The Application of 137Cs and 210Pbex Methods in Soil Erosion
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Open Geosci. 2020; 12:11–24 Research Article Kristina S. Kalkan*, Sofija Forkapić, Slobodan B. Marković, Kristina Bikit, Milivoj B. Gavrilov, Radislav Tošić, Dušan Mrđa, and Robert Lakatoš 137 210 The application of Cs and Pbex methods in soil erosion research of Titel loess plateau, Vojvodina, Northern Serbia https://doi.org/10.1515/geo-2020-0002 Received Mar 31, 2019; accepted Dec 17, 2019 1 Introduction Abstract: Soil erosion is one of the largest global prob- Land degradation is a broad term that relates essentially to lems of environmental protection and sustainable devel- the gradual loss of soil functions by the interaction of nat- opment, causing serious land degradation and environ- ural and anthropogenic factors [1]. Its consequences are mental deterioration. The need for fast and accurate soil reflected in the loss of fertility, desertification, vulnerabil- rate assessment of erosion and deposition favors the ap- ity to floods, vulnerability to climate change and acceler- plication of alternative methods based on the radionu- ated human activities. The complexity of the soil degra- clide measurement technique contrary to long-term con- dation phenomenon could be explained by categorizing ventional methods. In this paper, we used gamma spec- the term in four basic groups: erosion (soil deposition), 137 210 trometry measurements of Cs and unsupported Pbex depletion (taking of fertile material), accretion (chemical in order to quantify the erosion on the Titel Loess Plateau changes in the form of accumulation of heavy metals) and near the Tisa (Tisza) River in the Vojvodina province of Ser- compaction (physical disturbance) [1]. Every year about bia. Along the slope of the study area and in the immediate 10,000,000 ha of arable land on the global level is lost vicinity eight representative soil depth profiles were taken only by erosion, with several tens of times faster loss com- and the radioactivity content in 1 cm thick soil layers was pared to the time it takes to renew [2]. The consequences analyzed. Soil erosion rates were estimated according to of soil erosion are reflected in reduced agricultural produc- the profile distribution model and the diffusion and migra- tivity (on-site) and increased flooding of lake-river-sea sys- tion model for undisturbed soil. The net soil erosion rates, tems due to intense sedimentation [3]. Furthermore, cur- estimated by 137Cs method range from −2.3 t ha−1 yr−1 to −2.7 t ha−1 yr−1, related to the used conversion model which is comparable to published results of similar stud- Slobodan B. Marković: University of Novi Sad, Faculty of Sciences, ies of soil erosion in the region. Vertical distribution of Department of Geography, Tourism and Hotel Management, Trg natural radionuclides in soil profiles was also discussed Dositeja Obradovića 3, 21000 Novi Sad, Serbia; and compared with the profile distribution of unsupported Email: [email protected] 210 Pbex measurements. The use of diffusion and migration Kristina Bikit: University of Novi Sad, Faculty of Sciences, Chair of 210 Nuclear Physics, Trg Dositeja Obradovića 4, 21000 Novi Sad, Serbia; model to convert the results of Pbex activities to soil re- Email: [email protected] distribution rates indicates a slightly higher net erosion of Milivoj B. Gavrilov: University of Novi Sad, Faculty of Sciences, −1 −1 −3.7 t ha yr with 98% of the sediment delivery ratio. Department of Geography, Tourism and Hotel Management, Trg Dositeja Obradovića 3, 21000 Novi Sad, Serbia; Keywords: radiocaesium, unsupported lead, gamma- Email: [email protected] spectrometry, soil erosion, gully erosion, Titel loess Radislav Tošić: University of Banja Luka, Faculty of Sciences, Chair plateau of Physical Geography and Geology, Mladena Stojanovića 2, 78000 Banja Luka, Bosnia and Herzegovina; Email: [email protected] Dušan Mrđa: University of Novi Sad, Faculty of Sciences, Chair of *Corresponding Author: Kristina S. Kalkan: Faculty of Sciences Nuclear Physics, Trg Dositeja Obradovića 4, 21000 Novi Sad, Serbia; Novi Sad, Vojvodina, Serbia; Email: [email protected] Email: [email protected] Sofija Forkapić: University of Novi Sad, Faculty of Sciences, Chair Robert Lakatoš: University of Novi Sad, Faculty of Technical Sci- of Nuclear Physics, Trg Dositeja Obradovića 4, 21000 Novi Sad, ences, Chair of Physics, Trg Dositeja Obradovića 6, 21000 Novi Sad, Serbia; Email: [email protected] Serbia; Email: [email protected] Open Access. © 2020 K. S. Kalkan et al., published by De Gruyter. This work is licensed under the Creative Commons Attribution 4.0 License 12 Ë K. S. Kalkan et al. rent land loss rates are unsustainable and can grow signifi- in the atmosphere between May 1st and 5th formed the third cantly in recent times due to significant changes in soil cov- radioactive cloud, which moved south of Chernobyl, cross- erage and rainfall intensity as a matter of human impact ing former Yugoslavia, Greece, and western Turkey, and and climate change. Therefore, the need to monitor the ex- then be turned by the wind to the north towards Scandi- tent of land loss is highly justified. Conventional monitor- navia. Despite the fact that majority of studies worldwide ing techniques have numerous limitations in terms of rep- emphasize nuclear testing as the most important source of resentativeness of data, temporal and spatial resolution, Cs in the environment, the obtained average value of sur- costs, long-term measurements with high uncertainties [4]. face contamination by 137Cs in 1986 for territory of former During the last fifty years, empirical and semi-empirical Yugoslavia of 14.0 kBq m−2 (from 0.8 kBq m−2 in the zone of models of various complexities (e.g. USLE, EPIC, WEPP, minimal contamination to 83 kBq m−2 in the zone of maxi- RUSLE and EUROSEM) were designed to take into account mal contamination) shows that the Chernobyl fallout had the spatial and temporal pattern of variables, such as wa- relatively large contribution to total 137Cs deposition in our tershed topography, soil properties, land use and manage- region [15]. ment, climate, as well as the relationship between them [5]. In alluvial environments, the penetration of radiocae- The resolution and reliability of input variables directly af- sium in the vertical profile is more profound, mostly re- fect the precision of the applied model [6, 7]. Therefore, the lated to high water content, loose soil and the distribu- utilization of fallout radionuclide tracers in soil, mostly tion of soil granulation [16]. In attempting to address these bound to clay minerals and organic matter, such as the limitations of the 137Cs method, the using of unsupported 137 210 fission product Cs and the naturally occurring excess lead Pbex, as an alternative and complementary tracer 210 210 lead Pbex are being increasingly used for soil erosion in soil erosion investigations, was introduced [7, 8]. Pb and sediment assessment [7]. These radionuclides have is a natural product of the 238U decay series derived from been spread in the atmosphere and adsorbed on the sur- the decay of gaseous radon 222Rn, the daughter of 226Ra. face layer of soil, and subsequent redistribution of them Diffusion of the 222Rn from the soil introduces 210Pb into indicates soil erosion and provides the possibility for pre- the atmosphere, and its subsequent fallout provides a con- cise determination of annual soil erosion/deposition. stant input of this radionuclide to surface soils and sed- Due to the long half-life of 30.17 yr and also to fast iments which is not in equilibrium with its non-gaseous and strong sorption of this radionuclide onto soil parti- parent 226Ra. This is the reason why the fallout component cles, the 137Cs is an optimal erosion tracer and also its is termed as "unsupported" or "excess". The 210Pb half- measurement in environmental samples using gamma- life of 22.26 years is also similar to that of 137Cs. However, spectroscopy (an intensive gamma line at 661.7 keV) is because 210Pb was not present in the Chernobyl fallout, relatively easy and accurate without the need of special it doesn’t face the problems associated with interpreting chemical separation. Radiocaesium 137Cs, like a fission 137Cs measurements in those areas that received inputs of product, has become a part of global atmospheric de- both nuclear weapon tests and Chernobyl-derived radio- position since the nuclear weapon tests, with the maxi- caesium. mum caesium deposition in 1963 [3, 8]. During these tests, The main aim of this study was to apply 137Cs and 137 210 Cs has reached the stratosphere and the subsequent Pbex nuclear methods to quantify erosion and depo- fallout affected the whole Northern Hemisphere and part sition rates for the soil in a specific part of the complex of the Southern one [9]. Unlike nuclear tests, caesium re- gully system in the area of Loess Pyramid (LP) [19] on the leased by nuclear accidents has a local character and the southeastern part of Titel Loess Plateau (TLP). This loess deposition is highly conditioned by meteorological con- plateau is a palaeoclimatic and paleoecological witness of ditions [10]. The most notable was the Chernobyl acci- the last 5 glacial-interglacial cycles occurred during the dent [11]. The contamination related to the accident was last 650,000 yr [17]. As a matter of this and other natural spatially inhomogeneous and depended on the trajecto- and social characteristics, TLP was proclaimed as a Spe- ries of main radioactivity clouds, and on the precipitation cial Nature Reserve. The main aim of this study is to ex- in the area of interest at that time [12]. According to the plore soil rate erosion at the uncultivated rim of the TLP as atlas of the spatial distribution of residual levels of cae- a unique geomorphologic unit to control and manage the sium deposition from the atmospheric testing of nuclear soil loss by pluvial erosion.