References

ACP

Atmospheric Chemistry and Physics

ACP

1680-7324

Copernicus GmbH

Göttingen, Germany

10.5194/acp-10-11243-2010

Atmospheric OH reactivities in the Pearl River Delta – China in summer 2006: measurement and model results

Lou

¹ ² Holland

² Rohrer

² Lu

² ³ Bohn

² Brauers

² Chang

C.C.

⁶ Fuchs

² Häseler

² Kita

⁴ Kondo

⁵ Li

² ³ Shao

³ Zeng

³ Wahner

² Zhang

³ Wang

¹ Hofzumahaus

School of Environmental Science and Technology, Shanghai Jiao Tong University, Shanghai, China

Institut für Energie und Klimaforschung: Troposphäre, Forschungszentrum Jülich, Jülich, Germany

College of Environmental Sciences and Engineering, Peking University, Beijing, China

Faculty of Science, Ibaraki University, Ibaraki, Japan

Research Center for Advanced Science and Technology, University of Tokyo, Tokyo, Japan

Research Center for Environmental Changes (RCEC), Academic Sinica, Taipei, China

30 11 2010

10 22 11243 11260

This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

This article is available from http://www.atmos-chem-phys.net/10/11243/2010/acp-10-11243-2010.html

The full text article is available as a PDF file from http://www.atmos-chem-phys.net/10/11243/2010/acp-10-11243-2010.pdf

Total atmospheric OH reactivities (kOH) 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, kOH 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 kOH 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, kOH 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.

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