Fog scavenging of particulate matters in air pollution events: Observation and simulation in the Yangtze River Delta, China

Junlong Qian; Duanyang Liu; Shuqi Yan; Muning Cheng; Rongwei Liao; Shengjie Niu; Wenlian Yan; Shuyao Zha; Lulu Wang; Xiaoxiao Chen

doi:10.1016/j.scitotenv.2023.162728

Fog scavenging of particulate matters in air pollution events: Observation and simulation in the Yangtze River Delta, China

Sci Total Environ. 2023 Jun 10:876:162728. doi: 10.1016/j.scitotenv.2023.162728. Epub 2023 Mar 13.

Authors

Junlong Qian¹, Duanyang Liu², Shuqi Yan³, Muning Cheng⁴, Rongwei Liao⁵, Shengjie Niu⁶, Wenlian Yan⁷, Shuyao Zha⁸, Lulu Wang⁸, Xiaoxiao Chen⁸

Affiliations

¹ Key Laboratory of Transportation Meteorology of China Meteorological Administration, Nanjing Joint Institute for Atmospheric Sciences, Nanjing 210041, China; State Key Laboratory of Severe Weather, Chinese Academy of Meteorological Sciences, Beijing 100081, China; Wuxi Meteorological Bureau of Jiangsu Province, Wuxi 214101, China.
² Key Laboratory of Transportation Meteorology of China Meteorological Administration, Nanjing Joint Institute for Atmospheric Sciences, Nanjing 210041, China; State Key Laboratory of Severe Weather, Chinese Academy of Meteorological Sciences, Beijing 100081, China. Electronic address: liuduanyang@cma.gov.cn.
³ Key Laboratory of Transportation Meteorology of China Meteorological Administration, Nanjing Joint Institute for Atmospheric Sciences, Nanjing 210041, China.
⁴ Collaborative Innovation Center of Atmospheric Environment and Equipment Technology, Jiangsu Key Laboratory of Atmospheric Environment Monitoring and Pollution Control (AEMPC), Nanjing University of Information Science & Technology, Nanjing 210044, China.
⁵ State Key Laboratory of Severe Weather, Chinese Academy of Meteorological Sciences, Beijing 100081, China.
⁶ College of Safety Science and Engineering, Nanjing Tech University, Nanjing 211816, China.
⁷ Key Laboratory of Transportation Meteorology of China Meteorological Administration, Nanjing Joint Institute for Atmospheric Sciences, Nanjing 210041, China; Jiangsu Meteorological Observatory, Nanjing 210041, China.
⁸ Wuxi Meteorological Bureau of Jiangsu Province, Wuxi 214101, China.

PMID: 36921860
DOI: 10.1016/j.scitotenv.2023.162728

Abstract

Stable atmospheric boundary layer is conducive to the accumulation of atmospheric pollution and the occurrence of fog, and fog has a removal effect on air pollution. In this study, we use the observation and WRF-Chem (Weather Research and Forecasting Model with Chemistry) simulation to analyze the factors affecting the removal efficiency in a continuous fog and haze episode from November 26 to 28, 2018 in Jiangsu Province, such as fog thickness and duration. The results show that the WRF-Chem simulation well reproduces the boundary layer characteristics in the stages of fog formation, development and dissipation. The atmospheric boundary layer provides favorable conditions for the maintenance of fog and air pollution. The inversion layer, with the maximum intensity of 3 °C per 100 m, creates favorable thermal conditions, and the water vapor advection is also conducive to the fog maintenance. The ground observation verifies the wet scavenging of PM_2.5 during dense fog events. The scavenging effect is related to the fog duration, and the correlation is positive when the fog is just formed and negative when the fog is dissipating. The PM_2.5 concentration decreases from 159 μg m^-3 to 38 μg m^-3 after the fog lasts for 11 h. The fog has a remarkable scavenging effect on PM_2.5 in the vertical direction, due to the deposition effect of fog droplets on the pollutant particles. The PM_2.5 concentration on the ground is lower than the vertical average in the fog area, and the scavenging effects during the dense fog periods on November 27 and 28 are 47.7 μg m^-3 and 36.1 μg m^-3, respectively. The fog duration is mostly concentrated in 3-17 h. When the duration of fog is 4-8 h, the scavenging effect on PM_2.5 reaches the strongest, with an average PM_2.5 concentration decrease of >70 μg m^-3.

Keywords: Air pollution; Fog; Model simulation; WRF-Chem; Wet scavenging.