Denitrification coupled to pyrite oxidation in a sandy aquifer: Stable isotopic and microbiological evidence

Denitrification coupled to pyrite oxidation is a natural attentuation process for nitrate in groundwater. Side effects include the mobilization of trace metals, the production of sulfate and changes in groundwater pH. These changes all potentially threaten groundwater quality. In this study, we investigate this process in a sandy aquifer using multi-isotope (δ34S-SO4, δ18O-SO4, δ15 N-NO3, δ18O-NO3) and microbial analyses. Our study area is located at Oostrum, the Netherlands, where maximum concentrations of nitrate and sulfate in groundwater are 8 mM (500 mg/L) and 4 mM (400 mg/L), respectively. © 2010 Taylor & Francis Group, London