The Pollution Features Of Ozone And Sensitivity Analysis Of Precursors In Jinan City

Near ground ozone（O₃）is a typical two pollutant in the atmosphere which is produced by a series of complex photochemical reactions of volatile organic compounds（VOCs）and nitrogen oxides（NOx）,and has potential hazards to the atmospheric environment and human health.To study the pollution characteristics of urban ozone（O₃）and its precursors（VOCs,NOx）,determine the control ratio through sensitivity analysis,identify the key VOCs species which affecting the ozone pollution level and analyzing their sources are the scientific basis for formulating the control countermeasures of ozone pollution.This paper analyses the pollution characteristics（including spatial and temporal distribution characteristics and concentration levels）of the surface ozone and its precursors which is based on the online monitoring data of ozone and its precursors for more than 6 years in Jinan city.From a long term trend,the concentration level of O₃showed an upward trend in general.The concentration level of Ox was slow down which might be related to the control of the emission,but the overall concentration level was high,indicating that the atmosphere was more oxidizing in the region.The seasonal and monthly variations of O₃ and Ox are characterized by higher in spring and summer season,lower in autumn and winter season,the high values occurred in June.The diurnal variation of O₃ and Ox in different seasons is a single peak distribution,which is influenced by the radiation intensity and temperature of the sun,and the peak value is around 14:00¹5:00 in the afternoon.The spatial distribution characteristics of O₃ in Jinan city are higher in the north,lower in the South and higher in the suburb,and lower in urban area.Choosing the Quancheng Square super station as research area,we can obtain the concentration data and temporal and spatial distribution characteristics of ozone（O₃）and precursors（VOCs,NOx）by continuous on-line observation.From the concentration level and composition characteristics,the most abundant species are alkanes,followed by aromatics,alkenes and alkynes.The concentration contribution rate is alkanes>alkenes>aromatics>alkynes.From the time change,the long-term trend of the VOCs change is decreasing slowly.The seasonal variation is higher in winter and lower in summer.The annual concentration range is from 67.79 ppbv to129.87 ppbv.The diurnal variation is distributed in the Shuangfeng type.Higher reactive activity of VOCs are that of alkenes and aromatics,ozone generation potential（OFP）is also larger.The long-term change trend of nitrogen oxides overall showed a slow rising trend.The seasonal and monthly characteristics of nitrogen oxides are higher in autumn and winter in the heating season,which are lower in spring and summer season.The diurnal variation of NOx,NO and NO₂ was distributed in Shuangfeng type,and the peak time coincided with the peak of traffic morning and evening,and negatively correlated with O₃ daily variation curve.The mean concentration of near surface ozone and its precursors in summer in Jinan city are selected as the research basis.Through the sensitivity analysis of the VOCs/NOx ratio method and the EKMA curve,the formation of the near ground ozone（O₃）is controlled by VOCs and NOx,and VOCs is dominant in Jinan city.From the daily variation curves of ozone and its precursors,we can ensure that O₃ has a good negative correlation with VOCs and NOx.The key species of VOCs were identified by L_OH and OFP,and their sourc-es were explored by principal component analysis.Research shows that the VO-Cs species with higher atmospheric activity in Jinan city are aromatics and alk-enes,which have the greatest contribution to the formation potential of ozone（OFP）,among which the most highly active species are aromatics.The key spe-cies of VOCs in Jinan city are C₂^C₆ alkanes Ethane,2,2,4-Trimethylpentane,C-yclohexane),Ethylene,Isoprene,1,3-Butadiene,cis-2-Butene,Benzene,Toluene,1,2-Trimethylbenzene,m/p-Ethylbenzene,Ethylbenzene and Styrene.The main so-urces of VOCs in the ambient air of Jinan city are traffic source（vehicle exha-ust,gasoline volatilization）,the source of solvent use,the source of industry an-d the combustion source of fossil fuel,among which the vehicle exhaust and t-he solvent are the main source.