Kinetics release of heavy metal Cu from sediment affected by the mimic vegetation under unidirectional flows and regular waves

Abstract

The process of heavy metal contamination in wetlands is becoming increasingly prevalent due to rapid urbanization. Heavy metals deposited in the sediment can be re-released into the water under disturbances, leading to significant impacts on the water environment and ecosystem. The release of heavy metals in wetlands is a complex phenomenon involving the intricate interplay of physicochemical and biological mechanisms. To gain insights into the adsorption-desorption processes of Cu under the influence of hydro-sediment dynamics, indoor experiments were conducted in this study, considering the presence of mimic vegetation at a short-term scale. The biological processes were not explicitly considered in these experiments. To analyze the kinetic processes of heavy metal migration at the water-sediment interface influenced by mimic vegetation under different hydrodynamic conditions, several equations were utilized, including the pseudo-second-order kinetic equation, double constant rate equation, Elovich equation, and parabolic diffusion equation. The pseudo-second-order kinetic equation can best simulate the Cu release process, with R2 ranging from 0.98 to 0.99. In order to enhance the accuracy of our predictions, the stem-Reynolds number (Red) is introduced into the original pseudo-second-order kinetic equation to account for the influence of mimic vegetation on the release of heavy metals. As a result of this improvement, the release processes of Cu were better predicted using the updated equations. The error between the improved equation and the actual measured value is reduced to less than 10 %. These improved methods are suitable for both unidirectional flow and wave conditions affected by mimic vegetation, and they offer vital parameters for numerical simulations of heavy metal transport in riverine or coastal wetlands. This research contributes to a better understanding of the complex processes governing heavy metal dynamics in wetland environments and provides valuable insights for effective environmental management and protection.