Freshwater Colloquium: Groundwater management in Northeast Wisconsin: Potential for geogenic metals mobilization

Groundwater quality can be impacted by metals released from aquifer minerals, potentially causing human health concerns. When aquifer sediments are relatively undisturbed, metals bound to minerals remain stable, but during transitions in water level – due to variations in groundwater recharge or over-pumping – metals can be released to groundwater. This project evaluates the history of groundwater use in the Northeast Wisconsin Groundwater Management Area (GMA) for the confined Cambrian-Ordovician aquifer, and explores the potential for metals release due to oxidation during aquifer drawdown.

To evaluate these changes, (1) groundwater was sampled across the GMA for evaluation of water chemistry, (2) a monitoring well was installed to improve groundwater level monitoring in the southern portion of the GMA, and (3) batch leaching experiments were conducted under oxic and anoxic conditions with rock cuttings from the newly installed monitoring well to evaluate potential for metals release. Initial leaching experiment results show that nickel and cobalt increased over time in oxic experiments, but not in anoxic experiments, and negligible arsenic was observed over the experimental timeframe. This study provides initial results that support improved understanding of metals release from oxidized GMA aquifer sediments. Findings from this study will inform the development of effective groundwater management strategies, ensuring the sustainability and safety of water resources in the Northeast Wisconsin GMA.