| In recent years,with the rapid development of social economy and the acceleration of urbanization,the problem of air pollution is becoming more and more serious.In order to master the current situation of air pollution in Guangxi,explore the influence of different weather types on air quality,and better serve the prevention and control of air pollution,the research work was carried out.The characteristics of air pollution in Guangxi were systematically understood by analyzing the fine and good rate,the change of Aqi and primary pollutants in Guangxi from 2015 to 2019,and the spatial and temporal distribution of six pollutants(SO2,NO2,CO,O3,PM10,PM2.5),based on the principle of Synoptic Science,this paper classifies the general circulation situation of air pollution process by using the method of subjective and objective classification,and sums up 10 kinds of synoptic types that are easy to cause polluted weather,at the same time,two typical air pollution processes are selected as an example to analyze deeply.Based on the current situation of air pollution,the effects of different weather types on air quality are studied:1.In the past five years,the concentrations of the other five pollutants except O3have decreased year by year,and the ambient air quality in Guangxi has improved on the whole,but the pollution days and concentration of O3have increased year by year.In 2019,the number of pollution days with O3as the primary pollutant exceeded PM2.5,for the first time in the past five years(53.9%of O3and 45.6%of PM2.5),indicating that the compound air pollution with O3as the primary pollutant has become increasingly prominent.2.The temporal and spatial distribution characteristics of main air pollutants such as PM2.5and O3in Guangxi are significantly different.?1?interannual variation:the total concentration of O3increased year by year,while PM2.5showed a downward trend year by year?except for a rebound in 2017?.?2?seasonal variation:the concentration of O3was the highest in autumn,followed by summer and spring,and the lowest in winter;the concentration of PM2.5was the highest in winter,followed by spring and autumn,and the lowest in summer;?3?monthly variation:the concentration of O3was the highest from September to October and relatively low in other months,and the concentration of PM2.5was the highest in January and December,the lowest in June and August,and the lowest in other months.?4?diurnal variation:the diurnal variation of O3concentration showed a single peak,and the peak appeared around 16:00 in the afternoon,which was inversely correlated with NO2concentration,indicating that O3was mainly produced locally,while the diurnal variation of PM2.5concentration showed a double peak,with the main peak around22:00 at night and the second peak around 11:00 in the morning,generally speaking,and the concentration at night was higher than that in the daytime.?5?Spatial distribution:the high value area of O3concentration gradually expanded from some cities in northern and southern Guangxi to the whole Guangxi in 2019,showing continuous and regional pollution,and the value of PM2.5concentration in the north was higher than that in the south.3.According to the statistics on the types of polluted weather in Guangxi in the past five years,it is concluded that the weather types causing regional pollution in Guangxi mainly include 10 types:High Pressure Ridge type,south wind type,south wind type with other weather types,high pressure rear type,cold air supplement type,shear line with other weather types,Horse latitudes type,southwest warm low pressure with other weather types,mean pressure field type,typhoon periphery type,etc.the proportion of various weather types in the total number of days of regional pollution was 39.4%,17.7%,12.9%,8.3%,5.8%,4.8%,4.5%,2.6%,2.3%and1.7%respectively,the high-pressure Ridge type caused the most regional pollution days?about 40%?,and the high-pressure Ridge type,southerly airstream type and southerly airstream combined with other weather types caused 70%regional pollution days.4.Through the analysis of typical PM2.5pollution cases,it is found that the pollution process is influenced by the southerly air current,the front of the South branch trough and the weak cold air,forming high humidity and stable weather,in high humidity,static stability,boundary layer decline and other unfavorable meteorological conditions for the diffusion of pollutants,thus inducing the pollution process.From the point of view of pollution sources,the results show that the primary source of PM2.5pollution is less,and mainly comes from the pollutants emitted from coal,biomass and motor vehicle exhaust,it is also accompanied by long-distance transport of pollutants,thus triggering the pollution process with PM2.5as the primary pollutant.5.Through the analysis of O3pollution cases,it is found that the high temperature,low humidity and stable weather near the ground surface is favorable for O3local formation under the influence of the subsiding air flow around the typhoon,thus causing O3pollution weather as the primary pollutant.At the same time,the air sinks more strongly,carrying O3from the upper atmosphere down,resulting in a nighttime O3concentration peak without photochemical reaction.Overall,the O3pollution process is mainly due to local formation and transmission from high altitude down. |
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