Characterizing nighttime vertical profiles of atmospheric particulate matter and ozone in a megacity of south China using unmanned aerial vehicle measurements

Zhanyong Wang; Ruhui Cao; Bai Li; Ming Cai; Zhong-Ren Peng; Guohua Zhang; Qingchang Lu; Hong-di He; Jinpu Zhang; Kai Shi; Yonghong Liu; Hui Zhang; Xisheng Hu

doi:10.1016/j.envres.2023.116854

Characterizing nighttime vertical profiles of atmospheric particulate matter and ozone in a megacity of south China using unmanned aerial vehicle measurements

Environ Res. 2023 Nov 1;236(Pt 2):116854. doi: 10.1016/j.envres.2023.116854. Epub 2023 Aug 9.

Authors

Zhanyong Wang¹, Ruhui Cao², Bai Li³, Ming Cai⁴, Zhong-Ren Peng⁵, Guohua Zhang⁶, Qingchang Lu⁷, Hong-di He³, Jinpu Zhang⁸, Kai Shi⁹, Yonghong Liu⁴, Hui Zhang⁴, Xisheng Hu²

Affiliations

¹ College of Transportation and Civil Engineering, Fujian Agriculture and Forestry University, Fuzhou, 350108, China. Electronic address: wangzy1026@fafu.edu.cn.
² College of Transportation and Civil Engineering, Fujian Agriculture and Forestry University, Fuzhou, 350108, China.
³ School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China.
⁴ School of Intelligent Systems Engineering, Sun Yat-sen University, Guangzhou, 510006, China.
⁵ iAdapt: International Center for Adaptation Planning and Design, College of Design, Construction and Planning, University of Florida, PO Box 115706, Gainesville, FL, 32611-5706, USA; Healthy Building Research Center, Ajman University, Ajman, UAE.
⁶ State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, 510640, China.
⁷ Department of Traffic Information and Control Engineering, School of Electronic and Control Engineering, Chang'an University, Xi'an, 710064, China.
⁸ Guangzhou Sub-branch of Guangdong Ecological and Environmental Monitoring Center, Guangzhou, 510006, Guangdong, China.
⁹ College of Environmental Science and Engineering, China West Normal University, Nanchong, 637009, China.

PMID: 37562735
DOI: 10.1016/j.envres.2023.116854

Abstract

Daytime atmospheric pollution has received wide attention, while the vertical structures of atmospheric pollutants at night play a crucial role in the photochemical process on the following day, which is still less reported. Focusing on Guangzhou, a megacity of South China, we established an unmanned aerial vehicle (UAV) equipped with micro detectors to collect consecutive high-resolution samples of fine particle (PM_2.5), submicron particle (PM_1.0), black carbon (BC) and ozone (O₃) concentrations in the atmosphere, as well as the air temperature (AT) and relative humidity (RH) within a 500 m altitude during nighttime from Oct. 24th to Nov. 6th, 2018. The measurements showed that PM_2.5, PM_1.0, and BC decreased with altitude and were influenced by the nighttime shallow planetary boundary layer (PBL) where BC was more accumulated and fluctuated. In contrast, O₃ was positively correlated with altitude. Backward trajectory clustering and Pasquill stability classification showed that advection and convection significantly influenced the vertical distribution of all pollutants, particularly particulate matter. External air masses carrying high concentrations of pollutants increased PM_1.0 and PM_2.5 levels by 145% and 455%, respectively, compared to unaffected periods. The ratio of BC to PM_2.5 indicated that local emissions had a minor role in nighttime particulate matter. Vertical transport caused by atmospheric instability reduced the differences in pollutant concentrations at various heights. Geodetector and generalized additive model showed that RH and BC accumulation in the PBL were significant factors influencing vertical changes of the secondary aerosol intensity as indicated by the ratio of PM_1.0 to PM_2.5. The joint explanation of RH and atmospheric stability with other variables such as BC is essential to understand the generation of secondary aerosols. These findings provide insights into regional and local measures to prevent and control night-time particulate matter pollution.

Keywords: Atmospheric pollutant; Factor analysis; Nocturnal boundary layer; Vertical distribution.