AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
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Characterization of Particulate Bound Polycyclic Aromatic Compounds (PACs) and Their Oxidations in Heavy Polluted Atmosphere: A Case Study in Urban Beijing, China during Haze Events
LIJUAN LI, Steven Sai Hang Ho, Junji Cao, Chinese Academy of Sciences
Abstract Number: 345 Working Group: Urban Aerosols
Abstract Characterizations on polycyclic aromatic compounds (PACs) during frequent haze periods have been conducted in an urban site of Beijing, China. Particulate polycyclic aromatic hydrocarbons (PAHs) and oxygenated-PAHs (OPAHs) and other carbonaceous matters were quantified. The average PM2.5 during haze events (256.3 ±103.7 μg/m3) were one magnitude over than that of CRs (24.7 ± 27.7 μg/m3 ).The average total quantified PAHs (ΣPAHs) and OPAHs (ΣOPAHs) during haze events were 423.9 ± 178.4ng/m3 and 581.4 ±299.8 ng/m3 , respectively, which were 10 times higher than those of 40.3 ± 68.2 ng/m3 and 54.4 ± 82.4 ng/m3 in clear days. Four-rings PAHs had the highest compositions. 1,8-Naphthalic anhydride (1,8-NA) is the most abundant OPAHs, accounted for 49.8% of ΣOPAHs, followed by 9,10-anthraquinone (9,10-AQ) (13.8%) and benzo(a)anthracene-7,12-dione (BaAQ) (8.31%). In haze events, the contents of 5- to 7-rings PAHs decreased by 2.32% compared with those of clear days, while lower molecular weight fractions of 3- and 4-rings PAHs increased. The relationships between PAHs, OPAHs and relative humidity (RH) were found to be exponential. High oxygenation rate (R0) ratios of OPAH /PAH represents higher rates in secondary formation or degradation and gas- particle conversion for each PAH or OPAH during the wintertime. Significant positive correlation between BeP and OPAHs (r=0.97), combined with the results of photochemical aging and negatively correlation with O3, suggest that secondary atmospheric reactions of PAHs played an important role in the burden of OPAHs.