[Pollution Assessment and Source Apportionment of Heavy Metals in Soil of the Xining Basin]

To comprehensively understand the status of heavy metal contamination in the topsoil of the Xining Basin in Qinghai Province, China, 2 396 samples of soil were analyzed for pH and eight heavy metals （Cd, Hg, As, Pb, Cr, Cu, Ni, and Zn）. This assessment evaluated the pollution levels and traced the origins of contamination using the geo-accumulation index, pollution load index, and potential ecological risk index methods. Spatial distribution characteristics of soil heavy metals were analyzed using inverse distance weighting interpolation, while correlation analysis, principal component analysis, and PMF models were utilized to identify the sources of pollution. The findings revealed： ① The average values of soil Cd, Hg, As, Pb, Cr, Cu, Ni, and Zn in the study area were 0.21, 0.034, 13.1, 23.5, 75.8, 25.5, 31.9, and 72.2 mg·kg^-1. Compared with the whole area of Qinghai Province, the soil Hg in the study area showed high accumulation, and Cd showed moderate accumulation. ② In the study area, two points （0.1%） exceeded the soil pollution risk control value, and 49 points （1.6%） exceeded the soil pollution risk screening value. The risk indicators were mainly As, Cd, and Cr, and the overall soil condition was good. ③ From a regional point of view, the comprehensive ecological risk in the study area was low. Locally, Hg and Cd were the main pollution risk factors, among which the potential ecological risk of Hg was the largest, followed by that of Cd. ④ Correlation analysis showed that there were two groups of element combination sequences of Cd-Pb-Zn and Cu-Cr-Ni in the study area, and the elements in each sequence had homology. Hg was independent exogenous. ⑤ Source analysis showed that there were three different types of sources of heavy metals in the study area. Factor one was a composite source of natural and industrial emissions, Factor two was a natural source, and Factor three was a source of industrial and transportation emissions. In view of the above conclusions, it is suggested to strengthen the monitoring of natural sources and the blocking of human activity sources, so as to provide a scientific basis for the protection and restoration of the ecological environment of the Qinghai-Tibet Plateau.