Naturally occurring arsenic: Mobilization at a landfill in Maine and implications for remediation |
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| Institution: | 1. Lamont-Doherty Earth Observatory of Columbia University, 61 Route 9W, Palisades, NY 10964, USA;2. Department of Earth and Environmental Science, Columbia University, New York, NY 10027, USA;3. Department of Environmental Science, Barnard College, 3009 Broadway, New York, NY 10027, USA;1. Department of Chemistry, University of Kalyani, Kalyani 741235, West Bengal, India;2. CSIR-National Metallurgical Laboratory, Jamshedpur 831007, India;3. Jadavpur University, Kolkata 700032, India;4. Heritage Institute of Technology, Kolkata 700107, India;5. Vijaygarh Jyotish Ray College, Kolkata 700032, India;1. Institute of Geosciences, Friedrich Schiller University of Jena, Burgweg 11, 07749 Jena, Germany;2. Babe?-Bolyai University, Faculty of Chemistry and Chemical Engineering, Arany Janos Str. No. 11, RO-400028 Cluj Napoca, Romania;3. Subsurface Research Laboratory, University of Cyprus, Kallipoleos Str. 75, 1678 Nicosia, Cyprus;4. Institute of Inorganic and Analytical Chemistry, Friedrich Schiller University of Jena, Lessingstr 8, 07743 Jena, Germany;1. KHNP Central Research Institute, 1312-70 Yuseong-daero, Yuseong-gu, Daejeon 305-343, Republic of Korea;2. Department of Nuclear Engineering, Seoul National University, Seoul 151-742, Republic of Korea |
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| Abstract: | Elevated levels of dissolved arsenic (～300 μg L?1) have been detected beneath and in groundwater plumes extending away from a closed landfill in southern Maine. This study sought to determine the source of arsenic to the aquifer, the processes responsible for arsenic mobilization, and to evaluate the effectiveness of remediation efforts that have occurred at this site. The As appears to originate in the natural (glacial) aquifer solids, which contain ～5 mg kg?1 As on a dry weight basis. This conclusion is supported by the relatively uniform distribution of As in sediment samples, results of laboratory batch incubation experiments, and comparisons with groundwaters in nearby wetlands, which also have high levels of dissolved As that do not appear to originate within the landfill. The As is mobilized in the subsurface by strongly reducing conditions beneath the landfill and in nearby wetlands. In the aquifer beneath the landfill, the average oxidation–reduction potential (ORP) is ?95 mV (Eh + 105 mV), and these reducing conditions were primarily induced by landfill leachate. Remediation efforts at this site have included installation of a low permeability clay cap; groundwater extraction, oxidation, and re-injection; and subsurface oxidation by injection of magnesium peroxide. The natural source of arsenic within the aquifer solids, coupled with widespread reducing conditions, has severely limited the effectiveness of these interventions on groundwater arsenic concentrations. |
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