Human health risk assessment and source analysis of metals in soils along the G324 Roadside, China, by Pb and Sr isotopic tracing

Metal pollution was studied along the G324 roadside in Xiamen, southeast China, based on the soil profile and the different distances from the road. A range of metal concentrations were determined using ICP-MS and evaluated using enrichment factors, human health risk assessment and potential ecological risk index. The pollution sources in the soil were examined using multivariate statistical analysis and Pb-Sr isotope tracing technology. The results showed that the high soil metal contents were mainly distributed at the depth of 0-30 m, and the distance from the highway of 0-7 m. In both topsoils and profile soils, Cd had the biggest ecological risk. According to the human health risk assessment, there is no risk for human health in the roadside. The multivariate statistical analysis showed that the surface soil was clearly affected by the traffic factors; however, the profile soil was not only influenced by the traffic factors, but also by the industrial production. The results of analysis of Pb isotopic compositions showed that in the profile, the binary mixing of two major Pb sources (parent material and vehicle exhaust), the contribution rates were 78.29% and 21.71% on average, respectively. In topsoil, at a distance of 0-7 m away from the roadside, the two sources were also parent material (75.96%) and vehicle exhaust (24.04%). At 31-300 m from the roadside, the main sources were parent material (73.85%) and coal (26.15%). The combined Pb-Sr isotope tracing pollution sources confirm the Pb isotope analysis.