Process-Specific Evaporative Emission of Semivolatile/Intermediate-Volatility Organic Compounds from Modern Gasoline...

Area of Science:

• Atmospheric Chemistry
• Environmental Science
• Organic Geochemistry

Background:

• Evaporative emissions from gasoline vehicles are an underestimated source of secondary organic aerosol (SOA).
• Current air quality models often lack molecular-level data for semivolatile and intermediate-volatility organic compounds (S/IVOCs), hindering accurate SOA estimation.

Purpose of the Study:

• To characterize S/IVOCs from major gasoline vehicle evaporative processes using advanced analytical techniques.
• To determine the contribution of S/IVOCs to SOA formation potential across different emission events.
• To identify molecular-level chemical fingerprints for differentiating evaporative emission processes.

Main Methods:

• Utilized comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC × GC-TOFMS) for detailed S/IVOC characterization.
• Analyzed evaporative emissions from diurnal breathing loss, hot soak, running loss, and refueling processes.
• Employed volcano plot analysis to identify unique molecular signatures for each emission process.

Main Results:

• S/IVOCs constituted 16.8-58.3% of total evaporative emissions, with IVOCs dominating SOA formation potential (>50% during hot soak and running loss).
• Distinct molecular fingerprints were observed for each process, including oxygenated species (refueling), cycloalkanes (diurnal/hot soak), and nitrogen-containing compounds (running loss).
• These fingerprints suggest contributions from non-fuel sources and selective volatilization, challenging the simple fuel mixture concept.

Conclusions:

• This study provides critical molecular-level insights into S/IVOCs from gasoline vehicle evaporative emissions.
• The identified chemical fingerprints are essential for refining mobile source inventories and improving urban air quality models.
• Incorporating these S/IVOC profiles is necessary for effective air quality management in the post-tailpipe emissions era.