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- Bhattacharya, Prosun, et al.
(författare)
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Geogenic arsenic in groundwaters from Terai Alluvial Plain of Nepal
- 2003
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Ingår i: Journal de Physique IV. - : EDP Sciences. - 1155-4339 .- 1764-7177. ; 107, s. 173-176
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Tidskriftsartikel (refereegranskat)abstract
- The origin and mobility of arsenic (As) in the groundwater environment has received serious attention in recent years. Recent studies have reported naturally occurring As in groundwaters of the Terai Alluvial Plains (TAP) in southern Nepal, where groundwater exploitation has increased since the 1960s. The source of As in TAP is geogenic and leached primarily due to weathering of As bearing rocks and sediments in the Himalayas. In our present study, we have investigated the groundwater chemistry in the central part of the TAP in Nawalparasi district. TAP groundwaters are near-neutral to alkaline, with predominantly reducing character and high HCO3-, low SO4- and NO3- concentrations. Elevated HCO3 levels possibly result due to the oxidation of organic matter, low SO42- levels reflect sulfate reduction. Elevated NH4+ concentrations in these groundwaters suggest dissimilatory nitrate reduction in the aquifers. Total arsenic (As,.,) levels in groundwater varied from 1.7 mug/L to as high as 404 mug/L with dominance of As(III) species and elevated levels of dissolved Fe and Mn. Arsenic is mobilized in groundwaters as a result of desorption of As-oxyanions adsorbed onto Fe- and Mn-oxides as well as reductive dissolution of these surface reactive phases from the sediments along with release of As in anoxic groundwaters.
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- Hossain, Mohammed, 1960-, et al.
(författare)
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Sustainable Arsenic Mitigation (SASMIT) : An approach for developing a color based tool for targeting arsenic-safe aquifers for drinking water supply
- 2012
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Ingår i: METALS AND RELATED SUBSTANCES IN DRINKING WATER. - : IWA PUBLISHING. ; , s. 272-276
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Konferensbidrag (refereegranskat)abstract
- Presence of high concentration of geogenic arsenic (As) in water and soil become a big health risk towards millions of people in various magnitudes through drinking water. To minimize arsenic interaction with human considered as a global challenge. The main objective of this research is to develop a simple, easy and cost-effective arsenic identification tool which would be easily acceptable by the inhabitants and local well drillers. The relationship of sediment color and corresponding As concentrations in water has already been demonstrated and is being further studied under SASMIT project. A total of 1920 sediment samples from 15 locations bored up to a depth of 250 m have been scientifically evaluated according to the color codes using Munsell Color Chart. A total of 60 varieties observed and simplified into four color groups viz. black, white, off-white and red. It is revealed that red and off-white sands can be targeted for As-safe water. White sands can also be safe but uncertainty is high and black sediments produce water with highest As concentration, although Mn content in waters sampled from white and black sediments is relatively low. Further refinement is going on for improving the tool for targeting aquifers which can be safe for both arsenic and manganese.
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| 10. |
- Bhattacharya, Prosun, et al.
(författare)
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Distribution and mobility of arsenic in the Rio Dulce alluvial aquifers in Santiago del Estero Province, Argentina
- 2006
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 358:1-3, s. 97-120
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Tidskriftsartikel (refereegranskat)abstract
- Factors controlling arsenic (As) mobilization in the aquifers of the Rio Dulce alluvial cone were investigated. Groundwater analyses show severe As contamination (average concentration of 743 mu g/L) from geogenic sources, but spatial variability of As concentration is considerable. Sequential leaching of sediment samples from unsaturated zone using de-ionised water, bicarbonate, acetate, and oxalate extracted As to different extents. Sediment oxalate extraction showed that Al and Mn oxide and hydroxides are more abundant than Fe oxides and hydroxides, in spite of similar total Fe, Mn, and Al concentrations in the sediment. Speciation calculations performed for saturated zone samples indicated that Fe and Al oxides and hydroxides are stable in groundwater, suggesting that As adsorption processes may be to some extent controlled by the presence of Fe and Al mineral phases. Principal Component Analysis (PCA) showed that As is related to F, V, Mo, B, Si, most likely due to their common origin in volcanic ash. This suggests the volcanic ash as the probable source of groundwater As. Locally, elevated pH values linked to carbonate dissolution, cation exchange, and dissolution of silicates promote release of adsorbed As. Another factor contributing to the release of As locally may be the input of organic matter from excessive irrigation. The conceptual model of As release includes: i) As influx from dissolution of volcanic glass in volcanic ash, ii) adsorption of As on the surface of Fe and Al mineral phases in relatively low pH zones, and iii) high mobility of As in high pH zones. Future work should be focused on the determination of mineralogical forms of As in volcanic ash and on detailed investigation on factors controlling As mobility.
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