Evaluating the Impact of Long Term Hydrodynamic Conditions on the Release of Metals from Contaminated Sediments in Taihu Lake, China

Abstract

The effects of hydrodynamic conditions on sediment geochemistry, suspended solids, and the release of metal from metal-contaminated sediments were analyzed in a 23-day lab experiment involving two different experimental treatments (14 cm/s and 3.2 cm/s). At seven different points in time (after 0, 1, 3, 6, 10, 16, and 23 days) the sediment and water physical-chemical conditions and the amount of metal released into the surface water were determined. The amounts of filterable metals in the surface water increased by a factor of 21 and 4.1 (Cd), 10 and 1.7 (Pb), 13 and 1.8 (Cu), 3.6 and 1.7 (Cr), 3.7 and 1.5 (Ni), 11 and 4.7 (Fe), and 7.2 and 0.12 (Mn) times in the 14 cm/s and 3.2 cm/s treatments, respectively, after 23 days. Cr was the metal that bound most strongly to suspended solids, and Cd was the most readily released into the surface water. The metal equilibrium between dissolved and solid states was reached approximately 10 days after the experiment began. Pb required the longest time to reach equilibrium, whereas Cu required the least. Mn was the most easily affected by the hydrodynamic conditions. Results indicated that hydrodynamic conditions can dramatically enhance the mobility of metals, which may result in the release of sediment-bound metals to the surface water, and different metals show different characteristics during the release.

Keywords: metal release, hydrodynamic conditions, sediment, metal characteristics, suspended solids