Temperature changes and main gas release characteristics of Larix gmelinii plantations during smoldering in Daxing’anling Mountain region of Heilongjiang Province, northeastern China
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摘要:
目的 模拟阴燃过程，研究土壤表层温度变化规律和气体释放特征，为阴燃燃烧动力学、阴燃蔓延机制和阴燃火灾监测等研究提供理论支持。 方法 以大兴安岭地区兴安落叶松人工林土壤为研究对象，通过阴燃炉实验，分析测定不同燃烧时间下的土壤温度和气体（CO2、CO）释放量，及不同含水率（20%、30%、40%）对气体释放量的影响。 结果 阴燃过程中土壤表层温度呈现先快速增加，然后保持平稳，最后快速下降直至熄灭的变化趋势；根据土壤表层温度变化特征，将阴燃过程分为点燃期、上升期、稳定期和熄灭期4个阶段，各阴燃阶段校正燃烧效率（MCE）均小于0.75；阴燃过程中CO2平均释放量为316.23 mg/m3，CO平均释放量为101.25 mg/m3；阴燃过程中CO呈现持续性释放状态，CO2呈现间歇性释放状态；燃烧时间对CO2和CO释放量存在显著性影响，但CO2和CO释放量不存在相关关系；不同含水率下，CO2释放量呈现显著性差异（P ˂ 0.05），但CO释放量无显著性差异（P ˃ 0.05）。 结论 根据阴燃中的温度和气体变化，阴燃在14 h 后出现向明燃转化的趋势，但由于土壤中可燃物含量下降，最终未转化为明燃；由于含水率升高导致土壤氧气含量下降和热量损失增加，因此CO2释放量降低；在含水率20% ~ 40%的条件下，阴燃均可以维持蔓延传播，因此CO释放量无显著性差异。 Abstract:Objective This paper simulates the smouldering combustion process, and discusses the characteristics of soil surface temperature and main emissions in order to provide scientific reference for smouldering combustion kinetics, spread mechanism and fire monitoring. Method Taking the forest soil in the Larix gmelinii plantations of the Daxing’an Mountains as the research object, the temperature variation, main emissions and the effect of moisture content (20%, 30%, 40%) on emissions were analyzed by the results of smouldering furnace experiment. Result The soil surface temperature firstly increased rapidly, then remained stable, and finally decreased rapidly until extinguished during the smouldering combustion process; according to the characteristics of soil surface temperature, the smouldering combustion was divided into four stages, i.e. ignition stage, rise stage, steady stage and extinguishing stage, and the modified combustion efficiency (MCE) of each smoldering stage was less than 0.75; the average concentration of CO2 was 316.23 mg/m3, and the average concentration of CO was 101.25 mg/m3; in the smouldering combustion process, CO2 emission was intermittent, but CO emission was continuous; combustion time had a significant effect on CO2 and CO, but there was no correlation between CO2 and CO; there was significant difference between the concentration of CO2 under different moisture contents (P < 0.05), but there was no significant difference between the concentrations of CO (P > 0.05). Conclusion The smouldering combustion shows a trend of conversion to flaming combustion after 14 h, according to the temperature and emission variation during the smouldering furnace experiment, but the combustion burnt out in the end for the decrease of combustible content; the concentration of CO2 decreases with the increase of water content, resulting from the decrease of oxygen content and the increase of heat loss; smoldering combustion could maintain spread with moisture content of 20%−40%, so the concentration of CO has no significant difference. -
图 2 阴燃过程中的土壤表层温度及MCE值变化
Figure 2. Surface temperature of soil and MCE in the smouldering combustion process
图 3 阴燃过程中的CO2和CO释放
Figure 3. Emission of CO2 and CO during the smouldering combustion process
图 4 不同含水率下CO2和CO释放量差异性分析
不同小写字母表示CO2释放量存在显著差异（P ˂ 0.05）；不同大写字母表示CO释放量存在显著差异（P ˂ 0.05）。Different lowercase letters indicate significant differences in CO2 emission (P ˂ 0.05）；varied capital letters indicate significant differences in CO emission(P ˂ 0.05).
Figure 4. Difference analysis on the emission of CO2 and CO of different water contents
表 1 样地基本信息
Table 1. Basic information of sample plots
编号
No.树种组成
Tree species composition海拔
Altitude/m经纬度
Longitude and latitude胸径
DBH/cm林龄/a
Forest age/year郁闭度
Canopy density1 8兴安落叶松
8 Larix gmelinii
1白桦
1 Betula platyphylla
1 蒙古栎
1 Quercus mongolica566.0 124°02′24″E
50°20′24″N22.4 22 0.7 2 兴安落叶松
Larix gmelinii406.3 124°05′24″E
50°19′05″N22.5 27 0.5 3 9兴安落叶松
9 Larix gmelinii
1白桦
1 Betula platyphylla379.7 124°06′36″E
50°18′00″N21.2 26 0.8 4 兴安落叶松
Larix gmelinii407.2 124°04′48″E
50°18′00″N20.6 28 0.8 5 8兴安落叶松
8 Larix gmelinii
1 白桦
1 Betula platyphylla
1蒙古栎
1 Quercus mongolica553.8 124°01′12″E
50°21′00″N14.8 16 0.7 
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表 2 阴燃过程及基本情况
Table 2. Process of the smouldering combustion and basic information
阴燃阶段
Smouldering stage燃烧时间
Combustion
time/h燃烧过程
Combustion process平均校正燃烧效率
Average modified combustion
efficiency (MCE)平均温度
Average temperature/℃点燃期
Ignition stage (Ⅰ)0 ~ 2 地表温度快速上升至 100 ℃ 以上
Soil surface temperature rises rapidly to more than 100 ℃0.34 ± 0.47 100.71 ± 114.14 上升期
Rise stage (Ⅱ)2 ~ 6 地表温度逐渐上升至 400 ℃ 左右
Soil surface temperature rises gradually to about 400 ℃0.58 ± 0.13 281.25 ± 94.03 稳定期
Steady stage (Ⅲ)6 ~ 12 地表温度稳定在400 ~ 500 ℃
Soil surface temperature stays around 400−500 ℃0.31 ± 036 425.81 ± 41.99 熄灭期
Extinguishing stage (Ⅳ)> 12 地表温度快速下降
Soil surface temperature decreases rapidly0.17 ± 0.33 253.31 ± 146.12
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表 3 燃烧时间对CO2和CO释放量的影响（单因素分析）
Table 3. Effects of combustion time on the emission of CO2 and CO (one-way ANOVA test)
气体种类
Gas typedf F P CO2 8 2.946 0.013 CO 8 2.843 0.017
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