Impact of fuels and exhaust aftertreatment systems on the unregulated emissions from mopeds, light and heavy-duty vehicles

摘要

Transport sector plays a key role in climate change and air pollution. Among the anthropogenic sectors, on-road transport is recognized as the rst contributor to global warming, mainly due to its emission of carbon dioxide, ozone precursors and carbonaceous aerosols. In addition, on-road transport contributes to the deterioration of air quality by releasing nitrogen oxides, hydrocarbons, carbonyls, ammonia, and aerosols. However, the current European legislation of vehicles emissions focusses on a limited number of pollutants, namely hydrocarbons, carbon monoxide, nitrogen oxides, and particulate matter.The aim of this work was to improve the knowledge about the emission factors of gas phase and particle-associated emissions from vehicle exhaust. The impacts of aftertreatment devices and fuel quality on regulated and un-regulated species were studied. Several sampling campaigns with dierent types of vehicles were conducted in the vehicle emission laboratory (VELA) at the European Commission Joint Research Centre (EC-JRC) Ispra, Italy. The vehicles chosen were representative of some categories circulating in Europe (heavy duty vehicles, light duty vehicles, two-stroke mopeds), and either standard fuel or some alternative fuels (ethanol and liqueed petroleum gas) were used. The gas phase was monitored by a Fourier transform in-frared spectrometer (carbonyls, nitrogen-containing species, small hydro-carbons), and a resonance-enhanced multiphoton ionization time-ofightmass spectrometer (mono and polycyclic aromatic hydrocarbons). The particulate phase was analyzed by a high-resolution time-of-ight aerosol mass spectrometer (organic aerosol, chloride, nitrate), and a multiangle absorption photometer (black carbon).The mopeds were found to have the higher emission factors of primary organic aerosol and polycyclic aromatic hydrocarbons. While ecient to reduce the regulated emissions, the after-treatment used to comply with the moped Euro 2 emission standard might be responsible of large emission of unregulated organic aerosols. Most of the emission linked to the gasoline light duty vehicles were released before the light-o of the catalyst.Whereas alternative fuels studied helped to reduce ozone precursor emissions, the pollutants associated to the cold start of the vehicle reduced this benecial eect. Finally, the heavy duty diesel vehicle featured the highest nitrogen oxides and black carbon emissions. Despite ecient retrot and after-treatment systems (for particles and nitrogen oxides), these vehicles could release signicant amount of ammonia. These results provided valuable insights for the drafting of legislation related to the achievement of sustainable transport in Europe.Keywords: Atmospheric pollution; on-road transport; unregulated emis-sions; alternative fuels; exhaust aftertreatment systems; mopeds.