Composition of higher molecular weight organic matter in smoke aerosol from biomass combustion in Amazonia

Smoke particulate matter was sampled by high volume filtration from a controlled burn of forest litter in the northern forest reserve of INPA about 70 km north of Manaus, Amazonas. The extract of the filter was separated after methylation into hydrocarbon, ketone, carboxylic acid ester and polar fractions and then analyzed by gas chromatography and gas chromatography-mass spectrometry. The total lipid extract yield was 13 mg/m3 of smoke. The major organic components of the smoke particles were straight-chain aliphatic and triterpenoid compounds from vegetation wax, biopolymers, and gum/resin. Polynuclear aromatic hydrocarbons (PAH) from the combustion process were found at high levels and aromatized derivatives from natural product precursors were also important components. Petroleum hydrocarbons representing urban and vehicular emissions were not detectable. The n-alkanes ranged from C19 to C35, with a carbon number maximum (Cmax) at C29/C31 and an odd-to-even carbon predominance > C25 (CPI20–35 = 3.6). Terminal olefins (n-alk-1-enes) were also present and ranged from C17 to C35, with a Cmax at C22 and an even-to-odd carboon predominance (CPI17–35 = 0.8). The n-alkanes are derived mainly from vegetation wax and the alk-1-enes with other oxygenated compounds (e.g., ketones, acids, triterpenoids) are thermal alteration products from gum/resin and biopolymers. These alteration products coupled with the PAH are the tracers for biomass combustion.