Tapped Tailpipes Help Profile Particles

When vehicles burn fossil fuels, they emit a mixture of gaseous chemicals and particulate matter into the air. Some of these chemicals—such as oxides of nitrogen (NO_x), sulphur dioxide and volatile organic compounds (VOCs)—also form fine particles when they react in the atmosphere. Studies suggest that the smaller these particles are, the deeper they can be inhaled into the lungs and the greater their effect on respiratory and other health problems.

Although scientists have been measuring the mass concentration of particles in the air for more than a decade, growing interest in developing air quality standards for this form of pollution has spurred the need for more specific information about how it is formed, what it is made of, and where it comes from.

To answer these questions, scientists with Environment Canada (EC), Health Canada, the National Research Council and Natural Resources Canada launched a three-year project in 1998 to study fine particulate matter from the transportation sector—the largest human-made source of NO_x and VOCs in Canada. The project, which focuses on cars and trucks, was recently extended for another four years with plans to include other transportation sources such as off-road vehicles.

The project is aimed at developing detailed emissions profiles—including chemical make-up and size distribution—of fine particulate matter emitted from motor vehicles. By also collecting and analyzing ambient air samples, scientists can then use these profiles to calculate what percentage of atmospheric particle loading in populated areas is due to transportation, and what percentage of this is formed through atmospheric reactions. This knowledge is being used to develop models for forecasting how atmospheric loading would change as a result of different policies on transportation or transportation fuels.

Environment Canada developed sample collection and chemical analysis methods for both the source and ambient particulate matter, and spent last year testing these techniques in the lab and in the field. The Department's Environmental Technology Centre collected emission samples in its Ottawa lab from cars, light-duty trucks, buses and, for the first time, motorcycles. The Centre's technicians also spent five weeks in Vancouver measuring particle and gaseous emissions from more than 75 in-use vehicles at the BC Air Care Centre. The vehicles, which ranged from 1978 to 1998 models, were also checked for differences in the grade, brand and sulphur content of their gasoline.

Early results indicate that, in general, older cars emit more particles than newer ones, that oil-burning vehicles produce very high quantities of particles, and that well-maintained vehicles emit less than others. This year, the team will concentrate on completing analyses of the data collected last year, and has proposed collecting samples from new low- and ultra-low-emission vehicles as well.

Air-quality experts from EC's Meteorological Service of Canada tested their ambient air collection and chemical analysis techniques in studies in Toronto and southern Ontario last summer, and will be doing similar studies in Toronto and Vancouver over the next two years. One part of the Vancouver program will be a tunnel study, in which the ambient air at the entrance and exit of road tunnels is analyzed and results are used to determine particles and other chemicals emitted over a certain time or distance by a given number of vehicles. The Department is also working with atmospheric chemists from several Canadian universities, who are developing new sampling and analysis technologies and studying the transformation of gaseous chemicals in the atmosphere.

By synthesizing this information into computer models that simulate the formation and deposition of fine particulate matter and forecast the effects of possible changes in policies and transportation use, Environment Canada's scientists are helping identify effective strategies for controlling the formation of particles and ground-level ozone. The next area that needs to be looked at is stationary sources such as incinerators and coal-fired power plants, and their relative contributions to particulate matter and other forms of urban air pollution.

  Home |  Air |  Atmospheric Science |  Climate Change |  Environmental Action |  Habitat |  Pollution |  Species at Risk |  Technology |  Water |  Weather |  Wildlife