Reservoir sediment records of polymetallic contamination (Cd, Pb, Zn, As, Hg) in the zinc smelting area of Weining County, Guizhou Province, China

The sedimentation rate (dated by 210Pb), sediment characteristics, pollution, and polymetallic (Cd, Pb, Zn, As, Hg) sediment record were studied from two reservoirs (Maoshui Reservoir and Lexi Reservoir), which are located in the zinc smelting area of Weining County, Guizhou Province, China. The results showed that the Maoshui reservoir is mainly polluted by Cd, Pb, and Zn, with average concentrations of 53, 84, and 2108 mg/kg, respectively. While the mean concentrations of Cd, Pb, and Zn in the sediments of the Lexi reservoir are relatively low, which are 18, 196, and 553 mg/kg, respectively. The high concentrations of heavy metals in the sediment reflected the regional environmental pollution caused by indigenous zinc smelting. The scale of indigenous zinc smelting can be inferred from the concentration and ratio of elements in the sedimentary column. Therefore, it was confirmed that the peak of indigenous zinc smelting mainly occurred in the Maoshui area in the 1980s–1990s, while the zinc smelting activity expanded at the turn of the twenty-first century, and there were peaks in the indigenous zinc smelting activity in both the Maoshui basin and the Lexi basin. In the middle part of the sediment column of the Maoshui Reservoir (1990s), the sediment column had a high Pb concentration and a high Zn/Cd ratio, which represented the mixing of zinc smelting slag in this period. In the upper part of the sedimentary column of the Lexi Reservoir (after 2000), the sediment had a high concentration of Cd (18 mg/kg) and a low Zn/Cd ratio, which indicated that after the end of indigenous zinc smelting, the polluted soil continued to affect the regional environment. These results show that the sedimentary column of the reservoir in the area of indigenous zinc smelting completely recorded the history of regional zinc smelting activities and can be used to reconstruct the history of regional indigenous zinc smelting and its impact on the regional environment.