Effect of airflow setting on the organic composition of woodheater emissions

Fine particle emissions from woodheaters are large contributors to ambient atmospheric pollution in a number of regional centers in Australia. The health impact of woodsmoke is not limited to the particle loading alone, and a wide range of toxic inorganic and organic compounds are also emitted as gases or adsorbed onto particles. The organic composition of woodsmoke was determined from two heater models operated using different airflow settings. Particle emission factors varied between 3 and 36 g per kg dry wood burned, with higher burn rates (open airflow) producing significantly less particle mass per kg wood burned than the low burn rates (closed airflow). Over 90 organic compounds were quantified from the vapor- and particle-phases, including furans, methoxyphenols, and other substituted aromatics, PAHs, maltols, and the sugar levoglucosan. Emission factors for the majority of the particle-phase compounds increased as the airflow was progressively closed, but decreased for some PAHs and other compounds found predominantly in the vapor-phase. Levoglucosan was the single most abundant compound, contributing 5-16% of the total particle mass. Although there was some variation in levoglucosan emissions between heater models, the fact that levoglucosan emissions vary relatively little between airflow conditions for a given heater provides the potential to use it as a general tracer for woodsmoke. In contrast, the mass fractions of many other particle-phase compounds were considerably higher when operated with a closed airflow.