Primary particle emissions and atmospheric ageing from road traffic.
Résumé
Road traffic is a significant source of atmospheric aerosols, which are important pollutants (class 1 carcinogens for Humans). It contributes to primary and secondary particles in the atmosphere, depending on the presence of particle precursors such as volatile, intermediate-volatility, and semi-volatile organic compounds (VOCs, IVOCs, SVOCs). However, lack of knowledge exists on the sampling methodology, which depends on dilution and available deposition surface. Moreover, the physicochemical and photochemical processes leading to secondary aerosols are complex, and often studied in specific experimental conditions. Therefore, contribution of transportation on aerosol pollution is under-estimated in air-quality models. This study presents particle, black-carbon (BC) and IVOC emissions on a chassis dynamometer under controlled conditions (10 diesel and gasoline passenger-cars, Euro 1 to Euro 6) and in-situ (open urban area and tunnel). Particles and BC were measured with optical devices; IVOCs were sampled on sorbent tubes and analyzed with mass-spectroscopy. IVOC emissions are 2 to 2500 times higher in-situ than for chassis dynamometer experiments. Results show that sampling conditions influence significantly IVOC concentrations, mainly due to temperature and dilution effects on gas-particle partitioning. IVOCs can also nucleate to form new particles, or condensate onto pre-existing particles, and play an important role on particle atmospheric ageing.
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