Spatial variability of heavy metal ecological risk in urban soils from Linfen, China

Identifying areas of environmental exposure potential for humans due to contaminated soils is an ever growing concern for cities with extensive industrial histories. We applied a Potential Ecological Risk Index (RI) to evaluate the contamination degree of hazardous elements in soils from Linfen, northern China. The city has experienced extensive industrial pollution over time and is home to ～676,500 people. We analyzed in 0–10 and 10–20 cm soil depth the spatial distribution, sources and potential ecological risks of heavy metals (Cr, Ni, Cu, Zn, As and Pb) across Linfen in order to derive a human exposure risk map. Results indicate that the mean urban topsoil concentrations of Ni, Zn, As and Pb were 36.24 mg·kg⁻¹, 91.41 mg·kg⁻¹, 15.20 mg·kg⁻¹ and 28.12 mg·kg⁻¹, respectively, and exceeded corresponding background values. The coefficient of variation of Cu, Zn and Pb was greater than 50%, suggesting high variation in urban area. Contamination factor indices for Ni, Zn, As and Pb were higher than 1 and suggests urban soils in Linfen are moderately contaminated. The calculated 47.1% integrated pollution load index was higher than 1 and suggests that half of the city has an increasing pollution risk. The spatial variability of the Pollution Load Index and Risk Index suggest moderately to strongly contaminated areas in the east and center areas of the city. Our data suggest that Ni, As and Pb have the potential for posing the greatest ecological risk at most city sites and likely originated from numerous sources (vehicular traffic, exhaust, coal combustion, metal manufacturing and other anthropogenic activities) given the disparate spatial pattern and elevated concentrations relative to native soil background values.