AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
Abstract View
High-time resolution VOC and Speciated Total Emissions for Diesel and Gasoline Vehicles: Implications for Future Fleet Emissions and Pollutant Formation
GREG DROZD, Yunliang Zhao, Rawad Saleh, Georges Saliba, Bruce Frodin, Hector Maldonado, Satya Sardar, Allen Robinson, Allen H. Goldstein, University of California, Berkeley
Abstract Number: 428 Working Group: Urban Aerosols
Abstract Over the past two decades vehicle emissions standards in the United States have been dramatically tightened with the goal of reducing urban air pollution. Secondary organic aerosol (SOA) is the dominant contributor to urban organic aerosol, but controversy remains regarding the contributions of different types of vehicles to this SOA. Recent studies suggest increased non-methane hydrocarbon (NMHC) potency for SOA formation in lower emission standards vehicles. Speciation and time-resolved measurements during drive cycles for vehicular NMHC emissions are critical for effectively predicting not only SOA production, but also ozone formation and levels of air toxics. Experiments were conducted at the California Air Resources Board Haagen-Smit Laboratory to investigate pollutant emissions for Tier 0 (T0) and low, ultra-low, super ultra-low, and partial zero emission vehicles (LEV, ULEV, SULEV, PZEV). Tailpipe emissions were comprehensively characterized over a wide range of volatilities, from VOCs to LVOCs. Time-resolved measurements of VOCs using a proton-transfer-reaction mass spectrometer reveal the importance of emissions during the first 30 seconds after engine start and hard acceleration. IVOCs and SVOCs were sampled with sorbent tubes and characterized using thermal desorption two dimensional gas-chromatography-mass-spectrometry with electron impact (2D-GC-EI-MS) and vacuum-ultraviolet (2D-GC-VUV-MS) ionization. 2D-GC-EI-MS data reveal isomer distributions for alkyl benzenes that are drive-cycle dependent. 2D-GC-VUV-MS analysis of diesel exhaust IVOCs showed they are dominated by cyclic, branched compounds. A diesel vehicle with a particulate filter and selective catalytic reduction showed near elimination of IVOC emissions. Primary organic aerosol collected on quartz filters analyzed using 2D-GC-VUV-MS clearly show that gasoline and diesel particles were dominated by motor oil. These tests show that more than 200 miles of hot stabilized driving are typically required to equal cold start emissions. VOC emissions profiles, particularly for the BTEX compounds, show differences from the neat fuel composition, with implications for fuel-based emissions inventories.