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Membrane Water Treatment
  Volume 11, Number 1, Janaury25 2020, pages 11-23

The application of DGTs for assessing the effectiveness of in situ management of Hg and heavy metal contaminated sediment
Mark Xavier Bailon, Minoh Park, Young-Gyun Choi, Danny Reible, and Yongseok Hong

    The effectiveness of in situ sediment capping as a technique for heavy metal risk mitigation in Hyeongsan River estuary, South Korea was studied. Sites in the estuary were found previously to show moderate to high levels of contamination of mercury, methylmercury and other heavy metals. A 400 m x 50 m section of the river was selected for a thin layer capping demonstration, where the total area was divided into 4 sections capped with different combinations of capping materials (zeolite, AC/zeolite, AC/sand, zeolite/sand). Pore water concentrations in the different sites were studied using diffusive gradient in thin film (DGT) probes. All capping amendments showed reduction in the pore water concentration of the different heavy metals with top 5 cm showing %reduction greater than 90% for some heavy metals. The relative maxima for the different metals were found to be translated to lower depths with addition of the caps. For two-layered cap with AC, order of placement should be considered since AC can easily be displaced due to its relatively low density. Investigation of methylmercury (MeHg) in the site showed that MeHg and %MeHg in pore water corresponds well with maxima for sulfide, Fe and Mn suggesting mercury methylation as probably coupled with sulfate, Fe and Mn reduction in sediments. Our results showed that thin-layer capping of active sorbents AC and zeolite, in combination with passive sand caps, are potential remediation strategy for sediments contaminated with heavy metals.
Key Words
    Diffusive Gradient in Thin Film (DGT), sediment, mercury, heavy metal, capping
1Department of Environmental Systems Engineering, Korea University, Sejong City, Republic of Korea
2 Department of Environmental Engineering, Chungnam National University, Daejeon City, Republic of Korea
3 Department of Civil, Environmental, and Construction Engineering, Texas Tech University, Lubbock, Texas, USA

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