Solutions to Arsenic Groundwater Contamination
Alexander van Geen, Ph.D.,
Columbia University
NIEHS Grant P42ES010349
According to the World Health Organization, approximately 60 million people living in Bangladesh, or about half the population, drink water contaminated with unsafe levels of arsenic defined as greater than 10 micrograms per liter. The contamination puts people at high risk for cancer, diabetes, and other serious diseases. Arsenic contamination is also a serious problem in Cambodia, China, India, Myanmar, Nepal, Pakistan, and Vietnam.
In Bangladesh, wells that tap into deep aquifers are typically uncontaminated and are safe to drink. However, in recent years, farmers have started to drill deep wells for irrigation, which can compromise access to clean drinking water across the country. Irrigation wells pump high enough volumes of water to pull down arsenic-contaminated water nearer the surface and jeopardize the quality of water in the deep aquifer.
The source of the arsenic in the water was identified in the 1990s. The Himalayan mountain range has rocks and sediments that naturally contain arsenic. As these sediments move downstream in four major river basins, bacteria cause arsenic to be released from the solid material into a soluble, toxic form that works its way into shallow aquifers. Surface waters in these areas are often contaminated with disease causing bacteria and pathogens.
Research shows that relatively small amounts of arsenic wind up in rice grains grown in irrigated paddies. Therefore the scientists recommend using only deep aquifers for drinking and shallower wells for irrigation. In other areas where deep aquifers don't exist, filtration is used to remove arsenic from the water. This practice requires constant testing of the water to ensure that the filter is working properly, a process that doesn't occur as often as it should according to the researchers. They recommend a vigorous, recurring testing program of wells in the region and preserving deep wells for drinking water instead of irrigation. They also recommend additional research into the use of rain water harvesting and filtration.
Citation: Fendorf S, Michael HA, van Geen A. Spatial and temporal variations of groundwater arsenic in South and Southeast Asia. Science. 2010 May 28;328(5982):1123-7.
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