Characteristics Of Ozone Pollution And Its Correlation With Precursor Pollutants In Wuhan City From 2016 To 2017

Ozone?O₃?is a kind of trace active oxidant gas that is ubiquitous in the atmosphere.The small amount of O₃ in the troposphere is naturally formed,and most of them are caused by complex photochemical reactions of primary pollutants such as nitrogen oxides and volatile organic compounds.In recent years,the problem of O₃ pollution has increasingly become the focus of attention.In order to explore the changing characteristics of O₃ in Wuhan and the influence of precursor pollutants on it,this study conducted continuous monitoring of O₃ and precursor data and meteorological data in the ambient atmosphere of Wuhan City at the monitoring station of the School of Resources and Environmental Sciences of Wuhan University.Online observations were monitored from September 2016 to August 2017.The results show that:the average concentration of ozone in Wuhan urban area is 70.1ppbv during the whole observation period,the non-standard rate was 8.7%.There was 92 days of O₃which is the primary pollutant in the whole year.There was five-month's O₃ concentration exced the standard level during the observation period,mainly concentrated in the spring and summer from May to August.The daily variation of O₃ concentration showed a unimodal type.The minimum and maximum values appeared around 8:00 and 16:00,respectively.The O₃concentration decreased slowly at night and rose rapidly in the afternoon.The average concentration of O₃ in each season from high to low was spring,summer,autumn and winter.The concentration accumulation of O₃ in spring is the fastest,while the winter is the slowest.The frequency of different concentrations in different seasons showed a unimodal change in summer,and a continuous attenuation pattern in other seasons.Most of the O₃ concentration was below 40 ppbv.The variation distribution of VOCs and NO_x was bimodal,and they were similar.The average concentration of NO_x during the whole observation period was 33.3ppbv,and of VOCs was 34.3ppbv.The annual change trend was similar,the concentration in autumn and winter was higher,in spring and summer was lower.Among the VOCs concentration composition,the highest concentration of componds was alkanes?42.3%?.The VOCs source analysis results identified 8 sources,of which the highest contribution was vehicle exhaust?24.4%?.The PSCF analysis showed that local emissions were the main source of Wuhan VOCs,the impact of long-distance transportation was small.O₃ has a significant positive correlation with temperature,has a certain negative correlation with humidity,wind speed and air pressure.The dominant wind of non-standard sample was from southerly.Atmospheric monitoring stations were affected by regional pollution much more than the day time.The results of ratio calculation and model simulation show that the change of O₃ concentration in Wuhan is controlled by VOCs;the most important species contributing to the O₃ formation potential of all VOCs in the ambient atmosphere were ethene,m/p-xylene,toluene,propylene,propane,etc.Combing with the analysis results of VOCs source,Wuhan O₃ pollution control work should focus on the control of vehicle exhaust,LPG usage,industrial sources and the use of painting solvent usage.