Atmospheric hydrogen peroxide and organic hydroperoxides during PRIDE-PRD'06, China: their concentration, formation mechanism and contribution to secondary aerosols

W. Hua, Z. M. Chen, C. Y. Jie, Y. Kondo, A. Hofzumahaus, N. Takegawa, C. C. Chang, K. D. Lu, Y. Miyazaki, K. Kita, H. L. Wang, Y. H. Zhang (+1 others)
2008 Atmospheric Chemistry and Physics  
Atmospheric hydrogen peroxide (H 2 O 2 ) and organic hydroperoxides were measured from 18 to 30 July in 2006 during the PRIDE-PRD'06 campaign at Backgarden, a rural site located 48 km north of Guangzhou, a mega-city in southern China. A groundbased instrument was used as a scrubbing coil collector to sample ambient air, fol-5 lowed by on-site analysis by high-performance liquid chromatography (HPLC) coupled with post-column derivatization and fluorescence detection. The H 2 O 2 mixing ratio
more » ... the 13 days ranged from below the detection limit to a maximum of 4.6 ppbv, with a mean (and standard deviation) of (1.26±1.24) ppbv during the daytime (08:00-20:00 LT). Methyl hydroperoxide (MHP), with a maximum of 0.8 ppbv and a mean (and 10 standard deviation) of (0.28±0.10) ppbv during the daytime, was the dominant organic hydroperoxide. Other organic peroxides, including bis-hydroxymethyl hydroperoxide (BHMP), peroxyacetic acid (PAA), hydroxymethyl hydroperoxide (HMHP), 1-hydroxyethyl hydroperoxide (1-HEHP) and ethyl hydroperoxide (EHP), were detected occasionally. The concentration of H 2 O 2 exhibited a pronounced diurnal variation on sunny 15 days, with a peak mixing ratio in the afternoon (12:00-18:00 LT), but lacked an explicit diurnal cycle on cloudy days. Sometimes a second peak mixing ratio of H 2 O 2 was observed during the evening, suggesting that H 2 O 2 was produced by the ozonolysis of alkenes. The diurnal variation profile of MHP was, in general, consistent with that of H 2 O 2 . The estimation indicated that in the morning the H 2 O 2 detected was formed 20 mostly through local photochemical activity, with the rest probably attributable to vertical transport. It is notable that relatively high levels of H 2 O 2 and MHP were found in polluted air. The unexpectedly high level of HO 2 radicals detected in this region can account for the production of hydroperoxides, while the high level of NO x suppressed the formation of hydroperoxides significantly. High concentrations of hydroperoxides 25 were detected in samples of rainwater collected in a heavy shower on 25 July when a typhoon passed through, indicating that a considerable mixing ratio of hydroperoxides, particularly MHP, resided above the upper boundary layer, which might be transported 10483 Abstract ACPD
doi:10.5194/acp-8-6755-2008 fatcat:mf5mtpvskraltp6rpq5d5pguna