India, Bangladesh: bacteria responsible for arsenic in ground water

UK researchers claim to have identified the process responsible for contaminating groundwater with arsenic, a phenomenon that endangers the health of tens of millions of people, mostly in Bangladesh and India [1]. Their findings could help identify areas at risk, and eventually lead to ways of cleaning up contaminated water. Bacteria were found to be responsible for the release of arsenic into water from surrounding earth. The microbes gain energy by changing the chemistry of minerals containing both iron and arsenic, and release the arsenic into the water as a by-product of the reaction. Without such bacterial activity, the arsenic would remain in an insoluble form, and thus be unable to contaminate the water. The researchers collected earth samples at a depth of 13 metres from a site in West Bengal, India, known to have relatively high concentrations of arsenic in the water. The samples were mixed with groundwater in a laboratory and exposed to a range of biological, geological and chemical factors. The scientists found that arsenic was only released from the earth samples in the absence of oxygen, and that the presence of organic matter, derived from decaying animal and plant life, enhanced this process.

[1] Islam, F.S. ... [et al.] (2004). Role of metal-reducing bacteria in arsenic release from Bengal delta sediments. Nature, vol. 430, no. 6995 ; p. 68-71. http://dx.doi.org/10.1038/nature02638

Contact: Jonathan R. Lloyd, Dept. of Earth Sciences and Williamson Research Centre for Molecular Environmental Science, University of Manchester, jon.lloyd@man.ac.uk, http://www.earth.man.ac.uk/general/people/bio.ph...

Source: SciDev, 1 Jul 2004

Keywords

• Water-related diseases
• Water quality