Evaluating the relationships between aromatic and ethanol levels in gasoline on secondary aerosol formation from a gasoline direct injection vehicle

Patrick Roth; Jiacheng Yang; Christos Stamatis; Kelley C Barsanti; David R Cocker 3rd; Thomas D Durbin; Akua Asa-Awuku; Georgios Karavalakis

doi:10.1016/j.scitotenv.2020.140333

Evaluating the relationships between aromatic and ethanol levels in gasoline on secondary aerosol formation from a gasoline direct injection vehicle

Sci Total Environ. 2020 Oct 1:737:140333. doi: 10.1016/j.scitotenv.2020.140333. Epub 2020 Jun 20.

Authors

Patrick Roth¹, Jiacheng Yang¹, Christos Stamatis¹, Kelley C Barsanti¹, David R Cocker 3rd¹, Thomas D Durbin¹, Akua Asa-Awuku², Georgios Karavalakis³

Affiliations

¹ University of California, Bourns College of Engineering, Center for Environmental Research and Technology (CE-CERT), 1084 Columbia Avenue, Riverside, CA 92507, USA; Department of Chemical and Environmental Engineering, Bourns College of Engineering, University of California, Riverside, CA 92521, USA.
² University of California, Bourns College of Engineering, Center for Environmental Research and Technology (CE-CERT), 1084 Columbia Avenue, Riverside, CA 92507, USA; Department of Chemical and Environmental Engineering, Bourns College of Engineering, University of California, Riverside, CA 92521, USA; Department of Chemical and Biomolecular Engineering, A. James Clark School of Engineering, University of Maryland, College Park, MD 20742, USA. Electronic address: asaawuku@umd.edu.
³ University of California, Bourns College of Engineering, Center for Environmental Research and Technology (CE-CERT), 1084 Columbia Avenue, Riverside, CA 92507, USA; Department of Chemical and Environmental Engineering, Bourns College of Engineering, University of California, Riverside, CA 92521, USA. Electronic address: gkaraval@cert.ucr.edu.

PMID: 32783873
DOI: 10.1016/j.scitotenv.2020.140333

Abstract

While the effects of fuel composition on primary vehicle emissions have been well studied, less is known about the effects on secondary aerosol formation and composition. The propensity of light-duty gasoline engines to form secondary aerosol and contribute to regional air quality burdens are of scientific interest. This study assessed secondary aerosol formation and composition due to photochemical aging of exhaust emissions from a light-duty vehicle equipped with gasoline direct injection (GDI) engine. The vehicle was operated on eight fuels with varying ethanol and aromatic levels. Testing was performed over the LA92 cycle using a chassis dynamometer. The aging studies were performed using a mobile environmental chamber. Diluted exhaust emissions were introduced to the mobile chamber over the course of the LA92 cycle and subsequently photochemically reacted. It was found that secondary aerosol mass exceeded the primary particulate matter (PM) emissions. Secondary aerosol was primarily composed of ammonium nitrate due to the elevated tailpipe ammonia emissions. The high aromatic fuels produced greater total carbonaceous aerosol and secondary organic aerosol (SOA) compared to the low aromatic fuels. A clear influence of ethanol for the high aromatic fuels on SOA formation was observed, with greater SOA formation for the fuels with higher ethanol contents. Our results suggest that more SOA formation is expected from current GDI vehicles when operated with gasoline fuels rich with heavier aromatics and blended with higher ethanol levels.

Keywords: Ethanol blends; Gasoline aromatics; Gasoline direct injection; PM index; Secondary organic aerosol (SOA).