Study On The Flue Gas Emission Factors And Chemical Composition Of The Main Arboreal Species In The Greater Xing’an Mountains

As a common natural disaster,forest fires cover an area of 3.36-3.5MHA every year,releasing 2078-2460 carbon pollutants into the air TG,equivalent to 1/3 of the total amount of global fossil fuel combustion and industrial emissions,forest fires convert a large number of biomass from carbon sinks to carbon sources,while releasing a large number of flue gas particles,which is an important source of greenhouse gas emissions and the formation of atmospheric aerosols,and the particles contain a large number of elements such as carbon,organic carbon,water-soluble ions and heavy metal elements,etc.,which are important for the atmospheric environment and Serious harm to human health.At present,the research on the emission pollution of forest fire smoke particles mainly focuses on the estimation of emissions and the harm of smoke particles.The research on PM_2.5and its components from biomass combustion mostly focuses on the fields of crop straw combustion and urban environmental pollution sources.There are few reports on the systematic study of the emission factors and chemical components of smoke particles released by forest fire combustion.In view of this,five main trees（Larix gmelinii,Pinus sylvestris,Betula platyphylla,Quercus Mongolia and Populus ASPEN）were selected in this study Davidiana’s branch,leaf and bark were used as the research object.The emission factors of flue gas(CO,CO₂,Cx Hy,PM_2.5,NMHCs)were quantitatively studied when the branches and bark of different tree species were burned by the self-designed indoor biomass combustion flue gas analysis device.At the same time,the carbon components,water-soluble ions,organics and their contents of PM_2.5were compared and analyzed,which can reveal different arbors comprehensively The smoke emission characteristics and chemical composition of wood bark in the process of combustion provide an important scientific basis for estimating the emission of pollutants from forest fires and evaluating the impact on the ecological environment.The main conclusions are as follows:（1）The ignition point of various tree species in various organs ranges from 236.02℃to 291.43℃,among which the larch leaf has the lowest ignition point and the Mongolian oak branch has the highest ignition point.The crude fat content among organs of different tree species varies significantly,and the specific distribution range is From1.68%to 13.71%,birch bark has the highest crude fat content,which is3.4 times that of birch leaves,and 8.16 times that of Mongolian oak branches.The overall crude fat content is the highest,while Mongolian oak is the lowest,only 1/3;The range of calorific value of combustion and release of various organs of different tree species is 17234J·g^-1～31893 J·g^-1,and the calorific value of calorific value of each organ of other tree species except birch bark is not much different,and the distribution range is 17234 J·g^-1～20242 J·g^-1.The caloric value of birch bark combustion is 1.68 times that of birch leaves and 1.85 times that of poplar leaves.The difference in ash content between different organs of the same tree species is the largest.The leaf content is 5.02 times that of bark.The highest ash content in combustion was 8.15%,and the lowest ash content in Pinus sylvestris var.Mongolica was 1.93%,which was only 24%of the ash content in Poplar.（2）There are significant differences between the polluting gases（CO,CO₂,NOx,Cx Hy,NMHCs）and particulate matter(PM_2.5)released by different organs of various tree species.The CO₂,PM_2.5,OC and EC released by the coniferous species are higher than those of the broad-leaved species.The emission factors of atmospheric pollutants（CO,CO₂,NOx,Cx Hy,NMHCs）and particulate matter(PM_2.5)released from bark combustion are higher than those of branches and leaves.（3）The emission factors of water-soluble elements in PM_2.5released by combustion of different tree species are significantly different.Among them,the water-soluble element emission factors of larch,scots pine,and birch are significantly higher than the emission factors of Quercus mongolica and Poplar;K⁺,Ca²⁺and Cl^-were significantly higher than those of other ions in water-soluble ion emission factors in different organs of the other four tree species,and the SO₄^2-,NO₃^-,and NO₂^-emission factors were all the lowest.Ca²⁺.The emission factors between different organs of the same tree species are also significantly different.The emission factors for the three ions of K⁺,Ca²⁺and Cl^-burned by larch,and the bark emission factors are 5.56 times,6.55 times,and 3.84 times the branches,respectively.The emission factor of pine is similar to that of larch,both of which show that the bark is larger than the branches and leaves;the Ca²⁺emission factor released by burning birch bark is not significantly different from the Na⁺,NH₄⁺,and Mg²⁺emission factors,which is different from the other four tree species;Quercus mongolica The emission factors of K⁺,Ca²⁺and Cl^-three ions released by combustion are larger than those of bark;compared with the other four tree species,the proportion of Ca²⁺released by poplar combustion decreased and the proportion of F^-released increased.（4）The order of the average emission factors for the release of 16elements in PM_2.5from the burning of 5 tree species in the Greater Xing’an Mountains is:Ca>K>Zn>Mg>Cu>Ba>Ni>Sr>Pb>As>Se>Mn>Li>Co>Cr>Cd,in which the sum of the emission factors of Ca,K,Zn and Mg accounts for 96.1%of the total of the 16 element emission factors.Elemental emission factors vary widely among different tree species.The emission factor of coniferous trees is generally higher than that of broad-leaved trees.There is no significant difference in the total amount of elements emitted between different organs.The other 15elements except Cd are not significantly different between different organs（P>0.05）;different organs of different tree types burn The distribution order of water-soluble elements in PM_2.5released is relatively consistent,and the emission factors of Ca,K,Zn,and Mg are higher in all three organs.（5）During the combustion of the branches and leaves of different tree species,a total of 4 NMHCs were released,including 19 alkanes,15olefins,and 14 aromatics,of which olefins had the highest ozone generation potential.In addition to poplar,the emission factors for the release of alkanes from leaves of the four other tree species are greater than those from branches and bark,while poplars show that the emission factors for alkanes from the combustion of bark are greater than those from branches and leaves;Both showed that the leaves were larger than the branches and bark.The combustion emission factor of birch was expressed as branch>leaf>bark,and the combustion emission factor of poplar was expressed as bark>leaf>branch.