Assessment of contaminant loadings in lake sediments using magnetic property measurements

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The remediation of contaminated sediments in the Great Lakes is recognized by Canadian and US regulatory agencies as an urgent environmental priority. 42 Areas of Concern (AOC's) have been identified where lake-bottom sediments are contaminated to toxic levels by heavy metals, hydrocarbons and a range of other environmental pollutants. Once buried in sediments, these contaminants can persist for many decades and pose a serious long-term threat to human health and aquatic ecosystems. McMaster researcher Boyce and his graduate students are assisting in remediation efforts by developing new methods for mapping contaminated sediments based on their magnetic properties. Their preliminary work in Lake Ontario has shown that toxic sediments are often more highly magnetized than clean sediments and can be identified and mapped by towing a magnetic sensing device called a magnetometer above the lakebed. Measurement of the magnetization of sediment core samples can also provide rapid 'proxy' measurements of pollutant levels without the need for expensive and time-consuming chemical testing. Further work is now required to develop magnetic methods for pollution monitoring. With NSERC's support, Boyce and his team plan to investigate how magnetic particles and contaminants are transported into lake basins and to develop new methods for 'magnetic finger-printing' of pollution sources. The research will lead to a more rapid and effective approach for mapping contaminants in lakes and will accelerate ongoing international efforts to remediate sediments in several heavily polluted AOC's within the Great Lakes.