Gasoline aromatics: a critical determinant of urban secondary organic aerosol formation

Abstract

Abstract. Gasoline vehicle exhaust is an important contributor to secondary organic aerosol (SOA) formation in urban atmosphere. Fuel composition has a potentially considerable impact on gasoline SOA production, but the link between fuel components and SOA production is still poorly understood. Here, we present chamber experiments to investigate the impacts of gasoline aromatic content on SOA production through chamber oxidation approach. A significant amplification factor of 3-6 for SOA productions from gasoline exhausts is observed as gasoline aromatic content rose from 29 to 37 %. Considerably higher emission of aromatic volatile organic compounds (VOCs) using high-aromatic fuel plays an essential role in the enhancement of SOA production, while semi-volatile organic compounds (e.g., gas-phase PAHs) may also contribute to the higher SOA production. Our findings indicate that gasoline aromatics significantly influence ambient PM 2.5 concentration in urban areas and emphasize that more stringent regulation of gasoline aromatic content will lead to considerable benefits for urban air quality.

Remarkable nucleation and growth of ultrafine particles from vehicular exhaust

“…In addition, photooxidation of vehicular exhaust (dominantly aromatic VOCs) yields abundant precursors for nucleation and growth of UFPs (29,32) as demonstrated in our three different types of measurements. Our ambient and chamber measurements are representative of typical urban environments worldwide (8) since the gasoline fleet of the commonly used vehicle model in China is equivalent to those in Europe and the United States (27). We conclude that NPF under urban environments is mainly driven by organics from local traffic emissions.…”

“…In addition, we evaluated NPF in an enclosed environmental chamber using vehicular exhaust from a gasoline car operating on a chassis dynamometer (SI Appendix, Fig. S2) (27).…”

“…To assess NPF from traffic emissions, we conducted complementary experiments by introducing gasoline vehicular exhaust (27) into an enclosed environmental chamber (i.e., without gas exchange between the chamber and ambient air). While many previous studies examined the contributions of vehicular exhaust to secondary organic aerosol formation (27), few focused on NPF. Gases from the vehicular exhaust were diluted to atmospherically relevant levels in the chamber, and all experiments using vehicular exhaust were performed under the clean conditions.…”

“…Vehicular exhaust experiments were conducted by combining the chassis dynamometer system (Burke E. Porter Machinery Company) and an outdoor enclosed environmental chamber (SI Appendix, Fig. S2) similarly to that described elsewhere (27). The chosen gasoline fleet was a commonly used vehicle model in China that was certified to the China IV emission standard and equivalent to Euro 4.…”

Chemical characterization and source identification of PM<sub>2.5</sub> at multiple sites in the Beijing–Tianjin–Hebei region, China

“…These two unsaturated hydrocarbon species have important effects on air quality (Schell et al, 2001), as decreasing alkene content can decrease fire temperatures and reduce NO x emissions (G. Q. . A new study has also reported that gasoline aromatic hydrocarbons had an essential role in urban SOA production enhancement and thus significantly affected the ambient PM 2.5 (Peng et al, 2017). The limits on aromatic and alkene contents in vehicle gasoline are respectively 40 and 28 % for China IV starting in 2014, 40 and 24 % for China V starting in 2017, and 35 and 18 % for China VI, which is suggested for implementation in 2019 (http://www.nea.gov.cn/).…”