Comprehensive Risk Assessment of Heavy Metals in Topsoil and Their Risks to Human Health and Ecosystem in Zanjan Mineral Province, Western Iran

In total, 357 soil samples of six metals across the Province of Zanjan in northwest Iran were collected and analyzed. To assess the heavy metal pollution, the spatial distribution patterns, multivariate analysis, and various environmental indices such as enrichment factor (EF), geo-accumulation index (Igeo), contamination factor (Cf), potential ecological risk index (PER), and pollution load index (PLI) were employed. In addition, hazard quotient (HQ), hazard index (HI), and total carcinogenic risk (TCR) were used to approximate the carcinogenic and non-carcinogenic effects of heavy metals. Our experimental results indicated that mean concentrations (sample station %) of Zn (86%), Pb (85%), Cd (91%), Cu (8%), and Ni (9%) exceeded the world crustal average, except for Fe. Ecological indicators, such as EF, Igeo, Cf, and PER, showed that Zn, Pb, and Cd are the most concerning pollutants and potentially pose the most outstanding ecological risk. The average total hazard index values for studied heavy metals were 0.218 and 1.083, and the total cancer risks were 9.76E-05 and 1.60E-04 for adults and children, respectively. It was evident that both non-carcinogenic and carcinogenic risks posed by soil metals were above acceptable levels for children.