Study On Characteristics And Relationship Of Ozone And Precursor Pollution In Shenzhen Based On Sensor

With the rapid economic development and urbanization of industrial activities and motor vehicles,emissions of ozone precursors?VOC and NO_x?have rapidly increased,and ozone has surpassed particulate matter as the primary pollutant in the atmosphere.While the relationship between O₃,NO_x,and VOC is complex and non-linear,and is affected by a large number of factors,understanding the control factors of the process is essential to understanding regional photochemistry and application cost effective control strategies.In this study,three typical monitoring points have deployed in Shenzhen,and O₃,NO_x and VOC have analyzed and determined by inexpensive sensors and GC-MS.Analyze the correlation between ozone and its precursors,and analyze the ozone sensitivity based on EKMA to evaluate the ozone precursor reduction scheme.In laboratory calibration,the best correction algorithm has developed for sensor performance and quality control by characterizing the sensor's concentration response to ambient conditions?temperature and humidity?.The overall performance of the sensor after entering the calibration line is very good and can generate high quality,time resolved data.The pollution of Xili and Longhua sites was much higher than that of the university city site,in which ozone had the highest concentration in summer,NO_x has reached the maximum concentration in winter,and VOC concentration was highest in winter.The diurnal variation of ozone concentration was consistent with the characteristics of photochemical reaction.It has reached a maximum value in the afternoon and shows a distinct single peak shape.The daily variation of NO_x was characterized by bimodality.The maximum value has appeared in the morning and evening,and the peak of NO concentration appears.Earlier than the time when the peak concentration of NO₂ occurred.The factors affecting ozone production are complex,and ozone had a significant negative correlation with the trend of nitrogen oxides and VOC.In terms of VOC,alkane and aromatic hydrocarbons account for the majority,but aromatic hydrocarbons and olefins contribute to ozone pollution.Big.Among them,toluene,m-xylene and mesitylene in aromatic hydrocarbons contributed a lot,contributing a total of about49.6 % to ozone pollution.Isoprene was also extremely important in ozone production potential.The ratio of NO₂/NO was expressed as a unimodal distribution,and when the ratio is high,the ozone concentration is also high.The logarithmic relationship between ozone and its precursors has reproduced the photochemical reaction process.When theconcentration of NO_x and VOC was high,the concentration of ozone was low.As the photochemical reaction continues,NO_x and VOC were consumed by the reaction,and the ozone concentration was continuously increased.Through the ratio of the photochemical indicator,it can be preliminarily judged that the sensitive region of ozone generation is in the VOC control region.Based on the measured data and the concentration curve of ozone drawn by the classical model,the ozone concentration curve based on the measured data better reflects the photochemical reaction process.The curve drawn by the model has reflected that all three sites are in VOC.Control area.For the ozone precursor reduction scheme,the synergistic reduction of VOC and NO_x was the most effective.The VOC single reduction effect was not obvious,and because it was sensitive to VOC,the ozone concentration level may be slightly increased when NO_x was separately reduced.