Abstract. Emissions from mobile sources are important contributors to both
primary and secondary organic aerosols (POA and SOA) in urban environments.
We compiled recently published data to create comprehensive model-ready
organic emission profiles for on- and off-road gasoline, gas-turbine, and
diesel engines. The profiles span the entire volatility range, including
volatile organic compounds (VOCs, effective saturation concentration
C*=107–1011 µg m−3),
intermediate-volatile organic compounds (IVOCs,
C*=103–106 µg m−3), semi-volatile organic compounds
(SVOCs, C*=1–102 µg m−3), low-volatile organic
compounds (LVOCs, C*≤0.1 µg m−3) and non-volatile
organic compounds (NVOCs). Although our profiles are comprehensive, this
paper focuses on the IVOC and SVOC fractions to improve predictions of SOA
formation. Organic emissions from all three source categories feature
tri-modal volatility distributions (“by-product” mode, “fuel” mode, and
“lubricant oil” mode). Despite wide variations in emission factors for
total organics, the mass fractions of IVOCs and SVOCs are relatively
consistent across sources using the same fuel type, for example, contributing
4.5 % (2.4 %–9.6 % as 10th to 90th percentiles) and
1.1 % (0.4 %–3.6 %) for a diverse fleet of light duty gasoline
vehicles tested over the cold-start unified cycle, respectively. This
consistency indicates that a limited number of profiles are needed to
construct emissions inventories. We define five distinct profiles:
(i) cold-start and off-road gasoline, (ii) hot-operation gasoline,
(iii) gas-turbine, (iv) traditional diesel and (v) diesel-particulate-filter
equipped diesel. These profiles are designed to be directly implemented into
chemical transport models and inventories. We compare emissions to unburned
fuel; gasoline and gas-turbine emissions are enriched in IVOCs relative to
unburned fuel. The new profiles predict that IVOCs and SVOC vapour will
contribute significantly to SOA production. We compare our new profiles to
traditional source profiles and various scaling approaches used previously to
estimate IVOC emissions. These comparisons reveal large errors in these
different approaches, ranging from failure to account for IVOC emissions
(traditional source profiles) to assuming source-invariant scaling ratios
(most IVOC scaling approaches).
Spatial Distribution, Source Apportionment, Ozone Formation Potential, and Health Risks of Volatile Organic Compounds over a Typical Central Plain City in China
