Assessment of ecological pollution of heavy metals in surface soils of different sites within northwest of iraq

Abstract

Heavy metals pollution in surface soils of different urban areas in northwest Iraq were investigated. Correlation between screened metals’ spatial distribution (33 elements) and point and non-point pollution sources were performed. Obtained results showed that the levels of 15 elements (Hg, Ag, Cd, Sb, Sr, Ti, Mo, Rb, Sc, Zn, Ni, Cr, Cs, Te and Ca) exceeded the reference values of urban soil constituents. Higher observed levels of these metals, indicating that the urban soils of the studied areas are enriched with these contaminants. Further, higher concentrations of some “unexpected” toxic metals were detected in the studied locations. Estimated correlation coefficients of metal concentrations suggested three potential sources for soil pollution by heavy metals in the surveyed region. Different industrial activities, dominated by petroleum and petrochemical industries, are likely to be responsible for the releases of many heavy metals, e.g. Ni, Cr and Cu. Military activities were considered an important source for some toxic metals, e.g. Zr, Rb, V, and As, since these metals were observed at high levels in the studied sites. Trace metals such as Cu, Pb, Zn are found to be correlated with agricultural practices. However, the higher observed concentration of Ca in the surveyed locations can be attributed to natural processes’ impact. Overall, this research’s outcomes can be useful for the policymaking efforts dedicated to solving complex environmental problems related to soil pollution and being a guide for soil quality in northwest Iraq.