American Association for Aerosol Research - Abstract Submission

AAAR 38th Annual Conference
October 5 - October 9, 2020

Virtual Conference

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Investigating the Formation of Primary and Secondary Aerosols from Heavy Duty Vehicles (HDVs) Using Smog Chamber

SAHAR GHADIMI, Hanwei Zhu, David R. Cocker III, Thomas D. Durbin, Georgios Karavalakis, University of California, Riverside

     Abstract Number: 123
     Working Group: Combustion

Abstract
Heavy duty vehicles (HDVs) are major contributors to urban air pollution. Fuel types and driving conditions—Urban Dynamometer Driving Schedule (UDDS) cycle, refuse cycle and Cruise cycle— are known to impact vehicle emissions, while their influence need further investigation particularly on secondary organic aerosol (SOA) formation. In this study, the secondary and primary aerosol formations from different fuel types including Liquefied Petroleum Gas (LPG), Compressed Natural Gas (CNG), Renewable Diesel (RD), and Ultra-low Sulfur Diesel (ULSD) and different aftertreatments such as Three-Way Catalyst (TWC), Diesel Particulate Filter (DPF) and Selective Catalytic Reduction (SCR), were investigated using the 30 m3 Mobile Atmospheric Chamber (MACh) at UC Riverside. The physiochemical properties of the emissions and aerosols were evaluated using variety of particle and gas phase instrumentations such as Scanning Mobility Particle Sizer (SMPS), Kanomax Aerosol Mass (APM) analyzer, High-Resolution Time-of-Fight Aerosol Mass Spectrometer (HR-ToF-AMS), and LI-840A CO2/H2O gas phase analyzer. All of the experiments were performed under cold start conditions.

For all the fuel types, cruise mode produced lower primary and secondary emissions comparing to the UDDS and refuse driving cycle. Higher secondary organic mass observed in ULSD vehicles bearing DPF aftertreatment compered to RD vehicles with the same after treatment. Inorganic ammonium nitrate (NH4NO3) aerosols were extremely low (or negligible in some cases) in primary emissions and MACh-mediated photo-oxidation of diesel (RD and ULSD) exhaust. On the other hand, LPG and CNG vehicles were equipped with TWC aftertreatment produced higher ammonia (NH3) which further generated secondary ammonium nitrate particles (NH4NO3) upon reacting with HNO3. The combined impact of fuel type, aftertreatment strategies, and driving mode on primary and secondary emissions will be evaluated and discussed in detail.