Study Of The Characteristics Of Ozone Pollution And The Sensitivity To Precursors In Zhengzhou

In recent years,with the gradual improvement of fine particle matter pollution in China,the problem of ozone pollution in summer has become increasingly prominent.Studies on ozone pollution are concentrated in Pearl River Delta,Yangtze River Delta,Chengdu and Chongqing region,while in the central plain region,it mainly focuses on the identification of pollution level.Based on the on-line observation data and model analysis of typical high incidence season of ozone pollution in Zhengzhou,in this study,we identified the concentration characteristics of ozone and its precursors,the variation in different periods,and analyzed the sensitivity of ozone formation and its precursors,and distinguished the main control precursors.It hopes to provide scientific reference for Zhengzhou to formulate ozone control countermeasures in the future.First,the concentration of ozone and its precursors during May 1 to June 30,2018was analyzed by using statistical analysis method.The results showed that the average ozone concentrations of the three sites（Yanchang\ZZU\Ganglishuiku）are 55.4,54.8and 49.1 ppbv,respectively.The concentration of ozone and NO₂ in the urban station is higher than that in the suburb station,while the concentration of CO is relative lower.The hourly averaged concentration of VOCs in Yanchang site is 47.2 ppbv,and the components are alkane>alkene>aromatic>acetylene.The hourly averaged value of H₂O₂ concentration in Zhengzhou University site from May 1 to June 20 was 2.17 ppbv.Daily change analysis showed that the trend of ozone,Ox and H₂O₂ concentrations was similar.The peak value appeared at 15:00-17:00,and the daily change curve of VOCs,NOx and CO was similar,but the curve was opposite to that of ozone with the peak value at 7:00.Secondly,through the correlation analysis of ozone and its precursors and meteorological parameters,the key factors affecting the concentration of ozone are analyzed.The results showed that there was a significant positive correlation between NO₂,NO,CO and VOCs,but a significant negative correlation with ozone.The Pearson correlation coefficient was higher in daytime than in nighttime.Compared with the O₃ non-episode period,the temperature and humidity are higher and lower during the O₃ episode period,and the high concentration ozone appears in the south wind and the southeast wind direction.The high concentration of precursors,high temperature,low relative humidity,and moderately high wind speed together with the wind direction dominated by south and southeast wind contribute to urban O₃ episodes in Zhengzhou.Thirdly,two methods,propene-equivalent concentration and O₃ formation potential,were used to investigate the reactivity of VOCs.The results showed that alkenes and aromatics are the dominant components of ozone formation in Zhengzhou,while isoprene,cis-2-butene and ethylene are the species that contribute the most to ozone formation.Finally,the sensitivity analysis of ozone formation was carried out by using VOCs/NOx,SPM and OBM models.The results showed that during the observation period,the ozone formation of the three sites in Zhengzhou is mainly in the VOCs control regime and the transition regime.During the O₃ episode period,the ozone formation is likely to be in the transition control regime,while during the O₃ non-episode period,the ozone formation is more controlled by VOCs.The results of Relative Incremental Reactivity（RIR）showed that the control of alkene emission can better reduce the ozone generation rate.The analysis of local ozone chemical budget showed that the increase of ozone concentration in Yanchang site mainly comes from local photochemical generation,and the regional transmission is mainly horizontal output or vertical diffusion,but during the period of 8-10,there is also external input.