Assessment of the Distribution of Radionuclides and Impact of Industrial Facilities in the Chornobyl Exclusion Zones

FINAL REPORT Assessment of the Distribution of Radionuclides and Impact of Industrial Facilities in the Chornobyl Exclusion Zones

under the GEF project “Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone”

Reporting period 01 November 2017 – 31 March 2018

Agreement SSFA/2017/19 S1-32GFL-000370/11232/SB-000687.37/14AC0003

Institute for Radiation Measurement and Development (IRMD)

Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

SUMMARY

This technical report includes information on the distribution of radionuclides that originated from the accident within the Chornobyl exclusion zone (ChEZ). The existing systems of routine and precision (scientific) radioecological monitoring were analyzed and approaches to their optimization are proposed. This report presents results of the latest field studies, which were carried out in the ChEZ during November 2017 - March 2018, and earlier historical data that follow the subjects of Tasks C and D. Comparison of the latest and historical data shall provide an opportunity to assess changing dynamics of the radiation situation parameters in the ecosystems of ChEZ. Distribution of radionuclides within the ChEZ was mostly preconditioned by the initial release of irradiated fuel from the emergency Chornobyl reactor (1986). The initial pattern of contamination has changed significantly during the works for the liquidation of the accident consequences. Also, the initial radiation contamination pattern of ChEZ ecosystems was and is still subject to changes due to various natural processes. As for possible redistribution of radioactive contamination within the ChEZ, special attention was paid to the sites containing radioactive materials and located within the ChEZ, such as RWTLS, RWDS, ChCP and some other man-made objects. Regular observations of radiation situation in the ChEZ (routine monitoring) shall allow identification and assessment of its trends and timely corrective measures for radiation protection of personnel, people and the environment, as appropriate. A prospective area of scientific monitoring in the ChEZ is related to studying the long-term radioecological and radiobiological effects, as well as provision of information for long-term forecasting of changes in exposure doses of humans and biota within and outside ChEZ based on verified mathematical models of radionuclide behaviour in the environment.

This report consists of 203 text pages including 33 tables, 97 pictures and photos, 2 appendixes, bibliography with 252 references.

Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

CONTENTS

1 GOALS, OBJECTIVES AND CRITERIA OF EFFECTIVENESS OF RADIOECOLOGICAL MONITORING IN THE CHEZ ...... 7 1.1 Description of monitoring objects ...... 8 1.1.1 Natural objects ...... 8 1.1.2 Industrial (man-made) facilities ...... 9 1.1.3 Population centers ...... 11 1.2 Routine monitoring ...... 11 1.2.1 Forests and meadows ...... 11 1.2.2 Surface waters ...... 12 1.2.3 Groundwater ...... 12 1.2.4 Population centers, where people live (the “self-settlers”) ...... 12 1.2.5 Man-made objects ...... 13 1.2.6 Air in the ChEZ ...... 14 1.3 Scientific monitoring ...... 17 1.3.1 Forests and meadows ...... 18 1.3.1 Research of radiobiological effects ...... 23 2 OPTIMIZATION OF RADIOECOLOGICAL MONITORING IN THE ChEZ 38 2.1 Retrospective of the network of research sites for scientific radioecological monitoring in the ChEZ ...... 38 2.2 Routine monitoring ...... 43 2.3 Scientific monitoring ...... 44 2.3.1 Development of criteria and requirements for the monitoring system of terrestrial ecosystems ...... 44 3 APPROBATION OF SCIENTIFIC MONITORING IN THE ChEZ ECOSYSTEMS ...... 49 3.1 Air ...... 49 3.2 Surface waters ...... 50 3.3 Groundwater ...... 51 3.4 Monitoring of meadow and meadow-shrub ecosystems ...... 51 3.5 Justification, selection, organization and equipment of experimental sites for terrestrial ecosystems ...... 54 3.5.1 Definition of requirements ...... 54 3.5.2 Experimental efforts on forest sites. Determination of inventories and fluxes of biologically mobile radionuclide in typical forest plantations ...... 58 3.5.3 Organization of experimental sites in forest test areas to further determine redistribution of biologically mobile radionuclides in typical forest stands ...... 75 4 MAN-MADE OBJECTS. INFRASTRUCTURE FACILITIES, INCLUDING THE CHCP AND RADIOACTIVE MATERIALS LOCALIZATION SITES ...... 77 4.1 Comprehensive statistical analysis of landscape diversity in industrially impacted areas .. 77 4.2 Approbation of radioecological monitoring in the ChEZ ecosystems subjected to severe anthropogenic impacts ...... 82 4.3 Monitoring of the RWTLS effects for surrounding ecosystems (by the example of a pilot site at trench No.22 in the “Red Forest”) ...... 83 4.3.1 Characterization of еру experimental site ...... 84 4.3.2 Radioactive contamination of soil cover ...... 85 4.3.3 Physicochemical characteristics of radioactive waste ...... 87 3

Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

4.3.4 Radioactive contamination of vegetation ...... 88 4.3.5 Radiobiological effects of chronic exposure ...... 89 4.3.6 Lateral migration of radionuclides with groundwater flow ...... 89 4.3.7 Impact of biogenic transport of radionuclides on their redistribution in topsoil ...... 95 4.3.8 Monitoring of 36Cl concentrations in the groundwater of RWTLS "Red Forest" ...... 96 4.3.9 Impact of fires on the mobility of radionuclide migration in soil cover ...... 97 4.3.10 Impact on surface air in case of fires ...... 104 4.4 Monitoring of ChNPP cooling pond ...... 105 4.5 Main directions of radioecological monitoring of the environmental impacts produced by man-made facilities ...... 120 5 MONITORING OF NATURAL ECOSYSTEMS ...... 122 5.1 Network of radioecological monitoring existing in the ChEZ ...... 122 5.2 Scientific monitoring of radiobiological effects in natural ecosystems...... 126 5.3 Radioecological monitoring of aquatic ecosystems ...... 130 5.4 Radioecological monitoring of agro-ecosystems ...... 132 6 DEVELOPMENT OF PREDICTIVE ESTIMATES OF RADIATION SITUATION IN THE EXCLUSION ZONE ...... 135 6.1 Monitoring of the environment contamination with 241Am ...... 136 6.2 Changes in the ChEZ soil contamination density ...... 139 6.3 Predicted transformation dynamics of the fallout’s fuel component on the ChNPP CP drained plots ...... 142 6.3.1 Transformation coefficients of the Chornobyl fuel component in the ChEZ water bodies 146 6.4 Expected effective exposure doses for population ( “self-settlers) in population centers within the ChEZ ...... 147 6.4.1 External exposure doses ...... 148 6.4.2 Internal exposure doses ...... 148 6.5 Predicted contamination of agricultural and forest products ...... 150 6.6 Predicted contamination of wood in the ChEZ ...... 152 6.7 Predicted air contamination in the ChEZ ...... 164 6.8 Predicted contamination of surface and ground waters in the ChEZ ...... 169 7 PROCESSING AND PRESENTATION OF THE OBTAINED RESULTS TO THE DATABASE FOR DECISION-MAKERS AND INFORMATION OF THE PUBLIC ...... 171 8 PROPOSALS ON THE REVISION OF EXISTING SYSTEM OF ROUTINE AND SCIENTIFIC MONITORING ...... 173 8.1 Routine minitoring ...... 173 8.1.1 Air ...... 173 8.1.2 Surface waters ...... 174 8.1.3 Groundwater ...... 174 8.1.4 Population centers ...... 174 8.1.5 Terrestrial ecosystems ...... 175 8.2 Scientific monitoring ...... 175 APPENDIX A…………………………………………………………………………………...... 193 APPENDIX B……………………………………………………………………………………..195

Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

LIST OF ABBREVIATIONS

ARMS Automated radiation monitoring system AU Aspiration unit AUA AS All-Union Academy of Agricultural Sciences named after V.I. Lenin ChCP ChNPP cooling pond ChEZ Chornobyl exclusion zone ChNPP Chornobyl NPP CPS Chornobyl pilot site CISF Central Spent Nuclear Fuel Storage Facility CWI Cooling water intake EDE Effective dose equivalent EDR Equivalent dose rate FC Fuel component IAEA International Atomic Energy Agency ICRP International Commission for Radiological Protection IHB Institute of Hydrobiology IRL International Radioecology Laboratory of the SSRI “Chornobyl Centre” ISF-1 Wet Spent Nuclear Fuel Storage Facility ISF-2 Dry Spent Nuclear Fuel Storage Facility ISRMEW Integrated system of radiation monitoring and early warning MS Monitoring station NASU National Academy of Sciences of Ukraine NHC National Hydrometeorology Committee NPP Nuclear power plant NRI Institute of Nuclear Research NSC New Safe Confinement NUBiP of Ukraine National University of Life and Environmental Sciences of Ukraine RAW Radioactive waste RSS Radiation Safety Shop RSSU Radiation Safety Standards of Ukraine RWDS Radioactive Waste Disposal Site RWTLS Radioactive Waste Temporary Localization Site SAEZ State Agency of Ukraine on Exclusion Zone Management SNRCU State Nuclear Regulatory Committee of Ukraine SO Shelter Object SSE State Specialized Enterprise SSE CRWME SSE “Central Radioactive Waste Management Enterprise”

Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

SRI Scientific and Research Institute SSRI “Chornobyl State Scientific and Research Institution “Chornobyl Centre for Nuclear Centre” Safety radioactive Waste and Radioecology” TUE Transuranium element URIAR Ukrainian Research Institute for Agricultural Radiology URIH Ukrainian Research Institute for Hydrometeorology WBC Whole-body counter WWER Pressurised water reactor ZU(O)R Zone of Unconditional (Obligatory) Resettlement

Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

1 GOALS, OBJECTIVES AND CRITERIA OF EFFECTIVENESS OF RADIOECOLOGICAL MONITORING IN THE CHEZ

Radiation situation in the contaminated areas is currently assessed based on routine radioecological monitoring of the following objects: • Ambient air; • Surface water and groundwater; • Terrestrial and aquatic ecosystems of soils and landscapes (bioindicator measurements); • Sources of air emissions (composition and amounts of emissions); • Sources of wastewater discharges (composition and amounts of discharges), • Radioactive waste disposal sites (composition and radiation situation).

The State Agency of Ukraine on the Exclusion Zone Management (SAEZ of Ukraine) ensures organizational supervision and coordination of measurement of the radiation parameters pursuant to the legislation of Ukraine [1].

The routine and scientific monitoring of terrestrial and aquatic ecosystems (forests, former agricultural lands and meadows, water bodies, atmosphere, population centres, infrastructure facilities, sites of radioactive materials localization) in the ChEZ are conducted by several organizations of various departmental subordination. This necessitates their coordination and coherence, including the purpose of optimization and unification of the obtained data.

Organization of the monitoring should ensure completeness of monitoring (coverage of all the basic observation objects in ecosystems and landscapes), relevance of monitoring (justified list of monitored parameters), representativeness of data on the fluxes of radionuclides in monitored objects, acceptability of resources required for the establishment and support the monitoring system. The above aspects should be balanced and taken into account during the monitoring system establishment and ensuring its operation; this is achieved through an optimal choice of the following: • monitored parameters (dose rate of gamma radiation, specific activity of radionuclides in the air, water, soil, flora and fauna, etc.); • density of monitoring sites or sampling locations (network); • frequency of monitored parameters measurement or sampling (procedure); • methods of sampling, samples measurement, statistical processing, transmission, storage and interpretation of data.

Based on the set goals and objectives, three functional types of monitoring are generally supported, including within the excluded areas [2]: • Routine (basic/standard); • Crisis (emergency) in case of emergencies, such as fires, floods, performance of works at radiation hazardous objects, etc.; • Scientific and special monitoring (precision) is carried out by scientific organizations and institutions of various departmental subordination in order to forecast changes in radioecological situation.

The main goal of routine monitoring is to provide information that is required to plan radiation protection of personnel and minimize migration of radionuclides outside the ChEZ with the objective to ensure radiation protection of population and the environment.

Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

The main goal of scientific radioecological monitoring is to provide information for the long-term prediction of changes in exposure doses of humans and biota in the ChEZ and outside it based on verified mathematical models of radionuclide environmental behaviour and on the knowledge of the effects of ionizing radiation for biota.

The efficiency of routine and scientific monitoring is ensured by observance of the following basic criteria: complete coverage of ecosystems and landscapes, relevancy of chosen monitoring parameters, representativeness of data on radionuclide fluxes in monitoring objects.

Radioecological monitoring is an integral element of radiation safety system.

Certain functional types of radioecological monitoring within the ChEZ are carried out by the following: • Routine monitoring is carried out by the State Specialized Enterprise (SSE) “Ecocenter” pursuant to the Procedure, which is usually approved for a certain period [3], subdivisions of the SSE ChNPP [4]and by licensees within the ChEZ; • Scientific and special (precision) monitoring are performed by scientific organizations and institutes of various departmental subordination: State Scientific and Research Institution "Chornobyl Centre for Nuclear Safety, Radioactive Waste and Radioecology" (SSRI "Chornobyl Centre"), Ukrainian Research Institute of Agricultural Radiology (URIAR) under the National University of Life and Environmental Sciences of Ukraine (NUBiP of Ukraine), Institutes of Hydrobiology, Zoology and Geological Sciences under the NAS of Ukraine, Ukrainian Research Institute of Hydrometeorology (URIH) and others.

1.1 Description of monitoring objects

The territory of ChEZ is administered by the SAEZ of Ukraine. The area of ChEZ is 259 799.8 ha (259 403.7 ha in the Kyiv region and 396.1 ha in the Zhytomyr region). The length of the ChEZ border perimeter is 441.2 km, where 154.5 km is a border with the Republic of Belarus. The total length of serviced roads is 536 km, there are 12 bridges in total and the total length of river network is 260 km, incl. 60 km of the Pripyat River [5].

Currently (2017), the levels of radionuclide contamination in the most contaminated areas within the ChEZ areas are follows: 137Cs - 100 MBq/m2; 90Sr - 50 MBq/m2; 239-240Pu - 1 MBq/m2.

The variety of natural and man-made landscapes in the ChEZ, their vast areas combined with high levels of contamination with a wide range of long-lived radionuclides make ChEZ a unique experimental site for radioecological and radiobiological researches, field training and education of specialists.

1.1.1 Natural objects The exclusion zone covers an area of approximately 2 600 km2; its natural terrestrial ecosystems include 60% of forest areas and 28% of fallow lands and meadows. Aquatic ecosystems of lakes and rivers cover 6% of its territory, and 3% are covered by swamps. Disturbed ecosystems of the ChEZ, including the town of Prypiat and other evacuated centres of population, radioactive waste storage facilities and cooling pond, cover 3% of the ChEZ area.

The territory of ChEZ includes 182 vascular plants species and 48 mosses, it is inhabited by 66 mammalian, 249 avian, 62 fish, 11 amphibian and 7 reptilian species.

Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

The vertebrate fauna within the exclusion zone is characterized by a considerable variety, which primarily results from the formation of an almost reserved conditions during all the years after the Chornobyl disaster [6, 7]. Additional research and searches in the literature allowed to develop a full list of animals that live in this area, or stay here during their regular flights, or have the zone in their range, or there are some literary references to the species finds in neighboring areas.

1.1.2 Industrial (man-made) facilities Located on the ChNPP industrial site • Units 1, 2 and 3 of the Chornobyl Nuclear Power Plant; • Shelter Object (SO) and the New Safe Confinement named “Arch”; • Cooling pond of the ChNPP (ChCP) with the set of hydraulic facilities; • Liquid Radioactive Waste Treatment Plant; • Industrial Complex for Solid Radioactive Waste Management; • Wet Spent Nuclear Fuel Storage Facility (ISF-1); • Dry Spent Nuclear Fuel Storage Facility (ISF-2).

Located outside the ChNPP industrial site • Vector Complex (Priority Stage 1 and 2); • Radioactive Waste Disposal Sites (RWDS “Buriakivka”, RWDS “Pidlisnyi”, RWDS “ChNPP Priority Stage 3”); • Radioactive Waste Temporary Localization Sites (RWTLS); • Facilities to be constructed: • Centralized Spent Fuel Storage Facility (Centralized ISF).

ChNPP cooling pond (ChCP). Operation of the cooling water intake (CWI) was stopped in 2014. During 2015-2017, the cooling pond water level went approximately 4-5 m down due to infiltration through the dam in the Pripyat River and evaporation. As a result of the water level drawdown to its natural background level, at least 13-18 km2 of high-level radioactive bottom deposits are expected to be exposed over the next 3-5 years. This process shall cause changes in the radioecological situation, both in the cooling pond and in the adjacent area due to the changed groundwater level, re-suspension of radionuclides, etc. A considerable extension of the program for the ChCP radiological monitoring shall be required.

RWTLS. Nine radioactive waste temporary localization sites (RWTLS) are located in the ChEZ territory: “Yaniv Station” (1280 thsd m2), “Naftobaza” (420 thsd m2), “Pishchane (Sandy) Plato” (880 thsd m2), “Red Forest”, “Stara Budbaza” (1220 thsd m2), “Nova Budbaza” (1250 thsd m2), “Prypiat” (700 thsd m2), “Kopachi” (1250 thsd m2), “Chystohalivka” (60 thsd m2); their total area is about 10 hectares. The RWTLS consist of earth trenches and pits with radioactive materials and are the sources of radionuclide migrations into the groundwater and vegetation.

Surveys, operation and monitoring of the RWTLS are carried out by the State Specialized Enterprise "Central Radioactive Waste Management Enterprise" (SSE "CRWME") under the licenses issued by the SNRC of Ukraine. The following parameters are subject to the assessment: geological and hydrological conditions of burials, level of groundwater radioactive contamination and others required for the burials inventory and listing them on the register and cadastre of RAW storage facilities.

The results of surveys and monitoring are used to design and plan engineering measures in order to prevent radionuclide migrations into the environment, plan and justify measures aimed at the re- disposal of radioactive materials from the RWTLS. 9

Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

The Shelter Object. According to various estimates, the Shelter facility contains 180 tons of nuclear fuel with radioactive materials, which activity exceeds 20 million Ci. In addition to fuel- containing masses (FCM), there are large amounts of RAW that include remains of the destroyed reactor core, reactor graphite, contaminated metal and engineering structures from the power unit in the Shelter.

RAW storage and disposal facilities. Considerable amounts of solid and liquid radioactive wastes with varying levels of activity were accumulated at the Chornobyl NPP over the years of its operation and during the accident consequences liquidation. To localize these radioactive wastes, within the framework of international projects for technical assistance Liquid RAW Treatment Plant and Industrial Complex for Solid RAW Management were built and are being currently put into operation at the SSE Chornobyl NPP site. Implementation of these facilities will ensure processing and conditioning of RAW.

Spent nuclear fuel (SNF) is currently stored in the SNF storage facility of "wet" type (ISF-1); it was put into operation in 1986 and its operating life shall expire late in 2025. Therefore, a new storage facility of “dry” type (ISF-2) is being constructed on the ChNPP site to ensure long-term safe storage of the entire bulk of SNF. After ISF-2 commissioning, which is scheduled for the last quarter this year, a process of nuclear fuel transportation from ISF-1 to ISF-2 will start there.

The Vector Complex site is located in the exclusion zone, 11 km to the south-west from Chornobyl NPP. The Vector Complex is a production facility for RAW decontamination, transportation, processing and disposal. Its construction was started in 1998 and includes the following two stages: • Priority stage 1 of the Vector Complex; • Priority stage 2 of the Vector complex.

The Vector Complex priority stage 1 was designed for the disposal of RAW that resulted from the Chornobyl accident. Start-up system priority stage 1 includes a facility for RAW disposal in reinforced concrete containers (TRO-1) and a modular storage facility for in-bulk RAW disposal (TRO-2). The Vector Complex priority stage 2 envisages construction of the following: • Centralized near-surface storage facilities for RAW disposal from the state-owned special enterprises for RAW management under SC "UkrGO Radon"; • Processing facilities for the RAW of Chornobyl origin and for the RAW from SC "UkrGO Radon" facilities; • Long-term storage facilities for high-level long-lived RAW; • Centralized storage facility for long-term storage of spent ionizing radiation sources (IRS).

In 2015, construction of a centralized facility for long-term storage of spent IRS and installation of the storage facility’s systems and equipment were completed on the Vector Complex site.

Construction of a centralized storage facility for spent nuclear fuel from the national WWER reactors was started in ChEZ (2017). Also, construction of a deep geological repository is planned in ChEZ, because the radioactive wastes in Ukraine mainly include the wastes of Chornobyl origin.

Industrial facilities (Fig. 1.1) are located in the central part of ChEZ, on a relatively small area (approximately 20–25 thousand ha) and thus produce no significant anthropogenic effect in terms of the entire ChEZ area. .

Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

Fig. 1.1 – Layout of industrial facilities within ChEZ 1.1.3 Population centers In 1986, people were evacuated from 76 population centres located in the ChEZ area, including Pripyat and Chornobyl cities, military station named Chornobyl-2. Also, residents were partially resettled from the 86 population centres, classified in 1991 as the ZU(O)R. The so-called self- settlers (less than 100 people) live now in some of population centres within the ChEZ. the SSE “Ecocenter” carries out routine radioecological monitoring in these settlements, including radioactive contamination measurements of in local foods,.

Basing on the available information, the comprehensive analysis of the current system of routine and scientific monitoring was performed in terms of its completeness (coverage of ecosystems, landscapes), relevance (set of parameters) and representativeness of data on radionuclide concentrations and fluxes in the monitored objects.

1.2 Routine monitoring

1.2.1 Forests and meadows The SSE “Ecocenter” carries out routine radioecological monitoring of forest and meadow ecosystem components on 15 landscape sites within the ChEZ in accordance with the effective Procedure [3]. The scope of annual monitoring includes measurement of contamination density and vertical distribution of radionuclides in soil, as well as radionuclide concentrations in vegetation. Concentrations of 90Sr, 137Cs and 238-240Pu are measured in the collected samples.

The routine monitoring, which is carried out by SSE "Ecocenter", is indirectly related to radiation protection of personnel and also addresses some tasks of scientific monitoring. Hence, the network (coverage of ecosystems, landscapes) and monitoring procedure for forests and meadows are subject to optimization. Radiological situation in the ChEZ changes extremely slowly now, and thus allows an increase of time intervals between the measurements. Also, the observation procedure is undergoing optimization basing on radionuclide migration models in the environment.

Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

1.2.2 Surface waters Routine monitoring of the ChEZ water bodies is carried out within the established network and according to the approved monitoring methods at the hydro-geological stations, drainage and collecting systems, on sites and in wells pursuant to the approved Procedure [3].

The existing network for observing radiation situation in surface waters was generally formed by the early 1990s. Radiation monitoring procedure of the surface waters is based on the URIH developments and on the recommendations of the Ukrainian Ministry of Chornobyl Affairs (1992). Currently, these works are mainly related to water sampling at 40 points and further measurement of 137Cs, 90Sr concentrations and of some other radionuclides on a non-regular basis. Some of the monitoring results are presented on the website of the SAEZ of Ukraine.

Only some observation points allow monitoring of radionuclide migrations by water outside the ChEZ. These are the points that provide the data necessary to plan radiation protection of public.

Another observation points are mainly focused on addressing the tasks of scientific monitoring. When planning their research, organizations should agree on the applied methods and procedures in order to ensure comparability of the obtained results and avoid duplication. To this end, a survey of target scientific organizations is in progress now.

1.2.3 Groundwater In 1987-1988, Priority Stage 1 of a special network of boreholes was commissioned and systematic observations of groundwater started (the design was developed by "UkrDniproVodHosp” Institute). Currently, the groundwater observation network within the ChEZ includes 138 observation points. The large number of observation points is caused by the complex spatial structure of the monitored objects.

Only some of these 138 observation points, including those located at the RWTLS and RWDS, provide data on radionuclide migrations by water outside the ChEZ, which can be used for planning public radiation protection activities. The remaining observation points support addressing of the scientific monitoring tasks and should be consistently used by relevant leading scientific organizations.

1.2.4 Population centers, where people live (the “self-settlers”) Since 1995, the SSE "Ecocenter" is ensuring annual monitoring of abandoned population centres within the ChEZ, where self-settlers have returned to. This monitoring includes radiometric surveys of gardens, sampling of soil in vegetable gardens, sampling of drinking water and sampling of locally produced foods. Concentrations of gamma-emitting radionuclides and strontium 90Sr are measured in the samples. In addition, radioactive contamination density is monitored annually at 12 stationary sites in the towns of Chornobyl and Pripyat.

In accordance with Procedure-96 [8], routine monitoring should be performed annually, in different seasons to assess the effective doses of people exposure. Moreover, it is important to itemize the diet of local residents and expand the list of monitored foods according to their diet. Special attention should be paid to measurements of strontium 90Sr, caesium 137Cs. Expected doses of the self-settlers’ exposure should be verified based on dosimetric monitoring of their external (WBC) and internal (concentration of 90Sr in urine) exposure doses.

Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

1.2.5 Man-made objects Monitoring of the infrastructure facilities within ChEZ is ensured under the integrated system of radiation monitoring and early warning (ISRMEW). The ISRMEW has a network of automated monitoring points that ensure continuous monitoring of the environment and transmit the data received via a radio channel (350,000 measurements per year). Total coverage area of the ISRMEW network is over 2,000 km2. It has 40 points within the automated radiation monitoring system (ARMS) including the following: 12 points on the ChNPP industrial site, 5 points in 5-km zone, 12 points in 10-km zone, and 10 points in 30-km zone. Some of the monitoring results are presented on the website of the SAEZ of Ukraine.

Measurements of dose rate in the areas with high contamination density of 137Cs and of the resulting gamma background cannot provide objective data on the changes in radiation situation (such as, increased volumetric activity of radionuclides in the air during fires). Contribution of radionuclide contamination in the adjacent territory to the measured dose rate can be reduced by adjusting detectors to passive protection against lateral radiation.

Radiation monitoring of soil contamination, intensity of radioactive fallout and radionuclide concentrations in the ambient air in the RWDS area is carried out by the SSE “Ecocenter” in accordance with the Procedure [3]. The radioactive waste localization sites (RWTLS, RWDS) fall within the scope of the ISRMEW. Generally, this network includes the following: aspiration units, 3 plates for atmospheric fallout, 10 control points for soil sampling, 5-10 wells for groundwater sampling, 3 reservoirs for wastewater sampling. Every month, concentrations of 90Sr и 137Cs in the groundwater of the existing wells network is monitored within the RWTLS locations.

Radiation situation in the mothballed trenches at RWDS "Buriakivka" is controlled every day, and the modules of RWDS “Pidlisnyi” are checked once a week.

Taking into account high total activity of radionuclides at the RWTLS and RWDS (approximately equalling to radionuclide concentrations in the ChEZ soil), a preliminary conclusion about relevance of the routine monitoring system can be made.

Routine radiological monitoring of radionuclide activity concentrations in the surface air and intensity of their fallout during the decommissioning of the ChNPP cooling pond is carried out by the RSS of SSE ChNPP in accordance with the Instructions (Table 1.1) [4]. The obtained results for radionuclide concentrations in the air (Figure 1.2) should be refined, since they cannot be identical in different seasons (in winter and in summer), as well as at different areal points, which contamination densities vary greatly. Moreover, measuring results provided by the RSS of SSE ChNPP do not coincide with the data of SSE "Ecocenter" (Figure 1.3)

Based on radionuclide concentrations in the air and radionuclide deposition rates presented in the data of SSE ChNPP RSS, dry deposition rate of 137Cs aerosols is 5-20 cm/sec, which exceeds the typical values of approximately 1 cm/sec.

Table 1.1 – Monitoring stations (MS) of the SSE "Ecocenter" and SSE ChNPP RSS located around ChCP Location of MS with regard to ChNPP Unit 4 Monitoring station Distance, km Angle, degrees (0 and 360 - North, 90- East, 180- South, 270- West) SSE ChNPP RSS GTS Base 1.7 75 CWI-3 2.6 85 13

Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

MS-146 11.1 139 MS-216 4.2 132 Territory of AK TsPA “Ostrov” 1.7 103 Territory of AK OMTS “Ostrov” 2.9 118 SSE "Ecocenter" VRP-750 1 180 Naftobaza 2 330 CWI-3 2.6 85 Chornobyl 16 147

1.2.6 Air in the ChEZ The following two parameters are measured during the routine monitoring of air in the ChEZ: radionuclide concentrations in surface air and radionuclide concentrations in atmospheric fallout. The existing system of air monitoring includes 14 stationary aspiration units (AU) within the ARMS and 25 plates.

Five AUs ensure sampling of aerosols in the “near zone” around ChNPP with continuous air pumping through filters. The filters are replaced 5 times per month; air is pumped through each filter for 5-7 days. In the ChNPP “far zone” (5-30 km), radiation monitoring is continuously ensured by 9 stations of ARMS network, which are located around the ChNPP, more densely in the south. Some monitoring results are presented on the website of the SAEZ of Ukraine.

Monitoring of radioactive atmospheric fallout in the “near zone” is ensured by 8 plates installed according to main directions of air masses movement. There are 8 tablets in the “far zone”, which is covered by the ARMS network. Some additional plates with filters made of Petryanov's material are installed around RAW localization sites. The plates’ exposure time before the material is replaced is 12-15 days under standard conditions.

The automatic stations, which are currently used for sampling of radioactive aerosols, have different pumping rates depending on air humidity during day and night, on pumping time and dustiness due to different resistance while airflow passes through the filters. These cause additional inaccuracies while determining surface concentrations of radionuclides. Various materials (paper, gauze fabric, Petryanov's material, etc.) were used for the sampling of radioactive fallouts on the plates and also impacted retention effectiveness of radioactive aerosols.

Therefore, it should be noted that the system for routine monitoring of radioactive aerosol concentrations in the surface air and their deposition intensity in the ChEZ should receive relevant scientific guidance, modern equipment, training of personnel and conduction of inter-departmental and international comparisons and calibrations.

The system for routine monitoring of radionuclide concentrations in the air is quite relevant as for the purposes of radiation protection of personnel in the ChEZ in case of emergencies (forest fires, dust storms at drained areas of the cooling pond, emergencies at the facilities, etc.); it should be optimized and certified modern equipment should be used. As for the purposes of radiation protection of public, routine monitoring should be performed in the ChEZ periphery, in the direction of most important population centres, and its frequency should commensurate with the dispersion from various potential sources of emission.

Routine monitoring of the effects of ionizing radiation for the ChEZ biota to assess the necessity of environmental radiation protection is not performed now. Routine monitoring of the behaviour of

Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone ultra-long-lived and mobile radionuclides, such as 3H, 14C, 36Cl, 99Tc, 129I, is not performed in the ChEZ.

Some results of routine radiological monitoring, which is carried out in the ChEZ by the SSE "Ecocenter", are presented on the website of the SAEZ of Ukraine and are stored as Microsoft Excel files.

Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

Fig. 1.2 – Radionuclide concentrations in surface air along the shore line (a) and (b) and above the drained plots (c) and (d) in 2017 [9, 10]

b Fig. 1.3 - Radionuclide concentrations in the surface air in 2016-2017, as per the results of the RSS of SSE ChNPP and SSE "Ecocenter" in the locations of CWI (a) and PK-146/Chornobyl (b) [7, 8, 11]

Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

1.3 Scientific monitoring

The number of articles focused on the ChEZ monitoring and published in the international science metric database SCOPUS has been monotonously decreasing since 1996. Over 2/3 of the publications deal with radionuclides behaviour in the environment and a significantly smaller part of articles is focused on radiobiological effects of ionizing radiation. The main focus is on the aquatic ecosystems, although they are not critical in terms of their impact on humans and the environment. More than half of the articles were focused on the behaviour of caesium 137Cs. The increased attention to 137Cs behaviour is due to a simpler measurement of its activity if compared to other radionuclides; however, the current exposure dose in biota is mostly formed by strontium 90Sr. Scientific monitoring in the ChEZ is carried out by the SSE “Ecocenter”, SSE “CRWME”, International Radioecology Laboratory (IRL) of the SSRI “Chornobyl Centre”, NUBiP of Ukraine, Institutes of Hydrobiology, Geological Sciences, and Zoology under the NAS of Ukraine, URIH, and other organizations of different departmental subordination.

The URIAR has a network of monitoring sites covering main soil types in the former agricultural lands and meadows. Since 1987, migration of strontium 90Sr, caesium 137Cs and plutonium 238-240Pu in soil profiles and in soil/vegetation cover components has been studied on these sites.

Scientific radioecological monitoring of the ChEZ forests is carried out on a few temporary experimental sites, which are organized mainly in the pine stands; sampling is conducted there in accordance with assigned tasks. In the last decade, the SSE "CRWME" and URIAR organized four new experimental sites for radioecological monitoring in the ChEZ.

There are some stations of the URIAR, IRL and other organizations in the ChEZ that are used to observe the effects of different levels of ionizing radiation for biota. Due to financial difficulties, a full-scale scientific monitoring of radiobiological effects manifestation in the ChEZ was carried out mostly within the framework of episodic international projects and is not systemic, thus making the verification of reliability of some data obtained in the ChEZ rather complicated. Scientific monitoring of the ChEZ water bodies is carried out in the following principal areas: studies of radionuclide distributions in water bodies; assessment of exposure doses for biota; studies of hydro-geological conditions in the exclusion zone; studies of filtration and sorption properties of dams and soils in aquifers, forms of radionuclide migrations with groundwater; assessment of long- term trends in the groundwater contamination in the areas impacted by the RWDS and RWTLS.

The key research objects of SSE “Ecocenter”, URIH, IHB of the NAS of Ukraine, NRI of the NAS of Ukraine, and URIAR include cooling pond of the ChNPP, Hlyboke Lake, Azbuchin Lake, Yanivskyi Backwater, areas of RWDS and RWTLS.

Regular researches (URIAR, IGS of the NAS of Ukraine, IRSN (France), NMBU (Norway)) of radionuclides migration in the unsaturated zone and groundwater, biogeochemical streams of radionuclides, contamination of vegetation, and effects of ionizing radiation for biota is carried out on the RWTLS named "Red Forest" (trench No.22) - Chornobyl Pilot Site (CPS).

Scientific radiological monitoring of population centres in the ChEZ is currently not performed.

Main directions of scientific monitoring of radioactive aerosols in the ChEZ include measurements of radionuclide concentrations and dispersed composition during fires and operation of power facilities in the ChEZ, re-suspension above the drained plots of the ChNPP cooling pond and during the performance of various process operations at ChEZ facilities.

Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

Scientific monitoring of the behaviour of ultra-long-lived and mobile radionuclides, such as tritium 3H, carbon 14C, chlorine 36Cl, technetium 99Tc, iodine 129I, is currently not conducted in the ChEZ.

There was practically no scientific monitoring towards the development of dynamic models of environmental objects contamination in case of radiation and nuclear accidents.

The Ukrainian organizations, which are involved into the system of scientific radioecological monitoring in the ChEZ, have accumulated large arrays of empirical data. However, the information is being collected and stored discretely, in different formats and on various media. Access to the data is usually restricted. There emerged a need to use modern data storage and transfer systems. It is advisable to establish a new common data bank for the results of radiological monitoring in the ChEZ under the umbrella of Ukrainian SAEZ and on the basis of SSE "Ecocenter". This shall allow organizing huge amounts of data and developing criteria for their collection, storage and access. The main data bank criteria should include free access to information in accordance with the Constitution of Ukraine (Article 50), reliability of data, and safety of data.

The works towards optimization and revision of the existing system of routine and scientific monitoring are currently in progress; the standpoints are: completeness (coverage of ecosystems, landscapes), relevance (set of monitored parameters) and representativeness of data on radionuclide concentrations and fluxes in the monitored objects.

1.3.1 Forests and meadows Radioecological studies of terrestrial landscapes in the ChEZ can be conditionally divided into the investigations of forest and of meadow (including wetland) ecosystems. A particular attention was paid to forest plantations, which share in the land structure of the 30-km exclusion zone was 45-60%, according to the data obtained in different years. Table 1.2 summarizes major publications on the studies of terrestrial ecosystems, which were carried out externally with regard to URIAR, are of great scientific importance in disclosing the aspects of the ecosystems’ radiation contamination resulting from the accident at Chornobyl NPP Unit 4, and are based on collected experimental data. It should be noted that most of research in the late 1980s - early 1990s were carried out through cooperation of scientists from the post-Soviet states, which were most affected by the Chornobyl releases. Unfortunately, we cannot present all empirical findings from the studies of the terrestrial ecosystems radioecology, since many studies have a lack of proper methodological or descriptive support, which could significantly affect reliability of their data or results. Also, a large amount of experimental data was lost due to an absence of appropriate system for their storage and distribution. We selected only those scientific publications, which include complete descriptions of collected materials and methodological approaches. Most of the authors and performers of the studies presented in Table 1.2 have published many scientific papers, where various aspects of certain problems are discussed basing on duplicated empirical data from the field and laboratories; therefore we presented papers with the largest experimental capacity from the scientists.

The analysis of experimental studies performed by different scientists indicates that the most significant contribution to the investigation of radionuclides behavior in the terrestrial ecosystems and of ionizing radiation effects in the phytocenosis was made in 1986-1997, then a gradual decrease of works in these areas is observed (Table 1.2).

Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

Table 1.2 – Major experimental studies of forest and meadow ecosystems within the ChEZ

Authors and operators Location and quantity of Goal and object of research Publication

of research Years testing sites, testing areas, etc.

Kozubov H.M., 1986 Radiobiological and 16 test sites were organized in the Kozubov H.M., Taskaiev A.I. Radiobiological and Taskaiev A.I. - radioecological study of east of the Chornobyl exclusion radioecological studies of woody plants. - SPb: Nauka, 1994. 1993 morphological and anatomical zone, plus one was outside the – 256 p. [12]. characteristics and growth zone, near Orane village in the processes in woody plants of Ivankivskyi district. coniferous stands. Scheglov A.I., 1986 Regularities of redistribution and 18 stationary test sites were Scheglov A.I. Biogeochemistry of human induced Tsvetnova O.B., - migration of human induced organized throughout the radionuclides in forest ecosystems: based on the data from a Kliashtorin A.L., 1997 radionuclides in forest ecosystem Chornobyl zone. 10-year research in the area impacted by the Chernobyl Mamikhin S.V., components. Biogenic fluxes of accident. - M.: Nauka, 2000. - 268 p. [13]. Moisieiev I.T., radioisotopes in forest types of Ahapkin G.I., landscapes. Rozov S.Yu., Merkulova L.N., and others Mamikhin S.V., 1987 Dynamics of 137Cs concentration 4 test sites were organized near Mamikhin S.V., Tikhomirov F.A., Shcheglov A.I. Dynamics Tikhomirov F.A., - in forest ecosystems components Dytiatky checkpoint and 2 test of 137Cs in the forests of the 30-km zone around the Chornobyl Scheglov A.I. 1994 under different soil conditions. sites were near Chystohalivka nuclear power plant / The Science of the Total Environment. village. 1997. – Vol. 193. – (1997) – p. 169-177 [14]. Kopeikin V.A. 1987 Concentration of medium- and Sampling points (9 pcs.) were in the Kopeikin V.A. Plutonium in the wood of living trees in the near - long-lived radionuclides in “near” zone of Chornobyl NPP zone around the Chernobyl NPP. -2005. - p. 157-162. – Access 1993 vegetative and generative organs fallouts (up to 5 km) on the right at: http://www.iaea.org/ inis / collection / NCLCollectionStore / of woody and shrubby plant bank of the Pripyat River. _Public / 28/017 / 28017501.pdf [15]. species.

Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

Table 1.2 (Continued)

Authors and Location and quantity of Goal and object of research Publication

operators of research Years testing sites, testing areas, etc.

Scheglov A.I., 1987- Long-term dynamics of 137Cs and 8 test sites were organized within Shcheglov A., Tsvetnova O., Kliashtorin A. Biogeochemical Tsvetnova O.B., 2007 90Sr migration processes and their the Chornobyl zone: near cycles of Chernobyl-born radionuclides in the contaminated Kliashtorin А.L. biogeochemical cycle in Dytiatky checkpoint - 3 sites, forest ecosystems. Long-term dynamics of the migration contaminated forest ecosystems. Kopachi village - 3 sites, processes / Journal of Geochemical Exploration. – 2014. – Chystohalivka - 2 sites. Vol. 144. – p. 260–266 [16]. Hrodzynska H., 2002- Concentrations of 90Sr and 137Cs Fungi were sampled in 3 locations Hrodzynska H., Syrchyn S., Kuchma M., Konishchuk V. Syrchyn S., 2007 in organs of macromycetes. within the ChEZ: RWTLS "Red Macromycetes are bio-indicators of radiocaesium Kuchma M., Forest", Yaniv village, Kopachi contamination of forest ecosystems in Ukraine / Bulletin of Konishchuk V. village and Staro-Shepelychi NAS of Ukraine. - 2008. - No. 9. - p. 26-37 [17]. forestry. Shaw G., 1992- Parametrization of model of Forest area near Kopachi village. Shaw G.; Kliashtorin A., Mamikhin S., Shcheglov A., Kliashtorin A., 1995 radiocaesium fluxes in forest Rafferty B., Dvornik A., Zhuchenko T., Kuchma N. Mamikhin S., ecosystems. Modelling radiocesium fluxes in forest ecosystems / First Shcheglov A., international conference 'The radiological consequences of the Rafferty B., et al. Chernobyl accident'. – 1996. – p. 221–224 [18]. Kuchma N.D., 1986- Forecasting of radionuclide Forest management and partially Kuchma N.D., Arkhipov I.M., Fedotov I.S., Tikhomirov F.A., Arkhipov I.M., 1994 contamination dynamics in major sanitary values were determined Shcheglov A.I., Krynytskyi H.T., Kozubov H.M., Zibtsev Fedotov I.S., components of forest for the entire ChEZ. Basic S.V., Matukhno Yu.D., Popkov M.Yu., Radnemko O.N., Tikhomirov F.A., biogeocenosis was carried out. provisions were analyzed based Borovykova N.M., Diukarev A.P., Balatev L.S. Shcheglov A.I., Radiobiological effects of on the three test sites: near Radioecological and silvicultural consequences of the Krynytskyi H.T., ionizing radiation in woody plants Dytiatky and Leliv checkpoints contamination of forest ecosystems in the exclusion zone. Kozubov H.M., were described. and near Novi Shepelychi village. Chornobyl: Ministry of Chornobyl of Ukraine, 1994. - 53 p. Zibtsev S.V., (Preprint of the Research and Production Association Matukhno Yu.D., "Pripyat" Scientific and Technical Center) [19]. Popkov M.Yu., and others

Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

Table 1.2 (Continued)

Authors and Location and quantity of testing Goal and object of research Publication

operators of research Years sites, testing areas, etc.

Arkhipov N. P., 1986- Acute and chronic effects of Rsearch was carried out on 4 sites Arkhipov N. P., Kuchma N. D., Askbrant S., Pasternak P. S., Kuchma N. D., 1991 ionizing irradiation in forest of Scots pine plantations in and Musica V. V. Acute and long-term effects of irradiation on Askbrant S., cultures of Scots pine at around the RWTLS “Red Forest”. pine (Pinus sylvestris) strands post-Chernobyl / Science of Pasternak P. S., different levels of The Total Environment. –1994. – Vol. 157. – p. 383-386 [20]. Musica V. V. contamination. Zibtsev S.V. before Characteristics of absolute and Test areas (8 pcs.) were organized Zibtsev S.V. Accumulation of 90Sr in phytomass of forest 2002 relative contamination of tree in various types of forest plantations / Scientific Journal of Ukrainian State Power species organs with 90Sr. conditions, which are most typical Forest Engineering University. - 2003. - Issue 13.3. - p. 83-88 of the region. [21]. Bonzom J.M., 2010- Destruction of forest leaf litter Samples of soil and forest leaf litter Bonzom J.M., Hättenschwiler S., Lecomte-Pradines C., Hättenschwiler S., 2011 in deciduous stands at different were taken from 11 test sites in the Chauvet E., Gaschak S., Beaugelin-Seiller K., Della-Vedova Lecomte-Pradines C., levels of radioactive birch and alder plantations located C., Dubourg N., Maksimenko A., Garnier-Laplace J., Adam- Chauvet E., contamination. in different parts of the ChEZ. Guillermin C.Effects of radionuclide contamination on leaf Hashchak S., litter decomposition in the Chernobyl exclusion zone / Science Beaugelin-Seiller K., of the Total Environment. – 2016. – Vol. 562. – p. 596-603 Della-Vedova C., [22]. Dubourg N. et al. Paskevych S.A. 1996- Assessment of radiation weight Stationary sampling sites covered Paskevych S.A. Radiation weight of phytocoenoses in 1999 of grassy phytocenoses in the major types of meadows and meadows and fallows of the Chornobyl exclusion zone in the ChEZ meadows and fallows in fallows within the ChEZ. 33 sites in late phase of the accident: author's abstract to the thes. for a the late accident phase, with total. Candidate Degree in biology sciences, spec 03.00.01 - due regard for the Radiobiology. Kyiv, 2006. 20 p. [155]. characteristics of local landscapes.

Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

Table 1.2 (Continued)

Authors and Location and quantity of testing Goal and object of research Publication

operators of research Years sites, testing areas, etc.

Prister B. S., 1986- Main regularities in the 19 sampling points for soil and Prister B. S., Belli M., Sanzharova N. I., Fesenko S. V., Belli M., 1995 behavior of radionuclides herbaceous plants were organized Bunzl K., Petriaev E. P., Sokolik G. A., Alexakhin R. M., Sanzharova N. I., from Chornobyl releases in within the Ukrainian ChEZ. Ivanov Yu. A., Perepelyatnikov G. P., Il'yn M. I. Behaviour of Fesenko S. V., meadow ecosystem radionuclides in meadows including countermeasures Bunzl K., components. Mathematical application / Proceedings of the first international conference Petriaev E. P., model of radionuclide 'The radiological consequences of the Chernobyl accident'. – Sokolik G. A., migrations in the meadow 1996. – Vol. 31. – p. 59–68 [23]. Alexakhin R. M., (grassy) ecosystem Ivanov Yu. A., components was developed. Perepelyatnikov G. P., Radioecological classification Il'yn M. I. of meadow ecosystems was proposed. Effectiveness of applying countermeasures to meadow ecosystems was assessed.

Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

Hence, even based on a brief retrospective overview of the studies that were previously performed in forest and meadow ecosystems of the ChEZ (Table 1.2), it is easy to calculate that only the abovementioned scientific publications demonstrate that the quantity of test sites, where scientific monitoring has been carried out since 1986, includes 84 sites in forest ecosystems and 52 sites in meadows. The experimental data collected during that period allowed solving of many scientific and economic problems, which were outstanding in the first decades after the accident at Chornobyl NPP. However, it can be stated that stationary sites for continuous long-term investigations of radionuclide circulation and radiobiological effects in terrestrial ecosystems were not properly equipped, and therefore they cannot be used for new modern researches (this will not allow obtaining comprehensive and systematic researches of the dynamic processes in radionuclide redistribution in future and is a great loss for scientific community). Also, there is a lack of open databases for tracking characteristics of the plant communities, radioecological and radiobiological parameters. Rarely, if ever, the test sites can be renewed.

The scope of test sites in ChEZ covered the most common variations of its terrestrial landscape types; however it cannot be regarded as sufficient to demonstrate the actual distribution of forest and radioecological conditions within the area, and this was caused by the fragmentary nature of studies performed by scientific teams, which had different objects and subjects of research. In fact, only the work of S.A. Paskevych (2006) may be considered as finalized in terms of completeness and representativeness of information used for assessing radioecological value of meadow ecosystems in the ChEZ.

1.3.1 Research of radiobiological effects Experience in liquidating severe radiation accidents, including the Chornobyl NPP accident, demonstrated that radiobiological effects for natural and agrarian ecological systems affected by radioactive contamination depend on radiosensitivity of their dominant species. The most radiosensitive ones include coniferous plants, mammals and coniferous forest ecosystems.

In principle, this regularity in the formation of biological effects under a large-scale radiation impact should determine the formation of comprehensive bio-ecological monitoring in the areas contaminated with radionuclides.

Specific aspects of ChEZ existence allow to state that over a long period of time ChEZ will be a basis for scientific research and a testing ground for the development of methodologies to forecast sustainable existence of ecosystems as impacted by a radiation factor. Monitoring of potentially hazardous effects of the radiation factor on large areas should take into account not only the factor’s impact itself, but also the effect of absence of humans and their activity in the area, possible adaptation of biological objects to new environmental conditions (with no humans), as well as compensation processes and possible adaptation to human-induced factor in time. Bio-ecological monitoring should also allow the possibility to test the effects of hazardous factor, as well as appearance of biological effects against the effects of this factor.

Therefore, bio-monitoring of a radioactively contaminated area should include organization of an experimental study of transformations of natural objects and biological systems under the effects of changing radiation conditions (unless there are no other pollutants or biogenic factors in an ecosystem).

1.3.1.1 Animals

Analysis of works carried out in the ChEZ after the Chornobyl accident shows that despite the presence of crucial physiological dysfunctions in various organisms taken as a whole, and in certain cases even significant dysfunctions, its populations still exist (and sometimes even thrive) even under 23

Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

the most extreme, in terms of radiation impact, conditions (Table 1.3). It is noteworthy that changes that are revealed by scientific teams from CIS countries (Ukraine, Belarus, Russia) are not confirmed by the results of long-term researches carried out by foreign scientific teams (R.K. Chesser and R.J. Baker). This is especially true for studying chromosome aberrations frequency, micronuclei in erythrocytes, and various biochemical parameters. Taking into account the level of equipment in foreign laboratories, for some reason we would like to place particular confidence in the American results, which are confirmed by the general state of animal populations.

Therefore, for the optimization of bio-ecological monitoring in ChEZ we should apparently implement and plan studies from the perspective of assessing ecosystems as a whole, shift the focus from individual elements to a more integrated approach to monitoring and characterization of environmental conditions. Summarized monitoring results for biological effects in some representatives of animal world on the test areas in ChEZ are presented below (Table 1.3).

The conclusions are as follows: • The variety of biological forms and their interrelations, of landscapes and specific features of radioactive contamination within the ChEZ requires performance of monitoring studies to ensure radiation protection of humans and the environment; • Numerous biological effects on organismic, suborganismic, cellular, cytogenetic, and molecular levels that are observed by various authors and author teams from different countries do not provide a clear-cut understanding of dose dependencies in radiobiological effects under the conditions of natural experiments, with the involvement of all ecosystem relationships; • Majority of scientific studies and experiments, excluding farm animals and Przewalski's horses, are natural within this zone, they enlarge database on in-field reactions of biological objects to radiation effects and should be continued.

Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

Table 1.3 – Results of bio-environmental monitoring for studying the effects of radioecological conditions in animal organisms in the ChEZ Year Object Sites Studied parameters Doses Obtained effects 1986 Drosophila Red Forest Mutation rate 200 mR/h Mutation levels were increased in 1986-1987, after 2 years they decreased and returned to standard ones [24] 1986 Representatives of 3-7 km from the Abundance 8-86 Gy Decreased by 30 times in natural areas and by 2 (July) soil mesofauna (acari, ChNPP Biodiversity times in agricultural lands. [25,26] worms at various (Chystohalivka: Recovery started in a year. Abundance renewed development stages) forest and field) in 2.5 years. Even after 10 years, the species diversity was 80% of the reference one. Amphibians 1986- Populations of brown 180-2330 kBq/m2 for Chromosome >2 Gy Verifiable increase in aberrations in the bone 1994 frogs 137Cs aberrations, marrow cells and in blood [27]. Coherence and micronucleus in between dose and cytogenetic disorders in the 3.7-280 kBq/m2 for erythrocytes, tumors bone marrow can be traced before 1990 [28]. 90Sr Number of micronuclei in erythrocytes was higher up to 1991 [29]. Reduction of exposure dose over time (1990-1994) did not result in a decrease of aberrant cells in the bone marrow. Number of aberrations increased 5-6 times per a dose unit. After the experimental and reference frogs have got an additional acute exposure (2 Gy dose), no significant difference in XA amount was discovered [30], but the number of cells with damaged chromatin and apoptosis rate increased [31]. Among the 2500 studied frogs, 7 had bone tissue tumors [32]. Hydrobionts 1986- Fish (Sander, Asp, Cooling pond Fluctuating asymmetry 10-17 Gy Concentration of 137Cs in the carnivorous fish 1995 Silver Carp) level of pectoral fin rays tissues was an order of magnitude higher than the (FALPF), disorders in one in phytophags [33]. reproduction, In 1986, FALPF of a young Sander was 30 times development, blood higher than the one of a reference one [34]. By system 1991, the dose in young Silver Carp was 9-11 Gy [35,36]; 5.6% of specimens were sterile, with 0.25% in the reference ones; 15% had partial sterility; gonad development asymmetry was in

Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

Year Object Sites Studied parameters Doses Obtained effects 11%, with 2.9% in the reference ones [35]. Fertility of Silver Carp females in the ChCP exceeded the reference one by 40%, concentration of 137Cs in caviar was 15 kBq/kg, abnormal development of caviar was in 11%, the values for abnormal sperm were higher [36]; offspring demonstrated higher abnormal development than parents [37] 1986- Mollusca Cooling pond Development of ? State of depression [33,34] 1987 populations 1986- Oligochaetes A water body near Chromosome 14 µGy/h Verifiable relationship between the number of 1990 Yaniv village aberrations, number of XA and the number of specimens changing to specimens in populations sexual development [38]. Mammals 1986- Populations of mouse- 30 km ChEZ Abundance Did not depend on contamination density [33] 1988 like rodents October Populations of mouse- Chystohalivka Embryonic mortality Amounted to 34%; the reference one was 6% 1986г like rodents (Bank [33] Vole) 1986 - Mice (Root Vole) 5 km south of the State of circulatory EDR 4-6 mR/h -1 Gy The general condition was satisfactory. 1987 ChNPP system external exposure dose Numerous changes in the characteristics of white and red blood (hypochromic anemia, leukopenia was up to 2-fold [39, 40] 1986 - Mice (Root Vole) 20 km south-west of State of circulatory EDR 0.8 mR/h – Satisfactory condition. Numerous changes in the 1987 the ChNPP system absorbed dose -0.02Gy characteristics of white and red blood, internal organs [39] 1988 - Mice (Root Vole) – 5 km south of the State of circulatory EDR 4-6 mR/h -1Gy Satisfactory condition. Leukopenia was at the 1992 offspring, on the same ChNPP system external exposure dose level of 60%, micronuclei in erythrocytes, spleen sites state corresponds to radiation sickness of moderate severity, liver damage [40, 41] 1987 - Mice (Root Vole, 5 km south of the State of circulatory EDR 0.02-200 mR/h Satisfactory condition. Destructive liver 1992 Common Vole - ChNPP system, histology of damages, lipid depletion in antioxidants [42], 1987) - offspring after internal organs, values of increased cortical zone of adrenal glands and 5 years, on the same antioxidant ant system decreased zona glomerulosa in 5 generations; sites presence of cells with nucleus pycnosis, diploid and polyploid cells, necrotic changes in thyroid

Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

Year Object Sites Studied parameters Doses Obtained effects gland and adrenal glands. [39] 1986 Mice - voles 4-5 km south of the Catecholamines and 7-12 mR/h (40 Ci/km2 Catecholamines are verifiably lower, and protein ChNPP protein kinases in adrenal for 137Cs) kinase is verifiably higher [43]. glands 1986- Mice – Bank Voles EZ of Belarus Chromosome aberrations Station1 – 8-1526 Frequency of aberrations increased with 1992 kBq/m2; increasing contamination density. 14 generations Station 2 – 220-1526 were traced. The frequency of aberrations was 3- kBq/m2 7 times higher than on reference sites. On the Doses were 0.7 sites with higher contamination, aberrations were mGy/day more common, with the predominance of chromosomal type (fragments, robertsonian translocations, inversions); frequency of polypolyploid cells in the bone marrow exceeded the accident level by 1-3 orders, increased frequency of micronuclei in the erythrocytes was traced up to the 22nd generation [44, 45, 46, 47]. 1986- Mice – Root Voles ChNPP EZ Chromosome aberrations 0.02-200 mR/h. Sterility of males on the most contaminated sites, 1991 and micronuclei in Absorbed dose was 3-4 no accumulation of mutations in time, higher XA erythrocytes Gy/month on contaminated sites, but no dependence of the effect on the dose rate was observed [48, 49, 50, 51]. 1986- Mice – Root Voles 10-km ChNPP EZ Chromosome aberrations 97 mGy/d No changes [52] 1991 and micronuclei in erythrocytes Voles 10-km ChNPP EZ, Chromosome aberrations 19-53 mGy/d – 3.5-10 No difference in the frequency of chromosome Red Forest, Hlyboke and micronuclei in Gy cumulative dose breaks between Chornobyl and reference Lake erythrocytes animals, no disorders in the development of populations. [53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66 ] 1986- Mice – Root Voles, ChNPP EZ Frequency of 0.03 -300 mR/h in 1986 The maximum occurrence of anomalous 1991 Bank Voles, Field micronuclei, disorders in spermium heads was observed in the first 2 years Mice sex somatic cells after the accident; in 1986-1989 the frequency of micronuclei was verifiably higher than in later years; in 5-6 years after the accident the frequency of genetic disorders in sex and somatic cells decreased to a spontaneous level [67,68]

Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

Year Object Sites Studied parameters Doses Obtained effects Population studies 1986- Faunal complexes of Red Forest 3 sites, Changes in species ? Drastic changes in the structure of insect- 2001 insects-herpetobionts Kopachi, composition, trophic herpetobiont system during the first 5 years after Chystohalivka, structure, abundance in the accident (disappearance of phytophags and Novoshepelychi representatives of certain dominance of Silphidae) followed by forestry trophic groups stabilization and recovery in the 8-9th years after the accident [69, 70, 71,72, 73, 74, 75, 76, 77,] 1986- Structure and Kopachi, Studying the abundance A sharp increase in the abundance due to the 1999 dynamics of micro- Nova Krasnytsia, dynamics, age and sex changed conditions of using nature; logical mammal populations Chystohalivka, structure decrease at a relatively high level. Dose Izumrudne dependence of population abundance; abundance impacted by the changes in human burden; changes in the species ratio depending on biocenosis succession; changes in female fertility [78, 79, 73, 74, 75, 84, 85, 80, 81] 1997- Abundance of hunting Entire ChEZ Abundance of hunting During the first five years after the accident, there 2001 and commercial animals, characteristics was a significant increase in the abundance of mammals of RN contamination of polycarpous species (Wild Boar); increase in the organs and tissues abundance of oligocarpous species (Elk, Roe Deer). Stabilization of abundance and a slight decrease starting with the 6th year after the accident. Appearance of rare and endangered species of mammals and birds starting with the 5th year after the accident [82, 83, 84, 85, 86, 87] (c) 1986- Biogenic migration of ChEZ; Assessment of RN carry- Rate of RN removal beyond the ChEZ was 1988 RN over by migratory birds estimated. Birds that stop in the ChEZ for feeding mostly contribute to the removal. Role of various migration paths was assessed.

Migration of RN in Typical features of RN migration within the 1986- Kopachi, Nova trophic chains pasture trophic chain were defined. The most 1998 Krasnytsia, intensive accumulation and redistribution are Chystohalivka, typical of saprobic portion in the chain [88, 89, Cherevach 90, 71, 91, 92. 93, 94 ] (d) 1988- Variability of animal Kopachi, Variability of Increased degree of variation of wing cover

Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

Year Object Sites Studied parameters Doses Obtained effects 2001 morphological Chystohalivka, morphological pattern in the Colorado potato beetle within the characteristics Cherevach, characteristics while ChEZ, increased variability of wing pattern in the Izumrudne living under the exposure yellow-winged darter, increased degree of conditions variation in skull bones structure of micro- mammals [95, 96. 97, 80, 98,] (e) 1987- RN behavior in Entire ChEZ Intake, redistribution of Determination of typical features of absorbed 2001 animal organism RN in wild animals of dose formation in wild animals, depending on the ChEZ. Formation of their ecological characteristics, i.e. specific radiation doses in various confinement, type of feeding, activity, etc. [99. animal species 70, 100, 101, 102, 103] (е) Farm animals 1987 Cows Evacuated from the Thyroid gland disease The dose ratio in thyroid Partial atrophy or complete destruction of thyroid ChEZ, Homel region gland, mucous coat of gland, death in 5-8 months after the accident with gastrointestinal (G.I.) myxedema symptoms; edema of thyroid gland tract and in the whole stroma, hemorrhage into follicle cavity were body was 230:1.2:1; observed in 2 weeks after the accident; The dose of thyroid necrobiotic changes in follicle epitheliums, gland was 60-200 Gy proliferation of connective tissue were 2 months later; decreased volume of thyroid gland, thyroid gland necrosis were after 5 months [104,105,106]. 1987- 3 cows and a bull Novoshepelychi Physiological state 2 Gy per an organism, The frequency of chromosomal abnormalities in 2000 parameters 10 Gy per a mucous coat peripheral blood cells did not exceed 5-7% of the of G.I. tract, 50-150 Gy typical frequency of chromosomal aberrations in per a thyroid gland cattle; dependence between frequency of MN detection in erythrocytes and age was observed: certain alleles were not equiprobably transmitted from parents to offspring; a sharp change in alleles frequency in the first generation and their stabilization in the second generation were identified; mutations in the structural gene were found (transferrin locus), the animals have retained their ability to reproduce productivity. 4 generations were traced. [107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118]

1.3.1.2 Plants

Below are the results analysis for the major studies of radiobiological effects in reference plant species in the ChEZ (Table 1.4). Basic parameters in the studies of Scots pine included cytogenetic and genetic changes, seed reproductivity, survival of seedlings; the dependence of cytogenetic and genetic effects on absorbed dose rate was demonstrated [119, 120, 121, 122]; the genesis of radiomorphoses observed in the pine sublethal damage zone was established [12]; epigenetic changes (hypermethylation of DNA) in exposed pines were identified, and they probably are among the mechanisms of the plants’ rapid adaptation, which controls expression of genes and stability of genome. Therewith, there is an assumption that the DNA hypermethylation is a sharp adaptive response to the impact of ionizing radiation, because a tendency towards a decrease of this value both in plants growing in laboratory conditions and in plants growing under the conditions of chronic ionizing radiation in the ChEZ was observed in subsequent generations of the plants exposed in 1987, Arabidopsis thaliana (L.) Heynh. (A. Thaliana) [123]. The science that studies these changes is relatively young; and the significance of impact of epigenetic changes on genome stability and on population stability in general is an object requiring further investigation.

Earlier studies, which rather refer to investigations of acute exposure effects since the observed effects depended on the dose absorbed in early phase of the accident, demonstrate some negative effects in herbaceous plants of the ChEZ, both at the organismic and ecosystem levels; i.e. reduced reproductivity of seeds, decreased biodiversity of phytocenoses, development of immune deficiency, increased mutation frequency resulting in the development of morphological abnormalities [124]. If compared to 1986, the level of radiation background in the ChEZ has currently decreased significantly, and it is now less than 1% of the initial values [Error! Bookmark not defined.,125]. Despite this, the young coniferous trees demonstrate a tendency towards formation of radiomorphoses and increased frequency of cytogenetic changes depending on their exposure dose [141]. However, according to the research results in general [126, 127, 128] and in disregard for the expected destructive effect of radiation exposure, an increased diversity of fauna and flora species, appearance of rare and red-book plants (over 40 new-for-this-territory vascular plant species were recorded within the ChEZ) and animals (18 red-book mammal species were found in the ChEZ), disappearance of adventitious and domestic animals were recorded for the ChEZ. These are primarily due to an absence of anthropogenic factor. Therefore, a high level of radioactive contamination in the ChEZ has not produced negative effects on the diversity of biota species. The authors [210] stress that none of plant or animal species were endangered due to the Chornobyl accident. Radiation exposure, which is traditionally considered as a negative environmental factor, produces a noticeably less effect on biota if compared to lack of anthropogenic factor [129]. Hence, any effects of chronic exposure in the ChEZ are difficult to detect nowadays (excluding the coniferous trees radiomorphoses), if not viewed, literally, under a microscope.

Together with cytogenetic changes and expression of stress-dependent genes, later studies do not disregard characteristics of functional activity of antioxidant defense system in plant cells. This is due to its function of detoxification of reactive oxygen intermediate (ROI), which form in response to the impact of stress factors, including ionizing radiation. It is known that intensive formation of ROI and ROI-caused oxidation processes become a mechanism of cell destruction under the impact of acute ionizing radiation [130]. On the other hand ROI, which form on a cell-controlled level, are signaling molecules participating in gene expression regulation [131, 132]. Studies [133] that were carried out in the Bryansk region (exclusion zone in the Russian Federation), which was contaminated with radionuclides due to the Chornobyl accident, have not revealed any changes in the activity of catalase and superoxide dismutase (key antioxidant enzymes) in Scots pine seedlings with the absorbed dose rate up to 14.8 μGy/h, as well as total plant peroxydase changes that are Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone inversely proportional to absorbed dose rate. The authors [133] concluded that antioxidant protection system of Scots pine is functionally adequate under the impact of low doses of ionizing radiation.

31 Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

Table 1.4 – The results of major studies of radiobiological effects in reference plant species on the sites of Ukrainian ChEZ and of some studies on the sites of exclusion zone in the Russian Federation (RF) and in the Republic of Belarus (RB) are shown in the table below. Year of Object of research Sites Studied parameters Doses Obtained effects Organization Reference research 1986–1988 Taraxacum officinale Chornobyl Single-strand breaks of Acute exposure Induction of single-strand Institute of General Syomov et (common dandelion) Leliv DNA with the absorbed breaks with increasing Genetics named al., 1992 Arabidopsis thaliana Tovstyi Lis DNA recovery efficiency dose rate (EDR) absorbed dose rate. after N.I. Vavilov, [134] (thale cress) Yaniv-1 between 70 and High reparation efficiency USSR Academy of Viccia cracca (tufted Yaniv-2 2500 µGy/h), 0.2 (≈100%), excluding the areas Sciences (Moscow) vetch) Reference site µGy/h – on with the EDR of 2500 μGy/h outside ChEZ reference sites (Tovstyi Lis) 1986–1988 Arabidopsis thaliana Tovstyi Lis Frequency of embryonic 2–18480 sGy Increase in embryonic lethal Institute of General Abramov et (thale cress) Leliv lethal mutations, mutations with increasing Genetics named al., 1992 Zapolie polymorphism of some absorbed dose. No after N.I. Vavilov, [135] Chornobyl genes relationship between the AS of the USSR Yaniv-1 polymorphism of studied (Moscow) Yaniv-2 genes and absorbed dose. Reference sites outside ChEZ 1987–1992 Arabidopsis thaliana Tovstyi Lis Sensitivity to mutagens between 0.2 Gy Increased resistance to Institute of General Kovalchuk (thale cress) Yaniv Stability of genome and 248 Gy mutagen impacts Genetics named et al., 2004 Chornobyl (frequency of Reduced frequency of after N.I. Vavilov, [123] Reference site homologous re- homologous recommendations AS of the USSR outside ChEZ combinations) Multidirectional changes in (Moscow) Expression of stress- the expression of stress- dependent genes dependent genes Global changes in DNA Increased percentage of DNA methylation hypermethylation followed by leveling of the effect in later years of observations 1987–1989 Secale cereale (rye) Kozhushki Morphological values of 1.3–12 Gy Dose-dependent increase in All-Russian Geraskin et Triticum aestivum Chystohalivka seed viability, cytogenetic 2–78 sGy for root cytogenetic damages Institute of al., 2003a (common wheat) Red Forest changes in root meristem meristems Agricultural [120] Hordeum vulgare RS sites in the Radiology and (barley) ChEZ Agricultural Avena sativa Ecology (Obninsk)

32 Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

Year of Object of research Sites Studied parameters Doses Obtained effects Organization Reference research (common oat) 1986–1992 Pinus sylvestris L. 16 test sites within Morphogenesis and 4–25 Gy Genesis of radiomorphosis Institute of Biology Kozubov, (Scots pine) the 30 km ChEZ growth processes, Critical absorbed doses for of Komi Ural Taskaiev, Pices abies (L.) and 1 site outside morphological and pines and spruces (lethal doses branch of the RAS 1994 [12]; Karst. (Norway ChEZ (reference anatomical characteristics for young pine trees were Kozubov, spruce) one) of tree leaf apparatus in within the limits of 3-12 Gy, Taskaiev, the zones with sub-lethal for mature trees - 30-120 Gy, 2007 [136]; and average exposure for young spruce trees - 1-5 doses Gy, for mature trees - 5-15 Gy) 1986–2001 Pinus sylvestris L. Reference (Moscow Cytogenetic abnormalities Increased frequency of Institute of General Igonina, (Scots pine) region) (chromosome aberration In 2004 cytogenetic disorders with Genetics named 2010 [119] Dytiatky frequency), frequency of 0.18 µGy/h increasing exposure dose rate. after N.I. Vavilov, Zapolie isoenzymatic loci 0.09 µGy/h Wave-like change in the RAS Leliv mutations, survival of frequency of chromosomal Chystohalivka seedlings from exposed 0.9 µGy/h aberrations, the peak was in Railroad grade pines and productivity of 5.7 µGy/h 1986 and 1997; by 2001 crossing their seeds almost all studied populations Naftobaza (Oil 6.3 µGy/h returned to reference values, facility) 9 µGy/h in terms of the studied value. Asphalt plant Increased frequency of Yaniv 18.3 µGy/h mutations in isoenzymatic loci Axis of the west 7.5 µGy/h with increasing EDR. trace High variability in seed 26.3 µGy/h productivity both in the reference group and in Chornobyl populations. No changes in the survival rate of seed germinant from the exposed pines. 1995 Pinus sylvestris L. Asphalt and Cytogenetic changes in Exposure dose A significant increase in the All-Russian Geraskin et (Scots pine) concrete plant root meristem rate: percentage of aberrant cells Institute of al., 2003b Cherevach 12.5; 250; 2690 compared to reference values Agricultural [120] Obninsk (reference µrR/hour Radiology and

33 Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

Year of Object of research Sites Studied parameters Doses Obtained effects Organization Reference research site, RS) Agricultural Ecology (Obninsk) 2002 Pinus sylvestris L. Red Forest Global changes in DNA 10 Gy DNA hypermethylation in Chornobyl Kovalchuk (Scots pine) Chystohalivka methylation 80 Gy exposed pines as a function of Scientific and et al., 2003 exposure dose Technical Center for [137] International Research (Chornobyl) jointly with University of Lethbridge (Canada) and U.S. National Center for Toxicological Research 2004 Pinus sylvestris L. Reference Survival rate, biometric Absorbed dose Nonlinear dependences of Institute of General Igonina et. (Scots pine) Dytiatky parameters and (EDR) studied effects in relation to Genetics named al., 2012 morphological (0.18 µGy/h) dose. The most changes were after N.I. Vavilov, [138] Kopachi abnormalities <0.5 Gy (0.09 observed in the pine RAS Leliv (morphoses) in offspring µGy/h) population, where ancestors of the pines exposed (1.1 µGy/h) received a mid-dose in the Chystohalivka within the ChEZ 4–5 Gy (0.9 studied gradient (10-20 Gy), µGy/h) on the site named "Railroad Seed plot 4–5 Gy (5.7 grade crossing" with the EDR µGy/h) of 6.3 μSv/h. Railroad grade 4–20 Gy (0.25 crossing µGy/h) Asphalt plant 10–20 Gy (6.3 µGy/h) Naftobaza (Oil 10–20 Gy (18.3 facility) µGy/h) 10–20 Gy (9 Yaniv µGy/h) 80–100 Gy (7.5 Axis of the west µGy/h)

34 Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

Year of Object of research Sites Studied parameters Doses Obtained effects Organization Reference research trace 10–20 Gy (26.3 µGy/h) 2006–2007 Pinus sylvestris L. Ivankiv (outside Frequency of 0.0045–7.05 Dependence of morphological URIAR Yoshchenko, (Scots pine) ChEZ) morphological changes Gy/year change frequencies on URIH of Ukraine Bondar, Kopachi exposure dose rate 2009 [122] Yaniv Red Forest 2006–2007 Pinus sylvestris L. Ivankiv (outside Cytogenetic changes 0.0045–7.05 Dependence of cytogenetic URIAR Kashparov (Scots pine) ChEZ) Gy/year abnormalities on exposure URIH of Ukraine et. al. [139], Kopachi dose rate. 2009; Yaniv Correlation of cytogenetic Yoshchenko Red Forest abnormalities and availability et. al., 2010 of morphological changes [140]; Yoshchenko et al., 2011 [141] 2008 Higher aquatic plants Hluboke lake Cytogenetic changes 79–160 µGy/year Dose-dependent increase in Institute of Shevtsova, (Butomus Daleke lake 34–71 µGy/year the quantity of cytogenetic Hydrobiology of the 2010 [142]; umbellatus, Glyceria Azbuchyn lake 17–72 µGy/year abnormalities NAS of Ukraine Shevtsova maxima, Phragmites Yanivske lake 16–57 µGy/year and Gudkov, australis, Stratiotes ChNPP cooling 13–31 µGy/year 2009 [143] aloides, Sagittaria pond sagittifolia) Prypiat River 2.4–4.1 µGy/year Kyiv reservoir near Liutezh village 0.26–0.39 (outside ChEZ) µGy/year

2009 Pinus sylvestris L. Briansk region Gene polymorphism in 0.01–0.5 Gy Increased radioactive All-Russian Volkova, (Scots pine) (ChEZ in the RF) antioxidant enzyme of contamination of the sites up Institute of Geraskin, superoxide dismutase to 39 kBq/kg results in a Agricultural 2012 [144] verifiable increase in the Radiology and frequency of isoenzymatic loci Agricultural mutations, in effective number Ecology, Russian of alleles, in intrapopulation Academy of

35 Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

Year of Object of research Sites Studied parameters Doses Obtained effects Organization Reference research diversity and frequency of rare Agricultural morphs. Changes in genetic Sciences (Obninsk) structure of studied populations are due to increased frequency of rare alleles 2008 Betula pendula ChEZ Values of leaves Relationship between tree Vasyl Stefanyk Hanzha, (silver birch) fluctuating asymmetry. development stability in Precarpathian 2008 [145] Accumulation of 137Cs studied area and demutation National University and 90Sr by leaves. processes in urbolandscapes and radionuclide contamination 2009–2010 Arabidopsis thaliana 10 km ChEZ Resistance of seedlings to Increased resistance to Institute of Botany Shevchenko (thale cress) 30 km ChEZ genotoxins (determined genotoxin impacts named after N.G. et. al., 2012 Reference sites based on root growth), Increased expression of Kholodnyi, NAS of [146] outside ChEZ expression of cell studied genes Ukraine polyphasis marker genes 2011 Pinus sylvestris L. Near ChNPP Nucleotide diversity 2.6–16.4 Gy/year Higher nucleotide diversity of Chornobyl Center Vornam et (Scots pine), planted Pripyat city Gene expression of studied genes (catalase) and for Nuclear Safety, al., 2012 before the accident Red Forest antioxidant enzymes higher number of somatic Radioactive Waste [147] (aged 50 years) and Reference sites (catalase and glutathione mutations in studied genes and Radioecology, after the accident peroxidase) (catalase and glutathione jointly with Georg- (aged 20 years) peroxidase) in 50 and 20 year August University old tree populations, in of Goettingen comparison with reference (Germany) populations, irrespective of exposure dose rate 2015 Pinus sylvestris L. RF ChEZ Genetic and epigenetic 10-128 Gy/year Higher level of genetic All-Russian Volkova et (Scots pine) RB ChEZ changes polymorphism on Institute of al., 2017 contaminated sites compared Agricultural [148] to the reference ones. Radiology and DNA hypermethylation in Agricultural irradiated pines that does not Ecology (Obninsk, correlate with the pines’ RF), Center for

36 Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

Year of Object of research Sites Studied parameters Doses Obtained effects Organization Reference research radiation contamination level, Nuclear Research of this is due to increased Belgium, Flemish contribution of alpha-radiation Institute for to annual exposure dose on the Technological sites, where this effect was not Research (Belgium), identified. Polesie State Radioecological Reserve (RB)

37 Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

2 OPTIMIZATION OF RADIOECOLOGICAL MONITORING IN THE CHEZ

2.1 Retrospective of the network of research sites for scientific radioecological monitoring in the ChEZ

As early as in the first days of the accident in 1986, a large number of scientific teams arrived to the ChEZ. Almost all the units and components of ecosystems radioactively contaminated were subject to the studies. Much of the researches were applied in practice when developing proposals for the liquidation of disaster consequences. For example, efficiency of respiratory protection equipment, radio-protective properties of various food additives and chemical compounds used to reduce the exposure effects for a human body were studied. A specific direction of scientific research in the ChEZ was studying the paths of radionuclide intakes by organisms of the farm livestock and plants. Based on the results obtained, some farming techniques were proposed for the contaminated areas.

Offices of the USSR Academy of Sciences, expeditions and focus-groups of relevant scientific subdivisions (State Hydrometeorology Committee, Ministry of Health, AUA AS, Ministry of Defence, etc.) were working in the ChEZ. Scientists were acquiring information about the distribution of contamination within the area, composition of radioactive releases, general development trends, and incurred damage.

The data obtained were quickly applied to address some specific problems, i.e. to justify managerial decisions, develop new technologies, prepare engineering and technical solutions. Moreover, there emerged a need to review most of standard, routine process operations meant for ordinary life. Under the conditions of the contaminated environment and intense radiation fields, their performance required a new approach to both using manpower and machines. For that reason, most of work in the exclusion zone had scientific support.

All of the above applies to the period before 1991, i.e. to the first five years after the accident. At that time, science was inherent in the exclusion zone and scientists were a detachment in the army of liquidators. Organization of scientific activities was of in-process nature then; teams from many reputable scientific organizations were working there under general coordinating supervision. Difficult conditions, variety of assigned tasks and high priority of the accident liquidation activities secured state support to the entire structure.

The situation changed by the early 1990s; an acute period of the accident was over, the Sarcophagus was built, ChNPP Units 1, 2 and 3 were put into operation, decontamination of “near zone” around the plant was finished. The need in coordinating liquidation of the accident consequences at the all-Union level has disappeared. The exclusion zone finally formed as a detached area, with the autonomous management of republican level. The on-stream organizational structure of science started its disintegration due to the breakup of the Soviet Union, funding of science was cut down. The centre stage was given to accompanied problems, such as radioactive waste management.

There emerged a need to establish own scientific structures of republican level that would ensure scientific support to the accident consequences elimination activities within the exclusion zone. This is how the ChEZ science appeared, and it existed exactly for one decade (1991-2001).

Developing the actual distribution pattern of radioactive contamination within the ChEZ, studying the state of Shelter Object and effects of exposure, testing the methods of agricultural protection; all these have been done in great detail and required a considerable effort.

38 Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

However, it should be emphasized that not a single fundamental discovery, which would be accordingly registered or recognized by the international community, has been made based on the Chornobyl data.

All hazards that arose after the accident have only one ground, i.e. nucleus decay, which fully fits the ideas of modern nuclear physics with the half-century history of nuclear technology. At first glance, this danger could be generally overcome and controlled, since there are protection means and decontamination technologies available. No principally new objects have been found. Of course, unless you regard the "hot particles", which simulation has been carried out by the Kurchatov Institute for 20 years before the accident, and the thyroid gland reaction of children (we do not mean the fact of affection itself, but the dynamics of biological effect manifestations). The accident did not cause appearance of mass mutations, which were so feared of.

The science has got a strategic challenge to return the areas into economic circulation. Some specific scientific tasks should have been addressed to implement that strategy, i.e. study effects of radioactive contamination for environmental conditions, justify and develop cleaning techniques for the areas, landscapes and/or certain types of economic products.

In the late 90's, the science started demonstrating signs of depression. A main reason of the depression is conceptual one. There has been no common and accepted-by-all-the-parties concept of the exclusion zone, which could have formed a basis for a relevant research program development.

The works on Chornobyl topic were massive and included a search for a technology of getting clean products for forest, fish and farm businesses; study of radiation effects for living organisms and ecosystems; study of contamination situations in natural objects. One would think that performance of those massive researches should be nothing but welcomed. However, a complete research cycle with a large number of individual directions can only be possible with sufficient resources.

They were not available; and a steady reduction in funding was the crucial negative factor that significantly hampered development of science in the ChEZ.

As a result, quality of scientific works went down. The drop in quality was developing according to the positive feedback principle. Experts were leaving, unable to endure neglect of science by local officials in the ChEZ. Formally, funding under national targeted programs supported very many researches. However, the absolutely scarce resources were distributed among many tasks, and as a result none of the problems has really been solved.

The overwhelming number of scientific initiatives was a simple recording of measurement results on radionuclide concentrations in various environments and monitoring objects.

Finally, in 2002 it was decided to cut down scientific divisions in the ChEZ. The scientific sites and field stations were disposed off and experienced slow degradation. The scope of research that existed in the exclusion zone until 2002 is clearly demonstrated by the map of scientific and experimental sites location (Figure 2.1). The overwhelming majority of them are not used today.

Additionally to scientific polygons with specific target areas, there were some pilot sites within the ChEZ that were not identified in the terrain. Those scientific and observation sites were used for the regular observations of natural processes and sampling of environmental objects. Each area of research had dozens of such sites throughout the exclusion zone. Staff calls such scientific polygons and sites simply "points".

39 Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

About 50 sampling sites were organized to assess radionuclide migrations into plants. Several sampling points (Pripyat city and the ChNPP cooling pond) existed within the system of radioecological research of aquatic ecosystems. Studies of reference animal species and phyto-sanitary monitoring were carried out on up to 10 observation sites.

Figure 2.1 - Layout of scientific sites in the ChNPP exclusion zone in 1998

Figure 2.2 - Progress of works at the experimental site named “Chystohalivka”

40 Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

Figure 2.3 - Current state of scientific sites in the ChEZ

41 Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

Figure 2.4 - Greenhouse facility in Pripyat city in the mid-1990s

Figure 2.5 - Experimental bee-garden near abandoned greenhouses in the city of Pripyat

42 Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

Figure 2.6 - Research on the environmental monitoring of the ChCP

2.2 Routine monitoring

The recommendations for optimization of routine monitoring of main objects are presented below.

Air. The routine monitoring system for radioactive aerosol concentrations in the surface air and its deposition intensity in the ChEZ should receive relevant scientific guidance, modern equipment, performance of cross-sectoral and international comparative checks and calibrations, and its staff should receive training. Density of observation sites on the ChEZ periphery should be increased with due regard for all potential sources of airborne radioactivity release and dispersion, and also taking into account the geographical spread of nearby population centres. Equipment used for the airborne radioactivity sampling should be updated, certified and calibrated, with due regard for the requirements of international standards.

Optimization of the network is currently in progress.

It is proposed to improve the monitoring regulations through introduction of isokinetic sampling modes with the use of impactors for assessing dispersed composition of a radioactive aerosol; performance of morphological analysis of aerosol samples; and application of statistical analysis to identify trends, seasonal trends and radioactive aerosol formation sources in the ChEZ.

Surface water. Only few observation sites are used to monitor transport of radionuclides outside the ChEZ with water, with the objective to justify and plan radiation protection measures for public. The remaining observation sites should be focused on addressing the tasks of scientific monitoring; research plans and programs should be agreed by all concerned organizations. To this end, a survey of targeted scientific organizations is in progress now.

Groundwater. Only few observation sites, including RWTLS and RWDS, are used to monitor transport of radionuclides outside the ChEZ with water, with the objective to justify and plan radiation protection measures for public. The remaining observation sites should be focused on addressing the tasks of scientific monitoring; research plans and programs should be agreed by all concerned organizations. To this end, a survey of targeted scientific organizations is in progress now.

43 Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

Centres of population. Routine monitoring should be carried out annually in accordance with Procedure-96 [6] in different seasons in order to assess effective doses of public exposure; diet of local residents should be specified, the list of monitored foods should be expanded according to the diet. Special attention should be given to measurements of strontium 90Sr and caesium 137Cs. Expected doses of the self-settlers’ exposure should be verified basing on radiation control of external and internal exposure doses (WBC and measurement of strontium 90Sr concentration in urine).

Terrestrial ecosystems. This type of monitoring is indirectly related to the planning of personnel radiation protection, it should be referred to the scientific monitoring and meet its objectives.

To improve the monitoring Procedure, it is proposed to implement remote monitoring and observation techniques, while applying techniques of airspace images decoding, using quadcopters and UAVs for the monitoring observations. These are particularly important for assessing biota and sanitary conditions in the ChEZ.

Man-made objects. All infrastructure facilities are referred to the ChEZ man-made objects, including the ChCP and radioactive waste localization sites. The man-made objects monitoring procedure is described in 1.2.5.

2.3 Scientific monitoring

Ukraine proposed the IAEA to use ChEZ as a major observation site for radiation monitoring to accumulate the empirical data needed for justification and planning of radiation protection activities for humans and the environment.

The scientific monitoring network should be selected based on the prevalence of landscapes in the exclusion zone, in such a way as to cover all components that the critical from the viewpoint of radionuclide migrations, exposure doses of humans and biota. The objects, network, regulations, and methods of sampling, measurement, data processing and storage should be unified and optimized in order to obtain representative data of the radioecological monitoring.

2.3.1 Development of criteria and requirements for the monitoring system of terrestrial ecosystems At the local, national and international levels, the modern monitoring system for ecosystems is implemented under the support of Earth's remote sensing and geoinformation technologies. Though additional aboveground data from experimental works and accurate georeferencing of experimental sites are needed to develop satellite observations of shrub and meadow ecosystems; there is no such problem with forest ecosystems.

In terms of their geometric and spectral characteristics and if combined with aboveground survey results, the free-access data on Earth remote sensing obtained from Landsat-7,8 and Sentinel-2 (A and B) satellites and intended for monitoring of forests and changes in the earth cover are quite applicable for clarifying the current geographical location of landscapes within the ChEZ and assessing their state [149].

The analysis data for Landsat time series images of Global Forest Watch map (Figure 3.7) were used to identify the changes that occurred in 2002-2014 in the structure of forest (covered with forest vegetation) and non-forest lands. The map was published in 2013 (the University of Maryland, USA) and was repeatedly tested in the territory of Ukrainian Polissia, and particularly in the ChEZ [150]. All of the above actions allow selecting sites most fully corresponding to the actual pattern of landscape type distribution within the area. 44 Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

Analysis of data from the Global Forest Change, a global map of forest changes, demonstrates that during 2002-2014 the actual average increase of the ChEZ lands covered by forest vegetation was approximately 363 ha•year-1; therewith, an average of 592 ha•year-1 became forest plantations and 293 ha•year-1 were deforested; this is also confirmed by the publication of Zibtsev et al. [151]. Although this annual values demonstrate a considerable variability over the years, a positive balance towards a forest cover increase in the ChEZ was observed in a stated period. According to the article of Evangeliou et al. [152], in 2015 there was a mass drying in the area of 9.2 thousand hectares almost throughout the entire territory of burned areas resulting from the two "big fires" on the area exceeding 16 thousand hectares. Nowadays, almost all the plantations damaged by fire can be considered dead (Figure 2.8).

Figure 2.7 - Forest cover in the studied area and its changes (2001-2014) as per the data of Global Forest Watch interactive site [153]

45 Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

Figure 2.8 – Forest-covered areas lost as a result of fires in 2015-2016 (blue color highlights 2015 and red color marks 2016) in the ChEZ, according to Global Forest Change on-line map [Error! Bookmark not defined.]

Initial forest inventory data on the ChEZ forest reserve allowed presumable identification of distribution of lands with forest cover and with natural afforestation. The stands structure was studied in terms of its prevailing tree species (Figure 2.9), age (Figure 2.10) and other parameters. Aggregation of the forest sites taxation values from various sources of information with the results of own instrumental surveys allowed identification of significant uncertainties in the available forest taxation data. Therefore, for possible optimization of radioecological monitoring system for the forest ecosystems and within the framework of this work we organized experimental sites in locally-typical plantations (Figure 2.9, Figure 2.10) represented by pure stands of Scots pine and white birch (15 sites in total). Two basic sites were organized pursuant to the requirements for test sites of forest taxation, in accordance with SOU 02.02.-37-476: 2006 [154], another 13 sites were organized pursuant to the form accepted for forest inventory operations, i.e. circular test sites that varied in their area. Separately, two experimental sites were established in the 30-year-old cultures of Scots pine, which were planted at the RWTLS "Red Forest" and RWTLS "Naftobaza" because 100% tree mortality of pre-accidental pine plantations was observed there after the Chornobyl accident (marked by points 16 and 17 in Figure 2.9 and Figure 2.10). Samples of wood and soil were taken from all the above-listed forest sites; assessments of caesium 137Cs and strontium 90Sr concentrations in the stand components are in progress now. Such an approach allows obtaining a pattern of actual redistribution of specific activities of radionuclides in soil and in the forest stand components, as well as justifying sampling recommendations for the experimental sites.

Since 2006, there have been a few comprehensive phytocenotic (geobotanical) studies and bioproductivity assessments in the terrestrial landscapes of open type targeted at studying the radioecological aspects of these ChEZ ecosystems [155].

46 Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

Figure 2.9 - Spatial distribution of woody plant species on the forest-covered lands and in the areas with intense forest cover

Figure 2.10 – Distribution of forest stands and of probable areal re-afforestation based on average age, years

47 Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

Currently, there is no systematic approach to routine and scientific radioecological monitoring of terrestrial ecosystems in the ChEZ. SSE “Ecocenter” performs routine monitoring annually, at 15 landscape sites, which is insufficient. The basic problem of ensuring observations in the radioactively contaminated areas is a lack of database and clear requirements for methodological approaches to data collection and processing.

From the view point of radioecology, typical and critical landscapes used for periodical monitoring should be identified based on comprehensive scientific research (scientific monitoring). Further, all characteristics obtained for a certain biogeocenoses, starting with density of soil contamination with basic artificial radionuclides and ending with phytocenosis bio-productivity, should be populated into a relational database. Also, scientific monitoring of all ecosystems should be performed in case a crisis phenomena occurs (forest fires, prolonged floods, reservoirs drying, etc.), in order to assess its effects on distribution of radionuclides in affected cenoses, transfer of radionuclides beyond the ChEZ borders. Increased role of the ChEZ, as an experimental site, for international scientific community in studying a biogeochemical cycle of biologically mobile radionuclides in natural systems, radiobiological effects and many other topical aspects of radioecology and radiobiology should be promoted through a possibility for foreign scientists to get certain reliable initial data from already existing experimental sites; this will allow us to perform our own research works. Also, results of systematic observations of artificial and natural ecosystems obtained from really existing experimental sites through justified methodological approaches are the best educational content for training national and foreign experts.

48 Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

3 APPROBATION OF SCIENTIFIC MONITORING IN THE CHEZ ECOSYSTEMS

3.1 Air

A source function should be specified in a scientific program in order to predict changes in the radiation situation and to plan activities for the radiation protection of public and personnel in case of various types of forest fires in the ChEZ. Since during the fires of all types, most of radionuclides come from forest litter or grass layer, relevant researches should be performed in the ChEZ, for example, with the use of a radio-aerosol sampler shown below (Figure 3.1).

Figure 3.1 – Schematic design of a radioactive aerosol sampler used to study radionuclides transport from litter during fires in the natural conditions of ChEZ

To assess the radiation and sanitary working conditions of personnel within the ChEZ, the URIAR employees investigate inhalation intake of radionuclides during works performed in the 10-km zone. Figures 3.2 and 3.3 present a photo of such research in progress during the tilling of fire bands in 10- km zone around ChNPP.

Figure 3.2 - Tilling of fire bands in 10-km zone around ChNPP (Kopachi village)

49 Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

Figure 3.3 - Installation of aerosol samplers in a tractor cabin

Two “Typhoon” air blowers with controlled air pumping rate ranging between 10 and 100 l/min were used to sample aerosols in a tractor cabin. To estimate radionuclide activity concentrations, an aerosol was sampled on AFA-PMA-20 filters made of Petryanov material. Five-stage impactors were used to assess the dispersed composition of radioactive aerosols and estimate the aerodynamic median diameter based on activity.

Currently, scientific monitoring of radionuclide re-suspension from the ChCP drained plots is performed under both normal and extreme conditions, such as dust storms.

3.2 Surface waters

Proceeding from the radiological monitoring objectives, we may conclude that current monitoring of aquatic ecosystems in the ChEZ is excessive, while the monitoring of terrestrial ecosystems is insufficient, i.e. the data supplied to forecast a possible economic use of their components (such as wood) are incomplete.

The concentrations of radionuclides in water change very slowly nowadays, thus allowing longer intervals between the measurements in order to record reliable differences. The relevant observations are in progress at the Hlyboke Lake and on a pond near the village of Starosillia; it is advisable to continue them (Figure 3.4).

Figure 3.4 - Scientific monitoring on a reference water body near Starosillia village in December 2017

50 Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

Optimized regulations for water monitoring in the ChEZ should allow monitoring of radionuclides transport outside the ChEZ.

Contamination of bottom deposits is an important data source for an aquatic ecosystem characterization. Bottom deposits are perspective objects of analysis that present a pattern of long-term contamination (particularly, in low-flow water bodies). Bottom deposits are indicators of ecological conditions in both water bodies and their entire catchment area. Unlike surface waters, compositions of bottom deposits can be observed once in two years. Environmental assessment of the condition of bottom deposits is complicated from a formal point of view due to the lack of standard indicators. Therefore, background concentrations can be taken as initial indicators of chemical composition of bottom deposits, thus allowing tracing of contamination dynamics.

3.3 Groundwater

Scientific monitoring of radionuclide migrations outside the RWTLS with groundwater, including the transuranium elements (TUE), should be continued using the example of CPS "Red Forest" (refer to paragraph 4.1.3.5).

3.4 Monitoring of meadow and meadow-shrub ecosystems

These ChEZ ecosystems have the second highest prevalence after forest ecosystems. They are former croplands, which have turned from anthropogenic to natural ecosystems as a result of succession processes occurring after the accident. To date, some of them have turned into dry meadows with shrub vegetation, and some are almost completely covered by natural forests. Dynamics in these biocenoses is of interest from the radioecological viewpoint, since it can cause changes in radionuclide fluxes between the ecosystem components, including changes in the intensity of radionuclide vertical migrations in soil cover.

A large amount of experimental data has been accumulated to date. These data characterize features of vertical migration of basic radiologically-significant radionuclides in the exclusion zone soils. Hydromorphic organogenic soils (peat-bog soils of different moistening degree) are known to be critical to caesium 137Cs. Migration intensity of this radionuclide in automorphic sod-podzolic soils with various mechanical compositions is rather low (most of its activity in the undisturbed soils is currently contained in a 5-cm layer of topsoil). Due to the physicochemical properties of strontium 90Sr, its mobility in soils differs significantly from that of caesium 137Cs and TUE with equal migration conditions. Soil conditions in the ChEZ are generally favourable for the vertical migration of strontium 90Sr and sometimes its intensity can be tens of times higher than that of caesium 137Cs. Content of organic matter in soil is the critical parameter impacting the migration mobility. Lean cryptopodzol soils are the most critical ones; and due to vertical migration processes, significant amounts of this radionuclide have moved in these soils to a depth exceeding 1 meter. For example, in the sand dunes of the Pripyat River pine-forest terrace, in the grass and grass-moss wastelands ecosystems that are at the first stage of overgrowing, the peak of strontium was observed at the depth of 60 cm as early as in 1996, while the most of other radionuclide activities were contained in the surface soil layer (Figure 3.5).

Therefore, from the scientific point of view, the vertical migration processes of radionuclides (particularly, of strontium 90Sr) are certainly of some interest, since they impact the radionuclide concentrations in root soil layer and hypothetically can cause penetration of radionuclides into a saturated zone and further to rivers with groundwater flow. To obtain the reliable parameters of radionuclide distributions in soil and assess their dynamics, an appropriate methodological approach is required, which should take into account at least the following points: • Monitoring network should cover critical soil differences, from the viewpoint of radionuclides’ migratory mobility;

51 Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

• As for the studied radionuclides, contamination density at the monitoring network points far exceeds the pre-accident levels; • Information on vertical distributions of these radionuclides in the previous years is needed; • Since the processes of vertical migration lead to a fairly slow redistribution of radionuclides in soil profile, there is no need to take samples every year. For most observation points, the sufficient sampling would be once per five years. The procedure may be adjusted for the points with observed intensive migrations; • Sampling depth should be estimated with due regard for preliminary data on the migration intensity, but cannot be less than 40 cm; • Sampler design and sampling technique should ensure minimal contamination of samples during separation of a soil core; • Thickness of sampling layer should depend on expected intensity of radionuclide migrations, usually it varies within the range of 2-5 cm; • Quantity of soil cores should ensure identification of differences between the profiles sampled at different times (preliminary estimates state from 5 to 10 profiles) with a certain level of confidence; • Parallel samples from the same depth taken at different locations of a site at the same time should not be mixed to form a composite sample. To obtain statistical parameters for characterization of radionuclide vertical distributions within entire site at a certain time, radionuclide concentrations should be measured in every sample. The point is that soil is a very heterogeneous medium, and vertical distributions of radionuclides within the same site at the same time can be very different (Figure 3.6).

In 1988, the URIAR established a network of experimental sites in order to organize observations of radionuclide vertical migrations intensity. The network covered main soil differences in the ChEZ and all types of forms of radioactive fallout (Table 3.1). The network has been used for the studies until 2010, with varying intensity, depending on a financial state. Following the incorporation of environmental changes, this network can be used nowadays to study the processes of vertical migration.

52 Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

Figure 3.5 - Vertical distribution of radionuclides in the profile of cryptopodzol sandy soil (1996, p.13)

Figure 3.6 – Vertical distribution of caesium 137Cs in soil profile, sampled at the same time within an experimental site of 50х50 m (2015)

53 Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

Table 3.1 - Description of experimental sites for studying vertical migrations of radionuclides and contamination of soil with radionuclides (contamination density as per 1996) Soil contamination density, Item Description of experimental sites Coordinates MBq/m2 No. 137Cs 1 Natural meadow formed on sod-podzol 51.376079 20±10 1 sandy loam soil 30.04056 2 Natural very wet meadow formed on 51.37611 28±14 2 peaty-podzol soil. Thick turfgrass 30.03333 3 Natural meadow formed on sod-podzol 51.375810 24±10 3 sandy loam soil. Thin turfgrass – moss 30.021607 4 Sod-podzolic sandy loam soil, 51.343181 2.6±0.6 4 cultivated before the accident. Medium 30.103519 turfgrass – grass. Is currently overgrowing with pine trees 5 Sod-podzol gleyed soil, cultivated 51.446101 2.8±0.8 5 before the accident. Medium turfgrass 30.138289 – grass 6 Sod-podzol gleyed soil, cultivated 3.4±0.9 6 before the accident. Thin turfgrass – moss 7 Natural very wet meadow formed on 51.412778 1.2±0.3 7 sod gleyed soil. Thick turfgrass. 30.199167 Currently, it is a fallow 8 Sod-podzol sandy loam soil, cultivated 51.356936 3.8±1.0 8 before the accident. Thin turfgrass. 29.905042 Is slowly overgrowing with forest 11 Cultivated meadow formed on sod- 51.331392 1.1±0.3 11 podzol sandy loam soil (was cultivated 29.784067 before the accident) 13 Floodplain of the Pripyat River, sandy 51.41889 15±6 13 cryptopodzol soil. Thin turfgrass. River 30.07306 floodplain, shrubs

3.5 Justification, selection, organization and equipment of experimental sites for terrestrial ecosystems

3.5.1 Definition of requirements Scientific and routine radioecological monitoring of ecosystems on the ChEZ experimental sites should be targeted at addressing the following tasks: forecasting of man-caused radionuclides redistribution in natural systems and in artificial objects within the radioactively contaminated areas; identification of regularities in radionuclide behaviour, which may be used for decision-making in case of accidents at nuclear and power facilities, which involve radioisotope releases into the environment. Statistical values for the distribution of radionuclide concentrations in soil and in biomass components, as well as characteristics of growth in the forest stands, indicate that even with significant observation (or sampling) scopes, the accuracy of values established for radioactive contamination of ecosystem elements shall be minimum 20% [156]. Therefore, counting frequency at experimental sites should be 5 years or rarer. A shorter parameter recording period in natural ecosystems may be required in case a disastrous phenomena or succession are registered on a site. Considering the fact that a number of test 54 Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

areas in the forest-covered area within ChEZ should be minimum 50 [157], the number of experimental sites in open types of natural terrestrial landscapes should be minimum 30. That is, during 1 year samples should be taken from 16 testing sites representing the terrestrial ecosystems. The vast majority of experimental sites may be used for assessing the effects of ionizing radiation in reference organisms, since the majority of forest stands shall be represented by Scots pine and species of Poaceae family shall often be found among the topsoil living cover [158].

Nowadays, the abovementioned experimental sites must be geographically linked by mans of GPS. Rectangular test plots within a forest site should have its borderlines marked by border posts, and only a central post should be installed for circular ones. It should be noted that circular test plots are organized by means of modern laser-optical equipment (Haglof LaserGeo, Laser Technology TruPulse or other similar geodetic systems) (Figure 3.7) and special software; they can be restored with 1 cm accuracy in case there are no any visible marking signs there over a long time, after the last survey visit to the plots.

a b Figure 3.7 - Modern laser optical equipment for forest taxation and inventory: a) by Haglof LaserGeo; b) by Laser Technology TruPulse 360

Experimental sites in open-type landscapes should have clear boundary marks, representative plots should be divided into squares in staggered order, because comprehensive studies of shrub and grassy plant species, description of species composition and sampling should be performed in different growing seasons. Points of soil sampling, test sites for living topsoil cover, trees sampled for radiological investigations should be marked on a map or visibly marked on the plots. On the one hand, this ensures data verification possibility; and on the other hand this excludes possible re-entering to previously "processed" soils, or biomass, or mortmass components.

A layout of rectangular test plots in closed forest plantations prior to soil or vegetation sampling is shown in Figure 6. Its inner squares are coded in a certain order: most often a staggered order is used, however others can be also used (in Figure 6, they are marked with gray letters (top) and numbers (left)). Trees growing in a certain square get its code, correspondingly. Soil is sampled at the corners of the square, and samples are also coded following the same pattern; however they are referenced along lines or sides of the square (in Figure 3.8, they are marked with black letters (bottom) and numbers (right)). The dimensions of inner squares may vary, but most often the sides of 1, 2, 5 and 10 m are used. Establishment of conditional squares on a site allows mapping the following: ambient dose equivalent rate (EDR), density of soil surface contamination with a studied radionuclide, collected experimental field material, etc. This method is the most successful in organizing experimental sites for long-term stationary observations.

55 Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

Figure 3.8 – Layout of inner squares on rectangular test plots

If specific equipment for forest inventory is available, radioecological experimental plots of circular form with constant radii1 can be organized much faster than rectangular test plots. Depending on a tree stand density, the test areas may be of different sizes (S-r): 100 m2 - 5.64 m; 250 m2 - 8.9 m; 500 m2 - 12.6 m; 1000 m2 - 17.8 m; 5000 m2 - 39.9 m (for more details see Figure 3.9). A tripod with equipment is installed in a test plot center (Figure 3.9, point "C"); then coordinates are identified and trees are recorded. In case there is no direct visibility of some trees from a circular test plot center, equipment should be moved to better “position” points, which coordinates are pre-identified by the equipment itself. A compass point is selected to be the starting direction of tree recording (Figure 3.9, points "N", "W", "S", or "E"). Most often, soil sampling from a site is carried out by the statistical sampling method (i.e., similar division of a studied site into squares within a circular test plot). The main advantage of this method is the possibility to apply georeferencing of different types to certain trees, which makes it possible to reliably assess the variability of forest taxation characteristics within a selected forest plot; and in its turn, it ensures important data for applying satellite monitoring to the studied forest ecosystems. Another significant advantage of this method is the possibility to rather accurately map sampling points (± 0.1 m); and in case an experimental site is used for long-term studies, this will ensure avoidance of disturbed areas on soil surface or taking wood samples only from specific reference trees.

1, The following three types of circular test plots are distinguished in practical forest inventory: with constant radius, with variable radius and prism-count (relascopic). 56 Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

Figure 3.9 – Organization of circular test plots

Labour inputs in the monitoring observations can be reduced through close location of sampling sites and areas, in groups of 5-7 pcs., while including ecosystems of various types into the groups, where applicable. This shall allow implementation of remote landscape monitoring system in the entire ChEZ, and experimental sites can be used as data sources for the establishment of satellite images classification signatures. Scientific radioecological monitoring of radionuclide biogeochemical cycles in ecosystems should be carried out in ecosystems with sufficiently high levels of radiation contamination, starting with 1.0 µSv•h-1 ambient dose equivalent for gamma and X-ray radiation (as for 137Cs) at 1.0 m height above soil surface, or sometimes even higher. Otherwise, estimates for radionuclide fluxes (for example, their washout with rainwater or vertical migration in lower soil layers) may not have sufficient accuracy due to a significant measurement error. Preliminary survey of sites, which are planned to be included into test areas, also includes a uniform sampling of soil from 20 cm top mineral layer at grid points of squares within a potential site (a square may have any lateral length, but the total number of samples from a plot should be minimum 30) used to estimate the site’s radionuclide contamination density. Vegetation biomass and mortmass of should also be sampled (sampling of heartwood from 9 model trees while observing proportional representation in a stand thickness levels, is enough for forest plantations).

Based on the studies performed by the staff of the Ukrainian Research Institute of Agricultural Radiology, Department of Forest Taxation and Management under the National University of Bio- resources and Nature Management, which were repeatedly described in scientific publications [156, 159], a list of forest taxation parameters was developed to be used while recording of trees, taxation of model trees, and estimation of tree stands. Simultaneously, bio-productivity parameters should be calculated for aboveground biomass and mortmass (detritus) components of a plantation. For living

57 Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

ground cover, botanical description of sites should be performed, inclusive of estimations of aboveground biomass and mortmass inventory of plants, and using a technique from the transect method.

Litterfall and living topsoil cover should be sampled from 1 m2 plots. Litterfall should be divided into three layers by its destruction degree (in case all the layers could be traced): fresh (1-year) litterfall, litterfall from previous years with clearly identified structure, decomposed organic layer. Then, soil samples should be taken layer-by-layer to a depth of up to 1 m, at the same location and at least at five surface points without pooling them, which is due to a significant vertical migration of 90Sr. Concentrations of radionuclides should be measured in all soil samples separately in order to assess variation parameters of their specific activity.

Observations from specially equipped stations are required for the development of mathematical models for the biogenic fluxes of radionuclides in forest ecosystems. Samplers for litterfall and atmospheric water should be installed at the stations; samples should be taken from them at set time intervals (usually 1 month). Preliminary, 9 to 12 model trees should be cut on a site before a vegetation period or after it. The cut trees should be further carefully divided into samples of their aboveground biomass components: leaves/needles (1, 2, 3 years old), one-year shoots, shoots shorter than 1 cm, shoots longer than 1 cm, outer stem bark, inner stem bark, stem sapwood, heartwood (depending on age and wood species). Dead parts of living trees should be isolated separately. Using the method of soil cross-section or monolith, vertical distribution of root fractions should be assessed according to the following three ranges of thickness: less than 2 mm, 2-50 mm, and over 50 mm. After weight measurements (a tree stem volume is measured by the methods of stereometry), the above listed aboveground and underground biomass components should be sampled and then dried at 70°C in order to estimate bio-productivity of plantation components and measure radionuclide concentrations in them. The obtained data on main depots and radionuclide fluxes in forest ecosystems allow more accurate forecasting of their future concentration values, if compared to the conservative estimates that involve transition coefficients [160, 161, 162, 163].

After an experimental site or a research area is established and equipped within a forest or meadow phytocenosis, it should be rated through its introduction into a specially designed database on all characteristics obtained from a site within a terrestrial ecosystem, unique or consecutive number or code should be assigned. Now, we can identify some characteristics that should be determined obligatory: geographic reference in WGS84 system, type of vegetation cover, date of establishment, average contamination density for basic radionuclides, bio-productivity characteristics. In case of repeated recording effort on a site, the new data should be stored in the same databases in order to quickly systematize and analyze them. Generally, the requirements for permanent test sites in forest plantations have already been developed a long time ago; including the list of forest taxation parameters to be taken into account while establishing a test site in a forest and further repeatedly visiting it.

3.5.2 Experimental efforts on forest sites. Determination of inventories and fluxes of biologically mobile radionuclide in typical forest plantations According to the data obtained from the updated site-based database of the Production Association "Ukrderzhlisproekt" (Ukrainian National Forest Project), forest-covered areas within the studied area (using the example of SSE "Pivnichna Pushcha"(North Forest)) are most often represented by the following tree species: Scots pine (59.7%) and silver birch (25.5%); other forest-forming species are much rarer (for details see Table 3.2). Therefore, an experimental site (ChZ-1) was established in a Scots pine plantation to obtain the input data. In order to study all available fluxes of organic matter, this forest site was equipped with samplers of litterfall, stem and crown waters. Within the studied tree stand, this forest site has uniform soil conditions and forest taxation parameters, average concentration

58 Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

of 90Sr in its tree stem wood exceeds 10 kBq•kg-1: in case the values of wood specific activity are lower, estimates of 90Sr downstream in the rainwater shall be limited in a low-temperature season due to possible lower concentrations of the radioisotope, below the detection levels of β-spectrometers and radiometers available at the URIAR laboratories.

Table 3.2 – Distribution of forest areas in the Chornobyl exclusion zone by prevailing tree species and their age, thousand hectares Age, years Sub- Tree species % unde 21- 41- 61- 81- 101- over 120 total r 20 40 60 80 100 120 Black alder – Alnus glutinosa 0.79 3.27 4.12 1.69 0.17 0.00 0.00 10.04 6.7 Silver birch – Betula pendula 13.66 13.99 7.99 2.53 0.05 0.00 0.00 38.22 25.5 Scots pine – Pinus sylvestris 6.76 13.81 42.44 16.98 7.71 1.55 0.09 89.34 59.7 Aspen – Populus tremula 0.09 0.33 0.79 0.35 0.01 0.00 0.00 1.57 1.1 Common oak – Quercus robur 0.16 1.31 2.40 1.12 0.53 0.78 1.34 7.64 5.1 Other species 1.84 0.59 0.37 0.07 0.00 0.00 0.00 2.87 1.9 TOTAL 23.30 33.30 58.11 22.74 8.47 2.33 1.43 149.7 100

Major depots and fluxes of 90Sr in the pine forest were studied using the methodical approaches, which have already been tested repeatedly during the parametrization of mathematical models for the biogeochemical cycle of 137Cs. In most cases, the following depot units are used to this end: tree stand phytomass (needles (leaves), shoots, tree stem (outer bark, inner bark, sapwood, heartwood)), roots, tree stand mortmass (dead leaves, dead wood, dead parts of living trees), litterfall (according to available decomposition layers), soil mineral component (where layers are also distinguished, depending on a studied radionuclide migration depth). The main fluxes transporting the biologically mobile radionuclides include: growth of tree stand phytomass components, formation of mortmass (litter and dead leaves), meteorological washout of radionuclides from the surface of terrestrial phytomass components, migration of radionuclides beyond the soil root layer. In case several forest elements (tree layers, woody or shrubby plant species) are present in tree stands, each of them should be studied to reliably assess their radionuclide "balance".

Due to the availability of a significant amount of data on 137Cs behavior in forest ecosystems and lack of such information on 90Sr, we decided to measure concentrations of the above-listed radionuclides simultaneously. This shall allow comparison of their redistribution patterns in forest biogeocenosis.

The experimental forest site is located 5 km to the north from Unit 4 of the Chornobyl NPP, within the left bank floodplain of the Pripyat River (for more details see Figure 3.10). According to the latest forest inventory, it is referred to site 8, quarter 80 in the Paryshiv Forestry of the State Special Enterprise "Pivnichna Pushcha" (North Forest) (Ivankiv district, Kyiv region).

P1 N 51.43442° E 30.10785° P2 N 51.13915° E 28.60047° P3 N 51.13872° E 28.60063° P4 N 51.13880° E 28.60133°

59 Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

P2 P1

P3 P4

Satellite and geographic data were obtained by means of QGIS and Google service software Figure 3.10 – Geographical coordinates of site boundary posts

The site was organized in accordance with the requirements for test sites that are regulated by the rules of SOU 02.02-37-476:2006 [154]. The selected site is 30x30 m: 0.09 ha. The pine site has thickened forest trees, 53 years old. The forest inventory parameters of the plantation are presented in the text below.

The preliminary mapping of the site contamination was carried out by determining its EDR at 1.0 m height, at the points of 5 m square grid (Figure 3.11); this allowed to estimate the relative value variability - 7.3% (AM±SD 2.77±0.20 μSv•h-1), which indicates a lack of pronounced differences in radionuclide distribution on the site (uniformly contaminated) [164]. Further, soil samples were taken at each intersection point of the square grid in order to estimate soil contamination density for 137Cs and 90Sr. The soil sampling depth was 20 cm. The detailed measurements results for specific activity of 137 90 137 90 Cs (Am137Cs) and Sr (Am90Sr), as well as estimates of soil contamination with Cs and Sr are graphically presented in Figure 3.12, Figure 3.13. The average density of soil contamination with 137Cs was 2675±1080 kBq•m-2, and with 90Sr – 494±362 kBq•m-2. Anomalously high values of radionuclide concentrations were recorded at point G3; at the first sight, they could be caused by the presence of hot particles, however detailed analysis of soil sample has not confirmed this assumption. The data on radioisotope concentrations at this point were disregarded in the calculations.

60 Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

Figure 3.11 – EDR at the points of square grid on the experimental plot, µSv·h-1

Figure 3.12 – 137Cs contamination density in 20 cm top soil layer, MBq·m-2

61 Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

Figure 3.13 – 90Sr contamination density in 20 cm top soil layer, MBq·m-2

To obtain reliable data on the studied forest site, the methods of forest inventory, forest management, radioecological, soil science and others were used.

The forest inventory parameters were estimated by complete enumeration of trees according to their thickness levels and by cutting 6 model trees, which were selected by the proportional series representation method [165]. Model trees were sawn into 2 m sections; they were also sawn at a height of 1.3 m and at the base (stump) [165]. The following was assessed for the section cuts: diameter with bark, diameter without bark, thickness of wood growth over 5 years. Also, height and 5-year periodic height increments for branch cluster were measured in the model trees.

In Ukraine, the following components are distinguished in a tree stem within the studies of forest ecosystems bioproductivity: wood and bark; this is mainly due to a resource focus of forest taxation studies aimed to meet forestry’s practical needs. Investigating the environmental aspects of hazardous substances accumulation with different types of contamination usually requires more data on major structural elements of a forest biogeocenoses that have different patterns for the deposition of certain substances. Therefore, in similar foreign researches, a tree stem is principally divided into the following four elements: outer bark, inner bark, sapwood and heartwood (if available) [166, 161]. Such division is more applicable for studying cycling of chemicals and elements, as chemical composition of these components differs greatly, thus ensuring greater accuracy in the location of certain elements (for example, 137Cs and 90Sr radioactive isotopes).

To estimate average radionuclide concentrations, a sample from stem components should be formed from specific sampling points proportionally to a phytomass total share of in the studied component. Given that a phytomass of stem component in its air-dry state, in this case, is still an input value, there arises a need to ensure comparison and integration of the obtained results with most common databases and with methods from other authors.

To assess the aboveground phytomass of a tree stem, the method of P.I. Lakida is most often used in Ukraine; i.e. natural and basic local densities of wood and bark are estimated based on wood discs cut at

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relative heights, and further average values for these characteristics are determined for a stem based on derived regularities [159]. This method is used to assess phytomass of a tree stem and its components: wood and bark; and after modification, average concentrations of chemicals or elements (other than organogenic) in stem wood or bark can be reliably calculated. However with its high cost and high labor input into laboratory studies of concentrations of chemicals or elements in selected samples, this method loses its practical and economic efficiency, especially if detailed radial and vertical separation is not a research main objective. In such a case, it would be appropriate to use a medium sample from a tree stem component, which was formed based on its linear density value [169].

In a stand’s downstream, we identified the following components: rainwater (stem and crown) and litterfall. Characteristics of the downstream components were described though observing them during one year.

Samplers for litterfall (n = 3) and rainwater (crown (n=6) and stem (n=3)) were installed proportionally to the distribution of areas with different levels of soil surface contamination with 137Cs and 90Sr, as well as to the representation of trees in terms of their thickness levels (Figure 3.14) .

After weighing them in the field and in vacuo filtration by means of ash-free filtering paper, collected rainwater samples were further used to estimate Am137Cs and Am90Sr. Litterfall components were collected by traps (50x50 cm), and their field samples were dried at 70°C to air-dry condition. Then they were divided into four lots: needles, bark, small branches (up to 5.0 cm) and cones, buds, seeds (and their fragments). Frequency of collecting field material was scheduled with due regard for the uniformity of time intervals and with an attempt to observe calendar months.

Figure 3.14 – Layout of rainwater and litterfall samplers

Over the entire observation period (13 July 2016 – 17 September 2017), 111 samples in total were taken from the downstream components to measure Am137Cs and Am90Sr.

63 Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

Besides the studies of horizontal distribution of radionuclide concentrations in 20 cm soil layer, not least important is vertical distribution of radionuclides. This is particularly true of 90Sr; according to the previous research [167, 162] it is characterized by much higher migration to lower soil layers than 137Cs. To estimate distribution of 137Cs and 90Sr concentrations with soil depth, layered (10 cm) soil samples were taken down to the depth of 1.0 m at three "points" of the studied pine site, which had different radionuclide contamination densities.

Based on the results from the station established in a pure pine stand, its forest taxation parameters were estimated. The studied forest site grows under the forest conditions of type B3 [168]. 308 trees of Scots pine were subject to recording on the experimental site (30x30 m). Distribution of trees diameter at breast height (DBH) and selection of categories without the signs of weakening, suppression or death, are presented in Figure 3.15. The average taxation plant diameter was 14.5 cm (only for living trees), and the arithmetic mean was 13.9±4.1 cm (AM±SD).

Figure 3.15 – Distribution of tress by categories and diameters

Based on the tree universal enumeration data from the pine experimental site and after cutting 6 model trees, basic taxation parameters of the trees and stand were estimated using PERTA program; further these characteristics were used to determine bioproductivity values for forest phytocenosis. Based on the results from weighing tree crown components in the field and from their aliquots before and after drying to air-dry condition [159], as well as modified calculations to estimate phytomass of stem components [169], actual amount of biomass in model trees was presented per the chosen components (Table 3.3). Using the allometric relationship between the values of aboveground phytomass components and mortmass of the trees, as well as their DBH, a stock of biomass components for the stand was calculated (Table 3.4).

Statistical processing of data on Am90Sr measurement indicates their significant variability (Figure 3.16). The highest concentration of 90Sr is observed in averaged samples from inner bark of model trees (AM±SD: 148±40 kBq•kg-1), the lowest one - in the sapwood (AM±SD: 22.0±7.5 kBq•kg-1). The obtained data allow ranging the components of biomass in the direction of decreasing 90Sr concentrations: stem inner bark – stem outer bark – dead branches – shoots ≤1 cm (excluding 1-year) – 2-3 year needles – 1-year shoots – shoots >1 cm – 1-year needles – stem heartwood – stem sapwood.

64 Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

Figure 3.16 – Row of Am90Sr decrease in the tree stand components

65 Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

Table 3.3 – Phytomass and mortamas in model trees

Taxation Aboveground phytomass, kg parameters of Dead Stem wood Stem bark Needles Shoots ≤ 1 cm Number model trees Shoots > branches, Total 2+3 2+3 1 cm kg а DBH h m m m m m m 1-year Total 1-year Total SW HW STEM OB IB BARK year year 1 46 6.6 11.3 5.9 1.3 7.3 0.87 0.24 1.11 0.00 0.13 0.13 0.00 0.25 0.25 – 8.75 0.21 2 53 11.1 14.1 22.4 4.0 26.4 2.12 0.98 3.11 0.35 0.36 0.71 0.55 1.06 1.61 1.16 32.98 2.08 3 52 12.9 17.6 41.1 5.0 46.1 2.80 1.83 4.63 0.84 0.42 1.26 0.73 0.94 1.67 1.29 54.9 0.82 4 52 16.9 15.6 50.2 7.0 57.2 3.41 2.23 5.64 0.50 0.51 1.01 0.83 2.55 3.38 2.79 70.0 4.20 5 53 18.1 18.3 76.7 10.4 87.1 7.16 3.08 10.23 1.49 1.33 2.81 1.26 2.53 3.79 6.81 111 5.10 6 53 18.3 17.6 85.1 7.9 93.0 6.96 3.01 9.97 2.71 2.19 4.89 2.23 2.27 4.50 6.41 119 4.73

Note: mSW – sapwood phytomass; mHW – heartwood phytomass; mSTEM – stem wood phytomass; mOB – outer bark phytomass; mIB – inner bark phytomass; mBARK – stem bark phytomass.

Table 3.4 – Aboveground phytomass and mortmass of the tree stand Aboveground phytomass of the tree stand, т Stem wood Stem bark Needles Shoots ≤ 1 cm Deadwoo

Shoots d and

Parameters

> dead Total

mSW mHW mSTEM mOB mIB mBARK 1-year year branches

- 2+3

2+3 1 cm

year year

Total Total 1

On the experimental site (30x30 m: 10.72 1.33 12.05 0.85 0.44 1.29 0.221 0.158 0.379 0.264 0.357 0.621 0.813 15.15 0.64 0.09 ha) On 1 ha 119.1 14.8 133.9 9.4 4.9 14.3 2.46 1.76 4.22 2.93 3.96 6.90 9.04 168 7.1

Note: mSW – sapwood phytomass; mHW – heartwood phytomass; mSTEM – stem wood phytomass; mOB – outer bark phytomass; mIB – inner bark phytomass; mBARK – stem bark phytomass.

66 Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

The tree components ranged based on Am90Sr (Figure 3.16), do not usually demonstrate statistically significant differences with their adjacent (neighboring) components due to the overlap of confidence intervals at p = 0.95 (CI (0.95)). This explains the different order of anatomical and morphological components for 90Sr concentrations in the developed similar sequences from other authors [13, 21, 162].

All above calculations of the aboveground biomass components provide results for the inventories of radionuclide activities (90Sr and 137Cs) per a surface unit of the experimental site (1 m2), which were accumulated by aboveground components of the stand (Figure 3.17). According to the calculations, the total activity accumulated in phytomass and mortmass of the stand is approximately 613 kBq• m-2 (for 137Cs it is ≈245 kBq• m-2). The total content of 90Sr, if compared to 137Cs, differs two-fold for aboveground phytomass and mortmass of the stand.

Figure 3.17 – Accumulated activity of 90Sr and 137Cs per 1 m2 of the site, in the studied stand sectors

Analysis of Figure 15 demonstrates that total amount of 90Sr does not exceed the one of 137Cs only in the organs formed during current year (needles and shoots).

Assessment of 90Sr total amount in soil requires sampling of deeper layers, if compared to 137Cs, this is due to a faster migration of the latter in sod-podzolic soils of Ukrainian Polissia [167]. To complete this task, soil samples were taken layer-by-layer using a rotary sampler, the maximum setting depth was 1.1 m. Soil was sampled at three points at the sectors, where 20-cm samples have already been taken, and the value of radionuclide contamination density was within the following limits: AM-SD , AM, AM + SD. The range of soil in-depth sampling layers was: 0-5 cm, 5-10 cm, 10-20 cm, 20-30 cm, 40-50 cm, 50-60 cm, 60-70 cm, 70-80 cm, 80-90 cm, 90-100 cm. Samples of a general soil sample taken from a certain layer were weighted in the field, as well as soil that remained in a sampler tank. Based on the results of drying the obtained soil samples at 105°C, a sample weight was recalculated for absolutely dry condition, followed by calculation of radionuclide total activity per 1 m2 of a soil layer surface.

67 Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

The values obtained for 90Sr and 137Cs radionuclides activity per 1 m2 of the chosen soil layers are presented below (Table 3.5). With the collected experimental material, it becomes immediately clear that only 41-56% of 90Sr total activity is contained in 20-cm soil layer (and 84-92% of 137Cs).

Table 3.5 – Distribution of 90Sr and 137Cs total activity in soil Activity of 90Sr per 1 m2 Activity of 137Cs per 1 m2 Layer depth, cm Sr m % Cs m % Sampling point 1 0-5 535000 40300 46.53 2322320 92893 75.95 5-10 37200 2770 3.23 245700 24570 8.04 10-20 70500 5200 6.13 248160 24816 8.12 20-30 77300 5800 6.72 85150 8515 2.78 30-40 182000 13400 15.84 48240 4824 1.58 40-50 230000 16560 20.03 33120 3643 1.08 50-60 8790 745 0.76 49170 5408 1.61 60-70 4460 405 0.39 17550 2281 0.57 70-80 994 163 0.09 1630 326 0.05 80-90 980 140 0.09 1400 266 0.05 90-100 2408 344 0.21 5160 1032 0.17 ∑ 1150·103 – ∑ 3058·103 – 100 Sampling point 2 0-5 204400 15100 32.20 1218000 121800 53.95 5-10 61700 4600 9.72 397120 39712 17.59 10-20 88500 6800 13.94 302000 30200 13.38 20-30 81600 6300 12.85 197200 19720 8.74 30-40 48200 3700 7.59 52920 5821 2.34 40-50 61200 4600 9.64 34440 3788 1.53 50-60 71000 5500 11.18 13680 2189 0.61 60-70 5050 522 0.79 6960 1531 0.31 70-80 3060 306 0.48 6120 1530 0.27 80-90 3540 322 0.56 4830 1352 0.21 90-100 6670 606 1.05 24240 2666 1.07 ∑ 635·103 – ∑ 2258·103 – 100 Sampling point 3 0-5 52434 3780 13.07 594000 59400 42.17 5-10 40120 2992 10.00 257040 25704 18.25 10-20 72420 5396 18.05 335120 33512 23.79 20-30 28080 2160 7.00 93600 9360 6.64 30-40 32012 2416 7.98 48320 5315 3.43 40-50 47112 3473 11.74 37750 4156 2.68 50-60 68200 5115 17.00 7750 1550 0.55 60-70 32524 2595 8.11 3460 726.6 0.25 70-80 5250 1200 1.31 10500 1365 0.75 80-90 11242 924 2.80 6160 862 0.44 90-100 11850 1050 2.95 15000 2100 1.06 ∑ 401·103 – ∑ 1409·103 – 100

68 Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

For all sampling points, over 20% of 90Sr total activity in soil is at 40-60 cm depth, where a noticeable reduction in the quantity of pine tender roots is observed; this indicates reduced availability of the radionuclide with regard to its participation in metabolic processes. This phenomenon should be obligatory taken into account when forecasting 90Sr concentrations in depots and fluxes over a period exceeding 10 years, and also during the development of mathematical models of the radionuclide biogeochemical circulation. However, parametrization of the process of 90Sr migration into lower soil layers requires long-term and systematic investigations, and unfortunately they are very difficult to implement under the conditions of Ukraine.

The total activity of 90Sr per 1 m2 of soil on the pine plantation was 729±383 kBq·m2 (AM±SD), which is somewhat more than the radionuclide amount accumulated in above-ground phytomass and mortmass of the stand (≈613 kBq·m2). Contrastingly to 137Cs: 2240±825 kBq•m-2 in soil and approximately 245 kBq•m-2 in biomass of the stand.

Studying the pine stand’s downstream in the form of meteorological waters and litterfall was started on 13 July 2016. By now, the data for a period of more than one year (13 July 2016 - 12 September 2017) were obtained and allowed to calculate gross annual values for certain components of the downstream. Water and litterfall samples were taken from the installed samplers, 8 sessions in total within the mentioned period.

Data obtained from field observations of the litterfall components accumulation in trap collectors allowed preliminary estimates of their formation dynamics and components stock structure per 1 m2 -2 (ρlitterfall, kg·m ) on the studied pine plantation (Figure 3.18). Not surprisingly, intensive intake of litterfall from Scots pine trees was observed starting with the second half of summer and till November due to the increased intensity of needles fall related to the end of its vegetation season; the least was in winter season.

69 Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

Figure 3.18 – Quantity and structure of litterfall dynamics

Comparison of the mass of litterfall components’ down-streams and meteorological waters, as equivalent to 1 m2 (ρ, kg•m-2) during 13 July 2016 – 11 July 2017, demonstrates a 3-4 orders of magnitude higher amount of "liquid" share (AM±SD: 387±21 kg•m-2), if compared to the "solid" one (AM±SD: 0.145±0.032 kg•m-2) in different periods of observation; crown waters (AM±SD: 385±21 kg•m-2) make at least two orders of magnitude higher contribution than stem waters (AM±SD: 1.72±0.70 kg•m-2) of the total amount of liquid precipitation penetrating through the forest canopy.

During the entire observation period, changes of Am90Sr in down-stream components of the pine stand (Figure 3.19) were less pronounced than the ones of Am137Cs (Figure 3.20). Litterfall components (except for generative organs) were characterized by a slight variability in 90Sr concentrations during 13 July 2016 – 12 September 2017. The results from Am90Sr measurement in cone litterfall proved to be interesting: these organs belong to the most contaminated ones in forest phytocenosis as for 137Cs concentration; however, they demonstrate the lowest values for 90Sr.

70 Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

Figure 3.19 – Average values for Am90Sr in down-stream components of the studied tree stand

Strong and very tight correlative relationship (0.71-0.95 according to Spearman’s rank correlation coefficient (rs)) are observed in Am90Sr and Am137Cs values changing dynamics in crown and stem waters (Figures 17-18), which allows to state a certain synchronization of concentrations of biologically mobile radionuclides in meteorological waters. No similar dependence was established for solid fractions. The average annual concentration of 90Sr exceeds 137Cs in the crown (9.6±1.7 Bq•k-1 of 90Sr and 4.8±1.2 Bq•kg-1 of 137Cs) and stem (57±14 Bq•kg-1 of 90Sr and 42±17 Bq•kg-1 of 137Cs) waters obtained from the forest site; however these differences occasionally exceed 3 times. Sr For litterfall components, the difference of Am90 over Am137Cs is 6-8 times (excluding generative organs). Basing on the results obtained, it can be stated that 137Cs is subject to a better "washout" by meteorological waters from a tree layer than 90Sr, in case their concentrations in phytomass components are equal.

71 Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

Figure 3.20 – Dynamics of Am137Cs in metrological waters and tree litterfall

Observation data on the activities accumulated in down-stream components of the pine stand, as well as 90 137 on Am90Sr and Am137Cs in extracted fractions were used to assess the activity of Sr and Cs downward transfer to litterfall and soil from the stand, per 1 m2 of the studied plantation. Since the time of observations was longer than 1 year, annual expression of flow was calculated for 90Sr and 137Cs (conditionally, the period lasted from 13 July 2016 till 11 July 2017). Total activity of 90Sr transferred by meteorological waters and forest litter per 1 m2 of the site was 33.9±2.6 kBq, for 137Cs this value was 5.96±0.38 kBq.

Thus, basing on the initial results of studying down-stream components in the pine plantation (Table 3.6), a significantly smaller share of 90Sr transport (5.5±0.7%) by meteorological waters in gross annual activity was established, in contrast to 137Cs (16.2±1.8%); and stem water contribution (0.26% for 90Sr) can be neglected due to overlapping of the obtained total activity value with CI (0.95) of other downstream components.

Many models of plantation growth and bio-productivity were developed for major forest-forming tree species stands in the Ukrainian Polissia. The most common way to forecast future state of a plantation is to apply regression equations to the dynamics of taxation parameters in a tree stand; most often they are developed as progress tables of growth for industrial needs [170]. Biological productivity is further estimated by a method of including the forecasted taxation parameter values into static mathematical models for calculating stocks of phytomass and mortmass components in a forest biogeocenosis [171].

While selecting among a large number of regulatory and reference data used to address similar problems in Ukraine; the most successful proved to be the standards in the "Models of optimal tree stands growth and productivity" prepared by A.A. Strochynskyi, A.S. Shvydenko, P.I. Lakida [170] based on the comparison of output modeling characteristics for an experimental pine plantation with empirical data on taxation recording and analysis of tree trunks, and phytomass of pines for all elements of the phytocenosis was assessed by the regression equations from the publication "Tables and models of growth progress and productivity of plantations in major forest-forming species in Northern Eurasia" [171]. Forecasting future states of pine stands should take into account the total "excessive density" of forest cultures aged 30-70 years caused by lack of forest forming and regeneration cuts in most part of

72 Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone forests fund in ChEZ. As a result, the relative density of almost half of its medium-aged pine stands exceeds 1.0 [172], and they are often characterized by rapid and sizeable formation of litterfall.

Table 3.6 – Summary data on the year of down-streams observations (13 July 2016 – 11 July 2015)

Down-flow components

Buds,

Parameters alue Crown

V Stem water Needles Bark Branches cones, water expression seeds

Average Am137 , 12200 12800 6660 31500 Cs abs. 4.8±1.21 42±17 Bq·kg-1 ±1400 ±880 ±450 ±24009 Average Am90 , 78000 81500 81500 13100 Sr abs. 9.6±1.7 57±14 Bq·kg-1 ±4500 ±6400 ±6400 ±1000 0.257 0.079 0.066 0.013 abs. 385±21 1.72±0.70 Total mass ±0.018 ±0.005 ±0.025 ±0.006 (SUM), kg·m-2 0.066 0.020 0.017 0.003 rel. 99.4±65.4 0.44±0.18 ±0.005 ±0.001 ±0.007 ±0.002 Total activity of abs. 894±73 69±34 3150±260 1010±71 437±134 400±213 137Cs (SUM), Bq·kg-1 rel. 15.0±1.2 1.2±0.6 52.9±4.4 16.9±1.2 7.3±2.3 6.7±3.6 Total activity of abs. 1770±190 89±40 20100±1640 6440±460 5360±1950 167±102 90Sr (SUM), Bq·kg-1 rel. 5.2±0.6 0.26±0.12 59.2±4.8 19.0±1.4 15.8±5.7 0.49±0.30 Note: 1 – squared deviation (SD); abs. – absolute value; rel. – relative value, %

Generally, the studied pine forest stand can be considered normal [170, 172]. Therefore, following the correction of relative density of growth models from the above "Models of optimal tree stands growth and productivity" [170], the forest site’s taxation parameters dynamics and its bioproductivity were calculated, and the output results are presented in Table 3.7.

The data of Table 3.7 were obtained based on the assumption that the base stand height corresponds to an average height of 16.5 m at the age of 52 years; i.e. these taxation parameters correspond to field and cameral calculations for the experimental site. The dynamics of phytomass stock in the pine plantation was calculated based on initial results for the taxation parameters (A, GS, Ptotal), as well as for its quality class (SI): according to A.A. Orlov’s quality scale [171] it falls into class 2 (according to the accepted coding - 7).

Unfortunately, regulatory and reference data existing for the conditions of Ukraine do not allow to get a more detailed fractional distribution of components in aboveground phytomass of the stand: stemwood was not divided into sapwood and heartwood, stem bark was not divided into outer and inner one, needles and shoots were not divided according to their age categories.

73 Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

Table 3.7 – Estimated values of bioproductivity characteristics in the studied plantation for different ages of the pine stand

-1

- Forest total phytomass in absolutely dry state, t·ha

G, · 3

A, Htop,

·га . H, m D, cm Ptotal 2 -1 F·103 3 Vst m Tree stand fractions

GS, .,

years m m ·ha p м м

FLC

N, crown above-

stem incl. bark needles roots Total growth

TOTAL and young young and

shoots ground storey under 5 1.0 0.8 1.0 1.00 – – – – – – – – – – – – – – – 10 3.1 2.6 2.6 1.00 6.2 1364 22.1 12015 0.002 7.9 1.4 2.4 1.3 12 2.4 14.0 0.1 0.8 15 15 5.5 4.7 4.4 1.00 17.9 667 56.2 11781 0.005 20.7 3.3 5.1 2.3 28 6.1 34.2 0.2 1.1 35 20 7.7 6.8 6.2 1.00 25.9 594 104 8613 0.012 39.4 5.6 8.2 3.2 51 11.3 62.1 0.3 1.4 64 25 9.8 8.7 7.7 1.02 31.7 570 157 6727 0.023 60.3 7.9 11.1 3.8 75 17 92 0.3 1.6 94 30 11.6 10.5 9.2 1.04 36.2 557 211 5448 0.039 81.4 10.1 13.5 4.1 99 23 122 0.4 1.8 124 35 13.2 12.0 10.5 1.06 39.7 547 262 4565 0.057 102 11.9 15.5 4.3 121 29 150 0.5 2.0 153 40 14.7 13.5 11.8 1.07 42.5 539 309 3917 0.079 120 13.5 17.1 4.3 142 34 176 0.5 2.2 179 45 16.0 14.8 12.9 1.08 44.8 532 352 3412 0.103 138 14.9 18.3 4.3 161 39 200 0.6 2.4 203 50 17.3 16.0 14.1 1.08 46.5 526 391 3001 0.130 154 16.0 19.3 4.3 178 44 221 0.6 2.6 225 55 18.4 17.1 15.2 1.08 47.9 519 426 2653 0.160 169 17.0 20.0 4.2 193 48 241 0.7 2.7 244 60 19.4 18.1 16.3 1.08 48.9 514 455 2350 0.194 182 17.8 20.6 4.2 207 51 258 0.8 2.9 261 65 20.4 19.1 17.4 1.08 49.5 508 480 2081 0.231 194 18.4 20.9 4.1 219 54 272 0.8 3.1 276 70 21.3 19.9 18.6 1.06 49.9 503 500 1839 0.272 204 18.9 21.2 4.0 229 56 285 0.9 3.3 289 75 22.1 20.7 19.8 1.05 49.9 497 515 1619 0.318 213 19.2 21.2 3.9 238 57 295 1.0 3.5 300 80 22.8 21.5 21.1 1.03 49.7 492 525 1419 0.370 220 19.4 21.1 3.9 245 58 303 1.1 3.6 308 85 23.5 22.2 22.5 1.01 49.2 487 531 1237 0.429 226 19.5 21.0 3.8 251 58 309 1.1 3.9 314 90 24.1 22.8 24.0 0.98 48.4 481 531 1071 0.496 230 19.4 20.7 3.7 255 58 313 1.2 4.1 318 95 24.7 23.4 25.6 0.95 47.3 476 527 922 0.572 233 19.2 20.3 3.7 257 57 314 1.3 4.3 320 100 25.3 24.0 27.3 0.92 46.0 471 518 787 0.658 233 18.9 19.9 3.6 257 56 313 1.4 4.6 319

Note: А – age, years; Htop – top height, m; H – medium height, m; D – average diameter, m; Ptotal – relative density of all plantation components; G – cross-section area of trees at 2 3 -1 -1 3 1,3 m height per a unit of area, m ·ha; F – form factor; GS – stem stock in bark per a unit of area, m ·ha ; N – number of trees per 1 ha, pcs.·ha ; Vst – average tree volume, m ; FLC – forest live cover

74 Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

By applying the linear interpolation to the stocks of most important depots for biologically mobile radionuclides between 50 and 55 years (the age of plantation was 52 years), possible average annual absolute incremental growth of these components within the specified period was estimated. All the calculations were made for 1 m2 of the forest site. According to the product of current growth in the biomass components per Am90Sr and Am137Cs, which we accepted as probable values of increase in the amount of studied radionuclides in the phytomass components (Table 3.8).

Table 3.8 – Predicted values of annual increase of 90Sr and 137Сs activity in the components of above-ground biomass Stock Current activity increment, Current (between 2016 kBq·m-2·year-1 Biomass components increment, and 2017), kg·m- kg·m-2·year-1 90Sr 137Сs 2 outer bark 0.94 0.014 1.04 0,19 inner bark 0.49 0.006 0.89 0,40

Stem sapwood 11.91 0.060 1.32 0,58 heartwood 1.48 0.214 6.83 1,23 1-year needles 0.25 0.000 0.00 0,00 2+3 years needles 0.18 0.000 0.00 0,00 1-year shoots 0.29 0.004 0.22 0,22

Crown 2+3 years shoots (to 1 cm) 0.40 0.008 0.52 0,21 shoots >1 cm 0.90 0.000 0.00 0,00 Dry wood and dead branches 0,71 0.012 0.85 0.07 Total 17,55 0.318 11.67 2.90

Comparison of current increments in the amounts of 90Sr and 137Cs activity from Table 8 with the estimated average value conditionally for the period of 1986-2016 (formula 3.1) revealed 1.7-fold exceeding of average values over the current ones for 90Sr, and 2.7-fold – for 137Cs.

сер А Z A  , (3.1) ак  ап сер -2 -1 where Z A is an average increments in radionuclide activity amount, kBq·m ·year ; ρА is density (amount) of radionuclide in biomass components per 1 m2 of the pine site at the moment of -2 measurement, kBq·m ; aк is actual time of a parameter assessment, year; aп is a year of radionuclides release into the environment (1986), year.

Though yielded little information, the considerable exceeding for average increments in 90Sr and 137Cs activity amounts of the current ones allow to advance a hypothesis about a much higher "cumulative" ability of forest phytocenosis for these radionuclides in the past.

3.5.3 Organization of experimental sites in forest test areas to further determine redistribution of biologically mobile radionuclides in typical forest stands Assessment of actual spatial contamination of components in forest phytocoenoses of the ChEZ by biologically mobile radionuclides and their dynamics requires establishment of a monitoring sites system in the entire area covered by forest vegetation. Therefore, we decided to use circular test plots with the objective not only to develop recommendations for their organization (Table 3.9), but also to form initial operating stations in forest areas to observe the dynamics of 90Sr and 137Cs redistribution in the ecosystem components. The basic data on organized circular test plots are presented below (Table 3.9). Unfortunately, due to a large amount of field materials and laboratory analyzes (the number of soil samples only exceeded 460 pcs.), we could not perform all measurements of 137Cs and 90Sr specific activity in selected soil and plant samples. However, we plan to proceed with this kind of field and experimental effort, but outside this project.

75 Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

Table 3.9 – Key forest taxation and radiobiological characteristics of experimental sites organized as circular test plots

Am in stem Am in stem

, ,

sapwood, heartwood, m

Date of 1

- -1 -1

For dominant species Total, tree stand .0 Bq·kg Bq·kg

Plot ID sampling Rsite, E

(code) (organi- N m

µsv·h Latitude

Dominant 137 90 137 90

Longitud ADER zation) tree species Сs Sr Сs Sr D, H, A, N, G, Dtotal, Ntotal, Gtotal, cm m year pcs·ha-1 m2·ha-1 cm pcs·ha-1 m2·ha-1 Chz-2(4) 13.06.2017 51.42576 30.11134 Sb 8.92 13.6 16.2 41 2080 30.0 12.6 2680 33 3.15 2400 4500 – – Chz-3(5) 12.07.2017 51.45211 30.23415 Sp 39.9 35.6 22.3 97 290 28.9 34.0 348 32 0.70 810 2230 554 917 Chz-4(6) 12.07.2017 51.44754 30.21002 Sp 17.8 30.8 27.6 83 482 36.0 29.2 603 40 0.87 1780 2300 870 1500 Chz-5(7) 13.07.2017 51.42022 30.16364 Sp 12.6 17.3 20.3 55 1865 43.9 16.5 2205 47 1.58 4360 7780 1820 6900 Chz-6(8) 13.07.2017 51.44496 30.19738 Sp 12.6 14.1 14.3 58 2246 34.9 13.4 2566 36 0.88 2510 5440 2070 11000 Chz-7(9) 12.07.2017 51.44450 30.19842 Sp 8.9 11.6 13.4 33 3376 35.5 11.3 3657 37 0.59 925 3390 378 5230 Chz-8(10) 01.08.2017 51.35418 29.98985 Sp 12.6 17.5 12.6 27 1323 31.7 16.2 1604 33 0.65 92 920 46 780 Chz-9(11) 02.08.2017 51.43808 30.16017 Sp 17.8 19.5 18.1 41 1025 30.7 17.0 1497 34 1.30 1300 9120 1010 10074 Chz-10(12) 02.08.2017 51.43881 30.15939 Sp 17.8 14.5 12.1 35 1507 25.0 13.0 2019 27 1.39 1410 5700 503 17900 Chz-11(13) 02.08.2017 51.44349 30.14770 Sp 12.6 15.7 16.0 38 1985 38.4 15.1 2185 39 1.51 3150 9340 2500 19400 Chz-12(14) 03.08.2017 51.39896 30.20349 Sp 12.6 13.9 16.0 45 3168 48.2 13.1 3749 51 0.68 2350 3970 1430 7570 Chz-13(15) 03.08.2017 51.39948 30.20328 Sp 12.6 12.9 13.9 44 3108 40.7 12.3 3509 42 0.71 3140 5410 1590 9200 Chz-14(16) 12.07.2017 51.40747 30.19832 Sp 12.6 16.8 19.3 56 2446 54.3 15.9 2847 57 0.77 1870 2100 730 3540 Chz-15(17) 03.08.2017 51.40711 30.19995 Sp 12.6 14.9 16.6 41 2586 45.1 14.1 3048 47 0.64 1940 3140 1030 6240

Note: Sb – silver birch; Sp – Scots pine; Site ID (code) – test plot code; Rsite – radius of circular test plot; D – average diameter of tree stand; H – average height of tree stand; A – average age of tree stand; N – number of trees per a unit of area; G – cross-section area of tree stems at 1.3 m height.

76 Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

4 MAN-MADE OBJECTS. INFRASTRUCTURE FACILITIES, INCLUDING THE CHCP AND RADIOACTIVE MATERIALS LOCALIZATION SITES

Units 1, 2 and 3 of the Chornobyl NPP are at the stage of their decommissioning, and the Shelter Object is under the process of its transformation into the environmentally safe system. Spent nuclear fuel (SNF) is stored on the ChNPP site in the “Wet” Storage Facility (ISF-1). In late November 2016, the New Safe Confinement (NSC, “Arch”) was slided over the Shelter. The “Arch” is the largest-ever- built movable ground structure. It is 165 m long and 110 m high, its total weight is 36.2 thousand tons. The NSC commissioning is scheduled for late May 2018. Commissioning of a new Spent Nuclear Fuel Storage Facility (ISF-2) is scheduled for the second quarter of 2018.

Monitoring activities at the ChNPP site are performed by both responsible units of the ChNPP and by outside organizations. Parameters of the monitoring include the EDR, radionuclide concentrations in the air, groundwater, wastewater and sub-reactor water, and some others.

4.1 Comprehensive statistical analysis of landscape diversity in industrially impacted areas

After 1986 and within the ChEZ near the Chornobyl NPP industrial site, the forest plantations to the west and northwest of ChNPP Unit 4 were subjected to the severest anthropogenic impact; in the lethal zone of Scots pine, where soil top layer and dead trees were “buried” into trenches (now these are RWTLS “Red Forest” and “Naftobaza”). For more details see Figure 4.1 and Figure 4.2. Also, the ChNPP cooling pond has undergone a significant impact through its return to a natural self-regulation hydrological regime. Further, we shall discuss these objects.

Table 4.1 – Distribution of area per signature classes Item Number of pixels in topic raster, Signature class, landscape type Area, ha % No. pcs. 1. Scots pine (open-type) 2626432 36.4 16,8 2. Scots pine (closed-type) 2258801 31.3 14,5 3. Scots pine with dead tress 513703 7.1 3,3 4. Birch (grouped and scattered trees) 340772 4.7 2,2 5. Birch (young stock, natural seeding) 662663 9.2 4,2 6. Other deciduous species 403000 5.6 2,6 7. Water bodies 3799 0.1 0,0 8. Swamps and wetlands 782605 10.8 5,0 9. Meadows, sand 6450133 89.3 41,3 10. Structures, buildings, roads 1584939 21.9 10,1 TOTAL 15626847 216 100

77 Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

West trace axis of radioactive fallout выпадений

Figure 4.1 - RWTLS “Red Forest”:

The figures (Figure 4.1, Figure 4.2) demonstrate that a large number of landscapes can be identified within the RWTLS "Red Forest" and "Naftobaza"; the landscapes can be classified by means of GIS application toolkit, thus allowing estimation of current distribution between the identified signature types. The following 10 classes of signatures suitable for classification were identified through the analysis of SPOT-6 available satellite images (2014): Scots pine (open-type); Scots pine (close-type); Scots pine with dead trees; birch (grouped and scattered trees); birch (young stock, natural seeding); other deciduous species; water bodies; swamps, wetlands; meadows, sand; structures, buildings, roads. Output results of the area distribution by landscape types were obtained through classification of the images by the classical method of the smallest spectral distance (Table 4.1).

The total area within granulometric sites was 216 hectares. Graphical results of the classification of satellite image are shown in Figure 4.3. For the first three signature classes (Table 4.1), above-ground pine biomass was estimated (approximately 34.6% of the studied area), which imposes high fire hazard classes; a particular attention here should be paid to the areas with dried-up plantations of Scots pine. The data on bioproductivity characteristics from two experimental sites on rectangular test plots of Scots pine (shall be described below) were used for the calculations.

78 Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

Ось северо-западного следа радиоактивных выпадений

Figure 4.2 – RWTLS “Naftobaza”

79 Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

Figure 4.3 – Topical raster within the contours of studied areas

80 Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

Table 4.2 – Total yield of biomass on the studied sites

Stem phytomass, t Crown phytomass, t

, ,

absolute dry absolute dry t

, ,

, , t

Number of ha

, ,

signature

trees

classes Area

needles

Litterfall

bark total

total,

wood

Total, Total,

leaves crown

Dead branches Dead

branches Phytomass of ACC of ACC Phytomass 1 1905.1 307.0 2212.2 1147.1 186.1 1333.3 3545.4 422.3 918.5 36.4 2 1929.5 236.7 2166.2 964.5 363.2 1327.7 3493.9 406.0 712.0 31.3 3 – – – – – – – 678.8 – 7.1 Total, kg∙106 3.835 0.544 4.378 2.112 0.549 2.661 7.039 0.828 1.630 74.8

The total biomass of Scots pine plantations on the studied sites (phytomass + mortmass) is 9.5∙106 kg. For the details on components refer to Table 4.2.

The spatial and structural distribution of ChNPP cooling pond landscapes was assessed through the classification of the latest satellite image from Sentinel 2 sensor, which was adaptable for further processing. It was due to a necessity to get the "latest" data on spatial distribution of vegetation, which is changing dynamically in the conditions that follow the lowering of ChCP water level.

4 channels of S2B image, processing Level-1C, were used for the classification: band4 (665 nm), band3 (560 nm), band2 (490 nm) and band8 (842 nm). The survey was carried out at 9:10:09 GMT on 18 October 2017. ArcGIS 10.5 Interactive Classification and Training tool was used for the classification thus speeding up raster(s) processing by the Maximum Likelihood Classification method [173]. 7 signature types were identified and classified within the cooling pond’s water surface prior to the water discharge, inclusive of additional 10-25 m buffer around the surface perimeter. The structure of landscape-type areal distribution, which is based on the results of classification, is presented below (Table 4.3). Graphical interpretation of the initial topical raster is shown in Figure 4.4.

Table 4.3 – Landscape-type areal distribution of the ChNPP cooling pond, as of 18 October 2017 Item Description of landscape type Area, ha % No. 1. Water 879 36.5 2. Sand 768 31.9 3. Pine stands 9 0.4 4. Meadow 170 7.1 5. Dry cane 34 1.4 6. Deciduous trees and shrubs 237 9.8 7. Wetland vegetation 312 13.0 TOTAL 2409 100

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Figure 4.4 – Results of input images classification from Sentinel-2 satellite image

4.2 Approbation of radioecological monitoring in the ChEZ ecosystems subjected to severe anthropogenic impacts

One rectangular test plot was organized at the RWTLS “Red Forest” and another one was established at the RWTLS “Naftobaza”. The test plots were organized on the axes of radioactive fallouts, in the forest cultures of Scots pine, which were created in the earlier plantations’ lethal damage zone. Organization of the plots complied with the previously described requirements for experimental sites in forest ecosystems. Taxation characteristics of the studied forest plots are presented below (Table 4.4).

Phytomass components of woody plants sampled from experimental site ChZ-0/1RF at RWTLS “Red Forest” are characterized by extremely high levels of radionuclide contamination: 137Cs (35-280 kBq•kg-1 in pine, 24-450 kBq•kg-1 in birch) and 90Sr (485-5000 kBq•kg-1 in pine, 1100-6800 kBq•kg-1 in birch). At the site located at the RWTLS "Naftobaza", the specific activities of Cs and Sr radioisotopes were an order less.

82 Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

Table 4.4 – Data on test sites (TP) Stand Trees with Forest TP code Average for species Density Stock composition assessed quality coordinates phytomass Trees, in Area, ha dia- without age, height, pcs.∙ha-1 absolute, bark, species % meter, relative bark, TLU years m m2∙ha-1 m3 ∙ cm m3∙ha-1 ha-1 1 (Red Sp 98 28 11.9 8.1 1724 19.16 0.66 92.7 73.6 Forest) Chz-0/1RF ІІІ 0,1125 Sb 2 6 24 8.4 7.6 89 0.49 0.03 2.2 1.8 51°23'14.1"N 30°04'14.6"E А3 Total 100 28 11.7 8.1 1813 19.65 0.69 94.9 75.4 2 (Naftobaza) Sp 100 25 14.6 12.2 1600 26.96 0.73 166.3 139.6 Ia Chz-0/2NB 0,06 3 51°24'21.2"N 30°05'23.3"E Total 100 25 14.6 12.2 1600 26.96 0.73 166.3 139.6 B2

A large share of meadow landscapes (over 40%) in the territory of RWTLS “Red Forest” and RWTLS "Naftobaza" indicates that their monitoring should be focused particularly on open plant phytocenoses. Now, we know that a team from the Lancaster Center for Ecology and Hydrology (Lancaster, UK), directed by Nick Beresford, is organizing a system of stationary experimental sites for a long-term study of radioecological significance of grassy vegetation. The sites shall be placed along western and north-western "traces" of radioactive fallout.

An increased number of sites for studying forest ecosystems at the RWTLS "Red Forest", or RWTLS "Naftobaza", or ChNPP cooling pond would surely expand the experimental base from observations, but currently there is no urgent need.

At present, main focus should be directed to the ChNPP cooling pond’s succession processes, which were caused by its lower water level and decreased area of water surface. If we take into account the facts that the cooling pond’s area is approximately 2.4 thousand ha (10 times more than the ones of the RWTLSs "Red Forest" and "Naftobaza" taken together) and that it can be populated with herbaceous and woody vegetation very quickly due to "pioneer" species. Under such conditions, extremely high radionuclide concentrations can be found in plant biomass in 5 years. Therefore, now we recommend establishment of experimental sites right at the ponds’ bottom deposits, after their drainage at different groundwater levels; this is due to the determinative impact of groundwater depth on the bioproductivity of future phytocenoses.

4.3 Monitoring of the RWTLS effects for surrounding ecosystems (by the example of a pilot site at trench No.22 in the “Red Forest”)

24 RWTLS were identified in the ChEZ with the total amount of burials of 1.1·106 m3 and the total activity of 1.4·1016 Bq [174]. RWTLS consist of trenches and above-ground pits that were constructed without damp proofing. There are approximately 800 of such structures in total and they mostly localize high-level topsoil, contaminated wood and residential building elements. Radionuclide

83 Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

compositions of the localized RAW is currently defined by the nuclides of caesium 137Cs, strontium 90Sr and TUE.

When groundwater level increases, some RWTLS are flooded. This intensifies chemical and biochemical processes, reduces stability of the nuclear fuel matrix and accelerates transfers of radionuclides to mobile forms. Currently, radioactivity of the groundwater at RWTLS is mostly determined by strontium 90Sr. At the distances of several tens of meters from the trench, concentration of strontium 90Sr in the groundwater exceeds concentrations allowable for people thousands of times, while the specific activity of mobile forms of caesium 137Cs and TUE is much lower and transport of these nuclides outside the trench is practically not observed

The problem of RWTLS has got a special attention in the approved Concept of activity in the ChEZ [175]. According to the Concept, an optimal set of measures to minimize hazards from the RWDS and RWTLS should be developed. Therefore during the development of a RAW management strategy, attention should be given to the problem of radionuclides biogenic transport to soil surface, along with the problem of strontium 90Sr transport with groundwater. Many RWTLS are overgrown with herbaceous, shrubby and woody vegetation now. Root systems of these plants are found mainly in the high-level soil layer enriched with mineral nutrition components. Plants accumulate radionuclides very intensively (particularly, strontium 90Sr). As a result, specific activity of biomass of these plants amounts to units of MBq/kg and it is classified as medium-level waste, which may require re-disposal in future. For example, the current specific activity of plants in the “Red Forest” exceeds the one of disposed trees, and the density of -particles flux from vegetation is 10 times higher than that from the soil surface.

4.3.1 Characterization of еру experimental site At the time of the accident, the “Red Forest” area was covered with pine forests of various ages, a large part were forest cultures aged between 15 and 40 years. In May 1986, the total amount of woodlot was up to 50-53 thousand m3. During the accident, exposure dose of the ChNPP-adjacent forest was 80-100 Gy. As a result, all pine plantations died there. The trees and litter turned into radiation sources. Also, risk of fire increased due to the vegetation death. For these reasons, all the woodlot and high-level topsoil were cut completely and disposed in the trench. The whole of vacated land was covered with a layer of river sand. In such a manner, the existing vegetation cover was completely destroyed and general environmental conditions were changed.

Rye was sown and perennial grasses were oversown there. However, those species were poorly adapted to the prevailing conditions and mostly died in the following year. Therefore, an artificial forest was planted there pursuant to the "Interim recommendations for the performance of forest management activities in the dead forests of ChNPP resettlement zone". Saplings of Scots pine, birch and red oak were used for the afforestation. To form the undergrowth, shrubs of viburnum-leaved ninebark and white swida were introduced between the rows [176]. Since the site was affected by many factors, its state and structure of vegetation cover vary greatly now. Despite the same age of plantations, the biomass of trees and shrubs varies greatly depending on a habitat. This is explained by the fact that the RWTLS area has undergone significant man-caused impacts (destruction of the pre-accident vegetation cover, removal of fertile topsoil, construction of disposal trenches for the contaminated soil and vegetation, area coverage with river sand, treatment of

84 Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

surface with chemical solutions for dust suppression), which created very specific local conditions for the vegetation growth there.

In terms of its morphological characteristics, the planted vegetation at the RWTLS "Red Forest" (the discussed site is area of trench No.22) belongs to single-tier plantations; composition of the stand includes 80% of pine and 20% of birch. The stand was formed by artificial planting of saplings. Current age of the plantations is 30 years. Before the fire of 2016, the plantation density was approximately 1,500 trees per a hectare. The average density of plantations in trench No.22 area was as follows: 0.11 trees/m2 of pine and 0.033 trees/m2 of birch.

Trench No.22 was chosen as a radioecological monitoring object at the RWTLS "Red Forest". This disposal site is a rectangular trench. It is approximately 70 m long and 8-10 m wide, its depth is 2-2.5 m (Figure 4.5). The initial source of radionuclide migrations into the environment was a heterogeneous mixture of contaminated organic matter and soil including micron-sized fuel particles. Geological cross-section of the site consists of a sequence of sediment layers of quaternary eolian and alluvial sands and sandy loam layers. The depth to groundwater on the experimental site is 2-3 m. The infinite sandy leaky aquifer is limited by a low-permeable layer of Eocene marl at a depth of 30 m. During the 30 years after the trench filling, radionuclides were washed out by meteoric water (average annual precipitation is 550-650 mm) and penetrating into lower unsaturated soil and aquifer. As a result, in 2000 the concentration of strontium 90Sr in groundwater of the top aquifer ranged within n∙100 and n∙10,000 Bq/l around the trench, and the plume of radiostrontium has spread 10 m downstream from the source [177].

4.3.2 Radioactive contamination of soil cover As demonstrated by the studies, contamination of the topsoil (root layer) in the RWTLS "Red Forest" area is very uneven, both in terms of activity vertical distribution and in terms of absolute values. The reason is an incomplete removal of contaminated soil layer and the uneven "backfilling" layer in the trenches during the RWTLS construction.

Radioactive contamination of the soil profile has a random pattern both outside the trench and in its body, which is related more to the artificial penetration of radionuclides (up to 3 m) than to natural migration processes (Figure 4.6). Basing on the available information, studies of radionuclide vertical distributions in the site soil profile without taking account of the physicochemical forms of soil makes no sense.

85 Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

Figure 4.5 – Location of the experimental site at the RWTLS "Red Forest" (Trench No.22)

Such conditions significantly complicate the possibility to forecast contamination of the vegetation, since the overwhelming number of coefficients of radionuclide transfer from soil to plants were obtained for the natural biocenoses, which radioactive contamination was mostly in 10-20 cm topsoil layer. When studying the contamination of RWTLS area with artificial deepening of radionuclides, the concept of regarding transition coefficient as a relationship between radionuclide concentrations in a plant and density of radioactive contamination in a unit of land area is meaningless.

The URIAR carried out studies to assess the radionuclides inventory in trench No.22 (approximately 200 soil samples from the trench body were analyzed). The studies demonstrated that in 2000 the trench contained 600240 GBq of caesium 137Cs, 290120 GBq of strontium 90Sr, 41.6 GBq of europium 154Eu [178]. Application of actual relationship between the radionuclides in the trench (at the moment of sampling) and in fuel particles (at the start time) allowed estimation of the amount of radiostrontium that has gone beyond the trench due to vertical and horizontal migration processes. As of 2000, this value was 75% of its original concentration.

86 Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

A, кБк/кг A, кБк/кг 1 10 100 1000 1 10 100 1000 0 0 30 30 60 60 90 Cs-137 90 Cs-137

120 Sr-90 Sr-90 см 150 см 120

180 150

210

Глибина, 180 Глибина, 240 210 270 240 300 270 330

360 300

a b

A, кБк/кг A, кБк/кг 0.01 0.1 1 10 100 1000 0.01 0.1 1 10 100 1000 0 0

30 30 Cs-137 Cs-137 60 Sr-90 60 Sr-90

90 90

120 120

150 150

180 180

Глибина, см Глибина, см Глибина, 210 210

240 240

270 270

300 300

c d Figure 4.6 – Vertical distribution of radionuclides in the west part of trench No.22 (a, b) and outside its borders (c, d) in 2001

4.3.3 Physicochemical characteristics of radioactive waste It has been established that the initial relationship of physicochemical forms of radionuclides in the radioactive waste was as follows: 50% of radiocaesium were in condensed form, 50% of radiocaesium and 100% of radiostrontium and TUE were in fuel particles. Dissolution rates of the fuel particles were of the three types [179]: • U-Zr-O – highly stable, insoluble under natural conditions particles (2010% of activity, -1 the transformation constant was k0 = 0 year );

87 Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

• UO2 – particles of the dispersed nuclear fuel (6010% of activity, the transformation -1 constant was k1 = 0.029 year ); • UO2 + x – particles of oxidized nuclear fuel (2010% of activity, the transformation constant -1 was k2 = 0.43 year ).

In 2000, approximately 40% of strontium 90Sr activity (from the particles that could dissolve in natural conditions) in the material of the trench backfilling were in the matrix of fuel particles.

In 2015-2016, the URIAR jointly with IRSN (France) carried out monitoring to verify the above values. With due regard for the assessments uncertainty, the obtained results confirmed correctness of the accepted model. Now, approximately 20% of the radioactive waste activity is in the form of insoluble uranium-zirconium particles. They are biologically inaccessible and produce practically no impact on the environment (except for external irradiation of biota in the unsaturated zone).

4.3.4 Radioactive contamination of vegetation Studies of radioactive contamination at the experimental site have demonstrated a rather high spatial heterogeneity in radioactivity content in the topsoil. Nonetheless, some reference trees were selected in different parts of the experimental site and the sampling list covered almost all vegetation components. In 2001, basic components of the trees were sampled in a dynamic perspective in order to obtain more reliable results.

The results obtained demonstrated the following: • Specific activity of caesium 137Cs in the needles decreases as their age increases. Maximum concentrations of this radionuclide were observed in young needles in early growing season; • Specific activity of caesium 137Cs in the birch leaves also tends to decrease as with the increased age of organs, but this trend is less pronounced due to a shorter growth period of the leaves, if compared to the needles; • Specific activity of radiostrontium in the needles tends to increase as its age increases. The same can be applied to the birch leaves.

The dynamics of radionuclide intake by pine and birch components can be explained by their chemical counterparts’ arrival dynamics [180]; i.e. potassium for radiocaesium and calcium for radiostrontium. Both calcium and potassium are required elements of mineral nutrition of plants that ensure their normal development and growth.

The obtained data demonstrated rather high values of radionuclide contamination for the plant components on the "Red Forest" experimental site. Generally, specific activity of radiostrontium in the tree components growing at the trench several times exceeds the one of the trees growing outside it. Naturally, the differences would be much larger if the trees would stay under the same mineral nutrition conditions, but the ‘outside’ trees are growing on almost pure sand depleted of mineral nutrition elements. Under such conditions, the radionuclide transfer coefficients prove rather high. The ‘trench’ trees stay in different conditions; there is a relatively enriched mineral soil layer under the man-made sand layer (trench filling material). It is natural that root system of the ‘trench’ trees is developing towards increased accumulation of mineral elements and they partially get nutrition from the trench soil.

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Specific activity of radioactive waste in the trench is very heterogeneous and sometimes it can be lower than the one of soil outside the localization site (intact soil layer in the RWTLS construction). Obviously that radioactivity in the tree components growing on the latter plots proves to be higher than that of the ‘trench’ trees. This will be particularly notable for radiocaesium, since it is far less mobile in soil than radiostrontium. A large part of radiostrontium has moved to lower layers of soil horizon due to the vertical migration processes; and the contamination source (20-60 cm layer of contaminated soil, which was left in some places outside the trenches) is significantly depleted of radiostrontium. This explains absence of significant discrepancies in radiocaesium contamination of pine components growing outside the trench and at it.

4.3.5 Radiobiological effects of chronic exposure A comprehensive study of pines was carried out to determine the effects of chronic internal and external exposure of terrestrial ecosystems components within the ChEZ [204]. The research program covered over 1,100 young trees ( >20 years), which were selected from the sites with different levels of radioactive contamination. The sampling included pine plantations of the RWTLS "Red Forest". Those pines were planted after the Chornobyl accident in 1986, mostly to prevent secondary transport of radionuclides and erosion of soil. For every tree, main morphological parameters and radioactive contamination values were determined. Cytologic analyzes were made selectively, basing on the exposure doses range. The results obtained demonstrated a clear dependence of the frequency of morphological changes on exposure dose rates, thus allowing an unambiguous identification of radiation factor as a cause of the above changes.

For the same purpose, asymmetries of birch leaves and pine needles were studied in the ChEZ in 2016. The research was carried out for a wide range of external and internal exposure doses of the organisms. The "Red Forest" area was used as an experimental site. The results obtained demonstrated that the values of fluctuating asymmetry do not depend on external and internal exposure dose rates both for the birch leaves and for the pairs of Scots pine needles.

4.3.6 Lateral migration of radionuclides with groundwater flow Safety of radioactive waste storage facilities or of nuclear facilities is related to their ability to confine radioactivity and isolate it from the biosphere. The most probable process that can cause radioactivity releases from underground storage facilities is migration of radionuclides with groundwater. Several studies have demonstrated that transuranium nuclides can migrate in aquifers up to several kilometers from their underground nuclear sources [181, 182, 183, 184, 185, 186, 187]. All these studies confirmed existence of higher plutonium concentrations in aquifers at different distances downwards, in the direction of groundwater movement from the sources (up to several kilometers). Some data suggest that colloidal transfer of Pu is not the main process [185, 186]. Alternatively, other results confirm that the colloidal transport is the main process causing migration of plutonium isotopes in aquifer to sufficiently large distances [182, 183, 184, 187]. Presumably, the conflicting observations can be explained by differences both in their experimental logs and specific conditions of the migration. Despite these studies, our knowledge is still limited as for correct forecasting of Pu behavior in aquifers. The study’s objective was to improve our understanding of plutonium transport in shallow aquifer.

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Figure 4.7 – Cross section of strontium 90Sr spatial distribution in the experimental site saturated zone in June 2002. The line of hydrologic section is A-R [201]

Migrations of radionuclides from the near-surface radwaste temporary disposals with the groundwater flow are a mechanism of their redistribution in the environment. The RWTLS groundwater is covered by the system of routine radiation monitoring in the ChEZ. However, it is difficult to use these data for a long-term prediction of radionuclide transport with groundwater. Precision scientific monitoring is required to populate the migration models with parameters and to further validate them. A scientific site in the "Red Forest" is an ideal area for such monitoring. The area adjacent to trench No.22 has a network of wells, and their location allows assessing spatial distribution of radionuclides in water- saturated horizon in dynamic perspective. Moreover, as mentioned above, the radionuclide source function is quite well described. Lateral migration of the radionuclides has been studied since the 1990s. The studies proved presence of radionuclide radioactive contamination in the aquifer system of Quaternary deposits. The major contaminating agent is strontium 90Sr. The activity concentrations of caesium 137Cs and other radionuclides, including transuranium ones, are much lower (orders of magnitude) due to physicochemical properties of these chemical elements.

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Figure 4.8 – Cross-section of spatial distribution of plutonium isotopes in saturated zone of the experimental site in 2005 [41]

The experimental efforts, which were carried out in 2001, allowed estimation of the total removal of strontium 90Sr to aquifer; the value amounted to 2-7% of its initial concentration in the trench [201]. The plume of strontium 90Sr in the aquifer (with the concentrations of ~1000-2000 Bq/l) stretches approximately 10 m from the trench along the groundwater travel direction (Figure 4.7). Maximum concentrations of strontium 90Sr activity inside the plume are comparable to those in soil solution inside the trench. The background activity in top aquifer is the order of nx100 Bq/l and is due to the radionuclide’s vertical migration into unsaturated zone from the "artificial" layer that contains residual contamination. Results of tracer experiments allowed estimation of actual velocity of the groundwater ~ 11 m/year. Assuming that this value is unchanged, migration rate of strontium 90Sr in aeolian layer may be estimated as amounting to ~9% of the groundwater velocity.

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The works that were completed on the experimental site also demonstrated presence of mobile chemical forms of plutonium and their possible transport in top aquifer for tens of meters from the source within a fairly short period of time (Figure 4.8). Resulting spatial distribution of plutonium in the aquifer reflects orientation of the hydraulic gradient. Based on radionuclide relationship in the source and in the saturated zone, it was demonstrated that plutonium in the aquifer has mostly migrated from the trench.

A due consideration should be given to studying the migration of long-lived isotopes of plutonium, chlorine 36Cl and technetium 99Tc, as they may pose potential hazards to humans in the distant future due to their long decay time.

4.3.6.1 Concentrations of uranium isotopes and transuranium elements in saturated zone in 2017 The experimental effort to get updates on the spatial distribution of uranium, plutonium and americium isotopes in saturated zone of the experimental site was continued in 2017. The groundwater was sampled from the wells along 'WS' profile (Figure 4.5). Prior to sampling, each well was pumped with a water production that equaled to a well five-fold water volume (in this case, approximately 3 liters). The system for water sampling included a sealed glass container, vacuum pump, connection hoses and filter. During sampling, the samples were filtered through cotton cartridges (0.5 μm pore size, Westdale Filters Limited, UK). A sample volume was approximately 20 liters. During sampling, the water flow rate varied between 0.15 and 0.3 l·min-1. Since transportation of those large samples to laboratory was inefficient, the pre-concentration of radionuclides was carried out in the field. During sampling, tracers of studied radionuclides (232U, 243Am, 242Pu), concentrated nitric acid (0.6 ml per a liter of sample), and Fe3+ solution in the amount of 50 mg per a liter of sample were introduced into the vessel with filtered material. Then, a sample rested for several hours after sampling to come to the solution equilibrium, further the solution’s pH was increased to 8-9 by adding coalless ammonia to the sample, then sedimentation of ferrous hydroxide was performed. Together with ferrum, isotopes of uranium and transuranium elements were co- deposited. The sample was left to set overnight. After that, solution above the precipitate was carefully decanted, and suspension of ferrous hydroxides (approximately 1 liter) was transported to laboratory for the radiochemical separation of radionuclides. Americium, plutonium and uranium were distilled using Eichrom TRU and UTEVA resins with further alpha-spectrometric measurements. This analysis was based on ACW03 procedure (Eichrom Technologies, Inc.), with some changes. Hydroxides of high-valence elements were dissolved in nitric acid. Co-deposition with calcium phosphate was used to concentrate and isolate actinides from a sample. Tracers were used to determine chemical yield and correct results in order to improve accuracy and correctness of results. This procedure is a fast and reproducible method for activity measurements. Results of the analysis are presented below (Table 4.5). Unfortunately, we failed to take samples from some smallest wells in the profile; this was due to groundwater level fluctuations on the experimental site. 238U activity concentrations fluctuated in the range of 0.2-1.8 mBq kg-1. The maximum values were observed in wells 1-06-1 and 1-06-2, which were organized in the upper alluvial horizon of saturated zone. In the rest of samples, this radionuclide’s activity concentrations did not exceed 1 mBq kg-1. Uranium isotope concentrations in groundwater of layers with normal scattered content of radioactive elements had the order of n•100 - n•10-1 μg/l [188]. In absolute magnitude, uranium concentration in the experimental site’s groundwater was close to clarke one. It is known that activity

92 Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

concentrations of natural 238U and 234U are approximately equal in equilibrium state. In our results, the ratio of 234U/238U activities varied between 1.0 and 1.5. A distorted natural ratio of activities for these uranium isotopes in some samples may result from the impacts of burnable uranium. Such a distortion of isotopic ratio was observed in the accident’s “near zone”, both for soils [189] and for groundwater sampled from the Chornobyl NPP industrial site [190]. Concentrations of 241Am in groundwater samples were quite low and varied in the range of 0.4 - 4.5 mBq kg-1 (Table 4.5). Therewith, the obtained results showed that migration mobility of this radionuclide was lower in eolian layer, as compared to the underlying alluvial layer (marked in gray in the table). Isotopes of plutonium demonstrated a reverse pattern. Their mobility was higher in the aeolian layer. As of 2017, basing on average concentrations of radionuclides in the fuel, 239,240Pu/241Am activity ratio was approximately 0.5. It is generally known that americium is more mobile in the environment as compared to plutonium. In this case, the activity ratio for these radionuclides in groundwater should be under average for fuel (0.5). However, the results obtained demonstrate that the average value of 239,240Pu/241Am activity ratio was 3.8 in the water samples taken from top saturated zone (eolian deposits). This means that plutonium (some of its forms) was much more mobile than americium under those conditions. At the same time, the average ratio of 239,240Pu/241Am in the water samples taken from alluvial layer was 0.4, which is very close to the fuel mean. Mobility of americium and plutonium were approximately equal in that layer. Therefore, the results obtained confirm presence of a mobile fraction of plutonium, which migrates relatively quickly due to the lateral migration with groundwater flow, mostly in top part of saturated zone (eolian layer).

93 Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

Table 4.5 – Activity concentrations (mBq kg-1) of radionuclides 241Am, 239,240Pu, 238Pu, 234U and 238U in groundwater (WS profile, trench No.22)

No. of Sample Altitude, m 241Am Δ 239,240Pu Δ 238Pu Δ 234U Δ 238U Δ well size, L 1-06-1 20 111.08 0.83 0.08 0.86 0.11 0.32 0.05 2.29 0.21 1.60 0.15 1-06-2 20 109.59 0.66 0.10 0.37 0.08 0.12 0.04 2.59 0.32 1.82 0.24 2-06-1 20 108.31 0.42 0.05 0.21 0.04 0.08 0.02 0.59 0.07 0.37 0.05 2-06-2 20 106.83 1.35 0.14 0.79 0.13 0.41 0.11 0.80 0.10 0.62 0.08 11-02-1 20 108.2 3.32 0.32 0.30 0.05 0.13 0.02 0.24 0.04 0.22 0.03 11-02-2 20 106.7 4.50 0.32 1.72 0.21 0.74 0.10 0.31 0.05 0.29 0.05 12-02-2 20 109.7 0.63 0.14 2.51 0.39 0.97 0.18 0.28 0.03 0.29 0.03 4-02-2 20 109.7 1.02 0.09 12.17 1.85 5.14 0.83 0.35 0.05 0.34 0.05 3-02-1 20 108.2 1.21 0.16 0.42 0.07 0.24 0.05 0.50 0.07 0.44 0.06 3-02-2 20 106.7 1.79 0.24 0.61 0.09 0.31 0.05 0.92 0.11 0.77 0.09 10-02-2 18 109.7 0.70 0.15 1.43 0.26 0.56 0.14 0.48 0.08 0.38 0.07 9-02-1 20 108.2 0.60 0.09 0.27 0.04 0.14 0.03 0.16 0.04 0.15 0.04 9-02-2 20 106.7 1.71 0.20 0.51 0.07 0.27 0.05 0.34 0.05 0.33 0.05 4-00 20 109.5 1.04 0.10 3.58 0.46 1.47 0.21 0.29 0.04 0.19 0.03

94 Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

4.3.7 Impact of biogenic transport of radionuclides on their redistribution in topsoil Throughout their life, forest timber species are permanently and continuously replenishing forests with fallen organic matter. This is the way how they impact condition of soil surface and soil layers. Forest litter is formed from fallen leaves, needles, buds, seeds, branches, pieces of bark, dying living ground cover and other components. Litter impacts water and thermal conditions of soil. Fallen organic layer (litterfall) is an important component of the biological cycle of matter in a forest-soil system. Annual amounts of litterfall materials depend on soil fertility; composition, shape and yield class of a plantation; age, thickness, origin and crown density of forest plantations; in pine forests it usually amounts to 3 tons/ha-1 [191]. Forest litter is subject to destructive and chemical changes. The destructive changes include destruction of litter’s standard structure caused by mechanical impacts of wind, precipitations, various fauna and micro-flora species. The chemical changes occur under the impacts of enzymes, microorganisms, animals and contribute to humification of litter and formation of humus. The humification is a complex process caused by decomposition of initial litter components by soil mesofauna and microorganisms into simple compounds (partially into complete mineralization products), it also results from synthesis of organic compounds and formation of humic matter. During a growth period in stands, a fixed amount of its components repeatedly participates in the cycle: soil → tree → fallen leaves → forest litter → soil. Due to the circulation, nutrients accumulate in a topsoil and its natural fertility continuously increases, thus positively affecting the development of shrub and grass vegetation. Radionuclides of caesium 137Cs and strontium 90Sr are chemical analogues of potassium and calcium, i.e. of the elements that play an important role in plant mineral nutrition. Therefore, coefficients of their accumulation in forest vegetation are of significant values. Radionuclides return to soil as a part of litterfall. During the litter decay, the radionuclides that were present in the litter participate in migration processes together with organic and inorganic compounds. To study the effects of biogenic transport of radioactivity in terms of radionuclide redistributions in topsoil, scientists from the URIAR carried out a layer-by-layer sampling of soil (with a 2-cm increment) under the crowns and outside them. The samples were taken at trench No.22 surface. The results obtained demonstrated that concentrations of exchangeable radiostrontium (available for plant uptake) in the topsoil under crowns were much higher than that in the open areas (Figure 3.14). Radionuclides that are released from the litter are repeatedly involved into the migration processes. Some of them are absorbed by plant roots and some are redistributed in soil profile due to vertical migration processes. Radiostrontium is particularly mobile within this system.

This is how the vegetation growing on the trenches transports biologically available radionuclides to the surface; and radionuclides are mostly deposited in different plant organs. This results in a formation of radionuclide source, which may be redistributed in the environment during a fire. Radioactivity transport during a fire can cause additional exposure of both personnel and public outside the ChEZ.

To estimate the values of biogenic removal of caesium 137Cs and strontium 90Sr, in 2005 the URIAR and IRSN (France) jointly carried out a series of studies on radionuclide fluxes in the experimental site’s forest ecosystem. It was demonstrated that plantations of the Scots pine (Pinus sylvestris L.) on the waste disposal site produce a significant impact on long-term redistribution of the radioactivity contained in the trenches. After 15 years of its growth, the above-ground biomass of an average tree growing at trench No.22 has accumulated 1.7 times more caesium 137Cs and 5.4 times more strontium 90Sr than the trees growing outside the trench. Simulation of radionuclide fluxes demonstrated that the trees can annually extract up to 0.82% of the trench’s strontium 90Sr inventory and 0.0038% of caesium 137Cs inventory. The long-term 95

Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone forecast demonstrated that maximum removal of strontium 90Sr can occur within 40 years after planting. As a result, 12% of this radionuclide inventory in the trench shall be transported with biomass turnover to the soil cover surface and 7% shall be contained in the tree biomass [192].

Activity, kBq/kg Activity, kBq/kg Activity, kBq/kg 0.1 1 10 1 10 0.1 1 10 100

0-- 0-- 0--2 2 2 Sr fix. 2-- 2-- 2--4 Sr exch. 4 4 4-- 4-- 4--6 6 6

6-- 6-- 6--8

8 8 8--10 8-- cm

cm 8--

, , Sr fix. , 10 10 10-- 10-- 10--12

Sr exch.

Depth Depth 12 Depth 12 12-- 12-- 12--14 14 14 14-16 14- 14 - 16 16 Sr fix. 16-18 16- 16- Sr exch. 18 18 18-20 18- 18- 20 20

c) a) b) Figure 4.9 – Vertical distribution of fixed and mobile forms of strontium 90Sr activity in the topsoil surface on trench No. 22 at the RWTLS "Red Forest" (1999): a) under the birch crown; b) under the pine crown; c) outside the tree leaf and needle litterfall

4.3.8 Monitoring of 36Cl concentrations in the groundwater of RWTLS "Red Forest"

High solubility of chloride natural compounds and its geochemical inertness (chloride is not sorbed, not digested by microorganisms, does not oxidize, and is not restored) cause its excellent migration characteristics and ability to accumulate in deep groundwater. Its movement front in groundwater is consistent with movement front of solvent itself; therefore its distribution in groundwater may be predicted by using the transport models that disregard interactions of substances with rocks and other possible changes in element concentrations with changing parameters of hydrochemical systems. Accordingly, chloride may be considered as a possible tracer for estimating the maximum spread of radionuclides from the trench. For this purpose, 36Cl radioactive isotope, which was present in the Chornobyl accident fallout, is particularly suitable. This is a very long-lived radionuclide (its half-life is 3.01∙105 ± 0.04∙105 years), and its decomposition over the period of time after the accident may be ignored. For this reason, international researches for studying the spatial distribution of 36Cl in groundwater of saturated zone in the experimental site and determining its possible sources were conducted on the experimental site near trench No.22 of the RWTLS "Red Forest" in 2008-2011. The research results, which were obtained by means of the most advanced methods of research, demonstrated that nowadays trench No.22 is a source of groundwater contamination with this radionuclide [193]. The research results demonstrated that 36Cl/Cl isotope ratio values, which were measured in the groundwater, in a soil solution from the trench body and in birch leaves extracts, were 1-5 orders of magnitude higher than 36Cl/Cl theoretical natural ratio. This contamination occurred after the Chornobyl explosion and also exists nowadays. Although it is obvious that the trench is currently a point source of 36Cl, but other sources should be also involved in order to explain the obtained values. The groundwater 36Cl contamination values can be explained by the dilution of 96

Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone trench groundwater with uncontaminated water (rainwater or deep groundwater). The obtained 36Cl/Cl atomic ratio is 1-4 orders of magnitude higher in the groundwater than the theoretical natural ratio. 36Cl activity concentrations in water samples varied within a fairly wide range, i.e. between the units of mBq l-1 and 1 μBq l-1.

In this paper we assume that other trenches and/or soil surface may be additional sources of 36Cl in the groundwater contributing to the total contamination (especially in the wells located upstream the groundwater).

Main conclusion of this effort is that 36Cl can be a good indicator for radionuclides lateral migration from the trench through groundwater current. However, 36Cl migration from the trench to groundwater is not as simple as it seems, and the maximum length of its plume can be investigated only with the availability of additional wells. This difficulty is explained by the presence of 36Cl additional sources in the groundwater.

4.3.9 Impact of fires on the mobility of radionuclide migration in soil cover

As a result of fire in the area of RWTLS in 2016, most of its vegetation was destroyed, including its tree vegetation (Figure 4.10). Quasi-equilibrium of ecosystem in this affected area was disturbed; flows of substance between the ecosystem elements were disturbed too, including the radionuclide fluxes. As it was shown before (refer to paragraph 4.1.3.8), annual removal of 137Cs and 90Sr radionuclides to surface by tree vegetation can reach up to 0.004% and 0.8%, respectively. Since vegetation has died as a result of fire, the radionuclide circulation was interrupted. In this case, we should expect a change in migration mobility of 137Cs and 90Sr in the top soil layer. To study this problem, an experiment was started in September 2017 to investigate the dynamics of radionuclides mobility in the top soil horizon of burned area. Samples of litter and 0-5 cm soil horizon were taken from a foxed plot using a cylindrical sampler, 150 mm in diameter. To compare the effects of fire for radionuclides mobility, there should be available reference plots with soil and vegetation conditions that are similar to the burnt area. It was not difficult to select such plots, since the front line of fire spread was not uninterrupted and there were some unburned plots with vegetation within the burned area. Consequently, reference samples were taken there. The distance between samples in the burned area and outside it did not exceed 10 m. There were three sampling sessions in total.

Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

Figure 4.10 – Monitoring network for radionuclides bioavailability after a fire in ChEZ in 2016

Since the fire consumed litter (there occurred its "instantaneous" decomposition, which could take several years under normal conditions, depending on a forest type), we should have expected some increase in radionuclide mobile forms in the top mineral soil horizon due to that instantaneous source. Since the plants died and their root system no longer accumulated radionuclides in the soil root layer; while interacting with the soil system components, the mobile forms of radionuclides should have redistributed through the soil profile as a result of vertical migration processes. Measurement results for radionuclide concentrations in the litterfall samples are given below (Table 4.6). The results obtained for the radionuclide activity concentrations demonstrate differences between the two plots, primarily in terms of sources of radionuclides. While for the Red Forest (1), the trench was a source of radionuclides in the litter; for the west part of the fire site (2), a thin layer of undisturbed soil was a source of radionuclides. This is confirmed by several-fold differences in the values of 90Sr/137Cs ratios between the two sites with similar vegetation. Higher 90Sr/137Cs ratio at the trench in the Red Forest indicates a more powerful source of 90Sr in its root layer, if compared to the site where initial fallouts were concentrated on its soil surface and a significant share of strontium could have possibly moved beyond the root layer from the moment of the accident and as a result of vertical migration. Generally, a trend towards a decrease in the ratio with time is observed on the fires sites.

Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

Table 4.6 – Dynamics of radionuclide activity concentrations in the samples of litterfall Sampling Date of point Sample sampling 137Cs, Bq g-1 Δ, % 90Sr,Bq g-1 Δ, % 90Sr/137Cs Bi-1/NF L11 2130 6 6000 8 2.8 Bi-1/F L21 2910 6 7420 8 2.5 Pi-1/NF L31 196 6 580 13 3.0 Pi-1/F L41 866 6 2710 9 3.1 9/27/2016 Bi-2/F L51 1060 6 310 14 0.3 Bi-2/NF L61 1190 6 400 10 0.3 Pi-2/F L71 66 6 70 26 1.1 Pi-2/NF L81 140 6 110 10 0.8

Bi-1/NF L12 1600 6 2900 8 1.8 Bi-1/F L22 2220 6 2240 9 1.0 Pi-1/NF L32 230 6 960 9 4.2 Pi-1/F L42 896 6 2860 7 3.2 3/28/2017 Bi-2/F L52 655 6 330 10 0.5 Bi-2/NF L62 774 6 390 10 0.5 Pi-2/F L72 83 6 90 16 1.1 Pi-2/NF L82 141 6 110 16 0.8

Bi-1/NF L13 2730 6 11380 8 4.2 Bi-1/F L23 2150 6 5000 8 2.3 Pi-1/NF L33 193 6 850 8 4.4 Pi-1/F L43 626 6 1990 8 3.2 9/12/2017 Bi-2/F L53 877 6 600 13 0.7 Bi-2/NF L63 621 6 1030 8 1.7 Pi-2/F L73 107 6 100 16 0.9 Pi-2/NF L83 79 6 105 15 1.3

Note on sample codes: Bi – birch; Pi-pine; F- fire site; NF- outside the fire site; 1 – site in the Red Forest; 2 – site in the fire site west sector.

Samples taken from the soil and litter were dried to air-dry state. 10 g aliquots were taken from the mineral horizon samples for ammonium acetate extraction. Prior to the extraction, gamma- emitting radionuclide concentrations were determined. The extraction was carried out for the ratio soil:AcNH4 (2M) of 1:10. The suspension was shaken for 2 hours, incubated at room temperature for 22 hours, and then filtered through a 0.45 μm membrane filter. 90Sr concentration was estimated in solid phase, using the standard radiochemical procedure for 90Sr radionuclide extraction at the 6M sample opening with nitric acid. Taking into account presence of insoluble fuel particles in the precipitation, the residue was also analyzed through gamma and beta spectrometry.

Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

Table 4.7 – Dynamics of radionuclide activity concentrations in the samples of mineral soil (0-5 cm layer) Sampling Date of point Sample sampling 137Cs, Bq g-1 Δ, % 90Sr,bq g-1 Δ, % 90Sr/137Cs Bi-1/NF M11 996 6 690 10 0.7 Bi-1/F M21 1430 6 780 8 0.5 Pi-1/NF M31 610 6 250 7 0.4 Pi-1/F M41 700 6 390 9 0.6 9/27/2016 Bi-2/F M51 1340 6 370 7 0.3 Bi-2/NF M61 650 6 170 9 0.3 Pi-2/F M71 115 7 60 12 0.5 Pi-2/NF M81 100 7 30 14 0.3

Bi-1/NF M12 870 6 510 7 0.6 Bi-1/F M22 1430 6 450 9 0.3 Pi-1/NF M32 590 7 260 8 0.4 Pi-1/F M42 790 6 440 7 0.6 3/28/2017 Bi-2/F M52 1380 6 320 8 0.2 Bi-2/NF M62 760 6 170 9 0.2 Pi-2/F M72 138 6 60 10 0.4 Pi-2/NF M82 160 6 40 13 0.3

Bi-1/NF M13 920 6 820 9 0.9 Bi-1/F M23 1820 6 810 8 0.4 Pi-1/NF M33 770 7 360 7 0.5 Pi-1/F M43 920 6 770 8 0.8 9/12/2017 Bi-2/F M53 950 6 330 7 0.3 Bi-2/NF M63 2140 6 660 7 0.3 Pi-2/F M73 165 7 40 10 0.2 Pi-2/NF M83 190 6 110 8 0.6

Note on sample codes: Bi – birch; Pi-pine; F- fire site; NF- outside the fire site; 1 - site in the Red Forest; 2 – site in the fire site west sector.

Pine 100 80 60

40 Sr mobile, % mobile, Sr

90 20 0 Сентябрь 2016 Март 2017 Сентябрь 2017

Pi-1/NF за пределами Pi-1/F пожар

100

Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

Pine

, % , 15

10 mobile

Cs Cs 5 137 0 Сентябрь 2016 Март 2017 Сентябрь 2017

Pi-1/NF за пределами Pi-1/F пожар

Figure 4.11 – Concentration dynamics of radionuclide mobile forms (acetate extract) in 0-5 cm top mineral layer of soil horizon under the pine canopy on burnt and unaffected sites (Red Forest) In contrast to the litter, 90Sr activity concentration in the top mineral soil layer is substantially lower than the one of 137Cs (Table 4.7). This indicates that strontium is much more mobile than cesium and migrates intensively from this horizon, both down the profile due to its vertical migration with soil moisture current, and into plants through their root system. No significant differences were detected in radionuclide concentrations in this horizon between the sites of fire and outside them. Presumably, the period of observations was not enough to detect the differences. The analysis results showed that concentration of mobile (hereinafter, the sum of water-soluble and exchangeable) 90Sr in the top mineral horizon of pine forest generally varied between 50 and 80%. In the sample, which was taken in September 2017, concentration of mobile strontium on the fire site was about 80% and significantly increased the same value in a reference sample taken outside the fire site (Figure 4.11). The concentration of mobile 137Cs in the samples taken at that point generally varied between 8 and 15%; therewith the upper range describes points that were sampled in an unaffected area (Figure 4.11). These values are high enough, which is typical of fresh radiocaesium fallouts [193]. A result of these values was biogenic migration of radionuclides from the trench body, which was a permanent source of soil surface contamination. In all the samples, mobile fraction of 137Cs on the fire site was significantly lower than that in reference samples. That is, fixation of this radionuclide by soil solid phase is observed on the plots that are located on the fire site. The results obtained showed that concentration of mobile 90Sr in mineral horizon under the birch canopy outside the areas affected by fire did not change over time and was approximately 80%. Concentration of mobile 90Sr at the fire site varied between 60 and 80%, with the lowest values obtained for March 2017 (Figure 4.12). Concentration of mobile radiocesium in the samples was also at the level that is typical of fresh fallouts (5-18%). Significant differences between the fire and reference sites were observed only in 2016. Concentration of mobile radiostrontium in top soil horizon in the pine forest outside the RWTLS "Red Forest" varied between 30 and 70% (Figure 4.13). In September 2017, concentration of mobile strontium in the fire site’s soil was twice as large as the one on the reference site. Generally, if you compare this site with the site in the "Red Forest", a share of exchangeable strontium was marginally lower there. A share of mobile 137Cs was a few percent of its total

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Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone concentration in the layer and was significantly lower than in the "Red Forest". In such soil conditions, these values are characteristic of "old" fallouts of this radionuclide [193]. Concentration of mobile radiocaesium in the fire site soil did not depend on the time of sampling and was approximately 1%. While in the reference site, these values varied within 1-3%. In the birch forest, concentration of mobile 90Sr in mineral horizon outside the fire-affected site did not change with time and was approximately 40%. Concentration of mobile 90Sr at the fire site varied between 40 and 50%, with the lowest values obtained for March 2017 (Figure 4.14). Concentration of mobile radiocaesium in the samples was also at the level of several percent. It should be noted that total concentration of 90Sr takes account of an activity share of this radionuclide that did not travel to the solution during its boiling in 6 M nitric acid. After the treatment, 90Sr activity in the soil residue was estimated by beta spectrometry. 90Sr activity value in the residue was as follows: 3-10% for the "Red Forest" site, 15-45% for the site in the fire site’s west part. The weight of evidence suggests that activity of this insoluble residue is represented by very stable uranium-zirconium particles. This fact is confirmed by 90Sr/241Am ratio, which average value in the residues (24) is very close to that of nuclear fuel at the moment.

Birch

100 80 60

40 Sr mobile, % mobile, Sr

90 20 0 Сентябрь 2016 Март 2017 Сентябрь 2017

Bi-1/NF за пределами Bi-1/F пожар

Birch

20 , % , 15

mobile 10 Cs Cs

137 5 0 Сентябрь 2016 Март 2017 Сентябрь 2017

Bi-1/NF за пределами Bi-1/F пожар

Figure 4.12 – Concentration dynamics of radionuclide mobile forms (acetate extract) in 0-5 cm top mineral layer of soil horizon under the birch canopy on burnt and unaffected sites (Red Forest)

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Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

Pine 100

Sr mobile, % mobile, Sr 90 20

0 Сентябрь 2016 Март 2017 Сентябрь 2017

Pi-2/NF за пределами Pi-2/F пожар

Pine

2 Cs moible, % moible, Cs

137 1

0 Сентябрь 2016 Март 2017 Сентябрь 2017

Bi-2/NF за пределами Bi-2/F пожар

Figure 4.13 – Concentration dynamics of radionuclide mobile forms (acetate extract) in 0-5 cm top mineral layer of soil horizon under the pine canopy on burnt and unaffected sites (west part outside the Red Forest)

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Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

Birch

70 60

50 , % , 40

moible 30 Sr Sr

90 20 10 0 Сентябрь 2016 Март 2017 Сентябрь 2017

Bi-2/NF за пределами Bi-2/F пожар

Birch

7 6 5 4 3

Cs Cs mobile, % 2 137 1 0 Сентябрь 2016 Март 2017 Сентябрь 2017

Bi-2/NF за пределами Bi-2/F пожар

Figure 4.14 – Concentration dynamics of radionuclide mobile forms (acetate extract) in 0-5 cm top mineral layer of soil horizon under the pine canopy on burnt and unaffected sites (west part of fire outside the Red Forest)

Basing on the results of the study, the following conclusions can be made: • Rather quick fixation of mobile 137Cs with soil mineral part occurs on fire sites; • Share of mobile 90Sr in top soil horizon shall decrease with time due to its vertical migration deep into the soil horizon; • Vegetation that died as a result of fire is a long-term (can be estimated based on a stand’s biological decay rate) source of migration of mobile radionuclides into soil.

4.3.10 Impact on surface air in case of fires The RWTLS "Red Forest" area poses a potential hazard of a secondary additional radionuclide contamination of the environment in case of fires, because several percent of the total activity concentration of caesium 137Cs and strontium 90Sr within the RWTLS area may be contained in the biomass and litter. This may cause an increased exposure of both fire and general staff in the ChEZ and public outside the ChEZ. However, all available data on the air concentrations of radionuclides in the ChEZ fire “near zone” point to the fact that the staff external exposure doses exceed the internal exposure ones due to inhalation of radionuclides. In July 2016, a rather long-

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Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone term fire occurred in the ChEZ and covered the mostly contaminated part of the western trail of radioactive fallout, including more than half of the RWTLS "Red Forest" (refer to Figure 4.15). According to the emergency monitoring data of SSE "Ecocentre", concentrations of caesium 137Cs and strontium 90Sr in the air on the Exclusion Zone border exceeded the average monthly values by two orders of magnitude. Directly during the fire suppression, activity concentrations of these radionuclides amounted to units of Bq/m-3. The radiation doses shall be assessed in future. Though apparently, additional doses to public shall be extremely negligible, and the external exposure doses of the fire-fighters shall exceed the inhalation constituent. The lesson learnt is that the system of routine monitoring of the ChEZ air contamination should more quickly change to a crisis mode in case of emergencies. With regard to scientific radioecological monitoring, description of a source function during various fires is of great interest (share of mobilized activity during different fires).

Figure 4.15 - The site of 2016 fire in the ChEZ with the classification of landscape types

4.4 Monitoring of ChNPP cooling pond

Decommissioning of the ChCP was started in late 2014. Water was continuously recharged to the ChCP from the Pripyat River by the cooling water intake (CWI-3). After its pumps were stopped, a gradual drawdown of the water level began, which shall continue another 5-7 years, until the level stabilizes at its natural equilibrium elevations. It is expected that the water level shall decrease by approximately 7 m, thus causing a transformation of the integrated water body with an approximate area of 22 km2 into several small lakes and exposing up to 15 km2 of the ChCP bed with high-level bottom deposits. To date, the drawdown of the ChCP water level has already exceeded 4.5 m (Figure 4.16).

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Figure 4.16 – Current condition of the ChNPP cooling pond

Prior to the change of the ChNPP cooling pond’s water level, the expected dose rate of gamma radiation over the dried bottom deposits was estimated (Figure 4.17). Main contributor to the dose rate (over 99%) is gamma radiation of the short-lived 137mBa, which is formed as a result of 137Cs decay. For a "flat" surface source, the factor of transition from soil contamination density to equivalent dose rate (EDR) is 2.610-3 (μSv∙h-1)/(kBq∙m- 2) for 137Cs+137mBa at 1 m height above the ground surface; and for a uniform distribution of activity in 5-cm top layer, it is 0.81.110-3 (μSv∙h-1)/(kBq∙m- 2). The maximum equivalent dose rate in the air of 100x100 m site was predicted to be at a level of 30-40 μGy/hr in the mid-ChCP north and west parts. Maximum EDR levels (up to 60 μGy/hr) could be along coastlines of some residual lakes, due to maximum concentrations of 137Cs in these sites’ bottom deposits (Figure 4.17). During the ChCP discharge, activity could partially migrate to the deepest parts of the ChCP, which could result in lower radioactive contamination of remaining bottom deposits. Partially in the ChCP territory, the predictive estimates of equivalent dose rate (EDR) could exceed the reference levels (RL) in the the ChCP north (14 μSv/h) and south parts (7 μSv/h) (Figure 4.17). Some sites with an area over 100x100 m and EDR exceeding the reference level (7 mSv/h) could occur in the ChCP south part (mid-west part of the ChCP) [194]. Total area of the sites where EDR exceeded the RL could be approximately 15 ha in the ChCP south part (no allowance made for coastal stripes along remaining lakes). Presumably, some protective measures would be required to reduce the EDR level there (removal of the bottom deposits’ top contaminated layer, covering of contaminated layer by "clean" soil, plowing of contaminated layer, etc.). To this end, a program of routine and scientific monitoring was envisaged, progressively as the water level reduces in the cooling pond. And EDR should have been measured. In case a significant difference from the predicted situation occured (over 50%), radiation contamination maps should have been corrected and calculations to forecast additional doses should have been made. In the case local plots, where contamination exceeded 14 μSv/h (acceptable level according to the technical specification), were revealed, further drawdown should have been stopped and experts should have been involved to analyze situation and adjust the project documentation. The scope and frequency of monitoring should have been established with due regard for the water drawdown schedule. Unfortunately, this monitoring program was implemented only partly by the subdivisions of RSS SSE ChNPP (Figure 4.18) [9]. To verify the estimates validity, EDR was measured in 2017 at the sites with the estimated highest levels of radioactive contamination in drained bottom deposits of the north part and in

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Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone the middle, on the ChCP south bank near the discharge channel (Figure 4.19). The equivalent ambient dose rate was measured at 1 m height by RKS-01 STORA-TU radiometer-dosimeter (ECOTEST, Ukraine). Geographic coordinates of each point were referenced by GPSmap78s receiver (Garmin, USA). Site 1 was chosen based on maximum EDR levels measured in the ChCP north part in 2017. It was 100 m to the south-west of the area with the maximum levels of 137Cs contamination density in drained bottom deposits, which were obtained prior to the ChNPP cooling pond drawdown (Figure 4.17, Figure 4.19). Measurement results showed that the maximum EDR levels of approximately 50 Sv h-1 in the ChCP north part (Site 1) predictably exceeded the reference levels of 14 Sv h-1 (Figure 4.20a) and approximately 2 times exceeded earlier estimates for radionuclide concentrations in 5-cm surface layer (Figure 4.17), despite the fact that 137Cs was fairly evenly distributed in the 20-cm layer of the drained bottom deposits in the areas with high EDR (Figure 4.21a). This may be due to both inaccuracy of the maps for bottom deposits contamination density, which were used for the calculations, and redistribution of radionuclide activity during the water drawdown process in 2014-2017. Maximum EDR levels (Figure 4.20a) were observed on plots with silty bottom deposits of dark color, characterized by high fixation level of 137Cs and fine dispersed composition subject to stirring. EDR measurement interval on Site 2 (Figure 4.19, Figure 4.20b) was approximately 10 m from its water borders y at the time of measurements. The obtained results (Figure 4.20b) corresponded to earlier estimates (Figure 4.17, Figure 4.19), and the reference level of 7 Sv h-1 was not exceeded anywhere. Most of 137Cs activity was predictably concentrated in the 5-cm top soil layer (Figure 4.21b). Since according to the TOR, EDR values should be measured on a 100x100 m site, the average EDR values shall be significantly lower than the maximum recorded levels. In 2017, SSE "Ecocenter" measured 137Cs contamination density at 67 points in drained bottom deposits along the ChCP perimeter (excluding its north part); the value was 136÷6,207 kBq/m2, which corresponded to the EDR below the reference level of 7 Sv h-1. The above data are consistent with the results of EDR measurement along the shoreline in accessible dry points taken by the RSS of SSE ChNPP in 2017 (Figure 4.18). However, the method of designing and detailing the "spot", where EDR levels amounted to 10 Sv h-1 and which was detected in the ChCP south part during the study performed by the RSS of SSE ChNPP (Figure 4.18), should be refined. Generally, the values of EDR obtained by different organizations after the ChCP bottom deposits drainage have confirmed reasonability of the ChCP areal division into a north sector (zone 1) with the EDR reference level of 14 μSv/hour and the rest part of the ChCP (sector 2) with the EDR reference level of 7 μSv/hour. Maximum EDR levels were observed on drained sites of silty bottom deposits of dark color with high soil fertility, which was due to their dispersed composition and presence of organic material, which caused their rapid and dense overgrowing by grassy and woody vegetation.

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а б

Figure 4.17 – Distribution of gamma exposure dose rate at 1 m height above the drained plots, with radionuclides present on the surface (a) and in 5-cm surface layer of bottom deposits (b)

Figure 4.18 – EDR along the ChCP coastline on its drained plots Blue – to a maximum of 50 μSv/hour; Light-blue – to a maximum of 20 μSv/hour; Red – to a maximum of 10 μSv/hour; Yellow – to a maximum of 5 μSv/hour; Green – to a maximum of 1 μSv/hour.

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Site 1

Site 2

Figure 4.19 – Location of EDR monitoring sites

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б Figure 4.20 – Distribution of dose limit on Site 1 in the ChCP north part (а) and on Site 2 on the south shore in the mid-ChCP (b) in 2017

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b Figure 4.21 – Typical vertical breakdowns of radionuclide inventory in bottom deposits of the ChCP north part on Site 1 (a) and on the south shore in the mid-ChCP near discharge channel on Site 2 (b) On the one hand, predictive estimates supposed that moss-and-lichen covers with sparse grass and tree-shrub plants shall form on some of shallow sections of the ChCP bottom only after a long time (20-40 years) following the drainage, similarly to a washed dam on the left-bank floodplain. On the other hand, reservoirs in the left-bank floodplain, which were drained due to a water drawdown in 2001, were subject to complete overgrowth with grass and tree-shrub vegetation in 5-8 years. The most intensive overgrowth was supposed on the plots with silty bottom deposits (with remained flooded soils) at 6-8 m depth with a flat slope and high-level radioactive contamination. In actual practice, an intensive overgrowth of fertile silty and sandy-silty plots of drained bottom deposits was observed in grass and tree-shrub vegetation as water level decreased by 4-5 m in 2017 (Figure 4.22). Nowadays, radionuclides, including those contained in fuel particles, are tightly bound to inert carriers; bottom deposit particles. With the decreased dispersed composition of bottom deposit particles, their specific surface area and, correspondingly, the radionuclide specific activity increase. Silty plots demonstrate the highest levels of radioactive 111

Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone contamination due to the presence of finely dispersed silt fraction and high concentration of organic matter (up to 50% of total weight) (Figure 4.23a). Due to a rapid and thick overgrowth (as early as in 2017-2018, willow was 3-4 m high in the ChCP north part) of silty plots with finely dispersed silt fraction of bottom deposits, the wind-induced lift of radioactive aerosols is significantly reduced there, as well as probability of staff access to the plots, which is extremely important for radiation protection within the ChEZ. During the ChCP water drawdown, there occurred a "linear" and quite thick overgrowth of its inshore zones due to wind-transferred seeds of herbaceous and tree-shrub plants, primarily of willow and birch (Figure 4.22). As water level gradually decreases in the ChCP, root system of its trees expands thus allowing their future development and stretching to groundwater level in sandy plots. Small plots of the ChCP are occupied by elevated sandy plots that formed land areas (comas), which are overgrowing very slowly according to xerophytic type forecasts [TEO] (Figure 4.23b). These plots are represented by washed coarse-grained sand with minimal levels of radioactive contamination, low wind-lift coefficients, and high dry deposition rate, thus they do not pose a radiological hazard to the staff. The same applies to shell and sandy beaches, where vegetation is absent or very sparse (Figure 4.24c). Specific activity of 90Sr in the shells amounts to several units of kBq/kg, but due to their large and non-respirable size they do not pose a hazard in terms of wind transfer or inhalation intake. The thick layer of shells (up to 50 cm) shields radiation of contaminated high-level bottom deposits, inclusive of transuranium elements, and prevents their wind transfer thus establishing a natural radiation shield. Formation of vegetation cover on drained plots of the ChCP bottom is ongoing pursuant to its soil and climatic conditions, fertility and moistening regime (Figure 4.24). Fertile silty and sandy-silty plots of bottom deposits with the highest radioactive contamination level are overgrowing most intensively, which contributes to a decreased wind transfer of radioactive aerosols and staff access to these areas. Relatively low root intake of radionuclides into vegetation and flammable materials on these plots are due to their high fertility caused by presence of organic matter and clay fraction, which is crucially important in case of fires in the ChCP area. At some locations near the discharge channel, CWI, ISF-2, "Semykhody" Checkpoint and in the ChCP south part (in the direction of Chornobyl town), stationary checkpoints to monitor air concentrations of radioactive aerosols were installed, as well as some plates to measure intensity of radionuclide fallouts (Table 1.1). According to the feasibility study, intrusion criteria should have been established and experts should have been involved into the analysis of situation in case the established reference levels are reached, and corrections were to be made to the project documentation should the need arise. In our opinion, the level of monitoring activities for the measurement of radionuclide concentrations in the air (Figure 1.2, Figure 1.3) and intensity of radioactive fallout was unfortunately improper, relevant experts were not involved.

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Figure 4.22 – Overgrowth of silty and sandy-silty plots in the ChCP north part with willow (Salix), silver birch (Betula pendula) and sparse trees of Scots pine (Pinus sylvestris) in 2017

a b Figure 4.23 – Silty (a) and sandy (b) plots on drained bottom deposits of the ChCP in 2017

a b c Figure 4.24 – Overgrowth of silty (a), sandy (b) and shell-sandy beaches (c) with vegetation in 2017

When assessing the potential hazards of ChNPP decommissioning, both positive and negative consequences of corresponding activities should be taken into account. An expected decrease of the groundwater level in the “near zone” around ChNPP, where the most of RWTLS are located, should be referred to the positive ones. According to forecasts, this shall result in a decreased transport of radionuclides to groundwater not only from the RWTLS, but also from lower 113

Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone premises of the Shelter Object, which also stay flooded sometimes. Drawdown of water level in the ChCP shall also reduce risks associated with a possible rupture of protective dam between the ChCP and the Pripyat River, and shall also significantly reduce the maintenance costs of the ChCP water level pumps.

The major negative post-effect of the ChCP decommissioning is uncovering of its radioactively contaminated bottom deposits. This entails a series of negative effects linked to the potential secondary transfer of radionuclides by wind, particularly under abnormal weather conditions. Also, a high level of vegetation contamination is probable, as well as appearance of grass fires in the uncovered areas, increased mobility and migration capacity of radionuclides, etc. Radiological conditions around the ChCP may deteriorate, thus causing higher doses of the ChNPP staff and of ChEZ in general.

The recent researches of radiological consequences of the ChCP decommissioning allow assessments of some related risks. Changes in the radionuclide contamination density of 137Cs, 90Sr, 238-240Pu, 241Am caused by secondary transfer of radioactive aerosols by wind was assessed on the ChNPP industrial site and in Chornobyl town. The following three scenarios were considered: 1) standard decommissioning of the ChCP under normal meteorological conditions, 2) under conditions of a dust storm, 3) with a grass fire on drained bottom plots of the ChCP, which shall be covered with reeds and grasses.

Figure 4.25 – Distribution of 238-240Pu activity: a) drained part of the cooling pond, b) predicted additional annual contamination of the adjacent areas caused by a secondary wind transfer

According to the calculations, wind transfer of radioactive aerosols from the ChCP drained plots shall not result in additional contamination of adjacent areas and shall be less than 0.005% annually of the already existing one (Figure 4.25). The maximum average additional annual levels of area contamination with 238-240Pu near the ChNPP (<1 Bq/m2•year) shall be even a hundred times lower than the contamination levels of the Chornobyl accident (50 Bq/m2). This also applies to other radionuclides.

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1 2 Figure 4.26 – Contamination with 238-240Pu after a 3-day dust storm, wind is directed to (1) the ChNPP and (2) to Chornobyl town: a) drained part of the cooling pond, b) additional contamination of adjacent areas

In the case of a 3-day dust storm, an additional secondary contamination of the ChNPP area may be 5 times higher, and the one of Chornobyl area may be 60 times higher, if compared to the annual wind transfer under standard weather conditions (Figure 4.26). However, if we compare these values with the existing contamination densities, then the addition shall be extremely small (less than 0.02% of the existing contamination level during a 3-day dust storm).

The contribution of meadow fires located on the drained plots to secondary contamination of adjacent areas is maximal for strontium 90Sr, but for absolute values it is still insignificant (less than 0.05% of the existing contamination level for strontium 90Sr).

Figure 4.27 – Radiography of a bottom deposit sample (m = 1.5 g)

The estimated results demonstrated no significant radiological consequences for the ChEZ staff caused by secondary wind transfer of radionuclides from the drained plots of the ChCP. For all the considered scenarios, additional component in the dose of 30-km zone staff (put in terms of 50-year EDE) shall be three orders of magnitude lower than the established reference levels and the levels approved by RSSU-97.

It should be noted that all the above cases of exceeding the reference levels of radionuclide concentrations in the air are of episodic nature under extreme conditions. Such exceeded

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Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone reference levels of radionuclide concentrations in the air are also periodically observed now during dust storms and forest fires in the ChEZ.

When water level in the cooling pond goes down, the bottom deposits highly contaminated with long-lived alpha-emitting radionuclides stay exposed. The entire ChCP area shall belong to an isoarea with the plutonium 238-240Pu contamination density exceeding 3.7 kBq/m2. This will not allow its usage for traditional economic activities and residence of humans in the foreseeable future. Most of radionuclide inventory in the ChCP bottom deposits is contained in fuel particles (Figure 4.27). At the same time, leaching of radionuclides from the sampled ChCP bottom deposits is not proportional, which may indicate different forms of their containment.

The results obtained by the method of successive extractions demonstrate that a sharp increase in radionuclide mobility in the uncovered plots of the ChCP should not be expected in the next 5-10 years.

The reason is long-term maintenance of weakly alkaline reaction in the drained bottom deposits (Figure 4.28) and presence of fuel component in the ChCP in the form of chemically stable fuel particles. Therefore, only the radionuclides, which currently stay in mobile forms (< 30% of total concentration), can participate in migration processes on the drained plots of the ChCP bed.

A large share of radionuclide activities stays removed from the solid phase of the ChCP bottom deposits, even after the application of “ultra-rigid” extraction conditions. This may indicate presence of strontium 90Sr, plutonium 238,239,240Pu, americium 241Am and partially caesium 137Cs in chemically-very-stable fuel particles. Consequently, this radionuclide share cannot be mobilized under natural conditions for tens of years.

Figure 4.28 – pH dynamics of the environment of bottom deposits after their draining

The obtained results demonstrate that up to 70% of radionuclide activities in the ChCP bottom deposits are still associated with fuel particles. At the same time, up to 5% of caesium 137Cs, 24- 28% of strontium 90Sr, 3.1-4.2% of plutonium, 17-18% of americium 241Am are in mobile forms. At the moment, concentrations of water-soluble and exchangeable forms of radionuclides in the ChCP bottom deposits do not exceed 2% of their total amount. Main contributors to the activity (> 70%) are particles with a diameter exceeding 10 μm. Consequently, the intensity of radionuclide mobility in the ChCP drained plots shall be determined by the processes of radionuclide destruction and leaching from particles of this size. A considerable spatial heterogeneity in physicochemical properties of the bottom deposits (Figure 4.23) and in the radionuclide presence forms is observed.

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Concentrations of exchangeable forms of strontium 90Sr in bottom soil on different plots of the ChCP can vary within 5-50% of its inventory. All the above require implementation of comprehensive scientific monitoring of the ChCP area. Based on its results, reliable scientific forecasts of radioecological situation in the ChCP area and its environmental impact assessments may be obtained.

Monitoring studies on the dynamics of radionuclide forms were started on the drained plots of the ChCP. The obtained initial data can provide background values for the assessment of various migration processes’ dynamics. To date, experimental sites were established for a twin sampling of drained bottom deposits and vegetation (willow shoot leaves). The plants are sampled to assess the dynamics of radionuclide mobility. Location of the experimental sites and general view of some of them are shown in Figures 3.27 and 3.28.

Figure 4.29 – Location of experimental sites at the drained plots of the ChCP bed

Point L1 Point L2

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Points L3, L4 Point L5 Figure 4.30 – General view of experimental sites at the drained plots of the ChCP

Figure 4.31 – Particulate composition and distribution of 90Sr activity on the fractions of fuel particle size in 0-25 cm cross-section of bottom deposits (point T1)

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0-3 сm 3-6 cm 6-9 cm m=1.25 g m =1.25 g m=1.12 g

9-12 cm m=1.2 g 16-20 cm 12-16 cm m=1.33 g m=1.24 g

20-25 cm m=1.4 g

A core of ChCP bottom deposits (0-25 cm) at Т1

Figure 4.32 – Radiographic images of samples from bottom deposit profile (0-25 cm sampling depth), taken from a drained ChCP plot at point T1

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Figure 4.33 – Electron microscopy study of the ChCP bottom deposits (works are carried out jointly with the Norwegian University of Life Sciences)

Also, the monitoring of behaviour of fuel component (FC), the so-called fuel particles, was started and is in progress on the ChCP drained plots. The monitoring includes studying the FC particulate composition, its distribution over the ChCP area and depth, its physicochemical characteristics and destruction dynamics (Figure 4.31 – Figure 4.33).

4.5 Main directions of radioecological monitoring of the environmental impacts produced by man-made facilities

Since 1998, a detailed scientific radioecological monitoring of the environmental impacts of temporary disposal sites has been performed through the example of trench No. 22. An international Ukrainian-French scientific ground was equipped there. The URIAR, IGS of the NAS of Ukraine, IRSN (France) and other scientific institutes took part in the studies on the site. The main areas of research included the following: • Determination of function of the radioactivity source (determination of radionuclide inventories in the trench; obtaining physicochemical characteristics of radioactive waste, their dynamics; radionuclide migrations in unsaturated zone; fuel particles destruction dynamics). The results obtained can be used to verify radionuclide migration patterns both in the unsaturated zone and with the groundwater flow [195, 196, 197, 198]; • Biogenic transport of radionuclides from the trench [199]; • Lateral migration of radionuclides with groundwater flow outside the trench [200, 201, 202, 203]; • Radiobiological effects of chronic exposure of organisms [204].

At present, the following directions of continued radioecological monitoring on this scientific site would be efficient:

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• Lateral migration of long-lived isotopes of plutonium, chlorine 36Cl and technetium 99Tc that may pose a potential hazard to humans in the distant future due to a their long-term decay period. • Studying properties of mobile forms of TUE, their physical and chemical characteristics; • Continued monitoring of strontium 90Sr concentration in the groundwater in order to identify the intensity changes and assess long-term trends in its lateral distribution; • Monitoring of characteristics of the aquifer (fluctuations of level, direction and rate of movement); • Studying the effects of fire for radionuclide mobility changes; • Studying the radiobiological effects of chronic exposure in organisms.

Scientific monitoring of biogeochemical migrations of radionuclides, including TUE, from the RWTLS with the groundwater and into vegetation through the example of CPS "Red Forest", dissolution of fuel particles in soils, radioactive waste and bottom deposits of the ChCP should be continued.

Scientific monitoring of the changed radiological situation on drained plots of the Chornobyl NPP cooling pond, as well as of dissolution of fuel particles under various conditions is currently in progress; and it should be continued.

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5 MONITORING OF NATURAL ECOSYSTEMS

5.1 Network of radioecological monitoring existing in the ChEZ

The current scientific radioecological monitoring within the ChEZ covers all major ecosystems of this area (Table 5.1). Main characteristics of the scientific test sites and research areas are given in Appendix A.

Within the framework of this study, the scientific organizations that have completed or continue their researches in the ChEZ area were surveyed with the objective to analyze the system of scientific monitoring within the ChEZ. The following questions were proposed for the survey: • Object of your researches (soil, water, air, organisms, etc.); • Your observation network (research site (sites), coordinates); • Time span (research start dare, frequency of observations); • Monitored parameters (activity of radionuclides, concentration of heavy metals, etc.); • Subject of your research, i.e. processes (for example, migration of radionuclides (3H, 14C, 36Cl, 90Sr, 99Tc, 129I, 137Cs, 238-241Pu, 241Am) and heavy metals (accumulation), frequency of radiobiological effects, morbidity, mortality, population dynamics, etc.); • List of analytical methods applied (sampling and measurement methods); • Collection, storage and exchange of information (links to publications, reports, etc. on your research issues); • Do you carry out monitoring to assess the effects of ionizing radiation for the carbon stocks in ecosystems (increase in biomass, rate of organic matter decomposition, etc.)? ; • Do you carry out monitoring to assess the effects of ionizing radiation for the biodiversity of ecosystems, populations and organisms?

The questionnaires were sent to the following organizations: • Ukrainian Research Institute for Hydrometeorology (URIH) • Institute of Hydrobiology of the NAS of Ukraine • Scientific Research Institute of Radiation Protection of the Academy of Technological Sciences of Ukraine • Chornobyl Center for Nuclear Safety, Radioactive Waste and Radioecology • Institute for Nuclear Safety Problems of the NAS of Ukraine • Scientific Engineering Center of Radiohydrogeoecological Site Studies of the National Academy of Sciences of Ukraine • SSE "Ecocenter" • Institute of Geological Sciences of the NAS of Ukraine • SSE “Chornobyl NPP” • Department of Radiobiology of the NUBiP of Ukraine • Educational and Research Institute of Forestry and Landscape Management of the NUBiP of Ukraine • Institute of Molecular Biology and Genetics of the NAS of Ukraine • Institute of Cell Biology and Genetic Engineering of the NAS of Ukraine • Institute for Nuclear Research of the NAS of Ukraine • Taras Shevchenko Kyiv National University • Institute of Zoology named after I.I. Shmalhausen of the NAS of Ukraine.

To date, the answers (see Appendix B) were received from the following organizations: • Institute of Hydrobiology of the NAS of Ukraine • Institute of Zoology named after I.I. Shmalhausen of the NAS of Ukraine 122

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• Institute for Nuclear Research of the NAS of Ukraine • Educational and Research Institute of Forestry and Landscape Management of the NUBiP of Ukraine • Institute of Cell Biology and Genetic Engineering of the NAS of Ukraine • Institute for Nuclear Safety Problems of the NAS of Ukraine.

Key data from the questionnaires are summarized below (Table 5.1).

Table 5.1 – Participation of Ukrainian scientific organizations in researches within the ChEZ Period of Object of No. Organization Research sites observation research Water bodies in the left-bank Aquatic floodplain of the Pripyat River: organisms the lakes of Hlyboke, Daleke, Institute of (aquatic Vershyna, Krasnenska Starytsia. Hydrobiology of 1988 – to 1 vegetation, The ChNPP cooling pond, the NAS of date mollusks, fish), Azbuchyn Lake, Yaniv Ukraine bottom deposits, Backwater, Pripyat River (near water Chornobyl town), Uzh River (near Cherevach Village) Institute of Kopachi, Chystohalivka, Nova Zoology named Animals (model Krasnytsia, Ilintsy, agricultural after I.I. species and 2 1986-2001 lands near Pripyat city, Shmalhausen of groups of species, Novoshepelychi Forestry; game the NAS of game animals) animals – generally within ChEZ Ukraine 1989 - to Macromycete ChEZ, Leliv, Kopachi, Paryshiv, date fungi, soil Dytiatky Forest Leliv (30˚09'36.63''E, ecosystems: soil, 51˚19'19.74''N), Paryshiv Institute for 2006 – to vegetation, (51˚17'57.54''E, 30˚18'17.43''N), Nuclear Research date macromycete Dytiatky (30˚07'21.83''E, 3 of the NAS of fungi 51˚07'13.37''N) Ukraine Fishes, water,

bottom deposits, The ChNPP cooling pond, 1986-2016 aquatic the Pripyat River vegetation, mollusks Soils and radioactive waste Institute for contained in Shelter Object, Nuclear Safety 1992 – to them, ground and 4 Shelter Object’s industrial site Problems of the date surface water,

NAS of Ukraine water buildup inside the Shelter Object, air Educational and Research 1996-1998, ChEZ, 74 observation points 4*4 5 Institute of Forest vegetation 2003-2007 km Forestry and Landscape 123

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Management of the NUBiP of Ukraine Institute of Cell Biology and Accumulation of Genetic 90Sr and 137Cs in 6 2007-2015 Town of Chornobyl Engineering of vegetation and the NAS of soils Ukraine

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Figure 5.1 – Current network of scientific radioecological monitoring sites in the ChEZ

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5.2 Scientific monitoring of radiobiological effects in natural ecosystems

Scientific monitoring of radiobiological effects in the natural ecosystems of ChEZ is required in order to solve the problems dealing with radioecological regulation. Establishment of radioecological regulation system is impeded due to a lack of data on the doses absorbed by plants and animals. Understudied are the corresponding radiation effects in biota obtained for natural conditions [205]. Implementation of the goals and objectives of this type of monitoring is not only of social, ethical (from the viewpoint of implementing the eccentric concept of radiation protection) and fundamental importance, but it is also valuable for the purposes of public health, since zoning of contaminated areas is possible basing on bio-indicative values of radiobiological effects. For example, four destruction zones are distinguished within the 30-kilometer ChEZ: zone of total death (lethal effects), sub-lethal damage zone, zones of severe and mild damage to the tree layer assimilatory system [206].

Within the monitoring system that is being currently developed, the environmental regulation of acceptable low doses of chronic exposure poses many difficulties. Among such difficulties is the infinitely large diversity of wild species. A solution to this problem was proposed in the ICRP recommendations of 2007, Publication 103 [Error! Bookmark not defined., Error! Bookmark not defined.]. The ICRP recommends applying the concept of “reference” animals and plants to all exposure cases. This is described in detailed in Publication 108 [207]. When selecting the reference biological species, their radiosensitivity, significance and prevalence in basic world ecosystems should be taken into account, as well as the amount of available radioecological and radiobiological data. It is assumed that the role of reference organisms within the radiation protection system for biota could be similar to the one of a "reference" (standard) human within the radiation protection system for people. Table 5.2 presents a list of reference animal and plant types pursuant to the ICRP recommendations, in terms of their prevalence in main types of ecosystems. According to the ICRP recommendations, a distinctive feature of the proposed reference organisms is their highest radiosensitivity (critical link, which withdrawal can cause irreversible changes in ecosystem integrity). Consequently, it is assumed that reactions of the reference types may be used to estimate acceptable levels of radioactive contamination in ecosystems.

Table 5.2 – Reference types of animals and plants in relation to their prevalence in main ecosystem types Type of ecosystems Terrestrial Fresh-water Sea-water Reference organism Deers Х Rats Х Ducks Х Х Anura Х Х Trout Х Х Flatfishes Х Bees Х Anura crayfish Х Х Earthworms Х Coniferae trees Х Herbaceous plants Х Х Brown algae Х

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The studied biological objects should include the plant and animal species that correspond to the list of reference organisms recommended by the ICRP. Among the recommended objects, coniferous trees deserve special attention. The clearest effect of acute chronic exposure was the death of pine trees growing next to the nuclear power plant, which was caused by the Chornobyl accident in 1986. A site of approximately 4 km2 in the pine forest was called the "Red Forest" due to the brick-red colour of needles in the dead trees. Currently, it stays among the most radioactively contaminated sites within the ChEZ, its absorbed dose rate in the air at a height of 1 m is about 40 μGy/hr [208, 209]. There are not more than 10 pine trees aged over 30 and belonging to the pine forest that died in 1986. Also, there is a clear deformation of crowns in all the trees [160]. Moreover, some morphological abnormalities (the so-called "morphosis"), such as annulment of apical dominance, dichotomy, curved trunk, exposure of shoots, chlorophyllic mutations, change in needle sizes, etc., were found in the Scots pine development. The abnormalities occur in the pines, which were subjected to acute exposure at the doses less than lethal that resulted from the Chornobyl accident [210], in their offspring [211] and in the pine trees that were artificially planted on some plots of the RWTLS "Red Forest" and were growing under the conditions of chronic ionizing exposure [212]. Due to the observed effects, this species is a popular research object in studying the biological effects of chronic ionizing exposure. At the level of ecosystem, these morphological changes can lead to a broken interrelationship between the ecosystem components: disintegration of top tier, thinning of stands, increased inflow of precipitation, dust and pollutants to lower tiers [Error! Bookmark not defined.]. To date, radiobiological effects in Scots pine are the most studied. Within the framework of this research, the available data on the Scots pine “dose-effect” dependences shall be summarized with the objective to establish and justify criteria for the radioecological monitoring system, which is being developed now.

Another problem of environmental regulation is its methodological aspect due to the insufficiency, methodological difficulties and inadequate standardization of techniques used for environmental practices [213, 214]. The long-term effects of acute and chronic exposure of wildlife (excluding humans) at low doses resulting from the Chornobyl accident have not been determined by now. The corresponding studies require availability of multipurpose, easy-to-do, and automated where applicable diagnostic techniques for individual species and complex ecosystems. To date, such techniques have not been developed and standardized because of the diffused attention of scientists to many different wildlife objects, inadequate dosimetric assessments and inconsistency of obtained results.

The authors have verified applicability of a relatively simple technique used for the indication of radioactive contamination and biological effects basing on fluctuating asymmetry parameters in the Scots pine and white birch. The studies were carried out for a wide rate range of exposure doses absorbed by trees, both external and internal ones (0.1-40 µGy/hr and 0.1-274 µGy/hr, respectively). It should be noted that this technique is widely used for the assessments of man- caused environmental contamination levels [215]. Fluctuating asymmetry parameters in the leaves of white birch (Betula pendula Roth.) and needles of the Scots pine, which grow on the ChEZ sites with different levels of radioactive contamination, were studied. Coordinates of the sites, absorbed dose rate and fluctuating asymmetry values for the studied tree species are presented in Table. 3.3. Inadequacy of this technique for diagnosing radioactive contamination and biological effects in reference plant species was demonstrated by the authors of this report [216] and in animals – by other researchers [217].

The developed method of biological dosimetry for acute exposure conditions in forest biogeocenoses, which is based on the effect of wood radial growth suppression in a year of exposure and its sharp increase in subsequent years, also proved inapplicable under the conditions of chronic exposure at low doses [218, 219]. 127

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Special attention should be paid to the biochemical and cytogenetic technique, which is widely used to analyse the states of natural populations. The most radiosensitive biological systems (meristems of plants) are used to indicate the genetic effects of chronic irradiation. Application of molecular, genetical and bio-chemical research techniques in the ChEZ area has shown the genetic effects of chronic exposure in populations, which typically display themselves at biochemical level [Error! Bookmark not defined.]. However, these techniques have not yet been widely used due to their methodological complexity and inconsistency of obtained results.

Values for pro-antioxidant condition of plant and animal cells also belong to the widely used methods of biochemical analysis applied to radiobiological effects diagnosing, because mechanisms of oxidative stress are common mechanisms of response to negative impacts of various nature. Due to the same reasons (lack of universal techniques, inconsistency of obtained results, etc.), these techniques currently do not belong to the unconditional indicators of chronic ionizing exposure. However, parameters of functional state of a cell antioxidant defence system are interesting as the mechanisms of adaptation to the effects of chronic ionizing exposure at low doses. Moreover, changes in these values can be both a cause (which is related to a signal function of active forms of oxygen) and a consequence of epigenetic changes. This explains the relevance of research and increased interest of scientists in oxidative stress values and in the activity of antioxidant defence enzymes.

The authors of the report have studied the values of functional state of antioxidant defence system in the cells of reference plant species Arabidopsis thaliana (L.), Heynh. (A. Thaliana), which is growing on the ChEZ sites with different levels of radiations contamination, and in the cells of the plant sprouts. Coordinates of the sites and the absorbed dose rate in the studied plants are presented in Table 3.4. Contracting changes in the activity of antioxidant protection enzymes [220] depending on external absorbed dose rate were detected in A. Thaliana plants which grow directly in the ChEZ. The changes are probably of adaptive nature. Such changes have not been detected in the offspring of A. Thaliana, as well as changes in morphometric values of the studied sprouts of A. Thaliana depending on absorbed dose rate [221].

Within the framework of this research, the most efficient of currently available techniques for studying radiobiological effects shall be discussed and proposed in order to obtain a “dose- effect” relationship for reference organisms.

Integration of the available large amount of data for the purposes of environmental regulation seems impossible at the moment. The reasons include inconsistency of research objects and goals, lack of universal techniques, discrepancy of obtained results, and most importantly – inadequate dosimetric assessments. Some studies do not provide estimated radiation doses or cannot be applied to quantitative analysis of data.

Table 5.3 – Absorbed dose rate and fluctuating asymmetry index for the white birch leaves (Betula pendula Roth.) and the Scots pine needles (Pinus sylvestris L.) on the exclusion zone sites with different levels of radioactive contamination Type Absorbed dose rate, μGy/hour Fluctuating of Coordinates of site Total of asymmetry sampl External Internal external and index e internal N 51.382381 39.3±1.4 97±11 136±11 0.052±0.006 E 30.033179

N 51.383957 birch 13.4±2.1 180±19 193±19 0.054±0.009

E 30.072232 of Leaves 128

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N 51.383846 11.9±4.1 165±18 177±19 0.048±0.007 E 30.072289 N51.372305 5.7±0.5 13±1 19±1 0.060±0.009 E 30.029117 N 51.346963 0.6±0.1 0.6±0.1 1.3±0.6 0.051±0.006 E 30.126321 N 50.898991 0.11±0.02 0.05±0.01 0.2±0.1 0.054±0.008 E 29.952973 N 51.382381 39.5±2.5 152±19 192±19 0.014±0.002 E 30.033179 N 51.383957 12.6±2.4 273±34 286±34 0.018±0.002 E 30.072232 N 51.383846 13.5±1.9 105±13 118±13 0.017±0.001 E 30.072289 N51.372305 5.1±0.6 5.0±0.6 10±1 0.017±0.002 E 30.029117

N 51.346963 pine of Needles 0.6±0.2 0.45±0.06 1.0±0.2 0.015±0.001 E 30.126321 N 50.898991 0.13±0.02 0.09±0.01 0.22±0.02 0.015±0.001 E 29.952973

Table 5.4 – Characteristics of Arabidopsis thaliana (L.) Heynh. sampling sites and the plant absorbed radiation dose Specific activity of External Hu radionuclide, Internal absorbed dose rate, Coordinates absorbed mi kBq/kg of dry Location μGy/hour of site dose rate, dity, matter % 90Sr + μGy/hour 137Cs 90Sr 137Cs 90Sr 37Cs N 51.34531 Kopachi 2 0.28±0.01 71 0.48±0.1 17.0±1.0 0.019±0.04 2.5±0.2 2.5±0.2 E 30.12861 N 51.34707 Kopachi 1 1.03±0.04 67 0.21±0.06 17.3±1.0 0.010±0.003 3.0±0.2 3.0±0.2 E 30.12488 Site between N 51.37934 Yaniv and 7.85±0.04 52 12±1 115±22 0.82±0.08 28±6 29±6 E 30.02503 Chystohalivka N 51.38457 “Red Forest” 12.93±0.08 27 137±14 418±36 14.0±1.4 156±14 170±15 E 30.04076

The outcomes of radiobiological effects’ scientific monitoring in reference plant and animal species, and the monitoring system itself, will not be overtaken by the years moving the society away from the Chornobyl accident. The problems of radioactive contamination are still relevant due to a continuously increasing number of nuclear fuel cycle facilities being potential sources of accidents as well as sources of continuous radiation impacts on the environment.

Scientific monitoring of the radiobiological effects, radionuclide accumulation dynamics and exposure dose in reference plant (the Scots pine and wild grasses) and fish species in the ChEZ is currently in progress. Expanding the list of monitored objects is sceduled for 2018.

In 2005-2007, the URIAR organized several sites to monitor radiobiological effects in Scots pine trees in the forest cultures of this tree species located in the RWTLS "Red Forest" territory: at the trenches and outside them (274 trees), near the village of Chystohalivka (150 trees), also there were reference tress near the town of Ivankiv outside the ChEZ (100 trees). At the time of sites 129

Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone establishment, the pine trees were approximately 20 years old. Each tree on the sites was assigned a continuous number (Figure 5.2).

Figure 5.2 – Number tags on the Scots pine trees, which are observed to identify the radiobiological effects

Based on the observations results, the URIAR scientists completed the following: 1. Developed a dosimetry model that allows estimation of absorbed dose in trees apical meristem. For the experimental array trees, the absorbed dose rate in trees top meristem varied between 4.5 mGy· yr-1 on a test site near the town of Ivankiv and a few grays per year in the trees located at the trenches of Red Forest. 2. Established that numerous cell damages occur in the Scots pine seed material under chronic exposure impacts from incorporated radionuclides. For the experimental array, which included a wide range of radioactive contamination in trees, there was demonstrated a tendency towards increased contribution of deletions to the total number of damages, from 75 to 95% with increasing level of absorbed dose in pine organs. It was statistically established that percentage of aberration cells increased with the level of absorbed dose in pine organs. 3. For the actual conditions of Chornobyl radioactive contamination, a “dose-effect” dependency was developed for cytogenetic (percentage of aberration cells in apical meristem of primordial roots) radiobiological effects during chronic exposure to Scots pine. The results of cytogenetic studies can be used to regulate permissible limits for biota exposure and to develop theoretical approaches to radiobiological effects description [222].

5.3 Radioecological monitoring of aquatic ecosystems

The unique data on radionuclides contamination dynamics and their clearance from fish organisms in different seasons under the natural conditions of ChEZ were obtained for the first time on the test sites of URIAR (Figure 5.3, Figure 5.4).

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Figure 5.3 – Scientific monitoring at the Hlyboke Lake in November and December 2017

For the first time, values of 137Cs excretion rates from the body of silver Prussian carp (Carassius о gibelio) were experimentally obtained: kb=0.0022±0.0006 1/d (T1/2=315±93 days) at 5±1 С water temperature and kb=0.0094±0.0005 1/d (T1/2=74±5 days) at 22±1 °C water temperature (Figure 5.4a). Similar values for biological half-life of 137Cs activity excretion from fish о organism (Af(t), Bq/kg) T1/2 = 70±8 days were obtained for 22±1 С water temperature. In the Hlyboke Lake, 137Cs accumulation rate in the silver Prussian carp (Carassius gibelio) body was approximately kf=12±3 1/d.

For the first time, values of 137Cs intake rates by the body of silver Prussian carp (Carassius gibelio) out of water with 2 mg/l potassium content (kw=0.045±0.002 1/day, T1/2=350 days) (Figure. 5.4b) at T=5±1 °C temperature were experimentally obtained.

Our results demonstrate that the rate of radiocaesium intake into fish organism from water at a 137 low temperature of 5 °C (kw) is hundreds of times lower than the rate of Cs intake with food (kf=10-15/day). Nonetheless, the estimated values kw are critically important for the forecasts of fish contamination in autumn-winter-spring seasons at a water temperature of 5 °C.

It was demonstrated that the dynamics and levels of fish radioactive contamination in case a lake is contaminated shall differ fundamentally in an autumn-winter-spring season (November- March) from radioactive contamination of water bodies in a spring-summer-autumn season (May-September) at a water temperature of approximately 20 °C (Figure 5.5). In such a case, the difference in 137Cs specific activity in a fish body shall be two orders of magnitude during 4 months.

Because of cold weather in March 2018, the monitoring shall be continued immediately after ice melts on the ChEZ lakes.

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b 137 Figure 5.4 – Relative decrease in Cs activity in fish (Af(t)/Af(0)) at a water temperature of 5±1 оС without feeding (А3) and at a water temperature of 22±1 оС with fish feeding (А4, А5) – а), 137 137 and relative dynamics of Cs accumulation in fish (ration of Cs in fish muscular tissue Cf(t) о and its specific activity in water Cw) at a water temperature of 5±1 С without feeding (A2) –b), and corresponding exponential and linear dependences.

137 Figure 5.5 – Dynamics of Cs specific activity in the water of closed water bodies (at Cw(t=0) =1000 Bq/kg) and in the meat of silver Prussian carp (Cf(t), Bq/kg) at a water temperature of T = 5±1 оС and T = 22±1 оС

5.4 Radioecological monitoring of agro-ecosystems

In 2000, the URIAR organized a unique scientific monitoring site near Chystohalivka village (51.372305°, 30.029117°) in order to study the aerial and root intake of ultra-long-lived and mobile radionuclides (such as chlorine 36Cl, selenium 75Se, technetium 99Tc, iodine 129I) by various agricultural crops from the four soils having contrasting characteristics and taken from different parts of Ukraine (Figure 5.6). Much of the data obtained at this site are world-unique and were for the first time ever included into modern international reference books on radiation

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Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone protection of humans and environment (Figure 5.7) [223, 224, 225, 226, 227, 228 ]. The long- term scientific monitoring at this site should be continued.

Figure 5.6 – Performance of scientific monitoring of the behaviour of ultra-long-lived and mobile radionuclides, such as 36Cl, 75Se, 99Tc, 129I, 238-240Pu, 241Am, at the URIAR experimental site

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Figure 5.7 – Dependence of radioiodine accumulation factors in radish roots according to Kd 125I (a) and stable iodine (b); as well as stable iodine concentration in soil (c) and humus (d) for different types of soil

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6 DEVELOPMENT OF PREDICTIVE ESTIMATES OF RADIATION SITUATION IN THE EXCLUSION ZONE

At present and in the next few decades, the following medium- and long-lived radionuclides shall be of main radiological significance in the ChEZ: 90Sr, 137Cs, 238Pu, 239Pu, 240Pu, 241Am. At the time of release, the bulk of 90Sr, 238Pu, 239Pu, 240Pu and 241Am was in the particle matrices of irradiated nuclear fuel; i.e. the fuel component of Chornobyl radioactive fallout [Error! Bookmark not defined., 229, 230]. Consequently, the maps of contamination densities in the near zone around ChNPP are similar for these radionuclides (Figure 6.1).

As a result of nuclear fuel dispersion during the initial explosion and after its oxidation in the air, fuel particles (FP) were formed [231]. The density of fuel particles, which ranged in size from one to hundreds of microns, was 8-10 g/cm3. This caused a high rate of FP dry gravitational settling from a radioactive cloud and a rapid decrease of radioactive contamination of the near zone around ChNPP with the distance.

Unlike radionuclides in the fuel component of Chornobyl radioactive fallout, transmission of volatile and highly mobile 137Cs occurred mainly due to high-temperature annealing of nuclear fuel followed by its condensation on various media (the condensation component of Chornobyl radioactive fallout), which resulted in a fundamentally different pattern of radioactive contamination in the area (Figure 6.1 b).

i Density of area contamination by the i-th radionuclide at a specific time point ( As ) is the basic input information for radiation protection of personnel, people and the environment: assessing the possibility of people living, economic use of lands and their decontamination, levels of radioactive contamination in products, flammable materials and radionuclides release in case of fires, as well as calculating the equivalent external exposure dose rate and effective internal exposure doses caused by inhalation and peroral intake of radionuclides.

Table 6.1 – Main characteristics of radionuclides and their dose coefficients [232, 233]

i i i-th radionuclide Half-life (Т1/2) Specific activity of the Main type of Bs , Binh , i-th radionuclide in exposure (µSv/h)/ µSv /Bq Chornobyl nuclear fuel µSv/Bq (kBq/m2) in 2018, Bq/g 90 90 1 Sr  Y 29 years 5.9E+08 β 6.2E-6 2.8E-2 3.2E-2 (64.26 hours) 137 137m 2 Cs Ba 30.17 years 7.0E+08 β, γ 7.9E-4 1.3E-2 6.7E-3 (2.5 min) 238 3 Pu 87.74 years 6.3E+6 α 5.8E-8 110 43

239 4 Pu 24100 years 5.1E+6 α 1.2E-7 110 47 240 5 Pu 6563 years 7.8E+6 α 5.7E-8 110 47 241 6 Am 432.8 years 2.5E+7  1.7E-5 110 39

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a b

c d Figure 6.1 – Density of ChNPP EZ contamination by: 90Sr (a), 137Cs (b), 239-240Pu (c) and 241Am (d) [229, 230]

6.1 Monitoring of the environment contamination with 241Am

Often is raised the issue of an increased radiological significance of ChEZ area contamination with 241Am with time because of its increasing activity. Therefore, special attention should be paid to routine and scientific monitoring of this radionuclide in the exclusion zone.

241 Indeed, accumulation of and increase in Am activity (T1/2 = 432.8 years) shall occur with time 241 on fuel trace of the Chornobyl radioactive fallout due to the radioactive decay of Pu (T1/2 = 14.4 years) (Table 6.1). Maximum of 241Am activity shall be reached approximately in 70 years after the Chornobyl accident, but the increase in 241Am activity shall not exceed 20% of the current level of 2017-2018 (Table 6.2). Figure 6.2 shows the dynamics of relative activity of alpha-emitting radionuclides (in reference to the activity of long-lived 239+240Pu) in the fuel component of Chornobyl radioactive fallout. While 241Am activity is increasing (approximately 239 . 4 240 50 years), the activity of long-lived Pu (T1/2 = 2.41 10 years) and Pu (T1/2 = 6563 years) 238 shall practically not change, and the activity of Pu (T1/2 = 87.74 years) shall decrease by 40% because of its radioactive decay (Table 6.2, Figure 6.2). As a result, total activity of alpha- emitting radionuclides shall be slightly increasing over the next 50 years, and further shall be monotonically decreasing (Figure 6.2). Therewith, maximum total activity of alpha-emitting radionuclides shall only be 6% higher than the current level of 2017-2018. With equal dose factors per a unit of inhalation intake activity for alpha-emitting radioisotopes of plutonium and americium (Table 6.1), such a small change in their activity in the next 50 years (6% only) shall 136

Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone not produce any significant effect on conservative estimated values for inhalation doses of personnel and population with all considered scenarios, the same refers to the biota exposure.

Table 6.2 – Dynamics of changes in specific activity of alpha-emitting radionuclides in the fuel component of Chornobyl radioactive fallout, Bq/g

Year Radionuclides 2017 2021 2026 2031 2036 2046 2056 2076 2086 2136 238 Pu 6.3E+6 6.1E+6 5.8E+6 5.6E+6 5.4E+6 5.0E+6 4.6E+6 3.9E+6 3.6E+6 3.6E+6 239Pu 5.1E+6 5.1E+6 5.1E+6 5.1E+6 5.1E+6 5.1E+6 5.1E+6 5.1E+6 5.1E+6 5.1E+6 240Pu 7.8E+6 7.8E+6 7.8E+6 7.8E+6 7.8E+6 7.8E+6 7.7E+6 7.7E+6 7.7E+6 7.7E+6 241Am 2.5E+7 2.6E+7 2.8E+7 2.8E+7 2.9E+7 3.0E+7 3.0E+7 3.0E+7 2.9E+7 2.9E+7 Total 4.4E+7 4.5E+7 4.6E+7 4.7E+7 4.7E+7 4.7E+7 4.7E+7 4.6E+7 4.6E+7 4.6E+7

In the next 50 years, the increase of 241Am activity in soil and bottom deposits of the ChNPP cooling pond over time shall not produce any significant effects on the equivalent dose rate (EDR) within the ChEZ (Figure 6.3). The decrease of EDR over time shall mainly be due to radioactive decay and vertical migration of 137Cs. This is due to the fact that minimum values of 137Cs/241Am activity ratios currently amount to approximately 30 in the fuel component of radioactive fallout, they increase with a growing fraction of 137Cs activity on condensation particles and surface contamination due to sorption processes of silty particles in the bottom deposits. Moreover, even with equal density of 137Cs and 241Am soil contamination, the EDR of 137Cs137mBa radiation shall by 26 times (for surface distribution of activity), 50 times (for uniform distribution of activity in 5-cm soil layer), 70 times (for uniform distribution of activity in 15-cm soil layer) exceed the EDR of 241Am soft gamma radiation [233]. Altogether, these shall result in the fact (Figure 6.3) that current contribution of 241Am to EDR buildup on the ChNPP CP drained plots shall not exceed 0.1%, even if they are contaminated only by fuel particles (the case of 137Cs/241Am minimum activity ratio). Even after 100 years, contribution of 241Am to EDR buildup shall not exceed 1%.

Therefore, the approaches to 241Am monitoring should not be changed, since 20% increase in 241Am activity in the next 50 years shall not have any significant impact on changes in the buildup of internal and external exposure inhalation doses to personnel and biota in the ChEZ.

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Figure 6.2 – Dynamics of relative contribution to alpha-emitting radionuclides activity in the ChEZ

Figure 6.3 – Dynamics of relative contribution to 137Cs and 241Am EDR buildup on fuel traces of the radioactive fallout, with a uniform distribution of activity in 5-cm surface soil layer (current 241Am contribution to EDR buildup was accepted to be 1).

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6.2 Changes in the ChEZ soil contamination density

There was carried out the analysis of radioactive contamination of the exclusion zone area with long-lived radionuclides using the probabilistic approach of exceeding legally established criteria for the zoning of radiation-hazardous lands, where population living and conduction of traditional economic activities are impossible in the long term. Contamination density in the ChEZ area was estimated with due regard for the radioactive decay of radionuclides in 100 years (90Sr and 137Cs in 2117) and in 500 years (for the sum of plutonium radioisotopes 238-240Pu). In accordance with the legally established zoning criteria and with the use of probabilistic approach (50% and 90% probability), isolines of area contamination density for 137Cs, 90Sr, and 238-240Pu were developed for the territories, where population living in the long term is impossible due to the radiation (Figure 6.4- Figure 6.6).

At present, the isolines corresponding to radionuclide contamination density thresholds in the areas unsuitable for population living are mostly located in the 10-km near zone, excluding a small part of the "southern trace", which stretches slightly further south beyond the 10-km zone and reaches the town of Chornobyl (Figure 6.4-Figure 6.6). In 100 years, by 2117, the area where the levels of 137Cs and 90Sr contamination exceed 555 (Figure 6.4) and 111 kBq/m2 (Figure 6.5), respectively, shall reduce significantly due to radioactive decay; to the line of Kopachi-Buriakivka-Usov population centers.

Figure 6.4 – Predicted boundaries of 555 kBq/m2 isoline for 137Сs contamination density in the ChEZ at different times

Within the ChEZ, the boundaries of 238+239+240Pu at the level of 3.7 Bq/m2 shall change slightly over 500 years, and only in its southern part they shall stretch beyond the 10-km zone, while reaching the town of Chornobyl and the Uzh River (Figure 6.6).

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Figure 6.5 – Predicted boundaries of 111 kBq/m2 isoline for 90Sr contamination density in the ChEZ at different times

Excluding the area of industrial site and the ChNPP cooling pond, the area in ChEZ, where 239- 240Pu soil contamination density exceeds 4 kBq/m2, amounts to approximately 450 km2 (less than 20% of the ChEZ total area) (Table 6.3). However, simultaneously it contains over 88% of long- lived plutonium radioisotopes activity in soil (excluding the RWTLS). Approximately the same area in ChEZ (about 500 km2) had 137Cs contamination density that exceeded 555 kBq/m2 as of 2011 (Table 6.4) [229, 230].

Table 6.3 – Distribution of 239+240Pu activity in 30-cm top soil layer in 30-km ChEZ, outside the ChNPP industrial site and excluding the radioactive waste disposal sites and the ChNPP cooling pond [230] 239+240Pu contamination 239+240Pu activity Area level, kBq/m2 Bq % km2 % 0-0.1 2.74E+09 0.02 91 4.6 0.1-0.4 9.53E+10 0.6 381 19.1 0.4-1 3.89E+11 2.5 556 27.9 1-4 1.30E+12 8.4 519 26.0 4-10 1.21E+12 7.9 173 8.7 10-20 1.65E+12 10.7 110 5.5 20-40 2.79E+12 18.1 93 4.7 40-100 3.13E+12 20.3 50 2.5 100-200 2.13E+12 13.8 15.6 0.8 200-400 1.50E+12 9.7 5.4 0.3 >4000 1.19E+12 7.7 2 0.1 Total 1.54E+13 100.00 1996 100.0

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b Figure 6.6 – Predicted contamination density of 238+239+240Pu in the ChEZ area, as of 2017 (а) and 2517 (b)

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Table 6.4 – Breakdown of the ChEZ area in terms of 137Сs contamination density (global and Chornobyl ones) in Ukraine, as of 26 April 1986 and 10 May 2006 [234, 235] Total area, thsd km2 Year Area with 137Cs contamination density, thsd km2 <40 40-185 185-555 >555 kBqm-2 kBqm-2 kBqm-2 kBqm-2 2.6 1986 0.8 0.9 0.9 2006 1.2 0.8 0.6 2011 0.5 0.8 0.8 0.5

Thus, a long-term stable contamination with long-lived alpha-emitting radionuclides has formed in the 10-km zone of ChEZ around the ChNPP, which will not allow the population to stay there in the foreseeable future. Establishment of a special zone for technical applications (SZTA), having an exclusive "lifetime" status of unfitness for population living, is planned in this area with due regard for the regulatory and legislative framework existing in Ukraine, provisions of international safety standards and documents of the European Union. The rest of ChEZ, where return of population and conduction of traditional economic activities are not planned (the Chornobyl Radiation and Ecological Biosphere Reserve), should be a buffer zone between the SZTA and the territory, where people live.

Based on the radionuclide contamination density dynamics in the area, it can be concluded that radiological monitoring in the ChEZ should be carried out for hundreds and thousands of years.

6.3 Predicted transformation dynamics of the fallout’s fuel component on the ChNPP CP drained plots

The research results obtained during the scientific monitoring of the ChNPP CP allowed us to estimate the current state of fuel component in bottom deposits and to assess the dynamics of fuel particles transformation on drained plots. Radiographic studies confirmed presence of Chornobyl fuel particles in the ChNPP CP bottom deposits. The obtained results demonstrate that the most chemically stable fuel particles have a size of approximately 3 μm. Estimation of the fuel particles’ disperse composition in reference points showed that the highest concentration of fuel particles is typical of the ChNPP CP north part. The activity ratio of 137Cs and 90Sr amounts to 4 in the northern part of the water body, 12 – in the central part, 25 – in the southern part. This may indicate a different contribution of the fuel and condensation components of radioactive fallout to the contamination of ChNPP CP bed [236]. The calculated transformation ratio of fuel component in the ChNPP CP indicates that the water body was mostly contaminated with chemically stable fuel particles with UO2 matrix.

The predicted results of radionuclides mobility on the drained plots of ChNPP CP are based on the studies of radionuclide containment forms dynamics in actual bottom deposits of the ChNPP CP while simulating their drying and exposure in the field conditions on experimental site in the course of 47 months, as well as the studies on the drained plots of ChNPP CP bed. The method of successive extractions was used to analyze the radionuclides containment forms. The record of successive extractions is presented below (Table 6.5).

Table 6.5 – Stages of successive leaching of radionuclides from the samples of the ChNPP CP bottom deposits and their associated forms No. Reagent and leaching conditions Forms of radionuclides I distilled water; 24 hours at 20 0С and periodical stirring water-soluble

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0 II 1 М CH3COONH4 (NH4Ас); pH 7; 24 hours at 20 С exchangeable III 1 М HCl; 24 hours at 20 0С mobile IV 0.2 М (NH4)2C2O4 + 0.1 М H2C2O4 (Tamm's solution); pH associated with amorphous oxides 3,2; 2 hours at 20 0С and hydroxides of Fe and Al in the form of organo-mineral complexes 0 V 8 М HNO3; 24 hours at 20 С of low solubility and associated with fuel particles (UхOу) VI Residue after i.5 was ashed at 550 С during 6 hours with associated with organic components further processing by mixture of acids 8 М HNO3  10 М of bottom deposits and fuel HCl during 2 hours at 95 С particles (UO2) VII Residue after i.6 was leached by mixture of acids: 8 М firmly fixed on mineral components HNO3  4 М HF during 2 hours at 95 С of bottom deposits and as a part of structural fuel particles (UxZyOz) VIII insoluble residue

Studies on the experimental site. The analysis of water-soluble radionuclide forms’ dynamics in bottom deposits of the ChNPP CP on the experimental site after their drying and exposure in field conditions during 47 months (Figure 6.7) indicates their slight increase for 90Sr (up to 5- fold), but the absolute value of their increase in water-soluble fraction is insignificant (up to 0.6% of the gross content). For other radionuclides, the content of water-soluble forms did not change significantly during the experiment and remained extremely low (<0.1% of the gross content) [237].

The analysis of acetate leaches from the modified bottom deposits of the ChNPP CP, which were taken on the experimental site, indicates an increased contribution of exchangeable forms for 90Sr, between 1% and 10% of the gross content during 47 months. For other radionuclides, the content of exchangeable forms did not change significantly and was below 5% of the gross content.

The analysis of dynamics of acid-soluble mobile forms of radionuclides in modified bottom deposits of the ChNPP CP indicates their increase for 241Am, between 15% and 35% of the gross content. For other radionuclides, no statistically significant dynamics of mobile forms of radionuclides was detected on the experimental site.

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Figure 6.7 – Relative distribution of 137Cs, 90Sr, 239,240Pu and 241Am activity in the leaches of sequential extractions of samples of the ChNPP CP bottom deposits at the baseline (t = 0) and after in-field drying and exposure during 9, 15, 26, 47 months

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The approximation parameters for statistically reliable results of the growth dynamics of radionuclide forms on the experimental site are presented below (Table 6.6).

Table 6.6 – Approximation parameters of the growth dynamics (% of gross content) of radionuclide forms in modified bottom deposits of the ChNPP CP after simulation of their drying and exposure in the field conditions on the experimental site during 47 months

Radionuclide Forms of radionuclides Equation Correlation, R2 90Sr Water-soluble А (%)=0.0082·t(months)+0.1743 0.83 90Sr Exchangeable А (%)=0.1613·t(months)+2.5975 0.6 241Am Mobile А (%)=0.4113·t(months)+15.64 0.9

Consequently, in addition to the growth of water-soluble and exchangeable forms of 90Sr and acid-soluble mobile forms of 241Am in the modified bottom deposits of ChNPP CP after the simulation of their drying and exposure in the field conditions during 47 months, concentrations of other forms of 137Cs, 90Sr, 239,240Pu and 241Am did not demonstrate statistically significant changes in comparison to the initial forms of radionuclides in the ChNPP CP bottom deposits.

The determining factor that impacts the rate of radionuclides leaching from fuel particles is pH of medium. The acidity of medium on the experimental site remained weakly alkaline during 47 months. Obviously, this is the main reason for the low ratio of radionuclides leaching from fuel component in the modified bottom deposits of ChNPP CP.

Investigations on the drained plots of ChNPP CP. Visual analysis of the drained plots indicates that composition of bottom soils differs greatly; from pure sand (losses on ignition are fractions of a percent) to silted sand (losses on ignition are up to 40%). The concentrations of 137Cs, 90Sr, 239 + 240Pu and 241Am mobile forms in sandy soils considerably exceed the concentrations in silted sand. The content of 90Sr exchangeable forms in bottom soil ranges between 5 and 50% of the gross content at different sites of the ChNPP CP. Obviously this is due to different content of organic component in the bottom soil. A share of radionuclides that was leached out of the fuel component during almost 30 years was fixing on organics, thus forming complex compounds. It is known that the ChNPP CP soils were originally represented by sands (32% of the total area), primary soils (43%) and silt (25%). Therefore, the distribution of bottom soil characteristics over the bed area should be taken into account in predictive estimates of the dynamics of radionuclide forms containment on the ChNPP CP drained plots. In contrast to 90Sr, the nature of 137Cs distribution in bottom soil leaching at different points of the ChNPP CP is more comparable.

The analysis of 137Cs and 90Sr specific activity dynamics in the leaves of willow shoots at reference points on the drained plots of ChNPP CP did not reveal any significant increase in the contamination. This may indicate a minor dynamics of the radionuclides mobility in soil on the ChNPP CP drained plots.

Field observations indicate a rather dynamic rate in the overgrowth of the ChNPP CP drained plots. In the silt particles alluviums, the first vegetation appears as early as a few weeks after draining. The basic plants include grass and willow and poplar shoots. In a year after drainage, only open beach stretches with clean sand still stay without vegetation cover.

If we extrapolate these results to the entire pat of the ChNPP CP subject to future drainage, the following predictive estimates can be made: ✓ A sharp increase in the mobility of radionuclides should not be expected on the ChNPP CP dried plots in the next 3-8 years. The reason is a long-term preservation of weakly 145

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alkaline reaction of the bottom deposits and presence of fuel component in the ChNPP CP in the form of chemically stable fuel particles. Therefore, only that portion of radionuclides that are in their mobile forms can participate in the migration processes on the ChNPP CP drained plots (<30% of the gross content); ✓ A significant part of radionuclides activity is not leached from solid phase of the ChNPP CP bottom deposits, even after application of "super-hard" extraction conditions. This may indicate presence of 90Sr, 238,239,240Pu, 241Am and partially 137Cs in chemically very stable particles, and accordingly this radionuclide fraction cannot be mobilized for many decades under natural conditions; ✓ The most of fuel component activity, at least in the ChNPP CP north part, is concentrated in individual fuel particles of 10-30 μm size, accordingly the dynamics of radionuclide mobility in the ChNPP CP drained plots shall be guided by the processes of radionuclides destruction and leaching from the particles of this size; ✓ The results indicate presence of a considerable spatial heterogeneity of radionuclide containment forms on the ChNPP CP bed territory. This may be due either to different agrochemical characteristics of the bottom soil, and to different superposition in the composition of fuel component matrix in the initial radioactive contamination and should be additionally investigated; ✓ There is quite a positive dynamics in overgrowing of the ChNPP CP dried plots, which will continue in future.

6.3.1 Transformation coefficients of the Chornobyl fuel component in the ChEZ water bodies During the accident’s active phase, such radionuclides as 241Am, isotopes of plutonium and europium, significant part of cesium isotopes and large majority of 90Sr and 106Ru could have penetrated into the ChEZ water bodies exclusively in the form of finely dispersed particles of irradiated accidental nuclear fuel with uranium oxide matrix of different oxidation states and in structural materials. Being encapsulated in FP matrix, these radionuclides could not penetrate into the components of aquatic ecosystems at the initial moment.

Investigations of FP behavior in soils and reference media, including liquids, demonstrated that the main factors responsible for radionuclides leaching from the fuel component were composition of uranium oxide matrix, its oxidation degree and acidity of medium. Therefore, the dynamics of FP destruction and radionuclide leaching from them to aquatic systems should be subject to the general patterns of FP behavior in the environment. Research results for radionuclides leaching from real FP in reference solutions prove this. Generally, the process of fuel particles dissolution in a water column can be described by the first-order kinetic equation: dA/dt= (k+λ)A, FP=A(t)/(A0exp(-λt))=exp(-kt), where A(t) and A0 are activities of particles at time t after the dissolution start and at the initial moment, respectively; k – FP transformation invariant, year-1; λ – radionuclide decay invariant, year-1; FP – share of undissolved FP at time t.

Similarity in the parameters of the radioactive fallout’s dispersed composition distribution within the near zone around ChNPP allows us to compare destruction processes in the Chornobyl fuel component in various ecosystems of the exclusion zone, since the destruction rate shall depend only on the composition of fuel particle matrix and on characteristics of the medium, while the differences in the dispersed composition of FP can be neglected. It is also important that radionuclide composition and radionuclides ratio for the most FP that have fallen in the near

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Therefore, the task of retrospective assessment of radionuclide intake dynamics from FP to a water column generally is reduced to determining contributions of various types of FP (as for chemical resistance) to gross contamination and medium pH. As is known, water bodies in the exclusion zone have a weakly alkaline reaction. For example, pH of the ChNPP CP bottom deposits ranges between 7.1 and 7.4; and its water ranges between 7.5 and 8.2.

The analysis results for the radionuclides leaching dynamics out of real and model fuel particles in media with different pH allowed to obtain dependencies for the transformation coefficients of oxidized and unoxidized FP in water bodies of the exclusion zone (Figure 6.8). Accordingly, for unoxidized Chornobyl fuel particles with UO2 matrix: k (year-1)=0.0063·рН2-0.0786·рН+0.2526, and for oxidized Chornobyl fuel particles with UхOу matrix: k (year-1)=0.0465·рН2-0.6004·рН+2.1402

k, рік-1 1 UO2 матриця UxOy матриця

y = 0.0465x2 - 0.6004x + 2.1402 0.1 R² = 1

y = 0.0063x2 - 0.0786x + 0.2526 0.01 R² = 1

0.001 4 5 6 7 8 9 10 рН

Figure 6.8 – Dependency of transformation coefficient of oxidized and unoxidized Chornobyl fuel particles on pH of medium

These dependencies can be used for retrospective assessments of radionuclides leaching dynamics from Chornobyl FP in aquatic systems of the exclusion zone.

6.4 Expected effective exposure doses for population ( “self-settlers) in population centers within the ChEZ

The experience gained after the Chornobyl accident showed that the density of area contamination with radionuclides does not clearly correlate with expected doses of internal exposure to the population (“self-settlers”). Basing on the data on radionuclide contamination density in the area (Figure 6.4- Figure 6.6), a long-term forecast of average annual effective exposure doses ( Dtotal(t) , AED) that can be obtained by critical groups of the population/self- settlers (a representative individual) while living and carrying out traditional economic activities in the ChEZ, was made for 2017, 2117 and 2517:

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Dtotal(t) = De x t (t) + Dint (t) (6.1)

where De x t (t) and Dint (t) are expected effective doses from external and internal exposures.

The maximum values of dose factors and parameters of radionuclide intake into a human body were used for the conservative estimates (Table 6.1).

6.4.1 External exposure doses

The effective dose rate of an adult’s external gamma exposure from radionuclides Pext (μSv/h) contained in a 5-cm soil layer was calculated as follows: 6 P  i  i , (6.2) ext  As Bs i1 where i1 is the dose factor equal to the ratio of EDR and contamination density of a 5-cm soil Bs i layer by the i-th radionuclide ( As ) in the open area – Table 6.1.

The expected effective dose of a representative individual’s external gamma exposure from radionuclides Dext (μSv) contained in a 5-cm soil layer during a 1-year exposure time t=8760 hours shall be:

Dext (t) 1.8 Pext t 0.3, (6.3) where 0.3 is the factor of the villagers’ behavior mode in Ukraine; 1.8 is the ratio between the external effective dose of a representative individual and the average exposure dose to population in a settlement after the Chornobyl accident [238].

6.4.2 Internal exposure doses

The expected effective dose of internal exposure Dint (μSv) due to peroral and inhalation intake of radionuclides by an adult representative individual over a year was calculated as follows:

Dint (t)  Dinj (t)  Dinh(t) (6.4)

The dose from the consumption of local foods was calculated based on their annual consumption and 137Cs and 90Sr concentrations: 4 4 137Cs 137Cs 137Cs 90Sr 90Sr 90Sr Pu Am Pu Am (6.5) Dinj(t)  3*(Binj  As Tf j  Pj  Binj * As Tf j  Pj  Binj 8 As m) j1 j1 where i is the dose factor equal to the expected effective dose due to peroral intake of 1 Bq of Binj the i-th radionuclide to an adult body, μSv/Bq – Table 6.1; i Tf j is the effective transition coefficient (TC) of the i-th radionuclide to the j-th product for sod-podzolic sandy soil typical of the ChEZ, and Pj is annual consumption of the j-th product, which amount to: (Bq/kg)/(kBq/m2) Milk Meat Potatoes and vegetables Mushrooms 137Cs 2 0.2 0.4 0.06 13 Tfi ,( Bq/kg )/(kBq/m )

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90Sr 2 0.4 0.2 0.2 0.2 Tfi , ( Bq/kg )/(kBq/m )

2 130 42 180 4 Pi , (kg/year)

8 is the factor of conversion from radionuclide soil contamination density (kBq/m2) to the specific activity of a 10-cm layer of sod-podzolic sandy soil with a density of 1250 kg/m3; m=0.05 kg is the soil mass annually swallowed by an individual (NRBU-97/2000); 3 is the ratio between the internal effective dose of a representative individual due to peroral intake of radionuclides and the average exposure dose to population in a settlement after the Chornobyl accident [238].

The internal effective exposure dose due to inhalation intake of radionuclides was estimated for the most critical group (machine operators) in the following way: 6 D (t) 1E  6*V * i  i inh  As Binh , (6.6) i1 where V=2040 m3 is the volume of annually inhaled air during working hours by an adult; i Binh is the dose factor equal to the expected effective dose due to inhalation intake of 1 Bq of the i-th radionuclide into an adult body, μSv/Bq – Table 6.1.

1E-6 is the conservative value of wind lift (resuspension) coefficient for radionuclides in breathing area of machine operators during human impact on soil, and of fire fighters in case of meadow and forest fires in the ChNPP EZ [239,240,241].

Figure 6.9 shows corresponding maps of the expected AED to a representative individual in the ChEZ in 2017 (a) and in 2517. At present, the isoarea, where AED exceeds 5 mSv/year, is extending beyond the borders of 10-km zone in the west, north-west and south; while the dose limit of 1 mSv per year shall be exceeded after 500 years (Fig. 6.9).

Based on the obtained predictive estimates of exposure doses, it can be concluded that the routine and scientific radiological monitoring in population centers within the ChEZ should be carried out further and for a long time.

2 CM of Ukraine No. 656 dated 14 April 2000. 149

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b Figure 6.9 – Predicted AED fotor a representative individual in the ChEZ in 2017 (а) and in 2517 (b)

6.5 Predicted contamination of agricultural and forest products

With adherence to the radiation protection requirements for personnel, a limiting factor for economic use of radioactively contaminated areas is compliance of radionuclide concentrations 150

Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone in products with national hygienic standards. Currently, the "Permissible levels of 137Cs and 90Sr radionuclide concentrations in foods and drinking water (DR-2006)" [242] and "Hygienic standards of specific activity of 137Cs and 90Sr radionuclides in wood and wood products (GNPAR-2005)" are in force in Ukraine [243].

Radionuclide concentrations in products depend on contamination density in the area (Figure 6.4, Figure 6.5), soil-climatic conditions and product type (Table 6.7) [228]. For sod-podzolic soils with light mechanical composition, which are the most typical in the ChEZ, wild mushrooms and berries are most critical as for the risk of exceeded permissible 137Cs concentrations, as well as beef and cow milk among agricultural products. As for 90Sr, the most critical products include food grains and vegetables (Table 6.7).

Table 6.7 – Permissible levels of radionuclide concentrations in products and transition 137 90 coefficients for Cs и Sr from sod-podzolic sandy and sandy loam soils, TC, TFag, ((Bq/kg)/(kBq/m2)) [228, 238] Permissible level (DR- Transition coefficients, Radionuclide Product 2006), Bq/kg ((Bq/kg)/(kBq/m2)) Wild 500 5-20 mushrooms Wild berries 500 2-20 Beef 200 0.3-1 137Cs Milk 100 0.1-0.3 Vegetables 40 0.002-1 Potatoes 60 0.04-0.08 Grain 50 0.002-0.7 Grain 20 0.01-7 90Sr Vegetables 20 0.02-5 Milk and beef 20 0.01-0.5

Based on the data on 137Cs and 90Sr contamination density and their TCs in the most critical products (Table 6.7), there were developed the schematic maps of the ChEZ areas, where probable outputs of products with radionuclide concentrations exceeding the permissible level exist currently and shall still exist in 100 years, in 2117 (Figure 6.10). The results obtained indicate that current concentrations of 137Cs can exceed DR-2006 in wild mushrooms and berries practically throughout the entire ChEZ, as well as in milk/beef in the 10-km zone and on the "cesium spot" outside it, near the village of Vesniane, on an area of approximately 440 km2. Current concentrations of 90Sr in grain can exceed the hygienic standard for food grains (20 Bq/kg) throughout the ChEZ, this is also observed in its adjacent regions and ouside the ChEZ [244]. In 100 years, in 2015, contamination with 137Cs exceeding DR-2006 shall be mainly observed within the 10-km zone only, on an area of approximately 460 km2; and 90Sr concentrations in grain may also exceed the permissible levels outside it, on a total area of approximately 800 km2 (Figure 6.10).

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Figure 6.10 – Predicted borders of the area, where exceeded permissible levels for 137Cs concentrations in milk and wild mushrooms and for 90Sr concentrations in food grains (DR- 2006) are expected within the ChEZ in 2017 and in 2117

Based on the obtained predictive estimates of radioactive contamination of products, it can be concluded that the routine and scientific radiological monitoring in population centers within the ChEZ should be carried out further and for a long time.

6.6 Predicted contamination of wood in the ChEZ

The strictest requirements for 137Cs and 90Sr concentrations in wood and wood products (GNPAR-2005) are applied to firewood and fuel bundles: 600 Bq/kg and 60 Bq/kg [243]. To estimate wood radioactive contamination within the ChEZ, a layer with regular network of values for the extrapolation of radionuclide contamination density in the area was designed on the map of "Pivnichna Pushcha" (North Forest), basing on experimental sampling data (Figure 6.1). The map and point coordinates were put into UTM Mercator projection uniform coordinate system (WGS 84), zone 36, Northern hemisphere. The values of 90Sr and 137Cs contamination densities were recalculated, taking into account radioactive decay of the radionuclides in different years (Table 6.1). A certain quantity of extrapolation points was assigned to each forest site, depending on its area. The sites’ average contamination values were calculated based on arithmetic averages for site points. Using the maximum values of 137Cs and 90Sr TC to wood in the ChEZ conditions, i.e. 2 and 17 ((Bq/kg)/(kBq/m2)), respectively; each site, where the radionuclide concentrations may exceed GNPAR-2005 hygienic standards in 2020-2100, was assessed (Figure 6.11 – Figure 6.20).

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At present and in the near future, 90Sr concentrations in the fuel wood may exceed the permissible levels practically throughout the entire ChEZ and even outside it [245] (Figure 6.16); and even in 100 years, such a hazard shall still remain outside the 10-km zone (Figure 6.20). Unlike 90Sr, in 100 years 137Cs concentrations in the wood shall comply with GNPAR-2005 in the most part of ChEZ (Figure 6.15) [243].

Based on the obtained predictive estimates for the wood radioactive contamination, it can be concluded that the routine and scientific radiological monitoring of forest ecosystems should be carried out further and for a long time.

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Figure 6.11 – Predictive estimates of 137Cs specific activity in wood within the ChEZ in 2020

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Figure 6.12 – Predictive estimates of 137Cs specific activity in wood within the ChEZ in 2030

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Figure 6.13 – Predictive estimates of 137Cs specific activity in wood within the ChEZ in 2040

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Figure 6.14 – Predictive estimates of 137Cs specific activity in wood within the ChEZ in 2050

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Figure 6.15 – Predictive estimates of 137Cs specific activity in wood within the ChEZ in 2100

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Figure 6.16 – Predictive estimates of 90Sr specific activity in wood within the ChEZ in 2020

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Figure 6.17 – Predictive estimates of 90Sr specific activity in wood within the ChEZ in 2030

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Figure 6.18 – Predictive estimates of 90Sr specific activity in wood within the ChEZ in 2040

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Figure 6.19 – Predictive estimates of 90Sr specific activity in wood within the ChEZ in 2050

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Figure 6.20 – Predictive estimates of 90Sr specific activity in wood within the ChEZ in 2100

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6.7 Predicted air contamination in the ChEZ

Prior to the start of water drainage from the ChNPP CP, predictive estimates for increases in ground level concentrations of radioactive aerosols were made for the surface air on the ChNPP industrial site and in the town of Chornobyl for the case of multi-year averaged meteorological parameters (Scenario No.1) and for extreme situations such as dust storms (Scenario No.2) and vegetation fires on the cooling pond’s drained areas (Scenario No.1) – Table 6.8. Table 6.8 shows averaged estimates of additional fallout density and air concentrations of the considered radionuclides at a height of 1 m and of expected additional effective inhalation dose (50-year EED) to the ChEZ personnel, Chornobyl town (five points, evenly spaced throughout the town) and the ChNPP industrial site area (six points located 25-200 m from the cooling pond’s boundary).

The minimal contamination densities of 137Cs and 90Sr in the areas adjacent to the cooling pond are approximately 100-200 kBq/m2; for 238-240Pu and 241Am they are approximately 4.0 kBq/m2 (Figure 6.1). At the same time, the maximum secondary area contamination near the ChNPP shall be observed for 137Cs and 90Sr in the case of grass fires (55-58 Bq/m2), but even in this case it is shall be 1500-3000 times lower if compared to the minimum level of radioactive contamination currently existing around the CP (Table 6.8). For all the considered scenarios, additional area contamination with 137Cs, 90Sr, 238,240Pu and 241Am shall be substantially lower than the current area contamination with these radionuclides and shall not pose a hazard.

If we compare the obtained estimated air concentrations of radionuclides during the exposure time (5 days) and during one year to the reference levels accepted in the ChNPP EZ [194], then exceeded RL can be observed for the following(Table 6.8): • near the ChNPP and in Chornobyl town, for air concentrations of 137Cs and 90Sr during the exposure time (5 days) – in case of a grass fire; • in Chornobyl town, for the air concentrations of 137Cs and sum of transuranium elements (TUE, activities of 238-241Pu and 241Am are incorporated) during the exposure time (5 days) – in case of a dust storm; • in Chornobyl town, for average annual air concentrations of 137Cs and 90Sr – in case of a grass fire.

It should be noted that all these cases of exceeded reference levels for the air concentrations of radionuclides are of episodic nature and occur under extreme conditions. Such excesses of reference levels for the air concentrations of radionuclides are also periodically observed in the Chornobyl NPP exclusion zone now, during dust storms and forest fires.

From the beginning of the ChNPP CP water drawdown, since the autumn of 2014, no dust storms and fires were observed in the CP drained areas [according to http://rp5.ua/]. In 2016- 2017, the wind speed did not exceed 5 m/s, and the stocks of plant flammable material on the drained plots of bottom deposits are still too small for a development of a strong fire in the CP area.

Experimental data on radionuclide concentrations in the air in 2008-2014 (before the CP water drawdown) and since 2016 till October 2017 (during the CP water drawdown) were obtained by the SSE “Ecocenter” (Table 6.9) from the monitoring network in the town of Chornobyl and near the ChNPP industrial site. The maximum values of annual average and 5-day average aerosol sample taken to estimate surface air concentrations of 137Cs in 2008-2013, before the CP water drawdown, near the

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ChNPP industrial site and the town of Chornobyl [247] were 2-10 times lower compared to the monitoring data of 2016, after the CP water drawdown in 2016 (Table 6.9). This was due to both weather conditions and a fire in the "Red Forest" (the most radioactively contaminated part of ChEZ) in 2016, as well as due to human induced contamination of the ChEZ air (Figure 6.21) caused by the activities for New Safe Confinement (NSC) construction before November 2016. In 2016, the maximum average 5-day radionuclide concentrations in the air were not linked to re-suspension of radioactive aerosols from the drained plots of CP bottom deposits, since they were observed at control points in windless or quiet-wind conditions, at the wind speed below 1 m/s and not from the direction of the ChNPP CP (Table 6.9): Measurement interval for Wind [per http://rp5.ua/ ] Control maximum air concentrations Wind During the sampling, wind blew from point of radionuclides speed the following directions (North, East, South, West) VRP-750 30.08-03.09.2016 1 m/s NNW, WNW, ENE Naftobaza 10-15.8.2016 1 m/s ENE, W Chornobyl 1-5.09.2016 1 m/s NNW, WNW, WSW, SSW,

During 2016, air concentrations of radionuclides throughout the zone were increasing due to the NSC activities and were maximal, if compared to 2017 and the years preceding the CP water drawdown. After the NSC was slided onto the sarcophagus, the radionuclide concentrations have decreased significantly at all control points, and this is especially well demonstrated by the data of 2017 (Table 6.9). Despite the increased area of CP drained plots in 2017, the maximum annual average and 5-day average air concentrations of radionuclides decreased 3-10 times compared to 2016 (Table 6.9), which confirms the correctness of predictive estimates and absence of a significant contribution from drained bottom deposits to existing radioactive contamination of the ChEZ air, which is caused by other sources (radioactive contamination of soil, man-made elevation of dust, etc.). Predictive estimated increases in air concentrations of radionuclides under averaged standard weather conditions (Scenario No.1) were 10-100 times lower than the actual values in 2017, and up to 100-1000 times lower than the maximum 5-day air concentrations of radionuclides (Table 6.9). Against the background of fluctuations and measurement accuracy, this prevents a reliable experimental identification of the contribution made by re-suspension of radionuclides from drained plots of bottom deposits to existing radionuclide concentrations at the reference points. Basing on the experimental data obtained by the SSE ChNPP RSS and the SSE "Ecocenter" in 2016-2017, it was concluded that the volumetric activity of radionuclides in the surface air during the cooling pond decommissioning did not cause additional internal inhalation exposure doses to the personnel staying on the ChNPP industrial site, and even more so in the town of Chornobyl. For example, there was a fire of meadow and woody vegetation in the most radioactively contaminated part of the ChEZ, on the area of 300 hectares (in the so-called Red Forest), with the wind directions to the west and south on 15-18 July 2016. It resulted in increased 5-day air concentrations of radionuclides at Chystohalivka control point (located several kilometers south of the fire) by two orders of magnitude (up to 4E-3 Bq/m3 for 137Cs and 3.2E-3 Bq/m3 for 90Sr), if compared to the average annual levels (Figure 6.21). On 17 July 2017, the surface concentrations of 90Sr, 137Cs, 238-240Pu and 241Am near the fire front amounted to 1 Bq/m3, 0.2 Bq/m3, 2.5E-3 Bq/m3 and 9.9E-3 Bq/m3, respectively [246]. These results are consistent with the conservatively estimated excess of radionuclide volumetric concentrations on the ChNPP industrial site in the event of a grass fire on the CP (137Cs  3.5E-2 Bq/m3 and 90Sr 1.6E-2 Bq/m3) for 5 days of measurements (Table 6.9). 165

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Table 6.8 – Predicted additional radiation loads to the plots typical of ChEZ after the CP water drawdown RL, RL, Chornobyl Chornobyl Characteristics Scenario ChNPP Zone 1: 10 km town town near ChNPP

No.1 6.4 0.08 Additional density of fallouts, 137Cs, Bq/m2 No.2 37 5 200000 3 No.3 58 12 No.1 1.5 0.02 Additional density of fallouts, 90Sr, Bq/m2 No.2 7.4 1.1 100000 3 No.3 55 8.5 No.1 0.07 8.8E-4 Additional density of fallouts, 238-240Pu, No.2 0.33 0.047 4000 Bq/m2 3 No.3 4.5E-4 7.8E-5 No.1 0.08 0.001 Additional density of fallouts, 241Am, Bq/m2 No.2 0.4 0.057 4000 3 No.3 7.5E-3 1.2E-3 No.1 1.3E-5 2.3E-7 Average volumetric activity of 137Cs in the No.2 8.7E-4 1.2E-4 1E-2 8E-5 air at a height of 1m for 5 days, Bq/m3 No.3 0.035 0.005 Average volumetric activity of 90Sr in the No.1 3E-6 5.6E-8 air at a height of 1m for 5 days, Bq/m3 No.2 1.7E-4 2.6E-5 3E-3 4E-5 No.3 0.016 0.0025 No.1 1.3E-7 2.4E-9 Average volumetric activity of 238-240Pu in No.2 7.5E-6 1.2E-6 the air at a height of 1m for 5 days, Bq/m3 No.3 2.3E-7 3.6E-8 2E-3 4 3E-5 4 No.1 1.6E-7 2.9E-9 Average volumetric activity of 241Am in the No.2 9.1E-6 1.4E-6 air at a height of 1m for 5 days, Bq/m3 No.3 3.5E-6 5.5E-7 No.1 1.3E-5 2.3E-7 Average annual volumetric activity of 137Cs No.2 1.2E-5 1.6E-6 1.7E-3 2.7E-5 in the air at a height of 1m, Bq/m3 No.3 4.7E-4 7.5E-5 Average annual volumetric activity of 90Sr No.1 3E-6 5.6E-8 in the air at a height of 1m, Bq/m3 No.2 2.4E-6 3.5E-7 5E-4 1.2E-5 No.3 2.2E-4 3.3E-5 No.1 1.3E-7 2.4E-9 Average annual volumetric activity of 238- No.2 1E-7 1.6E-8 240Pu in the air at a height of 1m, Bq/m3 No.3 3.1E-9 5.0E-10 3E-4 4 1.1E-5 4 No.1 1.6E-7 2.9E-9 Average annual volumetric activity of No.2 1.2E-7 1.9E-8 241Am in the air at a height of 1m, Bq/m3 No.3 4.8E-8 7.5E-9 No.1 0.52 0.02 Additional inhalation 50-year EED for No.2 3.0 0.34 3000 700 personnel, µSv No.3 1.9 0.3

3 Minimum contamination density of the area around ChNPP CP 4 As a part of TUE, 238-241Pu, 241Am are taken into account (current ratio is 241Pu/238-240Pu= 46) 166

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Table 6.9 – Radionuclide concentrations at the ChEZ control points at standard weather conditions, before and after the change of the ChNPP CP water level, Bq/m3

Prior to the water level change in 2008- Predictive estimates After water the CP drawdown5 2014 [247] for Scenario 1 (Table Near ChNPP Chornobyl

de 6.8)

Near ChNPP Chornobyl ChNPP Chorno 2016 2017 2016 2017 Parameter Radionucli byl 137Cs 2.5E-3 ( ВРП-750) 2.2E-5 1.3E-5 2.3E-7 3.6E-3 (VRP-750) 1.2E-3 (VRP-750) 3.6E-5 2.0E-5 6.1E-4 (Naftobaza ) 8.7E-4 (Naftobaza ) 3.0E-4 (Naftobaza ) 1.7E-4 ( CWI-3) 2.9E-4 ( CWI-3) 1.5E-4 ( CWI-3) 90Sr 3E-6 5.6E-8 1.2E-3 (VRP-750) 4.0E-4 VRP-750) 1.4E-5 5.0E-6

3.9E-4 (Naftobaza ) 1.3E-4 ( Naftobaza )

at a height of height at a

volumetric 8.9E-5 ( CWI-3) 5.0E-5 ( CWI-3)

238-240Pu 1.3E-7 2.4E-9 4.6E-5 (VRP-750) 7.0E-6 ( VRP-750) 1.9E-7 6.0E-8 5.5E-6 (Naftobaza ) 1.6E-6 ( Naftobaza ) 1.8E-6 ( CWI-3) 6.0E-7 ( CWI-3) 241Am 1.6E-7 2.9E-9 7.3E-5 ( VRP-750) 2.0E-6 ( VRP-750) - -

1.7E-5 ( Naftobaza ) 7.0E-7 ( Naftobaza )

activity in the air 1 m Average annual - 4.0E-7 ( CWI-3) 137Cs 2.1E-2 (ВРП-750) 9.2E-5 1.3E-5 2.3E-7 4.4E-2 (VRP-750) 4.4E-3 (VRP-750) 7.0E-4 2.3E-4 4.7E-3 (Naftobaza ) 1.1E-2 (Naftobaza ) 1.3E-3 ( Naftobaza ) 4.5E-4 ( CWI-3) 4.4E-3 ( CWI-3) 5.9E-4 ( CWI-3) 90Sr 3E-6 5.6E-8 1.1E-2 (VRP-750) 1.5E-3 (VRP-750) 1.9E-4 1.8E-5

3.9E-3 ( Naftobaza ) 4.0E-4 ( Naftobaza )

1.2E-3 ( CWI-3) 1.8E-4 ( CWI-3)

5 days

238-240Pu 1.3E-7 2.4E-9 6.6E-4 ( VRP-750) 4.7E-5 ( VRP-750) 2.4E-6 5.4E-7 for 7.0E-5 ( Naftobaza ) 7.0E-6 ( Naftobaza )

2.6E-5 ( CWI-3) 2.6E-6 ( CWI-3)

volumetric activity the in air at

241Am 1.6E-7 2.9E-9 8.0E-4 ( VRP -750) 7.5E-5 ( VRP -750) 9.2E-6 -

1.5E-4 ( Naftobaza ) 3.6E-5 ( Naftobaza ) a a height of 1 m Average 5.0E-5 ( CWI -3) 1.7E-5 ( CWI -3)

5 Monitoring data from SSE “Ecocenter” 167

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b Figure 6.21 – Surface air concentrations of radionuclides for 5 sampling days in the town of Chornobyl (a) and at Chystohalivka control point (fire in the "Red Forest", which is the most contaminated part of the ChEZ, occurred on 15-18 July 2016)

i 90 137 Density of area contamination by the i-th radionuclide ( As , where i=1 for Sr, i=2 for Cs, i=3 for 238Pu, i=4 for 239Pu, i=5 for 240Pu, i=6 for 241Am – Table 6.1) at a specific time point prvide basic source data for assessing the radioactive contamination levels of flammable material and air, as well as for calculating equivalent dose rate of external exposure and effective doses of internal exposure due to inhalation intake of radionuclides during forest and meadow fires. Currently, forest litter can contain up to 50% of 90Sr and 137Cs activity and up to 1% of alpha- emitting radionuclides (238Pu, 239Pu, 240Pu, 241Am), which are the most hazardous in terms of inhalation intake. Based on the data on radionuclide contamination density in the area, radionuclides TC to different parts of stand (bark, branches, needles/leaves) and wood stocks on each site, radionuclide concentrations in flammable material were estimated. Using the URIAR’s experimental research results on the estimated radionuclide outflows and radiological hazard of meadow/forest fires in the ChNPP EZ [240,241], the expected effective doses of external and internal exposure to fire fighters were estimated for various types of fire and classes of fire

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Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone hazard [248]. The largest outflow of radionuclides occurs with intense top forest fires, when up to 98% of needles and leaves, 87% of branches, 67% of bark and 82% of litterfall burn up.

The estimates shown that currently, even during top forest fires in the ChEZ, the expected effective dose of exposure due to radioactive aerosols intake by fire fighters through their respiratory organs (use of personal protective equipment excluded) shall not exceed the dose of external exposure during fire fighting and therefore shall not be of any hazard.

In case of fires in the most severely contaminated forest sites near the population centers of N. Shepelychi, Leliv, Chystohalivka, Kopachi, Buriakivka, etc., the additional effective doses to the staff (ChNPP, Vector Complex and Chornobyl town) shall not exceed 10 μSv, and for population they shall be below 2 μSv at the ChEZ border. Therewith, additional contamination of the area due to secondary wind transfer of radionuclides shall not exceed 0.n% of the current level for 90Sr and 137Cs, as well as 0.00n% for plutonium isotopes [249, 250].

From the viewpoint of additional doses accumulation by personnel and a representative individual and migration of radionuclides outside the ChEZ, long-term forecast for radioactive contamination of vegetation, flammable materials and air in terms of assessing the radiological hazard of forest fires in the near zone around ChNPP indicated that these are not critical for changing the network and rules of air monitoring.

The intensity of radionuclide fallouts is determined by their re-suspension from the adjacent local area and varies within the limits of natural fluctuations due to the secondary transfer of radionuclides from sites, located farther than 1 km from forest fires and dust storms. In this regard, monitoring of intensity radioactive fallouts yields little information related to radiation protection and prediction of changes in radiation situation within the ChEZ.

The obtained results demonstrate that once the NSC construction is completed, significantly increased radionuclide concentrations in the surface air should not be expected, even in extreme situations such as forest fires, dust storms, etc. Nonetheless, the monitoring of radionuclide concentrations in the surface air should be continued, since its results are of great socio-psychological importance. The network of control points should be expanded to the ChEZ peripheries towards the largest centers of population (Ivankiv, Kyiv, etc.), as well as to the sites under construction, which are potential sources of radionuclide releases.

It should also be noted that special attention needs to be given to the on-line monitoring of air concentrations of radionuclides in personnel breathing zones during extreme situations, such as fire extinguishing or works resulting in an increased elevation of dust.

6.8 Predicted contamination of surface and ground waters in the ChEZ

Results of the last 10-20 years of monitoring demonstrate an extremely slow decrease in radionuclide concentrations in the ChEZ surface waters, which is mainly due to radioactive decay of 90Sr and 137Cs (Figure 6.22). All conservative predictive estimates indicate absence of a radiological hazard of radionuclide migrations with groundwater from the RWTLS [196,203] and other man-made facilities within the ChEZ in future [251, 252].

Nonetheless, monitoring of radionuclide concentrations in the surface and ground waters should be continued, since its results are of great socio-psychological importance. The network of control points for the surface waters should be concentrated at the ChEZ border. Monitoring of the groundwater requires special attention along the streams from the facilities, 169

Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone which constitute potential sources of radionuclide intake, and towards the points located near their potential entry to the surface waters of the Pripyat River.

Figure 6.22 – Average annual levels of specific volumetric activity of radionuclides in the waters of the Pripyat River (a) and of the Hlyboke Lake (b) [5]

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7 PROCESSING AND PRESENTATION OF THE OBTAINED RESULTS TO THE DATABASE FOR DECISION-MAKERS AND INFORMATION OF THE PUBLIC

Currently, the results of both routine and scientific monitoring in the ChEZ are stored on paper and electronic media and in different formats by organizations of different departmental subordination, which complicates their usage by the world scientific community, decision- makers and public information. Such a situation requires systematization of data, verification of their quality and uncertainties, data unification in order to design the structure and develop the Database for decision-makers and public information.

Within the framework of the IAEA project RER/3/004 "Radiological Support for the Rehabilitation of the Areas Affected by the Chornobyl Nuclear Power Plant Accident" (2007- 2011), an electronic register of high-level contaminated areas was developed and can become a basis for the generation of an integrated unified database on the results of monitoring within the ChEZ. The monitoring objects may include fallows, natural meadows, forests, water bodies, surface and ground waters, air, man-made facilities, various organisms, etc.

To date, we upgraded "CH_PUSHA" database using MS Access 2000 for ChEZ forest ecosystems. Its master table includes over 48,000 records on all sites in the forestry quarters of the "Pivnichna Pushcha” (North Forest) (number and area of each site, land category, etc.) and contains data on forest inventory: prevailing tree species; composition and productivity of stand; forest bonitet and type; age, height, diameter and density of tree growth, wood stock per a unit of area and on an entire site, etc. (Figure 7.1).

A layer with a regular network of values for the extrapolation of radionuclide area contamination density based on experimental sampling data was designed on the map of "Pivnichna Pushcha” (North Forest) [229, 230]. The map and coordinates of extrapolation points were put into a uniform coordinate system UTM Mercator projection (WGS 84), zone 36, Northern hemisphere. Each forest site had a certain quantity of extrapolation points, depending on its area. The value of average contamination density of radionuclides (137Cs, 90Sr, 238Pu, 239Pu, 240Pu, 241Am) on a site i 2 area ( As , kBq/m ) was calculated as the arithmetic mean for the point values on a site area/boundaries. Therefore, average contamination densities for 90Sr, 137Cs 238Pu, 239+240Pu and 241Am were determined for all forest sites using the calculations (Figure 7.2). Further, the density of area contamination with 241Pu was calculated by the ratio to 239+240Pu activity as of 2015: Pu241 Pu239240 As / As 19 (Table 6.1).

The specific activity of the i-th radionuclide in the stand structural components was estimated based on information from "CH_PUSHA" Database: average density of a site soil contamination with the i-th radionuclide ( , kBq/m2) and maximum values of radionuclide transition i 2 coefficients ( Tf j,k ((Bq/kg)/(kBq/m ) from soil to dry k-th components of a stand (k=1 for wood, k=2 for bark, k=3 for branches less than 1 cm, k=4 for needles/leaves) for different species of j-th trees: j=1 for pine and j=2 for birch.

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Figure 7.1 – Fragment of a database table

Figure 7.2 – Map of “Pivnichna Pushcha” (North Forest) with a layer of 90Sr contamination density on each site 172

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8 PROPOSALS ON THE REVISION OF EXISTING SYSTEM OF ROUTINE AND SCIENTIFIC MONITORING

The main objective of the routine radiological monitoring is radiation protection of personnel and minimization of radionuclide migrations outside ChEZ to ensure radiation protection of people and the environment.

The main objectives of the scientific radioecological monitoring in the ChEZ is long-term forecast of changes in exposure doses to humans and biota inside and outside ChEZ, as well as in the case of potential nuclear and radiation accidents, based on verification of mathematical models of radionuclides behavior in the environment and the effects of ionizing radiation in biota in natural conditions.

In terms of their completeness (coverage of ecosystems, landscapes), adequacy (set of parameters), and representativeness of information on radionuclide concentrations and fluxes in monitored objects, the performance criteria of the routine and scientific monitoring system are guaranteed fulfillment of main objectives described above.

Based on the developed criteria and comprehensive analysis, a revision of the existing system of routine and scientific monitoring in the ChEZ is proposed from the viewpoint of its completeness (coverage of ecosystems, landscapes), adequacy (set of parameters), and representativeness of information on radionuclide concentrations and fluxes in monitored objects.

8.1 Routine minitoring

8.1.1 Air From the viewpoint of personnel radiation protection in the ChEZ in case of emergencies (forest fires, dust storms on the ChNPP CP drained plots, emergencies at the facilities, etc.), the system of routine monitoring of radionuclide air concentrations is adequate, however it should be optimized and modern certified equipment should be used.

The obtained results indicate that once the NSC construction is completed, significant increases in radionuclide concentrations in the surface air should not be expected, even in extreme situations such as forest fires, dust storms, etc. However, the monitoring of radionuclide concentrations in the surface air should be continued, since its results are of great socio- psychological importance. The network of control points should be expanded at the ChEZ peripheries, towards the largest centers of population (Ivankiv, Kyiv, etc.), as well as near the facilities under construction, which are potential sources of radionuclide releases.

It should also be noted that special attention needs to be given to the on-line monitoring of air concentrations of radionuclides in the personnel breathing zones during extreme situations, such as fire fighting or works resulting in an increased elevation of dust.

We believe that current scientific and technical level of the monitoring for the measurements of radionuclide concentrations in the air and intensity of radioactive releases is unfortunately not adequate. The system of routine monitoring for radioactive aerosol concentrations in the surface air and intensity of their release in the ChEZ should obtain relevant scientific guidance, modern equipment, training of personnel, as well as multi-agency and international verifications and calibrations.

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The number of observation points should be increased at the ChEZ periphery, with due regard for all potential sources of releases and dispersions of radioactive aerosols, as well as location of nearby population centers. Equipment and materials used for the sampling of radioactive aerosols should be upgraded, while meeting recent international requirements, certification and calibration are also required.

8.1.2 Surface waters Results of the last 10-20 years of monitoring demonstrate an extremely slow decrease in radionuclide concentrations in the ChEZ surface waters, which is mainly due to radioactive decay of 90Sr and 137Cs.

Only some observation points are responsible for the monitoring of radionuclide migrations outside the ChEZ by water for the purpose of public radiation protection. The rest of observation points should meet the objectives of scientific monitoring and should be consistent with the research conducted by other organizations to avoid duplication. For this purpose, the profile scientific organizations were surveyed.

8.1.3 Groundwater All conservative predictive estimates indicate absence of a radiological hazard of radionuclide migrations with groundwater from RWTLS and other man-made facilities within the ChEZ in future.

Only some observation points, including the RWTLS and RWDS, are responsible for the monitoring of radionuclide migrations with water outside the ChEZ for the purpose of public radiation protection. The rest of observation points should correspond to the tasks of scientific monitoring and should be coordinated with leading profile scientific organizations. For this purpose, we are currently conducting a survey of profile scientific organizations.

However, the monitoring of radionuclide concentrations in the surface and ground waters should be continued, since its results are of great socio-psychological importance. The network of control points for surface waters should be concentrated on the ChEZ border. The monitoring of groundwater requires special attention along the streams from those facilities, which are potential sources of radionuclide intake, and to the points located near their potential entry to the Pripyat River’s surface waters.

8.1.4 Population centers Basing on the obtained predictive estimates of exposure doses and radioactive contamination of products, it can be concluded that the routine and scientific radiological monitoring in population centers within the ChEZ should be carried out further and for a long time.

The routine monitoring should be carried out annually in accordance with Procedure-96 during various seasons of the year in order to assess effective exposure doses of people, while itemizing the diet of local residents and expanding the list of controlled foods. Special attention should be given to 90Sr, along with 137Cs. Expected exposure doses to the self-settlers should be verified based on radiation monitoring of external and internal exposure doses (WBC and measurement of 90Sr concentrations in urine).

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8.1.5 Terrestrial ecosystems Based on the obtained predictive estimates of radioactive contamination in the area and vegetation, it can be concluded that the routine and scientific radiological monitoring of the ChEZ terrestrial ecosystems should be carried out further and for a long time.

This type of monitoring is indirectly related to the radiation protection of personnel, it should be referred to the scientific monitoring and meet its objectives. In this regard, the network (coverage of ecosystems, landscapes) and regulations for the monitoring of forests and meadows were upgraded. At present, radiological situation in the ChEZ changes very slowly, therefore the intervals between measurements should be increased in order to obtain reliable differences. Basing on the models of radionuclide migrations in the environment, the observation regulations were improved.

Since 20% increase in 241Am activity in the next 50 years shall not significantly impact the changes in the formation of internal and external exposure inhalation doses of personnel and biota in the ChEZ, no changes to the approaches of americium-241 monitoring are required.

The measurements of dose rate in the areas with high contamination density of 137Cs and of the resulting gamma background cannot provide objective data on changes in the radiation situation (such as increased radionuclide volumetric activity in the air during fires). This can be addressed by means of collimators in order to reduce lateral illumination of gamma radiation from the ground.

8.2 Scientific monitoring

Since main objective of scientific monitoring in the ChEZ is long-term forecast of changes in exposure doses to humans and biota inside and outside ChEZ, as well as in the case of potential nuclear and radiation accidents based on verification of the mathematical models of radionuclides behavior in the environment and the effects of ionizing radiation in biota in natural conditions, then objects, network and regulations of the scientific monitoring should be determined by the relevant research priorities. To this end, the International Union of Radioecology has conducted a specific study to identify the first-priority tasks in radiology, which should be addressed to ensure radiation protection of humans and the environment at the present time. The research results demonstrated that directions of the scientific monitoring often do not correspond to the most crucial modern problems in radiology. For example, most of the monitoring efforts dealt with radionuclide migrations in the environmental objects, while those works are only a part of the absorbed doses assessment efforts. Therewith, much less attention was paid to the problems of reference organisms’ dosimetry, as well as to the obtainment of "dose-radiobiological effects" dependencies, especially at the levels of population and ecosystem.

The Chornobyl EZ was recognized by the world scientific community to be the main experimental site for radioecological researches under natural conditions. In this regard, the optimization of scientific radiological monitoring in the ChEZ should be based on the following task priorities:  Ionizing exposure effects in biota under natural conditions, at the levels of population and ecosystem, for the purposes of radiation protection of the environment;  Dosimetry of internal exposure of reference organisms under natural conditions;

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 Behavior of extra-long-lived and mobile radionuclides in the environment under natural conditions, on which there is a lack of reliable data, for example 36Cl, 99Tc, 129I;  Parameterization of source function and radionuclide migrations in case of forest fires and other extreme situations;  Characteristics, behavior in the environment, micro-dosimetry and radiological effects of fuel hot particles in organisms.

According to the task priorities and based on the availability of funding, continued works within the network of radiological scientific monitoring sites are planned in 2018 (Figure 5.1).

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1. On approval of the Regulations on the state system of environmental monitoring: Resolution of the Cabinet of Ministers of Ukraine dated March 30, 1998, No. 391, Kyiv, Source: http://zakon2.rada.gov.ua/laws/show/391-98-%D0%BF (in Ukrainian) 2. Hudkov I.M., Haichenko V.O., Kashparov V.O. Agricultural radioecology: Handbook Edited by I.M. Hudkov, Academician of the National Academy of Sciences of Ukraine, K.: Lira- K Publishing House, 2017, 268 p. (in Ukrainian) 3. Operating procedures of the SSE "Ecocentre" for the radiation and ecological monitoring, radiation and dosimetric control within the Exclusion Zone and Zone of Unconditional (Mandatory) Resettlement, K.: SAEZ, 2017, 56 p. (in Ukrainian) 4. Instructions on radiation and ecological monitoring during the ChNPP cooling pond decommissioning, 1E-OSE, K.: SAEZ, 2015, 33 p. (in Russian) 5. Ministry of Emergencies of Ukraine 2011. Twenty-five Years after Chornobyl Accident: Safety for the Future. National Report of Ukraine, KIM, Kyiv , 328 p. ISBN 978–966–1547–64–2 6. Haichenko V.A. Specifics of wild animals living in the conditions of radioactive contamination of biogeocoenoses. //Chornobyl. Exclusion Zone. //Naukova Dumka. Kyiv, 2001, p. 317-325. 7. Hashchak S.P., Zalisskii O.O., Buntova O.G. Fauna of vertebrate animals in the Exclusion Zone of Ukraine. // Preprint Kyiv-Chornobyl 2000 8 Instructions and methodological guidelines "Radiation and dosimetric passportization of population centers in the territory of Ukraine affected by the radioactive contamination, which has been caused by the Chornobyl accident, inclusive of thyroid dosimetric passportisation" (Procedure-96). Kyiv, 1996, 74 p. (in Ukrainian) 9. Dubas V.N., 2017. Radiation monitoring during the cooling pond decommissioning. Presentation of the Head of REM Laboratory, RSS, SSE ChNPP, at the workshop, 12 October 2017 (in Russian) 10. Fedor Lanskikh, 2017. ChNPP Cooling Pond under Decommissioning. SSE Chornobyl NPP, at the workshop, 12 October 2017 11. Results of routine monitoring of the SSE “Ecocentre”, S.I. Kirieiev, 2017 (in Russian) 12. Kozubov G.M., Taskaev A.I. 1994. Radiobiological and radioecological studies of tree plants / Ed. Nauka, St. Petersburg, 256 p. (in Russian) 13. Scheglov A. I., 2000. Biogeochemistry of technogenic radionuclides in forest ecosystems: on materials of 10-year researches from the zone impacted by the Chornobyl NPP accident / Ed. Nauka, Moscow, 268 p. (in Russian) 14. Mamikhin S.V., Tikhomirov F.A., Scheglov A. I., 1997. Dynamics of 137Cs in the forests of the 30-km zone around the Chornobyl nuclear power plant / The Science of the Total Environment 193, p. 169-177 15. Kopeikin V.A., 2005. Plutonium in wood of living trees near the ChNPP zone / Ed. IAEA, 157-162 http://www.iaea.org/inis/collection/NCLCollectionStore/_Public/28/017/28017501.pdf (in Russian) 16. Scheglov A., Tsvetnova O., Klyashtorin A., 2014. Biogeochemical cycles of Chornobyl-born radionuclides in the contaminated forest ecosystems. Long-term dynamics of the migration processes / Journal of Geochemical Exploration 144, p. 260–266 17. Grodzinskaya G., Searchin S., Kuchma M., Konishchuk V., 2008. Macromicets are bioindicators of radiocaesium contamination of forest ecosystems of Ukraine / Bulletin of the National Academy of Sciences of Ukraine 9, p. 26-37 (in Ukrainian)

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222. Kashparov V.O., Bondar, Yu. O., Yoshchenko , V. I. 2009. Dose dependence of morphological changes and aberration to the plantation of Pine in the Chornobyl NPP Exclusion Zone / Nuclear Physics and Power 10(1), p. 86–91 http://jnpae.kinr.Kyiv.ua/10.1/Articles_PDF/jnpae-2009-10-0086-Kashparov.pdf 223. Kashparov V., Colle C., Zvarych S., Yoshchenko V., Levchuk S., Lundin S. Soil-to-plant halogens transfer studies 1. Root uptake of radioiodine by plants //Journal of Environmental Radioactivity, v.79, Issue 2, 2005, p. 187-204 224. Kashparov V., Colle C., Zvarych S., Yoshchenko V., Levchuk S., Lundin S. Soil-to-plant halogens transfer studies 2. Root uptake of radiochlorine by plants //Journal of Environmental Radioactivity, v.79, Issue 3, 2005, p. 233-253 225. Kashparov V., Colle C., Levchuk S., Yoshchenko V., Svydynuk N. Transfer of chlorine from the environment to agricultural foodstuffs //Journal of Environmental Radioactivity, v.94, Issue 1, 2007, p. 1-15

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226. Kashparov V., Colle C., Levchuk S., Yoshchenko V., Zvarych S. Radiochlorine concentration ratios for agricultural plants in various soil conditions //Journal of Environmental Radioactivity, v. 95, Issue 1, 2007, p.10-22 227. Quantification of radionuclide transfer in terrestrial and freshwater environments for radiological assessments, IAEA-TECDOC-1616, Vienna, 2009, p. 616 228. Handbook of parameter values for the prediction of radionuclide transfer in terrestrial and fresh-water environments. Vienna: IAEA-TRS-472, 2010. 194p. 229. Kashparov V.; Levchuk S.; Zhurba M.; Protsak V.; Khomutinin Yu.; Beresford N.A.; Chaplow J.S. Spatial datasets of radionuclide contamination in the Ukrainian Chornobyl Exclusion Zone // Earth System Science Data (ESSD), v.10, 2018, p. 339-353. https://doi.org/10.5194/essd-10-339-2018 230. Kashparov V.O., Lundin S.M., Zvarych S.I. et al. Territory contamination with the radionuclides representing the fuel component of Chornobyl fallout. The Science of the Total Environment 317 (1-3), 2003, p. 105-119 231. Kashparov V.O., Ivanov Yu.A., Zvarych S.I. et al. Formation of hot particles during the Chornobyl Nuclear Power Plant Accident //Nuclear Technology 114 (1), 1996, p. 246-253 232. IAEA. 2011. Radiation Protection and Safety of Radiation Sources: International Basic Safety Standards: General Safety Requirements. – Interim edition. – Vienna: International Atomic Energy Agency, 303 p. 233. Eckerman K.F. and Ryman J. C. External exposure to radionuclides in air, water, and soil. Federal guidance report No. 12. Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, Office of Radiation and Indoor Air, U.S. Environmental Protection Agency, Washington, DC 20460, 1993, 238p. 234. Radiological condition of the areas classified as radioactive contamination zones, ed. by V.I. Kholosha, Veta, Kyiv, 2008, 54 p. (in Ukrainian) 235. Twenty five years of the Chornobyl Disaster. Safety of the future -K: KIM - 2011. – 356 p. (in Ukrainian) 236. Protsak V.P., Odintsov O.O. Assessment of the Chornobyl radionuclides containment forms in bottom sediments of the ChNPP cooling pond // Nuclear Physics and Power Engineering. - 2014 - V. 15, No. 3 - p. 259-268 (in Ukrainian) 237. Protsak V.P., Odintsov O.O., Khomutinin Yu.V., Zhurba M.A., Prokopchuk N.N., Kashparov V.O. Dynamics of radionuclide physical and chemical forms in bottom sediments of the ChNPP cooling pond after the drainage: 1. Simulation experiment // Nuclear Physics and Power Engineering. - 2017. - V. 18, No. 4 - p. 341-349 (in Ukrainian) 238. Ulanovsky A., Jacob P., Fesenko S., Bogdevitch I., Kashparov V., Sanzharova N. ReSCA: decision support tool for remediation planning after the Chornobyl accident //Radiation and Environmental Biophysics, Springer, v.50, 2011, p.67–83 239. Kashparov V.O., Protsak V.P., Yoshchenko V.I., Watterson J.D. Inhalation of Radionuclides During Agricultural Work in Areas Contaminated as a Result of the Chornobyl Reactor Accident //J. Aerosol Science. –1994. - v.25, No.5.- p.761-767 240. Kashparov V.O., Lundin S.M, Kadygrib A.M., Protsak V.P., Levchuk S.E., Yoshchenko V.I., Kashpur V.A., Talerko N.M. Forest fires in the territory contaminated as a result of the Chornobyl accident: radioactive aerosol re-suspension and exposure of fire-fighters 241. Yoshchenko V.I., Kashparov V.O., Protsak V.P., Lundin S.M., Levchuk S.E., Kadygrib A.M., Zvarych S.I., Khomutinin Yu.V., Maloshtan I.M., Lanshin V.P., Kovtun M.V., Tschiersch J. Re-suspension and redistribution of radionuclides during grassland and forest fires in the Chornobyl exclusion zone: part I. Fire experiments //Journal of Environmental Radioactivity, v.86, Issue 2, 2006, p.143-163

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242. State Hygienic Regulations GN 6.6.1.1-130-2006. Acceptable levels of 137Cs and 90Sr radionuclide concentrations in foods and drinking water (DR-2006) // Official Bulletin of Ukraine. 2006. No. 29. p. 142 (in Ukrainian) 243. Hygienic Regulations on specific activity of 137Cs and 90Sr radionuclides in wood and wood products (GNPAR-2005) - Approved by Order of the Ministry of Health of Ukraine dated 31.10.2005. - No. 573. - 3p. (in Ukrainian) 244. Otreshko L.M., Levchuk S.E., Yoshchenko L.V. Concentrations of 90Sr in grain in the fuel traces of Chornobyl radioactive fallouts // Nuclear Physics and Power Engineering. - 2014 - V. 15, No. 2 - p. 171-177 (in Ukrainian) 245. Otreshko L.N., Zhurba M.A., Bilous A.M., Yoshchenko L.V. Concentrations of 90Sr and 137Cs in fuel wood on the southern fuel trace of Chornobyl radioactive fallouts // Nuclear Physics and Power Engineering. – 2015. – V. 16, No. 2. (in Russian) 246. Experimental findings of SSE “Ecocenter”, Executive Summary, 2016 (in Russian) 247 Kirieiev S., Godun B., Vishnevskyi et al. Radiation situation within the exclusion zone in 2010 / Bulletin of ecological conditions in the exclusion zone and in the zone of absolute (mandatory) resettlement, No.1(37) 2011, p.37-62 (in Ukrainian) 248. Kashparov V.O., Zhurba M.A., Kirieiev SI, Zibtsev S.V., Myroniuk V.V. Estimation of expected exposure doses of fire fighters in the Chornobyl exclusion zone in April 2015 // Nuclear Physics and Power Engineering. 2015. - V. 16, No. 4. - p. 399 – 407 (in Russian) 249. Khomutinin Yu.V., Yoshchenko V.I., Kashparov V.O., Levchuk S.E., Hlukhovskyi O.S., Protsak V.P., Lundin S.M. Assessment of radiological hazard of hypothetical forest fires in the exclusion zone // Bulletin of ecological conditions in the exclusion zone and in the zone of absolute (mandatory) resettlement, No.1(29) 2007, p. 28-33 (in Ukrainian) 250. Yoshchenko V.I., Kashparov V.O., Levchuk S.E., Khomutinin Yu.V., Protsak V.P., Lundin S.M. Radiological hazard of fires in terrestrial ecosystems of the exclusion zone // Bulletin of ecological conditions in the exclusion zone and in the zone of absolute (mandatory) resettlement, Chornobylinterinform, Kyiv, 2006, No.2(28), p.27-35 (in Ukrainian) 251. Environmental consequences of the Chornobyl accident and their remediation: twenty years of experience // Report of the Chornobyl Forum Expert Group ‘The Environment’, Ed. by Anspaugh L. and Balonov M., Radiological assessment reports series, IAEA, STI/PUB/1239, 2006, 166 p. 252. Buhai D., Skalskyi A., Haneke K., Thierfeldt S., Nitzsche O., Tretiak A., Kubko Yu. Groundwater monitoring and modelling of the “VECTOR” site for near-surface radioactive waste disposal in the Chornobyl exclusion zone // Nuclear Physics and Atomic Energy, 2017, Vol. 18, No. 4, p.382-389.

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APPENDIX A Characteristics of current network of scientific radioecological monitoring sites in the ChEZ

No Site ID Ecosystem N E Monitored parameters Organizations 1 ChZ-1 (3) Terrestrial 51.43433 30.10822 Biogeochemical cycle: 2 ChZ-2 (4) 51.42576 30.11153 depots and fluxes of 137Cs and 90Sr in forest ecosystems 3 ChZ-3 (5) 51.45211 30.23415 Redistribution of 4 ChZ-4 (6) 51.44754 30.21002 biologically mobile 5 ChZ-5 (7) 51.42022 30.16364 radionuclides in the 6 ChZ-6 (8) 51.44496 30.19738 components of forest 7 ChZ-7 (9) 51.44450 30.19842 ecosystems of typical pine 8 ChZ -8 (10) 51.35418 29.98985 stands 9 ChZ -9 (11) 51.43808 30.16017 UIAR of 10 ChZ -10 (12) 51.43881 30.15939 NUBiP of 11 ChZ -11 (13) 51.44349 30.14770 Ukraine 12 ChZ -12 (14) 51.39896 30.20349 13 ChZ -13 15) 51.39948 30.20328 14 ChZ -14 (16) 51.40747 30.19832 15 ChZ -15 (17) 51.40711 30.19995 16 ChZ -0/1 RF 51.38345 30.07117 Dynamics of radioactive 17 ChZ -0/2 NB 51.40604 30.08969 contamination of the components of forest biogeocenose on the RWTLS sites

18 E7-16-S Terrestrial 51.382381 30.033179 Dynamics of radioactive 19 E7-16-1t 51.383957 30.072232 contamination of pine and UIAR of 20 E7-16-1o 51.383846 30.072289 birch, radiation doses, NUBiP of 21 E7-16-C 51.372305 30.029117 morphological and Ukraine 22 E7-16-K 51.346963 30.126321 cytogenetic effects 23 E7-16-Iv 50.898991 29.952973 24 Hlyboke Aquatic 51.445020 30.066990 Contamination dynamics 25 Starosillia 51.353773 30.196582 for water, hydrobionts, UIAR, IHB aquatic vegetation; and URIH exposure doses, under the NAS morphological and of Ukraine cytogenetic effects 26 Chystohalivka Terrestrial 51.372305 30.029117 Dynamics of aerial and UIAR root intake of 36Cl, 75Se, 99Tc, 129I, 238-240Pu, 241Am by various agricultural crops from the four soils having contrasting characteristics and taken from different parts of Ukraine 27 P-1 Terrestrial 51.376079 30.04056 Vertical migration of 28 P-2 51.37611 30.03333 radionuclides in soil UIAR of 29 P-3 51.375810 30.021607 layers in open landscape NUBiP of 30 P-4 51.343181 30.103519 types Ukraine 31 P-5 51.446101 30.138289 193

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32 P-6 51.446200 30.138290 33 P-7 51.412778 30.199167 34 P-8 51.356936 29.905042 35 P-11 51.331392 29.784067 36 P-13 51.41889 30.07306 37 Bi-1/NF Terrestrial 51.38433 30.07160 Effects of fire at the 38 Bi-1/F 51.38439 30.07161 RWTLS "Red Forest" for 39 Pi-1/NF 51.38398 30.07228 the radionuclide mobility 40 Pi-1/F 51.38416 30.07182 in organic and mineral soil 41 Bi-2/NF 51.38188 30.03208 layers for pine and birch 42 Bi-2/F 51.38087 30.03392 stands 43 Pi-2/NF 51.38587 30.04372 44 Pi-2/F 51.38574 30.04379 45 Kopachi 2 51.34531 30.12861 Biochemical and 46 Kopachi 1 51.34707 30.12488 morphometric 47 Between 51.37934 30.02503 effects in plants Yaniv and Arabidopsis thaliana (L.) Chystohalivka Heynh. 48 ПП 1 51.316403 30.131667 Radioactive contamination 49 ПП 2 51.372778 30.020556 dynamics in pine 50 ПП 3 51.338333 30.142222 components 51 ПП 6 51.446944 30.136667 UIAR of 52 ПП 7 51.481108 30.129743 NUBiP of 53 ПП 8 51.438056 30.110278 Ukraine 54 ПП 9 51.404167 30.039167 55 ПП 11 51.351389 29.983611 56 ПП 12 51.378611 30.033056 57 ПП 13 51.374722 30.012222 58 ПП 14 51.319722 30.288333 59 ПП 15 51.322222 30.283611 60 L1 51.39888 30.12915 Dynamics of 61 L2 51.39879 30.12960 physicochemical forms of 62 L3 51.39930 30.13108 radionuclides in drained 63 L4 51.39589 30.11091 bottom deposits of the 64 L5 51.39625 30.11029 ChCP 65 T6 51.39474 30.11054 66 “Re- 51.409597 30.132249 Dynamics of suspension” physicochemical forms of radionuclides in bottom deposits of drained lakes

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APPENDIX B Results of the survey of scientific organizations that are involved into the ChEZ monitoring

Questionnaire 1 For the systematization of monitoring and scientific studies within the ChEZ (to be completed separately for each study)

Organization: Water Radioecology Department, Institute of Hydrobiology of the NAS of Ukraine Object of your researches (soil, water, Aquatic organisms (aquatic plants, mollusks, fish), air, organisms, etc.) bottom deposits, water Your observation network (research site Water bodies of left-bank flood plain ща the Pripyat (sites), coordinates) River: Lakes of Hlyboke, Daleke, Verhshyna, Krasnenska Starytsia. ChNPP cooling pond, Azbuchyn Lake, Yaniv Backwater, Pripyat River (near Chornobyl town), Uzh River (near the village of Cherevach) Time span (research start dare, frequency Seasonal researches (spring, summer, autumn) since of observations) 1988 Monitored parameters (activity of Hydrophysical, hydrochemical, hydrobiological radionuclides, concentration of heavy parameters of aquatic habitats; specific activity of metals, etc.) radionuclides; exposure and absorbed dose rates in aquatic organisms Subject of your research, i.e. processes Accumulation, migration, redistribution of 90Sr, 137Cs (for example, migration of radionuclides and their physical and chemical forms in aquatic (3H, 14C, 36Cl, 90Sr, 99Tc, 129I, 137Cs, 238- ecosystem components. Assessment of dose- 241Pu, 241Am) and heavy metals dependent cytogenetic, hematological, histological, (accumulation); frequency of yielding, parasitological, and population effects of radiobiological effects, morbidity, chronic ionizing exposure impacts on aquatic biota mortality, population dynamics, etc.) List of applied analytical methods Hydrobiological and radioecological methods of (sampling and measurement methods) sampling. Gamma-spectrometric and radiochemical methods for the estimation of radionuclide specific activity. Cytogenetic, hematological, and histological methods for the assessment of radiation effects Collection, storage and exchange of http://hydrobio.kiev.ua information (links to publications, reports, etc. on your research issues) Do you carry out monitoring to assess No the effects of ionizing radiation for the carbon stocks in ecosystems (increase in biomass, rate of organic matter decomposition, etc.)? Do you carry out monitoring to assess Yes the effects of ionizing radiation for the biodiversity of ecosystems, populations and organisms?

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Questionnaire 2 For the systematization of monitoring and scientific studies within the ChEZ (to be completed separately for each study)

Organization: Institute of Cell Biology and Genetic Engineering of the NASU, Biophysics and Radiobiology Department, Laboratory of Plant Signal Systems Object of your researches (soil, water, air, Soil and plants organisms, etc.) Your observation network (research site (sites), Chornobyl town coordinates) Time span (research start dare, frequency of since 2007 till 2015 observations) Monitored parameters (activity of radionuclides, Chronic exposure concentration of heavy metals, etc.) Subject of your research, i.e. processes (for example, Accumulation of 90Sr and 137Cs in soil migration of radionuclides (3H, 14C, 36Cl, 90Sr, 99Tc, and plants 129I, 137Cs, 238-241Pu, 241Am) and heavy metals (accumulation); frequency of radiobiological effects, morbidity, mortality, population dynamics, etc.) List of applied analytical methods (sampling and Protecomics measurement methods) Collection, storage and exchange of information www.chernobylproteomics.sav.sk (links to publications, reports, etc. on your research issues) Do you carry out monitoring to assess the effects of No ionizing radiation for the carbon stocks in ecosystems (increase in biomass, rate of organic matter decomposition, etc.)? Do you carry out monitoring to assess the effects of No ionizing radiation for the biodiversity of ecosystems, populations and organisms?

Questionnaire 3 For the systematization of monitoring and scientific studies within the ChEZ (to be completed separately for each study)

Organization: Institute of Zoology named after I.I. Shmalhausen of the NAS of Ukraine Object of your researches (soil, water, air, Animals organisms, etc.) Your observation network (research site (sites), Kopachi, Chystohalivka, Nova coordinates) Krasnytsia, Illintsi, south from the city of Pripyat, Novoshepelychi forestry; hunting animals – throughout ChEZ, not fixed

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Time span (research start dare, frequency of Model species and species groups: observations) 07.1986 spring – autumn 8 months monthly; Hunting animals: November – February monthly before 2001 Monitored parameters (activity of radionuclides, Activity of radionuclides, population concentration of heavy metals, etc.) characteristics, changes in species diversity Subject of your research, i.e. processes (for example, Accumulation and migration of 137Cs in migration of radionuclides (3H, 14C, 36Cl, 90Sr, 99Tc, trophic levels, frequency of 129I, 137Cs, 238-241Pu, 241Am) and heavy metals radiobiological effects, fertility, (accumulation); frequency of radiobiological effects, mortality, dynamics of populations and morbidity, mortality, population dynamics, etc.) faunal complexes List of applied analytical methods (sampling and Activity of 137Cs measurement methods) spectrometry, classical ecological methods of populations recording and dynamics, methods of chromosomal analysis Collection, storage and exchange of information E.g. map of animals contamination with (links to publications, reports, etc. on your research 137Cs, Kyiv 2001, and many others issues) Do you carry out monitoring to assess the effects of ionizing radiation for the carbon stocks in ecosystems (increase in biomass, rate of organic matter decomposition, etc.)? Do you carry out monitoring to assess the effects of Is not carried out since 2001 ionizing radiation for the biodiversity of ecosystems, populations and organisms?

Questionnaire 4 For the systematization of monitoring and scientific studies within the ChEZ (to be completed separately for each study)

Organization: Institute for Nuclear Research of the NAS of Ukraine Object of your researches (soil, water, air, Macromycete fungi, soil organisms, etc.) Your observation network (research site (sites), 1989 – 2008 – practically entire ChEZ; coordinates) 2008 – to date – Leliv, Kopachi, paryshiv, Dytiatky Time span (research start dare, frequency of 1989 – 2006 - once a year; observations) since 2006 – to date - from the beginning and till the end of fruiting period Monitored parameters (activity of radionuclides, Specific activity of 137Cs concentration of heavy metals, etc.)

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Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

Subject of your research, i.e. processes (for 1989 – 2006 – characteristics of 137Cs example, migration of radionuclides (3H, 14C, 36Cl, accumulation by macromycete fungi; 90Sr, 99Tc, 129I, 137Cs, 238-241Pu, 241Am) and heavy 2006 – to date - seasonal changes in 137Cs metals (accumulation); frequency of transfer to the soil-macromycetes chain radiobiological effects, morbidity, mortality, population dynamics, etc.) List of applied analytical methods (sampling and Standard methods of sampling and gamma measurement methods) spectrometry Collection, storage and exchange of information Zarubina N. The influence of biotic and (links to publications, reports, etc. on your research abiotic factors on 137Cs accumulation in issues) higher fungi after the accident at Chornobyl NPP // J. Envir. Radioact. 161 (2016). – P. 66 – 72. Do you carry out monitoring to assess the effects of No ionizing radiation for the carbon stocks in ecosystems (increase in biomass, rate of organic matter decomposition, etc.)? Do you carry out monitoring to assess the effects of No ionizing radiation for the biodiversity of ecosystems, populations and organisms?

Questionnaire 5 For the systematization of monitoring and scientific studies within the ChEZ (to be completed separately for each study)

Organization: Institute for Nuclear Research of the NAS of Ukraine Object of your researches (soil, water, air, Forest ecosystems: soil, vegetation, organisms, etc.) macromycete fungi Your observation network (research site (sites), Leliv (30˚09'36.63''E, 51˚19'19.74''N), coordinates) Parychiv (51˚17'57.54''E, 30˚18'17.43''N), Dytiatky (30˚07'21.83''E, 51˚07'13.37''N) Time span (research start dare, frequency of 2006 – 2012 – once a month year-round, observations) 2013 – 2015 – once a fortnight year- round, 2016 – to date - once a month in spring-autumn period Monitored parameters (activity of radionuclides, Specific activity of 137Cs in samples concentration of heavy metals, etc.) Subject of your research, i.e. processes (for example, Redistribution of 137Cs between soil and migration of radionuclides (3H, 14C, 36Cl, 90Sr, 99Tc, vegetation, between soil and fungi during 129I, 137Cs, 238-241Pu, 241Am) and heavy metals a calendar year (accumulation); frequency of radiobiological effects, morbidity, mortality, population dynamics, etc.) List of applied analytical methods (sampling and Standard methods of sampling, sample measurement methods) preparation and measurement of 137Cs specific activity in samples

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Collection, storage and exchange of information Zarubina N. 137Cs Specific Activity (links to publications, reports, etc. on your research Seasonal Changes within Various Forest issues) Ecosystem Objects after the ChNPP Accident // 15th International Congress of Radiation Research (ICRR2015), May 25 – 29, 2015, Japan, Kyoto. ICRR2015: PDFs: 10821 Do you carry out monitoring to assess the effects of No ionizing radiation for the carbon stocks in ecosystems (increase in biomass, rate of organic matter decomposition, etc.)? Do you carry out monitoring to assess the effects of No ionizing radiation for the biodiversity of ecosystems, populations and organisms?

Questionnaire 6 For the systematization of monitoring and scientific studies within the ChEZ (to be completed separately for each study)

Organization: Institute for Nuclear Research of the NAS of Ukraine Object of your researches (soil, water, air, Fish, water, bottom deposits, vegetation, organisms, etc.) mollusks Your observation network (research site (sites), ChNPP cooling pond, Pripyat River coordinates) Time span (research start dare, frequency of 1986 - 2016 observations) Monitored parameters (activity of radionuclides, Specific activity of radionuclides concentration of heavy metals, etc.) Subject of your research, i.e. processes (for Accumulation of radionuclides in various example, migration of radionuclides (3H, 14C, 36Cl, objects of aquatic ecosystems after the 90Sr, 99Tc, 129I, 137Cs, 238-241Pu, 241Am) and heavy accident; changes in 137Cs accumulation metals (accumulation); frequency of by various objects of the ChCP ecosystem radiobiological effects, morbidity, mortality, after the start of its transformation population dynamics, etc.) List of applied analytical methods (sampling and Standard methods of sampling and measurement methods) measurements Collection, storage and exchange of information 255 publications (monographs, articles, (links to publications, reports, etc. on your research reports) issues) Do you carry out monitoring to assess the effects of No ionizing radiation for the carbon stocks in ecosystems (increase in biomass, rate of organic matter decomposition, etc.)? Do you carry out monitoring to assess the effects of No ionizing radiation for the biodiversity of ecosystems, populations and organisms?

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Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

Questionnaire 7 For the systematization of monitoring and scientific studies within the ChEZ (to be completed separately for each study)

Organization: Institute for NPP Nuclear Safety Problems of the NAS of Ukraine Object of your researches (soil, water, air, Soil, water, air organisms, etc.) Your observation network (research site (sites), Shelter Object and SSE ChNPP coordinates) industrial site Time span (research start dare, frequency of 1992 -2018 observations) Monitored parameters (activity of radionuclides, Activity of radionuclides concentration of heavy metals, etc.) Subject of your research, i.e. processes (for example, 3H, 90Sr, 129I, 137Cs, 238-241Pu, 241Am migration of radionuclides (3H, 14C, 36Cl, 90Sr, 99Tc, 129I, 137Cs, 238-241Pu, 241Am) and heavy metals (accumulation); frequency of radiobiological effects, morbidity, mortality, population dynamics, etc.) List of applied analytical methods (sampling and Sampling and α, , β measurements measurement methods) Collection, storage and exchange of information (links to publications, reports, etc. on your research issues) Do you carry out monitoring to assess the effects of No ionizing radiation for the carbon stocks in ecosystems (increase in biomass, rate of organic matter decomposition, etc.)? Do you carry out monitoring to assess the effects of No ionizing radiation for the biodiversity of ecosystems, populations and organisms?

Questionnaire 8 For the systematization of monitoring and scientific studies within the ChEZ (to be completed separately for each study)

Organization: Institute for NPP Safety Problems of the NASU Object of your researches (soil, water, air, Project title: “Radio-hydro-ecological organisms, etc.) monitoring near the Shelter Object”. The research objects include: soils and radioactive waste localized in the soils, ground and surface waters, as well as water clusters inside the Shelter Object Your observation network (research site (sites), Observation wells at ChNPP industrial site coordinates) and in the adjacent area Time span (research start dare, frequency of The research was started in 1995. observations) The sampling frequency is once per a month and once per a quarter. The frequency of groundwater level monitoring is twice a month 200

Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

Monitored parameters (activity of radionuclides, Activity of radionuclides, full chemical concentration of heavy metals, etc.) composition, observation of level conditions of the groundwater Subject of your research, i.e. processes (for Migration of radionuclides: 3H, 90Sr, 137Cs, example, migration of radionuclides (3H, 14C, 36Cl, 238-241Pu, 241Am, U. Impact of chemical 90Sr, 99Tc, 129I, 137Cs, 238-241Pu, 241Am) and heavy composition and pH value of the metals (accumulation); frequency of groundwater on the formation of radiobiological effects, morbidity, mortality, radionuclide high migration ability population dynamics, etc.) List of applied analytical methods (sampling and Sampling of water from the wells after measurement methods) pumping; gamma- and alpha- spectrometry, radiometric methods. Chemical composition of water samples is assessed by standard methods Collection, storage and exchange of information Database. Annual reports. (links to publications, reports, etc. on your research Over 80 publications. issues) Do you carry out monitoring to assess the effects of No ionizing radiation for the carbon stocks in ecosystems (increase in biomass, rate of organic matter decomposition, etc.)? Do you carry out monitoring to assess the effects of The monitoring results are used to develop ionizing radiation for the biodiversity of safety analysis reports and environmental ecosystems, populations and organisms? impact assessments for the designed or commissioned facilities (the complex of NSC-SO).

Questionnaire 9 For the systematization of monitoring and scientific studies within the ChEZ (to be completed separately for each study)

Organization: Laboratory of Biosystems Radioecological Reliability, Institute of Cell Biology and Genetic Engineering Object of your researches (soil, water, air, Soil, water, population, agri-ecosystems, organisms, etc.) biota of various ecosystems, dose loads in biota and humans Your observation network (research site (sites), ChEZ effects in the Dnipro cascade, in the coordinates) biota of ChEZ lakes. The research site is located near the village of Buriakivka Time span (research start dare, frequency of The researches were started in 1986 and observations) are carried out annually, as a rule Monitored parameters (activity of radionuclides, Activity of radionuclides, concentration of concentration of heavy metals, etc.) heavy metals. Parameters of ecosystems radioactive capacity

201

Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

Subject of your research, i.e. processes (for Migration of radionuclides (90Sr, 137Cs, example, migration of radionuclides (3H, 14C, 36Cl, (accumulation); frequency of 90Sr, 99Tc, 129I, 137Cs, 238-241Pu, 241Am) and heavy radiobiological effects, mortality, dose metals (accumulation); frequency of loads and risks for biota and population radiobiological effects, morbidity, mortality, population dynamics, etc.) List of applied analytical methods (sampling and Gamma spectrometer, heavy metals measurement methods) detection spectrometers Collection, storage and exchange of information 2 basic monographs were published in (links to publications, reports, etc. on your research recent years. issues) Yu.A.Kutlakhmendov "The Road to Theoretical Radioecology" (2017) Yu.A.Kutlakhmendov et al. "Reliability of Biological Systems" (2018) Do you carry out monitoring to assess the effects of No ionizing radiation for the carbon stocks in ecosystems (increase in biomass, rate of organic matter decomposition, etc.)? Do you carry out monitoring to assess the effects of Models and means of estimating radio ionizing radiation for the biodiversity of capacity and dose loads in biota and ecosystems, populations and organisms? population were developed. Methods and countermeasures to protect biota and population

Questionnaire 10 For the systematization of monitoring and scientific studies within the ChEZ (to be completed separately for each study)

Organization: Institute for Nuclear Research of the NAS of Ukraine Object of your researches (soil, water, air, Mouse-like rodents organisms, etc.) Your observation network (research site (sites), 7 research sites coordinates) Time span (research start dare, frequency of Annually once a year since 2008 observations) Monitored parameters (activity of radionuclides, Population abundance, species concentration of heavy metals, etc.) composition, activity of radionuclides in animal carcasses and skeletons

Subject of your research, i.e. processes (for Investigation of radiobiological effects example, migration of radionuclides (3H, 14C, 36Cl, (cytogenetic, cytotoxic, hematological) 90Sr, 99Tc, 129I, 137Cs, 238-241Pu, 241Am) and heavy effects metals (accumulation); frequency of radiobiological effects, morbidity, mortality, population dynamics, etc.) List of applied analytical methods (sampling and γ-β-spectrometry measurement methods)

202

Conserving, Enhancing and Managing Carbon Stocks and Biodiversity in the Chornobyl Exclusion Zone

Collection, storage and exchange of information Publications (links to publications, reports, etc. on your research issues) Do you carry out monitoring to assess the effects of No ionizing radiation for the carbon stocks in ecosystems (increase in biomass, rate of organic matter decomposition, etc.)? Do you carry out monitoring to assess the effects of Included ionizing radiation for the biodiversity of ecosystems, populations and organisms?

Questionnaire 11 For the systematization of monitoring and scientific studies within the ChEZ (to be completed separately for each study)

Organization: Institute for Nuclear Research of the NAS of Ukraine Object of your researches (soil, water, air, Samples of the environment organisms, etc.) Your observation network (research site (sites), 5 research sites coordinates) Time span (research start dare, frequency of Periodically since 2010 observations) Monitored parameters (activity of radionuclides, Activity of man-made radionuclides in concentration of heavy metals, etc.) soils of the ChEZ ‘near zone’ Subject of your research, i.e. processes (for Investigation of radionuclide vertical example, migration of radionuclides (3H, 14C, 36Cl, migration: 90Sr, 137Cs, 241Am 90Sr, 99Tc, 129I, 137Cs, 238-241Pu, 241Am) and heavy metals (accumulation); frequency of radiobiological effects, morbidity, mortality, population dynamics, etc.) List of applied analytical methods (sampling and Standard methods for sampling the measurement methods) environment, γ-β-spectrometry Collection, storage and exchange of information Scientific articles in magazines, reports for (links to publications, reports, etc. on your research 2010-2014 (UkrNTI) issues) Do you carry out monitoring to assess the effects of No ionizing radiation for the carbon stocks in ecosystems (increase in biomass, rate of organic matter decomposition, etc.)? Do you carry out monitoring to assess the effects of No ionizing radiation for the biodiversity of ecosystems, populations and organisms?

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