A21A-0094
SECONDARY ORGANIC AEROSOL FORMATION FROM ULTRA-LOW, SUPER ULTRA-LOW AND PARTIAL ZERO EMISSION VEHICLE EXHAUST
Tuesday, 15 December 2015
Poster Hall (Moscone South)
Yunliang Zhao1, Andrew T Lambe2, Rawad Saleh3, Georges Saliba3, Hector Maldonado4, Satya Sardar4, Bruce Frodin4, Greg Drozd5, Allen H Goldstein5, Jesse H Kroll6, Eben S Cross6, Jonathan P Franklin6 and Allen L Robinson1, (1)Carnegie Mellon University, Pittsburgh, PA, United States, (2)Aerodyne Research Inc., Billerica, MA, United States, (3)Carnegie Mellon University, Center for Atmospheric Particle Studies, Pittsburgh, PA, United States, (4)California Air Resources Board, Sacromento, United States, (5)University of California Berkeley, Berkeley, CA, United States, (6)Massachusetts Institute of Technology, Cambridge, MA, United States
Abstract:
Secondary organic aerosol (SOA) is the dominant component of organic aerosol in many urban areas during the summertime. On-road light duty gasoline vehicles (LDGV) have been indicated as a major source of SOA precursors. Emissions of the SOA-forming non methane hydrocarbons (NMHCs) from on-road LDGV have been substantially reduced along with more stringent emission standards, leading to reduced potential for SOA formation. However, recent smog chamber measurements reported that the reductions in SOA formation were less than those in NMHC emissions, indicating that newer, low emitting vehicles may emit a more efficient of SOA precursors. Vehicles that meet the ultra-low, super ultra-low and partial zero emission standards have substantially lower NMHC emissions than vehicles tested in past studies. To better understand the effects of more stringent emission controls on the SOA formation, we conducted experiments 13 vehicles recruited from the Southern California vehicle fleet (five ultra-low emission vehicles, four super ultra-low emission vehicles and four partial zero emission vehicles) at the California Air Resources Board Haagen-Smit Laboratory. In addition, we investigated several vehicles compliant with older emission standards have also been investigated here to bridge the previous studies. Dilute vehicle exhaust were photo-oxidized in a smog chamber with the VOC-to-NOx ratio adjusted to simulate the photochemistry in urban air. Application of literature data from single-ring aromatic compounds cannot explain the observed SOA during chamber experiments. The average ratios between estimated and measured SOA for vehicles under different emission standards ranged from 0.04 to 0.71. Comprehensive measurements of SOA precursor emissions were made, including NMHCs, intermediate volatility and semi-volatile organic compounds. This study presents results of SOA production from these low emitting vehicles and compares the results with recently published data. This study also investigates the roles of the photochemistry and SOA precursors in SOA formation. The results from this study provide insight into SOA formation in urban air in the future and provide a basis for assessing the future impacts of low-emitting LDGV fleet.
