To assess the environmental consequences of heavy metals (HMs) in the soil, the study of soil pollution sources and indicators has an important role in environmental decision-making activities. This study aimed at investigating pollution sources and indicators in three study sites, namely, an industrial town (It), landfill (Lf), and wastewater treatment plant (WTP) in the vicinity of Ilam city, Iran. To achieve this objective, the sampling was performed from the topsoil (0–10 cm) of three sites (It, Lf, and WTP) with pollution potential. After laboratory analysis of some soil physio-chemical properties and total concentration of HMs including cadmium (Cd), lead (Pb), nickel (Ni), chromium (Cr), and cobalt (Co), pollution indicators and sources of pollution were evaluated by statistical analysis. The results of the geoaccumulation index (Igeo), enrichment factor (EF), contamination factor (CF), and pollution load index (PLI) showed that the studied areas were contaminated with HMs. The highest average of Cd and Pb were 1.45 mg kg-1 and 440.19 mg kg-1, respectively, in the Lf. Whereas, the highest average of Ni and Cr were 106.53 mg kg-1 and 43.50 mg kg-1, respectively, in the IT, while the highest average of Co was 81.69 mg kg-1 in the WTP. According to the results of the principal components analysis (PCA) and clustering, a small part of the Pb, Ni, and Co amounts in the soils had the natural origin, while the results confirmed that a significant proportion of Pb, Cd, and Cr concentrations associated with human-caused hazards. Moreover, all areas (especially Lf and WTP sites) were highly contaminated with Cd. Due to the higher mobility of Cd and its human health hazards, this metal should be given more attention in the study sites of Ilam city. In general, based on our results, more paying attention needs to be considered by decision-makers and stakeholders to manage and control pollution production sources in the soils of the study sites.
