再悬浮作用下长江口近岸沉积物中Cd、Pb和Cr的迁移与释放

利用PES（particle entrainment simulator）模拟装置,实验测定了不同的扰动强度和时间对长江口沉积物中Cd、Pb和Cr再悬浮释放和迁移的影响.在再悬浮过程中,上覆水中溶解态Cd、Pb和Cr的质量浓度分别在0.015～0.157、0.013～0.890和0.066～1.468μg.L-1之间变...

Transport and Release of Cd, Pb and Cr from the Yangtze Estuarine Sediments During Sediment Resuspension Event

The effects of resuspension energy and duration on release and transport of sediment bound Cd, Pb and Cr in the southern coastal areas of Yangtze Estuary were analyzed experimentally using a particle entrainment simulator (PES). In the sediment resuspension experiment, concentrations of dissolved Cd, Pb and Cr in the overlying water were 0.015-0.157, 0.013-0.890 and 0.066-1.468 microg x L(-1) respectively, and concentrations of particulate Cd, Pb and Cr varied between 0.37-5.40, 8.3-137.1 and 31.6-557.7 microg x g(-1) respectively. Before the biofilm in column surface was not damaged by disturbance, a large number of Cd adsorption to biofilm was released to the overlying water during the resuspension, but after part of the biofilm was damaged with the enhanced disturbance energy, Pb and Cr were released from the sediments to overlying water in short-term. Intensity of physical disturbance was the main factor that influenced the variation of particulate heavy metal concentrations. Results of resuspension fluxes showed that Cd, Pb and Cr released to the water by resuspension were then re-adsorption to suspended particles, and gradually deposited in the bottom sediments when the hydrodynamic conditions weakened, which had less harm to the aquatic ecosystems of Yangtze Estuary. The resuspension process of Cd, Pb and Cr mainly includes the following migration and transformation process: adsorptions of heavy metals in biofilm, direct release and diffusion of dissolved heavy metals from pore water, oxidative release of sulfide associated metals in sediments, re-adsorption of heavy metals to suspended particles in overlying water and deposition of particulate heavy metals.