Geological Structure of an Arsenic‐Contaminated Aquifer at Sonargaon, Bangladesh

Mitamura, Muneki; Masuda, Harue; Itai, Takaaki; Minowa, Takaharu; Maruoka, Teruyuki; Ahmed, Kazi Matin; Seddique, Ashraf Ali; Biswas, Dipon K.; Nakaya, Shinji; Uesugi, Kenji; Kusakabe, Minoru

doi:10.1086/587789

Cited by 26 publications

(20 citation statements)

References 20 publications

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“…1a), the depth at which most wells extract water 7 . A similar arsenic pattern has been observed at other sites 1,3,4,[8][9][10] and regionally 1 (see Supplementary Information). Previous research at our site provides some insight into the source of the contaminated water.…”

supporting

confidence: 83%

Anthropogenic influences on groundwater arsenic concentrations in Bangladesh

et al. 2009

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The origin of dissolved arsenic in the Ganges Delta has puzzled researchers ever since the report of widespread arsenic poisoning two decades ago. Today, microbially mediated oxidation of organic carbon is thought to drive the geochemical transformations that release arsenic from sediments, but the source of the organic carbon that fuels these processes remains controversial. At a typical site in Bangladesh, where groundwater-irrigated rice fields and constructed ponds are the main sources of groundwater recharge, we combine hydrologic and biogeochemical analyses to trace the origin of contaminated groundwater. Incubation experiments indicate that recharge from ponds contains biologically degradable organic carbon, whereas recharge from rice fields contains mainly recalcitrant organic carbon. Chemical and isotopic indicators as well as groundwater simulations suggest that recharge from ponds carries this degradable organic carbon into the shallow aquifer, and that groundwater flow, drawn by irrigation pumping, transports pond water to the depth where dissolved arsenic concentrations are greatest. Results also indicate that arsenic concentrations are low in groundwater originating from rice fields. Furthermore, solute composition in arsenic-contaminated water is consistent with that predicted using geochemical models of pond-water-aquifer-sediment interactions. We therefore suggest that the construction of ponds has influenced aquifer biogeochemistry, and that patterns of arsenic contamination in the shallow aquifer result from variations in the source of water, and the complex three-dimensional patterns of groundwater flow.

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confidence: 83%

Anthropogenic influences on groundwater arsenic concentrations in Bangladesh

et al. 2009

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“…Arsenic content ranged from non-detectable to 36.87 mg/kg, with the average value of 5.6 mg/kg. Core samples collected adjacent to a highly As contaminated tube well show that high As concentrations (from 7.0 to 36.87 mg/kg) are found down to 44.5 m, with the highest content at 44.5 m. Below that, the sediments are mainly medium to coarse sand, and As concentrations decrease abruptly down to stable low concentrations It is, therefore, postulated that the vertical leakage and translocation, controlled by electrical conductivity, dissolved organic matter, and land gradient, play a key role in the distribution of As from the upper aquifer to the middle one [35,41]. The present study and previous studies in Bangladesh and West Bengal, India, have shown that the source(s) of As seems to be locally distributed in lenses of fine-grained sediments (e.g., silty sand, clayey silt, clay), and peat in the Holocene deposits of the upper aquifer, which contain also high concentrations of Fe, Mn and Al oxides and organic matter [14,33,[42][43][44].…”

Section: Sediment Characteristicsmentioning

confidence: 99%

“…Seddique et al [33], Itai et al [34] and Mitamura et al [35] speculated that reduction of Fe oxyhydroxide is not the only mechanism of As mobilization. In addition, chemical weathering of biotite and/or other basic minerals induced by infiltration of oxic surface water in the Holocene aquifer could be important as a primary cause of As mobilization, because the biotite minerals contained high As concentrations.…”

Section: Scanning Electron Microscope (Sem)mentioning

confidence: 99%

“…The reducing conditions are generated due to were markedly more prominent in shallow tube wells as compared to deep tube wells [26]. The contaminated aquifers are confined to the GBM delta plains of the Holocene period, whereas the uplands of the Pleistocene period are uncontaminated [14,19,28,35,49,50].…”

Section: Mechanism Of Arsenic Mobilizationmentioning

confidence: 99%

“…The aim of the present study is therefore to examine the groundwater, sediment geochemistry and mineralogy, along with surface water and soils in order to ascertain the sources and mechanism of As release into the groundwater and to investigate the natural and anthopogenic (agricultural sources) contributions to high levels of As in groundwater. This study also investigates the surface and composition of the biotite minerals with electron microscopy in order to assess the role of biotite minerals on As mobilization due to the infiltration of oxic surface water into the Holocene aquifer, as proposed by Seddique et al [33], Itai et al [34] and Mitamura et al [35].…”

Section: Introductionmentioning

confidence: 99%

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Arsenic Contamination in Groundwater of Bangladesh: Perspectives on Geochemical, Microbial and Anthropogenic Issues

Anawar

Akai

Mihaljevič

et al. 2011

Water

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A groundwater, sediment and soil chemistry and mineralogical study has been performed to investigate the sources and mobilization process of Arsenic (As) in shallow aquifers of Bangladesh. The groundwater from the shallow aquifers is characterized by high concentrations of Arsenic (47.5-216.8 µg/L), iron (0.85-5.83 mg/L), and phosphate, along with high electrical conductivity (EC). The groundwater has both very low oxidation-reduction potential (Eh) and dissolved oxygen (DO) values indicating reducing conditions. By contrast, the deep aquifers and surface waters (pond, canal) have very low concentrations of Arsenic (<6 µg/L), iron (0.12-0.39 mg/L), and phosphate along with a relatively low EC. Furthermore, the values of Eh and DO are high, indicating oxic to suboxic conditions. Arsenic is inversely correlated with Eh values in the upper aquifer, whereas no relationship in the deeper aquifer is observed. These results suggest that As mobilization is clearly linked to the development of reducing conditions. The clayey silt, OPEN ACCESSWater 2011, 3 1051 enriched in Fe, Mn, Al oxides and organic matter, and deposited in the middle unit of shallow aquifers, contains moderately high concentrations of As, whereas the sediments of deep aquifers and silty mud surface soils from paddy fields and ponds contain a low content of As (Daudkandi area). Arsenic is strongly correlated with the concentrations of Fe, Mn and Al oxides in the core samples from the Daudkandi and Marua areas. Arsenic is present in the oxide phase of Fe and Mn, phyllosilicate minerals and in organic matter in sediments. This study suggests that adsorption or precipitation of As-rich Fe oxyhydroxide on the surface or inner sites of biotite might be responsible for As concentrations found in altered biotite minerals by Seddique et al. Microbially or geochemically mediated reductive dissolution of Fe oxyhydroxides is the main mechanism for As release. The reducing conditions are caused by respiratory decomposition of organic matter, either sedimentary or labile organic C. The process can be accelerated by agricultural activity and domestic organic wastes. An agricultural fertilizer can directly contribute As to groundwater as well as promote As mobilization by ion-exchange with phosphorus.

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Heavy metals in sediments of the Yarlung Tsangbo and its connection with the arsenic problem in the Ganges–Brahmaputra Basin

Kang

Zhang

et al. 2010

Environ Geochem Health

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The Yarlung Tsangbo (YT) is a large river running across southern Tibet and has significant effects on its lower reaches, the Ganges-Brahmaputra Basin. In order to investigate the geochemical features of the YT, 18 surface sediment samples were collected; ten trace element concentrations were measured for bulk sediments and two fine grain size fractions. Meanwhile, basic physicochemical parameters and element concentrations of river water were also analyzed. Results indicated that the river water was alkaline (pH 8.42) and that dissolved oxygen was mainly controlled by river water temperature. Some elements (e.g., Zn and Ni) showed close negative relationship to mean grain size of the sediments. Concentrations of most heavy metals, except As of the YT bulk sediments, were similar to those of Upper Crustal Concentration and its lower reaches, indicating almost no anthropogenic impact. Arsenic of the YT sediments was derived fundamentally from the parent rocks of the YT Basin and was far higher than that of its lower reaches. This indicates that relatively small amounts of As from the study area were transported down to the Brahmaputra River under present, relatively dry climatic conditions. However, more YT sediments might have been transported to its low reaches during the Holocene due to the wet climate, giving high As concentration in Holocene sediments of the Ganges-Brahmaputra Basin. Thus, As transported by the YT may produce important influence on the Ganges-Brahmaputra Basin and contribute to its high As concentration in groundwater.

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Geological Structure of an Arsenic‐Contaminated Aquifer at Sonargaon, Bangladesh

Cited by 26 publications

References 20 publications

Anthropogenic influences on groundwater arsenic concentrations in Bangladesh

Anthropogenic influences on groundwater arsenic concentrations in Bangladesh

Arsenic Contamination in Groundwater of Bangladesh: Perspectives on Geochemical, Microbial and Anthropogenic Issues

Heavy metals in sediments of the Yarlung Tsangbo and its connection with the arsenic problem in the Ganges–Brahmaputra Basin

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