Formation Mechanism And Improvement Path Of Ozone Pollution In Anhui Province

In order to explore the temporal and spatial distribution of Ozone concentration,influencing factors and the contribution of precursors volatile organic compounds（VOCs）to the generation of Ozone in Anhui Province,we analysis the temporal and spatial distribution of pollutants based on the data from 70 environmental monitoring stations in various cities in Anhui Province from 2016 to 2018,and the influencing factors of changes in Ozone concentration combined with meteorological factors（temperature,wind speed,relative humidity,atmospheric pressure,precipitation）and precursors（nitrogen dioxide,carbon monoxide,VOCs,PM2.5）.A comprehensive analysis method was used to analyze the observation data in detail,and the main results are as follows:（1）The spatial and temporal distribution of Ozone concentration in Anhui Province from 2016 to 2018 was analyzed by statistical analysis method.The results showed that the number of days with Ozone as the primary pollutant increased year by year,and the days dominated by PM_2.5decreased year by year.Therefore,the type of air pollution in Anhui Province is gradually changing from single particulate dominated to particulate and Ozone both dominated called aerosol composite photochemical pollution.From 2016 to 2018,the Ozone pollution showed an overall upward trend,and the high Ozone concentration areas were mainly concentrated in northern and central Anhui.Season:the Ozone concentration in Anhui Province is high in spring and summer while low in autumn and winter.Month:the monthly variation of Ozone concentration in Anhui Province mainly showed two changes:"M"double peak and"∧"single peak,and the month with the highest concentration is greatly affected by the temperature and rainfall of that year.Day:There is an anti-"weekend effect"phenomenon in Anhui Province where the Ozone concentration on working days is slightly higher than that of holidays.Hourly:the hourly variation of Ozone concentration showed a"single peak"type with concentration gradually decreased from 0:00 to 7:00,the lowest value appeared at about 7:00,and then gradually increased.The Ozone concentration maintained a relatively high level between 12:00 and 18:00,and the highest value generally appeared at about 15:00,which was the same as most cities in China.However,the characteristic of hourly variation of NO₂concentration was"bimodal",reaching the lowest value at about13:00 and peaking at 6:00 and 20:00,respectively.（2）The effects of concentration changes of nitrogen dioxide,carbon monoxide and PM2.5 on Ozone were negatively correlated.The results show that there is a nonlinear relationship between Ozone and air temperature,relative humidity,air pressure,precipitation and wind speed based on the Generalized additive model（GAM）.The R²of multi-factor GAM model is 0.653 and the variance interpretation rate is 65.7%,which mean the modelling effect is good.From the year-round scale,the influence of relative humidity and temperature on Ozone concentration is more significant than other meteorological factors,the meteorological conditions where the temperature is greater than 26°C,the temperature difference is greater than 8°C,and the relative humidity is less than 60%are good conditions for the Ozone concentration to easily exceed the standard.,and the exceeding rate of Ozone is as high as 55.71%.107 kinds of substances in ambient air were detected by the Ex PEC 2000 online monitoring system of volatile organic compounds,including 27 kinds of alkanes,11kinds of alkenes and alkynes,17 kinds of aromatic hydrocarbons,30 kinds of halogenated hydrocarbons,21 kinds of OVOCs and 1 kind of other substances.The average concentration of TVOCs during the observation period is 118.47μg/m³,of which the minimum is 12.83μg/m³and the maximum is 722.66μg/m³.The diurnal variation of VOCs in the observation area showed a typical"double peak"feature,and the concentration of VOCs in the weekend was higher than that in the working day.（3）The photochemical sensitivity of the observation area was discussed based on the observation data,the ratio of VOCs/NOx in the observation area was less than4/1,and the sensitivity of Ozone generation was preliminarily identified as VOCs-controlling area.Based on the Ozone generation efficiency（OFP）calculated from the observed data,the average estimated OFP of Ozone photochemical sensitivity is229.40μg/m³.The proportion of OVOCs was 29.20%,olefins and alkynes were27.34%,aromatics were 24.49%,alkanes were 17.43%,halogenated hydrocarbons were 1.48%,and others were 0.06%.The top ten factors contributing the most were ethylene,M/p-xylene,propanal,acetaldehyde,propylene,toluene,isopentane,acrolein,cis-2-butene and 1-pentene.The results of PMF model source analysis show that VOCs in the atmosphere of the observation area mainly come from the emission process of gasoline vehicles,which accounting for 40%;the emission sources of diesel vehicles and materials products account for 20%and 19%respectively;the chemical solvent sources and LPG volatiles contribute the least,accounting for 11%and 10%respectively.（4）The corresponding emission reduction measures and suggestions are put forward from the key emission reduction industries of NOx and VOCs and ozone collaborative control.