Peatlands as Filters for Polluted Mine Water?—A Case Study from an Uranium-Contaminated Karst System in South Africa

Located downstream of goldfields of the Witwatersrand basin, the Gerhard Minnebron (GMB) Eye—as major water source for downstream community of some 300,000 people—may be impacted on by mining-related water pollution especially with uranium (U). Containing up to 5 m-thick deposits of peat that is frequently reported to act as a filter for U and other heavy metals, this paper is the first part of a series that aims to quantify the ability of the GMB peatland to act as buffer against current and future U pollution. In a first step, this paper outlines the geohydrological conditions and discusses how deep–level gold mining impacted on the dolomitic aquifers. Subsequently, the potential influx of U into the wetland is estimated and associated sources and pathways analyzed. Finally, a model is proposed explaining the significant differences in degree and dynamics of U observed within a single groundwater compartment.