大兴安岭典型乔木树种燃烧排放非甲烷总烃(NMHCs)的特性

Characteristics of NMHCs Released by Burning Typical Arbor Species in Daxing’anling Mountains

【目的】揭示不同树种燃烧排放非甲烷总烃(NMHCs)的特性,对计算不同森林类型火灾发生过程中的NMHCs总排放量、评估对大气环境和人类健康的影响有重要意义。【方法】以大兴安岭地区典型树种兴安落叶松、樟子松、白桦、蒙古栎和山杨的枝、叶和皮为对象,运用生物质模拟燃烧装置,实测分析5个树种不同燃烧状态下释放NMHCs的排放因子。烟气收集用ASP-DC-1.2型电动采样泵;NMHCs测定用Entech 7100预浓缩系统和Agilent 7890 A/5975型色谱-质谱(GC-MS)联用仪,标准气体为美国Spectra Gases Inc.的57种非甲烷烃混标。【结果】1)共检测出48种NMHCs,其中烷烃19种、烯烃15种、芳烃14种。排放因子最大的10种化合物占总NMHCs排放因子的80.86%,其中异丁烷排放因子最高,占比超过总量的1/3;2)各类化合物的排放因子(mg·kg^-1)范围是:烷烃从樟子松的359.88±101.43到蒙古栎的756.54±205.47,烯烃从白桦的285.02±71.19到兴安落叶松的358.72±92.60,芳烃从樟子松的133.24±33.96到山杨的183.48±48.10;3)5个树种NMHCs平均排放因子(mg·kg^-1)明燃状态为739.81±214.54,阴燃状态为1284.91±405.72;4)叶、枝、皮平均排放因子(mg·kg^-1)分别为1089.26±451.94、918.44±237.80、1029.39±413.84;5)蒙古栎、兴安落叶松、山杨、白桦和樟子松NMHCs排放因子分别为1259.18±331.49、1111.56±248.53、1019.17±270.76、889.05±235.58、782.86±309.07 mg·kg^-1;6)5个树种的平均臭氧生成潜势为3.678 g·kg^-1,烷烃、烯烃和芳烃的臭氧生成潜势分别占总量的16%、73%和11%。【结论】大兴安岭地区5个典型树种燃烧排放3类(烷烃、烯烃、芳烃)共48种非甲烷烃,其中异丁烷的排放因子最高,烯烃臭氧生成潜势最高。非甲烷总烃排放量与燃烧状态相关,阴燃条件下燃烧效率整体较低,NMHCs排放因子显著大于明燃;不同生物质之间的碳含量无显著差异,故NMHCs排放因子未表现出极显著差异,但NMHCs排放因子影响因素众多,导致不同树种燃烧非甲烷总烃平均排放因子不尽相同,顺序为蒙古栎>兴安落叶松>山杨>白桦>樟子松;叶和皮的NMHCs平均排放因子略大于枝。

【Objective】It is of great significance to reveal the characteristics of non-methane hydrocarbons(NMHCs)emitted from the combustion of different tree species in order to calculate the total emissions of NMHCs in the process of different types of forest fires and to evaluate the impact on the atmospheric environment and human health.【Method】The branch,leaves and bark of the typical tree species of Larix gmelinii,Pinus sylvestris var.mongolica,Quercus mongolica,Betula platyphylla and Populus davidiana in the Daxing’anling Mountains were used as objects.A biomass simulation combustion device was used to measure and analyze the emission factors and characteristics of NMHCs released by five tree species under different combustion conditions.The flue gas is collected by ASP-DC-1.2 electric sampler.NMHCs was determined by Entech 7100 preconcentration system and Agilent 7890A/5975 chromatography-mass spectrometry(GC-MS).The standard gas was a mixture of 57 kinds of non-methanes from Spectra Gases Inc.,USA.【Result】1)A total of 48 NMHCs were detected,of which 19 were alkanes,15 were alkenes,and 14 were aromatics.The 10 compounds with the largest emission factors accounted for 80.86%of the total NMHCs emission factors,among which i-Butane had the highest emission factor,accounting for more than 1/3 of the total NMHCs emission factor;2)The emission factors(mg·kg^-1)of various compounds ranged from 359.88±101.43 alkanes of Pinus sylvestris var.mongolica to 756.54±205.47 alkanes of Quercus mongolica,and from 285.02±71.19 alkenes of Betula platyphylla to 358.72±92.60 alkenes of Larix gmelinii,and from 133.24±33.96 aromatics of Pinus sylvestris var.mongolica to 183.48±48.10 aromatics of Populus davidiana;3)The average emission factor(mg·kg^-1)of NMHCs in the five tree species was 739.81±214.54 in the flaming state,and 1284.91±405.72 in the smoldering state;4)The average emission factors(mg·kg^-1)of leaves,branch and bark were 1089.26±451.94,918.44±237.80,and 1029.39±413.84,respectively;5)The emission factors(mg·kg^-1)of Quercus mongolica,Larix gmelinii,Populus davidiana,Betula platyphylla and Pinus sylvestris var.mongolica,and were 1259.18±331.49,1111.56±248.53,1019.17±270.76,889.05±235.58,782.86±309.07,respectively;6)The average ozone forming potential of the five tree species was 3.678 g·kg^-1.The ozone forming potential of alkanes,alkenes and aromatics accounted for 16%,73%and 11%of the total,respectively.【Conclusion】In the Daxing’anling Mountains,five typical arbor species emit three types of total non-methane hydrocarbons(alkanes,alkenes,and aromatics)when burning.Among them,i-Butane has the highest emission factor,and alkenes have the highest ozone forming potential.The total non-methane hydrocarbon release is related to combustion status.The overall combustion efficiency is low under smoldering condition,and the NMHCs emission factor is significantly higher than that of flaming combustion;There is no significant difference in carbon content among different biomass,so NMHCs emission factors do not show extremely significant differences.However,there are many influencing factors of NMHCs emission factors,leading to different average emission factors of non-methane total hydrocarbons by combustion in different tree species,the order is Quercus mongolica>Larix gmelinii>Populus davidiana>Betula platyphylla>Pinus sylvestris var.mongolica;the average emission factors of NMHCs in leaves and bark are slightly larger than those in branch.