CADMIUM MOBILIZATION UNDER CONDITIONS SIMULATING ANAEROBIC TO AEROBICTRANSITION IN A LANDFILL LEACHATE-POLLUTED AQUIFER

The anaerobic conditions in landfill leachate-polluted aquifers can le ad to trapping of many heavy metals as sulfide precipitates. In labora tory experiments with aqueous systems containing sulfidic solid phases (aquifer solids from a landfill leachate plume or amorphous FeS), cad mium previously trapped as a sulfide precipitate was released to the a queous phase when conditions were changed from initially slightly anae robic to aerobic. Cadmium was subsequently removed from solution eithe r by adsorption on Fe oxyhydroxide phases or by precipitation as a car bonate mineral, groundwater pH being the major controlling variable.