Spatial distribution, source apportionment and potential ecological risk assessment of trace metals in surface soils in the upstream region of the Guanzhong Basin, China.

The health of ecosystems and safety of agricultural products are correlated with trace metal pollutionin in the soil, which eventually affects mankind. For this research, topsoil (0-20 cm) was sampled from 51 locations in the upstream area of the Guanzhong Basin to determine the level of pollution, spatial distribution characteristics and origins of 15 trace metals (V, Cr, Mn, Fe, Ni, Cu, Zn, As, Se, Rb, Sr, Y, Zr, Cd, Pb). The pollution index and potential ecological risk index were adopted for the accurate analyses of contamination degree and ecological risk that trace elements cause. The identification of potential sources of trace metals pollution was carried out using the APCS-MLR model and multivariate statistical analysis. Findings demonstrated that the most contaminated elements in the topsoil of the designated areas were Cr, Cu, Cd and Pb, and the average levels of all trace metal elements exceeded their respective local background values. However, most of the sampling points showed slight pollution, and a few demonstrated moderate and severe pollution. The southern, south-western and eastern parts in the research zone were relatively seriously contaminated, especially near Baoji City and Wugong County. Fe, Cu, Zn, Ni, Se were mainly caused by combination of agricultural and industrial production, the primary sources of Mn, Y, and Zr were the process of mining and industrial production, Cd and Pb originated mainly from traffic emission and agricultural pollution, and Cr mainly came from mining and metal smelting processes. Meanwhlie, some unknown pollution sources were also disclosed. This study has a reliable reference value for determining the source of trace metals in this region. To further determine the pollution sources of trace elements, long-term monitoring and management is necessary.