Earth system scientist Scott Fendorf (white shirt) poses with his team above a seasonal wetland that was dug out and flooded to simulate a permanent wetland environment.
Bacteria living in shallow sediment layers of permanently flooded wetlands in Asia drive arsenic release into water by feeding on freshly deposited plant material, a new study finds. Groundwater in South and Southeast Asia commonly contains concentrations of arsenic 20 to 100 times greater than the World Health Organization's recommended limit, resulting in more than 100 million people being poisoned by drinking arsenic-laced water in Bangladesh, Cambodia, India, Myanmar, Vietnam and China. Stanford scientists have solved an important mystery about where the microbes responsible for releasing dangerous arsenic into groundwater in Southeast Asia get their food. Their findings, published s , could guide future land management and future development. Arsenic is bound to iron oxide compounds in rocks from the Himalayas, and gets washed down the major rivers and deposited in the lowland basins and deltas. Scientists know that in the absence of oxygen, some bacteria living in those deposited sediments can use arsenic and iron oxide particles as an alternative means of respiration. When they do this, however, the microbes separate the arsenic and iron oxides and transfer the toxin into underlying groundwater.
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