Secondary Organic Aerosol Formation from m-Xylene in the Absence of NO_x

摘要

Formation of secondary organic aerosol (SOA) from m-xylene photoxidation in the absence of NO_x was investigated in a series of smog chamber experiments. Experiments were performed in dry air and in the absence of seed aerosol with H_2O_2 photolysis providing a stable hydroxyl radical (OH radical) source. SOA formation from this study is exceptionally higher than experiments with existence of NO_x. The experiments with elevated HO_2 levels indicate that organic hydroperoxide compounds should contribute to SOA formation. Nitrogen oxide (NO) is shown to reduce aerosol formation; the constant aerosol formation rate obtained before addition of NO and after consumption of NO Strongly suggests that aerosol formation is mainly through reactions with OH and HO_2 radicals. In addition, a density of 1.40 ± 0.1 g cm~(-3) for the SOA from the photooxidation of m-xylene in the absence of N0_x has been measured, which is significantly higher than the currently used unit density.