posted on 1997-11-26, 00:00authored bySteven H. Cadle, Patricia A. Mulawa, James Ball, Claudia Donase, Arnie Weibel, John C. Sagebiel, Kenneth T. Knapp, Richard Snow
One hundred three in-use vehicles identified as high
hydrocarbon and/or carbon monoxide emitters by remote
sensing and roadside visual, underhood checks during
a 1995 South Coast Air Quality Management District program
were tested on the IM240 cycle using a transportable
dynamometer. Seventy-one of these vehicles were
repaired
as part of the program and were retested. Seventeen
vehicles in the fleet initially emitted visible smoke from
the
tailpipe and were classified as “smokers”. The
fleet
ranged in age from 6 to 22 years, with a median age of
12.3
years. Exhaust HC, CO, NOx, and particulate
emissions (PM-10) were measured. PM-10 mass and the elemental and
carbonaceous composition of the particulate matter were
determined. The average fleet PM-10 emission rate was
0.138 g/mi, while the average emission rate for smokers
was 0.395 g/mi. It was concluded that the casual
observation
of smoking vehicles was not very successful in identifying
high PM-10 emitting vehicles. The particulate matter
composition was primarily carbonaceous, with a variable
distribution between the elemental and organic carbon
fractions, and showed no significant difference in the
percent
organic carbon fraction between smokers and non-smokers.
The PM composition differed, on average, between
pre-repair and post-repair samples. The effect of the
California Smog Check repair program on PM emission rates
could not be evaluated due to concerns regarding the
effect of vehicle conditioning on these measurements.