Vulnerability of deep groundwater in the Bengal Aquifer System to contamination by arsenic

Burgess, W.; Hoque, M. A.; Michael, H. A.; Voss, Clifford I.; Breit, George N.; Ahmed, Kazi Matin

doi:10.1038/ngeo750

Cited by 190 publications

(148 citation statements)

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“…In the Mekong Delta, dramatic changes occurred in vegetation types, flooding patterns, hydraulic gradients, and mineral weathering (27,28). Evidence of these changes is seen in the abundance of ferric (hydr)oxides that give Pleistocene sands in Bangladesh their oft-noted brown or orange color (8,10,13,29,30). These oxidized deposits have a higher capacity for arsenic adsorption (4,21,31) and are associated with aquifers that are low in dissolved arsenic, which are found at greater depths in the Bengal Basin owing to higher sedimentation rates.…”

Section: Resultsmentioning

confidence: 99%

“…"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.…”

mentioning

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.

239

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: 99%

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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.

239

126

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“…Recent investigations have raised concern for the security of deep groundwater pumping against invasion by arsenic drawn down from shallow levels (Michael and Voss 2008). Modelling studies have highlighted the need for more measurements of groundwater head in the deep regions of the Bengal Aquifer System (Ravenscroft et al 2004;Michael and Voss 2009b;Burgess et al 2010) and further research is needed to ascertain the hydraulic connection between the shallow and deeper groundwater resource in these areas.…”

Section: Arsenicmentioning

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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“…Arsenic-contaminated groundwater used for drinking and cooking is the cause of health problems such as keratosis and cancers reported in Bangladesh and the West Bengal area of India (Acharyya et al, 2000;Akai et al, 2004;Burgess et al, 2010;Das et al, 1996;Dowling et al, 2002;Nickson et al, 2000). Although the source of contamination is believed to be natural, cases elsewhere such as those reported in Thailand, Ghana and some areas of the United States were due to the improper disposal of contaminated soil or rock from mining activities (Bowell, 1993;Choprapawon and Rodcline, 1997;Welch et al, 1999;Williams, 1997).…”

Section: Introductionmentioning

confidence: 99%

The roles of pyrite and calcite in the mobilization of arsenic and lead from hydrothermally altered rocks excavated in Hokkaido, Japan

Tabelin¹,

Igarashi²,

Tamoto³

et al. 2012

Journal of Geochemical Exploration

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This paper describes the enrichment of hydrothermally altered volcanic and sedimentary rocks with arsenic (As) and lead (Pb), and the effects of pyrite and calcite on the mobilities and release mechanisms of these toxic elements under oxic and anoxic conditions. Enrichment of the altered rock with As and Pb predominantly occurred in precipitated pyrite grains and not on the alumino-silicate minerals making up the matrix of the rock. Arsenic was incorporated in pyrite grains formed during alteration in both volcanic and sedimentary rocks, but Pb was only found in the pyrite grains of the volcanic rock samples. When in contact with water, altered volcanic rocks had acidic pH while altered sedimentary rocks had alkaline pH. The mobilities of both As and Pb from the altered rocks were enhanced at acidic and alkaline pH and a minimum was observed in the circumneutral pH under both oxic and anoxic conditions. The absence of O 2 retarded the oxidation of pyrite most notably in the alkaline region but not in the acidic and circumneutral pH. The absence of CO 2 increased the pH of samples with significant calcite content but did not affect those containing substantial amounts of pyrite. Increasing the CO 2 also had insignificant effect on the concentrations of As and Pb in the leachate. The mechanisms controlling the mobilization of As and Pb from these rocks like dissolution of soluble secondary minerals, pyrite oxidation and adsorption were all related to pyrite while the pH of the rock when in contact with water was controlled by pyrite and calcite. Thus, excavated waste rocks that have been altered can be grouped based on the relative abundance of pyrite and calcite and their pH when in contact with water.

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Vulnerability of deep groundwater in the Bengal Aquifer System to contamination by arsenic

Cited by 190 publications

References 32 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

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

The roles of pyrite and calcite in the mobilization of arsenic and lead from hydrothermally altered rocks excavated in Hokkaido, Japan

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