Evaluation of sediment capping using zeolite, montmorillonite, and steel slag to immobilize heavy metals

摘要

Capping contaminated sediments is an in situ remediation technique by placing capping material on top of the sediments to prevent continued contamination of surface water and biota from contaminated sediments. Capping is considered as much cheaper than dredging and is expected to be very effective to block the diffusion of contaminants in short-term. The research on capping material for controlling the contaminants has been conducted and different capping materials used for each contaminants. Laboratory experiments in a flat flow tank were performed to evaluate the effect of capping materials on heavy metals. The results showed that all capping materials used this study were not effective in interrupting release of As and higher As concentrations in capped condition were observed than uncapped condition. Zeolite had negative effect on the block of Cr release but Cr was significantly reduced by 5 cm of steel slag capping. In contrast to As and Cr, the release of Cd, Ni, and Pb was not observed in all cases including uncapped sediments. Cu and Zn were the heavy metals, which were most significantly influenced by the capping conditions. Cu release from the marine sediments were effectively blocked by capping materials, whereas Cu concentration in uncapped condition were above the Cu criteria concentration during the experimental run. All capping materials were also found to be effective in interrupting release of Zn from the marine sediments. It was concluded that the zeolite, montmorillonite, and steel slag could be used as a potential capping material for interrupting the release of Cd, Cu, Ni, Pb and Zn from the contaminated marine sediments.