Pollution and Potential Ecological Risk Assessment of Pb, Cd, Cr and Ni in Surface Soils Along some Roads of City of Hamedan

Background & Objective: The road traffic has become one of the main sources of metal pollution and could affect roadside soils. Therefore, this study was conducted to assess the pollution and toxicity potential of Pb, Cd, Cr and Ni in surface soils along some roads of city of Hamedan in 2019. Materials & Methods: In this descriptive cross-sectional study, a total of 63 surface soil samples were collected along 700 m of a 9 km section of Goltepe, Razan and Kermanshah roads. After samples preparation, Pb, Cd, Cr and Ni contents were determined using ICP-OES. The enrichment factor (EF), mean effect range-median quotient (mERM-Q), mean probable effect level quotient (mPEL-Q) and cumulative potential ecological risk (RI) indices were also calculated. Also, all statistical analyses of the obtained data were performed using SPSS software. Results: The results showed that the maximum mean contents of Pb, Cd, Cr and Ni in the soil samples with 26.4, 0.320, 17.3 and 22.2 mg/kg, respectively, were found to be in Kermanshah, Razan, Razan and Kermanshah sampling sites (i.e. the sites with high vehicle traffic), indicaing the effect of traffic volume. The mean EF values of Pb, Cr and Ni were higher than 1.50, showed that soil samples could be classified as 'moderate' to 'severe' category in the sampling sites with high traffic volume (i.e. Razan and Kermanshah) which represents the effect of traffic emmissions on the soil contamination, while for all the sampling sites the mean EF values for Cd indicated that soil samples could be classified as 'non-contaminated' or 'no enrichment' matrices. Also, the mean values of mERM-Q and mPEL-Q of analyzed elements indicated that the elemental probability toxicity of soil samples was 21%. On the other hand, the values of Er showed a 'low ecological risk' of all analyzed elements. Also, the average values of potential ecological risk factor increase in the following descending order: Cd > Ni > Pb > Cr. Besides, the average value of RI with 31.9 indicating that the analyzed elements in all the sampling sites were classified as 'low ecological risk'. Conclusion: Although the average values of RI were shown the acceptable soil quality in all the sampling sites, Cd with 82.4% of the mean values of RI showed significant potential to occurrence the ecological risk; therefore, therefore, source identification and especially source control of this toxic element with potentially adverse effects on humans and also environmental health is recommended.