Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
8851679 | Chemosphere | 2018 | 43 Pages |
Abstract
Utilization of bacterial volatilization can be problematic to remediate mercury (Hg)-contaminated soils because most of the Hg in soils is bound to soil particles. The objective of this study was to develop a two-stage system (chemical extraction followed by microbial reduction) for Hg-contaminated soil remediation. The tasks were to (1) select the extraction reagents for Hg extraction, (2) assess the effects of extraction reagents on the growth of Hg-reducing bacterial strains, and (3) evaluate the effectiveness of Ca2+ and Mg2+ addition on merA gene (Hg reductase) induction. Bacterial inhibition was observed with the addition of 0.1â¯M ethylenediaminetetraacetic acid or citric acid. Up to 65% of Hg was biotransformed (Hg concentrationâ¯=â¯69â¯mg/kg) from the soils after a 24â¯h extraction using 0.5â¯M ammonium thiosulfate. Ca2+ and Mg2+ were selected because they have the same electric charge as Hg and the studied groundwater contained high concentrations of Ca2+ and Mg2+. Results showed that the addition of 200â¯mg/L Ca2+ or 650â¯mg/L Mg2+ could reach effective merA induction. In the two-stage experiment, 120â¯mg/kg Hg-contaminated soils were extracted with 2 rounds of extraction processes for 10â¯h using 0.5â¯M ammonium thiosulfate. Approximately 77% of Hg was extracted from the soils after the first-step extraction process. Up to 81% of Hg2+ was transformed from the washing solution via the biotransformation processes with Enterobacter cloacae addition and Ca2+ and Mg2+ supplementation. The two-stage remedial system has the potential to be developed into a practical technology to remediate Hg-contaminated sites.
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Authors
S.C. Chen, W.H. Lin, C.C. Chien, D.C.W. Tsang, C.M. Kao,