McMaster geology professors Bill Morris and Joe Boyce are “thinking dirty” these days  dirty sediment that is. “Strong magnetic sediments are sitting on the bottom of Hamilton Harbour,” says Morris. “Development of a remediation strategy requires a solid understanding of the depth and distribution of these contaminants.”

For years, Ontario's Great Lakes have been treated as a convenient dumping site for waste materials. With a long history of industrial activity and urban development, the harbour is considered a pollution “hot spot.”

Beneath the waves, many of us never see the effects of pollution. Substances like oil, plastics, sewage, industrial chemicals and even pesticides all harm life in and around the lake. Previous studies by Morris have shown that these polluted sediments are commonly characterized by an increased magnetic signal.

Morris and Boyce, along with graduate student Matt Pozza, will be heading out on the lake on Aug. 22-24 to make the not so apparent, much more visible. They will be measuring the magnetic intensity across the harbour bed to determine the thickness and extent of the pollution particles that make up the core of the lake bed.

The scientific data will be collected by a marine magnetometer which looks like a torpedo. Towed behind a boat, the immersed apparatus sees everything magnetic underneath the lake bed to a depth of up to eight kilometres. What it registers is logged as digital data which is then converted to multi-coloured contour maps. Laboratory processing of the information permits the scientists to separate signals from shallow and deep-seated sources.

“The immediate results help to identify the areas and extent of contamination in urban harbours, as well as determine the sources of pollution and sediment disturbance. More important, the project will help us to develop a model to determine the ramifications of sediment disturbance. The latter can have a huge impact on remediation strategy, such as topping the lake bed with clean sand,” say Boyd and Morris.

“The pollution problems we are facing in our urban environment are so complex, it takes a cross-disciplinary approach to understand and find solutions for them,” adds Morris. “I'm sure the data we collect on this project will have other scientific spinoffs.” Further analysis of the data will be required to draw more detailed results.

Funded by the Centre for Research for Earth and Space Technology, the project is a collaboration between the government agency and McMaster University's School of Geography & Geology. The Hamilton project could eventually lead to a study of contaminated sediments in other areas around the Great Lakes.