13C discriminations of Pinus sylvestris vs. Pinus ponderosa at a dry site in Brandenburg (eastern Germany): 100-year growth comparison

The carbon isotope composition (δ¹³C, ‰) and discrimination (Δ, ‰) of old grown North American Pinus ponderosa Dougl. Ex P. et C. Laws. and European Pinus sylvestris L. were determined using trees grown under almost identical growing conditions in a mixed stand in Bralitz, Northeast Germany. Single-tree δ¹³C analyses of tree-ring cellulose of both species were carried out at a yearly resolution for the period 1901–2001 and the results compared with growth (basal area increment). Annual mean δ¹³C values for P. ponderosa ranged from?21.6 ‰ to?25.2 ‰ and for P. sylvestris from?21.4 ‰ to?24.4 ‰. Accordingly, ¹³C discrimination (Δ) showed higher values for P. ponderosa throughout the investigation period. Five characteristic periods of Δ were identified for both the tree species, reflecting positive and negative influences of environmental factors. Good growing conditions such as after-thinning events had a positive effect on Δ, reflecting higher values, while poor conditions like aridity and air pollution had a negative influence, reflecting lower values. The dynamics of Δ were likewise reflected in the growth (basal area increment, BAI). Higher ¹³C discrimination values of P. ponderosa led to higher BAIs of P. ponderosa in comparison with P. sylvestris. Correlation function analyses confirmed that P. sylvestris was more dependent on precipitation than P. ponderosa, which showed a closer relationship with temperature. The results confirm that under predominantly dry growing conditions, P. ponderosa showed better growth performance than P. sylvestris, indicating better common intrinsic water-use efficiency and, therefore, higher rates of net photosynthesis at a given transpiration. In view of the prospect of climate change, the results are very significant for assessing both trees’ physiological properties and, hence, their potential for coping with future growing conditions.     

Characteristics of suspended matter in the River Sava watershed, Slovenia

A combination of C/N ratios, delta(13)C and delta(15)N values in suspended matter was used to examine the seasonal (late summer 2004 and spring 2005) relationship with hydrological characteristics of the River Sava watershed in Slovenia. The values of C/N ratios range from 1.2 to 19.1, delta(13)C values range from-29.2 to-23.0 per thousand and delta(15)N values from 0.5 to 16.7 per thousand and indicate that the samples are a mixture of two end members: modern soils and plant litter. A simple mixing model was used to indicate that soil organic carbon prevails over plant litter and contributes more than 50% of suspended material. The calculated annual particulate organic carbon flux is estimated as 5.2x10(10) g C/year, the annual particulate nitrogen flux 8.5x10(9) g N/year and the total suspended solid flux is estimated to be 1.3x10(12) g/year. Anthropogenic impact was detected only in a tributary stream of the River Sava, which is located in an agriculture-industrial area and is reflected in higher delta(15)N values in suspended matter and high nitrate concentrations in the late summer season.     

Distribution of stable isotopes in surface water along the Danube River in Serbia

Stable hydrogen and oxygen isotopes were analysed in water samples from the River Danube and its tributaries during a longitudinal survey performed in August 2005 on Serbian territory. Danube river water data ranged from-80 per thousand to-66 per thousand for delta2H, and from-11.2 per thousand to-9.3 per thousand for delta18O with delta values increasing downstream. The isotopic signatures of the adjacent tributaries (the Tisza, the Sava and the Velika Morava) sampled at the locations close to their confluence with the Danube (Titel, Ostruznica and Ljubicevski most, respectively) just about the time of the campaign were enriched (-67 per thousand and-63 per thousand for delta2H, and-9.3 per thousand and-8.9 per thousand for delta18O) with respect to the Danube water because of their catchment effects. Hydrogen and oxygen stable isotope values were used in combination with measured physico-chemical and biological parameters to trace hydrological and transport processes in these river systems. The mixing relationships between the Danube main stream and its tributaries were estimated using the mass balance for isotopic composition and electrical conductivity as conservative parameters. Evidence of an incomplete mixing process at the Centa location, 8 km below the confluence of the Tisza river, with its participation of 88% was shown by its oxygen-18 content. The correlations between river water isotope composition and physico-chemical and biological parameters are discussed.     

Potential for assessing long-term dynamics in soil nitrogen availability from variations in delta15N of tree rings

Numerous researchers have used the isotopic signatures of C, H, and O in tree rings to provide a long-term record of changes in the physiological status, climate, or water-source use of trees. The frequently limiting element N is also found in tree rings, and variation in its isotopic signature may provide insight into long-term changes in soil N availability of a site. However, research has suggested that N is readily translocated among tree ring of different years; such infidelity between the isotopic compositions of the N taken up from the soil and the N contained in the ring of that growth year would obscure the long-term N isotopic record. We used a 15-year 15N-tracer study to assess the degree of N translocation among tree rings in ponderosa pine (Pinus ponderosa) trees growing in a young, mixed-conifer plantation. We also measured delta13C and delta15N values in unlabeled trees to assess the degree of their covariance in wood tissue, and to explore the potential for a biological linkage between them. We found that the maximum delta15N values in rings from the labeled trees occurred in the ring formed one-year after the 15N was applied to the roots. The delta15N value of rings from labeled trees declined exponentially and bidirectionally from this maximum peak, toward younger and older rings. The unlabeled trees showed considerable interannual variation in the delta15N values of their rings (up to 3 and 5 per thousand), but these values correlated poorly between trees over time and differed by as much as 6 per thousand. Removal of extractives from the wood reduced their delta15N value, but the change was fairly small and consistent among unlabeled trees. The delta13C and delta15N values of tree rings were correlated over time in only one of the unlabeled trees. Across all trees, both delta13C values of tree rings and annual stem wood production were well correlated with annual precipitation, suggesting that soil water balance is an important environmental factor controlling both net C gain and transpirational water loss at this site. Our results suggest that interannual translocation of N among tree rings is substantial, but may be predictable enough to remove this source of variation from the tree-ring record, potentially allowing the assessment of long-term changes in soil N availability of a site.     

Isotopic characteristics of meteoric waters in the Belgrade region

The stable isotope composition of hydrogen (delta(2)H) and oxygen (delta(18)O) 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 delta(2)H=7.8 (+/-0.2) delta(18)O+7.3(+/-1.6) (r(2)=0.98, n=60, sigma=0.52) for the whole period of observation is close to the global meteoric water line. The amount-weighted mean delta(2)H and delta(18)O values of precipitation were-65+/-27 per thousand and-9.4+/-3.4 per thousand, respectively. Good correlation between delta(18)O values (r approximately >0.67) and ambient temperature and relative humidity was obtained. Stream-water data ranged from-94 to-60 per thousand for delta(2)H and from-11.0 to approximately 5.7 per thousand for delta(18)O 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.     

Stable isotope geochemistry of calcrete nodules and septarian concretions in a Quaternary 'red clay' paleovertisol from Hungary

Calcrete nodules and concretions in unusually large amounts are embedded in the Quaternary clay-rich (Vertisol-type) 'red clay' soil-sedimentary complex at the pediment of the Mátra Mountains (Hungary). Stable isotope signatures were studied in nodules and septarian concretions, uncommon due to their several millimeter sized calcite crystals filling voids and fractures, to reveal their origin. The isotope composition of calcrete covers a wide range: delta18O=-5.9 to-10.4 per thousand and delta13C=-8.9 to-12.3 per thousand (vs. V-PDB). Isotope compositions support pedogenic (sensu stricto) and/or shallow groundwater origin for the calcrete nodules and concretions, the role of 'evolved' (isotopically modified) groundwaters in the formation of secondary carbonate was possibly subordinate. Late-stage, large, Mn-rich euhedral calcite crystals in concretions have the lowest delta13C values, which are interpreted as a result of larger contribution of isotopically light organic carbon due to decomposition of organic matter under reducing conditions. Precipitation of late calcite crystals in concretions occurred in early diagenetic environment after shallow burial of the 'red clay' paleovertisol.     

Millimeter scale variations in the isotopic composition of vein sulphide minerals in the Kupferschiefer deposits, Lubin area, SW Poland

A slice of black shale rock cut by various metal sulphide veins of different generations from the Kupferschiefer deposits of Lubin, Poland was subjected to bombardment in a Laser Microprobe Combustion Reactor to produce SO2 for S-isotope analyses. The delta34S values ranged from-22 to-29 per thousand consistent with previous findings using conventional IRMS and attributable to primary generation of H2S by bacterial sulphate reduction. Systematic trends in delta34S values of a few per mil over distances of the order of mm attest to low temperatures of mineralization with accompanying change in the isotope composition of the fluids due to kinetic or equilibrium isotope fractionation.     

Feeding and growth of apple snail Pomacea lineata in the Pantanal wetland,Brazil--a stable isotope approach

Apple snails Pomacea lineata (SPIX 1827) are widespread in the tropical regions of Brazil as well as in the Pantanal wetland of Mato Grosso in the western part of the country. They have a key position in the Pantanal food web and serve as food for many animals e.g. fishes, birds, and caimans. However, little is known about their feeding preferences and growth rates. Stable isotopes have been used successfully on numerous studies as food source indicator. Therefore, the delta15N and delta13C values of snails from 0.45 to 3.03 cm in length, which were collected in the rainy season from March through May, were analyzed. Snails signatures revealed ambiguous evidence for food preferences. Delta15N and delta13C values ranged between -2.8 and 12.4 per thousand and between -24.2 and -16.4, per thousand respectively. This range of values mirrors the highly variable isotope values of possible food sources comprising C3 and C4 macrophytes. To test whether all common food sources were similarly assimilated, feeding experiments with different diets were conducted. Snail eggs were reared in tanks and offered different but single plants. Snails fed different diets and delta13C values of the food were reflected in the animal tissue. Growth varied considerably in experiments with different diets indicating the preference for certain food sources. Also, the fractionation of nitrogen isotopes between food and animal varied from 0.1 to 17.0 per thousand. The results are explained by different feeding habits, and it is supposed that animals fed either on the plant itself or on bacteria mats growing in the tanks. In an additional experiment juvenile snails were offered one single food with a distinctive C4 grass signature. These snails did not grow detectably, but nevertheless isotope signatures approached to values of the diet.     

Isotopic composition of sulphates from meteoric precipitation as an indicator of pollutant origin in Wrocław (SW Poland)

This paper describes the results of isotopic analyses of (i) hydrogen and oxygen in water (delta DH2O and delta18OH2O ) and (ii) sulphur and oxygen in sulphates (delta34Ssulphate and delta18Osulphate) from atmospheric precipitation collected within a one-year period between 25 May 2004 and 25 May 2005 in Wroc?aw (SW Poland). The resulting equation of Local Meteoric Water Line for Wroc?aw is delta D=6.373xdelta18O-0.047, (r2=0.97, n=32). The delta34Ssulphate varies from 1.1 to 4.2 per thousand (with an average of 2.5 per thousand), delta18Osulphate varies from 9.0 to 16.7 per thousand (with an average of 13.8 per thousand) and delta18OH2O varies from-0.8 to-16.3 per thousand (with an average of-8.2 per thousand). The above results indicate two main sources of sulphates in Wroc?aw precipitation: (i) low-temperature secondary sulphates forming in situ in Wroc?aw from the atmospheric SO2 as well as precipitation water (heterogeneous and homogeneous pathways oxidation) and (ii) high-temperature primary sulphates forming in rapid high-temperature hydratation of SO3- in an immediate proximity of industrial chimneys. We hypothesise that the secondary low-temperature type of sulphates is probably formed from the local sulphur and oxygen reservoirs, whereas the primary high-temperature type is allochthonous and it is probably transported from industrial areas located outside of Wroc?aw.     

Determination of delta13 CV-PDB and delta15NAIR values of cocaine from a big seizure in Germany by stable isotope ratio mass spectrometry

In this study, delta(13)C(V- PDB) and delta(15)N(AIR) values of 132 cocaine samples from a big seizure in Germany in 2002 were determined using elemental analyser isotope ratio mass spectrometry. The 1.2 tons of cocaine were packed in 1 kg packages and the cocaine bricks inside these packages showed certain logos. Twenty different logos could be identified. Results show a large variability among some samples, for delta(15)N(AIR) values ranging from-17 to -2 per thousand. Furthermore, the possibility of linking samples with the same logo was checked. The results show that, in general, there is no relationship between the determined isotope ratio and a certain logo.     

Isotope variations in white-tailed kites from various habitats in California: possible limitations in assessing prey utilization and population dynamics

White-tailed kite (Elanus leucurus) populations in the 1930s were close to extirpation in the United States. But by the 1940s, an upward trend towards recovery was apparent and continued to their current stable population levels. These dramatic fluctuations in kite numbers may have been related to changes in rodent prey populations due to the conversion of native habitats to agriculture. To address this question, we evaluated the use of stable isotope analysis in determining if a shift in diet could be isotopically differentiated in current and historic kite populations. We first compared delta13C, delta15N, and delta34S values from present-day kite flight feathers and prey fur samples from four locations in California. The total ranges of isotope values for kite and their rodent prey were similar within each site. Carbon isotope values ranged from -27.1 to -22.2 per thousand in Arcata, -26.1 to -16.9 per thousand in Davis, -27.0 to -15.0 per thousand in Cosumnes, and -28.2 to -11.6 per thousand in Santa Barbara. Nitrogen isotope values ranged from 3.2 to 15.7 per thousand in Arcata, 2.8 to 12.7 per thousand in Davis, 4.0 to 15.7 per thousand in Cosumnes, and 1.7 to 20.0 per thousand in Santa Barbara. Sulfur isotope values ranged from -7.8 to 12.4 per thousand in Arcata, -1.1 to 9.2 per thousand in Davis, 0.7 to 10.9 per thousand in Cosumnes, and -8.6 to 15.6 per thousand in Santa Barbara. Carbon, nitrogen, and sulfur isotope values at each site reflect typical trophic enrichments due to physiological processes. At each site, delta13C and delta15N values reflected the influence of a predominantly C3 or a mixed C3/C4 plant community. Sulfur isotope values reflect the influence of predominant marine or terrestrial sulfur sources at each site. However, variability in isotope values may limit the usefulness of such analyses for addressing prey utilization and population dynamics.     

Effects of natural environmental factors on delta13C of lichens

This preliminary study was designed to determine the extent to which the carbon isotope ratio in four species of lichens was influenced by such features as humidity, rainfall, radioactivity, and air quality. The sampling sites were selected to be at a great distance from any pollution. At the time of sampling, field data (temperature, relative humidity, average monthly precipitation, and radioactivity) were recorded. delta(13)C in whole lichen specimens were determined using standard mass spectrometric techniques with a standard deviation of+/-0.3 per thousand. We have found a weak but negative correlation between delta(13)C and relative humidity, and a positive correlation between delta(13)C and average monthly precipitation at the studied sites. The effects were minor, of the order of 1.5 per thousand for all the lichens. We have examined the correlation between (137)Cs activity concentration of the studied lichens and delta(13)C of these lichens, and we have suggested that fixation of radiocesium does not alter photosynthesis rate. There was a delta(13)C variation with the altitude gradient with less negative delta(13)C values at higher altitude. It is possible that this difference is caused by the ozone and occurred at the high elevations.     

Impact of water table depth on forest soil methane turnover in laboratory soil cores deduced from natural abundance and tracer 13C stable isotope experiments

We investigated turnover of methane (CH4) in soils from a poorly drained UK forest. In situ, this forest exhibited a negligible soil-atmosphere CH4 flux, whereas adjacent grassland plots were sources of CH4. We hypothesised that the forest plots exhibited reduced anaerobic CH4 production through water-table draw down. Consequently, we exposed soil cores from under oak to high and low water-table conditions in the laboratory. Methane fluxes increased significantly in the high water-table (1925+/-1702 mug CH4 m(-2) h(-1)) compared to the low one (-3.5+/-6.8 microg CH4 m(-2) h(-1)). Natural abundance delta13C values of CH4 showed a strong depletion in high water-table cores (-56.7+/-2.9 per thousand) compared to methane in ambient air (-46.0 per thousand) indicative of methanogenic processes. The delta13C values of CH4 from low water-table cores (delta13C-46.8+/-0.2 per thousand) was similar to ambient air and suggested little alteration of headspace CH4 by the soil microbial community. In order to assess the CH4 oxidizing activity of the two treatments conclusively, a 13CH4 spike was added to the cores and 13CO2 production was measured as the by-product of CH4 oxidation. 13CH4 oxidation rates were 57.5 (+/-12.7) and 0.5 (+/-0.1) microg CH4 m(-2) h(-1) for high and low water-tables, respectively. These data show that the lower water-table hydrology treatment impacted methanogenic processes without stimulating methanotrophy.     

A laser extraction/combustion technique for in situ delta(13)C analysis of organic and inorganic materials

A CO(2) laser extraction system is described for in situ delta(13)C analysis of organic and inorganic materials. Carbonaceous compounds volatilized by the laser are quantitatively converted to CO(2) gas by a combustion furnace mounted after the sample chamber. Gases produced by the laser and combustion processes are swept by helium carrier gas and separated by a packed gas chromatography column prior to their introduction to an isotope ratio monitoring mass spectrometer. A sample of lentil bean was analyzed at a spatial resolution of 200 μm and yielded delta(13)C values with precision of +/- 0.3 per thousand. The accuracy of delta(13)C measurements was better than +/- 0.5 per thousand from NBS 22 (mineral oil), USGS 24 (graphite), and IAEA CO-1 (calcium carbonate). Copyright 1999 John Wiley & Sons, Ltd.     

Estimating groundwater mixing and origin in an overexploited aquifer in Guanajuato, Mexico, using stable isotopes (strontium-87, carbon-13, deuterium and oxygen-18)

Stable Isotopes (strontium-87, deuterium and oxygen-18, carbon-13) have been used to reveal different sources of groundwater and mixing processes in the aquifer of the Silao-Romita Valley in the state of Guanajuato, Mexico. Calcite dissolution appeared to be the main process of strontium release leading to relatively equal (87)Sr/(86)Sr ratios of 0.7042-0.7062 throughout the study area which could be confirmed by samples of carbonate rocks having similar Sr ratios (0.7041-0.7073). delta(13)C values (-11.91- -6.87 per thousand VPDB) of groundwaters confirmed the solution of carbonates but indicated furthermore influences of soil-CO(2). Deuterium and (18)O contents showed a relatively narrow range of-80.1- -70.0 per thousand VSMOW and -10.2- -8.8 per thousand, VSMOW, respectively but are affected by evaporation and mixing processes. The use of delta(13)C together with (87)Sr/(86)Sr revealed three possible sources: (i) carbonate-controlled waters showing generally higher Sr-concentrations, (ii) fissure waters with low-strontium contents and (iii) infiltrating water which is characterized by low delta(13)C and (87)Sr/(86)Sr ratios. The third component is affected by evaporation processes taking place before and during infiltration which might be increased by extraction and reinfiltration (irrigation return flow).     

Spatial and seasonal variations in the stable C isotope composition of dissolved inorganic carbon and in physico-chemical water parameters in the Plitvice Lakes system

Plitvice Lakes waters were collected at 14 sampling points, including springs, tributaries and lakes, for the period 2002-2007. The results of the physical and chemical conditions of calcite precipitation as well as the δ(13)C values of dissolved inorganic carbon (DIC) were used to study the processes influencing calcite precipitation. Significant differences between spring, lake and stream waters as well as changes in the downstream direction were observed. The correlation between δ(13)C(DIC) values and physico-chemical conditions for calcite precipitation showed that calcite precipitates in lake waters which are oversaturated with respect to CaCO(3) (I (sat) values 4-10) and with δ(13)C(DIC) values between-11.5 and-8.5 ‰. In spring waters, the δ(13)C(DIC) values were more negative, from-14 to-12 ‰, and I (sat) values of 1-2 indicated that equilibrium conditions for calcite precipitation were not attained. The downstream increase in δ(13)C(DIC) correlated with the increase in the δ(13)C values of calcite in the lake sediments, suggesting that the freshwater calcite was mainly of autochthonous origin and precipitated within the water column in isotopic equilibrium with DIC.     

The fate of organic matter in a papyrus (Cyperus papyrus L.) dominated tropical wetland ecosystem in Nyanza Gulf (Lake Victoria, Kenya) inferred from delta13C and delta15N analysis

Papyrus swamps usually form at the interface between river inlet and open lake. From one such wetland ecosystem (the Kibos system located in the Nyanza Gulf, Lake Victoria, Kenya), three sediment cores were recovered using piston corer in order to determine the fate of organic matter derived from papyrus and possible nutrient pathways in this system. The coring represented a transect from the river through the floating papyrus mat to the lake. Two short cores were retrieved from the lake and river. One long core (2 m) was recovered on a floating papyrus mat. The C:N ratio showed similar trends down core from the three locations. This may possibly be due to diagenic processes such as autolysis, dissolution and microbial mineralisation occurring in the sediments. Statistical analysis through one-way ANOVA revealed no significant differences in the C:N ratios between stations. Results of the stable carbon isotope ratios revealed that the delta(13)C of the river and lake samples were persistently more negative than -20 per thousand over the whole profile indicating possible contribution from terrestrial derived carbon. Regarding the floating mat core, the delta(13)C values ranged from -18.99 per thousand on the top of the floating mat but gradually increased to -16.82 per thousand towards the bottom of the core indicating possible contribution of carbon from Cyperus papyrus that has a delta(13)C value of -13.45+/-0.62 per thousand. Statistical analysis through one-way ANOVA revealed significant differences in the delta(13)C values between stations. The stable nitrogen isotope values were highly positive both in the river and in the lake station (delta(15)N > 10 per thousand), indicating possible contamination from sewage wastes. Values in the swamp were less positive suggesting first, the formation of ammonium depleted in (15)N from intense organic matter mineralisation, secondly indicating the delta(15)N signal of papyrus and, finally that nitrogen fixation processes were possibly occurring in the swamp. Statistical analysis through one-way ANOVA revealed significant differences in the delta(15)N values between stations. The stable isotope findings suggested that carbon derived from papyrus is retained in the swamp. Impoverished oxygen concentration in the swamp suggests high mineralisation of organic matter in the swamp indicating that the retained papyrus-derived carbon is largely respired. We conclude that further studies should be undertaken to determine the respiration rates in the wetland.     

Diurnal variations in the photosynthesis-respiration activity of a cyanobacterial bloom in a freshwater dam reservoir: an isotopic study

The stable isotopic analyses of molecular oxygen dissolved in water (delta18O(DO)) and dissolved inorganic carbon (delta13C(DIC)), supplemented with basic chemical measurements, have been carried out on a diurnal basis to better understand the dynamics of photosynthesis and respiration in freshwater systems. Our observations have been carried out in a lowland dam reservoir, the Sulejow Lake (central Poland), during the summer cyanobacterial bloom. All data obtained, isotopic, hydrochemical, and biological, show a high mutual consistency. Namely, the lowest delta18O(DO) values, obtained at 10:00 and 14:00 (16.0 and 15.5 per thousand, respectively), correspond to the highest amount of cyanobacterial cells observed (66 and 63 mg dm(-3), respectively), whereas the minimum delta13C(DIC) (-10.6 per thousand) obtained at 22:00 corresponds to the maximum content of organic matter (110 mg dm(-3)). This evidence suggests that isotopic assays of delta18O(DO) and delta13C(DIC) are a reliable tool for the quantitative study of biochemical processes in freshwater systems.     

Flooding of lignite mines: isotope variations and processes in a system influenced by saline groundwater

The quality of both groundwaters and surface waters that arise during flooding of abandoned lignite open pits are influenced by regional and local factors. A typical regional factor is due to oxidised sedimentary sulfides. A more local factor is the interaction of shallow water with highly saline groundwater, which is important in Merseburg-Ost (Germany). Investigation of this system is aided by the use of many environmental isotope tracers but special problems can arise. In order to reveal processes in the mine environment (shallow groundwater, lake water) and to characterise mixtures with saline groundwater results are described using the tracers deltaD, delta18O, delta13C, delta34S, 87Sr/86Sr, 3H, 14C, 39Ar, and 222Rn. Deep highly saline groundwater had a radiocarbon concentration typically below 10 pMC. The values of delta13C(DIC) are around-5 per thousand. As delta13C of the aquifer rock samples (Permian, Zechstein carbonates) was in the range of-6...+5 per thousand, residence time corrections based on delta13C are questionable. Additional checks with 39Ar, as well as results from the variationof delta18O (or deltaD) with respect to the salinity, emphasise a Holocene age; as is also the case for most mineralised groundwaters and also for water having a low delta18O (and deltaD). For saline groundwater residing in the Zechstein aquifer the measured delta34S values of about 12 per thousand are close to those expected from the literature. In contrast, the 87Sr/86Sr ratio of dissolved strontium is far from the values anticipated for the aquifer rocks despite there being proportionality between the chloride concentration and the strontium concentration. Furthermore, the proportionality is not valid in lower mineralised water. The 87Sr/86Sr ratio can, therefore, hardly be used as a tracer for the distribution of ascending saline water. The amount of salt-water coming from below into the residual quarry basins is an essential contribution to the lake inventories. Therefore, 222Rn was used to assist in determining the renewal of salt-water layers that formed in deep lake locations. In the deep zones 222Rn concentrations up to 6 Bq/l were measured but were dominantly in equilibrium with 226Ra, which was found in all higher mineralised groundwater samples. Excess radon was limited to just a few decimetres above the lake sediment surface but does not appear to be caused by continuous groundwater discharge.Hydrochemical investigations of groundwater from the Quaternary aquifer were carried out over the last six years before flooding was complete. Apart from a slight downward shift of the average sulfate concentration, other changes showed virtually no trends. An increase of the sulfate concentration was mostly correlated with a decrease of delta34S for individual sites only, but not for the whole ensemble of sampling locations. Sulfate from pyrite oxidation plays an important role but cannot be attributed unequivocally to coal mining. There are hints that the conditions closer to the basin edges may differ from those remoter parts of the flood plain.     

Below-ground partitioning (14C) and isotopic fractionation (delta13C) of carbon recently assimilated by maize

Partitioning of carbon recently assimilated by maize between shoots, roots, exudates, and CO2 from root respiration depending on three different levels of nutrient supply (full nutrient solution (NS), 10 times diluted NS, or deionised water) was estimated by 14C pulse labelling. A 13C fractionation in these compartments was investigated in relation to the nutrient supply. With decreasing nutrient supply, 14C allocation to the shoots and to the roots decreased from 76 % to 69 % and increased from 8 % to 13 % of 14C recovery, respectively. Average percentage of 14C in exudates and root-respired CO2 was 0.5 % and 16 % of 14C recovery, respectively. The concentration of the NS was not crucial for the amount of recently assimilated C recovered in exudates and CO2, but for the amounts in shoots and roots. For all three nutrient levels, roots were enriched in 13C when compared with shoots and 13C fractionation increased with decreasing nutrient supply up to 0.7 per thousand. Further 13C discrimination by exudation led to more 13C in exudates when compared with the roots of full nutrient supply and less 13C in exudates when compared with the roots grown in diluted NS and in deionised water. There were only small differences of<1.0 per thousand in delta13C values between roots and CO2 from root respiration. A 13C fractionation of recently assimilated C occurred between roots and exudates but was negligible for the CO2 respired by roots.