Distribution characteristics, risk assessment, and source analysis of heavy metals in surface sediments and near-lakeshore soils of a plateau lake in China

Lakes in Tibet play an important role in regulating regional climatic conditions and maintaining ecological balance. Evaluating the distribution characteristics, ecological risk, and source of heavy metals in surface sediments and soil near the lakeshore is important for protecting the water and soil resources of Ranwu Lake. Fourteen sample sets of surface sediment and corresponding near-lakeshore soils were collected and analyzed by inductively coupled plasma mass spectrometry to examine seven heavy metals: As, Cd, Co, Ni, Zn, Cr, and Pb. Descriptive statistical analyses show that the heavy metal content is higher in the soil than in the sediment. The geo-accumulation and pollution load indices both indicate relatively heavy Cd and As pollution within the study area. This was corroborated by the results of the potential ecological risk index. The PCA-APCS-MLR receptor model was used to analyze the potential sources of the heavy metals. The two main sources of heavy metals in sediments and soils were natural and anthropogenic sources such as vehicle emissions, long distance atmospheric transport, and geothermal and mining activities. The Cr, Co, and Ni contents in the sediment samples and the As, Cr, Co, and Ni contents in the soil samples were mainly affected by natural factors. The As and Zn contents in the sediment samples were affected by both natural and anthropogenic factors, whereas the Cd and Pb contents were mainly affected by anthropogenic activities. The results of correlation analysis of the heavy metals in the sediment and soil samples are consistent with the source analysis results of the PCA-APCS-MLR receptor model.