Arsenic mitigation by developing a tool based on gray and brown sediment solid phase characterization
2013 (English)Conference paper, Abstract (Refereed)
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 local drillers in this area are the only ones who have been utilized by the community to identify safe aquifer depths. The overall objective of this 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 geochemical investigations as to (a) why red/brown to off-white sediments produces As-safe water but contains high Mn; (b) as to why light gray sediment produce low As and Mn free water; and (c) why dark gray sediments produce high As bearing water. Shallow tubewells excepting those installed within off-white sediments are mostly contaminated with high As. High Mn in many wells is also an additional problem in some shallow aquifer depths. In our field studies we find the wells installed within light grey medium sand the As concentration was found below 50μg/L and Mn is within WHO guideline value of 0.4 mg/L.
This study focuses on the adsorption behavior of oxidized reddish-red-brown sediments from Matlab region, and their capacity to attenuate As. Sediment extractions indicate a relatively low amount of As in the oxidized sediments. Reductive dissolution of Fe(III)-oxyhydroxides and release of its adsorbed As is considered to be the principal mechanism responsible for mobilization of As. Groundwater abstracted from oxidized reddish sediments, in contrast to reducing grayish sediments, contains significantly lower amount of dissolved As and can be a source of safe water. This study describes the lithofacies, mineralogy and results of adsorption experiments on the sediments within ~85m depth and establishes a relationship between aqueous and solid phase geochemistry along these intermediate depths of the aquifer.
Core samples have been analyzed by petrographic microscopy, microtopography and distribution of elements within sediment grains by FESEM-EDX and clay and bulk mineralogy by XRD. Synchrotron aided μXANES and μXRD studies conducted for solid state As speciation (As3+ and As5+) in different depth core samples. The projected outcome is to incorporate detailed sediment characteristics of the different aquifers including all possible color variations available in the exploited intermediate depths within Matlab. This study would have a wider implication towards a broader scale regional remediation project that incorporates the enquiry of efficiency of sediment color as a simple and easy tool for identifying safe aquifers in major As risk prone areas. Knowing sediments more accurately would also enrich and strengthen the field based tools for identifying As-safe and As-Mn safe aquifers for tubewell installation.
Place, publisher, year, edition, pages
Athens, Georgia, 2013.
IdentifiersURN: urn:nbn:se:kth:diva-124513OAI: oai:DiVA.org:kth-124513DiVA: diva2:635912
12th International Conference on the Biogeochemistry of Trace Elements (ICOBTE), June 16-20, Athens, USA
FunderSida - Swedish International Development Cooperation Agency
QC 201406242013-07-072013-07-072014-06-24Bibliographically approved