Simulation Study On The Effect Of Ozone Pollution Improvement By Emission Reduction Scenario Of Ozone Precursors In The Central Urban Area Of Baoding

In recent years,the concentration level of particulate matter has significantly decreased,but ozone pollution has become increasingly prominent in Baoding City.,A series of policy documents has issued in order to effectively prevent and control ozone pollution in Baoding City.The study aims to quantitatively evaluate the improvement effects on ozone pollution in the central urban area of Baoding City under different NOx and VOCs emission reduction schemes by conducting relevant research on the relationship between O₃concentration and precursor NOx and VOCs emissions during typical periods.Based on this,the emission reduction direction for ozone pollution prevention and control in the central urban area of Baoding is provided,as well as suitable local NOx and VOCs emission reduction plans during the 14th Five Year Plan period.and expected to be provided reference for the scientific development of NOx and VOCs control strategies in Baoding City.In this paper,we firstly use the air pollutant concentration data monitored from2017 to 2021 in Baoding City to analyze the Changes in ambient air quality and major atmospheric environmental issues.Meantime,we estimated the emissions of 9pollutants from 10 types of sources in the central urban area of Baoding City using the emission factor method,constructed a emission inventory for the central urban area of Baoding City in 2019.Secondly,The pollutant concentrations were simulated in the central urban area of Baoding in January,April,July and October 2019 by CMAQ model,and the simulated results were compared with the observed values to verify the accuracy of the emission inventory.Finally,a sensitivity test method is used to conduct scenario simulations of according to different NOx and VOCs emission reduction ratios based on the validated emission inventory in the central urban area of Baoding City,and quantitatively evaluate the improvement effect on ozone pollution in the central urban area of Baoding under different NOx and VOCs emission reduction schemes.The main conclusions obtained are as follows:（1）The the ambient air quality improved significantly from 2017 to 2021 in Baoding City,the average annual concentration level of six basic pollutants shows a downward trend,with the proportion of days with good air quality rising from 43.8%in 2017 to 68.0%in 2021,but ozone pollution has shown a significant upward trend,with the proportion of days with O₃as the primary pollutant rising from 33.8%in2017 to 40.7%in 2021.O₃has become an important factor affecting the excellent rate of ambient air quality in Baoding City.（2）The emissions of SO₂,NOx,CO,VOCs,NH₃,PM₁₀,PM_2.5,BC and OC are4235,26841,41302,10047,11371,18820,5862,436 and 536 tons in the central urban area of Baoding City in 2019.Among them,the emission of SO₂is mainly from the fixed combustion source of fossil fuels,NOx and VOCs are mainly from the mobile source,particulate matter is mainly from the dust source,and agricultural source is the main emission source of NH₃.（3）The WRF model to simulate the temperature,relative humidity,wind speed and the observation value of correlation coefficient is above 0.5,0.7 and 0.9respectively,WRF model simulation of near-surface meteorological elements effect is good.The CMAQ model to simulate the SO₂,NO₂,CO,O₃,PM₁₀,PM_2.5and the observation value of correlation coefficient is above 0.4 respectively,and the standardized fraction deviation（MFB）is within the range of-30%to 30.0%,and the standardized fraction error（MFE）is less than 50%,indicating that the emission source inventory constructed in this study is reasonable.（4）The results of 16 sensitivity tests were comprehensively analyzed.From the improvement effect of ozone concentration,when the emission of VOCs was reduced by 60%,the O₃concentration decreased most significantly.When VOCs emission is reduced by 40%,O₃concentration decreases significantly.However,when the reduction ratio of VOCs is less than or equal to 20%,the reduction of NOx can not effectively reduce the O₃concentration.A large reduction in NOx will cause the O₃concentration to rise instead of falling.From the improvement effect of ozone pollution,among the four typical sensitivity tests,test 1（10%reduction of NOx,10%reduction of VOCs）has a general improvement effect on ozone pollution,the total ozone pollution days decreased from21 to 20,and the severe and moderate pollution days did not decrease.Test 5（10%reduction of NOx,20%reduction of VOCs）has a significant improvement effect on ozone pollution,the total ozone pollution days decreased from 21 to 17,including severe and moderate pollution days decreased by 2 days.The test 9（10%reduction of NOx,40%reduction of VOCs）has a significant improvement effect on ozone pollution,the total ozone pollution days decreased from the 21 to 15 days,including severe and moderate pollution days decreased by 3 days.The test 16（60%reduction of NOx and VOCs）has a very significant improvement effect on ozone pollution,the total number of ozone pollution days is reduced from 21 to 11,and the number of severe and moderate pollution days is reduced by 4 days.In summary,when formulating emission reduction strategies for VOCs and NOx,the emission reduction of VOCs should be greater than NOx,and when the emission reduction ratio of VOCs is more than 40%,it can effectively improve the ozone pollution status in the central urban area of Baoding City.Reducing NOx and VOCs in an equal proportion can also curb the upward trend of ozone pollution when considering the difficulty and cost of actual emission reduction.Taking into account the environmental goals and requirements of the 14th Five Year Plan,as well as the socio-economic benefits,the appropriate emission reduction strategy was VOCs reduced by 20%and NOx reduced by 10%for the prevention and control of ozone pollution in the central urban area of Baoding during the 14th Five Year Plan period.