Spatiotemporal Changes Of Air Pollutants And Health Risks During Crop Residue Burning Seasons In China’s Main Agricultural Production Areas

Crop residue burning releases a variety of gaseous pollutants and particles,which seriously affects the ecological environment and human health.Although some studies used coefficient method and statistical data to calculate the emission inventory of various major pollutants from crop residue burning in China,and some studies also focused on the change of particulate matter in crop residue burning season,few studies concerned changes and associated health risks of all major air pollutants,including aerodynamic diameters less than 10 um(PM₁₀)and 2.5 um(PM_2.5),sulfur dioxide（SO₂）,nitrogen dioxide（NO₂）,ozone（O₃）and carbon monoxide（CO）,during the open field crop residue burning seasons.Based on the remote sensing data with spatial resolution of 1 km,our study detected the daily crop residue burning spots from 2015 to 2016 in China.Based on the daily concentrations of PM_2.5,PM₁₀,CO,SO₂,NO₂and 8 h-average O₃provided by China National Environmental Monitoring Center’s air quality monitoring station,the average concentrations of six kinds of air pollutants in each day and month were calculated on the provincial scale.We analyzed the temporal variation of these air pollutants.And the crop residue burning spots and the concentrations were analyzed to select the abnormal month of pollution at provincial level.Then,the spatial contributions of crop residue burning spots on air pollutants at monitoring sites level have been analyzed,along with changes of associated health risks.The results indicated that:（1）Based on the results of statistical analysis,the crop residue burning spots in2016 decreased significantly compared with that in 2015,by about 28%.From 2015to 2016,more than 50%of the crop residue burning spots in China were distributed in Heilongjiang,Liaoning and Jilin provinces.In Northwest China,the total number of crop residue burning spots were less than 5%of the whole country,and in southern China,the number was less than 10%.（2）The results of monthly variation analysis of air pollutants show that the concentrations of PM_2.5,PM₁₀,SO₂,CO and NO₂showed the change of high in winter and low in summer,while the concentration of O₃showed the opposite trend,which was higher in summer and lower in winter.In the crop residue burning seasons,compared with the other five kinds of air pollutants,the anomaly of PM particles is the most significant.In the areas with serious crop residue burning,such as northeast China,it was easier to detect anomalies.（3）The results of comparative analysis of air pollutants in the same period show that in periods with intensive crop residue burning,provinces trended to suffer with higher mean air pollutants concentrations,larger maximum and outliers.（4）The spatial contributions suggested that provinces of Heilongjiang,Jilin,and Liaoning experienced a regional increase of concentrations for almost all major air pollutants in crop residue burning seasons;while in other provinces with less and spread crop residue burning,the increase of air pollutants concentrations trended to be merely close to or on crop residue burning spots.（5）Finally,associated health risks of PM pollutants were increased during the crop residue burning seasons when comparing to the periods without crop residue burning in Heilongjiang,Jilin,Liaoning and Inner Mongolia,but the health risks of other pollutants did not increase significantly.This may be due to the fact that the increase will not affect human health,although crop residue burning can increase most of the air pollutants.Therefore,the intensity and spatial distribution of crop residue burning can be properly controlled in crop residue burning season,which can be used as an important vehicle to reduce serious air pollution and related health risks.