A simulation study of mercury immobilization in estuary sediment microcosm by activated carbon/clay-based thin-layer capping under artificial flow and turbation

Yu Ting; Boon-Lek Ch'ng; Chi Chen; Meng-Yuan Ou; Yung-Hua Cheng; Che-Jung Hsu; Hsing-Cheng Hsi

doi:10.1016/j.scitotenv.2019.135068

A simulation study of mercury immobilization in estuary sediment microcosm by activated carbon/clay-based thin-layer capping under artificial flow and turbation

Sci Total Environ. 2020 Mar 15:708:135068. doi: 10.1016/j.scitotenv.2019.135068. Epub 2019 Nov 20.

Authors

Yu Ting¹, Boon-Lek Ch'ng¹, Chi Chen¹, Meng-Yuan Ou¹, Yung-Hua Cheng¹, Che-Jung Hsu¹, Hsing-Cheng Hsi²

Affiliations

¹ Graduate Institute of Environmental Engineering, National Taiwan University, No. 1, Sec. 4, Roosevelt Rd., Taipei 106, Taiwan.
² Graduate Institute of Environmental Engineering, National Taiwan University, No. 1, Sec. 4, Roosevelt Rd., Taipei 106, Taiwan. Electronic address: hchsi@ntu.edu.tw.

PMID: 31780157
DOI: 10.1016/j.scitotenv.2019.135068

Abstract

In-situ thin layer capping (TLC) is a promising sediment remediation approach that has been shown effective in immobilizing contaminants from releasing to natural biotas and human beings. This research intended to comprehend the effectiveness of Hg immobilization by TLC under turbation condition via a microcosm study. Three TLC caps with different activated carbon (AC)/clay combinations were applied to actual Hg-contaminated estuary sediment (76.0 ± 2.6 mg-Hg/kg). The caps with AC (3%) + bentonite (3%) and AC (3%) + kaolin (3%) were efficient in reducing both total mercury (THg) and methylmercury (MeHg) concentrations in overlying water by 75-95% and 64-98%, respectively, in the later stage of 75-d operation. In contrast, the AC (3%) + montmorillonite (3%) cap did not show a significant reduction on THg and MeHg in the overlying water, probably due to the unstable, suspension property of montmorillonite. The stable caps showed higher resistance to Hg breakthrough under occasional turbation events; however, a labile cap appeared to have dramatic Hg breakthrough when turbation occurred. It is therefore essential to note that with unstable caps, turbation events may result in unwanted secondary resuspension of contaminants.

Keywords: Mercury; Methylmercury; Sediment turbation; Thin layer capping.