Variations in submicron aerosol liquid water content and the contribution of chemical components during heavy aerosol pollution episodes in winter in Beijing

X J Shen; J Y Sun; X Y Zhang; Y M Zhang; J T Zhong; X Wang; Y Q Wang; C Xia

doi:10.1016/j.scitotenv.2019.07.327

Variations in submicron aerosol liquid water content and the contribution of chemical components during heavy aerosol pollution episodes in winter in Beijing

Sci Total Environ. 2019 Nov 25:693:133521. doi: 10.1016/j.scitotenv.2019.07.327. Epub 2019 Jul 20.

Authors

X J Shen¹, J Y Sun², X Y Zhang³, Y M Zhang¹, J T Zhong⁴, X Wang⁴, Y Q Wang¹, C Xia¹

Affiliations

¹ State Key Laboratory of Severe Weather & Key Laboratory of Atmospheric Chemistry of CMA, Chinese Academy of Meteorological Sciences, Beijing 100081, China.
² State Key Laboratory of Severe Weather & Key Laboratory of Atmospheric Chemistry of CMA, Chinese Academy of Meteorological Sciences, Beijing 100081, China; State Key Laboratory of Cryospheric Science, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, 730000 Lanzhou, China. Electronic address: jysun@cma.gov.cn.
³ State Key Laboratory of Severe Weather & Key Laboratory of Atmospheric Chemistry of CMA, Chinese Academy of Meteorological Sciences, Beijing 100081, China. Electronic address: xiaoye@cma.gov.cn.
⁴ State Key Laboratory of Severe Weather & Key Laboratory of Atmospheric Chemistry of CMA, Chinese Academy of Meteorological Sciences, Beijing 100081, China; University of Chinese Academy of Sciences, Beijing 100049, China.

PMID: 31377367
DOI: 10.1016/j.scitotenv.2019.07.327

Abstract

The aerosol liquid water content (ALWC) of submicron particles (PM₁) was calculated in this work by three methods based on the aerosol physical and chemical properties measurement campaigns in winter in Beijing, including (a) the PM₁ volume difference between the ambient and dry states by applying the particle number size distribution and particle hygroscopicity measurement; (b) the thermodynamic equilibrium model (ISORROPIA II) based on the chemical composition; and (c) the κ-Köhler theory of chemical composition with a volume mixing scheme. The three methods agreed well with reasonable uncertainties. The ALWC showed an exponential trend depending on the relative humidity (RH), and an abundant ALWC was also favored by the high PM₁ mass loading. The contribution of different chemical component to the ALWC was evaluated by the κ-Köhler method, which revealed that during the measurement, the inorganics and organics could contribute to ~80% and ~20%, respectively, under ambient RH conditions, with the largest contributor of ammonium nitrate. When the RH was above 85%, the mass concentration of ALWC was comparable to, or even larger than, that of the dry PM₁.

Keywords: Aerosol liquid water content; Heavy aerosol pollution episode; North China Plain; Particle hygroscopicity.