Hygroscopic properties and cloud condensation nuclei activity of atmospheric aerosols under the influences of Asian continental outflow and new particle formation at a coastal site in eastern Asia
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Published:2020-05-19
Issue:10
Volume:20
Page:5911-5922
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ISSN:1680-7324
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Container-title:Atmospheric Chemistry and Physics
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language:en
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Short-container-title:Atmos. Chem. Phys.
Author:
Cheung Hing ChoORCID, Chou Charles Chung-Kuang, Lee Celine Siu Lan, Kuo Wei-Chen, Chang Shuenn-Chin
Abstract
Abstract. The chemical composition of fine particulate matter (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 during an intensive
observation experiment from April 2017 to March 2018. The parameters of
aerosol hygroscopicity (i.e., activation ratio, activation diameter and kappa
of CCN) were retrieved from the measurements. Significant variations were
found in the hygroscopicity of aerosols (kappa – κ – of 0.18–0.56, for water vapor supersaturation – SS – of 0.12 %–0.80 %), which were subject to various pollution sources, including aged
air pollutants originating in eastern and northern China and transported by
the Asian continental outflows and fresh particles emitted from local sources
and distributed by land–sea breeze circulations as well as produced by processes of new
particle formation (NPF). Cluster analysis was applied to the
back trajectories of air masses to investigate their respective source
regions. The results showed that aerosols associated with Asian continental
outflows were characterized by lower NCN and NCCN values and by
higher kappa values of CCN, whereas higher NCN and NCCN values with lower kappa values
of CCN were observed in the aerosols associated with local air masses.
Besides, it was revealed that the kappa value of CCN exhibited a decrease during
the early stage of an event of new particle formation, which turned to an
increasing trend over the later period. The distinct features in the
hygroscopicity of aerosols were found to be consistent with the
characteristics in the chemical composition of PM2.5. This study has
depicted a clear seasonal characteristic of hygroscopicity and CCN activity
under the influence of a complex mixture of pollutants from different
regional and/or local pollution sources. Nevertheless, the mixing state and
chemical composition of the aerosols critically influence the aerosol
hygroscopicity, and further investigations are necessary to elucidate the
atmospheric processing involved in the CCN activation in coastal areas.
Funder
Ministry of Science and Technology, Taiwan
Publisher
Copernicus GmbH
Subject
Atmospheric Science
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