The Arsenic Contamination of Drinking & Ground Water in Bangladesh:Biogeochemical Aspects & Implications on Public Health

Michael Raessler

Organization(s): MPI Biogeochemie, Germany

Arsenic is one of the most widespread contaminants of drinking and ground waters in the world. These contaminations may be of anthropogenic, but also of geogenic origin which seemed to be particularily true for the Bengal delta most of which is part of Bangladesh. About 150 million people in Bangladesh and the Indian province of West Bengal are in danger of consuming drinking water with arsenic concentrations of ≥ 50 µg/L. The arsenic is being dissolved from the aquifer by biogeochemical processes. Its transport is ruled by chemical transformations and the properties of the arsenic species formed. Primary sources of arsenic in the Bengal delta are As-bearing ores, such as FeAsS, from the Himalaya, the weathering of which releases sulfate, As (III) and Fe (II). The latter is readily oxidized to Fe (III), precipitating as iron oxyhydroxides and adsorbing As (V) which is slowly formed from As (III) by action of oxygen. On the other hand, presence of high amounts of organics in the Bengal delta sediments, favours dissolution of arsenic as As (III). Microbial oxidation of organic matter, including peat layers, and reductive dissolution of iron and manganese oxyhydroxides are the important processes to mobilize arsenic most of which is present as arsenite in groundwaters of Bangladesh. Today, microbially mediated oxidation of organic carbon is thought to drive the geochemical transformations that release arsenic from sediments, but the source of the organic carbon that fuels these processes remains controversial. It has been found that arsenic mobilization is driven by the recharge through anoxic pond sediments and anoxic sediments of wetlands, respectively. This is fueled by the portion of biologically degradable organic carbon (BDOC), whereas recalcitrant organic carbon has little or no influence on arsenic mobilization.

Michael Raessler

Michael Raessler (M.R.) studied Chemistry in Munich and Kiel. After his diploma he joined the former GSF Research Centre for Environment and Health, Institute of Ecological Chemistry, at Neuherberg near Munich (nowadays Helmholtz-Zentrum München), where he was working on the speciation of both arsenic and selenium in environmental samples.

M.R. obtained his Ph.D. in Analytical Chemistry and Environmental Analytics from the TU Munich. In 1997, M.R. launched the department of Inorganic Chemical Analytics at the Max Planck Institute for Biogeochemistry in Jena, which he headed until 2005.

Since then, he is heading the SpecLab department (including Atomic Spectroscopy, Sample preparation techniques, Analytical method development and - last, but not least - Carbohydrate Analysis in Plant Samples of various origins.

.R. authored and co-authored more than 25 articles.