Spatial Eco-Risk Assessment of Heavy Metals in the Surface Soils of Industrial City of Aran-o-Bidgol, Iran.

Heavy metals usually accumulate and migrate in soil environment due to human activities and this in return poses potential ecological and health risks. A total of 135 surface soil samples were collected from Aran-o-Bidgol City, Iran and were analyzed for their Cd, Pb, Ni and Cu concentrations to determine these elements' spatial distribution and potential ecological risks. To this end, interpolation mapping was conducted using Ordinary Kriging. The mean concentrations of Cd, Pb, Ni and Cu in the samples were 0.72, 11.41, 29.87 and 14.82 mg kg(-1), respectively, which were all higher than their background values. The spatial variation in the concentration of heavy metals could be attributable to point sources and vehicle emissions. Considering the severity of the potential ecological risks of metals, the descending order of contaminants' concentrations was Cd > Cu > Ni > Pb. The Potential Ecological Risk Index (RI) suggested that approximately 40 % and 59 % of the samples posed high and significantly high potential ecological risks, respectively. Moreover, ecological risk decreased progressively going from southwest to northeast over the under-study area. Considering the background values and RI, this area presented a relatively high level of contamination.