Overview
This program will investigate the physical and chemical composition of secondary emissions from 2 natural gas trucks and 2 modern technology diesel trucks over realistic driving conditions. The proposed study will complement the major 200 vehicle program funded by SCAQMD. Primary organic aerosol (POA) will be measured for all heavy-duty vehicles over different driving cycle using a chassis dynamometer. The primary emissions testing using CE-CERT’s Mobile Emissions Lab (MEL) and heavy-duty chassis dynamometer will be covered under the base SCAQMD program. Emission measurements will include regulated pollutants, PM mass, total particle number, solid particle number in accordance to the PMP protocol, black carbon, and particle size distributions, as well as carbonyl compounds. For each vehicle, the exhaust will be collected in CE-CERT’s mobile chamber and subsequently photochemically aged. This proposal will expand on SCAQMD’s funding for evaluating in-use emissions from current technology natural gas and diesel trucks and for evaluating secondary organic aerosol (SOA) formation from GDI vehicles, including ethanol fueled GDI vehicles. The proposed work will use the mobile environmental chamber with on-line gas and particle phase instrumentation to include detailed physical and chemical characterization of primary and secondary aerosol (e.g., POA and SOA) from heavy-duty vehicles. There are three novel aspects for this program: (1) characterizing current generation heavy-duty vehicles, since most previous studies have focused on light-duty vehicles/engines, and (2) characterizing the SOA forming potential from natural gas trucks. To the best of our knowledge, this will be the first study looking at the impacts of natural gas heavy-duty vehicles on SOA formation and ultimately their impact in air quality. Characterizing aerosols from heavy-duty diesel and natural gas vehicles is an important step in understanding air quality in our region. Heavy-duty trucks are important sources of volatile and semi-volatile organic compounds (VOCs and SVOCs), NOx, CO, and particulate matter (PM) that represent a significant contribution to SOA and ozone formation in the atmosphere. Secondary organic aerosol formed from atmospheric reactions of volatile and semi-organic compounds in the presence of NOx constitutes an important component of suspended fine atmospheric particulate matter that impacts visibility, climate, and health. Studies have shown that in California diesel emissions from heavy-duty vehicles contribute to primary organic aerosol (POA), but not detectably to SOA, while gasoline vehicles are the main source of SOA formation (Bahreini et al., 2012). However, there is a gap in the literature about the actual effects of primarily natural gas heavy-duty vehicles and diesel trucks.
Lead Researcher: Dr. Georgios Karavalakis Co-researcher: Dr. David Cocker