Fine Particle Emissions From Tropical Peat Fires Decrease Rapidly With Time Since Ignition

Area of Science:

• Environmental Science
• Atmospheric Chemistry
• Ecology

Background:

• Southeast Asia frequently experiences peatland fires, causing severe regional haze and high fine particulate matter (PM2.5) concentrations.
• Previous studies indicated high PM2.5 emissions from tropical peat fires, but new research suggests these estimates may be significantly underestimated.

Purpose of the Study:

• To report higher PM2.5 emission factors from newly ignited tropical peat fires in Malaysia.
• To provide the first mechanistic explanation for the variability in PM2.5 emission factors from peat fires.
• To offer updated recommendations for PM2.5 emission factors for climate and air quality modeling.

Main Methods:

• Conducted field measurements of PM2.5 emission factors at newly ignited peat fires in Malaysia.
• Performed laboratory measurements of burning peat to analyze the fire progression and ash layer effects.
• Analyzed the relationship between ash layer buildup and PM2.5 emission rates.

Main Results:

• Measured PM2.5 emission factors at newly ignited peat fires were higher than previously reported, potentially underestimating emissions by a factor of three or more.
• Demonstrated that the buildup of a surface ash layer during peat fires causes a decrease in PM2.5 emissions over time.
• Found that peat fires are most hazardous in terms of aerosol emissions during their initial ignition phase.

Conclusions:

• Current estimates of PM2.5 emissions from tropical peat fires may be significantly underestimated.
• The variability in PM2.5 emission factors is mechanistically explained by the formation of an ash layer.
• Updated emission factor recommendations are provided for newly ignited fires (58 g/kg, decreasing by 9%/day) and average conditions (24 g/kg) to improve air quality and climate models.