Comparison of primary aerosol emission and secondary aerosol formation from gasoline direct injection and port fuel injection vehicles

Zhuofei Du,Min Hu,Yudong Yang,Wenbin Zhang,Yanhong Qin,Yusheng Wu,Jing Zheng,Shijin Shuai,Fangting Gu,Jianfei Peng,Mengren Li,Min Shao

doi:10.5194/acp-18-9011-2018

Abstract

Abstract. Gasoline vehicles significantly contribute to urban particulate matter (PM) pollution. Gasoline direct injection (GDI) engines, known for their higher fuel efficiency than that of port fuel injection (PFI) engines, have been increasingly employed in new gasoline vehicles. However, the impact of this trend on air quality is still poorly understood. Here, we investigated both primary emissions and secondary organic aerosol (SOA) formation from a GDI and a PFI vehicle under an urban-like driving condition, using combined approaches involving chassis dynamometer measurements and an environmental chamber simulation. The PFI vehicle emits slightly more volatile organic compounds, e.g., benzene and toluene, whereas the GDI vehicle emits more particulate components, e.g., total PM, elemental carbon, primary organic aerosols and polycyclic aromatic hydrocarbons. Strikingly, we found a much higher SOA production (by a factor of approximately 2.7) from the exhaust of the GDI vehicle than that of the PFI vehicle under the same conditions. More importantly, the higher SOA production found in the GDI vehicle exhaust occurs concurrently with lower concentrations of traditional SOA precursors, e.g., benzene and toluene, indicating a greater contribution of intermediate volatility organic compounds and semi-volatile organic compounds in the GDI vehicle exhaust to the SOA formation. Our results highlight the considerable potential contribution of GDI vehicles to urban air pollution in the future.

Highlights

Organic aerosol (OA) accounts for approximately 20–50 % of ambient fine particulate matter (PM2.5), with significant environment, climate and health effects (Maria et al, 2004; Kanakidou et al, 2005)
The Emission factors (EFs) of CO2 and total hydrocarbon (THC) are derived from measured concentrations in constant volume sampler (CVS), while the EFs of benzene and toluene were calculated from the initial concentrations in the chamber
The EF of THC from the Gasoline direct injection (GDI) vehicle met the standard of the China Phase V Emission Standard (0.1 g km−1), but that from the port fuel injection (PFI) vehicle was slightly above the standard limit

Summary

Introduction

Organic aerosol (OA) accounts for approximately 20–50 % of ambient fine particulate matter (PM2.5), with significant environment, climate and health effects (Maria et al, 2004; Kanakidou et al, 2005). Primary organic aerosol (POA) is emitted directly by sources, while secondary organic aerosol (SOA) is mainly formed via oxidation of gaseous precursors in the atmosphere and accounts for about 30–90 % of OA mass worldwide (Zhang et al, 2007; Hu et al, 2016). Zhao et al (2016a) reported that POA and intermediate volatility organic compounds (IVOCs) from vehicles constituted a large percentage of SOA concentration in China by chamber experiments as well as the two-dimensional volatility basis set (2D-VBS) box model simulations.

Methods

Results

Conclusion