Journal Article

PreJuSER-12502

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Atmospheric OH reactivities in the Pearl River Delta - China in summer 2006: measurement and model results

Lou, S.FZJ* ; Holland, F.FZJ* ; Rohrer, F.FZJ* ; Lu, K.FZJ* ; Bohn, B.FZJ* ; Brauers, T.FZJ* ; Chang, C. C. ; Fuchs, H.FZJ* ; Häseler, R.FZJ* ; Kita, K. ; Kondo, Y. ; Li, X.FZJ* ; Shao, M. ; Zeng, L. ; Wahner, A.FZJ* ; Zhang, Y. ; Wang, W. ; Hofzumahaus, A.FZJ*

2010
EGU Katlenburg-Lindau

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Please use a persistent id in citations: http://hdl.handle.net/2128/10046  doi:10.5194/acp-10-11243-2010

Abstract: Total atmospheric OH reactivities (k(OH)) have been measured as reciprocal OH lifetimes by a newly developed instrument at a rural site in the densely populated Pearl River Delta (PRD) in Southern China in summer 2006. The deployed technique, LP-LIF, uses laser flash photolysis (LP) for artificial OH generation and laser-induced fluorescence (LIF) to measure the time-dependent OH decay in samples of ambient air. The reactivities observed at PRD covered a range from 10 s(-1) to 120 s(-1), indicating a large load of chemical reactants. On average, k(OH) exhibited a pronounced diurnal profile with a mean maximum value of 50 s(-1) at daybreak and a mean minimum value of 20 s(-1) at noon. The comparison of reactivities calculated from measured trace gases with measured k(OH) reveals a missing reactivity of about a factor of 2 at day and night. The reactivity explained by measured trace gases was dominated by anthropogenic pollutants (e. g., CO, NOx, light alkenes and aromatic hydrocarbons) at night, while it was strongly influenced by local, biogenic emissions of isoprene during the day. Box model calculations initialized by measured parameters reproduce the observed OH reactivity well and suggest that the missing reactivity is contributed by unmeasured, secondary chemistry products (mainly aldehydes and ketones) that were photochemically formed by hydrocarbon oxidation. Overall, k(OH) was dominated by organic compounds, which had a maximum contribution of 85% in the afternoon. The paper demonstrates the usefulness of direct reactivity measurements, emphasizes the need for direct measurements of oxygenated organic compounds in atmospheric chemistry studies, and discusses uncertainties of the modelling of OVOC reactivities.

Keyword(s): J

Note: We thank the PRiDe PRD2006 campaign team (2002CB410801), especially M. Hu, N. Takegawa, and A. Oebel for help and support at the field site. We thank Pinhua Xie, Anhui Institute of Optics and Fine Mechanics in Hefei, China, for providing the methane data. C. C. thanks Academic Sinica, Taiwan, for financial support of this work.

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Research Program(s):

1. Atmosphäre und Klima (P23)

Appears in the scientific report 2010

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