Abstract for presentation at 14th IUAPPA World Congress

Exhaust emissions from motor vehicles vary greatly and depend on factors such as engine operating conditions, fuel, age, mileage and service history. As such, a new method has been devised to rapidly identify high-polluting vehicles as they travel on the road. By monitoring emissions from a large number of vehicles in a short period of time, it avoids the need to conduct expensive and time consuming tests on chassis dynamometers.
A sample of the exhaust plume is captured as each vehicle passes a roadside monitoring station and the pollutant emission factors are calculated from the measured concentrations using carbon dioxide as a tracer. Although similar methods have been used to monitor soot and gaseous mass emissions to-date, it has not been used to monitor particle number emissions from a large fleet of vehicles. This is particularly important, as epidemiological studies have shown that particle number concentration is an important parameter in determining adverse health effects.
The method was applied to measurements of particle number emissions from individual buses in the Brisbane City Council diesel fleet operating on the South-East Busway. The results indicated that the particle number emission factors are gamma- distributed, with a high proportion of the emissions being emitted by a small percentage of the buses. Although most of the high-emitters were the oldest buses in the fleet, there were clear exceptions, with some newer buses emitting just as much. This was attributed to their recent service history, particularly pertaining to the improper tuning of the engines. A targeted correction program is therefore recommended as a highly effective measure in mitigating urban environmental pollution.