Evaluation of the Pollution by the Potentially Toxic Elements in the Topsoils of a Semi-Industrial Zone, Northwestern Iran

Various industries, including cement production, petrochemical processing, and power plants, exert significant environmental impacts on their surroundings. The close proximity of these industries within the study area underscores the critical need to investigate soil pollution of potentially toxic elements and elucidate possible pollution sources and associated risks. The present study involved taking 44 topsoil (0–10 cm) samples of Arsenic (As), Cadmium (Cd) Cobalt (Co), Chromium (Cr), Copper (Cu), Nickel (Ni), Lead (Pb), and Zinc (Zn) concentrations, which their mean concentration were found to be 11.29, 0.46, 15.89, 67.36, 44.36, 79.93, 8.50 and 68.27 mg kg−1, respectively. Comparison with the baseline values stated in local and international soil quality guidelines has indicated higher As, Cd, Cr, Cu, and Ni concentrations. The soil pollution indices of the geoaccumulation index, pollution index, pollution load index, and enrichment factor pollution have evaluated the pollution status of the study area to be uncontaminated to moderately contaminated, moderately polluted, polluted, deficient enrichment to moderate enrichment classes, respectively. Ecological and health risks that involved the application of the single index of ecological risk, potential ecological risk, hazard quotient, hazard index, and cancer risk have revealed that the study area was ecologically in a low-risk state with an average potential ecological risk value of 90.38, while carcinogenic (10−6-10−4) and non-carcinogenic risks (>1) were also found to be in a tolerable range for human health. Possible pollution sources were identified using multivariate statistics and further confirmed and visualized by the spatial distribution maps obtained from the deterministic interpolation method of inverse distance weighting. These analyses have suggested that the soil pollution which its existence was confirmed by the related indices and comparisons, to the potentially toxic elements of Cr and Ni can be possibly attributed to the petrochemical and power plants, to Cd could be appointed to cement plant, and to Cu could be associated with agricultural activities. It has also been found that arsenic was determined to be a common pollutant among the three main industries.