Investigating the Contamination Level and Health Risk of Potentially Toxic Elements in Surface Soil of the Roadside Environment

Soil contamination with heavy metals is an important, common environmental, public health challenge, and concern worldwide. Therefore, this study was conducted to evaluate the contamination level and health risk of potentially toxic elements (cobalt, copper, manganese and nickel) in the surface soil samples of the roadside environment of Hamedan in 2019. In so doing, 63 surface soil samples (0-15 cm) were collected along 700 m from a 9 km section of Goltepeh (G), Razan (R), and Kermanshah (K) roads. After acidic digestion of soil samples in the laboratory, the contents of elements were determined using ICP-OES. Based on the results obtained, the highest amounts of the analyzed elements (mg kg-1) were found in the samples collected from the R site (1.92, 334 and 22.2 for Co, Mn, and Ni, respectively), and for Cu with 25.0 mg kg-1 it was related to K site, which indicating the effect of traffic density on soil pollution. The calculated values of EF showed that the enrichment (pollution) of Cu, Mn and Ni in the stations with high traffic (Razan and Kermanshah roads) was greater than 1.5, indicating the effect of human inputs especially with the traffic origin, while the EF values for the Co indicated "non-contaminated or no enrichment" conditions. Also, the results of the health risk assessment showed that "ingestion" was the main route of exposure of children and adults to the non-carcinogenic risk (HQ) of soil contaminated with heavy metals. In all sampling stations, the values of cumulative non-carcinogenic risk index (HI) of the studied elements in both child, and adult groups indicated "low risk". In addition, Mn with an average of 82% had the highest share in causing non-carcinogenic risk for both children and adults. On the other hand, the carcinogenic risk (CR) of Co and Ni was negligible for both children and adults. Since the results indicating the impact of traffic activities on the contamination of roadside soil with heavy metals. Therefore, periodic monitoring of the sources of soil contamination in the roadside environment is recommended for the environmental and human health aspects.