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<p>Smoldering fire of forest duff releases substantial amounts of gases, with emissions significantly influenced by fuel properties and combustion conditions. This study investigates the transient emissions of four main gas species (CO<sub>2</sub>, CO, CH<sub>4</sub>, and NH<sub>3</sub>) from smoldering forest duff with four distinct particle size ranges (2 &lt; <i>d</i><sub>1</sub> ≤ 4&#xa0;mm, 1 &lt; <i>d</i><sub>2</sub> ≤ 2&#xa0;mm, 0.425 &lt; <i>d</i><sub>3</sub> ≤ 1&#xa0;mm, and <i>d</i><sub>4</sub> ≤ 0.425&#xa0;mm) under controlled laboratory conditions. Based on the real-time mass loss rate (MLR), the combustion process was categorized into three stages: ignition, spread (decline and growth), and burn out. During the relatively steady spread (growth) stage, the geometric mean mass flux of CO<sub>2</sub> and CO for the largest particle size (<i>d</i><sub>1</sub>) was relatively higher than that for the smallest particle size (<i>d</i><sub>4</sub>), while NH<sub>3</sub> and CH<sub>4</sub> from <i>d</i><sub>1</sub> remained lower. Within the spread (growth) stage, the geometric mean emission factor (EF) calculated by MLR (EF<sub>m</sub>) was higher than the EF calculated by the carbon balance approach (EF<sub>b</sub>) across all particle sizes, with the discrepancy more pronounced in low carbon content particles (<i>d</i><sub>1</sub> and <i>d</i><sub>4</sub>). The EF(CO<sub>2</sub>)/EF(CH<sub>4</sub>) ratios can differentiate the various smoldering stages. For the first time, the transient carbon emission factor (CEF) was calculated using two methods, with CEF<sub>m</sub> being found to provide more detailed insights into smoldering combustion dynamics. This study enhances the understanding of the gaseous emissions of forest duff across different particle sizes and examines the discrepancies between EF calculation methods.</p>

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Variations in Gaseous Emissions from Smoldering Fire of Size-Fractioned Forest Duff Particles

  • 期刊论文

  • 发表日期：

    2025年8月22日

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  • Ruichen Wang,
  • Jiuling Yang,
  • Haoliang Wang,
  • Zhijian Fu,
  • Yuqi Hu

摘要

Smoldering fire of forest duff releases substantial amounts of gases, with emissions significantly influenced by fuel properties and combustion conditions. This study investigates the transient emissions of four main gas species (CO2, CO, CH4, and NH3) from smoldering forest duff with four distinct particle size ranges (2 < d1 ≤ 4 mm, 1 < d2 ≤ 2 mm, 0.425 < d3 ≤ 1 mm, and d4 ≤ 0.425 mm) under controlled laboratory conditions. Based on the real-time mass loss rate (MLR), the combustion process was categorized into three stages: ignition, spread (decline and growth), and burn out. During the relatively steady spread (growth) stage, the geometric mean mass flux of CO2 and CO for the largest particle size (d1) was relatively higher than that for the smallest particle size (d4), while NH3 and CH4 from d1 remained lower. Within the spread (growth) stage, the geometric mean emission factor (EF) calculated by MLR (EFm) was higher than the EF calculated by the carbon balance approach (EFb) across all particle sizes, with the discrepancy more pronounced in low carbon content particles (d1 and d4). The EF(CO2)/EF(CH4) ratios can differentiate the various smoldering stages. For the first time, the transient carbon emission factor (CEF) was calculated using two methods, with CEFm being found to provide more detailed insights into smoldering combustion dynamics. This study enhances the understanding of the gaseous emissions of forest duff across different particle sizes and examines the discrepancies between EF calculation methods.