Environmental Impacts of an Old Mine Tailings Deposit — Metal Adsorption by Particulate Matter

The distribution of metals (aluminum, manganese, iron, copper, zinc, cadmium and lead) between suspended particles and solution phase has been studied by analysis of time series data in a stream receiving leachates from a mine tailings deposit. A precipitation of aluminum and iron takes place when the acidic effluents are neutralized by unpolluted groundwater, while the other dissolved elements never reach saturation. The particulate fraction is largely amorphous. A transfer of dissolved elements from the solution phase to the particle phase, increasing in the order zinc < cadmium < copper < lead with increasing pH, is observed. This removal of metals from the aqueous phase appears to be due to sorption processes rather than to coprecipitation. The formation of a particulate metal fraction could be the means for long-range transportation and redistribution of metals in environmental water systems.