Fine Particle Emissions From Tropical Peat Fires Decrease Rapidly With Time Since Ignition. Issue 10 (16th May 2018)

• Record Type: Journal Article
• Authors: Roulston, C.; Paton‐Walsh, C.; Smith, T. E. L.; Guérette, É.‐A.; Evers, S.; Yule, C. M.; Rein, G.; Van der Werf, G. R.
• Is Part Of: Journal of geophysical research. Volume 123:Issue 10(2018)
• Page Start: 5607
• Page End: 5617
• Publication Date: 2018-05-16
• Subjects: peat -- PM2.5 -- fire -- emissions; Atmospheric physics -- Periodicals; Geophysics -- Periodicals; 551.5
• DOI: 10.1029/2017JD027827
• Languages: English
• ISSNs: 2169-897X

Abstract

Abstract: Southeast Asia experiences frequent fires in fuel‐rich tropical peatlands, leading to extreme episodes of regional haze with high concentrations of fine particulate matter (PM2.5 ) impacting human health. In a study published recently, the first field measurements of PM2.5 emission factors for tropical peat fires showed larger emissions than from other fuel types. Here we report even higher PM2.5 emission factors, measured at newly ignited peat fires in Malaysia, suggesting that current estimates of fine particulate emissions from peat fires may be underestimated by a factor of 3 or more. In addition, we use both field and laboratory measurements of burning peat to provide the first mechanistic explanation for the high variability in PM2.5 emission factors, demonstrating that buildup of a surface ash layer causes the emissions of PM2.5 to decrease as the peat fire progresses. This finding implies that peat fires are more hazardous (in terms of aerosol emissions) when first ignited than when still burning many days later. Varying emission factors for PM2.5 also have implications for our ability to correctly model the climate and air quality impacts downwind of the peat fires. For modelers able to implement a time‐varying emission factor, we recommend an emission factor for PM2.5 from newly ignited tropical peat fires of 58 g of PM2.5 per kilogram of dry fuel consumed (g/kg), reducing exponentially at a rate of 9%/day. If the age of the fire is unknown or only a single value may be used, we recommend an average value of 24 g/kg. Plain Language Summary: This paper provides evidence that peat fire emissions of fine particulates are much larger than for other fires when the peat is newly ignited but decrease rapidly as the fire progresses. This is important because it means that newly ignited fires are particularly detrimental to ambient air quality in impacted regions. Key Points: In this study we show that emissions of PM2.5 from Malaysian peat fires are likely 3 times larger than previously assumed We show that the emissions of fine particulate matter from peat fires in the field decrease rapidly with the age of the fire We show that the likely cause is the accumulation of an ash layer as the peat burns below the surface