Research On The Response Relationship Between Typical Industrial Source Emissions And PM_2.5 Concentration In Beijing-Tianjin-Hebei Region And The Optimization Of Emission Reduction Technology

Since the implementation of the action plan for the prevention and control of air pollution,the air quality in China has been significantly improved.However,the situation of air pollution prevention and control is still grim.For the Beijing-Tianjin-Hebei(BTH)region,the industry is the main air pollution discharge department.And consequently,it is of great significance to optimally control industrial emissions for the realization of the air pollution control objectives.This study conducted the atmospheric PM_2.5 observation and analyzed the chemical components characteristics in typical cities of BTH,investigated the relationship between industrial industry emission and fine particle concentration,analyzed the meteorological classification and characteristics of severe pollution processes,and established the PM_2.5 optimization control scheme based on the air quality sensitivity analysis of industrial emissions.The PM_2.5 samples in Beijing,Tangshan and Shijiazhuang in January,April,July and October of 2019 were collected.The elements,ions and carbon components(organic carbon and elemental carbon)were analyzed in the laboratory.By means of backward trajectory clustering analysis and PSCF,the potential pollution sources and transmission paths in the three cities were explored.The characteristics of PM_2.5 and VOCs composition spectrum of typical industry sources were analyzed.The industry emission inventory of BTH in 2018 was established based on the emission factors and activity data.The impact of industrial emissions on regional air quality of BTH was carried out under the background of continuous emission reduction in 2013 and 2018by WRF-CAMx numerical simulation.The sensitivity of industrial emissions on PM_2.5concentration was analyzed.The characteristics of air pollutant concentrations under different pollution grades were analyzed.Based on the weather type principal component analysis method,the meteorological types under different pollution levels were classified.Three typical air pollution processes were selected,and by combining the backward trajectory simulation,the pollutant transmission characteristics and pollution causes were analyzed and judged.Finally,based on the method of operational research and linear programming,the optimized control model of industrial emission for PM_2.5 pollution mitigation was developed.Considering both the air pollution impact sensitivity and control the cost of different emission sources,taking improvement of air quality and minimizing the economic cost as objectives,based on the above-mentioned pollution process classification types,the optimized emission reduction plan was proposed for different types of pollution processes.The results showed that PM_2.5 pollution in typical cities of BTH was characterized by temporal distribution of winter>autumn>spring>summer;the annual average concentration of Shijiazhuang and Tangshan was similar,and the PM_2.5 concentration in Beijing was significantly lower.Secondary particles in PM_2.5 were the main components in Beijing,accounting for 42.4%-61.5%of the mass concentration of PM_2.5.The secondary component accounted for the highest proportion in winter(61.5%);secondary organic aerosol(SOA)and nitrate accounted for a relatively higher proportion.The secondary component of PM_2.5 in Shijiazhuang city was higher in summer and autumn,among which sulfate was the main component in summer and nitrate was the main component in autumn.In summer,the proportion of secondary particles in PM_2.5 was the highest in Tangshan(mainly sulfate and nitrate).The main potential source regions of PM_2.5 in spring in Beijing were Tangshan and Southern Hebei,Southern Hebei,Tangshan and Bohai Sea in summer and autumn,and Zhangjiakou in winter.Among them,metallurgical industry was an important industrial emission source in BTH.In 2018,the SO₂,NOx,PM_2.5,VOCs and CO emissions of metallurgical industry were 155000 tons,124000 tons,9500 tons,103000 tons and 6.18million tons,respectively.For the whole BTH,Tangshan,Shijiazhuang,Tianjin and Handan had higher industrial industry concentration contribution rate;for Beijing,the southern four cities and Tangshan,the local contribution rate was significantly higher than that of the surrounding cities.The sensitivity analysis results showed that Shijiazhuang,Tianjin,Baoding were the cities with higher sensitivity in industry emissions,and the sensitivity of per unit pollutant emission in different cites was various;Shijiazhuang was the most sensitive city.In the statistical period 2010-2018,Baoding,Xingtai,Shijiazhuang and Handan had more pollution days.Based on the PCT classification method,the sea level air pressure field and 10m wind field results in severe pollution period of BTH were divided into five types(HP-1,HP-2,HP-3,HP-4and HP-5;MP-1,MP-2,MP-3,MP-4 and MP-5).The low-pressure trough type,low pressure pressure equalizing type and weak high pressure type were the main weather types in the heavy pollution period in BTH,the percentage was?25%for each type.From the seasonal viewpoint,the low pressure type and the high pressure rear type were mainly distributed in autumn and winter,and the low pressure trough type was the main type in spring and summer.Finally,taking 2018 as the benchmark year,the optimized emission reduction scheme of industrial emissions in 2030 for the air quality of BTH reaching the standard value and for the emergency emission reduction for severe and moderate pollution in autumn,winter,spring and summer were obtained.The results showed that in order to meet the air quality standards,11 urban industrial industries except Chengde and Zhangjiakou should reduce 164000 tons PM_2.5 equivalent emission mass,accounting for 47.7%of the total emission equivalent.Tangshan,Handan,Shijiazhuang and Xingtai had larger reduction amounts,accounting for 81.5%of the total regional emission reduction.The emission reduction effect assessment indicated that the optimized emission reduction scheme would be practical.The PM_2.5 concentrations for different cities would be reduced to 32.1-38.9?g/m~3.The results of the emergency optimization emission reduction plan showed that the equivalent distribution of emission reduction in different cities in the five process schemes was 413.3 t/d-479.7t/d.The difference of emission reduction in the five pollution types was closely related to the sensitivity of urban emissions to regional air quality.Shijiazhuang,Baoding and Zhangjiakou were more prominent in the process of HP-1 pollution;the southwest transmission channel of HP-2 pollution process was higher than that of central Hebei;the proportion of urban emission reduction in the middle and northwest of BTH was relatively prominent in the process of HP-3 pollution.From the perspective of the regional air quality improvement effect of implementing optimized emergency plan,the PM_2.5 concentration in the region would be reduced by 30.7%-36.2%during the processes from HP-1 to HP-5.The implementation of the medium pollution optimization emission reduction scheme would reduce the regional PM_2.5 concentration by 16.9%-21.4%during the MP-1 to MP-5 processes.Taking the red alert in December2016 in BTH region as a study case,the results showed that the PM_2.5 concentration reduction of different cities was 25.0%-30.6%under the condition of policy emission reduction.However,under the optimized emission reduction scenario,the decrease of PM_2.5 concentration would be 32.1%-38.2%,which is significantly higher than that of the policy emission reduction scenario.