Research On The Characteristics Of Air Pollution In Typical Cities In The Sichuan Basin And The Impact Of Precipitation On Them

Mountainous?bath?cities prone to heavy air pollution has become a common problem in the world.The average altitude of the Sichuan Basin is about 500 meters,and it has a unique basin climate characteristics-small annual wind speed,high static wind frequency,short sunshine hours,and winter Inversion phenomenon occurs frequently.In recent years,with the rapid economic development,increasing energy consumption and accelerating urbanization,local pollution problems have become increasingly serious.This has led to a continuous deterioration of local air quality.This problem has caused widespread problems among local governments and related scientific and technical workers.attention.Based on the unique climate characteristics of the basin,precipitation plays an important role in the removal of local pollutants.However,compared with other heavily polluted areas in our country,the research on the removal efficiency of precipitation on the Sichuan Basin is still very rare and needs to be studied in depth.Four types of polluted cities in Chengdu Basin,Chongqing,Dazhou and Zigong in the Sichuan Basin are used to measure the daily airborne pollutant concentration data from 2014 to 2016 and the daily hourly precipitation data for the same period.Based on the respective changes in the concentration of pollutants(SO₂,NO₂,PM₁₀,PM_2.5,and CO)and precipitation,the focus was on the removal efficiency of different pollutants on different pollutants,and the following main results were obtained:?1?The mass concentrations of five pollutants(PM₁₀,PM_2.5,SO₂,NO₂,and CO)in the representative cities decrease from 2014 to 2016;Zigong has the worst air quality,followed by Chengdu and Chongqing,and Dazhou has the best air quality;The main air pollutants are particulate pollutants(PM_2.5.5 and PM₁₀);The annual variations of the quality of the five pollutants showed a"U"type overall,and the heavy pollution period occurred in the winter,Based on the basin unique climate characteristics,the diurnal variation of PM_2.5,PM₁₀,NO₂ and CO concentrations was bimodal,while that of SO₂ was unimodal,with the minimum concentration occurring at 5⁷am.?2?The precipitation in the four typical representative cities in the basin are concentrated in the summer.In terms of precipitation,Chongqing is the most,followed by Dazhou and Chengdu,and Zigong is the least.The hourly precipitation shows a typical”night rain”feature.?3?As far as the frequency of different grades of precipitation is concerned,Chengdu City and Dazhou City all show:light rain>micro precipitation>moderate rain>heavy rain>rainstorm;Chongqing:light rain>moderate rain>heavy rain>micro precipitation>rainstorm;Dazhou light rain>moderate rain>micro precipitation>heavy rain>rainstorm shows that the frequency of occurrence of moderate rain is highest in all four cities.?4?For different levels of precipitation on the removal efficiency of pollutants,different levels of precipitation in different cities have some differences in the removal efficiency of pollutants.Among them,the order of Chengdu's removal efficiency is rainstorm>moderate rain>heavy rain>light rain;in Chongqing,the clearing rate increases from heavy rain to rainstorm with increasing precipitation.The study also found that the maximum removal rate of pollutants in continuous precipitation occurred on the 2nd day,and then the removal efficiency decreased gradually.However,in terms of precipitation efficiency per unit time,the precipitation is obviously greater than the continuous precipitation.The results of this study deepen the understanding of the removal efficiency of pollutants in different grades of precipitation,and provide a reference for the reasonable pollution prevention and control.