INIS-XA--259 XA0054563

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A Quarterly Newsletter of the Section

CONTENTS

Isotope techniques in lake water studies 3

Lake Titicaca : history and current studies 6

The evaporation pan technique revisited 9

Groundwater renewal in water scarce areas 11

Isotope response to dynamic changes in groundwater systems due to long- term exploitation 11

Isotope Hydrology Calendar 11

Geothermal energy resources - Results and achievements of regional project RAS/8/075 13 for improved drinking s water resources management 13 s Workshop on isotope data inter- I pretation and integration in site- I conceptual models 13 0)

2nd Interlaboratory comparison for deuterium and 18 analysis of water samples 14 =

Challenges and new techniques for j light element stable isotopes 15 s Selingue lake, Mali

Issued h}' the

Vienna, Austria

ISSN 1020-7120 Issue No. 8/9, December 1999 WATER & ENVIRONMENT NEWS

EDITORIAL

ince its inception in 1997, Water and Environ- resources management and in advancing the under- Sment News has been well received by its read- lying science. ers and has improved the dissemination of current news and developments in Isotope Hydrology in This issue of the News focuses on isotope studies our Member States. It also appears to capture a related to lakes. Physical and bio-geochemical pro- desirable readership, as there is an increased inter- cesses occurring at and below the surface of lake est expressed for participation in upcoming co- water influence lake - atmosphere interactions, sur- ordinated research programmes and other activi- face and groundwater hydrology, and climatic ties. archives in lake sediments. Dr. L. Gourcy has pro- vided a review of some of the Agency's activities in We recognize that publication of the 3rd issue of the development and application of isotope tech- 1999 of the News has been delayed. This delay niques to study lake processes. Dr. J. Gibson and resulted from key staff changes in this past year. Dr. T. Edwards from the University of Waterloo de- Although periodic staff rotation is an essential com- scribe an improved technique for measuring pan ponent of the Agency's policies, there are occa- evaporation rates. Dr. M. A. Paredes Riveros from sions when some schedules are interrupted. We the Proyecto Especial del Lago Titicaca (PELT) , intend to minimize these interruptions as much as Puno, Peru, and Dr. R. Gonfiantini from the Istituto di possible. Geocronologia e Geochimica Isotopica del CNR, Pisa, Italy, describe the use of multiple isotope trac- After a nearly 10 years tenure, the last five as ers to study the dynamics of Lake Titicaca. ! would Section Head, Dr. Klaus Froehlich retired from the like to thank all our colleagues for giving so gener- Agency at the end of July. During Klaus' tenure, ously of their time to improve the quality of the News. the Section's contributions to the Agency's techni- cal cooperation programme were better reco- On behalf of myself and the Section, I wish you all a gnized and Isotope Hydrology was recognized by very happy New Year! the Member States as a significant priority pro- gramme of the Agency. We wish Klaus a very Pradeep Aggarwal happy and productive retirement and look forward Head, Isotope Hydrology Section to benefiting from his advice from time to time.

I am privileged to have been selected to replace Klaus as the Section Head. Although it is a tough act to follow, I hope to successfully lead the Section in increasing the role of Isotope Hydrology in water

Contact Us Mr. CheikhB. Gaye, ext. 21733 e-mail: [email protected] Isotope Hydrology Section International Atomic Energy Agency Mrs. Jane Gerardo-Abaya, ext. 21742 P.O. Box 100, WagramerStrasse 5 e-mail: J. Gerardo-A baya@iaea. org A-1400, Vienna AUSTRIA Mrs. Laurence Gourcy, ext. 21734 Tel. +43-1-2600 + ext e-mail: LGoiircy@iaeaorg Fax: +43-1-26007 Mr. Manfred Groening ext. 21740 Mr. Pradeep Aggarwal, Section Head, e-mail: [email protected] ext. 21735 e-mail: [email protected] Mr. Yucel Yiirtsever, ext. 21732 e-mail: Y. Ywisever@iaeaorg Mr. Edmimao Garcia-Agiido, ext. 21739 e-mail: [email protected] Visit Us on the Internet http:/Avww. iaea. org/programmes/ripc/ih/'index. html

Quarterly No. 8 / 9, December 1999 - Page 2 XA0054564 WATER & ENVIRONMENT NEWS

ISOTOPE TECHNIQUES IN LAKE WATER STUDIES

Scientific Scope ods have recently been used in many studies to determine the mixing processes and the apparent Lakes in a variety of environments (tectonic inclu- age of lake water. For the first time in 1999, such ding rift, glacial, coastal, volcanic and fluvial) cover a techniques were tried in Lake Titicaca where water significant portion of the surface area of the conti- balance parameters are difficult to obtain. These nent. Freshwater lakes are among the most easily developments are expected to provide a better un- exploitable freshwater resources. Lakes are also derstanding of the lake processes. recognized as major sedimentological features in which stored material can be used to study recent Technical assistance on isotopic lake studies climate and evolution. To adequately pre- serve these important landscape features, and to use The support of the IAEA to its Member States in lake them as climatic archives, an improved understand- studies, through the Technical Cooperation Pro- ing of processes controlling their hydrologic and bio- gramme, is often related to the protection of the geochemical environments is necessary. The studies water reservoirs and to understanding the water of lake processes can be separated in three cate- dynamics and contamination problems (Table 2). gories, with specific isotope applications (Table 1): Lakes representing local or regional interests have been studied, like lakes Mogan and Eymir in Turkey, IAEA activities related Beseka in , Manzala in Egypt, Titicaca in Bolivia and Peru, Prespa in the Republic of Macedo- to the study of lakes nia, Greece and Albania, and Chapala in Mexico.

Research and Development Project NIC/8/010 on the study of the water balance of Lake Xolotlan was of particular interest for the The first Advisory Group Meeting (AGM) on the appli- possibility of determining underground components cation of nuclear techniques to study lake dynamics (groundwater inflow and outflow rates). The water stable isotopes were used successfully together with was held in 1977 at the IAEA Headquarters in Vi- 137 210 enna. Twenty-four specialists reviewed current re- pollen, Cs and Pb of the bottom sediment. search trends in order to obtain indications and Artificial tracers have been used in various countries guidelines for future activities in the field of isotope (Chile, Turkey) to study seepage flow, to determine limnoiogy. In 1992, a joint UNESCO/IAEA consul- the turnover time in lakes, and to identify the possi- tants' meeting assessed the new state of the art of ble pollution path. isotope techniques in limnological studies and re- commended a new Co-ordinated Research Pro- Another important problem encountered in lake sys- gramme. This Co-ordinated Research Programme tem is the water level variations. The Caspian Sea is on the "Use of Isotope Techniques in Lake Dynamics the world's largest closed basin. The fact that the Investigations" was initiated in 1994. The programme drainage basins of its major tributaries (Volga, was aimed at assessing the potential of environmen- Ural..) are located in humid climatic regions, tal isotope techniques in studying the dynamics of whereas the Sea is in the semi-arid zone, makes the lakes and related problems such as solute dynamics, Caspian Sea sensitive to hydroclimatic changes. sediment focusing, establishing the water balance This climatic sensitivity is evidenced above all, in the components, and vulnerability of surface water bod- continuous fluctuations of the sea level. Its rapid rise ies to pollution. The CRP enabled a number of - (about 2.25 metres since 1978) is causing great tope and geochemical studies to be carried out on concern to all five riparian countries: Azerbaijan, small and large surface water bodies, with the gen- Iran, Kazakhstan, Russia and Turkmenistan. De- eral aim to better understand the dynamics of these spite many years of study, knowledge of the causes systems under growing anthropogenic influence. A of the Sea's water-level rise and fall is still limited, compilation (TECDOC) of the results of this CRP is in although it has been demonstrated that the water press and is expected to be available in the year budget fluctuations are likely climatically induced. A 2000. regional West Asian project (RAW/8/004) provided support for the use of isotopic techniques in tackling Further improvement of the techniques used for lake sea level rise and its negative consequences on the studies is continuing in many laboratories. For water economies of the riparian countries. balance studies, sampling of water vapour to deter- mine the evaporation factor is difficult to carry out in On the other hand, Lake Beseka in Ethiopia pre- remote areas where no power supply is available. sents the particularity of having extended at an Development and testing of new techniques for water astounding rate for three decades. The continuous vapour sampling are on-going at the IAEA and in rise of the lake level creates problem for highways, some other European laboratories. The tritium-helium isotopes and chlorofluorocarbon concentration meth- Programme Review

Quarterly No. 8 / 9, December 1999 - Page 3 WATER & ENVIRONMENT NEWS

COUNTRIES WITH NATIONAL TC PROJECTS IN ISOTOPE LIMNOLOGY (Since 1978)

Table 1: Role and application areas of isotopes Table 2: IAEA-ongoing TC projects in limnology related to lake studies

Lake Budget * evaporation rate estimation -180.2H, 3H, 36CI Country Title started * precipitation - 18O, 2H, 3H Turkey Study of lakes using 1993 * underground and subsurface inflow and outflow, origin of water -180,2H, 3H, 37CI, 87Sr/86Sr isotope techniques Lake Dynamics Nicaragua Evaluation of anthro- * horizontal and vertical mixing rates, transit time and water veloc- 1995 ity pogenic impact on - artificial tracers; 3H Lake Xolotlan - rare gases; 3He/4He. 20Ne, 2Rn 226 222 Peru and Isotopic and hydro- - Ra/ Rn 1997 -180,2H, 3H Bolivia chemical study of the * apparent age/time of segregation of deep water from the atmo Lake Titicaca sphere 3 3 3a Turkey Nuclear techniques for - H/ He, CI 1997 - freons (CCI2F, and CCI3F) lake and marine pollu- * redox processes and recycling carbon and lake ventilation tion studies -13C, MC in DOC and DIC, 3H * sedimentation rate and migration of sediments on the lake floor Ethiopia Use of isotopes in the 1997 (sediment dating) - 210Pb, 137Cs, "C, 32Si, 10Be, U/Th series study of Lake Beseka - 13C and 18O of carbonates and dissolved water Colombia Hydrodynamics of 1999 * migration of chemical species in sediments and the exchange of Lake Tota and their different substances between sediments and overlying water - artificial tracers 3H effect on pollution 137 - anthropogenic radionuclides; ^Sr, Cs, Macedonia Study of the Prespa 1999 natural radionuclides; 77Be , '" 2100Pb Contamination Greece lake using nuclear and Albania related techniques -15N,18O Paleolimnological investigation - reconstructing hydrological conditions; 3O, "C -iceformation; 180,2H

Programme Review

Quarterly No. 8 / 9, December 1999 - Page 4 WATER & ENVIRONMENT NEWS railways and farm lands. Due to high salinity and fluoride concentration, waters of this lake are not considered potable. Stable water isotopes, tritium and carbon-14 of dissolved inorganic carbon were used to provide conclusive evidence that the lake level rise occurred due to a decrease in the lake outflow. This outflow decrease resulted from an increase in the groundwater elevation to the south and east of the lake, most probably due to in- creased irrigation return over the last three decades.

Laurence Gourcy

The highly contaminated Puno Bay (photo credit: L. Gourcy/ IAEA)

Serma dam, Yogyakarta, Indonesia View of the artificial lake. (Photo credit: E. Garcia-Agudo/IAEA)

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lerma dam, Yogyakarta, Indonesia )ischarge gauging with artificial racers. (Photo credit: E. Garcia-

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Quarterly No. 8 / 9, December 1999 - Page 5 XA0054565 V WATER & ENVIRONMENT NEWS

LAKE TITICACA: HISTORY AND CURRENT STUDIES

rom the early Quaternary, the provides about 55 % of the water Water is removed by Rio De- FAltiplano, the flat region at inflow. On the Altiplano, precipita- saguadero (literally: river which about 4000 m a.s.l. in Peru and tion mainly occurs from December removes water) from the Lago Bolivia between the eastern and to March, in correspondence with Menor, which accounts for the western Andean Cordilleras, was the astronomic summer and the missing 5 % of water losses. Rio occupied by lakes, in shape and southern shift of the ITCZ Desaguadero works as an over- extent different from the present (Intertropical convergence zone). flow for the lake and helps to ones. The history of these lakes is The yearly precipitation amounts to reduce the lake level changes. It documented by lacustrine sedi- about 700 mm around the Lake flows towards the South across ments. Titicaca, and decreases to about the Bolivian Altiplano and after 400 mm in the South at the latitude 400 km reaches the Lake Poopo After the end of the last glaciation, of the town of Oruro, and to 200 (3686 m a.s.l.), south of Oruro; during the Holocene, the Lake Titi- mm in the salares (salt plains) re- the excess water ends up in the caca attained its present shape, at gion. Rains are more abundant on south-western salar de Coipasa a mean altitude of 3810 m a.s.l., a 2 the lake where they range from 800 (3657 m a.s.l.). With its limited total surface of 8400 km , and a 3 3 to 1400 mm/a: this is possibly an discharge (mean value 30 m /s volume of 930 km . It consists of indication that part of the water after collecting water from small three main water bodies, the 2 removed by evaporation returns to tributaries all the way from Lake largest (approx. 6500 km ) and the iake as rain. Titicaca to Lake Poopo), the Rio deepest (288 m) of which is by far Desaguadero is the most impor- the Lago Mayor in the North, mainly Rivers and streams provide about tant water resource for the arid in Peruvian territory. The Lago 2 45 % of the water inflow to Lake Bolivian Altiplano. Menor (approx. 1400 km ) in the Titicaca, i.e. about 20 % less than South, with a depth of 20-30 m, is direct precipitation, and almost the mostly located in Bolivia and con- Evaporation is therefore the whole salt inflow. The major rivers nected to the Lago Mayor through largest water balance term and are Rio Ramis (mean discharge 74 possibly the one which shows the the Tiquina Strait which is 850 m m3/s), Rio Coata (47 m3/s), Rio least interannual variability. Un- wide. The third lake region is the Have (38 m3/s), Rio Huancane (19 fortunately, evaporation is also Bahia de Puno, a large (approx. 3 3 2 m /s), Rio Suches (11 m /s), Rio the most difficult parameter to 500 km ), shallow, highly contami- Keka, all flowing into the Lago measure with good accuracy. nated bay in front of the town of Mayor; and Rio Tiwanacu which Puno on the western coast of Lago flows in the Lago Menor. The dis- Mayor. The Autoridad Autonoma Bina- charge varies largely in the course cional del Lago Titicaca (ALT) Lake Titicaca is the major water of the year, from practically zero [Binational Autonomous Au- source for about 1,000,000 people during the dry season up to 10 thority for Lake Titicaca] living in the lake region. In the na- times the average discharge in the tive tradition the lake is consi-dered rainy season. After the strong drought which a gift of god, and is invoked by struck the Altiplano in summer riparians as father of life. Diffuse groundwater leakage into 1982-1983 - the rains were less the lake from coastal is Water balance of Lake Titicaca than the half of the average believed to represent a negligible amount, in a possibly fortuitous As in all closed lakes, the water term of water balance. coincidence with a strong El Nino balance of Lake Titicaca is unsta- event-the Peruvian Government ble, as indicated by the lake level Evaporation from the lake is strong established the Proyecto Especial oscillations of up to 5 m recorded in and accounts for more than 95 % of del Lago Titicaca (PELT), with the current century. The minimum the water losses. Data provided by Headquarters in Puno, with the level (3807 m a.s.l.) was attained Class A evaporation pans range general task of fostering studies during the long drought of 1940- from about 2000 mm/a at Suana and activities leading to a better 1945, and the maximum level Island and Puno, to 1300 mm/a at assessment, exploitation and (3812 m a.s.l.) was reached in Conima and Copacabana and 1200 management of the resources of 1987 after some rainy years. It is mm/a at Isla del Sol. However, the region, including farming, cat- therefore of interest to briefly dis- these evaporation data are affected tle breeding, fishery, water re- cuss here the water balance of by the pan conditions and tempera- sources, etc. Lake Titicaca. In fact, a good as- ture variations, which may differ sessment of water inflow and out- considerably among stations. About the same time the prepara- flow is of paramount importance for Therefore, it is difficult to assess tion of a Binational Master Plan the lake water management. the lake evaporation rate with suffi- for water resources management cient accuracy from these data. and protection-prevention of Direct precipitation over the lake floods, started with the support of

Quarterly No. 8 / 9, December 1999 - Page 6 WATER & ENVIRONMENT NEWS the European Community. In the isotopic results is being made. It interpretation can be attempted. following year the Governments of would be desirable, however, that We summarize below the major Peru and Bolivia established the sampling and measurements con- observations and conclusions, and Autoridad Autonoma Binacional tinue for some years in order to indicate activities to continue or del Lago Titicaca (ALT) with Head- obtain statistically meaningful data. initiate. quarters in La Paz, Bolivia. PELT Closed lakes, where the major became the executive arm of ALT 2. The PELT boat was equipped fraction of the inflowing water is and was converted into a bina- with a new system for deep water removed by evaporation, exhibit a tional body. The zone of activity sampling by Nansen bottles and significant enrichment in heavy was extended to the whole Lake with probes to measure water tem- isotopes. This is due to the fact Titicaca basin which has a surface perature and conductivity at depth. 2 that the isotopically light water of 144,000 km including the Boli- molecules (1H 16O) evaporate vian Altiplano. Among the PELT 2 3. A new evaporation pan was con- from the liquid surface at higher undertakings, worthy of mention is structed, in which the water temper- rate than those containing heavy the creation of the lake research ature is fixed by using the lake isotopes (2H or 18O), the concen- centre in Chucuito, about 20 km water as thermostatic fluid. The en- tration of which increases in the South-east of Puno. ergy for the lake water circulation residual liquid phase. Therefore, pump is provided by solar panels. Lake Titicaca water, like all closed The IAEA Technical Cooperation The whole system is now installed lakes, is enriched in heavy iso- Project RLA/08/022 and tested in the Taquile island. topes. In particular, the Lago Mayor is enriched by about 60 %o In December 1997, the Interna- 4. The equipment of the Instituto de in 2H and 12 %o in 18O with respect tional Atomic Energy Agency Investigaciones Quimicas was up- to rivers and precipitation feeding launched the Technical Coopera- graded and strengthened with a the lake. Due to the large size and tion Project RLA/08/022 for the ap- new ion chromatograph to cope depth, and the relatively long resi- plication of isotope techniques to with the high number of chemical dence time of water, the isotopic the investigation of Lake Titicaca, analyses to be done. Intercalibra- and chemical composition of the for which ALT and PELT were the tion with the chemical laboratory of Lago Mayor is very uniform and major counterparts. Other impor- the Istituto di Geocronologia e constant in time. tant counterparts were the Instituto Geochimica Isotopica (Pisa) is go- Peruano de Energia Nuclear ing on. A further enrichment of about 10- (IPEN) in Lima and the Instituto de 20 %o in 2H and 2-3 %o in 18O is Investigaciones Qufmicas (IIQ) of 5. In April 1999, a Regional Course observed in water of Lago Menor the Universidad Mayor de San An- on Isotope Limnology was held in with respect to the Lago Mayor, dres in La Paz. The major objec- Chucuito on the Lake Titicaca, accompanied by a salt concentra- tive of the project was to improve which was attended by scientists tion and conductivity increase of the lake chemical and isotopic bal- and technicians from Columbia, about 20-30 %. The isotopic and ances in order to better assess the Cuba, Mexico, Nicaragua, and chemical composition of the Lake water resources available from the Venezuela, in addition of those Menor is less stable and uniform lake. This objective implied the or- from Peru and Bolivia. than that of Lago Mayor, due to ganization of an extensive network the shallow depth and short resi- of stations for sampling the lake 6. Lake samples were taken for de- dence time of water. Isotopic and and its major tributaries, precipita- termining the freon concentration chemical values similar to those of tion, groundwater, and the execu- deriving from dissolution of anthro- Lago Mayor are found in the tion of experiments to improve the pogenic freon present in the atmo- Tiquina Strait, while intermediate evaporation estimate. The sam- sphere. Freon concentration is de- values are observed at the sam- pling network and frequency were termined by gas chromatography at pling site closest to the Strait in the established in 1997, it includes 18 the IAEA Isotope Hydrology labora- Lake Menor. This indicates that lake sites to be sampled bi- tory. the water movement is essentially annually at various depths, 9 rivers unidirectional from the Lago Mayor and 11 precipitation stations for 7. Various fellowships have been to the Lago Menor, and there is no monthly sampling, and a number of awarded and the training for staff significant return of water from the wells and springs for groundwater will continue in 2000. Lago Menor. sampling. On the contrary, the bulk of Puno Preliminary short discussion of The activities carried out to present Bay water is isotopically and the Lake Titicaca data with the IAEA support are summa- chemically almost undistinguish- rized below. able from the Lake Mayor, indicat- Isotopic and chemical data on Lake ing that the water moves in both Titicaca, obtained within the frame 1. About 800 water samples were directions, i.e. from the lake into of the IAEA Technical Co-operation collected and their chemical and the bay and vice-versa. The identi- project RLA/08/022 are accumulat- isotopic composition determined. fication of lake water major circu- ing, and a preliminary, qualitative A first assessment of chemical and lation patterns is important not

Quarterly No. 8 / 9, December 1999 - Page 7 WATER & ENVIRONMENT NEWS

only for making water balances but the river, in spite of the fact that ing the evaporation rate. The new also for predicting the contaminant chemistry and isotopic composi- evaporation pans, when available dispersion and fate. tion of rivers are to some extent in sufficient number, will hopefully buffered by groundwater. This may contribute to reduce the current In all cases, the lake is isotopically require a long period of observa- discrepancies between measure- quite different from groundwater in tion, in order to fully understand ments carried out at different lake coastal aquifers (typical values vs. the processes governing the iso- stations, thus improving the relia- V-SMOW: 518O -15 %o and 52H topic and chemical variations as a bility of evaporation rate measure- -120 %o), where in principle signifi- function of river discharge. To this ments. cant lake water contributions could aim, the sampling frequency may be easily identified. 1 need to be increased during Marco A. Paredes Riveros & Roberto Gonfiantini2 As already said, the isotopic and floods. Generally speaking, the de- chemical composition values are sign, installation and management (1) PELT, Puno, Peru quite uniform throughout the whole of the sampling network may need (2) istituto di Geocronologia e Lago Mayor indicating that the lake to be revised on the basis of the Geochimica Isotopica del CNR, is vertically and horizontally well acquired experience. Pisa, Italia mixed. Thus, the application of Evaporation rate is the major un- For more information see C. Dejoux and A. models based on the isotopic and known in the Lake Titicaca bal- lltis (Editors): Lake Titicaca. A Synthesis chemical material balances is quite ance. Evaporation experiments will of Limnological Knowledge, Kluwier Aca- straightforward. demic Publishers, Dordrecht, 1992. be carried out in the special evapo- More difficult is the estimate of ration pans being built for the pro- mean values of input waters, and ject {one is already installed in the in particular the mean isotopic Taquile Island). The scope is to composition of rains and rivers and establish the steady state isotopic the chemical composition of rivers. composition of the evaporating wa- Large variations occur for the rain ter, and from this to contribute to isotopic composition as well as for assessing the characteristics of the evaporation pans for determin-

„•%*-

Meteorogical station in Taquile Island, Lake Titicaca (Photo credit: PELT)

ALT/IAEA joint Course on Isotope Limnology, Chucuito, Peru, 1999 Openning ceremony (Photo credit: PELT)

Quarterly No. 8 / 9, December 1999 - Page 8 XA0054566 WATER & ENVIRONMENT NEWS THE EVAPORATION PAN TECHNIQUE REVISITED: OLD THEORY AND A NEW APPLICATION FOR TIME= WEIGHTED SYNOPTIC TRACING OF THE ISOTOPIC COMPOSITION OF ATMOSPHERIC VAPOUR

i eliable and consistent characterization of the Canada, an arid region that is typically characterized ^stable isotope composition of atmospheric wa- by 15-20% wetland area because of underlying per- ter vapour and its temporal variability are important mafrost, has prompted development of a new ap- prerequisites to the wider application of isotope proach for characterizing the isotopic composition of mass balance methods in atmospheric and water vapour-phase atmospheric moisture and its variability. balance studies, at scales ranging from the typical The method employs conventional evaporation pans atmospheric general circulation model (GCM) grid- and is especially suitable for use in water balance square domain down to and including field-based studies of lakes at local to regional scales. Due to the studies conducted in small watersheds or at points pronounced seasonality of precipitation, proportion- near the ground surface. Precipitation sampling ately large snowmelt input and short thaw season, conducted within the WMO/IAEA Global Network lakes in the region rarely attain isotopic steady state, for Isotopes in Precipitation (GNIP) and affiliated but instead often display systematic seasonal enrich- national networks has made significant contribu- ments and spatial trends that are strongly dependent tions to our understanding of temporal and spatial on the shifting isotopic composition of local atmo- variations in the isotopic composition of atmo- spheric vapour. spheric moisture using the equilibrium assumption, i.e., that the isotope distribution in precipitation is an Intensive experiments (Gibson et al. 1999) have "equilibrium proxy" for that in vapour, based on demonstrated that five- to ten-day flux-weighted assumed temperature-dependent equilibrium iso- records of the stable isotope content of ambient atmo- tope exchange effects. However, because precipi- spheric vapour can be obtained through careful moni- tation predominantly occurs as discrete events sep- toring of the isotope and mass budgets of evaporation arated in time, especially in arid or seasonally-arid pans, coupled with the well-known layered resistance climates, liquid-phase sampling may not provide a model of Craig and Gordon (1965). This conclusion is good time-weighted estimate of vapour-phase iso- reinforced by successful use of pan-derived vapour topic composition, nor does it provide information 818O and 52H values in a detailed isotope-mass bal- on changes occurring between precipitation events. ance analysis of a small lake at Lupin, Nunavut, which This is further complicated by uncertainty in the yielded evaporation rates in close agreement (±10%) relation between cloud temperature and climatolog- with results based on Bowen ratio energy balance and ical temperature, which is difficult to ascertain with- aerodynamic profile calculations (Gibson et al. out specific knowledge of the atmospheric bound- 1996a,b). ary layer structure. Conversely, improved under- standing of the isotopic relations between precipita- Previous evaporation pan experiments mainly fo- tion and vapour could potentially provide important cused on investigation of isotope exchange parame- hydroclimatological insight, for example yielding ters using relatively small pans sensitive to rapid clues about the nature and causes of variations in 18 2 changes in ambient conditions (e.g. Gat 1970; Wel- the slope of local evaporation lines in 8 O - 8 H han and Fritz 1977; Allison et al. 1979; Allison and space, or providing information for evaluation of Leaney 1982). In contrast, the new approach utilizes atmospheric feedback or throughput in coupled standard class-A pans, which have sufficient volume evaporative systems (e.g. Gat and Bowser 1991). (220 I) to buffer short-term transient variations in atmospheric conditions, justifying the assumption of Routine sampling of atmospheric water vapour us- constant kinetic isotopic fractionation effects in con- ing cryogenic traps has not been widely adopted in cert with precisely measured temperature and relative field studies, primarily due to logistical constraints, humidity to derive vapour isotopic composition. and it has rarely been integrated within precipitation sampling networks. Moreover, field-based sam- A major strength of the method is that pan-derived pling campaigns are commonly of rather limited vapour isotopic compositions are naturally flux- duration, yielding short-term data sets that may weighted, as represented in the Craig and Gordon have limited applicability at water balance time- (1965) model, and can thus be applied directly to scales or may be poorly suited for meaningful com- isotope mass-balance analysis of nearby lakes. For- parison with records of precipitation isotope compo- tunately, although the use of kinetic isotope effects sition. Challenges also exist to design efficient that are inherently dependent on the turbulence trapping systems, because of the potential for frac- regime of the boundary layer is a potential weakness, tionation arising from incomplete vapour recovery.

Field work in remote areas of continental northern

Quarterly No. 8 / 9, December 1999 - Page 9 WATER & ENVIRONMENT NEWS this factor seems to be remarkably uniform on ular value for stations receiving little or highly variable synoptic time scales or, alternatively, it can be precipitation. As studies in Canada have shown, indexed on the basis of other routinely measured such data are applicable in hydrometeorological stud- climatological data. ies at various spatial and temporal scales. Significant potential also exists for incorporation into major inter- As an example, Figure 1 shows a comparison of national hydroscience initiatives, like the ongoing pan-derived atmospheric vapour 818O and 82H at continental-scale regional hydrologic studies within the Lupin study site with data obtained from cyro- the Global Energy and Experiment genically trapped vapour during the daytime and (GEWEX), as well as being a resource for validation calculated vapour 818O and 82H assuming isotopic of the global isotope field as depicted by atmospheric equilibrium with discrete occurrences of precipita- GCMs field as depicted by atmospheric GCMs. tion. The pan-derived values clearly provide com- parable records of temporal changes in atmo- References spheric moisture 818O and 82H. Note that the daytime vapour-trap estimates are biased relative Allison, G.B. and Leaney, F.W. 1982. Journal of Hydrology 55, to the daily pan-derived estimates because of the 151-161. influence of vapour from local lakes and tundra Allison, G.B., Brown, R.M. and Fritz, P. 1979. Journal of Hydrol- bryophytes. ogy 42, 109-127. The results suggest that isotopic sampling of exist- Craig, H. and Gordon, L.I. 1965. In: E. Tongiorgi (Editor;, Stable ing, conventionally operated class-A evaporation Isotopes in Oceanographic Studies and Paleotemperatures, pans could offer a straightforward and cost- Lab. Geologia Nucleare, Pisa, 9-130. effective solution to the problem of documenting the shifting isotopic distribution in atmospheric mois- Gat, J.R. 1970. In: Isotopes in Hydrology, 1970. IAEA, Vienna, ture. The method could provide continuously- 151-162. weighted records of vapour S18O and 82H for use in Gat, J.R. and Bowser, C.J. 1991. . In: H.P. Taylor, J.R., O'Neil, isotope-climate research, which would be of partic- and I.R. Kaplan (Editors), Stable Isotope Geochemistry: A Tribute to Samuel Epstein, Special Publication No. 3, The Geochemical Society, San Antonio, Texas, 159-168. Gibson, J.J., Prowse, T.D. and Edwards, T.W.D. 1996a. Hydro- logical Processes 10, 1369-1382. Gibson, J.J., Prowse, T.D. and Edwards, T.W.D. 1996b. Nordic Hydrology 27, 1-24. Gibson, J.J., T.W.D. Edwards and Prowse, T.D. 1999. Journal of Hydrology 1M, 55-74. Welhan, J.A. and Fritz, P. 1977. Geochimica et Cosmochimica Acta 41, 682-686.

JJ. Gibson and T.W.D. Edwards Figure 1. Time-series of step-wise atmospheric Department of Earth Sciences vapour S18O and 82H values derived from class-A and Environmental Isotope Laboratory pans (solid lines), average of moisture collected daily University of Waterloo, in vapour trap at height of 6-m over tundra (bold Waterloo ON N2L 3G1 CANADA lines), and estimates of vapour 818O and 82H based on the assumption of isotopic equilibrium with dis- crete occurrences of precipitation (diamonds). (See Gibson etal. 1999.)

Technical Review

Quarterly No. 8 / 9, December 1999 - Page 10 WATER & ENVIRONMENT NEWS J

GROUNDWATER RENEWAL, IN WATER ISOTOPE RESPONSE TO DYNAMIC CHANGES SCARCE AREAS IN GROUNDWATER SYSTEMS DUE TO LONG-TERM EXPLOITATI ON he final coordination meeting of the CRP enti- Ttled "Isotope based assessment of groundwa- np*he first Research Co-ordination Meeting of the ter renewal rate in water scarce areas" was held in JL recently initiated CRP entitled "Isotope response to dynamic changes in groundwater systems due to Vienna, from 18 to 21 October 1999. Fourteen long-term exploitation" was held in Vienna, from 8 to Institutes were involved in this project which is now 12 November 1999. The main motivation for the closed. Detailed information on physiography, initiation of this CRP was the fact that during the last lithology, rainfall, unsaturated zone moisture con- few decades major sources of freshwater have been tent and a variety of chemical and isotopic con- exploited to meet the ever increasing demand for stituents was collected at a total of 44 benchmark water supply to different sectors (domestic, agricul- sites located mainly in arid regions. The purpose tural and industrial). The stresses imposed on the was to evaluate the use of chemical and isotopic available water resources due to man's impact (exploitation, release of pollutants through domestic/ tools to understand history of recharge and to esti- industrial waste waters, and agricultural practices) mate recharge rates. Evaluation of chloride and have resulted in many parts of the world in depletion tritium concentrations from unsaturated zone pro- of the available reserves as well as the deterioration files (up to a depth of 45 m) provided recharge rate of water quality. This impact is more pronounced in estimates ranging from fractions of a millimetre to arid and semi-arid regions. Therefore, the CRP is tens of millimetres per annum. The methodology directed mainly towards making an assessment of the adopted and verified through applied field research potential utility of isotopes in the quantitative under- standing of the long-term changes induced by ex- has proved the applicability of unsaturated zone ploitation. Furthermore, applied field research in se- isotopic/hydrochemical profiles for estimation of lected bench- systems with different hydrogeo- natural renewal rate of aquifers in such arid re- iogical settings and spatial scales will enable method- gions, and has provided a unique approach for this ological developments for more reliable predictions of purpose. The results and findings of the CRP will be future behaviour of the systems under different ex- published as a TECDOC by the Agency in 2000. ploitation scenarios.

Y. Yurtsever Y. Yurtsever

ISOTOPE HYDROLOGY CALENDAR

March RCM on The use of tracers and stable isotopes in surface water pollution, RC-701.2 - Vienna,13 -17 April Executive Meeting for Water Resources Managers, 2000 RAS/8/084-Taejon, ROK IAEA MEETINGS AND TRAINING \AEA Meeting Categories February Advanced course on numerical modelling - AGM: Advisory Group Meeting; RAS8084 - Bangkok, Thailand, 14-25 RCM: Research Co-ordination Meeting; CS: Consultants Service; CM: Consultants Meeting; SYM: International Symposium

Quarterly No. 8 / 9, December 1999 - Page 11 WATER & ENVIRONMENT NEWS

GNIP-SCIENTIFIC STEERING COMMITTEE MEETING

kn 1 and 2 July 1999, the first be formed to consider the gaps *WMO 'meeting of the Global Network and needs for more stations. for Isotopes in Precipitation - Scien- - Director of the WCRP tific Steering Committee (GNIP- - Some regions have already been SSC) was held at the IAEA Head- identified and should be contacted - to be suggested by WMO quarters in Vienna. The scope of in order to start/continue sampling the GNIP-SSC, as defined in the (Brazil, tropical Andes, West * IGBP / PAGES Memorandum of Understanding re- Africa, India, Central Asia). lating to GNIP signed by the IAEA - to be suggested by PAGES and the WMO, is to "provide advice - The SSC recommended that the to the IAEA and WMO on matters networks of Global Atmosphere * Experts representing the sci- related to the GNIP and to the Watch (GAW) of WMO be used as entific community GNIP Data Base". much as possible for the GNIP networks. - Environmental Physics: The main recommendations U.Schotterer, ISOHYC, Switzer- made by the Steering Committee Composition of the first GNIP- land are: Scientific Steering Committee - Meteorology: - WMO/IAEA should consider ap- The first committee members have S. Hastenrath, University of proaching meteorological/hydrolog- been selected in order to present a Wisconsin-Madison, USA ical services to help in the manage- good equilibrium between scien- ment of national networks. tifics from the United Nations - Climatology: agencies and scientifics from re- M. Latif, Max Planck Institute for - A list of national networks on search institutes. Both climatolo- Meteorology, Germany isotopes in precipitation should be gists and hydrologists are repre- completed. sented. The SSC expressed inter- The full report of the first GNIP- est in having additional members SSC and more information about of the hydrological/hydrogeologi- - IAEA should compile all the publi- the Global Network for Isotopes in cal communities in the GNIP com- cations using the GNIP data, and Precipitation can be requested mittee. this list should complete the infor- from Laurence Gourcy mation given to the national net- works and GNIP stations. *IAEA

- The SSC recommended including - Head of the Isotope Hydrology [email protected] scientists from other continents Section (Asia, Australia, South America) in the SSC. - Isotope Hydrology Section staff - The SSC asked that a task group in charge of the GNIP

ISOTOPE HYDROLOGY INFORMATION SYSTEM ISOHIS he ISOHIS database allow gathering, storage Tand dissemination of isotope, chemical, hydroge- ological and geographical data from water studies around the world. The software for entering and verifying records, and for managing local/regional ISOTOPE HYDROLOGY fNFORMA IION S YSTEM databases called Data Entry Module is available since May 1999.

You can download directly the software and User Manual in ftp://ftp.iaea.org/dist/isohis/ or request the CD-ROM from Laurence Gourcy.

Quarterly No. 8 / 9, December 1999 - Page 12 WATER & ENVIRONMENT NEWS

TC ACTIVITIES

GEOTHERMAL ENERGY reservoir management. nagement of the geothermal re- RESOURCES - RESULTS The project included three sets of sources. AND ACHIEVEMENTS activities: The regional programme reco- workshop to assess this re- • Field investigations using isotope gnized the availability of scientific Agional project was heid in and geochemical techniques for the expertise in the countries of the November 1999 in Indonesia. exploration of low-medium tempera- region. Manpower resources have The workshop was attended by ture geothermal systems, commonly been developed, information ex- representatives from China, In- occurring hydrological problems as- changed and disseminated, and the donesia, Philippines and Thai- sociated with exploitation and rein- applications of isotope techniques land, who collaborated in the jection in high temperature systems, to practical hydrological and geo- project, as well as by counter- as well as environmental impacts chemical problems associated with parts of on-going IAEA Techni- due to waste water reinjection on the exploration and management of cal Cooperation projects on shallow groundwater. geothermal reservoirs accelerated. geothermal energy in El Sal- The regional collaboration has har- vador, Costa Rica, Ecuador, • Interlaboratory comparison which nessed and optimized the available Peru and Guatemala. assessed the quality of chemical and expertise in participating countries isotope analyses in the participating consistent with the intentions of Regional Project RAS/8/075 laboratories. TCDC. was implemented with the gen- eral objective to support the uti- • Development of a regional J. Gerardo-Abaya lization of isotope and geochem- database on geothermal waters as a ical techniques for geothermal pre-requisite to planning and ma-

ISOTOPE FOR IMPROVED concepts for isotope data interpre- The initial training and hands-on DRINKING WATER tation in groundwater hydrology exercises on numerical modelling REOURCES MANAGEMENT were discussed. The various ap- were provided on MODFLOW and proaches to data processing and MT3D which will be used in the he first assessment work- interpretation were exposed during project for development of site- Tshop of the UNDP/IAEA/RCA the presentations and will be useful specific dynamic simulation models Project RAS/8/084 was held in for participants to consider in their for and transport Vietnam from 27 September to 8 continuing investigations. for the study sites included into the October 1999. project. The lectures and computer The participating countries are en- exercises provided the capabilities A workshop reviewed the results couraged to facilitate transfer of for use of the software, including of Interlaboratory comparison for technology through regular com- data input, simulation, calibration chemistry. The role, strategy, de- munication. Countries with estab- and post-processing of the simula- sign and concepts in isotope in- lished expertise in the fields of iso- tion results. vestigations, formulations of con- tope hydrology and modelling reit- ceptual models for quantitative erated their willingness to impart interpretation of isotope data in information to less experienced hydrology, and general modelling Member States. Y. Yurtsever/J. Gerardo-Abaya

WORKSHOP ON ISOTOPE ing regional Technical Co-operation overview of the principles and ap- DATA INTERPRETATION - Model Project RAF/8/029 and was plications of isotope hydrology. PROJECT RAF/8/029 attended by 14 participants from Lumped parameter models to in- the 7 countries involved in the re- terpret groundwater isotopic data regional workshop on Isotope gional project, namely Kenya, as well as hydrologic models were A Data Interpretation and Inte- Madagascar, Namibia, South introduced with emphasis on the gration in site conceptual models Africa, Tanzania, Uganda and Zim- hands-on use of MULTIS and was held from 27 September to 8 babwe. In addition to provision of VISUAL MODFLOW. The Isotope October at the Schonland Re- training, the workshop was also Hydrology Data base (ISOHIS) de- search Centre, University of Wit- aimed at reviewing the status of the veloped by the Isotope Hydro-logy watersrand, Johannesburg, South Model Project and updating the Section of the IAEA was also intro- Africa. The Course was organised workplan. duced. within the framework of the ongo- The workshop provided a detailed C. B. Gaye

Quarterly No. 8 / 9, December 1999 - Page 13 XA0054567 1/ WATER & ENVIRONMENT NEWS

LABORATORY ACTIVITIE 1.0 2"" 1NTERLABORATORY COMPARISON FOR Ccdsensus Value

DEUTERIUM AND OXYGEN-18 Waited mean value rejected ajGiers

ANALYSIS OF WATER SAMPLES Standard dewaten(1a: . .rejXrt&J standard uj)certa;rfy lie; oliieweighledmeanvaHje 0.6 he IAEA Isotope Hydrology Laboratory orga- nd Tnised in 1998/99 the 2 interlaboratory com- 0.4 parison test for the analyses of hydrogen and oxygen isotope composition of water. The test was open to all laboratories engaged in isotope analy- ses of water samples world-wide. U.O

The main objective of this exercise was to help the °-0.2 laboratories to assess their precision and accuracy -0.4 for the range of 5 0 and 5 H values normally observed in meteoric waters. More than 115 labo- •0.6 ratories from 43 countries indicated their willing- ness to participate in the exercise and received •0.8 four water samples (OH-1 to OH-4) for analysis. -1.0 STATISTICAL EVALUATION OF THE RESULTS Figure I: S-shape plot of 8 Deuterium values sample OH-1 in ascending order versus the Laboratory During this intercomparison exercise all partici- Identification numbers. For explanations see text. pants remained anonymous. Their full addresses are listed in the Annex of the Report, but no link to their identifying lab number used in the data pre- mean of the whole group (dashed line). This shift sentation is given (except the IAEA laboratory, towards more depleted values is systematically found ID no. 10). Only the participants were able to iden- for all four water samples and might be explained by tify themselves. By the end of April 1999, 87 of the evaporation of improperly stored internal standards. participating laboratories had reported their data. CONCLUSIONS Results of seven laboratories, selected by the IAEA for their high analytical quality, were used to The participating laboratories are a representative assign a "consensus" value for the analyses with portion of the entire analytical community engaged in the lowest attainable uncertainty. this type of measurements. Therefore, it is believed that the results of this test properly reflect the current Figure 1 is an example of the way the evaluated situation with respect to accuracy and precision of data set was presented in the IAEA report. The stable isotope analyses of water samples. 518O-values of the sample OH-1 are sorted in ascending order and plotted versus the laboratory The apparent interlaboratory precision (one-sigma ID numbers. Vertical bars indicate the standard level), derived from the whole pool of the analysed uncertainty (1 0) quoted by each laboratory. The results, is in the order of 0.11 %o for 8 O and 1.3 %a solid line represents the adopted consensus value. for 8 H. This is comparable with the typical standard The dotted line represents the weighted mean precision reported by the majority of the laboratories. value as calculated from the whole set of laborato- ries with the standard uncertainty indicated by the • No major improvement of this performance indica- two dotted lines. The data presentation in such an tor could be detected with respect to that in 1995 (1st S-shaped plot shows the large number of laborato- interlaboratory comparison). ries participating in the intercomparison exercise and the range of values reported by these laborato- • At least 25% of the participating laboratories under- ries. Full circles indicate the accepted values, open estimate their overall standard uncertainty and/or circles indicate the rejected outliers. Visually, one suffer from systematic effects of varying nature and might notice the importance of the reported stan- are therefore identified as outliers (fig. 1, open cir- dard uncertainty of each laboratory in respect to cles). the rejection of values: Deviating values might still be accepted as long as the laboratories state a reasonable uncertainty and vice versa. • No significant dependence of the obtained 5-values Finally, one should realise the shift between the on the type of the sample preparation procedure consensus value (solid line) and the weighted could be detected.

Quarterly No. 8 / 9, December 1999 - Page 14 WATER & ENVIRONMENT NEWS

• The results for the entire population do not show The final report "IAEA 2" Interlaboratory Compari- normal distribution. A small but significant shift son for Deuterium and Oxygen-18 Analysis of Water towards more negative 5-values between the con- Samples" will be made available as PDF document sensus value and the weighted mean value of the for download on the homepage of the IAEA Isotope entire population is identified. Since an evapora- Hydrology Laboratory under: http://www.iaea.or.at/ tive loss of only 0.1% of the initial mass of the used Droarammes/rial/pci/isotopehydroloQv/hvdroloav internal standard or of an improperly stored VS- main,htm MOW sample would be sufficient to explain the observed isotope shift in the observed order of J. Lippmann / M. Groning 1B ? 0.04 %o for 5 O and 0.3 %o for 5 H, such an evapo- rative enrichment with time after the calibration against VSMOW might be one possible explana- tion.

I AGM NEWS I XA0054568 CHALLENGES AND NEW TECHNIQUES FOR LIGHT ELEMENT STABLE ISOTOPE MEASUREMENTS

n Advisory Group Meeting on Stable Isotope neous measurements, non-destructive determina- ARatio Measurements by GC-IRMS and tions and reduced contamination risks, e.g. avoiding Spectroscopy was held from 20-23 September any isobaric interference. Even though tey are rela- 1999 in Vienna. The meeting aimed to review the tively young techniques, the analytical precision is current status of emerging techniques for the deter- not far from that achievable with mass spectrometry mination of stable isotope ratios of light elements. techniques. Further improvements are expected in Besides isotope hydrology and isotope geoche- the future, which will make these techniques widely mistry, the range of disciplines using isotope signa- competitive to mass spectrometry. Despite recent tures has broadened significantly during the last improvements, the measurement of stable isotopes years, adapting and using isotopes to, for example, is still reported as ratios relative to standards of characterise physiochemical or biological path- known isotope ratio. The creation of reliable isotope ways, fingerprint substances and trace material standards or international reference materials for fluxes. As a consequence, the requirements of the both techniques is critical not only to compare re- instruments have changed significantly in some sults between runs on a single machine, but also to fields. Several new instrumental developments relate them to other machines and laboratories. The were discussed in the meeting with a focus on (1) requirements for isotope standards have increased Continuous Flow-isotope Ratio Mass Spectrome- dramatically with the new technologies, also due to ters (CF-IRMS) and (2) optical techniques for sta- the wider range of applications. As a result, there are ble isotope determinations. new challenges for the isotope community to extend the availability of international reference materials. Continuous Flow IRMS is a generic term for IRMS This meeting defined the most urgent needs for such instruments coupled on-line to preparation or sepa- materials and gave a starting point for a new field ration systems like Elementary Analysers, Gas and direction for the Stable Isotope Reference Mate- Chromatographs, and Combustion or Reduction rials Program of the IAEA. Interfaces. The key features of CF-IRMS include reduced sample size and analysis time and isotope M. Groning measurements of individual compounds in com- plex mixtures.

Optical techniques use laser beams for measuring the absorbance of different spectral lines for the various isotope species, e.g. 12C16O16O vs. I3Q16Q18Q jn ^e jnfrarecj regjon or for measuring the electrical response of gas discharge to optical perturbation. Various detection techniques are used, with significant improvements realised re- cently, offering some operational advantages such as simplified instrumentation, multiple simulta-

Quarterly No. 8 / 9, December 1999 - Page 15 WATER & ENVIRONMENT NEWS

STAFF CHANGES IN THE ISOTOPE HYDROLOGY SECTION

Mira Gattin left the IAEA at the end of December Departures 1999 after working in the Isotope Hydrology Labora- tory for more than 30 years. As a chemical engineer she started to work on tritium analysis and switched later to stable isotope mass spectrometry, where she was responsible mainly for sample analyses for 8D, 813C and 518O. At the same time she was responsible for the training of many dozens of fellows in the field of stable isotope mass spectrometry. Her engage- ment, careful work attitude and friendly personality contributed considerably to the success of the labo- ratory. We wish her all the best for the new phase of life after her retirement.

Dr. Klaus Froehlich retired from the Agency at the end of July. Dr. Froehlich joined the Agency in 1988 as senior staff of the IHS and served as Section Head for the last five years. During his tenure as Section Head, he facilitated efficient collaboration with colleagues world-wide to foster further development and application of isotope techniques in hydrology and related environmental fields. Isotope Hydrology has increased its visibility Arrival:

among the Member States, and the programme "..- '•

was recognized by the General Conference as a I" significant achievement of the Agency. Among other initiatives, he was responsible for conceiving 1 and launching Water and Environment News, es- Sl-L- '.ir- ...„.„ tablishing a Memorandum of Understanding on the Global Network for Isotopes in Precipitation (GNIP) between the IAEA and the WMO, and providing the GNIP database through Internet to the scientific community. He also initiated the setting up of the Isotope Hydrology Information System (ISOHIS). During the last two years he enhanced efforts towards launching a long-term Inter-Agency (UNESCO, WMO, WCRP etc.) collaborative pro- Michael van Duren joined the Isotope Hydrology gramme called International Programme for Iso- Laboratory in December 1999. By profession, he is topes in the Hydrological Cycle. a food chemist and previously worked in various branches of the Agency's Laboratories in Seibers- He can be contacted at the following address : dorf for the past 15 years. He will ensure the Viktor-Wittner-Gasse 63/7 continuity in mass spectrometric measurements in A-1220, Vienna, Austria the Isotope Hydrology Laboratory. e-mail : [email protected] He can be contacted at: o o Telephone : +43-1-2600-21765 o e-mail: [email protected] d> at Water and Environment News, Isotope Hydrology Section, International Atomic Energy Agency, Wagramer Strasse 5, P.O.Box 100, A-1400, Vienna, Austria. Printed by IAEA in Vienna

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