Global Change Abstracts The Swiss Contribution - SCNAT

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142 Global Change Abstracts – The Swiss Contribution | Oceans and Fresh Water Systems 08.1-275 Hydrological heterogeneity of an alpine stream-lake network in Switzerland Robinson C T, Matthaei S Switzerland Limnology , Water Resources , Hydrology Water source and lake landscape position can strongly influence the physico-chemical characteristics of flowing waters over space and time. We examined the physico-chemical heterogeneity in surface waters of an alpine stream-lake network (>2600 m a.s.l.) in Switzerland. The catchment comprises two basins interspersed with 26 cirque lakes. The larger lakes in each basin are interconnected by streams that converge in a lowermost lake with an outlet stream. The north basin is primarily fed by precipitation and groundwater, whereas the south basin is fed mostly by glacial melt from rock glaciers. Surface flow of the entire channel network contracted by similar to 60% in early autumn, when snowmelt runoff ceased and cold temperatures reduced glacial outputs, particularly in the south basin. Average water temperatures were similar to 4 degrees C cooler in the south basin, and temperatures increased by about 4-6 degrees C along the longitudinal gradient within each basin. Although overall water conductivity was low (300 µg 1(-1) (nitrite + nitrate-nitrogen), whereas particulate nitrogen was approximately nine times greater in the north basin (seasonal average: 97 µg 1(-1)) than in the south basin (seasonal average: 12 µg 1(-1)). Total inorganic carbon was low (usually
Global Change Abstracts – The Swiss Contribution | Oceans and Fresh Water Systems hydrological soil information is not available at a European scale, we reclassified the Soil Geographical Database of Europe (SGDBE) at 1:1 million in a hydrological manner by adopting the Hydrology Of Soil Types (HOST) system developed in the UK. The HOST classification describes dominant pathways of water movement through soil and was related to the base flow index (BFI) of a catchment (the longterm proportion of base flow on total stream flow). In the original UK study, a linear regression of the coverage of HOST classes in a catchment explained 79% of BFI variability. We found that a hydrological soil classification can be built based on the information present in the SGDBE. The reclassified SGDBE and the regression coefficients from the original UK study were used to predict BFIs for 103 catchments spread throughout Europe. The predicted BFI explained around 65% of the variability in measured BFI in catchments in Northern Europe, but the explained variance decreased from North to South. We therefore estimated new regression coefficients from the European discharge data and found that these were qualitatively similar to the original estimates from the UK. This suggests little variation across Europe in the hydrological effect of particular HOST classes, but decreasing influence of soil on BFI towards Southern Europe. Our preliminary study showed that pedological information is useful for characterising soil hydrology within Europe and the long-term discharge regime of catchments in Northern Europe. Based on these results, we draft a roadmap for a refined hydrological classification of European soils. Hydrology and Earth System Sciences, 2007, V11, N4, pp 1501-1513. 08.1-278 Selecting scenarios to assess exposure of surface waters to veterinary medicines in Europe Schneider M K, Stamm C, Fenner K Switzerland Water Resources , Agriculture, Soil Sciences Registering a veterinary medicinal product (VMP) in the European Union requires assessing its potential to contaminate surface waters (SW) on a European scale. VMP are spread to land in manure or excreted during grazing and may enter SW through runoff, erosion, or leaching. Since the factors driving these processes vary largely across Europe, it is necessary to identify characteristic conditions, so-called scenarios, un(er which VMP enter SW. These scenarios may guide the parameterization of mechanistic fate models to predict environmental concentrations for environmental risk assessment. A number of such scenarios for pesticides and VMP have been developed rather pragmatically. Here, we describe how a 143 geo-referenced European database of driving factors was used to divide the European environment into groups with similar conditions for SW contamination by VMP. Out of these groups, relevant exposure scenarios in Europe were selected by a simple scoring system. Comparing these to the existing scenarios showed that a number of situations are not well covered. The newly identified scenarios are primarily located in hilly areas of Central Europe and the Mediterranean, and in Eastern European plains with a continental climate. We recommend that they are included in the technical guidelines for higher-tier assessment of VMP. Environmental Science Technology, 2007, V41, N13, JUL 1, pp 4669-4676. 08.1-279 Assessing iron-mediated oxidation of toluene and reduction of nitroaromatic contaminants in anoxic environments using compound- specific isotope analysis Tobler N B, Hofstetter T B, Schwarzenbach R P Switzerland Geochemistry & Geophysics , Microbiology , Marine & Freshwater Biology We evaluated compound-specific isotope analysis (CSIA) as a tool to assess the coupling of microbial toluene oxidation by Fe(III)- reducing bacteria and abiotic reduction of nitroaromatic contaminants by biogenic mineral-bound Fe(II) species. Examination of the two processes in isolated systems revealed a reproducible carbon isotope fractionation for toluene oxidation by Geobacter metallireducens with a solid Fe(111) phase as terminal electron acceptor. We found a carbon isotope enrichment factor, epsilon(C), of -1.0 +/- 0.1%o, which corresponds to an apparent kinetic isotope effect (AKIE(C)) of 1.0073 +/- 0.0009 for the oxidative cleavage of a C-H bond. Nitrogen isotope fractionation of the reduction of nitroaromatic compounds (NAC) by mineral-bound Fe(11) species yielded a nitrogen isotope enrichment factor, EN, of -39.7 +/- 3.4%o for the reduction of an aromatic NO 2-group (AKIE(N) = 1.0413 +/- 0.0037) that was constant for variable experimental conditions. Finally, AKIE values for C and N observed in coupled experiments, where reactive Fe(11) was generated through microbial activity, were identical to those obtained in the isolated experiments. This study provides new evidence on isotope fractionation behavior during contaminant transformation and promotes the use of CSIA for-the elucidation of complex contaminant transformation pathways in the environment. Environmental Science Technology, 2007, V41, N22, NOV 15, pp 7773-7780.
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