Sediment Re-Suspension and Release of Dissolved Heavy Metal Cu under Wave Actions

Abstract

Located in the semi-enclosed Bohai Sea, the Yellow River subaqueous delta faces serious pollution by the heavy metal Cu in seabed sediments and is frequently subject to storm surges which further incur sediment re-suspension or even liquefaction, and cause Cu to be released back into seawater. This study performed an indoor wave flume experiment to simulate the release of Cu into overlying water under different hydrodynamic conditions in three phases: static diffusion, seabed nonliquefaction and re-suspension, and seabed liquefaction and re-suspension. As indicated by the results, the concentration distribution of Cu in overlying water was closely related to that of suspended sediment and had consistent change trends. Sediment liquefaction clearly promoted the release of Cu into overlying water, and the dissolved Cu concentrations in the overlying water during the seabed liquefaction and re-suspension phase were 18 times those in the static diffusion phase, and 11 times those in the seabed non-liquefaction and re-suspension phase. In addition, seabed liquefaction caused Cu in sediments to diffuse towards deeper levels, and the diffusion depth of was about half of liquefaction depth.