Are emissions of black carbon from gasoline vehicles underestimated? Insights from near and on-road measurements.
Measurements of black carbon (BC) with a high-sensitivity laser-induced incandescence (HS-LII) instrument and a single particle soot photometer (SP2) were conducted upwind, downwind, and while driving on a highway dominated by gasoline vehicles. The results are used with concurrent CO(2) measurements to derive fuel-based BC emission factors for real-world average fleet and heavy-duty diesel vehicles separately. The derived emission factors from both instruments are compared, and a low SP2 bias (relative to the HS-LII) is found to be caused by a BC mass mode diameter less than 75 nm, that is most prominent with the gasoline fleet but is not present in the heavy-duty diesel vehicle exhaust on the highway. Results from both the LII and the SP2 demonstrate that the BC emission factors from gasoline vehicles are at least a factor of 2 higher than previous North American measurements, and a factor of 9 higher than currently used emission inventories in Canada, derived with the MOBILE 6.2C model. Conversely, the measured BC emission factor for heavy-duty diesel vehicles is in reasonable agreement with previous measurements. The results suggest that greater attention must be paid to black carbon from gasoline engines to obtain a full understanding of the impact of black carbon on air quality and climate and to devise appropriate mitigation strategies.
Atmospheric Science and Technology Directorate, Science and Technology Branch, Environment Canada, 4905 Dufferin Street, Toronto, Ontario M3H 5T4 Canada. john.liggio@ec.gc.ca
John
J
Liggio
Mark
M
Gordon
Gregory
G
Smallwood
Shao-Meng
SM
Li
Craig
C
Stroud
Ralf
R
Staebler
Gang
G
Lu
Patrick
P
Lee
Brett
B
Taylor
Jeffrey R
JR
Brook
D049450:Incandescence; D007834:Lasers; D009864:Ontario; D053260:Soot / Q000032:analysis*; D001335:Vehicle Emissions / Q000032:analysis*
D053260:Soot; D001335:Vehicle Emissions