Heavy metal pollution assessment in agricultural soils of Kermanshah province, Iran

Heavy metals in agricultural soils are of major environmental concern because of the longstanding toxicity and bioaccumulation of metals. We collected 53 soil samples from agricultural fields in Kermanshah province, Iran. Our results showed average concentrations of Zn, Cu, Ni, Cr, Mn and Fe were 74.6, 41.2, 131.5, 79.2, 559.1, and 25,935mg kg(-1), respectively. The concentrations of Zn (81%), Cu (98%), Ni (100%), Cr (98%) and Mn (79%) were greater than their background values in the world soils. Except for Ni (68%) and Cr (4%), the concentrations of Zn and Cu were lower than the maximum permissible levels suggested by the Iranian Environmental Quality Standard for agricultural soils. Multivariate statistical analyses successfully grouped the metals according to their anthropogenic or natural origins. The anthropogenic activities have resulted in Zn, Cu, and Fe accumulation in the agricultural fields, whereas Ni and Cr amounts are mainly derived from natural, combined with anthropogenic origins. On the other hand, Mn shows evidences of a geogenic source in the soils. The calculated results of enrichment factor (EF) and geo-accumulation index (I-geo) of the heavy metals reveal a similar order of Ni>Cu>Cr>Mn>Zn>Fe. The high EF and I-geo for Ni and Cu in agricultural soils indicate that there is a considerable Ni and Cu pollution probably. The EF and I-geo of Zn and Fe are low and the assessment results indicate an absence of distinct Zn and Fe pollution in agricultural soils. The assessment results of pollution indexes also support serious pollution of agricultural soils by Ni and Cu. In general, the integrated pollution index analysis indicates the agricultural soils in the region as seriously polluted.