Study On Optimal Control Strategy Of Atmospheric Environmental Capacity And PM_2.5 Reaching Standard In Linfen

At present,the overall quality of my country's ecological environment is improving,but some areas still have the problem of a high proportion of days with excessive air pollution and frequent occurrence of heavy polluted weather.In order to further reduce the urban PM_2.5concentration and improve air quality,it is necessary to formulate more scientific control strategies,taking into account the amount of pollutant emission reduction and the cost-effectiveness of emission reduction,and implement precise policies.Linfen is one of the heavily polluted cities in the Fenwei Plain.PM_2.5 is the primary air pollutant.Research on atmospheric environmental capacity and optimization of pollution control strategies has been carried out,and the total pollution emission limit by region and industry has been determined,and the treatment cost should be taken into consideration.And emission reduction plans are very necessary.This article first uses observational data and emission source lists to analyze the air quality and the temporal and spatial distribution of pollutant concentrations and the emission characteristics of pollution sources during the 13th Five-Year Plan(2016-2020)period in Linfen.The analysis found that the air quality in Linfen City has been significantly improved from 2016to 2020,and the severely polluted weather has dropped by 70%.In 2020,the average concentrations of NO_x,SO₂,PM₁₀,PM_2.5,O₃,and CO were 41.4,19.9,94.9,56.6,118.3?g/m³and 1.3 mg/m³,respectively.Compared with 2016,the PM_2.5 concentration dropped by 21.9%,SO2 has a large decrease(75.8%),and the annual average concentration of O₃ has increased by46.5%.According to regional distribution,the central area of Linfen is more polluted,and the western area is lighter,especially in severe and above polluted weather.Cities in the central area account for more than 77%,and the western area only accounts for about 3%.The total emissions of SO?,NO_x,CO,VOCs,NH?,TSP,PM??,PM_2.5,BC and OC in Linfen in 2018 were1466 kt,of which CO(63%),PM??(7.2%)and VOCs(6.3%).The industries with the highest SO₂,NOx,and VOCs emissions are civil combustion(45%),mobile sources(55.1%)and coking industry(54.9%).The total emissions of pollutants in 2020 will be 1222 kt,which is 20%less than in 2018.NH?emissions will increase by 11.5%and VOCs will be reduced by 137.2%.Secondly,based on the regional atmospheric environment model Reg AEMS,combined with the mathematical planning model,the source-receptor influence matrix of different industries and different regional pollution sources in Linfen is calculated,and the atmospheric environment capacity of Linfen in different pollution processes is estimated,and pollution is realized.Two-objective optimization with the largest amount of chemical emissions and the smallest cost of abatement.Studies have shown that for industry sources,moderate-to-severely polluted mobile sources,civil combustion sources,and biomass combustion sources contribute significantly,with relative contributions ranging from 11.8 to 13.6%,11.1 to 12.4%,and 10.5 to11.6%.The relatively large contribution of lightly polluted processes is civil combustion sources and mobile sources,with relative contributions of 12.9-40.7%and 12.5-13.8%.From the perspective of regional source contribution,Xiangfen?Quwo and Hongdong County have higher contributions,with relative contribution rates of 8.6-12.7%,7.4-10.8%,and 6.1-9.6%.The atmospheric environmental capacity of NH₃,NO_x,PM_2.5,SO₂ and VOCs in Linfen during the severe pollution process were 13.8,43.7,95.5,38.6,and 164.7 t/d,respectively,and the medium pollution was 26.9,86.2,126.5,51.6,and 196.7 t/d,light pollution was 44.2,140.6,132.7,48.0,and 180.1 t/d.Quwo?Xiangfen and Hongdong County have larger atmospheric environmental capacity,and Yonghe?Daning and Ji County are common Lower.As pollution intensifies,the atmospheric environmental capacity in the central region has decreased significantly.Finally,according to the emission reduction coefficient obtained by the dual-objective optimization,combined with the emission volume and the emission reduction cost of each industry,the PM_2.5 compliance of 15 industries and 17 regional pollution sources in Linfen City in the process of heavy,medium and light pollution were explored.Optimize emission reduction plans,compare the differences under different PM_2.5 concentration quality targets,and give optimized emission reduction strategies under different pollution situations.The results show that,in order to meet the PM_2.5 concentration level II standard(75?g/m³),under heavy pollution weather conditions where the average PM_2.5 concentration exceeds 200?g/m³,the average emission reduction rate of Linfen City is 69.7?77.5%.The cost is 4.46 to 4.64 million yuan.For the moderately polluted process,the average emission reduction rate is 66.2%,and the emission reduction cost is 2.25 million yuan.For light pollution processes with an average PM_2.5concentration of less than 90?g/m³,the emission reduction rate is 38.9-56.3%,and the emission reduction cost is 0.89-2.75 million yuan.Analyzing the 6 pollution processes,it is found that NO_x emission reduction and emission reduction costs are higher,reducing one-time PM_2.5emission has greater control effect and lower cost.The iron and steel industry has the highest emission reduction cost,and the coking industry has the highest emission reduction cost.With large emission reduction potential and low cost,cement production and industrial boilers are more cost-effective.With the improvement of PM_2.5 concentration standards and the increase of pollution,the proportion of emission reduction and emission reduction costs will increase accordingly.When the source control of other industries reaches the limit,it is better to choose to control electric heating and civil combustion sources effect.The study in this paper is an effective attempt to achieve urban PM_2.5 concentration planning and refined control strategies under the premise of dual goals(maximum allowable emissions and minimum emission reduction costs),which can be applied to other cities'air pollution control countermeasures.