Elevated arsenic in deeper groundwater of the western Bengal basin, India: Extent and controls from regional to local scale

Mukherjee, Abhijit; Fryar, Alan E.; Scanlon, Bridget R.; Bhattacharya, Prosun; Bhattacharya, Anandaroop

doi:10.1016/j.apgeochem.2011.01.017

Cited by 141 publications

(83 citation statements)

References 52 publications

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“…As such, our understanding of the extent and mechanisms of deep arsenic contamination has remained incomplete. Evidence suggests that deep contamination in the Mekong Delta focus area is unlikely to have been caused by the only presently acknowledged mechanism: pumping-induced vertical migration of arsenic or dissolved organic carbon (DOC), which can trigger arsenic release, from the surface or shallow subsurface (6,7,(19)(20)(21). The number of wells above 10 μg/L in the deep zone is seven times greater than in the shallow zone.…”

Section: Resultsmentioning

confidence: 95%

“…"Dig deep to avoid arsenic" (3) has been touted as a safe answer to the provisioning of drinking water in Bangladesh, despite a lack of evidence that deep aquifers indeed remain uncontaminated under prescribed (4,5) or unregulated pumping. In fact, recent studies indicate that arsenic occurrence may be on the rise where deep aquifers are intensively pumped in parts of Bangladesh, West Bengal, India and the Red River Delta, in northern Vietnam (6)(7)(8). In some cases, isolated deep arsenic contamination may be caused by downward leakage through well bores.…”

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confidence: 99%

“…Across basins, dissolved arsenic concentrations tend to be highest in the shallow (<100 m) subsurface (10), where the reactivity of host minerals and the organic carbon needed to dissolve them is also greatest (11,12). As a result, considerable attention has been paid to contamination mechanisms in Holocene units (up to ∼0.011 Ma in age), where affected wells are most commonly found, and to older Pleistocene units (∼0.011-2.6 Ma), where they are usually more rare (6)(7)(8)13). Little is known of arsenic occurrence in older Pliocene-Miocene-age (∼2.6-23 Ma) aquifers or in the thick sequences of interbedded confining clays (i.e., aquitards), which are known to mobilize high levels of dissolved arsenic in nearsurface Holocene clays (12).…”

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confidence: 99%

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Release of arsenic to deep groundwater in the Mekong Delta, Vietnam, linked to pumping-induced land subsidence

Erban¹,

Gorelick²,

Zebker

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

235

126

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Deep aquifers in South and Southeast Asia are increasingly exploited as presumed sources of pathogen- and arsenic-free water, although little is known of the processes that may compromise their long-term viability. We analyze a large area (>1,000 km 2 ) of the Mekong Delta, Vietnam, in which arsenic is found pervasively in deep, Pliocene–Miocene-age aquifers, where nearly 900 wells at depths of 200–500 m are contaminated. There, intensive groundwater extraction is causing land subsidence of up to 3 cm/y as measured using satellite-based radar images from 2007 to 2010 and consistent with transient 3D aquifer simulations showing similar subsidence rates and total subsidence of up to 27 cm since 1988. We propose a previously unrecognized mechanism in which deep groundwater extraction is causing interbedded clays to compact and expel water containing dissolved arsenic or arsenic-mobilizing solutes (e.g., dissolved organic carbon and competing ions) to deep aquifers over decades. The implication for the broader Mekong Delta region, and potentially others like it across Asia, is that deep, untreated groundwater will not necessarily remain a safe source of drinking water.

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Section: Resultsmentioning

confidence: 95%

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confidence: 99%

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confidence: 99%

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Release of arsenic to deep groundwater in the Mekong Delta, Vietnam, linked to pumping-induced land subsidence

Erban¹,

Gorelick²,

Zebker

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

235

126

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“…[50][51][52]) with an average concentration in the range of 1-2 mg/Kg [4,50,51,53]. The concentration of arsenic in the Bengal aquifer sediments range from 0.4 to 40 mg/Kg [4,11,13,33,45,[55][56][57], making up for an average which is slightly higher than that for the average unconsolidated sediments found to be in the range of 2-10 mg/Kg [4]. The sediments of the Bengal basin are not reported to be exceptionally enriched in Fig.…”

Section: Sources Of Arsenicmentioning

confidence: 96%

A Review of Groundwater Arsenic in the Bengal Basin, Bangladesh and India: from Source to Sink

2015

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The groundwater of the Bengal basin, in Bangladesh and West Bengal state of India, is found to be severely polluted by non-point sourced, geogenic arsenic (As), which has been regarded as the largest public health concern in the human history. The geomorphology and geology of the aquifers play very important role in the three dimensional existence of the As in the groundwater. The provenance of the groundwater As of Bengal basin may be hypothesized to be sourced to the Himalayan orogenic belt, where the contaminant might have originated by deep-seated tectono-magmatism and subsequently introduced to the surficial system by exhumation. Later, sedimentary processes transported the As-laden sediments from the orogenic belt to the peripheral foreland basin of Bengal where, under conducive biogeochemical environment, the As is released from the solid-phase to the circulating groundwater. Ferric hydroxides and pyrite are considered to be the two most important host minerals for As, although clay minerals may also act as important substrates for the sorbed As. The mobilized As then exists in the groundwater until a suitable geochemical sink is available. The mobilization process may be related to reductive-dissolution of metal oxides and hydroxides that exist in the unconsolidated sediments of the Bengal basin. Other mechanisms like pyrite oxidation, redox cycling in surficial soils, and competitive ion exchange are also accepted as potential mechanisms for arsenic mobilization, and multiple processes may simultaneously contribute to the mobilization of As. The processes are significantly complicated by redox disequilibria in the Bengal basin aquifers. These inorganic processes may have been significantly catalyzed and accentuated by microbially mediated activities. The tertiary source of groundwater As is the irrigation return flow from the agricultural fields.

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“…Elevated arsenic concentration in shallow groundwater is widespread and very high concentrations (>200 μg/L) are common (BGS and DPHE 2001;Acharyya 2005;Harvey et al 2006;Mukherjee et al 2011). At depths of >150 mbgl, groundwater generally has lower arsenic concentrations.…”

Section: Typology 2: Upper Indus and Upper-mid Ganges Igb Plainmentioning

confidence: 99%

Hydrogeological typologies of the Indo-Gangetic basin alluvial aquifer, South Asia

et al. 2017

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The Indo-Gangetic aquifer is one of the world's most important transboundary water resources, and the most heavily exploited aquifer in the world. To better understand the aquifer system, typologies have been characterized for the aquifer, which integrate existing datasets across the IndoGangetic catchment basin at a transboundary scale for the first time, and provide an alternative conceptualization of this aquifer system. Traditionally considered and mapped as a single homogenous aquifer of comparable aquifer properties and groundwater resource at a transboundary scale, the typologies illuminate significant spatial differences in recharge, permeability, storage, and groundwater chemistry across the aquifer system at this transboundary scale. These changes are shown to be systematic, concurrent with large-scale changes in sedimentology of the Pleistocene and Holocene alluvial aquifer, climate, and recent irrigation practices. Seven typologies of the aquifer are presented, each having a distinct set of challenges and opportunities for groundwater development and a different resilience to abstraction and climate change. The seven typologies are: (1) the piedmont margin, (2) the Upper Indus and Upper-Mid Ganges, (3) the Lower Ganges and Mid Brahmaputra, (4) the fluvially influenced deltaic area of the Bengal Basin, (5) the Middle Indus and Upper Ganges, (6) the Lower Indus, and (7) the marine-influenced deltaic areas.

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Elevated arsenic in deeper groundwater of the western Bengal basin, India: Extent and controls from regional to local scale

Cited by 141 publications

References 52 publications

Release of arsenic to deep groundwater in the Mekong Delta, Vietnam, linked to pumping-induced land subsidence

Release of arsenic to deep groundwater in the Mekong Delta, Vietnam, linked to pumping-induced land subsidence

A Review of Groundwater Arsenic in the Bengal Basin, Bangladesh and India: from Source to Sink

Hydrogeological typologies of the Indo-Gangetic basin alluvial aquifer, South Asia

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