Naturally occurring arsenic: Mobilization at a landfill in Maine and implications for remediation

LDEO Publication: 
Publication Type  Journal Article
Year of Publication  2005
Authors  Keimowitz, A. R.; Simpson, H. J.; Stute, M.; Datta, S.; Chillrud, S. N.; Ross, J.; Tsang, M.
Journal Title  Applied Geochemistry
Volume  20
Issue  11
Pages  1985-2002
Journal Date  Nov
ISBN Number  0883-2927
Accession Number  ISI:000233065600001
LDEO Publication Number  6683
Key Words  pollution plume vejen; bangladesh groundwater; organic-chemicals; redox zones; sediments; denmark; health; mobility; aquifer; water

Elevated levels of dissolved arsenic (similar to 300 mu g 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 are 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. (c) 2005 Elsevier Ltd. All rights reserved.


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URL  <Go to ISI>://000233065600001
DOI  DOI 10.1016/j.apgeochem.2005.06.008