Distribution and source identification of heavy metals in the soil surrounding Kermanshah Refinery, Iran

Oil products are considered to be life-threatening factors in the ecosystem due to their contents of organic compounds, sulfide, sulfur, heavy metals, and various circular hydrocarbons, organic solvents, aromatic compounds, linear formaldehyde, fats, and grease. The present study aimed to investigate the soil surrounding Kermanshah Refinery, Iran and estimate the density of various heavy metals and their pollution sources, including arsenic (As), cadmium (Cd), cobalt (Co), chromium (Cr), nickel (Ni), zinc (Zn), lead (Pb), copper (Cu), scandium (Sc), and vanadium (V). The geoaccumulation index indicated that the intensity of the refinery soil had variable degrees of pollution, ranging from no pollution to average pollution with chromium and nickel. In addition, the enrichment index showed average enrichment for cadmium (station 14), copper (stations two, 11, 13, and 14), lead (stations six and 13), zinc (stations two, six, 11, and 13), and chromium (stations 6-15). On the other hand, the pollution bar index of chromium, copper, nickel, zinc, and lead was estimated to be higher than one, which confirmed unacceptable soil quality and the presence of soil pollution in the region. According to the results of Pearson's correlation-coefficient, nickel pollution was significantly correlated with chromium and scandium pollution, while cobalt pollution was associated with vanadium and chromium pollution. Moreover, a significant correlation was observed between zinc and copper pollution, which indicated the equal pollution source or similar geochemical behaviors of these elements toward each other. Since vanadium is considered to be an oil pollution index, it could be concluded that high pollution with this element and chromium may arise from petroleum in the studied region.