A Snapshot Of The Geological, Hydrogeological And Anthropogenic Impacts On The Water Chemistry Of The Mohlin River, Black Forest

The subject of this study is the examination of the chemical composition of the Mohlin River with respect to its geology, hydrogeology and potential anthropogenic impacts. Water samples taken at different locations in the river were analyzed for Ca2+, Mg2+, Na+, K+, HCO3-, CO32-, SO42-, Cl-, F- and NO3- via alkalinity testing and ion chromatography. Electric conductivity, temperature, discharge and pH-values were measured as well as stable isotopes (delta D, delta O-18), which were analyzed by Cavity-Ring-Down-Spectroscopy. In the upper section, the Mohlin River can be classified as a siliceous water body, while the lower part of the river is at the transition between a siliceous and carbonatic water body. Out of all impact factors, the geology is the most important, while inflows also play a key role. Other impact factors on the water chemistry are anthropogenic discharges, hydraulic-engineering actions and legacy mining activities in the Alsace and the Black Forest regions. Despite these factors, the water quality of the Mohlin River can be classified as "good" in relation to the measured parameters.