Preliminary Study On Allowable Emissions Of Main Air Pollutants Based On The CMAQ Model Under The PM_2.5 Standard Of Tianshui City

With the continuous advancement of my country’s industrialization and urbanization,the problem of complex atmospheric pollution represented by fine particulate matter(PM_2.5)has become increasingly prominent and has become one of the major environmental problems my country is currently facing.Due to its unique topographical conditions（valley city）,meteorological conditions（long heating period in winter and spring,frequent sand and dust weather）and industrial layout（mostly concentrated in the main urban area）of Tianshui City,PM_2.5frequently occurs in the main urban area in winter and spring.The daily average concentration exceeds the standard.This study uses ventilation coefficient and comprehensive index of ambient air quality to analyze the meteorological conditions of Tianshui City in recent years,and determines 2017 as the base year for unfavorable meteorological conditions.On this basis,the MEIC list is localized and established.The emission inventory of air pollution sources with a resolution of 3 km in Tianshui City,combined with the meteorological field-driven CMAQ model simulated by the WRF model,studied the allowable emission of major air pollutants in Tianshui City under the PM_2.5standard.The results show that:（1）The emissions of CO,NOx,SO₂,NH₃,VOCs,PM_2.5,and PM₁₀in Tianshui City in 2019 were 214077.82 t,7259.00 t,14437.84 t,11644.55 t,11519.75 t,19672.63 t,and 58772.93 t,respectively;the dust source was PM_2.5The main primary emission source is 45%,followed by fossil fuel combustion sources;road dust accounts for 80.68%of the dust sources,and civil scattered coal sources account for95.65%of the fossil fuel combustion sources;the air pollution sources in Tianshui City are emitted by the main urban area.main.（2）The spatial distribution of PM_2.5in Tianshui City is high in the main urban area and divergent,which is more consistent with the distribution of the road network in Tianshui City;PM_2.5pollution is the most serious in January,followed by April and October,and ambient air quality in July up to standard;on the basis of the existing pollution source structure,the allowable emissions of SO₂,NOx,NH₃,and PM_2.5in Tianshui City under the PM_2.5standard are obtained by reducing iterative simulation:4912.29 t,1720.59 t,2779.64 t,3337.56 t in January;in April,it was 926.53 t,930.31t,392.59 t,and 2563.38 t;in July,it was 1081.89 t,1098.24 t,1396.27 t,and 3083.99 t;in October,it was 948.56 t,924.34 t,1199.88 t,and 2357.33 t.（3）In order to realize that the PM_2.5concentration in Tianshui City meets the requirements of ambient air quality standards under unfavorable meteorological conditions,the main urban area is taken as the main emission reduction area,and the primary emission reduction pollutant is PM_2.5.PM_2.5in January,April and October The reduction ratios are 86.83%,61.41%and 65.21%respectively,and the focus should be on controlling road dust and PM_2.5generated by the burning of scattered coal from civilian sources.