Evaluation of the sulfate dynamics in groundwater by means of environmental isotopes.

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 834S, delta18O-H2O, deltaD, tritium, and 85K5r. delta34S values of the groundwater sulfate vary between -19...+ 37 per thousand CDT. No simple correlation exists between sulfate concentrations and delta34S. 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 delta18O and 8D, 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.

Using environmental isotopes 2H and 18O for identification of infiltration processes in floodplain ecosystems of the River Elbe.

We examined a floodplain area in the middle section of the river Elbe Valley with regard to hydrogeological and hydrological processes using isotopic methods. Over two years, river water and groundwater have been analysed for temporal and spatial chemical and isotopic (delta2H and delta18O) changes. By these methods we assessed the flow dynamics of the river-groundwater infiltration system. At low and mean river stages there is a general hydraulic gradient from the higher areas at the margin of the valley towards the floodplain. During floods river water infiltrates into the adjacent aquifer not primarily through the river banks but first through surface water inflow from north to south, via depressions and gullies from the back of the floodplain. The early stage of river water infiltration is characterized by a sharp decrease in conductivity and in concentrations of SO4(2-) and Cl- in the hydraulically connected shallow aquifer. delta2H and delta18O values show a similar tendency. We observed a significant minimum in stable isotope ratios during the flood in March 1999. Using a simple mixing equation it was calculated that the groundwater in the upper, shallow aquifer consists of around 70% river water in the transition zone (well 13) during flooding.

Calorimetric validation of 13C bicarbonate and doubly labeled water method for determining the energy expenditure in goats.

The purpose of the present study was to validate the 13C bicarbonate method (13C-M) and the doubly labeled water method (DLWM) for the estimation of the CO2 production R(CO2) in goats as a ruminant model. Indirect calorimetry was chosen as the reference method. Studies were carried out in 2 male African dwarf goats at 3 different developing stages (age: 5, 10, and 14 months, body mass: 14.6, 20.3, and 21.7 kg). Animals were fed a balanced feed 14 days before and during the studies. The isotope tracers (4 mg/kg NaH13CO3, 120 mg/kg 2H2O, and 75 mg/kg H218O; 99 AT.-%) were simultaneously given as a single pulse injection into the jugular vein. Thereafter, the animals were kept for 8 days in two respiration chambers (volume of chamber: 2.85 m3, air flow rate: 25 1/min) for the estimation of CO2 production and O2 consumption. For the determination of R(CO2) using the 13C-M samples of exhaled breath were drawn from the respiration chambers. The 13C enrichment and CO2 concentration of breath samples were measured by means of an infrared isotope analyzer. In order to determine R(CO2) by means of the DLWM, blood serum was used. The 2H and 18O enrichments were measured by an isotope ratio mass spectrometer. Urine samples were collected over 24 h to quantify renal water losses. The R(CO2) was calculated by means of the 13C-M using the area under the 13C enrichment-time curve. The determination of R(CO2) by means of the DLWM was based on the slopes of the 2H and 18O disappearance curves and the body water pool obtained from the zero time intercept of the isotope curves. The values of R(CO2) resulting from the 13C-M were found to be comparable with those from the calorimetric measurement. Smaller (not statistically significant) values of R(CO2)--92% from 13C-M and 87% from DLWM--compared to the indirect calorimetry could indicate the incorporation of 13C and 2H into metabolites other than CO2 and H2O, respectively. The body water contents calculated from the zero time intercepts of the 2H and 18O disappearance curves amounted to 66% and 63%, respectively. The body water content was found to be not related to the age of animals. The renal water loss was calculated to be 35% of the total water loss (0.76 l/d.

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

Abstract D and (18)O 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 δ(18)O 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 δ(18)O 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.

Methodical studies for d/h-isotope analysis - a new technique for the direct coupling of sample preparation to an irms.

Abstract A new technique for the sample preparation and direct coupling to an Isotope Ratio Mass Spectrometer (IRMS) for the D/H-determination is described. 1 µl size samples of water are injected and reduced with chromium metal in a novel reaction furnace. The hydrogen gas flows directly into the IRMS and is analysed (standard/sample comparison). The reproducibility is about 1 %. The accuracy of the technique was proven by means of the IAEA-standard waters V-SMOW, GISP, SLAP.

Mineral- und heilwässer in sachsen - eine isotopenanalytische charakterisierung.

Abstract The groundwaters studied and labelled as mineral water were "natural mineral waters" for bottled waters and "natural curative waters" for heal therapeutical applications. They were characterized either by a specific mineralization or their suitability for balneology. To reveal the actual hydrological situation isotope investigations using (2)H, (18)O, (3)H, (12)C and (14)C (DIC) and (34)S (sulphate) were included in a study describing samples of 24 mineral water deposits in Saxonia. The water was classified into 4 hydrochemical types of genesis. Due to different hydrogeological and hydrochemical situations widely scattered isotope ratios were measured. Most of the investigated mineral waters are containing at least parts of younger waters (with residence times less than about 40 years). Correlations between chemical composition and the tritium content could be observed within different springs from the areas Bad Brambach, Bad Elster and Burkhardswalde. Strong variations in δ(34)S were found in samples with low sulphate content, showing different sulphur sources, as well as microbiological reactions. On the other hand mineral waters from Bad Brambach and Bad Elster show nearly the same δ(34)S value of about 6‰ CDT despite beeing of a different chemical type. The δ(13)C values between -22 and -2.2y PDB are related to different sources of CO(2).