Study On The Temporal And Spatial Characteristics Of Ozone Pollution In Wuhan Based On CMAQ Model

In recent years,Wuhan is in a state of rapid development,facing severe ozone pollution,especially in the summer,the number of days of excessive ozone remains high.Excessive O₃ in the air will do great harm to human health and building materials,so it is necessary to study the mechanism and influencing factors of ozone pollution.Based on the meteorological data and pollutant monitoring data of Wuhan from January 2018 to February 2019,this paper analyzes the spatial and temporal distribution characteristics of O₃ pollution in Wuhan,and studies the correlation between O₃,meteorological elements and other air pollutants;Based on the high-precision grid data of population distribution,time distribution spectrum and chemical species distribution spectrum,combined with ISAT inventory processing tool,this paper realizes the time-space distribution and chemical species distribution of MEIC（multi-resolution emission inventory for China）,and generates a high-resolution air pollutant emission inventory in Wuhan area;Based on the list and the meteorological field simulated by WRF model,CMAQ（community multiscale air quality）was used to simulate the ozone pollution distribution in Wuhan from June 1 to June 7,2018,and the simulation results were evaluated by using relevant statistical indicators.The main conclusions of this paper are as follows:（1）In 2018,the peak of monthly average concentration of O₃ and days exceeding the standard in Wuhan is from April to October,and the peak appears in June;the concentration of O₃ presents a"single peak"feature in a day,higher in the daytime than at night,and the peak appears around 14:00 p.m.In terms of spatial distribution,the areas with high concentration of O₃ in Wuhan are concentrated in the north,East,northeast and southwest corner.As a whole,the concentration of O₃ in the far urban area is higher than that in the main urban area.The concentration of O₃ in Wuhan is positively correlated with sunshine duration and temperature,but negatively correlated with wind speed,relative humidity,NO₂,CO,PM_2.5 and PM₁₀.（2）According to the detailed distribution of MEIC list,the total emissions of SO₂,NO_X,VOC,CO,PM_2.5,PMcoarse and NH₃ in Wuhan grid area in June 2016 were 7568.31t,9507.16t,14909.24mol,69710.21t,3992.91t,1377.28t and 8427.22t,respectively.（3）The WRF model has the best simulation effect on the temperature and pressure near the ground in Wuhan,followed by the humidity,and the wind speed is not good because of the complexity of the underlying surface.（4）CMAQ is more accurate in simulating the variation of ozone concentration.O₃ concentration increases with the increase of light intensity and precursor emissions,and decreases rapidly in the evening with the decrease of light intensity and human emissions.Generally speaking,the ozone simulation value is smaller than the measured value.According to the average relative deviation MFB and the average relative error MFE,the ozone simulation concentration of most monitoring stations in Wuhan is in a reasonable acceptable range,while the ozone simulation of a few monitoring stations is not ideal.These stations are concentrated in the far urban area of Wuhan,that is,the partial edge of the simulation area grid.（5）CMAQ model is more reasonable to simulate the spatial distribution characteristics of ozone concentration in Wuhan.The simulated concentration and monitoring concentration show a trend of low concentration in the main urban area and high concentration in the far urban area.At the same time,compared with the measured concentration,the simulated concentration is underestimated to some extent.During the study period,the ozone concentration was in the rising stage from 12:00 to 15:00,and gradually decreased from 15:00 to 18:00,which was in line with the actual trend of daily concentration change.