"The work shows that nitrate pollution, which arises from sources such as automobile exhaust, wastewater disposal and fertilizers, is more important in lake dynamics than had been thought," said Harry Hemond, the Leonhard Professor of Civil and Environmental Engineering and an author of a paper on the work that appeared in the June 28 issue of Science. "This is a linkage we need to understand if we want to manage water quality."
In an interesting twist, said Hemond, the nitrate pollution, which is also associated with noxious impacts such as excessive algal growth, was found to have a mitigating effect. It reacts with naturally occurring iron to create iron oxides that in turn adsorb arsenic. "The result is a suppression of seasonal arsenic release into the water," said Hemond, who is director of MIT's Parsons Laboratory.
Hemond and co-author David Senn (Ph.D. 2001) focused their studies on the Upper Mystic Lake. U.M.L. is part of the Aberjona Watershed, a 25-square-mile drainage basin that includes parts of seven Massachusetts communities (Woburn, Winchester, Wilmington, Lexington, Burlington, Reading and Stoneham).
For over a century, hundreds of tons of toxic wastes from leather, chemical and other industries were dumped into the waterways of the Aberjona, the real-world setting of the movie "A Civil Action." Today the dumping has stopped, but the pollutants--including considerable amounts of solvents, chromium and arsenic--remain. For the last 14 years MIT researchers have been exploring the fate of these wastes and the chains of events that can lead to effects on human health.
The work reported in Science began with a mystery. Iron and arsenic in water sampled from the depths of U.M.L.
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Contact: Elizabeth Thomson
thomson@mit.edu
617-258-5402
Massachusetts Institute of Technology
29-Aug-2002