A group of Dartmouth researchers studying the concentrations of toxic metals at the former Coakley Landfill in North Hampton, N.H. has found that while the level of iron and some other contaminants decreased, the level of arsenic slightly increased. The researchers detailed their calculations regarding the geochemical processes at this site over the last years in a paper published online on November 23 by Environmental Science and Technology, a journal of the American Chemical Society.
Their research could shed light on how arsenic pollutes groundwater near landfills, especially in areas where the landfill's organic material mixes with naturally occurring iron oxides. This process also may explain the high level of arsenic in drinking water in Bangladesh and other areas of Southeast Asia.
"Unfortunately, arsenic appears to come from the interaction of microbes with iron oxides carrying arsenic in the underlying rocks," says Benjamin Bostick, a coauthor on the paper and assistant professor of earth sciences. "In the Coakley Landfill, it appears that these microbes increase arsenic concentrations by consuming organic wastes and creating a 'reducing condition' where the oxygen concentration is very low, which is conducive to arsenic release. We think that arsenic contamination caused by the natural degradation of other toxic organic material might be widespread."
The Coakley Landfill was listed in 1986 as an Environmental Protection Agency Superfund Site because of hazardous waste content. The area was capped in 1998, a procedure common in the rehabilitation of landfills. With data collected since 1994, the researchers were able to tie changes in arsenic levels over time to the degradation of benzene and other organic wastes.
Funding for this research was provided by the U.S. National Institutes of Environmental Health Sciences Superfund Basic Research Program and the National Science Foundation.
By SUSAN KNAPP
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Last Updated: 12/17/08