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Role of metal-reducing bacteria in arsenic release from Bengal delta sediments


The contamination of ground waters, abstracted for drinking and irrigation, by sediment-derived arsenic threatens the health of tens of millions of people worldwide, most notably in Bangladesh and West Bengal1,2,3. Despite the calamitous effects on human health arising from the extensive use of arsenic-enriched ground waters in these regions, the mechanisms of arsenic release from sediments remain poorly characterized and are topics of intense international debate4,5,6,7,8. We use a microscosm-based approach to investigate these mechanisms: techniques of microbiology and molecular ecology are used in combination with aqueous and solid phase speciation analysis of arsenic. Here we show that anaerobic metal-reducing bacteria can play a key role in the mobilization of arsenic in sediments collected from a contaminated aquifer in West Bengal. We also show that, for the sediments in this study, arsenic release took place after Fe(iii) reduction, rather than occurring simultaneously. Identification of the critical factors controlling the biogeochemical cycling of arsenic is one important contribution to fully informing the development of effective strategies to manage these and other similar arsenic-rich ground waters worldwide.

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Figure 1: Reduction of Fe(iii), and mobilization of arsenic in microcosms containing Bengali sediments incubated under a range of biogeochemical regimes.
Figure 2: Shifts in the microbial community of the sediment from the Nadia district, West Bengal, after stimulation of anaerobic metal reduction by acetate.
Figure 3: Reduction of Fe(iii), and mobilization of arsenic in microcosms containing heat-sterilised Bengali sediments.


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This work was supported by EPSRC, the Bangladesh Ministry of Science & Technology (Bangabandhu Fellowship to F.S.I.), The Royal Society, University of Manchester, ORS, GV Instruments and NERC. H. Rowland is thanked for XRD analysis. R. Bilsborrow and F. Mosselmans provided invaluable support in the acquisition of XAS data, which was supported by beamtime awards at Daresbury SRS by CCLRC. Fieldwork by D.C. was supported by KTH, IFCPAR and the University of Kalyani.

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Correspondence to Jonathan R. Lloyd.

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Supplementary Information

Gives details of (1) sediment collection methods and characteristics; (2) XAS analysis of unamended sediment and brief interpretation; (3) calculation and brief discussion of relative redox potentials of Fe(III)/Fe(II) and As(V)/As(III) couples and; (4) phylogenetic affiliation of bacteria detected in unamended and amended microcosms. (PDF 350 kb)

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Islam, F., Gault, A., Boothman, C. et al. Role of metal-reducing bacteria in arsenic release from Bengal delta sediments. Nature 430, 68–71 (2004).

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