Multilevel air quality evolution in Shenyang: Impact of elevated point emission reduction

Yanjun Ma , Xiaolan Li , Guiqian Tang , Liguang Li , Weijun Quan , Yangfeng Wang , Ziqi Zhao , Ningwei Liu , Ye Hong


Received November 17, 2020,Revised , Accepted May 27, 2021, Available online July 05, 2021

Volume 34,2022,Pages 300-310

Visibility observed at different altitudes is favorable to understand the causes of air pollution. We conducted 4-years of observations of visibility at 2.8 and 60 m and particulate matter (PM) concentrations from 2015 to 2018 in Shenyang, a provincial city in Northeast China. The results indicated that visibility increased with the increasing height in winter (especially at night), and decreased with height in summer (especially at the daytime). PM concentration exhibited opposite vertical variation to visibility, reflecting that visibility degrades with the increase of aerosol concentration in the air. The radiosonde meteorological data showed that weak turbulence in the planetary boundary layer (PBL) in winter favored aerosols’ accumulation near the surface. Whereas in summer, unstable atmospheric conditions, upper-level moister environment, and regional transport of air pollutants resulted in the deterioration of upper-level visibility. Inter-annual variation in the two-level visibility indicated that the upper-level visibility improved more significantly than low-level visibility, much likely due to the reduction in emission of elevated point sources in Shenyang. Our study suggested that strengthening the control of surface non-point emissions is a promising control strategy to improve Shenyang air quality.

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