Feb. 17, 1998 To most people, winter road salt is not one of Toronto's bragging rights. But to U of T researchers, road salt in Toronto -- specifically in the Don River -- is the key to a better understanding of arsenic and its mobility and toxicity in the environment.
Professor Miriam Diamond of geography and graduate student Mehran Monabbati of chemical engineering and applied chemistry have found the perfect location for their research. "We [in Ontario] apply a lot of salt on our roads, with Toronto alone using 150,000 tonnes a year," says Diamond. "The nearby Don Valley River becomes very salty because snow and salt drain into the riverway and that's how the two substances mix."
Much of the arsenic that is polluting water in North America has been dislodged during mining operations, says Diamond. When open pit mines are abandoned, they fill with rain and ground water, a process that releases the ground's naturally occurring arsenic into creeks and rivers. It is then absorbed by algae which transports it to the bottom where it stays until dislodged into the water again. The whole cycle repeats itself time and again.
Arsenic, Diamond says, can change form and become a sort of different "species," depending on the substances into which it comes in contact during its travels. A dangerous species can change into a less dangerous species and vice versa.
In initial lab results, the researchers found that road salt may extract arsenic out of the sediment at the bottom of rivers and lakes where arsenic is embedded. They presented their results to The Society of Environmental Toxicology and Chemistry in San Francisco in November.
Professor Miriam Diamond
Department of Geography
(416) 978-1586 or 978-1749
U of T Public Affairs
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