Heavy metals in soil of an urban industrial zone in a metropolis: risk assessment and source apportionment

The risk of heavy metal pollution in industrial zones has received great awareness, but few studies have focused on urban industrial zone of metropolises. In order to explore the pollution characteristic, ecological risks, human health risks, and sources apportionment of heavy metals (HMs), the concentrations of 9 HMs (As, Cd, Cr, Cu, Hg, Mn, Ni, Pb, Zn) in 48 soil sites of a typical urban industrial zone in Shanghai, China were investigated. The mean concentrations of HMs except As (8.09 mu g/g) were higher than the background value of corresponding HMs in Shanghai, with Mn (717.60 mu g/g) having the highest concentration. The geo-accumulation index showed that Mn had the most severe pollution. The potential ecological risk index indicated that most HMs were at lower risk, but Hg posed a relatively high risk in many sites. In addition, the entire study area may cause potential ecological risks, especially in the northern and the southeastern areas. In light of the results regarding health risk assessment for children and adults, HMs were negligible of non-carcinogenic risk in humans. As for carcinogenic risk, all HMs had "no significant" cancer risk, except for Cr and Ni at the "acceptable" levels. The results of source apportionment analysis using the positive matrix factorization model indicated that heavy metal pollution was mainly caused by (1) metal manufacturing, (2) machinery manufacturing, (3) pesticides and fertilizers, and (4) manufacture and metallic materials. Our results provide the underlying insights needed to guide soil pollution management and remediation of urban industrial areas in metropolises.