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- Bhattacharya, Prosun, et al.
(författare)
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Natural arsenic in the groundwater of the alluvial aquifers of Santiago del Estero Province, Argentina
- 2005
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Ingår i: Natural Arsenic in Groundwater. - London : Balkema. - 041536700X ; , s. 57-65
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Konferensbidrag (refereegranskat)abstract
- Natural occurrences of arsenic has been documented in groundwater of the shallow aquifers of the Chaco-Pampean Plain, Argentina. The distribution of arsenic and mechanisms of its mobilization in the shallow alluvial aquifers was investigated around the city of Santiago del Estero in Northwestern Argentina in order to provide an insight into the complex hydrological and geochemical conditions that yields high As concentrations in groundwater. Significant spatial variations of total arsenic (As-tot) concentrations were observed with an average value of 743 mu g/L. Arsenate was a dominant species in most samples. Average concentrations of Al, Mn, and Fe were 360 mu g/L, 574 mu g/L, and 459 mu g/L, respectively. The 7M HNO3 extraction of sediments and volcanic ash-layer indicated AS(N03) concentrations ranging between 2.5-7.1 mg/kg. AS(N03) indicated a significant positive correlation with Mn-N03, Al-N03, and Fe-N03. Oxalate extractions revealed significant fractions of As (Aso(ox)) in the sediments (0.4-1.4mg/kg) and a dominance of oxalate extractable Al- and Mn. Speciation calculations indicate that Al oxide and hydroxides have the potential to precipitate in the groundwater, suggesting that As adsorption processes may be to some extent controlled by Al oxides and hydroxides. Mobility of As at local scale seems to depend on high pH values, related to the dissolution of carbonates driven by cation exchange, and dissolution of silicates. There is a clear relationship of As with F, V, B and Si, suggesting their common origin in volcanic ash layer. Preliminary conceptual model of arsenic input includes release of As and Al from dissolution of volcanic ash layer, precipitation of Al oxides and hydroxides followed by adsorption of As on Al and Fe phases in sediments, and release of As under high pH conditions.
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| 2. |
- Jakariya, Md., et al.
(författare)
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Sustainable safe water options in Bangladesh : experiences from the Arsenic Project at Matlab (AsMat)
- 2005
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Ingår i: Natural Arsenic in Groundwater. - LEIDEN : A A BALKEMA PUBLISHERS. - 041536700X ; , s. 319-330
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Konferensbidrag (refereegranskat)abstract
- The presence of elevated levels of naturally occurring arsenic in groundwater of Bangladesh, has severely impaired the decade long effort of providing safe water to nearly 98% of its population and putting an estimated 3 5 million people-nearly one fourth of the total population at risk. In order to address this problem, a project titled "Arsenic in tubewell (TW) water and health consequences in Matlab Upazila of Chandpur district (AsMat)" is being implemented jointly by ICDDR,B and BRAC. During this study. all the TWs in Matlab have been assigned unique identification numbers, with marked GPS coordinates, depth, and age. It is estimated that nearly 65% of the about 13,000 TWs in Matlab have As concentrations above the Bangladesh drinking water standard (50 mu g/L). In order to minimize arsenic exposure, a work to provide various alternate safe drinking water options to the exposed population has been initiated. As of March 2004, about 1047 different alternate safe water options, such as Pond Sand Filter (PSF), Rainwater Harvester (RWH) and different filters to remove arsenic as well as pathogenic bacteria, were distributed among the targeted exposed population in Matlab. To ensure sustainable use, the provided options were assessed based on community acceptability, technical viability, and financial viability.
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| 3. |
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| 4. |
- Tandukar, N., et al.
(författare)
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Naturally occurring arsenic in groundwater of Terai region in Nepal and mitigation options
- 2005
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Ingår i: Natural Arsenic in Groundwater. - London : Taylor & Francis Group. - 041536700X ; , s. 41-48
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Konferensbidrag (refereegranskat)abstract
- Natural arsenic (As) was detected in groundwaters in the Terai Alluvial Plain (TAP) in southern Nepal in the year 1999. By the end of March 2004, about 245,000 wells have been tested for As, out of which about 3% samples are found to have exceeded Interim Nepalese Standard of 50 mu g/L. From the detail study conducted in hotspot district Nawalparasi, natural rocks are thought to be the sources of As that are leached mainly due to the weathering of As bearing minerals from the Himalayas towards the northern Nepal. In this paper, the chemistry of groundwater from highly arsenic affected Nawalparasi district in the central part of the TAP in southern Nepal has been presented. TA-P groundwaters are found to be predominantly of reducing character with low SO42- and NO3-, but high HCO3- concentrations. Total arsenic (As-tot) concentration in groundwater varied from 1.7 mu g/L to as high as 404 mu g/L. As(III) species is found to be predominant along with elevated levels of dissolved Fe and Mn. The correlation between DOC, HCO3-, Fe-tot and As-tot strongly supports the hypothesis of reductive dissolution of Fe-oxyhydroxides as the main mechanism of mobilization of As in groundwater in TAP. Blanket testing by As-field test kits is the easiest way to find out As free sources nearby for tubewell switching. In the absence of As-free source, the only available option is the treatment of water either at the point of entry or at the point of use to meet the drinking water standard. DWSS in collaboration with UNICEF and WHO is conducting blanket testing of As in 10 Terai districts. Based on the blanket test result, As treatment methods such as 3-gagri filter, arsenic biosand filter etc., which are simple, effective, affordable and socially acceptable will be provided as a short-term option to the affected communities in hotspot areas.
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