Particulate emission rates from light-duty vehicles in the South Coast air quality management district

This paper presents the results of a particulate emission rate study conducted on 129 light-duty gasoline and 19 light-duty diesel vehicles for the Coordinating Research Council's (CRC's) Project E-24-2. Total particulate emission rates for newer gasoline vehicles were low (<3 mg/mi) with modest increases with vehicle age and older technology. Average FTP particulate emission rates as a function of model year for gasoline vehicles were found to be 2.5 mg/mi for 1991 and newer models, 14.4 mg/mi for 1986-1990 models, 49.0 mg/mi for 1981-1985 models, and 33.8 mg/mi for 1980 and older models. High gaseous emitters were found to have approximately 5-10 times the particulate emission rates of normal emitters. The diesel vehicles had an average particulate emission rate of 561 mg/mi. It should be noted that the light-duty diesel Vehicles were predominantly older, pre-1985 vehicles; the 1985 and newer diesel Vehicles had substantially lower particulate emissions, i.e., less than 100 mg/mi. Emission inventory estimates in the South Coast Air Basin based an the fleet emission rates were higher (3.42 tons/day of PM for light-duty passenger cars) than those obtained using the default values in EMFAC7G (1.96 tons/day of PM), due primarily to the contribution of high emitters.