aerosols, carbon, emissions, FIRE BEAR Project, fire regimes, forest fire behavior, Scotch pine, Siberia,

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Approximately 20 experimental fires were conducted on forest plots of 1–4 ha each in 2000–07 in two types of boreal forests in central Siberia, and 18 on 6 × 12-m plots in 2008–10. These experiments were designed to mimic wildfires under similar burning conditions. The fires were conducted in prescribed conditions including full documentation on pre-fire weather, pre-fire and post-fire forest fuels, fire intensities, and other biological, physical and chemical parameters. The amount of particulate matter emitted during a typical fire averaged 0.6 t ha–1 and ranged within 0.2–1.0 t ha–1 depending on burning conditions. Particulates accounted for ~1–7% of the total mass of the consumed biomass during a typical forest fire (10–30 t ha–1 based on our data from 2000–07). Most of the particulate matter consists of organic substances, 77% on average, with a range of 70–90%. Elemental carbon averaged 8%, with a range of 2–18%. Trace element compositions and amounts of particulates indicate that there was no actual difference in the element emissions sampled from the fires conducted in the two forest types (6–8% in larch forest and 8% in pine forest). Most of the particulate matter, 90–95%, consists of submicrometre and near-micrometre particles ~0.1–5 μm in diameter.

Siberian boreal forest fires burn large areas annually, resulting in smoke that releases large amounts of particulate emission into the atmosphere. We sampled aerosol emissions from experimental fires on three Scots pine (Pinus sylvestris L.) forest sites of central Siberia. Emissions from ground-based aerosol samples were 0.1-0.7 t/ha. This value represented 1%-7% of the total biomass (10-30 t/ha) consumed during the experimental fires. We were able to classify the chemical composition of 77%-90% of the mass of particulate fire emissions. Chemical analysis indicated that an average of 8%-17% of the particulate composition was of mineral origin. Carbonaceous aerosols created because of incomplete combustion ranged from 50% to 70% of the total aerosol mass. The fraction of aerosols containing elemental carbon (EC) (i.e., graphite, soot, and charcoal) was 7%-15%. As our samples were taken near the ground surface, these results represent freshly emitted fire aerosols that have not yet had time to react with atmospheric moisture or to undergo postfire chemical or physical-chemical changes. In a typical year, where 12 × 10 6 -14 × 10 6 ha burn in Russia, we estimate that 3 × 10 6 -10 × 10 6 t of particulate matter may be emitted into the atmosphere.Résumé : À chaque année, les incendies brûlent de vastes zones de forêt boréale en Sibérie. Ces incendies produisent de la fumée qui relâche dans l'atmosphère de grandes quantités de particules. Ils ont échantillonné les émissions d'aérosols provenant de feux expérimentaux dans trois forêts de pin sylvestre (Pinus sylvestris L.) du centre de la Sibérie. Sur la base d'échantillons d'aérosols prélevés au sol, les émissions atteignent 0,1-0,7 t/ha. Cette valeur représente 1 % -7 % de la biomasse totale (10-30 t/ha) consumée par les feux expérimentaux. Les auteurs ont pu classer la composition chimique de 70 % -90 % de la masse des émissions de particules dues au feu. L'analyse chimique a montré que 8 % -17 % des particules sont d'origine minérale. Les aérosols carbonés provenant de la combustion incomplète comptent pour 50 % -70 % de la masse totale d'aérosols. La proportion des aérosols contenant du carbone élémentaire (c.-à-d. du graphite, de la suie et du charbon) est de 7 % -15 %. Étant donné que nos échantillons ont été prélevés près de la surface du sol, ces résultats représentent les aérosols fraîchement émis par le feu qui n'ont pas eu le temps de réagir avec l'humidité atmosphérique ou subir des modifications chimiques ou physico-chimiques à la suite du feu. Au cours d'une année typique en Russie, où 12 × 10 6 -14 × 10 6 ha de forêt sont détruites par le feu, ils estiment que 3 × 10 6 -10 × 10 6 t de particules seraient émises dans l'atmosphère.[Traduit par la Rédaction] Samsonov et al. 2217

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