Synergistic effect of water-soluble species and relative humidity on morphological changes in aerosol particles in the Beijing megacity during severe pollution episodes

Xiaole Pan, Baozhu Ge, Zhe Wang, Yu Tian, Hang Liu, Lianfang Wei, Siyao Yue, Itsushi Uno, Hiroshi Kobayashi, Tomoaki Nishizawa, Atsushi Shimizu, Pingqing Fu, Zifa Wang

研究成果: ジャーナルへの寄稿記事

4 引用 (Scopus)

抄録

Depolarization ratio (δ) of backscattered light is an applicable parameter for distinguishing the sphericity of particles in real time, which has been widely adopted by groundbased lidar observation systems. In this study, δ values of particles and chemical compositions in both PM2:5 (aerodynamic diameter less than 2.5 μm) and PM10 (aerodynamic diameter less than 10 μm) were concurrently measured on the basis of a bench-top optical particle counter with a polarization detection module (POPC) and a continuous dichotomous aerosol chemical speciation analyzer (ACSA-14) from November 2016 to February 2017 at an urban site in Beijing megacity. In general, measured δ values depended on both size and sphericity of the particles. During the observation period, mass concentrations of NO-3 in PM 2.5 (fNO 3 ) were about an order of magnitude higher than that in PM 2.5-10 (cNO 3 ) with a mean fNO 3 =cNO 3 ratio of 14±10. A relatively low fNO 3 =cNO 3 ratio (∼ 5) was also observed under higher relative humidity conditions, mostly due to heterogeneous processes and particles in the coarse mode. We found that δ values of ambient particles in both PM 2.5 and PM 2.5-10 obviously decreased as mass concentration of water-soluble species increased at unfavorable meteorological conditions. This indicated that the morphology of particles was changed as a result of water-absorbing processes. The particles with optical size (Dp) of DpD5 μm were used to represent mineral dust particles, and its δ values (δDpD5) decreased by 50% as the mass fraction of cNO 3 increased from 2% to 8% and ambient relative humidity increased up to 80 %, suggesting that mineral dust particles were likely to be spherical during humid pollution episodes. During the observation, relative humidity inside the POPC measuring chamber was stable at 34±2 %, lower than the ambient condition. Its influence on the morphology was estimated to be limited and did not change our major conclusion. This study highlights the evident alteration of non-sphericity of mineral dust particles during their transport owing to a synergistic effect of both pollutant coatings and hygroscopic processes, which plays an important role in the evaluation of its environmental effect.

元の言語英語
ページ(範囲)219-232
ページ数14
ジャーナルAtmospheric Chemistry and Physics
19
発行部数1
DOI
出版物ステータス出版済み - 1 7 2019

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megacity
relative humidity
aerosol
pollution
water
dust
aerodynamics
effect
particle
mineral
speciation (chemistry)
urban site
environmental effect
lidar
coating
polarization
chemical composition

All Science Journal Classification (ASJC) codes

  • Atmospheric Science

これを引用

Synergistic effect of water-soluble species and relative humidity on morphological changes in aerosol particles in the Beijing megacity during severe pollution episodes. / Pan, Xiaole; Ge, Baozhu; Wang, Zhe; Tian, Yu; Liu, Hang; Wei, Lianfang; Yue, Siyao; Uno, Itsushi; Kobayashi, Hiroshi; Nishizawa, Tomoaki; Shimizu, Atsushi; Fu, Pingqing; Wang, Zifa.

:: Atmospheric Chemistry and Physics, 巻 19, 番号 1, 07.01.2019, p. 219-232.

研究成果: ジャーナルへの寄稿記事

Pan, Xiaole ; Ge, Baozhu ; Wang, Zhe ; Tian, Yu ; Liu, Hang ; Wei, Lianfang ; Yue, Siyao ; Uno, Itsushi ; Kobayashi, Hiroshi ; Nishizawa, Tomoaki ; Shimizu, Atsushi ; Fu, Pingqing ; Wang, Zifa. / Synergistic effect of water-soluble species and relative humidity on morphological changes in aerosol particles in the Beijing megacity during severe pollution episodes. :: Atmospheric Chemistry and Physics. 2019 ; 巻 19, 番号 1. pp. 219-232.
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title = "Synergistic effect of water-soluble species and relative humidity on morphological changes in aerosol particles in the Beijing megacity during severe pollution episodes",
abstract = "Depolarization ratio (δ) of backscattered light is an applicable parameter for distinguishing the sphericity of particles in real time, which has been widely adopted by groundbased lidar observation systems. In this study, δ values of particles and chemical compositions in both PM2:5 (aerodynamic diameter less than 2.5 μm) and PM10 (aerodynamic diameter less than 10 μm) were concurrently measured on the basis of a bench-top optical particle counter with a polarization detection module (POPC) and a continuous dichotomous aerosol chemical speciation analyzer (ACSA-14) from November 2016 to February 2017 at an urban site in Beijing megacity. In general, measured δ values depended on both size and sphericity of the particles. During the observation period, mass concentrations of NO-3 in PM 2.5 (fNO 3 ) were about an order of magnitude higher than that in PM 2.5-10 (cNO 3 ) with a mean fNO 3 =cNO 3 ratio of 14±10. A relatively low fNO 3 =cNO 3 ratio (∼ 5) was also observed under higher relative humidity conditions, mostly due to heterogeneous processes and particles in the coarse mode. We found that δ values of ambient particles in both PM 2.5 and PM 2.5-10 obviously decreased as mass concentration of water-soluble species increased at unfavorable meteorological conditions. This indicated that the morphology of particles was changed as a result of water-absorbing processes. The particles with optical size (Dp) of DpD5 μm were used to represent mineral dust particles, and its δ values (δDpD5) decreased by 50{\%} as the mass fraction of cNO 3 increased from 2{\%} to 8{\%} and ambient relative humidity increased up to 80 {\%}, suggesting that mineral dust particles were likely to be spherical during humid pollution episodes. During the observation, relative humidity inside the POPC measuring chamber was stable at 34±2 {\%}, lower than the ambient condition. Its influence on the morphology was estimated to be limited and did not change our major conclusion. This study highlights the evident alteration of non-sphericity of mineral dust particles during their transport owing to a synergistic effect of both pollutant coatings and hygroscopic processes, which plays an important role in the evaluation of its environmental effect.",
author = "Xiaole Pan and Baozhu Ge and Zhe Wang and Yu Tian and Hang Liu and Lianfang Wei and Siyao Yue and Itsushi Uno and Hiroshi Kobayashi and Tomoaki Nishizawa and Atsushi Shimizu and Pingqing Fu and Zifa Wang",
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T1 - Synergistic effect of water-soluble species and relative humidity on morphological changes in aerosol particles in the Beijing megacity during severe pollution episodes

AU - Pan, Xiaole

AU - Ge, Baozhu

AU - Wang, Zhe

AU - Tian, Yu

AU - Liu, Hang

AU - Wei, Lianfang

AU - Yue, Siyao

AU - Uno, Itsushi

AU - Kobayashi, Hiroshi

AU - Nishizawa, Tomoaki

AU - Shimizu, Atsushi

AU - Fu, Pingqing

AU - Wang, Zifa

PY - 2019/1/7

Y1 - 2019/1/7

N2 - Depolarization ratio (δ) of backscattered light is an applicable parameter for distinguishing the sphericity of particles in real time, which has been widely adopted by groundbased lidar observation systems. In this study, δ values of particles and chemical compositions in both PM2:5 (aerodynamic diameter less than 2.5 μm) and PM10 (aerodynamic diameter less than 10 μm) were concurrently measured on the basis of a bench-top optical particle counter with a polarization detection module (POPC) and a continuous dichotomous aerosol chemical speciation analyzer (ACSA-14) from November 2016 to February 2017 at an urban site in Beijing megacity. In general, measured δ values depended on both size and sphericity of the particles. During the observation period, mass concentrations of NO-3 in PM 2.5 (fNO 3 ) were about an order of magnitude higher than that in PM 2.5-10 (cNO 3 ) with a mean fNO 3 =cNO 3 ratio of 14±10. A relatively low fNO 3 =cNO 3 ratio (∼ 5) was also observed under higher relative humidity conditions, mostly due to heterogeneous processes and particles in the coarse mode. We found that δ values of ambient particles in both PM 2.5 and PM 2.5-10 obviously decreased as mass concentration of water-soluble species increased at unfavorable meteorological conditions. This indicated that the morphology of particles was changed as a result of water-absorbing processes. The particles with optical size (Dp) of DpD5 μm were used to represent mineral dust particles, and its δ values (δDpD5) decreased by 50% as the mass fraction of cNO 3 increased from 2% to 8% and ambient relative humidity increased up to 80 %, suggesting that mineral dust particles were likely to be spherical during humid pollution episodes. During the observation, relative humidity inside the POPC measuring chamber was stable at 34±2 %, lower than the ambient condition. Its influence on the morphology was estimated to be limited and did not change our major conclusion. This study highlights the evident alteration of non-sphericity of mineral dust particles during their transport owing to a synergistic effect of both pollutant coatings and hygroscopic processes, which plays an important role in the evaluation of its environmental effect.

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