Dispersal and morphological characteristics of smoke particulate emission from fires in the boreal forests of Siberia

Abstract

About 10–14 million hectares of Siberian boreal forests burn annually. These forest fires, which amount to 300–500 million tons of biomass each year, result in smoke emission into the atmosphere. Direct measurements of smoke emissions conducted in several natural fire experiments at a taiga in Krasnoyarsk Territory between 2000–2009 have shown that the total amount of particulate emission from the fire is estimated to be 0.2–1 t/ha. These values represent 1–7% of the total biomass consumed during a typical forest fire in Siberia (15–30 t/ha); the remaining 93–99% of the burnt biomass are gaseous combustion products. Data on the disperse characteristics of particulate smokes, averaged over 16 natural fire experiments from 2007–2009, have shown that (89 ± 8)% of the total aerosol matter are in particles with aerodynamical diameters of less than 3 μm, (7 ± 6)% are in particles of 3–5 μm, and the remaining 5–10% of material is in particles larger than 7 μm. The morphological structure of the smoke particles indicates that submicron particles are formed due to condensation of organic vapors directly over a combustion zone, followed by their coagulation into particles of 1–3 μm. The elemental composition of the fine fraction of smoke emission, measured with the use of X-ray fluorescence with synchroton radiation excitation, is demonstrated to be used for discrimination between the sources of the elements.