| 1. |
- Alam, M.S., et al.
(författare)
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Controls of sedimentary facies on arsenic mobilization in shallow aquifers of the Matlab North Upazila, southeastern Bangladesh
- 2013
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Groundwater extracted from shallow (<100 m bgl) Holocene alluvial aquifers, is the primary source of drinking water in Matlab North Upazila, Southeast Bangladesh. The distribution of lithofacies and its relation to hydrochemistry in such heterogeneous deposits are of fundamental importance for the analysis of groundwater quality. Aquifer sediment samples were collected from 48 locations throughout the study area. Lithofacies distribution was characterized using grain size and sediment colors. Channel fills (sandy) and over bank (silt-clay) deposits the two main lithofacies groups, were identified. These sandy deposits represent an active meandering river or channel fills sediment sequence, which are usually capped by silts and clays of an over bank sediment sequence. All the collected sediments samples were generalized and subdivided based on four distinct color variations, such as Black, White, Off-white, and Red according to Munsell color chart and water-well drillers’ perception.Mineral compositions showed variability with the sediment color and grain size. Red and off-white sediments contain fewer amounts of metastable minerals (hornblende, actinolite, kyanite and pyroxenes etc.) than that of black sediments, whereas black sediments contain higher amount of biotite. The relatively high content of biotite and other dark colored ferromagnesian minerals are responsible for the black and grayish color of these sediments. Ferruginous coating on silicates, particularly on quartz grains, gives the red and off-white coloration. Based on the available information regarding sediment colors of aquifers in which tubewell screens were placed, 44 domestic hand pumped tubewells (HTWs) were selected for water sampling. The groundwater abstracted from black sediments of shallow aquifer showed higher concentrations in DOC (median: 5.81 mg/L), dissolved NH4+ (median: 3.47 mg/L), PO43- (median: 1.36 mg/L), Fe (median: 4.87 mg/L), As (median: 252.53 μg/L) and relatively low Mn (median: 0.54 mg/L) and SO42-(median: 0.59 mg/L) concentrations, whereas groundwater abstracted from off-white and red sediments of shallow aquifer showed lower concentrations in DOC (median: 1.95 and 1.71 mg/L, respectively), dissolved NH4+ (median: 0), PO43- (median: 0.14 and 0.04 mg/L, respectively), Fe (median: 2.25 and 0.63 mg/L, respectively), As (median: 17.36 and 15.05 μg/L, respectively) and relatively high Mn+2 (median: 1.12 and 1.15 mg/L, respectively) and SO42- (median: 0.79 and 0.78 mg/L, respectively) concentrations. The water samples collected from black sediments (median Eh: 211 mV) indicated most reducing environment, followed by white (median Eh: 227 mV), whereas off-white and red sediments (median Eh: 268 and 274 mV) signified less reducing environment. The study supports that the sediment colors in shallow aquifer can be a reliable indicator of high and low-As concentrations and can be a useful tool for local drillers to target arsenic safe aquifers.
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| 2. |
- Bhattacharya, Prosun, 1962-, et al.
(författare)
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Hydrogeochemical contrasts across the multi-level aquifers of Bengal basin in Matlab, Bangladesh : Implications for arsenic free and low-manganese drinking water sources
- 2016
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Ingår i: Arsenic Research and Global Sustainability - Proceedings of the 6th International Congress on Arsenic in the Environment, AS 2016. - : CRC Press/Balkema. ; , s. 45-46
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Konferensbidrag (refereegranskat)abstract
- Targeting shallow, intermediate-deep and deep aquifers, piezometers nests were installed at 15 locations in the Matlab region, an As hotspot in southeastern Bangladesh. Groundwater levels and water quality were monitored for over a three years period. Stable isotopic composition was used to identify the hydrogeological characteristics of different aquifers, hydraulic connectivity between the contaminated and safe aquifers. Within the shallow depth (up to 100m), two aquifers (Aquifer-1 and Aquifer-2) were identified, and groundwater from Aquifer-1 indicated consistently high As concentration was found to be As-enriched (median As levels upto 714 μg/L). Considerable variability in As concentrations were observed in Aquifer-2 wells (6–30 μg/L) comprising relatively oxidized or less reduced red and off-white sands. The intermediate-deep and deep aquifers were found to contain very low As concentration and these aquifers are hydraulically separated from the shallow aquifers. Groundwater depth and elevation and stable isotope signatures also reflect that intermediate-deep and deep aquifers, in most places belong to the same hydrostratigraphic unit (Aquifer-3).
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| 3. |
- Hossain, Mohammed Mojahidul, et al.
(författare)
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Enhancing the capacity of local drillers for installing arsenic-safe drinking water wells—experience from Matlab, Bangladesh
- 2016
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Ingår i: Arsenic Research and Global Sustainability - Proceedings of the 6th International Congress on Arsenic in the Environment, AS 2016. - : CRC Press. ; , s. 630-631
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Konferensbidrag (refereegranskat)abstract
- Nearly 90% of the estimated 10 million tubewells in Bangladesh are installed privately by local drillers for rural drinking water supplies in Bangladesh. The awareness of local drillers on elevated Arsenic (As) concentrations in tubewell water at shallow depths have made them change their practice of installation of tubewells. Using the visual color attributes of the shallow sediments (<100 m) and content of dissolved iron, generally associated with high As concentrations, the local drillers presently install community tubewells at depths targeting red/brownish or off-white sediments. This study recognizes the local tubewell drillers as important stakeholder in the business of tubewell installation. A Sediment Color Tool has been developed to enhance the local driller’s capacity to identify the As-safe aquifers that would bring significant change to reduce As exposure and scale-up safe water access in rural Bangladesh.
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