| 1. |
- Bravo, L, et al.
(författare)
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- 2021
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swepub:Mat__t
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| 2. |
- Tabiri, S, et al.
(författare)
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- 2021
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swepub:Mat__t
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| 3. |
- Ahmed, K. Matin, et al.
(författare)
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Arsenic enrichment in groundwater of the alluvial aquifers in Bangladesh : an overview
- 2004
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Ingår i: Applied Geochemistry. - : Elsevier BV. - 0883-2927 .- 1872-9134. ; 19:2, s. 181-200
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Tidskriftsartikel (refereegranskat)abstract
- Arsenic in the groundwater of Bangladesh is a serious natural calamity and a public health hazard. Most groundwater from the shallow alluvial aquifers (<150 m), particularly in the Holocene plain lands, are vulnerable to As-enrichment. Delta plains and flood plains of the Ganges-Brahmaputra river system are moderately to severely enriched and more than 60% of the tube wells are affected. Shallow aquifers in the Meghna river basin and coastal plains are extremely enriched with more than 80% of the tube wells affected. Aquifers in the Pleistocene uplands and Tertiary hills are low in As. The vertical lithofacies sequence of the sediments from highly enriched areas of the country show two distinct lithofacies associations-a dominantly sandy channel-fill association and a fine-grained over bank association. The sediments can be grouped into 4 distinct lithofacies, viz. clay, silty clay, silty sand and sand. Thin section petrography of the As-enriched aquifer sands shows that the sands are of quartzolithic type and derived from the collision suture and fold thrust belt of the recycled orogen provenance. Groundwater is characterized by circum-neutral pH with a moderate to strong reducing nature. The waters are generally of Ca-Mg-HCO3 or Ca-Na-HCO3 type, with HCO3- as the principal anion. Low SO42- and NO3-, and high dissolved organic C (DOC) and NH4+ concentrations are typical chemical characteristics of groundwater. The presence of dissolved sulfides in these groundwaters indicates reduction Of SO4. Total As concentration in the analyzed wells vary between 2.5 and 846 mug l(-1) with a dominance of As(III) species (67-99%). Arsenic(III) concentrations were fairly consistent with the DOC and NH4+ contents. The HNO3 extractable concentrations of As (As-NO3) in the sediments (0.5-17.7 mg kg(-1)), indicate a significant positive correlation with Fe-NO3, Mn-NO3, Al-NO3 and P-NO3. The concentrations Of S-NO3 (816-1306 mg kg(-1)) peaked in the clay sediments with high organic matter (up to 4.5 wt.%). Amounts of oxalate extractable As (As..) and Fe (Fe x) ranged between 0.1-8.6 mg kg(-1) and 0.4-5.9 g kg(-1), respectively. Arsenic(ox) was positively correlated with Fe-ox, Mn-ox, and Al-ox in these sediments. Insignificant amounts of opaque minerals (including pyrite/arsenopyrite) and the presence of high As contents in finer sediments suggests that some As is incorporated in the authigenically precipitated sulfides in the reducing sediments. Moreover, the chemical extractions suggest the presence of siderite and vivianite as solid phases, which may control the aqueous chemistry of Fe and PO43-. Reductive dissolution of Fe oxyhydroxide present as coatings on sand grains as well as altered mica (biotite) is envisaged as the main mechanism for the release of As into groundwater in the sandy aquifer sediments.
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| 4. |
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Groundwater Arsenic Contamination in the Bengal Delta Plain of Bangladesh : KTH Special Publication. Proceedings of the KTH-Dhaka University Seminar
- 2001
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Proceedings (redaktörskap) (refereegranskat)abstract
- The Bengal Delta Plain, like many deltas in Asia, is densely populated. Natural conditions are favourable in terms of soil fertility and abundance of water resources for cultivation. Groundwater is abundant and easily accessible by wells. However, the well drilling campaigns during the last few decades, intended to supply safe water to nearly 97% the population, have turned out to bring out water with toxic levels of arsenic over large areas of the country. The mechanisms of the arsenic mobilisation are not well understood and two conflicting hypothesis have been forwarded. Any measure to improve the situation has to be based on correct understanding of the geochemistry, as incorrect interpretations may worsen the situation. In order to study the mechanisms of arsenic mobilisation, and options for low-cost remediation, a collaborative research project had been initiated by KTH in co-operation with the Department of Geology, Dhaka University, Bangladesh commencing from January, 1999. Sida-SAREC has provided funding for a three year research project. As a starting point and a summing up of the present knowledge a seminar was jointly organised by the Departartment of Geology at the Dhaka University and the Groundwater Arsenic Research Group, Department of Civil and Environmental Engineering at KTH. The present volume is a documentation of a a seminar jointlly organised by the Department of Geology at the Dhaka University and the Department of Civil and Environmental Engineering at KTH. The seminar was aimed at giving a good starting point for future co-operation. The co-operation had already started in the form of thesis works for M. Sc. students following the M. Sc. course Environmental Engineering at KTH. This and part of the coming co-operation is funded by Sida. The University of Dhaka kindly took the trouble of all the local arrangements and provided a major scientific contribution to the seminar. The Swedish Ambassador in Bangladesh honoured the seminar by opening the sessions.
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