Intermediate volatile organic compounds emissions from vehicles under real world conditions

Area of Science:

• Environmental Science
• Atmospheric Chemistry
• Transportation Emissions

Background:

• Vehicle emissions are a major source of air pollution.
• Intermediate volatile organic compounds (IVOCs) contribute to secondary organic aerosol (SOA) formation.
• Quantifying real-world IVOC emissions is crucial for effective air quality management.

Purpose of the Study:

• To quantify real-world emission factors (EFs) of total IVOCs and VOCs from mixed vehicle fleets.
• To investigate the relationships between IVOC EFs, fleet composition, and vehicle speed.
• To assess the secondary organic aerosol formation potentials (SOAFPs) of IVOCs and VOCs.

Main Methods:

• Real-world vehicle emissions were measured in the Yangtze tunnel, Shanghai.
• Multiple linear regression (MLR) was used to estimate IVOC EFs for gasoline and diesel vehicles.
• IVOCs were classified into unresolved complex mixtures and speciated target compounds (n-alkanes, PAHs).

Main Results:

• Average total-IVOC EF was 24.9 ± 7.8 mg/(km·veh), comparable to VOCs.
• Unspeciated cyclic compounds and branched alkanes (b-alkanes) dominated IVOC composition.
• IVOC EFs positively correlated with diesel vehicle fractions and significantly contributed to SOAFP (86%).

Conclusions:

• Diesel vehicles are the primary real-world sources of IVOC emissions.
• IVOC emissions significantly contribute to SOA formation, highlighting the need for control policies.
• Reducing IVOC emissions from vehicles is essential for improving air quality.