Ecological risk, dynamics in fingerprinting, and source apportionment of heavy metals in soils from plateau in Upper Yellow River, Qinghai Province, China

Purpose Beichuan River is a primary tributary of Huangshui River and a secondary tributary of Yellow River. However, the soil in the watershed has been polluted due to decades of agricultural and urbanization development. Effective pollution investigation and source control of the Beichuan River basin is the key to soil conservation. In this study, the spatial distribution and physical and chemical properties of potentially toxic metals (PTMs) in soil of Beichuan River basin were studied for the potential ecological risks and source apportionment. The results can provide guidance for the environmental protection of Beichuan River and can also provide technical support for the contamination of similar river basins. Materials and methods The contents and ecological risk of nine PTMs (Cr, Hg, As, Pb, Ni, Cd, Co, Cu, and Zn) in 37 surface soil samples were investigated with several evaluation methods (geo-accumulation index, potential ecological risk index, and toxic risk index). The fraction species of soil samples were treated by Tessier sequential extraction. The potential sources of the nine PTMs were explored with a combination of Pearson’s correlation coefficient, geostatistics, and source analysis method. Results and discussion Four potential contamination source were identified in the study area: (1) industrial source of chemical industry and smelting industry related to coal combustion; (2) traffic emission and atmosphere deposition; (3) agricultural activities, which included fertilizers, pesticides and livestock manure; and (4) the natural source. The source apportionment indicated that the non-point source contamination in agriculture has an obvious influence on the PTMs in the Basin. The risk assessment demonstrated that the Cd and Cr were the heavy metal with serious pollution. The fingerprinting of the PTMs and physicochemical property in soil can be analyzed to two cluster, with the different physical and chemical properties and the contamination. Conclusions The risk assessment results and the source apportionment indicated that PTM contamination occurred in the southeast and northwest of the study region. The results can help distinguish the sources of the contamination, which will achieve the regional contamination control and ecological protection of soil in extreme weather areas of the plateau. Meanwhile, this study has a guiding significance for the high-quality development of the Yellow River.