Assessment of level and source identification of heavy metals in the surface soil of the roadside: A case study

Road transportation is one of the most important and main sources of metal pollution, which has turned roadside ecosystems into metal sensitive areas. Therefore, this study was conducted to analysis and source identification of Zn, Pb, Cd, Co, Cr, Cu, Mn, and Ni in the surface soils along some roads in Hamedan Township in 2019.

In this study, a total of 63 surface soil samples were collected along 700 m from a 9 km section of Goltepe (G), Razan (R) and Kermanshah (K) roads. After preparing soil samples, the contents of elements were determined using ICP-OES. The enrichment contamination severity index (CSI) was also calculated. All statistical analyses of the obtained data were performed using SPSS software.

The highest amounts of all the analyzed elements were found in the samples collected from the R site with 122, 0.320, 1.92, 17.3, 334 and 22.2 mg/kg for Zn, Cd, Co, Cr, Mn, and Ni, respectively, and from K site with 26.4 and 25.0 mg/kg for Pb and Cu, respectively, showing the effect of traffic volume. The values of the CSI index showed the acceptable quality of the soil in the studied sites. Also, the results of multivariate statistical analyzes (PCC, PCA and HCA) showed that Mn in roadside soils is probably caused by soil raw materials and exhaust emissions. While the origin of Zn, Pb, Cd, Co, Cr, Cu and Ni emission was mainly from non-exhaust sources (such as wear of brakes, tires, engines and lubricating oil).

The findings were indicated the impact of traffic activities on soil contamination with heavy metal in the study areas; therefore, regular and periodic monitoring of soil samples is recommended to control of emission sources of pollutants in order to maintain the health of ecosystems and humans.