Analysis, spatial distribution and ecological risk assessment of heavy metals in surface soils, the case of Khorramabad, Iran

In this study, the contents of potentially toxic elements (Cd, Cr, Pb, Cu, Zn, Ni and Mn) in urban surface soils collected from city of Khorramabad were determined to assess the soil contamination rates, potential ecological risks and also spatial distribution of the analyzed elements. In so doing, a total of 55 surface soil samples were collected from 11 sampling sites. After acid digestion of samples, the contents of the elements were determined using flame atomic absorption spectrometer. Then, the pollution rates and potential ecological risks of the soil samples were assessed using various models including geo-accumulation index (I-geo), potential ecological risk index (RI), enrichment factor (EF) and pollution load index (PLI). The spatial distribution of the analyzed elements was estimated using the kriging interpolation technique. Based on the results, the observed mean I-geo values could be classified as "unpolluted" for all heavy metals in the study area. Besides, the EF values of Fe (1), Zn (340), Cr (445), Cd (1000), Ni (605), Cu (874), Pb (316) and Mn (900) indicated that all the elements had extremely severe enrichment. Moreover, the RI values indicated that the whole study area could be categorized as 'moderate'. The values of PLI indicated that the study area could be considered as 'non-polluted'. The calculated values of the studied indices and their spatial distribution showed that the elements concentration in E (G3T4S1) and I (G6T2S2) sampling sites were more than those in the other sites and that, for managing and controlling the anthropogenic activities in those sites, special care and appropriate interventions are needed. In conclusion, while an increase in soil contamination in the study area is expected in the future, the use of bioaccumulator species for biomonitoring and bioremediation of the contaminated areas with potentially toxic elements (PTEs) is recommended.