Analysis Of Ozone Pollution Characteristics In Shenyang:during The Epidemic Period

Ozone pollution has become the primary pollutant affecting the air quality in spring and summer in economically developed areas of China,and the study on the present situation and influencing factors of ozone pollution is the key to air pollution prevention and control.In 2019,Covid-19 swept the world.In order to cope with the virus,Shenyang adopted a series of epidemic prevention and control measures to protect people’s health,and restricted travel during the control period to minimize pollutant emissions under artificial control.Based on the concentration data and meteorological data of pollutants in monitoring sites in Shenyang,this study studied the current situation of ozone pollution in Shenyang at the pre-epidemic stage（2019）,the control period（2020）and the post-epidemic stage（2021）.The results showed that from 2019 to 2021,the annual average ozone concentration first increased and then decreased,and the ozone exceeding rate was 8%,9%and 3%respectively,and the days exceeding the standard were mainly concentrated in May-September.The change of ozone concentration has obvious seasonal law,and the ozone concentration decreases in summer,spring,autumn and winter.In 2020,the ozone concentration exceeded the standard continuously for more than 3 days for 6 times,which was higher than 4 times and 1time in 2019 and 2021.The highest ozone concentration in a day generally appears around 15 pm;The weekend effect of ozone is the most obvious in 2020,and the ozone concentration on working days is lower than that on rest days.The weekend effect in 2019 and 2021 is not obvious.The spatial distribution law of ozone is that the ozone concentration in the center of the city is lower than that in the periphery of the city,and the ozone concentration in the south and north is higher than that in the east and west.The main influencing factors of ozone include pollutant factors and meteorological factors.This paper discusses the correlation between ozone and various influencing factors from 2019 to 2021.It is found that temperature,low wind speed（<15Km/h）and PM_2.5in summer are positively correlated with ozone.NO₂,CO,PM_2.5in winter,higher wind speed（>15Km/h）and precipitation are negatively correlated with ozone.The nonlinear correlation between each influencing factor and ozone is higher than the linear correlation.HYSPLIT-Meteo Info was used to analyze the 24-hour backward trajectory,potential sources and concentration weight of ozone in Shenyang from 2019 to July 2021.The results showed that the air mass from the south had the greatest influence on the ozone concentration in Shenyang in summer,and the high-value areas where WCWT and WPSF overlapped were mainly concentrated in Dalian,Yingkou,Jinzhou and Huludao in 2019.In 2020,it will be Dalian,Liaoyang,Jilin and North Korea;In 2021,it will be Dalian and Tieling.Among them,in 2020,the potential source area of ozone is the widest and the concentration is the highest.Using the data of ozone concentration from 2014 to 2021,the ozone concentration is predicted by ARIMA time series model.It is found that the ozone concentration in Shenyang will rebound in the next three years compared with 2021,but the ozone concentration is still lower than that before the epidemic began.From2022 to 2024,the ozone concentration showed a downward trend,with the lowest value appearing in winter and the highest value appearing in summer,with obvious seasonal variation.Therefore,the control of ozone concentration should be comprehensively considered in many aspects,and the local NO_x/VOCs reduction ratio should be appropriate.Unreasonable emission reduction will lead to an increase in ozone concentration,and at the same time,joint prevention and control between regions should be strengthened.