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| 2. |
- Bhattacharya, Prosun, 1962-, et al.
(författare)
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Arsenic in Groundwater of Bangladesh : Options for Safe Drinking Water
- 2010
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The study was undertaken in order to find and scientifically validate the options for arsenic safewater in Bangladesh. The study has been carried out in a geological province where most of theshallow wells have arsenic above the allowable limit for drinking water according to Bangladeshstandard. The original study plan has been modified as newer information on arsenic mobilisationand mitigation was available. Accordingly the emphasis on dug well and arsenic removal filter hadbeen shifted to other options such as geologically targeted aquifers. Also at the same time therehas been collaboration with number of other projects been carried out in and around the studyarea. Eventually the main focus of the research was shifted to capacity development in order toenhance the local capability for finding safer sources drinking water in the study area and othersimilar environments in the country.
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| 3. |
- Bhattacharya, Prosun, 1962-, et al.
(författare)
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Arsenic in Swedish groundwater Mobility and risk for naturally elevated concentrations : Final Report
- 2010
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Arsenic (As) in groundwater has become a serious global problem during the last few decades forseveral reasons. The chronic toxicity from drinking water has motivated the lowering of thehealth limit from 50 μg/L to 10 μg/L. Due to the rather complicated analytical chemistry of As ithas seldom been analysed in groundwater. Once the common occurrence of excess As ingroundwater has been discovered like in Bangladesh it has become evident that As in concentrationswell above the health limit can be easily mobilized from very moderate amounts in the aquifermaterial under specific conditions. There are essentially three mechanisms of mobilization: 1)oxidation of sulphides containing As; 2) reduction of ferric compounds releasing adsorbed Asand 3) high pH conditions leading to lowered adsorption capacity of ferric and aluminium compounds. This study has aimed at investigating the mobilization of As under the conditions existing in Precambrianrocks and the overlying tills in Sweden. As study area the north-eastern part of theVästerbotten county was chosen. The occurrence of sulphides both in mineralisations and insome of the country rocks may infer that the risk of elevated As concentrations in groundwatermay be a bit higher there than elsewhere in Sweden. The hypothesis was that the two firstmechanisms mentioned above would be responsible for any elevated groundwater As in groundwater,thus either oxidation of sulphides or reducing conditions leading the reduction of ferrichydroxides. Samples were collected from drilled wells, dug wells and springs. pH, Eh and temperature weremeasured in the field and the samples were filtered through 0.20 m filters in the field. As(II) wasseparated from As(V) in the field by ion-exchangers. As redox conditions are the determinantsfor the mobilization of As the groundwaters have been classified into five redox classes followinga classification developed by the Swedish Environmental Protection Agency. Dug wells with elevatedAs turned out to be in the oxidizing part of the classification while drilled wells were foundin all classes. This is reasonable as drilled wells often collect water from different environmentsthrough the different fracture systems the drilled wells contact. Wetland springs are found tohave moderately reducing water high in iron. While drilled wells and dug wells show a wide spectrumof As(III)/As(tot) ratios the As(III) is clearly dominant in wetland springs. Drilled wellsshowed the highest concentrations of As up to 300 μg/L and wells drilled in alkaline volcanicrocks had the highest median concentrations of As. Arsenic in wetland springs were strongly correlatedto iron. Another clear relationship was that groundwater with even low concentrations ofnitrate was low in As. Obviously the presence of nitrate indicates an oxidizing environmentwhere As is firmly adsorbed onto ferric hydroxides. There was no clear relationship with sulphateindicating that the drilled wells which made up the majority of the groundwaters often had waterof a mixed origin coming to the well via different fracture systems. The results indicate that As should in general be analysed in household wells as it is difficult topredict the presence of elevated concentrations from the major ion chemistry. High iron concentrationis a factor that indicates an elevated risk of As above the health limit. Nitrate on the otherhand indicates a low risk for elevated As concentration.
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| 4. |
- Bhattacharya, Prosun, et al.
(författare)
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Temporal and seasonal variability of arsenic in drinking water wells in Matlab, southeastern Bangladesh : A preliminary evaluation on the basis of a 4 year study
- 2011
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Ingår i: Journal of Environmental Science and Health. Part A. - : Informa UK Limited. - 1093-4529 .- 1532-4117. ; 46:11, s. 1177-1184
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Tidskriftsartikel (refereegranskat)abstract
- Temporal and seasonal variability of As concentrations in groundwater were evaluated in As-affected areas of Matlab, southeastern Bangladesh. Groundwater samples from 61 randomly selected tubewells were analyzed for As concentrations over a period of three years and four months (from July 2002 to November 2005) and monitored seasonally (three times a year). The mean As concentrations in the sampled tubewells decreased from 153 to 123 mu g/L during July 2002 to November 2005. Such changes were pronounced in tubewells with As concentration >50 mu g/L than those with As concentrations <50 mu g/L. Similarly, individual wells revealed temporal variability, for example some wells indicated a decreasing trend, while some other wells indicated stable As concentration during the monitoring period. The mean As concentrations were significantly higher in Matlab North compared with Matlab South. The spatial variations in the mean As concentrations may be due to the differences in local geological conditions and groundwater flow patterns. The variations in mean As concentrations were also observed in shallow (<40 m) and deep (>40 m) wells. However, to adequately evaluate temporal and seasonal variability of As concentration, it is imperative to monitor As concentrations in tubewells over a longer period of time. Such long-term monitoring will provide important information for the assessment of human health risk and the sustainability of safe drinking water supplies.
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| 5. |
- Hossain, M., et al.
(författare)
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Potentiality of intermediate depth aquifer as a source of arsenic and manganese safe tubewells in Bangladesh
- 2012
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Ingår i: Understanding the Geological and Medical Interface of Arsenic, As 2012 - 4th International Congress: Arsenic in the Environment. - : Taylor & Francis Group. - 9780415637633 ; , s. 71-73
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Konferensbidrag (refereegranskat)abstract
- Shallow tubewells excepting those installed in red/off-white sediments are mostly contaminated with high arsenic. Social survey conducted in 96 villages of Matlab, a worse-affected area of Bangladesh, reveals that only 18% of tubewells provide As-safe water. In such a condition, high Manganese in many wells is found to be an additional problem. Based on monitoring in depth-specific piezometers, drinking water wells were installed in intermediate depth aquifer around 120 m. Ninety percent of the wells installed in light grey medium sand, had arsenic concentrations below the Bangladesh standard of 50 ÎŒg/L and manganese was within the previous WHO guideline (0.4 mg/L). Availability of similar sand over this depth range could be targeted by local drillers to tap safe water at a reasonable cost. Replication trials and periodical monitoring are emphasized for validation and sustainability.
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| 6. |
- Hossain, Mohammed, et al.
(författare)
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Sediment color tool for targeting arsenic-safe aquifers for the installation of shallow drinking water tubewells
- 2014
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 493, s. 615-625
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Tidskriftsartikel (refereegranskat)abstract
- In rural Bangladesh, drinking water supply mostly comes from shallow hand tubewells installed manually by the local drillers, the main driving force in tubewell installation. This study was aimed at developing a sediment color tool on the basis of local driller's perception of sediment color, arsenic (As) concentration of tubewell waters and respective color of aquifer sediments. Laboratory analysis of 521 groundwater samples collected from 144 wells during 2009 to 2011 indicate that As concentrations in groundwater were generally higher in the black colored sediments with an average of 239 mu g/L. All 39 wells producing water from red sediments provide safe water following the Bangladesh drinking water standard for As (50 mu g/L) where mean and median values were less than the WHO guideline value of 10 mu g/L. Observations for off-white sediments were also quite similar. White sediments were rare and seemed to be less important for well installations at shallow depths. A total of 2240 sediment samples were collected at intervals of 1.5 m down to depths of 100 m at 15 locations spread over a 410 km(2) area in Matlab, Bangladesh and compared with the Munsell Color Chart with the purpose of direct comparison of sediment color in a consistent manner. All samples were assigned with Munsell Color and Munsell Code, which eventually led to identify 60 color shade varieties which were narrowed to four colors (black, white, off-white and red) as perceived and used by the local drillers. During the process of color grouping, participatory approach was considered taking the opinions of local drillers, technicians, and geologists into account. This simplified sediment color tool can be used conveniently during shallow tubewell installation and thus shows the potential for educating local drillers to target safe aquifers on the basis of the color characteristics of the sediments.
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| 7. |
- Hossain, Mohammad, et al.
(författare)
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Strategic approach for up-scaling safe water access considering hydrogeological suitability and social mapping in Matlab, southeastern Bangladesh
- 2013
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Konferensbidrag (refereegranskat)abstract
- In recent years, there has been a significant progress in understanding the source and mobilization process, sediment-water interactions, and distributions of arsenic in groundwater environment in Bangladesh. However, the impacts of arsenic mitigation are still very limited. A social survey conducted during 2009-2011 in 96 villages in Matlab revealed that only 18% of total tubewells provide As-safe water. The safe water access also varied between 0 and 90 percent in the region due to lack of knowledge about the local geology and unplanned tubewell development. SASMIT, an initiative of KTH-International Groundwater Arsenic Research Group has developed a method for safe tubewell installation considering hydrogeological suitability, safe water access and other relevant social and demographic information into account.Piezometers installed at 15 locations over an area of 410 km2, using local boring techniques allowed to delineate the hydrostratigraphy, characterize the aquifers in terms of sediment characteristics, water chemistry and hydraulic head distribution, which ultimately led to the identification of the suitable aquifers for tapping safe water. The piezometer locations with safe drinking water quality were then targeted for safe well installation based on the determination of safe buffer distances in a cluster of a few villages (mouzas). Social mapping of all the villages within the mauzas were done using GIS to evaluate the availability of safe water options for a cluster of households (bari). For safe well installations, priority was given to regions with safe water access, greater number of beneficiaries especially in poor households, and easy access to the site from a cluster of households. Through this approach, it was thus possible to make 95% of the newly installed wells As-safe thus scaled up the safe water access upto 40% in some mauzas. Thus the as a strategy to improve safe water access, the SASMIT study recommends investigating the hydrogeological suitability through installation of few piezometers with a minimum effort and based on the results the implementation plan can be made using GIS based social mappings for relatively uniform distribution and to maximize the safe water access.
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| 8. |
- Jacks, Gunnar, et al.
(författare)
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Arsenic and its bioavailability in surface waters in a black schist area in northern Sweden
- 2012
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Ingår i: Understanding the Geological and Medical Interface of Arsenic, As 2012 - 4th International Congress: Arsenic in the Environment. - : Taylor & Francis Group. - 9780415637633 ; , s. 249-250
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Konferensbidrag (refereegranskat)abstract
- The Västerbotten county in northern Sweden is largely underlain by Precambrian bedrock. There are numerous sulfide ore bodies and gold deposits accompanied by arsenic. However, more black schists with a sulfur content of about 1% are a more widespread source of arsenic (As). The arsenic is accumulated in the B-horizon of tills but also remobilized in wetlands and released into surface water. Sandy sediments in brooks and streams may contain up to 500 mg/kg As adsorbed onto ferric (Fe) oxyhydroxides. Lakes may contain up to 19 ÎŒg/LAs. Speciation of As has been investigated in lake water by filtration and dialysis. Four lakes have been investigated varying from a clear-water lake to lakes high in Fe and DOC (dissolved organic carbon). The As is closely correlated to Fe in the different fractions. The fraction < 1 kDa is low in As indicating that the As has low bioavailability. Fishing is important in the area both for local people as well as for tourists. The low bioavailability of As is verified by a few analysis of fish, pike and trout, in which the As content is relatively low and consisting of predominantly organic species like MMA, DMA and arsenobetaine. Thus in spite of elevated As contents in sediments and in water the As does not seem to pose a health risk for fish consumers.
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| 9. |
- Kibria, M. G., et al.
(författare)
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Hydrogeochemistry and microbial geochemistry on different depth aquifer sediments from Matlab, Bangladesh
- 2014
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Ingår i: One Century of the Discovery of Arsenicosis in Latin America (1914-2014). - : CRC Press. - 9781138001411 ; , s. 101-103
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Konferensbidrag (refereegranskat)abstract
- Arsenic (As) poses the greatest hazard towards drinking water quality in Bangladesh. Tubewell drinking water is one of the main sources for household based water options in rural Bangladesh. Our study area is in Matlab Upazila, in Bangladesh. The overall objective of this research and the SASMIT project is to develop a community based initiative for sustainable As mitigation by developing a sediment color based tool for the local drillers prioritizing on the hydrogeological and biogeochemical investigations. For this purpose we analyzed different depth colored sediments and water for find out the sustainable low Arsenic contaminated aquifer.
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| 10. |
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| 11. |
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| 12. |
- von Brömssen, Mattias
(författare)
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Hydrogeological and geochemical assessment of aquifer systems with geogenic arsenic in Southeastern Bangladesh : Targeting low arsenic aquifers for safe drinking water supplies in Matlab
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Naturally occurring arsenic (As) in Holocene aquifers in Bangladesh have undermined a long success of supplying the population with safe drinking water. Arsenic is mobilised in reducing environments through reductive dissolution of Fe(III)-oxyhydroxides. Several studies have shown that many of the tested mitigation options have not been well accepted by the people. Instead, local drillers target presumed safe groundwater on the basis of the colour of the sediments. The overall objective of the study has thus been focussed on assessing the potential for local drillers to target As safe groundwater. The specific objectives have been to validate the correlation between aquifer sediment colours and groundwater chemical composition, characterize aqueous and solid phase geochemistry and dynamics of As mobility and to assess the risk for cross-contamination of As between aquifers in Daudkandi and Matlab Upazilas in SE-Bangladesh. In Matlab, drillings to a depth of 60 m revealed two distinct hydrostratigraphic units, a strongly reducing aquifer unit with black to grey sediments overlies a patchy sequence of weathered and oxidised white, yellowish-grey to reddish-brown sediment. The aquifers are separated by an impervious clay unit. The reducing aquifer is characterized by high concentrations of dissolved As, DOC, Fe and PO43--tot. On the other hand, the off-white and red sediments contain relatively higher concentrations of Mn and SO42- and low As. Groundwater chemistry correlates well with the colours of the aquifer sediments. Geochemical investigations indicate that secondary mineral phases control dissolved concentrations of Mn, Fe and PO43--tot. Dissolved As is influenced by the amount of Hfo, pH and PO43--tot as a competing ion. Laboratory studies suggest that oxidised sediments have a higher capacity to absorb As. Monitored hydraulic heads and groundwater modelling illustrate a complex aquifer system with three aquifers to a depth of 250 m. Groundwater modelling illustrate two groundwater flowsystems: i) a deeper regional predominantly horizontal flow system, and ii) a number of shallow local flow systems. It was confirmed that groundwater irrigation, locally, affects the hydraulic heads at deeper depths. The aquifer system is however fully recharged during the monsoon. Groundwater abstraction for drinking water purposes in rural areas poses little threat for cross-contamination. Installing irrigation- or high capacity drinking water supply wells at deeper depths is however strongly discouraged and assessing sustainability of targeted low-As aquifers remain a main concern. The knowledge gained here can be used for developing guidelines for installing safe wells at similar environments in other areas of Bangladesh.
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