可燃物化学性质对燃烧释放PM2.5元素成分的影响

通过自主设计的燃烧装置,对云南省6种典型乔木树种的不同器官(枝、叶、皮)室内模拟阴、明燃两种燃烧过程,收集燃烧排放颗粒物(PM_2.5)并测定K、Mg等8种元素排放因子,比较不同燃烧状态释放PM_2.5中元素含量的差异,同时分析各元素排放因子与可燃物自身元素含量之间的相关性.结果表明:可燃物中K、Mg和Ca元素含量较高,范围为(137.74~4670.70) mg/kg,微量元素Mn含量突出;阔叶可燃物元素含量普遍高于针叶,器官间元素含量差异显著;燃烧释放PM_2.5中K、Na元素排放因子较高,范围为(0.4269~4.9321)~(0.6311~3.0856) mg/kg,微量元素Zn较高、Cu最少,范围为(0.0409~0.3670)~(0.0029~0.0458) mg/kg,常量元素高于微量;树种间元素排放因子表现针叶高于阔叶,器官间较可燃物自身差异增大;燃烧状态对排放因子存在影响,常量元素普遍表现为明燃>阴燃,微量元素无明显规律;PM_2.5与可燃物各元素含量比值中,Na元素最高,其余元素占比普遍0~1%范围,微量元素含量比高于常量,针叶高于阔叶;可燃物的化学性质对其排放特性影响显著,可燃物与PM_2.5的元素间相关性较高,相关水平普遍达0.600以上,器官间不同元素相关水平表现为:常量元素普遍高于微量元素,针叶略高于阔叶,叶>皮>枝,明燃高于阴燃.

Effects of chemical properties of fuel on the composition of PM2.5 released by combustion

We simulated the flaming and smoldering combustion process of different organs (branches, leaves and barks) of six typical tree species in Yunnan Province based on a self-designed combustion apparatus. The emitted particulate matters (PM_2.5) were collected, and the emission factors of eight elements (K, Mg, etc) were measured and calculated. On this basis, the differences of element content in PM_2.5 between different combustion states were compared, and the correlations between element emission factors and element content in the fuel were analyzed. The results showed that the contents of K, Mg and Ca in the fuel were high, range of (137.74~4670.70) mg/kg, and the trace element Mn was prominent. The element content of broad-leaved species was generally higher than that in conifers, and significant differences were found among the element content from different organs. The PM_2.5 emission factors of major elements were higher than those of trace elements, K and Na were high in major elements, range of (0.4269~4.9321)~(0.6311~3.0856) mg/kg, Zn and Cu were respectively the highest and lowest in trace elements, range of (0.0409~0.3670)~(0.0029~0.0458) mg/kg . The element emission factors of PM_2.5 in conifers were higher than those in broad-leaved species, and the differences of element content (emission factor) among organs were large. The combustion state affected the emission factors of major elements (generally burning > smoldering). For the element content ratio (before and after combustion), Na occupied the highest ratio and proportion of residual elements was generally in the range of 0 ~ 1%. The trace elements were higher than the major elements, and conifers were higher than broad-leaved species. Chemical properties significantly affected the emission characteristics of fuel. The correlations between elements of fuel and emitted particulate matters were strong with coefficients > 0.60. The correlation levels of different elements in fuel were as follows: major elements were generally higher than trace elements, conifers were slightly higher than broad-leaved species, leaves > barks > branches, and flaming combustion was more significant than smoldering combustion.