Review on Geochemical Characteristics and the Ecological Risk of Heavy Metals in the Sedimentary Environment

Studies on the geochemical behavior of heavy metals in sediments are of great significance for the revelation of the evolvement mechanism of water environment and the evaluation and protection of aquatic ecological environment. During using different assessment methods to do ecological risk assessment of heavy metals,it is often found that inconsistencies or even contradictory come out. Some most commonly used evaluation methods were chosen to be introduced in details. The reasons why there are large differences among evaluation results by different risk assessment indices as well as the limitations of novel methods based on acid-volatile sulfide acid/simultaneously extracted metals were mainly explained. Finally,some suggestions were put forward on the development direction of the pollution and ecological risk assessment methods of heavy metals. The main mechanisms which influence the migration behaviors of heavy metals between sediments and the overlying waters such as adsorption,precipitation,coordination and oxidation-reduction,and geochemical forms of heavy metals in sediment were introduced in details.