Research On Coordinated Control Of PM_2.5 And Ozone Pollution In Chemical Industry Park

With the rapid development of China’s economy,all industries have entered the"fast lane"of vigorous development.In order to obtain the regional economic advantage of industrial agglomeration,a large number of chemical industrial parks have been built all over the country.However,with the industrial agglomeration and the continuous expansion of the scale of chemical industry parks,the environmental problems brought by them are increasingly prominent.The air pollutants produced in the chemical industry park are characterized by a wide range of pollutants,large emissions and wide impact range.After some oxidizing gas pollutants are discharged into the air,a series of complex photochemical reactions will occur under light conditions,forming secondary pollution,which will have a serious impact on the regional environment.Therefore,it is urgent to carry out research on the mechanism and influencing factors of regional air compound pollution,analyze the temporal and spatial distribution characteristics of conventional air pollutants,explore the relationship between PM_2.5,secondary organic aerosols（SOA）and volatile organic compounds（VOCs）,and propose relevant countermeasures for the coordinated control of PM_2.5and ozone in the chemical industry park,so as to provide theoretical support for the prevention and control of air pollution.Based on the analysis of relevant literature and data at home and abroad,this paper constructs a regional air quality model based on CALPUFF to simulate the transmission and diffusion of air pollutants SO₂,NO₂and PM_2.5by analyzing the regional environmental quality,understanding the topographic and geomorphic characteristics of the chemical industry park,and analyzing the time series change characteristics of regional monitoring factors;The VOCs emission inventory of the chemical industry park was constructed,the contribution value of VOCs to the generation of secondary organic aerosols was estimated,and the contribution value of SOA to the generation of PM_2.5was estimated.The contribution values of different VOCs species to ozone generation in the chemical park were calculated by using the equivalent propylene concentration method and MIR method.The correlation between ozone,PM_2.5,other pollutants and meteorological factors in different seasons is analyzed,and the following conclusions are finally drawn:（1）The average ozone concentration in summer is the highest（144.8μg/m³）,which is the high incidence season of ozone pollution exceeding the standard.Spring is the high season for PM_2.5pollution exceeding the standard.The contribution of SOA to PM_2.5generation varies with seasons,with the largest contribution in spring（15%）and the smallest in summer（7%）.According to the VOCs/NO_xratio method,the sensitive areas of ozone generation in the chemical industry park are divided.The analysis shows that the chemical industry park is in the VOCs sensitive area,and the ozone generation is mainly controlled by VOCs.（2）Aromatic hydrocarbon compounds in VOCs contribute the most to the generation of SOA,with the contribution rate exceeding 90%.Among them,the three aromatic hydrocarbons with higher contribution rates are m-p-xylene（28.56%）,1,3,5-trimethylbenzene（26.76%）and toluene（20.54%）.The VOCs with higher contribution value to ozone generation are olefins and aromatic hydrocarbons,which are propylene,ethylene,cis-2-butene,acetylene,n-butene,m-p-xylene,trans-2-pentene,toluene,isobutane,1-pentene,isoprene and trans-2-butene,respectively.（3）Through the correlation analysis of PM_2.5,ozone and other conventional air pollutants,meteorological factors,the results show that the correlation between PM_2.5and ozone is most significant in spring and summer（spring correlation coefficient 0.639,summer correlation coefficient 0.689）;PM_2.5and ozone have strong correlation with SO₂and NO_x;PM_2.5and ozone are most closely related to air temperature and humidity.（4）The key to the coordinated control of PM_2.5and ozone is to control the emission of ozone precursors VOCs.The source control can be achieved by means of raw and auxiliary materials substitution,the process control can be achieved by strengthening the monitoring of VOCs,and the overall control can be achieved by delimiting ozone generation sensitive areas.