Evaluating a Sediments Pollution Using Contamination Indices and Risk Assessment in Mineralized Zones, Eastern Iran

Abstract In this study, the results of nearly 1400 stream sediment sample analysis were processed to better understand environmental pollution caused by mining activities. Stream sediment samples were analyzed for As, Sb, Fe, Cr, Ni, Co, Cu, Zn, Pb, Sr, and Hg. The mean concentration of these elements followed the decreasing order of Fe > Sr > Zn > Cr > Cu > Ni > Co > Pb > As > Sb > Hg. Based on the assessment of pollution, extremely severe enrichment factor Co (EF > 25) and high enrichment of Sb, Hg, Cr, and Sr (EF > 10) were detected. Specifically, Cr and Ni in southern stream sediments showed significantly elevated concentrations compared to the others. The range of the contamination factor varied from CF  6 for most elements. Geo-accumulation index showed high contamination levels by Cr and Co and high to severe contamination by Sb. The risk indices were low for all elements except for As and Co in the eastern part of the study area. Principal component analysis, Pearson’s correlation coefficient and cluster analysis were used to demonstrate similarities and differences between the elements. Pollution indices showed that contaminations in some samples are the consequence of gold mineralization. The high correlation of Cu, Zn, and Sb is due to the sulfide mineralization of gold. The high correlation of Cr and Ni corresponds to ultramafic rocks and ophiolitic series. Based on the results presented here, while most contamination in the target area is rooted in geochemical and mineralization processes, mining activity also contributes to soil pollution for certain elements such as Cu and Zn.