Study On Air Pollutant Emissions Changes From Open Biomass Burning And The Impact On Regional Haze Pollution In Northeast China

Various gaseous pollutants and particulate matters emissions from open burning of biomass?including straw burning,grassland fires,forest fires?are one of the important sources of atmospheric pollutants.Northeast China is a central region with high forest and grass coverages as well as an intensive agricultural area in China.A large amount of straw remained and burned in the field directly.FINN?Fire Inventory from NCAR?fire datasets were used to analyze the temporal and spatial variations of particulate matters emissions from fires in Northeast China in 2002-2016 and the meteorological factors affecting emissions from open biomass burning.We introduced the FINN dataset into WRF-Chem model to simulate a large-scale and extremely heavy pollution process in Northeast China in November 2015.The main conclusions are as follows:?1?Temporal and spatial variations of particulate matter emissions from open biomass burning in Northeast China1)The annual emissions of PM_2.5,PM₁₀,OC and BC from open biomass burning in2002-2016 are 2.7984¹2.23 million tons,3.3658¹4.48 million tons,1.5015⁶5.03 million tons and 0.2099⁰.8573 million tons,respectively.The annual emissions are 59.015 million tons,70.89 million tons,314.9 million tons and 0.4337 million tons.2)Emissions from open biomass burning have obvious seasonal dependence,with the largest emissions in spring,followed by autumn and winter.The bimodal character is present throughout the year,with emissions peak months is April and October.3)High-value areas of emissions from open biomass burning are mainly concentrated in the Daxing and Xiaoxing'anling areas and the Sanjiang Plain area in the eastern part of Heilongjiang Province.The high-value areas are more characterized by natural emissions?forest fires,grassland fires?.In addition,a large value zone of particulate matter emissions from the arable land agricultural area in the Northeast Plain is a northeast-southwest trend,mainly related to human activities?straw burning?.4)From 2002 to 2016,the domain areas of emissions from fires have been transferred from forest land to cultivated land,and more will be discharged by man-made burning activities such as straw burning.5)Meteorological factors such as high temperature,drought,and strong wind will increase the emissions from open biomass burning.?2?The impact of multi-scale meteorological on a heavy pollution over Northeast China in November 20151)From the weather situation,in the development stage of the heavy pollution process,the high-level zonal circulation is prevalent,and the overall weather situation is stable.As the surface cold high pressure moves eastward and weakened,the surface pressure gradient is small,and the northeast China is located between the Mongolian high pressure and the Japan Sea high pressure.In the low pressure equalization field between the high pressures,the surface Inverted trough develops,and the northeast China is located in front of the 500hpa trough and controlled by the southwest warm and humid air flow.With the reconstruction of the East Asian trough and the cold high pressure southward,northwesterly wind brought dry and cold airflow,and the concentration of PM is reduced.2)The strong temperature inversion layer structure in the vertical direction of the boundary layer during pollution period,the atmosphere is stable,the ground is high humidity,small wind or static wind,which is not conducive to the dilution and diffusion of pollutants,accumulated in the boundary layer.?3?Contribution of straw burning emissions to the heavy pollution process and regional PM_2.5.5 transport in Northeast China1)The contribution of straw burning emissions to Harbin,Changchun and Shenyang is reach up to 45%,and especially the contribution of straw burning is up to 10%-40%during the peak concentration period of PM_2.5.The areas with large contribution of straw burning are mainly located in the surrounding areas of cities and agricultural areas.The contribution to the surrounding areas of the Harbin-Changchun-Shenyang urban belt can reach 10%-60%.The contribution to the Sanjiang Plain in the eastern Heilongjiang Province and the Songnen Plain in the western Heilongjiang Province and Jilin Province is even more than 80%.2)The vertical structure of PM_2.5.5 is obviously affected by the temperature inversion layer.When there is an inversion layer,the PM_2.5.5 began to accumulate at a relatively low level under the inversion layer and difficult to spread upwards.Under the atmospheric dilution and diffusion capacity,PM_2.5.5 emitted from fires,extended to a height of more than 1 km with the plume of burning.The emissions from open biomass burning in Heilongjiang Province are mainly transported at a height of about 1km with a large transmission flux.The trans-provincial transmission flux from Jilin Province to Heilongjiang Province is relatively small and transmitted at a lower altitude.