Natural attenuation of inorganic pollutants (copper, sulfate) in the aquifer below an industrial site

Abstract
The contamination of soils and aquifers by inorganic pollutants is so widespread in industrial sites that it does not seem economically feasible to decontaminate the large areas or soil volumes involved. It is therefore interesting to investigate whether the local environment is capable to attenuate this contamination. Natural attenuation by degradation seems realistic for many organic pollutants. Here we show that it can take place also for inorganic pollutants. The phreatic fill aquifer underlying an industrial plant located on the river banks of the Garonne River is contaminated by acidic water (pH down to 1) and high concentrations of sulfate (up to 50 g/L) and copper (up to 30 g/L). As acid water, rich in Cu and sulfate. migrates away from the contamination source, pH increases due to buffering of aquifer solids, dissolved Cu concentrations decrease by 6 orders of magnitude, while sulfate concentrations decrease little.