Pollutants journey from Sahara to Toronto streets

The science of tracing the source of pollutants is becoming more precise, thanks to advanced technology and the efforts of engineering and science researchers.
A team led by Greg Evans, a professor in the Department of Chemical Engineering and Applied Chemistry at the University of Toronto, managed to detect migratory pollutants from a forest fire in Quebec in air on College Street in Toronto. They even found particles from a sandstorm in the Sahara in samples taken from the Toronto site.
To identify the particles, the researchers used a laser ablation mass spectrometer (LAMS), which is able to find the chemical signature using high powered lasers.
Identifiying the migratory source, though, is more like detective work. In a report in the University’s Science and Technology News, Professor evans explains how they discovered the Quebec and Sahara Desert trail: “We happened to know when that forest fire was happening in Quebec and we realized that this mixture of different particles that we found in downtown Toronto is a signature for a forest fire.” As for the dust particles from the Sahara, they recognized the particles and were able to track their trajectory from the desert, across the Atlantic Ocean to Mexico, then north through the U.S. to Toronto.
Source: news@UofT. Article by Nicolle Wahl, dated october 19, 2004.