Evaluation of the Use of Sea Sand, Crushed Concrete, and Bentonite to Stabilize Trace Metals and to Interrupt Their Release from Contaminated Marine Sediments

Abstract

The aim of this study is to assess the effectiveness of sea sand (SS), crushed concrete (CC), and bentonite (BN) as a capping material to block the release of trace metals (As, Cd, Cr, Cu, Ni, Pb, and Zn) from heavily contaminated marine sediments, and to stabilize/solidify these trace metals in the sediments. The efficiency of SS, CC, and BN for blocking trace metals was evaluated in a flat flow tank in which a 1-cm-thick layer of capping materials was placed above the contaminated sediments. Trace metals were released into the overlying water from contaminated sediments in the following decreasing order: Cd > As > Zn > Ni > Pb > Cr > Cu. Electronegativity, electrostatic force, or metal hydrolysis significantly influenced the mobility of trace metals in sediments. The elution of Cu, Ni, and Cd from contaminated sediments was effectively reduced by CC, especially in case of Cd elution. SS was appropriate for interrupting Cr and Zn release, and BN was appropriate for interrupting Pb release. A sequential extraction study demonstrated that SS capping is appropriate for stabilizing As, Cu, and Ni; CC capping for Zn; and BN capping for Pb. SS, CC, and BN can be applied effectively for remediating the contaminated sediments.