CONCENTRATION OF HEAVY METALS IN SOILS ALONG THREE MAJOR ROADS OF SULAIMANI, NORTHEAST IRAQ

Abstract

Heavy metal contamination of agricultural soils resulting from vehicle emissions is a cause of serious concern due to the potential health impacts of transferring to food chain. In this study, heavy metal concentration of roadside soils along three major roads connecting the city of Sulaimani to surrounding cities were determined. Twenty soil samples from each side of three roads were collected at 1 m, 15 m, 25 m and 50 m distances from road edges. The heavy metals of Cr, Co, Pb, Cd and Ni were analyzed by acid digestion. Heavy metal pollution of roadside soils was assessed using three different environmental indices; enrichment factor (EF), contaminant factor (CF) and contamination degree (CD). Heavy metals concentrations of roadside soils were significantly different (P?0.01) among three major roads and usually decreased with increased distance from the roads. The highest concentrations were 268.56, 9.56, 134.16, 3.99 and 179.20 mg kg-1 for Cr, Co, Pb, Cd and Ni, respectively. The results showed that mean concentrations of all heavy metals determined were significantly higher than the global background values of heavy metals. The order of heavy metal contamination based on CF values in Arbat road was Cr?Ni?Pb?Cd?Co, in Kirkuk road Ni?Cr?Cd?Pb?Co, and in Mergapan road Pb?Ni?Cr?Cd?Co. Significant positive correlations between Ni and Co in Arbat (r=089) and Kirkuk (r=0.58) roads, Ni and Pb in Mergapan road (r=0.70), and Cd and Pb in Kirkuk road (r=0.76) revealed their common source in the studied environments. The roadside soils in the region are being extensively used for agricultural production. Therefore, the increased concentration of Cr, Pb, Cd and Ni in roadside soils should be carefully monitored and necessary precautions should be taken to prevent further accumulation in roadside soils.