[Movement and transformation of heavy metals in water-sediment in water-level-fluctuating zone of Three Gorges Reservoir Area].

According to the off-season regulation model for Three Gorges Reservoir, the characteristic of movement and transformation of Cu, Pb, Cd and Cr in sediment of water-level-fluctuating zone of Three Gorge Reservoir Area was investigated. The results indicated that the chemical fraction composition characteristics of heavy metals are different. Cu mainly existed in organic/sulphidic fraction and residual fraction; Pb mainly existed in carbonates, Fe-Mn oxides and residual fraction; Cd mainly existed in carbonates and Fe-Mn oxides fraction; Cr mainly existed in residual fraction. In flood season, the exposure of sediment from river bottom to atmosphere caused the decrease of TOC, AVS and pH and increase of ORP, and lowered the amount of extractable heavy metals. Heavy metals have the tendency to release to water body. The migration rates of Cu, Pb, Cd and Cr were 30.50%, 26.10%, 33.50%, and 11.77% respectively, the migration ability of heavy metals followed: Cd > Cu > Pb > Cr. The contributions of extractable fractions of Cu, Pb, Cd and Cr to the migrated heavy metals were 77.15%, 86.09%, 94.86%, and 32.34% respectively, extractable fraction was the mainly part of the migrated heavy metals. The off-season regulation model for Three Gorges Reservoir lowered the ecological harm of heavy metals, the concentrations of Cu, Pb, Cr, Cd in the study areas were low.