| 1. |
- Bhattacharya, Prosun, 1962-, et al.
(författare)
-
Arsenic in Groundwater of Bangladesh : Options for Safe Drinking Water
- 2010
-
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.
|
|
| 2. |
- Bhattacharya, Prosun, 1962-, et al.
(författare)
-
Arsenic in Swedish groundwater Mobility and risk for naturally elevated concentrations : Final Report
- 2010
-
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.
|
|
| 3. |
- Hossain, Mohammad, et al.
(författare)
-
Strategic approach for up-scaling safe water access considering hydrogeological suitability and social mapping in Matlab, southeastern Bangladesh
- 2013
-
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.
|
|
| 4. |
|
|
