Ozone Pollution Characteristics In The Main Urban Area Of Lanzhou City Based On CMAQ Model And MEIC

In this paper,The time-distribution characteristics of air pollutant concentration and the spatial distribution characteristics of O₃ concentration in the main urban area of Lanzhou City are analyzed by using the data of hourly atmospheric pollutants monitoring and the daily data of the micro-station in Lanzhou City in 2018.The high-precision GDP and population network grid data are used to refine the MEIC emission inventory list and then the Lanzhou inventory list is established.Based on the meteorological field simulated by the inventory list and the WRF model（the NCEP reanalysis meteorological data provides the initial boundary）,the CMAQ model（Community Multiscale Air Quality model）is used to simulate the primary ozone pollution in the main urban area.The ozone characteristics are analyzed by IRR and IPR process analysis technique.The results show that:i.In 2018,the ozone concentration in the main urban area of Lanzhou City is high in summer and low in winter,high in June during the 12 month and high att 2-3.p.m.in a day.The interpolated value of ozone concentration in the micro-site shows that the ozone concentration in the main city in June shows spatial distribution characteristics of high in the west and low in the east,high in the north and low in the south.ii The detailed MEIC emission inventory list shows that the total emissions for NO_X、PM_2.5、PM₁₀、NH₃、VOC、SO₂、CO in Lanzhou in 2016 are:8.39×10⁴、2.36×10⁴、3.35×10⁴、1.04×10⁴、8.36×10⁴、3.44×10⁵（tons）.iii.Study on the ozone episode using CMAQ shows low concentration value,but reflects the actual trend and spatial distribution of ozone,and the simulated ozone concentration error during the day is within a reasonable range;iv.The sensitivity study of regional ozone based on the photochemical indicator p（H2O2）/p（HNO3）shows that most of the time zone in Lanzhou City is affected by VOC control area（p（H₂O₂）/p（HNO₃）<0.35）,except for the core area,the northern and southern borders changed from 10-11 pm to 1 pm on June 10 to NOx sensitive area,so reducing ozone concentration requires two measures:the core area of the city controls VOC,and the NOx is controlled at the north and south borders;the clean spot at the suburbs is NOx sensitive area when it is 15-20,and the other is also the VOC sensitive area.v.The results of IPR process analysis show that the horizontal and vertical transport processes contribute the most to the ozone concentration in the main urban area and the suburb.The horizontal transmission contributes positively to the ozone concentration in the main urban area during the daytime,while the vertical transport is the opposite;the chemical process has large consumption amount when ozone is consumed for 14 hours.vertical diffusion is the opposite.The two processes contribute more to the main urban area compared with the suburb.Under the premise of better WRF simulated meteorological field,the simulated precipitation and the 500hpa weather situation of reanalysis data indicate that the ozone pollution process occurred under the typical favorable ozone generation weather situation in a sunny day with cloudless sky after a precipitation.