Laboratory Measurements of Particle Emissions from Smouldering Peat Fires

Smouldering peat fires are the dominant source contributing to transboundary haze, especially in Southeast Asia during dry spells. These periodical air pollution episodes include a large amount of particle emissions which result in respiratory and cardiovascular health emergencies among populations, and can lead to regional dispute and public criticism, but are poorly understood. In this work, a series of controlled small scale smouldering experiments were conducted to characterise and quantify the particle emissions from the burning of Irish sphagnum peat samples. Simultaneous measurements of mass loss rate, temperature profile, visual and infrared imaging and the mass of size-fractioned particles (PM10, PM2.5 and PM1) revealed that transient emissions vary in time with three observed fire stages (ignition, spread and burn out) which are characterised by different combustion dynamics. When peat mass loss rate peaked, the fire released the maximum amount of particles. Furthermore, the spread stage was found to emit more fine particles below 2.5 μm while the ignition stage generated more coarse particles (between 2.5 and 10 μm). This novel framework reveals that the emission variability is possibly attributed to different particle formation mechanism between peat pyrolysis and char oxidation. Understanding the smouldering particle emissions that differ significantly to those from flaming combustion is expected to accelerate the development of strategy tackling regional haze pollutions evolved from ubiquitous peat fire events.

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