Environmental assessment of heavy metal transport and transformation in the Hangzhou Bay, China

The environmental impact of heavy metal (Cu, Cd, Zn, Pb, Ni, Sr-90 and Cs-137) transport and transformation in the Hangzhou Bay (China) was assessed through a comprehensive model that integrates hydrodynamics, sediment and heavy metal transport. A mechanistic surface complexation model was used to estimate the adsorption and desorption of heavy metal by suspended sediment under different aqueous chemistry conditions. The dynamics of metal exchange to and from the seabed was also assessed. The primary processes regulating heavy metal distribution, i.e., convection-diffusion, adsorption-desorption, sedimentation-resuspension, as well as other physical and chemical processes related to mass exchange between adjacent sediment layers, were considered in detail. The accidental discharge of Cs-137 was simulated as an example and results showed that Cs-137 transported along the coast driven by tidal flow. Most Cs-137 distributed near the outfall and accumulated in the seabed sediment. The proposed model can be a useful tool for predicting heavy metal transport and fate and provide a theoretical basis to guide field sampling, assessment of risks and the design of remediation strategies. (C) 2015 Elsevier B.V. All rights reserved.