Research On The Applicability Of Ozone Sensitivity Determination Index In Jiangsu Area

With the continuous control of atmospheric pollution in recent years,the problem of particulate pollution has been solved,but ozone pollution has become more serious.In order to control ozone pollution and precisely control the emission of nitrogen oxides(NO_x,the sum of nitric oxide and nitrogen dioxide)and volatile organic compounds(VOCs),it is necessary to have an in-depth understanding of the response relationship between ozone and precursors and the sensitivity of ozone to NO_x and VOCs.Therefore,the study of different photochemical indicators to determine the sensitivity of ozone is crucial to formulating effective emission reduction control strategies.In this study,the air quality model was used to simulate the ozone pollution period in the Yangtze River Delta region from July 22 to 31,2017.This study distinguished the ozone sensitive district by calculating the average difference between the ozone concentration corresponding to the reduction of 35%VOCs(or NO_x)emission and the simulated ozone concentration under the baseline scenario between 1 pm and 4 pm.Correspond the NO_x sensitive or VOCs sensitive information obtained through the sensitivity test with the photochemical indicator value of the grid,the critical value and range of the photochemical indicators was obtained by counting the photochemical indicator value of the study area in the fifth and ninety-fifth percentile of the sensitive regime of ozone.The photochemical indicators H₂O₂ and HNO₃ generation rate ratio(P_H2O2/P_HNO3),formaldehyde and nitrogen dioxide ratio(HCHO/NO₂),formaldehyde and total reactive nitrogen(HCHO/NO_y)and total reactive nitrogen(NO_y)were used to study the relationship between the sensitivity of ozone and photochemical indicators.The results show that:(1)The critical values of the photochemical indicators in Jiangsu Province were:P_H2O2/P_HNO3(0.55,0.75),HCHO/NO₂(0.81,1.35),HCHO/NO_y(0.38,0.60),NO_y(8.18,17.63).There is a certain difference with other studies,which shows that the critical value of photochemical indicator needs to be adapted to local conditions.(2)Based on the photochemical indicator values simulated in this study,most area of Jiangsu Province was in the NO_x sensitive regime,and only some urban centers were in the VOCs sensitive regime.(3)According to the EKMA curve,the sensitive regime classification based on the indicators HCHO/NO₂ and HCHO/NO_y was more consistent with the EKMA curve.P_H2O2/P_HNO3 may highly estimate the sensitivity of ozone to VOCs.NO_y may underestimate the sensitivity of ozone generation to VOCs,and highly estimate the sensitivity of ozone to NO_x.Recommend to use photochemical indicator HCHO/NO₂ and HCHO/NO_y.(4)When a stricter criterion was adopted,the indicator value range in the transition regime becomes larger,and the sensitivity to single precursors decreased.The photochemical indicator critical value obtained by the first and second order sensitivity coefficients of the decoupling direct method tended to divide more regions as NO_x sensitive regime.When the ozone concentration was high,ozone is more sensitive to VOCs and NO_x.