Measurement of NO_yduring Campaign of Air Quality Research inBeijing 2006 (CAREBeijing-2006): Implications for the ozoneproduction efficiency of NO_x

摘要

Total reactive nitrogen oxides (NO_y) are among the key components in the chemistryof ozone production. In order to improve the understanding of the formation mechanismsof high-ozone events in Beijing, China, an intensive experiment on the reactivenitrogen oxides was carried out at the observatory of Peking University during theCampaign of Air Quality Research in Beijing and surrounding areas in 2006(CAREBeijing-2006) campaign. In this study, analysis focusing on the data of high 03episodes was performed to examine the relationship between the concentration of totaloxidant and the composition of NON. High levels of NO and NO_ywere observed in themorning rush hours, indicating the influences of fresh emissions from local traffic.However, the ratio of [NO] to [NO_y] was only 11-60% in the morning, implying thatthere was a substantial amount of aged air pollutants remained overnight in the stagnant airmass. Significant increases in the NO_zmixing ratio (= [NO_y]-[NO_x]) were observedduring the period from the morning toward early afternoon, consistent with the increasingoxidant level. Ozone production efficiency of NO,, (OPE_x), which was derived fromthe NO_z-O_x regression, was found to range from 3.9 to 9.7 mol/mol in Beijing.Furthermore, it was revealed that the daily [NOz] maximum was proportional to the NO,,peak level in the morning, and that OPE_x decreased with the increases of [NO_z] in ahyperbolic form. According to the results, abatement in NO_x emission would not beeffective toward reducing ozone concentrations in Beijing.