The Impact of Cascade Large Deep Reservoir on the Migration and Deposition of Cadmium in Lancang River

Abstract

Metal pollution is a global environmental problem. In order to understand the effects of the cascade hydropower development on Cd in reservoir sediments, this study investigated the migration and deposition mechanisms of Cd in reservoir sediments by using the film diffusion gradient technique (DGT) for the cascade large deep reservoirs of the Lancang River (LCR), Nuozhadu (NZD) and Xiaowan (XW). The results show that: (1) Strong correlations amongst the deposition processes of Cd, Mn and S were found in the sediments of the NZD reservoir; weak correlations between the deposition processes of Cd and Mn were found in the sediments of the XW reservoir. (2) Part of labile Cd in the pore water of the NZD reservoir was supplemented by silt and sand, and another part was inherent in the pore water; most of labile Cd in the pore water of the XW reservoir was inherent in the pore water, and minimal replenishment of sediment was noted. (3) Mn is the main factor controlling the migration of Cd in the NZD reservoir. This paper provides an effective resource for understanding the migration and deposition of Cd in the sediments of large deep reservoirs along the LCR.