Spatial distribution and chemical partitioning of potentially toxic elements in soils around Khatoon-Abad Cu Smelter, SE Iran

Abstract

The objective of this study was to assess the environmental impacts of Khatoon Abad Cu smelter, SE Iran, on soil contamination and to investigate the chemical partitioning of potentially toxic elements (As, Cd, Cu, Mo, Pb and Zn) in the soils. For this purpose, topsoil and subsoil samples were collected and analyzed using standard methods; dust, slag, and concentrate samples were characterized for reference. The results showed elevated concentrations of As (up to 441.8 mg kg−1), Cd (up to 11.4 mg kg−1), Cu (up to 12,611 mg kg−1), Mo (up to 178.2 mg kg−1), Pb (up to 316 mg kg−1) and Zn (up to 803 mg kg−1) in <63 μm fraction of topsoil samples. The highest recorded concentrations for these elements were in soils collected in downwind direction. The concentration of smelter driven metals in topsoil samples decreased with increasing distance from the Cu smelter and also with increasing depth of the soil samples. The granulometric distribution of the soil samples as well as the mineralogical and geochemical composition of dust sample confirms the impact of smelting activity on the surrounding soils. On the basis of sequential extraction data, the highest percentage for exchangeable, carbonate, reducible, oxidizable, and residual fractions were recorded for Cd (26.5%), Zn (35.5%), As (47.7%), Cu (28.7%) and Mo (37.8%), respectively. The anthropogenic activity (Cu smelting) was the main parameter controlling the metal chemical partitioning because the percentage of non-residual fractions of the studied elements decreased with increasing distance from the Cu smelter and also decreased with increasing depth of the soil samples. Human risk assessment indicated non-carcinogenic (hazard quotient of 1.7) risk to the population and carcinogenic (Incremental Lifetime Cancer Risk of 7.71E-04) risk of As to the children, through the ingestion pathway. The hazard quotient of dermal contact (to the children) is 1.4 for Cu at one site located around the smelter. The results of a single extraction test confirmed the higher risks of As and Cu through ingestion pathway compared with other studied elements. The results of this study show that more attention should be given to the potentially toxic elements (PTEs) pollution in Khatoon Abad area.