Characterization of aging wood chip combustion aerosol in an environmental chamber

Aging of aerosol from wood chip combustion in a stoker burner was monitored in an outdoor environmental chamber for 19–27 h in order to study the size, volatility and organic carbon (OC) content of the combustion aerosol particles during aging. A scanning mobility particle sizer, a volatility tandem differential mobility analyzer (VTDMA), and a thermal–optical carbon analyzer were utilized. The VTDMA and carbon analyses were performed at the beginning, after 17–24 h of aging and at one intermediate point. The size decrease of freshly emitted particles was 6–10% when heated to 360∘C, and was found to depend on the experiment start time. For particles aged for 24 h, a 74–86% decrease in particle size at 360∘C was observed. The more volatile OC fraction and the total OC fraction in the particles increased and the less volatile OC fraction decreased with aging. This suggests that during aging more volatile compounds condense on or heavier compounds photodegrade into lighter ones in the particles. Occasionally, new particle formation and growth were observed in the following day. The new particles were found to be composed mainly of volatile material.