Anthropogenic-influenced hydrochemical processes in a quaternary anoxic aquifer of the Oder River polder Oderbruch

摘要

The hydrochemistry in the largest polder of the Oder river, named Oderbruch, is impacted by a year-long infiltration of water from the Oder into the aquifer below the alluvial loamy top layer of the polder. These exceptional hydraulic conditions are a result of dike constructions created more than 250 years ago. The goal of the investigation is a better understanding of the substance dynamics within the contact zone between the anaerobic ground water and surface water of a vast drainage system. Induced by changing water levels, different ex- and infiltration conditions occur which strongly influence the hydrochemical conditions of the aquifer. Field investigations with a hydrochemical and hydraulic characterization of selected ditch locations show an extremely high matter dynamic at exfiltrating ditch locations. Within a few decimeters, the redox processes create an extreme chemical gradient combined with a distinct heavy metal enrichment. In the exfiltration zone, more than 10 kg iron and 0.15 kg manganese have accumulated in the last three decades.