Efficacy of dredging engineering as a means to remove heavy metals from lake sediments.

Abstract Dredging is used worldwide to remove polluted sediments from water bodies. However, the dredging efficacy remains hard to identify. Here, we studied the efficacy of dredging engineering as a means to remove Cu, Cd, and Pb from polluted lake sediments, after six years of completion. Dissolved metals and DGT-labile metals were quantified in the non-dredged and post-dredged sediments by high-resolution dialysis (HR-Peeper) and diffusive gradients (DGT) in thin films techniques. April and July measurements showed that dredging was effectively remediate the polluted sediments. The dissolved Pb, Cd, and Cu contents decreased up to 30%, 44%, and 26%, and the DGT-labile contents decreased up to 51%, 27%, and 33% compared with the contents in the non-dredged zone. Dredging was thus proven efficient in decreasing the labile metal fractions, increasing the capacity of available solids to bind metals, and slowing the leaching of metals from available solids in the post-dredged sediments. In October and January, the dredging efficacy was counteracted by the decomposition of algae, which increased the dissolved and DGT-labile metal concentrations in the post-dredged zone. Graphical abstract Unlabelled Image Highlights • Dredging efficacy varied by season after six years of completion. • Dredging was effective in controlling heavy metals pollution in April and July. • Efficacy results from increased inert with slower kinetic response in sediments. • Dredging negligibly affected metal mobility in October and January. • Algal degradation affected dredging efficacy by releasing additional amounts of metals. [ABSTRACT FROM AUTHOR]