Arctic fires and smouldering combustion: influence of soil and air temperature on fire spread

Smouldering wildfire is an important disturbance to peatlands worldwide; it contributes significantly to global carbon emissions and provides positive feedback to climate change. Herein, we explore the feasibility of firebreaks to control smouldering peat fires through laboratory-scale experiments. The dry-mass moisture content (MC) of peat soil was varied from 10% (air-dried) to 125%. We found that smouldering peat fire may be successfully extinguished above the mineral soil layer, even if the peat layer is not entirely removed. There are two criteria for an effective peat firebreak: (I) adding water to make the peat layer sufficiently wet (>115% MC in the present work); and (II) ensuring that the peat layer is thinner than the quenching thickness (< 5cm). Criterion I may fail if the water table declines or the peat layer is dried by surface fires and hot weather; thus, satisfying Criterion II is more attainable. A sloping trench-shaped firebreak is recommended to guide water flow and help maintain high peat moisture content. This work provides a scientific foundation for fighting and mitigating smouldering wildfires and provides guidance about protective measures for field-scale peat fire experiments.

Section: Experimental Methodsmentioning

confidence: 99%

How to build a firebreak to stop smouldering peat fire: insights from a laboratory-scale study

Lin

Liu

Huang

2021

“…Specifically, the interface between litter and peat layers was set to '0 cm', '+3 cm' was in the upper litter layer, and '−3 cm', '−6 cm', '−9 cm', and '−12 cm' were in the lower peat layer. Similar set-ups have also been widely used for past laboratory-scale fire experiments (Benscoter et al 2011;Christensen et al 2019;Huang and Rein 2019;Lin et al 2021a;Qin et al 2022b).…”

Section: Fuel Samples and Lab Test Setupmentioning

confidence: 99%

“…flaming) induced by a heterogeneous solid surface reaction (i.e. smouldering), which is predominantly controlled by the oxygen supply and heat loss (Santoso et al 2019;Garg et al 2023a). In this transition process, a robust smouldering reaction with a higher temperature (i.e.…”

Section: Fire Phenomenamentioning

confidence: 99%

“…1). Currently, this 'holdover' and 're-emerging' fire phenomenon has been observed in peatlands of different regions (McCarty et al 2020;Scholten et al 2021), and has also been successfully reproduced in laboratory-scale experiments (Huang and Rein 2019;Qin et al 2022b;Shan et al 2023;Yin et al 2023). However, whether a resurfacing smouldering fire can ignite a flame on the litter layer, leading to a flaming wildfire, requires more fundamental research.…”

Section: Introductionmentioning

confidence: 97%

“…Smouldering and flaming are both important combustion phenomena in wildfires, and one can transition to the other under specific conditions (Santoso et al 2019). The smouldering-to-flaming (StF) transition represents an abrupt initiation of gas-phase burning preceded by smouldering, accelerating fire spread and heat release, as well as increasing the corresponding fire hazards (Santoso et al 2019). When the resurfacing smouldering front arrives at the ground surface, it can dry and heat the accumulated litter.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Resurfacing of underground peat fire: smouldering transition to flaming wildfire on litter surface

Zhang,

Shu,

Qin

et al. 2024

Background Smouldering wildfires in peatlands are one of the largest and longest-lasting fire phenomena on Earth, but it is unclear whether such underground peat fires can resurface to the ground and ignite a flame on the litter layer. Methods This work conducted a laboratory experiment by putting a 5-cm thick litter layer (banyan tree leaves with a density of 27–53 kg/m3) onto a 10-cm thick peat sample (moisture content of 10–100%). Key results and conclusions Tests confirmed that a smouldering peat fire, ignited at the bottom, can propagate upwards and resurface to ignite a flaming wildfire on the surface litter layer. The propensity of litter to be flaming ignited decreased with increasing peat moisture content and litter layer density. We found the threshold of such surface flaming as a function of temperature and temperature increase rate at the interface between peat and litter. Finally, large field experiments successfully reproduced and validated the laboratory observations. Implications This work reveals an important wildfire ignition phenomenon that has received little attention but may cause new spot fires, accelerate fire progression and exacerbate its hazards.

Laboratory benchmark of low-cost portable gas and particle analysers at the source of smouldering wildfires

Cui,

Dossi,

Rein

2023

Background Smouldering wildfires emit large amounts of carbon, toxic gases and particulate matter (PM), posing health and environmental hazards. It is challenging to conduct field measurements on wildfire emissions, and available instruments are limited by high cost and low mobility. Aim Here, we contribute to solving this challenge by studying three commercial low-cost and portable air quality analysers (KANE101, SDS011 and FLOW) and comparing them with research-grade instruments (FTIR, PM Cascade Impactor and DustTrak). Methods A series of laboratory experiments on peat smouldering were conducted including the stages of ignition, spread and burnout to provide conditions of emission measurements near the source. Key results The gas analyser KANE101 accurately measured CO2 and allowed calculation of modified combustion efficiency (MCE). The FLOW air pollution sensor was found unsuitable for PM measurements near fire sources because of its narrow range. FLOW captured the variation of volatile organic compounds (VOCs), but measurements did not correlate well with NO2 measurements. The SDS011 PM sensor responded well in measuring PM10 in this study. Conclusions KANE101 and SDS011 can be used in the field after calibration to measure CO2/CO and PM. Implications This work provides a better understanding of how low-cost and portable emission sensors can be of use for wildfire measurements in the field.