Datta said that some of the wells that the researchers tested have 30 times more arsenic than is accepted by the World Health Organization and the U.S. Environmental Protection Agency. Datta said the effects of arsenic in groundwater aren't apparent immediately but rather build up over time. It causes skin lesions and skin cancer that spreads to other parts of the body. It can lead to paralysis and organ failure.
"Technically this is a natural source of pollution," Datta said. "The major hypothesis is that the Himalayan river systems that feed the Ganges-Brahmaputra-Meghna delta have been carrying down sediments that are the major source of arsenic. These sediments in the form of specific minerals and in the right environmental conditions trigger the release of arsenic into the groundwater."
The researchers suggest that as the arsenic-rich water enters the river, the chemistry causes it to precipitate and adhere to iron-bearing minerals in the sediments.
In effect, they said, the sediments form an "iron curtain" to keep the arsenic out of surface water in the river. But recycling of these arsenic-laden sediments to the Ganges-Brahmaputra-Meghna delta aquifer may lead to further groundwater contamination.
Datta is collaborating with Karen Johannesson at Tulane University and John F. Stolz at Duquesne University. Results of studies by Datta and Columbia University researchers in the Meghna River in Bangladesh appeared Oct. 6 in the journal Proceedings of the National Academy of Sciences. Neal presented their research at the Geological Society of America meeting Oct. 18-21 in Portland, Ore.
|Contact: Saugata Datta|
Kansas State University