Source identification and ecological risk assessment of some heavy metals in surface soils collected from the vicinity of Arad-Kouh processing and disposal complex, Tehran, Iran

Heavy metals are the common pollutants of soils, which pose a potential threat to the public and particularly children's health. Therefore, this study was conducted to assess the source identification and potential ecological risk of Fe, Zn, Pb, Cd, Cr, and Ni in surface soils collected from the vicinity of Arad-Kouh processing and disposal complex, Tehran, Iran in 2020.

In this descriptive study, a total of 30 surface soil samples were collected from 10 sampling sites. After acid digestion of soil samples, the element contents were determined using ICP-OES. Also, pollution indices, potential ecological risk were computed. Moreover, principal component analyses (PCA) and hierarchical cluster analysis (HCA) were performed to find out the contamination sources and distinguish the different groups of analyzed elements from different sources, respectively. Furthermore, all statistical analyses were performed by SPSS software.

Based on the results obtained, the mean content of elements in soil specimens (mg/kg) was 26651.6 for Fe, 71.7 for Zn, 27.7 for Pb, 1.22 for Cd, 22.3 for Cr, and 32.8 for Ni. On the other hand, the soil quality of the study area was varied between 'minor enrichment' to 'moderately severe enrichment' based on the enrichment factor (EF) values, between 'low contamination' to 'high contamination' based on the pollution index (PI) values, and between 'unpolluted' to 'moderately polluted' based on the geo-accumulation index (I-geo) values and also showed 'moderate degree of contamination' based on the degree of contamination (DC) values. The computed values of Er showed that the potential ecological risk of Zn, Pb, Cr, and Ni was low and for Cd was moderate. Also, as the mean values of RI were 170.9, all the examined elements could be classified as a moderate ecological risk. The results of Pearson correlation coefficient, I-geo, PI, and IPI in accordance with PCA and HCA indicated that Zn, Cd, Cr, and Ni were originated from anthropogenic sources, while, Pb had a lithogenic origin.

Although the studied elements had moderate potential ecological risk, since the Cd with 93.3% of the mean RI values showed a higher potential environmental risk compared to other elements, therefore, source identification and source control of this element with potentially adverse effects on humans and also environmental health is recommended.