Research On PM_2.5 Pollution Characteristics And Regional Transmission In Jingzhou City In Recent Years

As a core city in the Jianghan Plain in the middle reaches of the Yangtze River Basin,Jingzhou City is facing the problem of PM_2.5pollution of atmospheric fine particles that urgently needs to be studied in depth.This study uses the observation data of air pollutants and conventional meteorological elements in Jingzhou from January 2015 to December2020 to conduct a statistical analysis of the state of air pollution in Jingzhou,mainly analyzing the annual,seasonal and daily changes of air pollutants.Change characteristics,excessive rate of air pollutants and the impact of meteorological conditions on air pollutants;focus on the analysis of the most severely polluted PM_2.5change characteristics,and discuss the special effects of precipitation and wind farms on PM_2.5pollution;combined with FLEXPART-The 10-year simulation study of the WRF model reveals the temporal and spatial distribution characteristics of the"influence zone"of the air pollutant source area in Jingzhou City,determines the main air pollutant transmission channels in Jingzhou City,and quantifies the local emissions and emissions during typical heavy pollution processes.The relative contribution of regional transmission to PM_2.5pollution.Get the following main conclusions:1)In recent years,air quality changes and haze pollution in Jingzhou area and their meteorological driversThe concentrations of PM_2.5,PM₁₀,NO₂,SO₂and CO in Jingzhou are higher in winter and lower in summer,while O₃is higher in summer and lower in winter.The peaks of PM_2.5,PM₁₀,CO,SO₂and NO₂appear in the morning and night,and the peaks of O₃appear in the afternoon.Among the air pollutants in Jingzhou,fine particles PM_2.5pollution is the most serious,followed by photochemical pollution of coarse particles PM10 and O₃,and NO₂pollution is lighter,and there is no SO₂and CO pollution.The main atmospheric over-standard substances in Jingzhou are PM_2.5,PM₁₀,O₃and NO₂.CO and SO₂have not exceeded the standard.Among them,particulate matter has the most serious over-standard,especially the fine particle PM_2.5,which has an over-standard rate of 54.61%in winter.Jingzhou City,located in the East Asian monsoon region,has four distinct seasons.The main meteorological elements have obvious seasonal changes:temperature is high in summer and low in winter,with an annual average temperature of 17.5?;relative humidity does not change much,fluctuates around 78.%of the annual average;wind speed is the largest in spring;Winter>spring>autumn>summer;rainfall is abundant,and precipitation is concentrated in April to August.Meteorological conditions have a significant impact on the changes in the concentration of air pollutants in Jingzhou.Temperature,humidity and wind speed are the main factors affecting the changes in the concentration of air pollutants in Jingzhou.2)The special role of near-surface wind field driving and precipitation removal during the change of PM_2.5pollution in JingzhouThe PM_2.5pollution incidents in Jingzhou mainly occurred in winter,spring and autumn,among which severe PM_2.5pollution incidents mainly occurred in winter.The strong northeasterly wind of the East Asian winter monsoon was accompanied by high concentrations of PM_2.5pollution in Jingzhou,revealing the role of the regional transmission of air pollutants driven by the East Asian winter monsoon in the heavy pollution incident in Jingzhou.Severe pollution incidents in Jingzhou can be generated and dissipated throughout the day,and overall pollution incidents lasted for a short time.Light rain intensity precipitation does not have a significant effect on the moisture removal of PM_2.5,but causes the moisture absorption of PM_2.5to increase,and the concentration rises;when the precipitation intensity reaches more than moderate rain,the rainfall has obvious effects on the fine particles of PM_2.5in the atmosphere.Wet removal effect indicating the special atmospheric environmental effect of precipitation in the humid area of the middle reaches of the Yangtze River.3)The contribution of air pollution regional transmission to Jingzhou haze pollution and the climatic characteristics of PM_2.5"influence zone"The main"influence areas"of PM_2.5in Jingzhou are Hubei,Hunan,Henan and Anhui provinces.In different seasons,the contribution rate of Hubei Province's external transmission to Jingzhou's PM_2.5"influence zone"was 50.4%in spring,33.9%in summer,42.6%in autumn,and 43.0%in winter.The three regional transmission channels in spring are(1)north channel(along Nanyang Basin-Jingzhou),(2)eastern channel(along the Yangtze River channel-Jingzhou),and(3)southern channel(along Xuefeng Mountain-Jingzhou);in summer,they are mainly from south Northern Passage:(1)Northern Passage,(2)Northeast Passage(along the low hills of Dabie Mountain-Jingzhou)and(3)East Passage in autumn and winter.The analysis of the"influence area"of typical cases of PM_2.5regional transmission in the main winter heavy pollution weather in Jingzhou shows that the main source of high-pressure static PM_2.5pollution is local emissions,and the contribution rate in the province is as high as87.8%;low-pressure inverted channel PM_2.5Pollution mainly comes from southward transportation and local accumulation.The contribution within and outside the province is equivalent,with a contribution rate of 55.0%within the province and a contribution rate of45.0%outside the province;the main source of PM_2.5pollution transported by cold fronts is regional transmission in the northerly direction.,The contribution from outside the province is as high as 77.2%.During the heavy PM_2.5pollution in winter,regional transmission from outside the province dominates the occurrence of heavy PM_2.5pollution in Jingzhou,highlighting the importance of joint prevention and control of air pollution within and outside the province.