With the change in global climate and environment, water scarcity has been of great concern around the word and exacerbated by serious pollution in water resources. Pollutants accumulated in sediments are threatening water safety and ecological security. Different from others focusing on prevalent heavy metals (Cu, Pb, Zn, As, Cd, Cr, Hg, etc.), in this study, some unheeded metal pollutants Tl, Sb, Mo, Sr, Co, V, Ti, Ca, Mg, Be and Li were monitored in sediments of the Xiangjiang River, China. It was found that there was no remarkable vertical variation with depth, but the seasonal characteristics of Tl, Sb, Mo, Be and Li. The enrichment, pollution and potential ecological risk of Tl, Sb and Mo were revealed by the enrichment factor (EF), geoaccumulation index (Igeo), pollution load index (PLIsite and PLIzone) and potential ecological risk index (RI). It is noticed that the pollution of Tl mainly occurred in summer at midstream and downstream and Mo pollution was much higher than Sb in summer and the reverse in other seasons. Additionally, sediment quality on east side was worse than on west side in Songbai section of the Xiangjiang River. For the first time, the toxic-response factor was figured out as Mo = 18, Tl = 17, Sb = 13, Sr = 6, Co = Be = 1, V = Li = 0, and importantly, the high potential ecological risk of Tl, Sb and Mo needs to be taken seriously for the comprehensive assessment on watershed environmental quality.
Keywords: Ecological risk; Metal pollution; Sediment; Toxic-response factor.