Mechanism of arsenic release to groundwater, Bangladesh and West Bengal

In some areas of Bangladesh and West Bengal, concentrations of As in groundwater exceed guide concentrations, set internationally and nationally at 10 to 50 μg l −1 and may reach levels in the mg l −1 range. The As derives from reductive dissolution of Fe oxyhydroxide and release of its sorbed As. T...

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Bibliographic Details
Published in:Applied geochemistry 2000-05, Vol.15 (4), p.403-413
Main Authors: Nickson, R.T., McArthur, J.M., Ravenscroft, P., Burgess, W.G., Ahmed, K.M.
Format: Article
Language:English
Subjects:
Bangladesh
Earth sciences
Earth, ocean, space
Engineering and environment geology. Geothermics
Exact sciences and technology
Freshwater
Hydrology. Hydrogeology
India
India, West Bengal
Pollution, environment geology
Water resources
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Summary:In some areas of Bangladesh and West Bengal, concentrations of As in groundwater exceed guide concentrations, set internationally and nationally at 10 to 50 μg l −1 and may reach levels in the mg l −1 range. The As derives from reductive dissolution of Fe oxyhydroxide and release of its sorbed As. The Fe oxyhydroxide exists in the aquifer as dispersed phases, such as coatings on sedimentary grains. Recalculated to pure FeOOH, As concentrations in this phase reach 517 ppm. Reduction of the Fe is driven by microbial metabolism of sedimentary organic matter, which is present in concentrations as high as 6% C. Arsenic released by oxidation of pyrite, as water levels are drawn down and air enters the aquifer, contributes negligibly to the problem of As pollution. Identification of the mechanism of As release to groundwater helps to provide a framework to guide the placement of new water wells so that they will have acceptable concentrations of As.
ISSN:0883-2927
1872-9134
DOI:10.1016/S0883-2927(99)00086-4