Polluted Waters Bear Magnetic Signature

May 18, 2009 -- A new way to detect pollution magnetically could become a powerful tool for cleaning up the world's tainted waterways.

For thousands of years, man's mining and metalworking habits have produced toxic stews, many of which ran off into local rivers, lakes and harbors, where they settled and mingled with sediments. Only in recent decades, as large fish kills and choking algae blooms have fouled our water resources have we become aware of the massive ecological impact of sediment pollution.

But cleanup is expensive. Many contaminated sites in the United States remain untreated because the cost is simply too high. Many haven't even been adequately mapped.

Joseph Boyce of McMaster University in Canada and a team of researchers have come up with a way to identify contaminated sediments by their magnetic signature. By simply towing a magnetometer behind a boat, the team has shown they can scan the bottoms of harbors, lakes, and even entire coastlines for pollution, much like a treasure hunter sweeps a beach with a metal detector.

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The researchers will present their findings at the American Geophysical Union's joint assembly next week.

"The U.S. Environmental Protection Agency lists 42 areas of concern for sediment contamination in the Great Lakes alone," Joseph Boyce of McMaster University in Canada said. "These are places where sediments are so toxic they're impacting water quality, fish and vegetation."

The team tested the technique in Hamilton Harbor, an industrial hub on Lake Ontario lined with steel plants. Areas of the harbor with sediments deposited since the late 19th century -- when factories first settled the area -- were strongly magnetized, indicating the presence of the magnetic mineral hematite and other iron-rich compounds.