Study On The Interaction Between Atmosphere Particulate Matter And Near-surface Ozone In Beijing In Recent Years

Atmospheric particulate matter and near-surface ozone are currently the core pollutants of Beijing’s atmospheric composite pollution.The coordinated control of atmospheric particulate matter and ozone is the key to the continuous improvement of air quality.In recent years,the concentration of atmospheric particulate matter in Beijing has shown a clear downward trend,but near-surface ozone pollution has become increasingly prominent,and has become the main air pollutant that affects the improvement of Beijing’s ambient air quality.There is a very complicated relationship between atmospheric particulate matter and ozone,not only do they share common precursors,but they can interact in the atmosphere in a variety of ways.This study used the monitoring data of ambient air pollutants in Beijing in recent years and the observation data from the field,combined with a variety of analytical methods,to study the interaction between atmospheric particulate matter and near-surface ozone in Beijing.The main research conclusions are as follows:From 2016 to 2019,the annual evaluation values of PM2.5 and PM10 in Beijing both showed a downward trend year by year.The average annual decline rates of the annual evaluation values of PM2.5 and PM10 were 9.73μg/m3 and 9.88μg/m3,respectively.The annual evaluation value of ozone also decreased year by year,and the concentration remained between 190 and 200μg/m3,far exceeding the Secondary standard.Atmospheric particulate matter in Beijing is more frequently polluted in spring and winter,with the highest frequency of pollution in March;ozone pollution occurred most frequently in June and July;in addition,the simultaneous pollution of atmospheric particulate matter and ozone mainly occurred in April,May and September.In summer,PM2.5 and ozone concentration showed a tendency to increase or decrease at the same time,and the daily mean value of PM2.5 and MDA8 O3 showed a significant positive correlation;in winter,as the PM2.5 concentration increases,the ozone concentration gradually decreases,and the daily mean value of PM2.5 and MDA8 O3 showed significantly negative correlation.Meteorological factors have a certain effect on the relationship between atmospheric particulate matter and ozone.PM2.5 and ozone showed the characteristics of simultaneous increase or decrease under high temperature and low humidity conditions;while under low temperature and low humidity conditions,ozone concentration decreased as PM2.5 increased.The temporal and spatial variation of atmospheric oxidant(Ox)concentration in Beijing was summer>spring>autumn>winter,traffic pollution monitoring site>urban site>suburban site>background site.The degree of photochemical reaction activity and atmospheric oxidation capacity have a greater impact on the formation of secondary particles.When the degree of photochemical reaction activity and atmospheric oxidation capacity was stronger,the mass concentration of the secondary PM2.5 component was higher,and it accounted for a greater proportion of the total PM2.5 mass concentration.During the enhanced field observation period,the average value of secondary inorganic salts(NO3-,SO42-and NH4+)in the PM2.5 component accounted for 76.1%of the total mass concentration of water-soluble inorganic ions Strong atmospheric oxidizability could improve the conversion rate of secondary inorganic ions in the atmosphere.The higher the concentration of atmospheric oxidant Ox,the higher the corresponding sulfur conversion rate and nitrogen conversion rate,thereby promoting the growth of PM2.5 concentration.During the enhanced field observation period,Beijing’s aerosols were mainly scattered aerosols,and absorption aerosols accounted for a relatively small amount.When the PM2.5 concentration was high,due to the increase in the scattering coefficient and the decrease in the backscattering fraciton,the scattering effect of atmospheric particulate matter promotes the enhancement of near-surface solar radiation.When the value of aerosol optical depth was large,the NO2 photolysis rate could be significantly reduced,while when the single scattering albedo value was large,the NO2 photolysis rate could be increased.When TVOCs and NO2 concentrations were low,changes in the optical properties of atmospheric particulate matter were the main factors that caused changes in ozone concentration.The enhancement of the scattering effect of atmospheric particulate matter on solar radiation had led to a rapid increase in ozone concentration.In addition,when TVOCs and NO2 concentrations were low,both the scattering coefficient and the backscattering fraction showed a significant correlation with ozone concentration.This paper demonstrated the mutual influence between the two aspects of the effect of atmospheric oxidizability on atmospheric particulate matter and the effect of atmospheric particulate matter optical properties on ozone pollution.Ozone concentration could affect the generation of secondary particles by affecting the atmospheric oxidizing ability;the optical characteristics of atmospheric particulate matter could affect the generation of ozone by changing the solar radiation intensity and the rate of NO2 photolysis;in addition,it is found that the atmospheric particulate matter and ozone concentration in Beijing from 2016 to 2019 have a good correlation,indicating that the complex interaction between atmospheric particulate matter and ozone caused them to have a close relationship.Therefore,when formulating the control strategy of atmospheric particulate matter and ozone pollution in the future,the interaction between them should be fully considered,which will be beneficial to the cooperative control of atmospheric particulate matter and ozone.