Microcosm depth profiles of arsenic release in a shallow aquifer, West Bengal

Gault, A. G.; Islam, Farhana; Polya, David A.; Charnock, John; Boothman, Christopher; Chatterjee, Debashis; Lloyd, Jonathan R.

doi:10.1180/0026461056950293

Cited by 84 publications

(56 citation statements)

References 24 publications

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“…It is assumed that both wells are open for much of their length, as no reported screening processes have been undertaken. As there is no significant variation in the pH of both water types, it may be considered that a difference in the sedimentation of the aquifer systems or the residence time of the groundwater as a consequence of well depths, may influence the mobility of the arsenic (Gault et al 2005b;Polizzotto et al 2005;Kinniburgh and Kosmus 2002).…”

Section: Discussionmentioning

confidence: 99%

Arsenic contamination of natural waters in San Juan and La Pampa, Argentina

O'Reilly

Watts

Shaw

et al. 2010

Environ Geochem Health

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Arsenic (As) speciation in surface and groundwater from two provinces in Argentina (San Juan and La Pampa) was investigated using solid phase extraction (SPE) cartridge methodology with comparison to total arsenic concentrations. A third province, Río Negro, was used as a control to the study. Strong cation exchange (SCX) and strong anion exchange (SAX) cartridges were utilised in series for the separation and preservation of arsenite (As ). Samples were collected from a range of water outlets (rivers/streams, wells, untreated domestic taps, well water treatment works) to assess the relationship between total arsenic and arsenic species, water type and water parameters (pH, conductivity and total dissolved solids, TDS). Analysis of the waters for arsenic (total and species) was performed by inductively coupled plasma mass spectrometry (ICP-MS) in collision cell mode. Total arsenic concentrations in the surface and groundwater from Encon and the San José de Jáchal region of San Juan (north-west Argentina within the Cuyo region) ranged from 9 -357 μg l -1As. Groundwater from Eduardo Castex (EC) and Ingeniero Luiggi (LU) in La Pampa (central Argentina within the Chaco-Pampean Plain) ranged from 3 -1326 μg l -1As. The pH range for the provinces of San Juan (7.2 -9.7) and La Pampa (7.0 -9.9) are in agreement with other published literature. The highest total arsenic concentrations were found in La Pampa well waters (both rural farms and pre-treated urban sources), particularly where there was high pH (typically > 8.2), conductivity (> 2600 μS cm As. Arsenic species for both provinces were predominantly As for groundwater, respectively. This translates to a relative As III abundance of 69 -100 % of the total arsenic in surface waters and 32 -100 % in groundwater. This is unexpected because it is typically thought that in oxidising conditions (surface waters), the dominant arsenic species is As V . However, data from the SPE methodology suggests that As III is the prevalent species in San Juan, indicating a greater influence from reductive processes. La Pampa groundwater had As (equating to up to 33 % of the total arsenic). Previously published literature has focused primarily on the inorganic arsenic species, however this study highlights the potentially significant concentrations of organoarsenicals present in natural waters. The potential for separating and preserving individual arsenic species in the field to avoid transformation during transport to the laboratory, enabling an accurate assessment of in-situ arsenic speciation in water supplies is discussed.

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Section: Discussionmentioning

confidence: 99%

Arsenic contamination of natural waters in San Juan and La Pampa, Argentina

O'Reilly

Watts

Shaw

et al. 2010

Environ Geochem Health

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“…The large release of Fe to groundwater by day 252, however, did not cause a concomitant increase in As concentrations. This decoupling could be related to the formation of various secondary Fe minerals, including vivianite and magnetite, which can incorporate As into the new minerals (17,28). Alternatively As may not be distributed uniformly within Fe oxyhydroxide surfaces (10).…”

Section: Implications Of Observed Arsenic Releasementioning

confidence: 99%

“…Previous incubations using natural aquifer sediment have provided valuable mechanistic insights, but intentional or unintentional manipulations of the material have hampered the extrapolation of measured rates to natural conditions (5,10,15,17). A distinguishing feature of the incubations described here is that groundwater and sediment were collected simultaneously using a device coined the needle-sampler, placed immediately under anaerobic conditions in the field, rapidly transported to the laboratory and maintained under such conditions for the 11-month duration of the experiment (18).…”

Section: Introductionmentioning

confidence: 99%

Mobilization of Arsenic During One-Year Incubations of Grey Aquifer Sands from Araihazar, Bangladesh

Radloff

Cheng

Rahman

et al. 2007

Environ. Sci. Technol.

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Elevated As concentrations in shallow groundwater pose a major health threat in Bangladesh and similarly affected countries, yet there is little consensus on the mechanism of As release to groundwater or how it might be influenced by human activities. In this study, the rate of As release was measured directly with incubations lasting 11 months, using sediment and groundwater collected simultaneously in Bangladesh and maintained under anaerobic conditions throughout. Groundwater and grey sediment were collected as diluted slurries between 5 and 38 m depth, a range over which ambient groundwater As concentrations increased from 20 to 100 μg L −1 . Arsenic was released to groundwater in slurries from 5 and 12 m depth at a relatively constant rate of 21 ± 4 (2 σ) and 23 ± 6 μg As kg −1 yr −1 , respectively. Amendment with a modest level of acetate increased the rate of As release only at 12 m (82 ± 18 μg kg −1 yr −1 ). Although the groundwater As concentration was initially highest at 38 m depth, no release of As was observed. These results indicate that the spatial distribution of dissolved As in Bangladesh and local rates of release to groundwater are not necessarily linked. Iron release during the incubations did not occur concurrently with As release, providing further confirmation that the two processes are not directly coupled. Small periodic additions of oxygen suppressed the release of As from sediments at all three depths, which supports the notion that anoxia is a prerequisite for accumulation of As in Bangladesh groundwater.

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“…Members of the Burkholderia genus have been isolated from granitic soils (48) and have been shown to be efficient at mineral weathering (40). Unfortunately, little work has been done to characterize microbial populations in the aquifers and soils of Southeast Asia, and isolates were not available (9,19,20). The metabolic function of Burkholderia fungorum is indistinguishable from those of other heterotrophic bacteria and therefore was chosen as a model organism (12).…”

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confidence: 99%

Microbial Mineral Weathering for Nutrient Acquisition Releases Arsenic

Mailloux

Alexandrova

Keimowitz

et al. 2009

Appl Environ Microbiol

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Tens of millions of people in Southeast Asia drink groundwater contaminated with naturally occurring arsenic. How arsenic is released from the sediment into the water remains poorly understood. Here, we show in laboratory experiments that phosphate-limited cells of Burkholderia fungorum mobilize ancillary arsenic from apatite. We hypothesize that arsenic mobilization is a by-product of mineral weathering for nutrient acquisition. The released arsenic does not undergo a redox transformation but appears to be solubilized from the apatite mineral lattice during weathering. Analysis of apatite from the source area in the Himalayan basin indicates the presence of elevated levels of arsenic, with an average concentration of 210 mg/kg. The rate of arsenic release is independent of the initial dissolved arsenic concentration and occurs at phosphate levels observed in Bangladesh aquifers. We also demonstrate the presence of the microbial phenotype that releases arsenic from apatite in Bangladesh aquifer sediments and groundwater. These results suggest that microbial mineral weathering for nutrient acquisition could be an important mechanism for arsenic mobilization.

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Microcosm depth profiles of arsenic release in a shallow aquifer, West Bengal

Cited by 84 publications

References 24 publications

Arsenic contamination of natural waters in San Juan and La Pampa, Argentina

Arsenic contamination of natural waters in San Juan and La Pampa, Argentina

Mobilization of Arsenic During One-Year Incubations of Grey Aquifer Sands from Araihazar, Bangladesh

Microbial Mineral Weathering for Nutrient Acquisition Releases Arsenic

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