Evaluation Of The Impact Of Straw Burning Management And Emission Reduction Policies On Regional Air Pollution In Northeast China Based On WRF-CMAQ

The open burning of crop straws can release atmospheric pollutants including carbon monoxide（CO）,sulfur dioxide（SO₂）,nitrogen oxides（NO_X）and fine particulate matter PM_2.5（particulate matter with diameter less than 2.5μm）.It is an significant factor in reducing regional air quality.Northeast China is a main grain production region and has the largest amount of straw yield in China.At the same time,the Northeast region is also one of the areas where the open field crop residue burning occurs frequently,which caused regional haze in recent years.Various air pollution phenomena frequently occur here,and the air quality here is seriously affected.In order to solve the problem of crop straw open burning and improve the air quality in the region,the three provinces of Heilongjiang,Jilin and Liaoning in Northeast China have carried out straw burning ban management and control actions,and promulgated a series of straw burning ban policies.To evaluate the effects on burning ban policies on improvement of air quality.In this paper,the straw burning ban policies implemented by the country and the three northeastern provinces in recent years were summarized.The seasonal and yearly variate of PM_2.5 and other pollutants from open field crop residue burning during 2013-2020 were analyzed.Then the relationship between quantitatively analyzes the change law of straw open burning emissions and fire points were developed.Furthermore,the evaluation of different burning ban policies on regional air quality were conducted by air quality model WRF（The Weather Research and Forecasting Model）-CMAQ（Community Multiscale Air Quality Model）.The conclusions of this study are as follows:At present,relevant national departments and local governments in China have issued a series of straw burning ban management and control policies,which effectively control the occurrence of open burning of straw.At the national level,there are 12 laws and more than 40 related policy documents related to straw burning ban in China.A framework system for the management of straw burning ban has been established through these documents,which provides a reference for local governments to formulate relevant regulations.The series of laws and policy marks that China has entered the stage of a comprehensive ban on burning crop straw.In the three northeastern provinces,each provincial government has also established a responsibility system for the management of straw burning bans.There is a significant negative correlation between the intensity of burning ban and the number of fire points in Northeast China during 2013-2020 period.From 2013 to 2020,the total emissions of open straw burning in Northeast China showed an overall trend of increasing first and then decreasing based on the localized straw burning emission inventory.Firstly,the total emissions of main air pollutants from straw burning reached a peak（106,594.12Gg）in 2015,and they decreased significantly and maintained a stable trend after 2017.The trend of annual emissions illustrated that the straw burning ban policy showed a good governance effect in Jilin Province in 2019.Secondly,the monthly variation of air pollutant emissions from straw burning showed that before spring plowing（March and April）and after autumn harvest（October and November）were the concentrated burning periods.Furthermore,the emission in spring was greater than that in autumn after 2015 because of more intensity of burning ban policy after 2015.The simulation scenarios of burning ban showed that the management and control of crop straw open burning in Northeast China can effectively reduce the impact of open straw burning on air pollution.The burning ban policy is conducive to improving the air quality in Northeast China.In the basic scenario,the contribution ratios of CO and PM_2.5 concentrations from crop straw open burning to the atmospheric environment were 24.01%and 39.98%in Northeast China.Therefore,the open burning of crop straws has a negative effect on air quality in Northeast China.Under the emission reduction scenario,the contribution ratios of CO and PM_2.5 concentrations from crop straw open burning to the atmospheric environment decreased by 9.58%and 13.95%,compared with 2017.Meantime,the concentrations of CO and PM_2.5 in Northeast China reduced by 0.02 mg/m³ and 41.43μg/m³.The results indicating that the straw burning ban policy in 2019 improved the air quality in Northeast China.In the future scenario,three provinces in Northeast China were all conducted the burning ban policy in Jilin Province in 2019.The simulation results showed that the contribution ratios of crop straw open burning to CO and PM_2.5 in Northeast China dropped to 3.71%and4.55%.The average atmospheric concentrations of CO and PM_2.5 in the three provinces in Northeast China were decreased by 9.72%and 16.97%.Hence,if all three provinces in Northeast China were implements the Jilin Province’s straw burning ban policy in2019,it could further improve the regional air quality.