Analysis Of Characteristics And Typical Cases Of Atmospheric Particulate Matter Pollution In The Southwest Of Chengdu In Winter

With economic development,population growth and accelerated urbanization,air pollution is more severe.Chengdu has always occurred air pollution in winter.The winter concentrations of particulate matters?PM?in Chengdu southweset area from 2014 to 2017,as well as the meteorological data of MICAPS,achive data and HYSPLIT model from NOAA in the same time,were used to get deep insight into the temporal distribution characteristics of PM concentrations and the meteorological factors and circulation background during diffirent air quality band.To research the characteristics in size distribution of chemical components,the composition of PM in typical periods was also analyzed experimentally in the study.The study found that:?1?The concentration of particulate pollution was the most serious in the winter of 2016,including some continuous pulltion process.the average wind speed was 1.2 m/s,the frequency of stable and light wind was 81.5%,and the average relative humidity?RH?was 80%during the research,besides the precipitation was mainly concentrated in the winter of 2015.When the wind speed was less than 1.5m/s,the wind speed was inversely correlated with the PM concentration,otherwise the PM concentration increase beceuse of grund dust.Particle concentration is positively correlated with relative humidity in the absence of precipitation.?2?Particle concentration and precipitation are generally inverse relation,but the clear ability has limited in small rain and accelerate the generation of secondary particles because of high RH.PM concentration declines with the inversion decreased and increased of multi-inversion,which the 925 hPa ground inversion and multi-inversion is the obvious characteristics during heavy pollution,and there also are many internal cluster from sichuan basin caused the air pollution.The trough line near the 500 hPa in excenlent and good?EG?days and weaken in light and medium days?LM?,and When the 500hPa west wind prevailed or behind the trough with sink flow,the area break out the heavy pollution.When the cold air intensity is insufficient,the high-pressure with downdraft will increase of particle concentration.?3?The concentration of water-soluble ions,organic carbon and element carbon increased with the PM concentration.NO₃^-and SO₄^2-have bimodal distribution where NH₄⁺were found only one peaks,and NO₃^-is higher than NH₄⁺in EG and OH days,but on the contrary in LM days.The concentration of OC?EC?NO₃^-?NH₄⁺?SO₄^2-?Cl^-?Na⁺and K⁺were higher in the fine particle?<2.1 m?,but less in the large particles,which NO₃^-and SO₄^2-present bimodal distribution under moderate pollution and maximum concentration of NO₃^-and SO₄^2-is more in 0.65¹.1?m particle,in addition crustal element ions are mainly distributed in coarse matters.The higher the concentration of particulate matter,the higher the concentration of EC in particles<0.43 m.OC/EC values were greater than 2 in all particle sizes,indicating that there is SOC in the PM,and it mainly distributed in fine particle.Particulate matter in southwest of Chengdu is seriously affected by mobile vehicle emission.