Study On Characteristics Of Atmospheric VOC Pollution And Its Contribution To Ozone Formation In Jinan

Volatile organic compounds?VOCs?,a type of compounds that are widespread in the near-surface atmosphere.Such compounds are not only directly harmful to human health,but also reacts with nitrogen oxide(NO_X)under photocatalysis to generate typical secondary pollutant ozone?O₃?,which is harmful to the city's atmospheric environment.This paper takes VOCs and O₃ in Jinan as the research objects,the pollution characteristics and levels of VOCs and O₃ in urban areas were studied based on the online monitoring data for one consecutive year.The key VOCs species that affect the generation of O₃ and their mutual transformation were identified and the source of VOCs in Jinan was explored,in order to provide a scientific basis for improving the air quality of Jinan.?1?.In this study,through on-line GC-MS/FID monitoring system,56 VOCs in Jinan atmosphere were monitored,and a set of special quality control and quality assurance methods were formulated and implemented to ensure the accuracy of data.According to the analysis of monitoring data,the average daily VOCs concentration in Jinan ranged from 12.03ppb to 92.69ppb,with an average total concentration of 30.35ppb.In terms of time variation,the average seasonal concentration distribution of VOCs in Jinan was as follows:Winter>Autumn>Spring>Summer.The highest value of the hourly average concentration occurs every day from 7 am to 9 am,and the lowest value of each day occurs from 3 pm to 4 pm.The results have shown that the VOCs has a positive correlation with particulate matter(PM_2.5 and PM₁₀),carbon monoxide?CO?and nitrogen oxide?NO_X?,while showed a significant negative correlation with O₃.?2?.Using special species ratio method to analyze the source of VOCs in Jinan.Through the comparative study of different species?alkanes,olefins and aromatics?,species with similar atmospheric life and species with different atmospheric life,it is found that automobile exhaust is the main source of VOCs in Jinan.The combustion and emission of petrochemical industry also have an important effect on the concentration of VOCs in ambient air in Jinan.At the same time,the transfer of regional background atmosphere also has a certain influence on the concentration of VOCs in ambient air.Combined with the pollution characteristics of VOCs in the ambient air of Jinan,it is considered that the main control direction of VOCs Pollution in Jinan should be to control the emission of vehicle exhaust,and to increase the emission limit of petrochemical enterprises and cut back on coal use.?3?.The O₃ pollution in Jinan is at a high level in China and remains on an upward trend as a whole.O₃ concentration shows the seasonal distribution characteristics of high in summer and low in winter in terms of time distribution,and has obvious monthly changes.The overall change last month showed an inverted"V"shape.The daily peak appears after noon,and the concentration of O₃ in suburb is higher than that in urban area and background area.Based on the data from other stations in Jinan,it is found that O₃ is positively correlated with temperature and solar radiation,and negatively correlated with humidity and wind speed.The sensitivity analysis results of ratio method and EKMA curve method both show that O₃ generation in Jinan belongs to"VOCs control area".Based on this,every species is analyzed according to L_OH contribution rate and O₃generation potential?OFP?.The results indicate that olefin species are important species for controlling O₃ production in Jinan.It is determined that 1-butene,isoprene,m-xylene,propylene,cis-2-butene,isopentane and ethylene as the active species,played an important role in the generation of O₃ in VOCs in Jinan.According to the source analysis of VOCs,automobile exhaust and petrochemical industry are two pollution sources that have obvious promotion effect on ozone generation.The main control direction of controlling O₃ pollution in Jinan should start from controlling the exhaust emission of motor vehicle and reducing the emission of petrochemical pollution sources.