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 4KW). 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 NO2, JNO2 , 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=12×106 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 gkm−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 Geoscientific our understanding of the contribution of on-road gasoline ve- hicles to ambient aerosols.