Reactive Organic Gases from Vehicle Evaporative Emissions: Rates, Compositions, and Temperature Effects

This study quantifies evaporative volatile organic compound
emissions
from China 3 to China 6 standard vehicles using a variable temperature
sealed housing evaporative determination system. Total hydrocarbon
(THC) emission factors during diurnal breathing losses (DBL) exhibited
distinct temporal trends: the averages were 0.58, 0.87, 0.40, and
0.18 g·day–1 for DBL day 1 (0–24 h)
escalating to 2.97, 2.88, 0.41, and 0.21 g·day–1 for DBL day 2 (24–48 h) across emission standards. Proton
Transfer Reaction Time-of-Flight Mass Spectrometry identified 197
reactive organic gases (ROGs), with oxygenated and nitrogen-containing
compounds contributing 20% ± 11%, 18% ± 9%, and 13% ±
9% to hot soak losses, DBL day 1, and DBL day 2, respectively. Alkanes,
alkenes, aromatics, and carbonyls/ketones dominated ROG emissions
(44%–99% combined). The emission composition shifted significantly
across high-, normal-, and low-emitting vehicles: traditional hydrocarbons
decreased progressively, while carbonyls/ketones increased, attenuating
hydroxyl radical reactivity (OHR) reduction. Temperature-dependent
experiments revealed proportional increases in THC and key ROG emissions
per unit temperature increase, well-characterized by exponential functions.
Controlling evaporative emissions by regulating oxygenated species
and adopting near-zero emission vehicles reduces aerosol/ozone formation,
while reactive carbonyl/ketone shifts in modern fleets highlight evolving
atmospheric impacts, requiring tailored control strategies.