Study On The Physical And Chemical Characteristics Of Atmospheric Fine Particles Under The Environment Of High Concentration Ozone

In recent years,Guangdong Province has made positive progress in air quality.As of 2019,Guangdong's ambient air quality has achieved overall standards for five consecutive years,and the average annual concentration of PM2.5 has dropped from 47 ?g·m-3 in 2013 to 27 ?g·m-3 in 2019 at the leading level in the country.The concentration of O3 in the Pearl River Delta region has not decreased but has risen.It has shown an upward trend since 2005.O3 pollution has gradually become the primary pollutant that affects the air quality in the Pearl River Delta region,especially in autumn.The problem of O3 pollution is the most serious.PM2.5 and O3 pollution are related to the secondary air pollution problem.VOCs and NOx are important precursors formed by PM2.5 and O3.Promoting VOCs and NOx synergistic emission reduction and strengthening PM2.5 and O3 cooperative control are Current important tasks.Studies have shown that reducing the concentration of PM2.5 may aggravate the O3 pollution situation,and high O3 concentration also leads to the rapid generation of PM2.5.Therefore,we need to further explore the relationship between O3 pollution and particulate matter,and analyze the possible causes of PM2.5 at high concentration O3,in order to provide data support for the collaborative control of PM2.5 and O3 in the Pearl River Delta region.This paper mainly uses a single particle aerosol mass spectrometer and other instruments to comprehensively analyze the ambient air quality status of the Guangdong Atmospheric Super Monitoring Station in 2018 and 2019,focusing on the physical and chemical characteristics of particulate matter under high concentration O3 in October.The main conclusions are as follows:1)The main pollutants in Heshan City in 2018 and 2019 are O3 and PM2.5,and the days of O3 as the main pollutant is much more than PM2.5.The proportion of days with main pollutants in 2018 was 44.9%(102 days)and 35.7%(81 days),respectively,in 2019 they were 48%(94 days)and 28.4%(55 days).In October,the pollution was serious and mainly O3 pollution.The average concentration of O3 in October 2018 was 200 ?g·m-3,the average concentration of PM2.5 was 50 ?g·m-3,and the average concentration of O3 in October 2019 was 184 ?g·m-3.,The average concentration of PM2.5 is 40?g·m-3,indicating that the high concentration of O3 in the Pearl River Delta region has a certain effect on the generation of PM2.52)At high concentration O3 period,atmospheric fine particles are mainly secondary aging particles,including Sec,OC-aged and ECOC-aged particles,and the concentration of Sec particles is significantly higher than that of low concentration O3 period.In 2018,the main types of particulate matter are EC-aged,Sec and OC-aged particles.In 2019,the main types of particulate matter are EC-aged,Sec and ECOC-aged particles.These three categories account for more than 80%of the total particulate matter.In 2018,the concentration of EC-aged particles in high concentration O3 period was 32.1%lower than that in low concentration O3 period,44.1%,Sec particles accounted for 37.1%higher than low concentration O3 period,27.8%,OC-aged particles accounted for 13.5%higher than low concentration 10.4%during the O3 period.The EC-aged particle number concentration in 2019(55.6%)is higher than the high-concentration O3 period in 2018(32.1%),the Sec particle number concentration(24%)is lower than the 2018 high concentration O3 period(37.1%),OC-aged particles The number concentration(3.8%)is lower than the high concentration O3 period(13.5%)in 2018,and the ECOC-aged particle number concentration(9.8%)is slightly higher than the high concentration O3 period(9.3%)in 2018 Except for EC-aged particles,the change trend of the concentration of main particles is similar to that of the corresponding O3 concentration,indicating that the formation of Sec,OC-aged and ECOC-aged particles is related to high concentration of O33)The content of secondary organic aerosol in single particles increased significantly during the period of high concentration O3.The proportion of nitrate-containing particles in the secondary particles at high concentration O3 period is higher than that of sulfate particles,indicating that the photochemical reaction has a greater impact on nitrate formation and aging than sulfate.In addition,through the quantitative analysis of the concentration of the particles containing 59CH3CO2-and 73C2HO3-combined with the quantitative analysis of the mass concentration of OC and SOC,it was found that the concentration of the single particles containing secondary organic matter was consistent with the characteristics of the mass concentration of secondary organic carbon.The peak concentration appears between 17:00-20:00,a few hours behind the peak ozone concentration,indicating that the photochemical reaction of organic precursors in the high concentration ozone environment has an important contribution to the formation of secondary organic aerosols.In summary,the pollution of O3 in Heshan City is relatively serious.In high concentration O3 environment,PM2.5 generates more secondary particles and promotes the formation of secondary organic particles.