Characterization of PM2.5 and PM10 near California Highways with a Focus on Non-Tailpipe Emissions
XIAOLIANG WANG, Steven Gronstal, Brenda Lopez, Heejung Jung, L.W. Antony Chen, Steven Sai Hang Ho, Judith Chow, John Watson, Chas Frederickson, David Mendez-Jimenez, Tianyi Ma, Ling Cobb, Qi Yao, Seungju Yoon,
Desert Research Institute Abstract Number: 307
Working Group: Source Apportionment
AbstractThis study evaluates the contributions of different sources, particularly vehicle non-tailpipe emissions, to particulate matter (PM) in near-road environments. PM
2.5 and PM
10 filter samples were collected near I-5 and I-710 in California over two weeks. Each sample was characterized for inorganic and organic species. The effective variance chemical mass balance (EV-CMB) model apportioned PM concentrations to different sources.
Average concentrations of PM
2.5 and PM
10 were 10-15 and ~30 µg/m
3, respectively. For PM
2.5, the most abundant components were: organic matter (OM; ~30–40%), mineral dust (~25–30%), and elemental carbon (EC; ~10–15%). For PM
10, mineral dust (~40–45%), OM (~25%), nitrate (~6-11%), and EC (6-8%) were the dominant component. EC concentrations near I-710 were 19-26% higher than those near I-5, likely due to more diesel vehicles on I-710. Average particulate PAH concentrations near I-710 were 47% higher than those near I-5, particularly for lower molecular weight PAHs. High correlations were found for elements with common sources, such as markers for brake wear and road dust.
Source apportionment shows that road dust was the largest near road PM source and it contributed more to PM
10 than to PM
2.5. On average, contributions of the non-tailpipe fractions (brake and tire wear) to PM
2.5 exceeded those of tailpipe fractions (diesel and gasoline emissions) at I-5 (~30% vs. 20%) while they were comparable at I-710 (15–17% vs. 15–19%). For PM
10, the non-tailpipe contributions were 2 – 3 times the tailpipe contributions. Brake wear particles were more abundant than tire wear particles, though there was a higher uncertainty in the tire wear contribution estimates. The I-710 samples found brake wear with a higher copper content than that found in I-5 samples, reflecting different fleet compositions.