Sources of low-arsenic groundwater in the Bengal Basin: investigating the influence of the last glacial maximum palaeosol using a 115-km traverse across Bangladesh

Hoque, M. A.; McArthur, J. M.; Sikdar, P. K.

doi:10.1007/s10040-014-1139-8

Cited by 38 publications

(60 citation statements)

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“…Recent models for As‐affected aquifers in Southeast Asia have elucidated similar influential factors and variables (groundwater age, organic carbon, aquifer, depth, etc. ; Biswas et al, ; Biswas, Bhattacharya, et al, ; Biswas, Neidhardt, et al, ; Desbarats et al, ; Gillispie et al, ; McArthur et al, , , ; Mihajlov et al, ) related to modeled As hazard in aquifers (Biswas, Neidhardt, et al, ; Bonsor et al, ; Hoque et al, , , ; Mahmud et al, ; Mukherjee et al, ; Podgorski et al, ).…”

Section: Resultsmentioning

confidence: 99%

Predicting geogenic Arsenic in Drinking Water Wells in Glacial Aquifers, North‐Central USA: Accounting for Depth‐Dependent Features

Erickson

Elliott

Christenson

et al. 2018

Water Resources Research

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Chronic exposure to arsenic (As) via drinking groundwater is a human health concern worldwide. Probabilities of elevated geogenic As concentrations in groundwater were predicted in complex, glacial aquifers in Minnesota, north-central USA, a region that commonly has elevated As concentrations in well water. Maps of elevated As hazard were created for depths typical of drinking water supply and with well construction attributes common for domestic wells. Conventional variables describing aquifer properties and materials, position on the hydrologic landscape, and soil geochemistry were among the most influential for predicting the probability of elevated As. We also found that certain well construction attributes were influential in predicting As hazard. Smaller distances between the top of the well screen and overlying aquitard (proximity) and shorter well screen lengths were each associated with higher probabilities of elevated As. Influential predictor variables, which are either mapped across the region or are well construction attributes, are proxies in the model for measurable physical or geochemical causes of elevated As (e.g., redox condition, till or aquifer sediment chemistry, and water chemistry), which are not mapped across the region. Our setting shares some important characteristics with deltaic and other high-As aquifers in Southeast Asia: late Quaternary age, complex layering of coarse-and fine-grained materials, low-As sediment concentrations, and geochemical controls on As mobilization. Translating three-dimensional geologic and geochemical understanding of As mobility to quantifiable variables for modeling with powerful, flexible statistical tools could improve predictions and help identify safer groundwater supply options in the USA, Southeast Asia, and elsewhere.Plain Language Summary This study demonstrates that certain well construction attributes are influential in predicting arsenic (As) concentrations in drinking water wells. Smaller distances between the top of the well screen and overlying aquitard, and shorter well screen lengths, were each associated with higher probabilities of elevated As. Chronic exposure to As via drinking groundwater is a human health concern worldwide, and Minnesota, USA, commonly has elevated As concentrations in well water. This study describes a new, novel, and important finding from an As probability model: Controllable well construction choices (not just location or depth) influence As concentrations in drinking water from wells.

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Section: Resultsmentioning

confidence: 99%

Predicting geogenic Arsenic in Drinking Water Wells in Glacial Aquifers, North‐Central USA: Accounting for Depth‐Dependent Features

Erickson

Elliott

Christenson

et al. 2018

Water Resources Research

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“…The Holocene stratigraphy of Sylhet basin has been constructed over the modest relief (~50 m) of antecedent Pleistocene topography (Figs b and ), the boundary of which can often be identified by deeply oxidized sands and low plasticity (stiff) muds, the result of extended sub‐aerial exposure during lowstands of sea‐level (Ravenscroft et al ., ; McArthur et al ., ; Hoque et al ., ; Pickering et al ., ; Williams, ). This Pleistocene topography is characterized by shallowly buried (1–10 m deep) remnant terraces on the western side of Sylhet basin (Figs b and ).…”

Section: Resultsmentioning

confidence: 99%

Holocene Brahmaputra River path selection and variable sediment bypass as indicators of fluctuating hydrologic and climate conditions in Sylhet Basin, Bangladesh

2017

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The Holocene stratigraphy of Sylhet basin, a tectonically influenced sub-basin within the Ganges-Brahmaputra-Meghna delta (GMBD), provides evidence for autogenic and allogenic controls on fluvial system behaviour. Using Holocene lithology and stratigraphic architecture from a dense borehole network, patterns of bypass-dominated and extraction-enhanced modes of sediment transport and deposition have been reconstructed. During a~3-kyr mid-Holocene occupation of Sylhet basin by the Brahmaputra River, water and sediment were initially (~7.5-6.0 ka) routed along the basin's western margin, where limited downstream facies changes reflect minimal mass extraction and bypass-dominated transport to the basin outlet. Sedimentdispersal patterns became increasingly depositional~6.0-5.5 ka with the activation of a large (~2250 km 2 ) splay that prograded towards the basin centre while maintaining continued bypass along the western pathway. Beginning~5.0 ka, a second splay system constructed an even larger (~3800 km 2 ) lobe into the most distal portions of the basin along the Shillong foredeep. This evolution from a bypass-dominated system to one of enhanced mass extraction is well reflected in (i) the rapid downstream fining of deposited sand and (ii) a change in facies from amalgamated channel deposits to mixed sands and muds within discrete depositional lobes. The persistence of sediment bypass suggests that seasonal flooding of the basin by local runoff exerts a hydrologic barrier to overbank flow and is thus a principal control on river path selection. This control is evidenced by (i) repeated, long-term preference for occupying a course along the basin margin rather than a steeper path to the basin centre and (ii) the persistence of an underfilled, topographically low basin despite sediment load sufficient to fill the basin within a few hundred years. The progradation of two 10-20-m thick, sandy mega-splays into the basin interior reflects an alternative mode of sediment dispersal that appears to have operated only in the mid-Holocene (~6.0-4.0 ka) during a regional weakening of the summer monsoon. The reduced water budget at that time would have lowered seasonal water levels in the basin, temporarily lessening the hydrologic barrier effect and facilitating splay development into the basin interior. Overall, these results place basin hydrology as a first-order control on fluvial system behaviour, strongly modifying the perceived dominance of tectonic subsidence. Such coupling of subsidence, fluvial dynamics and local hydrology have been explored through tank experiments and modelling; this field study demonstrates that complex, emergent behaviours can also scale to the world's largest fluvial system.Deciphering the response of depositional systems to changes in sediment transport dynamics, climate and Correspondence: R. Sincavage,

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“…Further proof of anoxia is that concentrations of the oxyanions V and U, which are insoluble under Fe‐reducing conditions, are low when concentrations of Fe and As are high (Figure S2; Table S2) as is found in groundwaters in the Bengal Basin (cf. Hoque, McArthur, & Sikdar, ). Depth profiles of NO 3 , NH 4 , Fe, and Mn show much scatter owing to local variations in aquifer properties.…”

Section: Discussion Of Arsenicmentioning

confidence: 99%

Arsenic and other water‐quality issues affecting groundwater, Indus alluvial plain, Pakistan

Naseem

McArthur

2018

Hydrological Processes

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Groundwater beneath the alluvial plain of the Indus River, Pakistan, is reported to be widely polluted by arsenic (As) and to adversely affect human health. In 79 groundwaters reported here from the lower Indus River plain in southern Sindh Province, concentrations of As exceeded the WHO guideline value for drinking water of 10 μg/L in 38%, with 22% exceeding 50 μg/L, Pakistan's guideline value. The As pollution is caused by microbially‐mediated reductive dissolution of sedimentary iron oxyhydroxides in anoxic groundwaters; oxic groundwaters contain <10 μg/L of As. In the upper Indus River plain, in Punjab Province, localized As pollution of groundwater occurs by alkali desorption as a consequence of ion exchange in groundwater, possibly supplemented by the use for irrigation of groundwater that has suffered ion exchange in the aquifer and so has values >0 for residual sodium carbonate. In the field area in southern Sindh, concentrations of Mn in groundwater exceed 0.4 mg/L in 11% of groundwaters, with a maximum of 0.7 mg/L, as a result of reduction of sedimentary manganese oxides. Other trace elements pose little or no threat to human health. Salinities in groundwaters range from fresh to saline (electrical conductivity up to 6 mS/cm). High salinities result from local inputs of waste water from unsewered sanitation but mainly from evaporation/evapotranspiration of canal water and groundwater used for irrigation. The process does not concentrate As in the groundwater owing to sorption of As to soils. Ion exchange exerts a control on concentrations of Na, Ca, and B but not directly on As. High values of Cl/Br mass ratios (most ≫288, the marine value) reflect the pervasive influence on groundwater of sewage‐contaminated water from irrigation canals through seepage loss and deep percolation of irrigation water, with additional, well‐specific, contributions from unsewered sanitation.

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Sources of low-arsenic groundwater in the Bengal Basin: investigating the influence of the last glacial maximum palaeosol using a 115-km traverse across Bangladesh

Cited by 38 publications

References 36 publications

Predicting geogenic Arsenic in Drinking Water Wells in Glacial Aquifers, North‐Central USA: Accounting for Depth‐Dependent Features

Predicting geogenic Arsenic in Drinking Water Wells in Glacial Aquifers, North‐Central USA: Accounting for Depth‐Dependent Features

Holocene Brahmaputra River path selection and variable sediment bypass as indicators of fluctuating hydrologic and climate conditions in Sylhet Basin, Bangladesh

Arsenic and other water‐quality issues affecting groundwater, Indus alluvial plain, Pakistan

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