[Evaluation and Source of Heavy Metal Pollution in Surface Soil of Qinghai-Tibet Plateau].

Spatial distribution and source apportionment of heavy metals in the surface soil of the Qinghai-Tibet Plateau was investigated to gain an understanding of the pollution characteristics. The surface soil (0-20 cm) samples were collected from the northeast to the southwest in the study area. The total amount of 13 heavy metals (Ba, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Sb, Sc, and Zn) was determined. The potential sources of heavy metals were preliminarily apportioned and identified by the principal component analysis-absolute principal component score-multiple linear regression (PCA-APCS-MLR) receptor model. Results show that the average contents of Cd and Sb significantly exceed the environment standard, and they were 2.13 and 1.52 higher than the soil background values of the Qinghai-Tibet Plateau in the 1970s, respectively. The enrichment factor (EF), geo-accumulation index (), and Nemero synthesis index (PN) were used to evaluate the surface soil heavy metal contamination, which indicated that Cd and Sb also were pollutants in the Qinghai-Tibet Plateau with a limited pollution level. Various levels of pollution were presented at the central, southeastern, and northeastern regions of the Qinghai-Tibet Plateau, while the central and southeastern areas exhibited relatively severe pollution levels. The PCA-APCS-MLR levels revealed that three main sources of heavy metals in the soil of the Qinghai-Tibet Plateau were the natural source, traffic activities, and the mining industry, in that order. Cobalt, Cr, Cu, Fe, Mn, Ni, and Sc, were largely affected by natural sources, while Ba, Cd, Mo, and Pb were mainly affected by traffic activities. Specifically, Zn gave priority to natural and traffic sources, and Sb was jointly affected by natural sources, traffic activities, and the mining industry. Therefore, Sb and Cd pollution from traffic activities and the mining industry should be noted in control plans for the heavy metal pollution in soil of the Qinghai-Tibet Plateau.