Arsenic contamination lacks one-size-fits-...( MADISON - Though a worldwide problem...)

MADISON - Though a worldwide problem, arsenic contamination of drinking water does not have a universal solution.

Instead, recent work by University of Wisconsin-Madison researchers on arsenic-tainted wells shows that appropriate treatment varies depending on the source of the contamination.

Naturally occurring arsenic in rocks is usually associated with sulfur- or iron-rich minerals, where it poses no threat to groundwater, explains lead researcher Madeline Gotkowitz, a hydrogeologist at the Wisconsin Geological and Natural History Survey.

Once it is released from mineral form into groundwater through geochemical or biological processes, however, chronic exposure to arsenic has been linked to skin lesions and increased risk of several cancers. The issue has gained international prominence in Southeast Asia but affects populations around the world.

"It's stunning how many people worldwide are affected by toxic levels of arsenic," Gotkowitz says. "There are thousands upon thousands of people who become ill from having their drinking water contaminated with arsenic."

Though on a smaller scale, arsenic-tinged groundwater is a problem in parts of the United States as well, including regions in the Northwest, East and Midwest.

Management practices in Wisconsin have been complicated by two competing sources of soluble arsenic, Gotkowitz says. Arsenic associated with sulfide minerals in rock can be released by the weathering effects of oxygen-rich environments.

Alternately, arsenic bound to iron oxides can be released by iron-reducing bacteria, which thrive in low-oxygen conditions. "There is different geochemistry in different [areas]," Gotkowitz says. "That makes it a harder nut to crack. ... People might have a similar symptom - arsenic in their water - but there are different solutions because the geologic environment is quite different."

In Wisconsin, groundwater arsenic affects some munic
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