Abstract
Arsenic (As) can be naturally present in the native aquifer materials and can be released to groundwater through reduction dissolution of iron oxides containing As. While granular iron permeable reactive barriers (PRBs) can be effective for the treatment of arsenic in groundwater, the mobilization of arsenic in the sediment downgradient of the PRB might be an issue due to the reduced geochemical conditions generated by reactions in the PRB. The release of arsenic in the sediment downgradient from a proposed iron PRB was studied through laboratory column experiments and reactive transport modeling. The laboratory column experiments showed a significant removal of arsenic from the groundwater by granular iron (from the influent concentration of about 0.7 mg L−1 to less than 0.006 mg L−1 at the effluent); however, arsenic can be flushed out from the aquifer sediments (up to 0.09 mg L−1). The reactive transport modeling based on the geochemical reactions as suggested from the experiments, i.e., reductive dissolution of As-bearing goethite, was successful to reproduce the observed geochemical trends in the column experiments. This study can provide implications regarding the installation of iron PRBs to treat arsenic in groundwater and also be useful to understand geochemical behavior of arsenic under reduced conditions.
Highlights
Arsenic is naturally present in a variety of rocks and minerals, including sulfides, oxides, and hydroxides [1,2]
This study evaluated the potential release of arsenic in a sediment downgradient of a proposed iron permeable reactive barriers (PRBs) to treat groundwater that is contaminated with arsenic
The influent groundwater contained around 0.7 mg L−1 arsenic
Summary
Arsenic is naturally present in a variety of rocks and minerals, including sulfides, oxides, and hydroxides [1,2]. Mineral deposits that are associated with gold (e.g., pyrite and arsenopyrite) and sedimentary rocks (e.g., marine shales) are sources of arsenic in groundwater [3,4]. Arsenic contamination of groundwater water is identified in many countries, such as Bangladesh [5,6], China [7], and Nepal [8]. Acute and chronic effects from arsenic exposure include several cancers (e.g., skin, lung, liver, bladder, etc.), skin disorders (e.g., melanosis and keratosis), cardiovascular disease, diabetes, and reproductive effects [9,10]. Arsenic is released through sulfide mineral oxidation (e.g., arseno-rich pyrite, arsenopyrite), desorption (increase in pH), and reductive dissolution of arsenic-bearing Fe(III) and Mn(IV)
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