Abstract
The effects of indigenous microbial consortium on removal of As from As-contaminated soil using an Fe(III)-reducing bacterium Shewanella putrefaciens were investigated under circumneutral pH condition. Sequential extraction of As revealed that more than 30% of As was associated with Fe(III)-(oxy)hydroxides in the soil. Bioleaching experiments were conducted anaerobically with a supply of lactate as a carbon source. The highest As removal efficiency (57.5%) was obtained when S. putrefaciens and indigenous bacterial consortium coexisted in the soil. S. putrefaciens and indigenous bacteria solely removed 30.1% and 16.4% of As from the soil, respectively. The combination of S. putrefaciens and indigenous bacteria led to a higher amount of labile As after microbial dissolution of Fe(III)-(oxy)hydroxides. After microbial treatment, soil quality represented by pH and organic content appeared to be preserved. The results indicated that the ecological and physiological understanding of the indigenous microbiome might be important for the efficient application of bioleaching technology to remove As from contaminated soils.
Highlights
Arsenic occurs in nature with four main redox states: As(-3), As(0), As(+3) and As(+5), with predominant forms of arsenate (As(+5)) as H2AsO4− and HAsO42− under aerobic and arsenite (As(+3)) as H3AsO30 and H2AsO3− under anaerobic conditions [1]
The goal of this study was to investigate the effects of indigenous bacterial consortium living in As-contaminated agricultural soil on anaerobic As bioleaching efficiency by Shewanella putrefaciens, which was artificially inoculated
As concentration of 110 mg/kg in the soil was approximately four times higher than the Korean standard (25 mg/kg) [40], which indicated that the soil was significantly contaminated with As likely due to nearby mining activity
Summary
Arsenic occurs in nature with four main redox states: As(-3), As(0), As(+3) and As(+5), with predominant forms of arsenate (As(+5)) as H2AsO4− and HAsO42− under aerobic and arsenite (As(+3)) as H3AsO30 and H2AsO3− under anaerobic conditions [1]. Arsenic can be released to the environment from anthropogenic and natural sources [6,7]. In South Korea, significant As contamination has been mainly reported in the areas around abandoned metal mines, the number of which exceeded 1000. Agricultural soils, groundwater and vegetable samples around Songchun, Dongjung, Myoungbong, Dongil, and Duckum metal mines showed high contamination levels of As and heavy metals such as Cu, Pb and Zn [9]. It was reported that the maximum of 167 μg/L of As existed in groundwater around the Gubong mine [10]
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