Dynamic fire emission of smoldering peat under water suppression

The persistent smoldering peat fires are most difficult to extinguish because of their hidden nature and resurgence from underground. This study experimentally investigated the effects of water spray (fixed at 0.4 L/min or 600 mm/h) on the smoldering peat sample (20 cm × 20 cm × 10 cm) and associated gas emissions. The spray duration varied from 10 to 150 s, equivalent to water depths up to 25 mm. The dynamic emissions of CH 4 , CO, CO 2 , NH 3 , and C 6 H 14 were measured during the burning and suppression. After water spray, three distinct outcomes were observed: failed, partial, or complete fire suppression. Notably, an accumulated water depth below 25 mm failed to achieve complete fire suppression. In cases of failed suppression, the smoldering fire resurged and ultimately consumed all peat. With increasing water volume, both the time to resurgence and the subsequent emission peak were delayed. The peak mass fluxes and emission factors (EF) of CO 2 and CO, along with the modified combustion efficiency (MCE) and CO/CO 2 ratio, exhibited weak dependence on water volume. In contrast, at the threshold water depth of 25 mm, the peak mass flux and EF of CH 4 , as well as the CH 4 /CO 2 ratio, decreased by approximately 50%. This work advances the scientific understanding of transient gaseous emissions from hidden underground peat fires subjected to water suppression. • Emissions from smoldering peat fires affected by water suppression were investigated • Increasing water volume delayed smoldering resurgence and the time to reach emission peak • Dynamic emissions of CO 2 and CO, and MCE and CO/CO 2 are insensitive to water spray • Continuous water spray significantly reduces CH 4 emissions by weakening pyrolysis front