Multivariate statistical analysis and risk assessment of dissolved trace metal (loid)s in the cascade-dammed Lancang River

As a prominent factor impacting water quality, the dissolved trace metal(loid) (DTM) has not been adequately studied in the Lancang River Basin (LRB). Herein, we sampled surface water from 46 sites in the LRB to explore the spatial distribution, primary sources, and associated human health risks of 18 DTMs (As, Ba, Cd, Co, Cr, Cs, Cu, Li, Mo, Ni, Pb, Rb, Sb, Sr, Tl, U, V, and Zn). Affected by geothermal spring input, the concentrations of As, Cs, Li, Mo, Sr, and U were significantly higher in the mainstream than those in tributaries, with a decreasing trend along the flow direction in the mainstream of the LRB. Tl and Rb are mainly related to naturally derived sources, like soil erosion, Cd, Cr, Cu, Pb, and Zn were mainly attributed to anthropogenic processes, Co and Ni were affected by both natural and anthropogenic processes, while Sb was mainly from the Sb deposit in the basin. As a result of the combined influence of multiple sources of pollution, the spatial distribution of these elements does not seem to be regular. Most of the DTM concentrations in the LRB were within the Chinese and WHO drinking water guideline values, while 43.5% of the samples contained arsenic exceeding the guideline value of 10 mu g/L. In general, the water quality of the LRB was good. Health risk assessment indicated that As, Sb, and Tl were the primary drivers of the non-carcinogenic risk. These results give the scientific basis needed for metal(loid) cycling in the aquatic environment and the ecological management of the LRB.