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© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 25 Jul 2019

Submitted as: research article | 25 Jul 2019

Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Atmospheric Chemistry and Physics (ACP).

Hygroscopic properties and CCN activity of atmospheric aerosols under the influences of Asian continental outflow and new particle formation at a coastal site in East Asia

Hing Cho Cheung1,2, Charles C.-K. Chou3, Celine S. L. Lee3, Wei-Chen Kuo3, and Shuenn-Chin Chang4,5 Hing Cho Cheung et al.
  • 1School of Atmospheric Sciences, and Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies, Sun Yat-sen University, Guangzhou 510275, China
  • 2Southern Laboratory of Ocean Science and Engineering (Guangdong, Zhuhai), 519082, China
  • 3Research Center for Environmental Changes, Academia Sinica, Taipei 11529, Taiwan
  • 4Environmental Protection Administration, Taipei 10042, Taiwan
  • 5School of Public Health, National Defense Medical Center, Taipei 11490, Taiwan

Abstract. The chemical composition of fine particulate matters (PM2.5), the size distribution and number concentration of aerosol particles (NCN) and the number concentration of cloud condensation nuclei (NCCN) were measured at the northern tip of Taiwan Island during a campaign from April 2017 to March 2018. The parameters of aerosol hygroscopicity (i.e. activation ratio, activation diameter and kappa) were retrieved from the measurements. Significant variations were found in the hygroscopicity of aerosols, which were suggested be subject to various pollution sources, including aged air pollutants originating in the eastern/northern China and transported on the Asian continental outflows, fresh particles emitted from local sources and distributed by land-sea breeze circulations as well as produced by new particle formation (NPF) processes. Cluster analysis was applied to the backward trajectories of air masses to investigate their respective source regions. The results showed that the aerosols associated with Asian continental outflows were characterized with higher kappa values, whereas higher NCCN and NCN with lower kappa values were found for aerosols in local air masses. The distinct features in hygroscopicity were consistent with the characteristics in the chemical composition of PM2.5. Moreover, this study revealed that the nucleation mode particles from NPF could have participated in the enhancement of CCN activity, most likely by coagulating with sub-CCN particles, although the freshly produced particles were not favored for CCN activation due to their smaller sizes. Thus, the results of this study suggested that the NPF coupling with coagulation processes can significantly increase the NCCN in atmosphere.

Hing Cho Cheung et al.
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Hing Cho Cheung et al.
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Short summary
Air pollution can result in changes in the amount and properties of aerosols, which in turn could influence climate by acting as cloud condensation nuclei (CCN). This study investigated the composition and hygroscopicity of aerosols (PM2.5) at a station under influences of East-Asian (EA) outflows and local air mass during respective seasons. The results manifest that the EA aerosols were more hygroscopic, whereas new particle formation and coagulation could also influence local CCN activity.
Air pollution can result in changes in the amount and properties of aerosols, which in turn...