Estimation Of Carbon Emissions From Straw Burned Openly Based On Medium Resolution Remote Sensing Data

In order to obtain the carbon emissions from straw burned in a comprehensive,accurate and efficient manner,the carbon emissions from straw burned openly are estimated in Hohhot region based on medium-resolution remote sensing data.The high temperature anomaly data monitored by the Landsat OLI satellite were used to extract the open burning points of straw in Hohhot from 2014 to 2020,and the number and distribution of open burning points of straw in Hohhot in 7 years were obtained.Based on Sentinel-2 remote sensing data in 2020,the normalized combustion index（NBR）and combustion area index（BAI）of the main months of the study area were calculated.The improved combustion index(NBR_SWIR11,BAI_{Red Edge5},BAI_{Red Edge6},BAI_{Red Edge7})was proposed to select the optimal combustion index and threshold.The open burning area of straw in the spring（March and April）and autumn（October and November）in Hohhot region was extracted based on the optimal combustion index.The carbon emissions of open burning area of straw in Hohhot region were estimated in combination with the crop yield,straw-to-grain ratio and emission factor of carbon pollutants in Hohhot in 2019 and 2020.The main results are as follows.（1）From 2014 to 2020,the straw fire points in Hohhot were mainly concentrated in Tumut Left Banner,Tokto County,Helinger County and the southern urban areas.Spring（March and April）and autumn（October and November）are the main months for open burning of straw.The number of fire points showed a downward trend overall（from 543 in 2014 to 58 in2020）.（2）The optimal combustion index for fire sites extracted in March,October and November was BAI,with the thresholds of 78,120 and 110,respectively,and the overall classification accuracy and kappa coefficients were 0.91,0.878,0.96 and 0.82,0.756 and 0.9,respectively.The optimal combustion index and threshold for fire sites extracted in April were BAI_{Red Edge5} and 78,respectively,and the overall classification accuracy and kappa coefficient were 0.95 and 0.9,respectively.（3）In the spring of 2020,the area of straw burning was 12×10~4 hm~2 and the amount of straw burning was 85.7×10~4 t.In autumn,the area of straw burning is 4×10~4 hm~2,and the amount of straw burning is 29.1×10~4 t.In 2020,the total amount of straw burning in Hohhot was 114.8×10~4 t,and CH₄,CO,CO₂ and carbon emissions were 2510 t,11.7×10~4 t,159.6×10~4 t and 48.7×10~4t,respectively.（4）The estimation of carbon emission from straw burned in open-air based on medium-resolution remote sensing data can not only quantitatively reflect the carbon emission status,but also obtain the spatial and temporal distribution of regional straw burning,which can provide reference for the formulation of straw comprehensive utilization measures.