Secondary organic aerosol formation from gasoline vehicle emissions in a new mobile environmental reaction chamber
We present a new mobile environmental reac-tion chamber for the simulation of the atmospheric aging of different emission sources without limitation from the instruments or facilities available at any single site. Pho-tochemistry is simulated using a set of 40 UV lights (to-tal power 4 KW). Characterisation of the emission spec-trum of these lights shows that atmospheric aging of emissions may be simulated over a range of tempera-tures (−7 to 25 • C). A photolysis rate of NO 2 , J NO 2 , of (8.0 ± 0.7) × 10 −3 s −1 was determined at 25 • C. We demon-strate the utility of this new system by presenting results on the aging (OH = 12 × 10 6 cm −3 h) of emissions from a modern (Euro 5) gasoline car operated during a driving cy-cle (New European Driving Cycle, NEDC) on a chassis dy-namometer in a vehicle test cell. Emissions from the entire NEDC were sampled and aged in the chamber. Total or-ganic aerosol (OA; primary organic aerosol (POA) emission + secondary organic aerosol (SOA) formation) was (369.8– 397.5)10 −3 g kg −1 fuel, or (13.2–15.4) × 10 −3 g km −1 , after aging, with aged OA/POA in the range 9–15. A thorough investigation of the composition of the gas phase emissions suggests that the observed SOA is from previously uncon-sidered precursors and processes. This large enhancement in particulate matter mass from gasoline vehicle aerosol emis-sions due to SOA formation, if it occurs across a wider range of gasoline vehicles, would have significant implications for our understanding of the contribution of on-road gasoline ve-hicles to ambient aerosols.