Heavy metal contamination of soils around a lead smelter at Port Pirie, South Australia

Abstract

A survey was made of the concentrations of EDTA-extractable lead, zinc, cadmium, and copper in surface soils at 472 sites surrounding an isolated lead smelter at Port Pirie, S.A. Contamination declined exponentially with distance near the smelter, but was detectable up to 40-65 km from the source depending upon direction. Close to the smelter, the fallout pattern was consistent with the direction of surface winds (NNW-SSE), but major contamination on hills 20 km due E was related to topography and rainfall and was independent of mean surface wind direction at the source. It is probable that most of the soil contamination occurred prior to 1940. The dispersion of heavy metals was ranked in the order cadmium > lead >> zinc. No contamination with copper was detected. The ratios lead/cadmium and zinc/cadmium for soils were high close to the smelter, but declined with distance to constant values. It was concluded that over short distances soil contamination resulted from the fallout of particulate emissions of variable composition, but beyond about 15 km the heavy metals are probably dispersed mainly as aerosols. The soils of the surveyed region were mostly of pH above 7.5, and vertical movement of heavy metals in soil profiles was negligible. Some implications of the results for human and animal health are discussed.