Secondary Organic and Inorganic Aerosol Formation from a GDI Vehicle under Different Driving Conditions

Weihan Peng,Niina Kuittinen,Georgios Karavalakis,Cavan Mccaffery,David R Cocker,Topi Rönkkö

doi:10.3390/atmos13030433

Weihan Peng, Niina Kuittinen + Show 4 more

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https://doi.org/10.3390/atmos13030433

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Abstract

This study investigated the primary emissions and secondary aerosol formation from a gasoline direct injection (GDI) passenger car when operated over different legislative and real-world driving cycles on a chassis dynamometer. Diluted vehicle exhaust was photooxidized in a 30 m3 environmental chamber. Results showed elevated gaseous and particulate emissions for the cold-start cycles and higher secondary organic aerosol (SOA) formation, suggesting that cold-start condition will generate higher concentrations of SOA precursors. Total secondary aerosol mass exceeded primary PM emissions and was dominated by inorganic aerosol (ammonium and nitrate) for all driving cycles. Further chamber experiments in high temperature conditions verified that more ammonium nitrate nucleates to form new particles, forming a secondary peak in particle size distribution instead of condensing to black carbon particles. The results of this study revealed that the absorption of radiation by black carbon particles can lead to changes in secondary ammonium nitrate formation. Our work indicates the potential formation of new ammonium nitrate particles during low temperature conditions favored by the tailpipe ammonia and nitrogen oxide emissions from gasoline vehicles.

Highlights

total hydrocarbons (THC) and non-methane hydrocarbons (NMHC) emissions were higher for the cold-start New European Driving Cycle (NEDC), FTP, and LA92 cycles compared to Caltrans
When the engine is cold, the major THC and NMHC source is the fuel vapor from the liquid fuel film on the cylinder surfaces that did not get efficiently oxidized in the three-way catalyst (TWC), which was below its light-off temperature at the beginning of the cycle
The results reported here agree with other studies on gasoline vehicles reported exceedances of ammonium nitrate formation compared to secondary organic aerosol (SOA) [11,13,31]

Summary

Introduction

Gasoline vehicles are known to significantly contribute to secondary organic aerosol (SOA). Formation, with a greater contribution to SOA mass in urban areas compared to diesel vehicles [3–5]. A number of studies have demonstrated the key role gasoline vehicles are playing in the elevated SOA mass production, as a result of VOC and intermediate VOC (IVOC) emissions that are considered precursors for SOA formation [8–11]. The majority of these investigations have reported significant exceedances of SOA mass compared to primary organic aerosol (POA) levels [12–14]

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