Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
doi:10.5194/acp-2016-1133
© Author(s) 2017. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
02 Jan 2017
Review status
This discussion paper is under review for the journal Atmospheric Chemistry and Physics (ACP).
Photochemical aging of organic and inorganic ambient aerosol from the Potential Aerosol Mass (PAM) reactor experiment in East Asia
Eunha Kang1,2, Meehye Lee1, William H. Brune3, Taehyung Lee4, and Joonyoung Ahn5 1Department of Earth and Environmental Sciences, Korea University, Republic of Korea
2Department of Urban and Environmental studies, Suwon Research Institute, Republic of Korea
3Department of Meteorology, Pennsylvania State University, USA
4Department of Environmental Science, Hankuk University of Foreign Studies, Republic of Korea
5National Institute of Environmental R esearch, Republic of Korea
Abstract. We investigated the photochemical aging of ambient aerosols using a potential aerosol mass (PAM) reactor at Baegryeong Island in the Yellow Sea during August 4–12, 2011. The size distributions and chemical compositions of the ambient and aged PAM aerosols were measured alternately every 6 min by Scanning Mobility Particle Sizer (SMPS) and High Resolution-Time of Flight-Aerosol Mass Spectrometer (HR-ToF-AMS), respectively. Inside the PAM reactor, the O3 and OH levels were equivalent to approximately 5 days of integrated OH exposure at typical atmospheric conditions. Two types of air masses were distinguished on the basis of the chemical composition and the degree of aging: Sulfate was predominant with higher O : C ratio for the air transported from China and organic concentration was higher than that of sulfate with lower O : C ratio when the air came through the Korean Peninsula. In PAM reactor, sulfate was constantly formed, resulting in the increase of particle mass at 200–400 nm size range. Organics were responsible for an overall loss of mass in 100–200 nm particles. This loss was especially evident for the m/z 43 component representing semi-volatile organics. Conversely, the m/z 44 component corresponding to low-volatile organics increased with a shift toward larger sizes during the organics-dominated episode. Therefore, we hypothesize that the oxidation of semi-volatile organics was facilitated by gas-phase oxidation and partitioning for re-equilibrium between the gas and particle phases. Nitrate evaporated in the PAM reactor upon the addition of sulfate to the particles. These results suggest that the chemical composition of aerosols and their degree of photochemical aging particularly for organics are also crucial in determining aerosol mass concentrations. Because sulfate in the atmosphere was stable for about a week of the nominal lifetime of aerosols, SO2 is a unquestionably primary precursor of secondary aerosol in northeast Asia. In comparison, the contribution of organics to secondary aerosols is more variable during transport in the atmosphere. Notably, an increase in low-volatility organics was associated with sulfate and evident at 200–400 nm, highlighting the role of secondary organic aerosol (SOA) in cloud condensation nuclei (CCN) formation.

Citation: Kang, E., Lee, M., Brune, W. H., Lee, T., and Ahn, J.: Photochemical aging of organic and inorganic ambient aerosol from the Potential Aerosol Mass (PAM) reactor experiment in East Asia, Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-1133, in review, 2017.
Eunha Kang et al.
Eunha Kang et al.
Eunha Kang et al.

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Short summary
The Potential Aerosol Mass (PAM) reactor expedites slow atmospheric oxidation reactions and enables to observe chemical aging processes and determine the aerosol-forming power of an air mass. A PAM reactor was first deployed at Baengnyeong Island in the Yellow Sea and experiment results confirm the key role of SO2 in generating secondary aerosols in northeast Asia and the contribution of organics to secondary aerosols is more variable during transport in the atmosphere.
The Potential Aerosol Mass (PAM) reactor expedites slow atmospheric oxidation reactions and...
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