A geochemical survey of heavy metals in agricultural and background soils of the Isfahan industrial zone, Iran

There is a growing public concern about the potential accumulation of heavy metals in agricultural soils of Iran. This is mainly the result of rapid urban, mining and industrial discordant development over the last several decades, which has jeopardized the ecology, food safety, human health, and sustainable development of agriculture. To investigate the soil pollution, a total of 105 agricultural soil samples and 40 background soil samples were collected from the Isfahan industrial zone. Accordingly, total concentrations of 7 heavy metals (including Cu, Pb, Zn, Cd, Ni, Co and Cr), associated with Al, Fe, Mn and some physicochemical properties of soils were determined. The geochemical background and threshold was predicted using the Median Absolute Deviation (MAD) method. The median concentrations of heavy metals in agricultural soil were nearly similar to those of background soil, with some outlier data in the vicinity of the industrial and mining areas. Based on correlation coefficient and factor analyses, the primary source of Ni, Co, Cr, Fe and Al was determined to be geogenic, whereas the source of Pb, Zn and Cd is substantially controlled by anthropic activity. Our observations proved that in the Isfahan industrial zone, both human and natural sources affect the concentrations of Cu and Mn. Maps of heavy metal pollution indices in agricultural soils reveal high level of pollution in the vicinity of BamaPb-Zn mining area along with Esfahan and Mobarakeh Iron-Steel plants.