Environmental isotopes as a useful tool for studies at mixed uranium mill tailings sites

Groundwaters in the area of a mixed landfill (domestic waste above uranium mill tailings) in Dresden (Saxony, Germany) were investigated for their isotope signatures to distinguish between different groundwater types. To determine between the two contamination sources (waste and uranium mill tailings) a multi parameter interpretation was done using both, the main hydrochemical parameters the radionuclides 234U, 238U, 226Ra and 222Rn as well as the environmental isotopes of the elements hydrogen, oxygen, sulphur and carbon. The seepage water from the landfill shows higher delta34S, delta18O and tritium values as the inflow. The tritium values give an idea about water movement in the dump and mean residence time of the groundwater. The water in the dump shows varying delta13C values which indicate different processes occurring in the dump.     

Evaluation of the Sulfate Dynamics in Groundwater by Means of Environmental Isotopes

Abstract

Elevated sulfate concentrations and their heterogeneous distribution in the drinking water catchment area Torgau-Mockritz (Germany) were investigated by means of multiple isotope signatures such as δ³⁴S, δ¹⁸O-H₂O, δD, tritium, and ⁸⁵Kr. δ³⁴S values of the groundwater sulfate vary between -19…+ 37‰ CDT. No simple correlation exists between sulfate concentrations and δ³⁴S. Superimposition of different sulfur sources and mobilization processes combined with a complicated groundwater movement create a complex distribution pattern. The oxidation of reduced sedimentary sulfur has to be regarded as a main source of dissolved sulfate at least regionally. Tritium and ¹⁴C data revealed that old groundwater can be excluded as source for high sulfate contents. Correlated temporal variations in the concentrations of tritium and sulfate are observed in deeper sampling positions. Highly variable δ¹⁸O and δD, as detected in parts of the catchment area, indicate local influences of surface water infiltration into the aquifer. The spatial distribution of isotope signatures enables the identification of zones with descending younger water or hindered groundwater movement and hence provides useful hints for flow modeling.     

Estimation of lake water—groundwater interactions in meromictic mining lakes by modelling isotope signatures of lake water

Abstract

A method is presented to assess lake water–groundwater interactions by modelling isotope signatures of lake water using meteorological parameters and field data. The modelling of δ¹⁸O and δD variations offers information about the groundwater influx into a meromictic Lusatian mining lake. Therefore, a water balance model is combined with an isotope water balance model to estimate analogies between simulated and measured isotope signatures within the lake water body. The model is operated with different evaporation rates to predict δ¹⁸O and δD values in a lake that is only controlled by weather conditions with neither groundwater inflow nor outflow. Comparisons between modelled and measured isotope values show whether the lake is fed by the groundwater or not. Furthermore, our investigations show that an adaptation of the Craig and Gordon model [H. Craig, L.I. Gordon. Deuterium and oxygen-18 variations in the ocean and the marine atmosphere. In Stable Isotopes in Oceanographic Studies and Paleotemperature, Spoleto, E. Tongiorgi (Ed.), pp. 9–130, Consiglio Nazionale delle Ricerche, Laboratorio di Geologia Nucleare, Pisa (1965).] to specific conditions in temperate regions seems necessary.     

Nachruf Prof. Hübner

Abstract

Representative water samples were collected from different oases in the western desert of Egypt to examine characteristics of Egyptian groundwater. Chemical data recognized two basic groundwater types; alkali bicarbonate and alkali chloride, where sodium has the highest concentration. For each region the median SD, δ¹⁸ 0 and ionic strength of water calculated from their chemical analyses are recorded and plotted.

Generally, the results of isotopic content measurements of the groundwaters from the different oases in the western desert indicate the fossile origin of these waters. The values of δD and δ¹⁸ 0 of the western desert oases' waters are characteristic of old paleowaters from the Nubian sand aquifer. Modern sparse rainfall data suggest that any precipitation will exhibit moderate to large positive isotopic content enrichments and cannot be a source for these waters. They have been in no connection with the Nile water, moreover the change in isotopic composition is due to evaporation which is now ineffective at deeper levels.     

Isotopic Assessment of Sources and Processes Affecting Sulfate and Nitrate in Surface Water and Groundwater of Luxembourg

Abstract

Surface water and deep and shallow groundwater samples were taken from selected parts of the Grand-Duchy of Luxembourg to determine the isotopic composition of nitrate and sulfate, in order to identify sources and/or processes affecting these solutes. Deep groundwater had sulfate concentrations between 20 and 40mg/L, δ³⁴S_sulfate values between ?3.0 and ?20.0‰, and δ¹⁸O_sulfate values between +1.5 and +5.0‰ nitrate was characterized by concentrations varying between <0.5 and 10mg/L, δ¹⁵N_nitrate values of ～?0.5‰, and δ¹⁸O_nitrate values ～+3.0‰. In the shallow groundwater, sulfate concentrations ranged from 25 to 30mg/L, δ³⁴S_sulfate values from ?20.0 to +4.5‰, and δ¹⁸O_sulfate values from ～+0.5 to +4.5‰ nitrate concentrations varied between ～10 and 75mg/L, δ¹⁵N_nitrate values between +2.5 and +10.0‰, and δ¹⁸O_nitrate values between +1.0 and +3.0‰. In surface water, sulfate concentrations ranged from 10 to 210mg/L, δ³⁴S_sulfate values varied between ?9.3 and +10.9‰, and δ¹⁸O_sulfate values between +3.0 and +10.7‰ were observed. Nitrate concentrations ranged from 10 to 40mg/L, δ¹⁵N_nitrate values from +6.5 to +12.0‰, and δ¹⁸O_nitrate values from ?0.4 to +4.0‰. Based on these data, three sulfate sources were identified controlling the riverine sulfate load. These are soil sulfate, dissolution of evaporites, and oxidation of reduced S minerals in the bedrock. Both groundwater types were predominantly influenced by sulfate from the two latter lithogenic S sources. The deep groundwater and a couple shallow groundwater samples had nitrate derived mainly from soil nitrification. All other sampling sites were influenced by nitrate originating from sewage and/or manure. A decrease in nitrate concentration observed along one of the rivers was attributed to denitrification. It appears that sulfate within Luxembourg's aquatic ecosystem is mainly of lithogenic origin, whereas nitrate is often derived from anthropogenic activities.     

Isotope and Trace Gas Analyses as Tools to Assess Water Protection Zones in a Rural Area

Abstract

An example is presented for the application of groundwater age dating by tritium and chlorofluorocarbon (CFC) measurements to assess water protection zones. The investigation area is located in a rural area close to Osnabrück (Lower Saxony, Germany). Samples from 13 drinking water supply wells were collected in November 1995.

By using an exponential model, groundwater residence times were calculated for the wells. The tritium and CFC data showed comparable residence times with slightly higher values derived from the CFCs (especially F113). Most of the wells showed residence times around or below 10 years indicating a rather high vulnerability with respect to anthropogenic contaminations.     

Impact of Measurement Uncertainty in Chemical Quantities on Environmental Prognosis by Geochemical Transport Modelling∗

Abstract

In Germany, geochemical modelling takes a strong position in two aspects of broader public interest. The first aspect is the safety assessment of a nuclear waste repository, the second is remediation of uranium mining areas. In both aspects, the application of geochemical modelling is stipulated by authorities. This situation results from the possibility to model highly complex situations by computers. The increase in computing power experienced in recent times now offers techniques to assess the sensitivity of modelling results to uncertain input data both in the thermodynamic data base and the site-specific field data. Both aspects are investigated by using Monte Carlo methods in combination with non-parametric statistics. A probabilistic geochemical modelling of uranium mill tailings leaching is demonstrated by application of TReaC modelling code using a simplified site model.     

Isotopic characteristics of meteoric waters in the Belgrade region

Abstract

The stable isotope composition of hydrogen (δ²H) and oxygen (δ¹⁸O) in monthly precipitation and river water (Sava River and Danube) samples in the Belgrade area gathered between 1992 and 2005 are determined. The local meteoric water line δ²H=7.8 (±0.2) δ¹⁸O+7.3(±1.6) (r ²=0.98, n=60, σ=0.52) for the whole period of observation is close to the global meteoric water line. The amount-weighted mean δ²H and δ¹⁸O values of precipitation were?65±27 ‰ and?9.4±3.4 ‰, respectively. Good correlation between δ¹⁸O values (r>rsim0.67) and ambient temperature and relative humidity was obtained. Stream-water data ranged from?94 to?60 ‰ for δ²H and from?11.0 to ～5.7 ‰ for δ¹⁸O with highly statistically significant difference (p>0.01) between the Sava River and the Danube. In addition, the isotopic compositions of local precipitation and adjacent river water at monitoring sites were compared. Obtained data will give an opportunity to improve the knowledge of mixing stream water and local groundwater, and assessment of potential groundwater risks and pressures in the Belgrade basin.     

Deuterium as Natural Tracer in Groundwater from Neighbouring Area of Danube Delta Biosphere Reserve

Abstract

Measurements of deuterium content of the groundwater from neighbouring area of Danube Delta Biosphere Reserve show that the waters are meteoric in origin, but at the same time the results showed that the water for three sampling points could not originate from local groundwater and have their recharge area at high altitude and a considerable distance.

According to the δD values the following categories of waters were delineated:

• (1) waters that belong to an confined aquifer in limestone and have their recharge in high altitude region, higher than 1000m (δD < -80‰)

  (2) waters tributary to the Danube river that have a small variability in time of δD values (δD > - 75‰)
  (3) local infiltration waters, situated in the West of the investigated area towards the continental platform of the Dobroudja, with high variability in time of δD values, due to seasonal effect (δD > - 70‰)
  (4) waters originated in mixing processes between the waters with different isotopic content. The one endmember is heavier isotopic water that belongs to local recharged waters (local infiltration waters and waters tributary to Danube river) and the other endmember is the isotopically light water.

     

Tritium Content and Salinity of Some Groundwaters in Greater Cairo Water Supply Stations

Abstract

Groundwaters from some wells, used for potable water supply from three drinking water stations at Greater Cairo in El-Ameria, El-Harem and Joli Ville, were sampled for tritium measurement. The wells with low tritium content are very suitable for drinking purpose due to the high residence time indicating that the groundwater was away from surface contaminations for a longer time. The pumping of the production wells should be restricted to deep wells of low salinity for drinking purpose. General recommendations are given for the proper approach for exploiting groundwater as a useful and cheap source for drinking water in Greater Cairo.     

Saisonale Variation von Deuterium und Sauerstoff-18 in Luftfeuchte und Niederschlag über Antarktika

Abstract

D and ¹⁸O distributions were investigated in Antarctic precipitation (falling snow) and in water vapour to study their dependance on season and sampling site. Long-term sampling at the former German Georg Forster Station during 1978–93 and at the Japanese Syowa Station during 1994–97 allow conclusions about the present seasonal isotopic variations in the water inflow to Antarctica. The δD and δ¹⁸O values of precipitation at these East Antarctic coastal stations were compared with corresponding data from the West Antarctic Georg von Neumayer and Halley stations. The monthly means of these long-term data sets show typical hysteresis-like seasonal patterns of isotopic composition. Significant time lags exist regarding station temperatures, while water vapour δD values do not show such hysteresis patterns. Here, half-yearly and even quarter-yearly time components were found by Fourier analysis. Attempts were made to describe the variation in δD and δ¹⁸O values of water vapour and precipitation as well as in the resulting deuterium excess by the mixed cloud isotopic model (MCIM) of Ciais and Jouzel.     

There is no Temperature Dependence of Net Biochemical Fractionation of Hydrogen and Oxygen Isotopes in Tree-Ring Cellulose

Abstract

The isotopic composition of tree-ring cellulose was obtained over a two-year period from small diameter, riparian zone trees along an elevational transect in Big Cottonwood Canyon, Utah, USA to test for a possible temperature dependence of net biological fractionation during cellulose synthesis. The isotope ratios of stream water varied by only 3.6‰ and 0.2‰ in δD and δ¹⁸O, respectively, over an elevation change of 810m. The similarity in stream water and macroenvironment over the short (13km) transect produced nearly constant stem and leaf water δD and δ¹⁸O values. In addition, what few seasonal variations observed in the isotopic composition of source water and atmospheric water vapor or in leaf water evaporative enrichment were experienced equally by all sites along the elevational transect. The temperature at each site along the transect spanned a range of ≥ 5°C as calculated using the adiabatic lapse rate. Since the δD and δ¹⁸O values of stem and leaf water varied little for these trees over this elevation/ temperature transect, any differences in tree-ring cellulose δD and δ¹⁸O values should have been associated with temperature effects on net biological fractionation. However, the slopes of the regressions of elevation versus the δD and δ¹⁸O values of tree-ring cellulose were not significantly different from zero indicating little or no temperature dependence of net biological fractionation. Therefore, cross-site climatic reconstruction studies using the isotope ratios of cellulose need not be concerned that temperatures during the growing season have influenced results.     

Stable isotopic and geochemical variability within shallow groundwater beneath a hardwood hammock and surface water in an adjoining slough (Everglades National Park,Florida, USA)

Data from a 10-month monitoring study during 2007 in the Everglades ecosystem provide insight into the variation of δ¹⁸O, δD, and ion chemistry in surface water and shallow groundwater. Surface waters are sensitive to dilution from rainfall and input from external sources. Shallow groundwater, on the other hand, remains geochemically stable during the year. Surface water input from canals derived from draining agricultural areas to the north and east of the Everglades is evident in the ion data. δ¹⁸O and δD values in shallow groundwater remain near the mean of?2.4 and?12 ‰, respectively. ¹⁸O and D values are enriched in surface water compared with shallow groundwater and fluctuate in sync with those measured in rainfall. The local meteoric water line (LMWL) for precipitation is in close agreement with the global meteoric water line; however, the local evaporation line (LEL) for surface water and shallow groundwater is δ D=5.6 δ¹⁸O+1.5, a sign that these waters have experienced evaporation. The intercept of the LMWL and LEL indicates that the primary recharge to the Everglades is tropical cyclones or fronts. δ deuterium to δ¹⁸O excess (D_ex values) generally reveal two moisture sources for precipitation, a maritime source during the fall and winter (D _ex>10 ‰) and a continental-influenced source (D _ex<10 ‰) in the spring and summer.     

Influence of Nitrogen,Water and Competition on Carbon Isotope Ratios (δ13C) in a CAM Plant (Crassula argentea)

Abstract

Leaf carbon isotope ratios (δ¹³C), an indicator of long-term intercellular carbon dioxide concentration, and also stem and root carbon isotope ratios were measured on the obligate CAM species Crassula argentea cultivated in pure and mixed cultures with the succulent C₃ Peperomia obtusifolia in open-air conditions under two different levels of nitrogen and water supply.

As expected, a diminished water supply and a relatively dry and hot summer climate cause a shift of δ¹³C values to a less strong ¹³C discrimination (less negative δ¹³C values). A diminished nitrogen supply causes a shift of the δ¹³C values in direction of a higher ¹³C discrimination (more negative δ¹³C values), particularly in the leaves. Competition causes also an increased ¹³C discrimination, especially valid for shoot axes.

The shift of ¹³C/¹²C isotope ratios in case of nitrogen deficiency is discussed to be a result of a decreased PEPCase activity in the night.     

Use of Isotope Analysis in Solving Environmental Problems in Power Engineering

Abstract

During hydraulic dumping of ashes at a sludge bed of the power plant at Mělnik (north of Prague), new springs originated which wetted houses and properties at the small village of Podvlci. The sludge bed as well as the village lie at the southwestern margin of the alluvial plain of the Labe (Elbe) River at the foot of a slope built of Cretaceous sedimentary rocks. By analyzing the concentrations of radiocarbon and tritium, it was possible to determine the origin of the water and the ratio of the modern and original groundwater in the new springs in the surroundings of the sludge bed. To substitute the present dump the operation of which should be stopped, establishing of a new one has been proposed within the alluvial plain. By means of stable isotopes and radionuclides, the relations between the groundwater in the Quaternary sediments and in the underlying Middle Turonian confined aquifer were studied, because changes in the hydrogeological regime have to be expected due to the operation of the proposed new sludge bed.     

Experimental study of uranium isotope fractionation of rock material from two aquifers

This paper presents results of a study carried out in order to estimate the uranium isotope fractionation ²³⁴U/²³⁸U in groundwater from laboratory experiments. Matrix rock from borcholes in a Triassic sandstone aquifer and a Pleistocene sand aquifer was leached with 1 N HCl, 0.1 N HCl and deionized water.

Additionally, the uranium isotope composition of the bulk rock (index “R”) and several groundwater samples of corresponding horizons were analysed. The results indicate the relation between the portion of leached uranium (index “L”) and the observed activity ratio ²³⁴U/²³⁸U (AU)

.

If this relation can be confirmed by further investigations new possibilities of using uranium isotopes in hydrogeology would be made available

Die Arbeit stellt Ergebnisse einer Studie vor, die zur Abschützung der Uranium-Isotopenfraktionierung ²³⁴U/²³⁸U im Grundwasser aus Laborexperimenten durchgeführt wurde. Matrixgestein von Bohrlöchern in einem Triassischen Sandstein-Grundwasserleiter und einem aus pleislozänen Sanden bestehenden Grundwasserleiter wurde mit 1 N HCl, 0,1 HCl und entionisiertem Wasser gelaugt. Auβerdem wurden die Uranium-Isotopenzusammensetzung des Gesteins (Index “R”) und einige Grundwasserproben zugehöriger Horizonte analysiert. Die Ergebnisse zeigen cine Beziehung zwischen dem Anteil des gelaugten Uraniums (Index “L”) und dem Aktivitätsverhältnis ²³⁴U/²³⁸U (AU)

.

Wenn diese Relation durch weitere Untersuchungen bestäligt werden kann, eröffnen sich neue Möglichtkeiten für die Nutzung der Uraniumisotope in der Hydrogeologie.     

Pleistocene age paleo-groundwater inferred from water-stable isotope values in the central part of the Baltic Artesian Basin

A new data set of δ²H and δ¹⁸O in the groundwater from the central part of the Baltic Artesian Basin is presented. The hydrogeological section is subdivided into stagnation, slow exchange and active exchange zones. Na–Ca–Cl brine found at the deepest part – the stagnation zone – is characterized by δ¹⁸O values above ?5?‰ and δ²H values approaching ?40?‰ with respect to Vienna Standard Mean Ocean Water. The slow exchange zone where waters of mostly intermediate salinity reside is characterized by δ¹⁸O values around ?11.7?‰ and δ²H values around ?85.3?‰. Mean δ¹⁸O and δ²H values of the fresh groundwater in the active water exchange zone are ?11.1 and ?79.9?‰, respectively. Characteristically, the groundwater in the active and slow exchange zone is isotopically more depleted compared with the precipitation values observed, and the depletion increases with depth down to the level where strongly enriched brines are encountered.     

The Suitability and Usage of 18O and Chloride as Natural Tracers for Bank Filtrate at the Middle River Elbe

Abstract

Flow times and infiltration behaviour are very important for water extraction from riverbank filtration. Both the chloride content and the isotopic composition of oxygen (δ¹⁸O) were found to be suitable indicators for the conditions encountered in the middle course of the River Elbe near Torgau. The ranges for Elbe water were measured to be 20–43 mg Cl/l (1995-97) and -11 to -8.5‰ δ¹⁸O (1993-97). Both methods permitted flow-time spectra at two adjacent sampling profiles incorporating river and production wells to be obtained, indicating the preferred flow paths and the vertical extension of the riverbank filtrate plume in the aquifer. However, since the differences between the mean values for river water and regional groundwater were too small the percentage of river water abstracted from production wells could not be calculated.     

Estimation of microbial methane generation and oxidation rates in the municipal solid waste landfill of Kaluga city,Russia

Using a theoretical model and mass isotopic balance, biogas (methane and CO₂) released from buried products at their microbial degradation was analysed in the landfill of municipal and non-toxic industrial solid organic waste near Kaluga city, Russia. The landfill contains about 1.34×10⁶ tons of waste buried using a ‘sandwich technique’ (successive application of sand–clay and waste layers). The δ¹³C values of biogenic methane with respect to CO₂ were?56.8 (±2.5) ‰, whereas the δ¹³C of CO₂ peaked at+9.12‰ (+1.4±2.3‰ on average), reflecting a virtual fractionation of carbon isotopes in the course of bacterial CO₂ reduction at the landfill body. After passing through the aerated soil layers, methane was partially oxidised and characterised by δ¹³C in the range of?50.6 to?38.2‰, evidencing enrichment in ¹³C, while the released carbon dioxide had δ¹³C of?23.3 to?4.04‰, respectively. On the mass isotopic balance for the δ¹³C values, the methane production in the landfill anaerobic zone and the methane emitted through the aerated landfill surface to the atmosphere, the portion of methane oxidised by methanotrophic bacteria was calculated to be from 10 to 40% (averaged about 25%). According to the theoretical estimation and field measurements, the annual rate of methane production in the landfill reached about 2.9(±1.4)×10⁹ g C CH₄ yr^?1 or 5.3(±2.6)×10⁶ m³ CH₄ yr^?1. The average rates of methane production in the landfill and methane emission from landfill to the atmosphere are estimated as about 53 (±26) g C CH₄ m^?2 d^?1 (or 4 (±2) mol CH₄ m^?2 d^?1) and 33 (±12) g C CH₄ m^?2 d^?1 (or 2.7 (±1) mol CH₄ m^?2 d^?1), respectively. The calculated part of methane consumed by methanotrophic bacteria in the aerated part of the landfill was 13(±7) g C CH₄ m^?2 d^?1 (or 1.1(±0.6) mol CH₄ m^?2 d^?1) on average.     

Groundwater of the Crimean peninsula: a first systematic study using stable isotopes

ABSTRACT

Karst springs in the Main Range of the Crimean Mountains and the Crimean Piedmont show a restricted range of values (δ¹⁸O?=?–10.5 to –8.0 ‰, δ²H?=?–72 to –58 ‰), somewhat more negative than the weighted mean of meteoric precipitation. This suggests preferential recharge at higher elevations during winter months. Groundwater tapped by boreholes splits in three groups. A first group has isotopic properties similar to those of the springs. The second group shows significantly lower values (δ¹⁸O?=?–13.3 to –12.0 ‰, δ²H?=?–95 to –82 ‰), suggesting recharge during colder Pleistocene times. The third group has high isotope values (δ¹⁸O?=?–2.5 to +1.0 ‰, δ²H?=?–24 to –22 ‰); the data points are shifted to the right of the Local Meteoric Water Line, suggesting water–rock exchange processes in the aquifer. These boreholes are located in the Crimean Plains and discharge mineralized (ca. 25 g L^?1) thermal (65°C) water from a depth of 1600–1800 m. Groundwater associated with mud volcanoes on the Kerch peninsula have distinct isotope characteristics (δ¹⁸O?=?–1.6 to +9.4 ‰, δ²H?=?–30 to –18 ‰). Restricted δ²H variability along with variable and high δ¹⁸O values suggest water–rock interactions at temperatures exceeding 95 °C.