26 research outputs found
Assessment of catchment response and calibration of a hydrological model using high-frequency discharge-nitrate concentration data
Wassergebundener Stofftransport in Flusseinzugsgebieten: verbessertes Verständnis durch Synthese von "Top-down" und "Bottom-up" Modellansätzen
Investigating hydrological drivers of nitrate export dynamics in two agricultural catchments in Germany using high-frequency data series
Streambed microbial communities in the transition zone between groundwater and a first-order stream as impacted by bidirectional water exchange
Impact of non-idealities in gas-tracer tests on the estimation of reaeration, respiration, and photosynthesis rates in streams
Groundwater-surface water exchange as key control for instream and groundwater nitrate concentrations along a first-order agricultural stream
In-situ mass spectrometry improves the estimation of stream reaeration from gas-tracer tests
Sorption and transformation of the reactive tracers resazurin and resorufin in natural river sediments
Methoden für die Abschätzung der Massenflüsse von Xenobiotika in verschiedenen Maßstäben in städtischen Gebieten
Nitrate reduction potential of a fractured Middle Triassic carbonate aquifer in Southwest Germany
Nitrate reduction constitutes an important natural mechanism to mitigate the widespread and persistent nitrate contamination of groundwater resources. In fractured aquifers, however, the abundance and accessibility of electron donors and their spatial correlation with groundwater flow paths are often poorly understood. In this study, the nitrate reduction potential of a fractured carbonate aquifer in the Upper Muschelkalk of SW Germany was investigated, where denitrification is due to the oxidation of ferrous iron and reduced sulfur. Petrographical analyses of rock samples revealed concentrations of syn-sedimentary and diagenetically formed pyrite ranging from 1 to 4 wt.% with only small differences between different facies types. Additional ferrous iron is available in saddle dolomites (up to 2.6 wt.%), which probably were formed by tectonically induced percolation of low-temperature hydrothermal fluids. Borehole logging at groundwater wells (flowmeter, video, gamma) indicates that most groundwater flow occurs along karstified bedding planes partly located within dolomites of the shoal and backshoal facies. The high porosity (15–30%) of these facies facilitates molecular diffusive exchange of solutes between flow paths in the fractures and the reactive minerals in the pore matrix. The high-porosity facies together with hydraulically active fractures featuring pyrite or saddle dolomite precipitates constitute the zones of highest nitrate reduction potential within the aquifer. Model-based estimates of electron acceptor/donor balances indicate that the nitrate reduction potential protecting water supply wells increases with increasing porosity of the rock matrix and decreases with increasing hydraulic conductivity (or effective fracture aperture) and spacing of the fracture network.Deutsche Forschungsgemeinschaft
http://dx.doi.org/10.13039/501100001659Eberhard Karls Universität Tübingen (1020