Spatial Distribution and Source Analysis of Heavy Metals in Sediments of the Upstream Xijiang Basin within Nonferrous Metal Accumulation Areas

This study aimed to investigate how the development of the non-ferrous metals industry impacted sediment deposition in the upstream Xijiang Basin. Twelve sampling sites were selected on four tributaries in the upstream Xijiang Basin, namely, Diaojiang River, Longjiang River, Rongjiang River, and Liujiang River. Contents of Cu, Zn, Pb, Cd, As, Cr, Ni, Tl, Sb and Hg in sediments were measured in the twelve sampling sites, then correlation, clustering, and lead isotope tracing analyses were used to evaluate the distribution and sources of the measured heavy metals in sediments. The results showed that: (1) the average contents of As, Pb, Cd, Ni, Zn, Cu, Tl, Hg, Sb and Cr in sediments were 95.42, 113.09, 4.92, 28.03, 416.51, 27.07, 0.75, 0.31, 34.02 and 57.58 mg/kg, respectively. The river sediments have been seriously polluted by Cd, As, Zn and Pb, moderately polluted by Hg and Sb, and slightly polluted by Cr, Ni, Cu and Tl. (2) From a spatial perspective, the order of pollution degrees of sediments in the four tributaries was Diaojiang, Longjiang, Rongjinag, and Liujiang. (3) Regarding the source of contamination, As, Pb, Cd, Zn, Cu and Sb in the sediments were related to the mineral exploitation of nonferrous metal accumulation areas in the upstream Xijiang Basin. Ni, Tl, Hg and Cr in sediments mainly came from the natural geological background. The range of Pb/Pb ratio was 1.08 to 1.19 in the sediments. The order of similarity between lead isotope ratio in the sediments of the four tributaries and ore of Dachang and Chehe was Diaojiang, Longjiang, Rongjiang, and Liujiang. Lead isotope tracing analysis further revealed that heavy metals in the sediments of Diaojiang and Longjiang Rivers originated from non-ferrous mining and smelting activities, and those in Rongjiang and Liujiang Rivers were mainly contributed by the geological background in the sites.