Variations in physicochemical properties of airborne particles during a heavy haze-to-dust episode in Beijing

Zihan Wang; Wei Hu; Hongya Niu; Weiwei Hu; Yusheng Wu; Libin Wu; Lujie Ren; Junjun Deng; Song Guo; Zhijun Wu; Daizhou Zhang; Pingqing Fu; Min Hu

doi:10.1016/j.scitotenv.2020.143081

Variations in physicochemical properties of airborne particles during a heavy haze-to-dust episode in Beijing

Sci Total Environ. 2021 Mar 25:762:143081. doi: 10.1016/j.scitotenv.2020.143081. Epub 2020 Oct 17.

Authors

Zihan Wang¹, Wei Hu², Hongya Niu³, Weiwei Hu⁴, Yusheng Wu⁴, Libin Wu¹, Lujie Ren¹, Junjun Deng¹, Song Guo⁴, Zhijun Wu⁴, Daizhou Zhang⁵, Pingqing Fu¹, Min Hu⁶

Affiliations

¹ Institute of Surface-Earth System Science, School of Earth System Science, Tianjin University, Tianjin 300072, China.
² Institute of Surface-Earth System Science, School of Earth System Science, Tianjin University, Tianjin 300072, China; State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, China. Electronic address: huwei@tju.edu.cn.
³ Key Laboratory of Resource Exploration Research of Hebei Province, Hebei University of Engineering, Handan 056038, China.
⁴ State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, China.
⁵ Faculty of Environmental and Symbiotic Sciences, Prefectural University of Kumamoto, Kumamoto 862-8502, Japan.
⁶ State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, China; Collaborative Innovation Center of Atmospheric Environment and Equipment Technology, Nanjing University of Information Science & Technology, Nanjing 210044, China. Electronic address: minhu@pku.edu.cn.

PMID: 33190904
DOI: 10.1016/j.scitotenv.2020.143081

Abstract

The variations in physicochemical properties of airborne particles collected during a typical transition from haze to dust were investigated using single particle analysis with transmission and scanning electron microscopes combined with online measurement of chemical compositions of airborne particles in Beijing in February 2013. The transition was divided into three phases based on the weather condition. During haze pollution (Phase 1), gaseous and particle pollutants enhanced gradually. Results from single particle analysis showed that more coatings and more anthropogenic elements (e.g., S) appeared on the surface of fine and coarse particles, which was probably caused by efficient aqueous-phase reactions under high humidity (70%) condition. Phase 2 was dust intrusion episode. PM₁₀ reached over 1000 μg m^-3. Larger fractions of mineral particles and bare-like soot particles were observed in fine particles, while the fraction of secondary particles with coatings decreased. The proportion of black carbon in submicron particles also increased. Photochemical oxidation in gas phase likely dominated in secondary formation under high O₃ concentration. After the dust episode (Phase 3), secondary formation enhanced obviously. Soot aged quickly and had a larger mode of 0.45 μm than the other phases. The size modes of airborne fine particles during Phases 1 and 3 were 0.35 μm, which were a bit larger than that during Phase 2 (0.24 μm). These results indicate that dust plumes accompanied with strong wind brought mineral particles in both fine and coarse modes and freshly emitted particles with smaller sizes, and swept away pre-presence air pollutants. This study could provide detailed information on the physicochemical properties of airborne particles during typical severe pollution processes in a short time. Such short-term change should be taken into account in order to more accurately assess the environmental, climatic and health-related effects of airborne particles.

Keywords: Aerosol mass spectrometer; Haze-to-dust transition; Individual particles analysis; Physicochemical properties; Secondary formation.