TY  - JOUR
A1  - Osenbrück, Karsten
A1  - Blendinger, Eva
A1  - Leven, Carsten
A1  - Rügner, Hermann
A1  - Finkel, Michael
A1  - Jakus, Natalia
A1  - Schulz, Hartmut
A1  - Grathwohl, Peter
T1  - Nitrate reduction potential of a fractured Middle Triassic carbonate aquifer in Southwest Germany
Y1  - 2021-12-07
VL  - 30
IS  - 1
SP  - 163
EP  - 180
JF  - Hydrogeology Journal
DO  - 10.1007/s10040-021-02418-9
PB  - Springer Berlin Heidelberg
N2  - 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.
UR  - http://resolver.sub.uni-goettingen.de/purl?gldocs-11858/10996
ER  -