Heavy metal contamination of soils around a Pb [sbnd]Zn smelter in Bukowno, Poland

Abstract

An exploratory study of the area surrounding a Pb Zn smelting and mining centre in Bukowno, Poland, detected significant contamination by heavy metals. The median concentrations for field and garden topsoils (0–10 cm depth) were: Pb 545 μg/g, Zn 2175 μg/g, Cd 14.8 μg/g and As 81 μg/g. Close to the smelter area, topsoil concentrations of Pb, Zn and Cd exceeded Dutch “C” and Polish “V” action levels indicating that remediation should be considered. In the nearby village, concentrations of Pb, Zn and Cd in garden topsoils generally exceeded Dutch “B” cutoff levels, indicating a need for further investigation. Significant contamination of subsoils (40–50 cm depth) was also found. Median subsoil concentrations of Pb, Zn and Cd were 339 μg/g, 1860 μg/g and 8.9 μg/g, respectively. These high subsoil concentrations may have resulted from mechanical mixing of soils during previous remediation attempts. Visual inspection of the site suggested that there were three main sources of heavy metals in the soils. Geochemical mapping of the contamination confirmed that the primary source of pollution has been the smelting operations, however, it was not possible to establish the relative importance of airborne dispersion of material from uncovered waste tips versus flue gas particulate dispersion. Mine waste surrounding small-scale historical mine shafts appear to be a second source of contamination, with localised affected areas of less than 1 hectare. Preliminary sequential extraction investigation has been applied to investigate differences between two soil samples and two potential source materials. The mineral phases that hold the heavy metals appear to be significantly different in the source materials compared to contaminated soils. This change in speciation of the metal is probably the result of natural weathering processes.