A cold front induced co-occurrence of O3 and PM2.5 pollution in a Pearl River Delta city: Temporal variation, vertical structure, and mechanism

Yuanping He; Lei Li; Haolin Wang; Xinqi Xu; Yuman Li; Shaojia Fan

doi:10.1016/j.envpol.2022.119464

A cold front induced co-occurrence of O₃ and PM_2.5 pollution in a Pearl River Delta city: Temporal variation, vertical structure, and mechanism

Environ Pollut. 2022 Aug 1:306:119464. doi: 10.1016/j.envpol.2022.119464. Epub 2022 May 12.

Authors

Yuanping He¹, Lei Li¹, Haolin Wang¹, Xinqi Xu¹, Yuman Li¹, Shaojia Fan²

Affiliations

¹ School of Atmospheric Sciences, Sun Yat-sen University, Zhuhai, 519082, China; Guangdong Provincial Observation and Research Station for Climate Environment and Air Quality Change in the Pearl River Estuary, Key Laboratory of Tropical Atmosphere-Ocean System, Ministry of Education, Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, 519082, China.
² School of Atmospheric Sciences, Sun Yat-sen University, Zhuhai, 519082, China; Guangdong Provincial Observation and Research Station for Climate Environment and Air Quality Change in the Pearl River Estuary, Key Laboratory of Tropical Atmosphere-Ocean System, Ministry of Education, Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, 519082, China. Electronic address: eesfsj@mail.sysu.edu.cn.

PMID: 35569620
DOI: 10.1016/j.envpol.2022.119464

Abstract

In this study, the spatiotemporal variabilities and characteristics of ozone (O₃) and fine particulate matter (PM_2.5) were reconstructed, and the interaction between meteorological conditions and the co-occurrence of O₃ and PM_2.5 in Zhuhai, a city in the Pearl River Delta (China), was analysed. The vertical distributions of lower tropospheric O₃, aerosol extinction coefficient, and wind velocity were measured using a ground-based LiDAR system. The diurnal variations in air pollutant concentrations and meteorological conditions at ground level were examined from 28 November to December 8, 2020 considering the weather conditions in Zhuhai. Heavy pollution episodes with increased concentrations of O₃ and PM_2.5 were observed from 6 to 7 December after a period of cold air invasion. The maximum hourly average concentrations of O₃ and PM_2.5 at the ground level reached up to 190 μg/m³, 98 μg/m³, respectively. The horizontal wind speed rapidly decreased to less than 2 m/s during the heavy pollution episodes driven by O₃ and PM_2.5, whereas the vertical wind velocity was dominated by the downdraught. When the large-scale synoptic winds were weak, a strengthening sea breeze in the afternoon could promote the landward propagation of warm marine air masses, and a lower surface wind speed was driven by the convergence of cold air from the north and warm air from the south. In turn, this increased the residence time of air pollutants and promoted their conversion to secondary pollutants. Regarding the pollution sources, the results indicated that the Pearl River Estuary represented a 'pool' of O₃ and PM_2.5 pollution. In addition, the contribution of regional pollutant transport could not be ignored when considering the accumulative increase in air pollution. Overall, the relatively weak synoptic winds, low mixing height, and high generation of pollution around Zhuhai collectively resulted in high concentrations of O₃ and PM_2.5.

Keywords: Aerosol; Air pollution; Cold air; Downdraught; Ozone; Pearl River Delta.

MeSH terms

Air Pollutants* / analysis
Air Pollution* / analysis
China
Environmental Monitoring / methods
Ozone* / analysis
Particulate Matter / analysis
Rivers

Substances

Air Pollutants
Particulate Matter
Ozone