Water environment in the Tibetan Plateau: heavy metal distribution analysis of surface sediments in the Yarlung Tsangpo River Basin

To fully understand the environmental quality of sediments in the Yarlung Tsangpo River Basin, surface sediments of the main stream of the Yarlung Tsangpo River and its five major tributaries were studied. In 2016, a total of 201 water samples from the Yarlung Tsangpo River and its tributaries were collected during three water seasons. Fifteen trace elements (including Cd and heavy metals such as Cr, Cu, Pb, and As), which have great environmental effects, were analyzed. The results showed that Ti, Mn, and Cr were the main heavy metals in Yarlung Tsangpo River sediments, accounting for 51%, 10%, and 7% of the total heavy metals, respectively. There were no significant differences among the heavy metal contents in the sediments of Yarlung Tsangpo River among three water seasons, but there were significant spatial variations. During the same period, the concentration of each element in the tributary sediments was generally higher than that in the main stream. According to three different ecological risk assessment models, it is calculated that the heavy metal elements in the surface sediments of the river basin are at low or no pollution risk.