Investigations of primary and secondary particulate matter of different wood combustion appliances with a high-resolution time-of-flight aerosol mass spectrometer

摘要

A series of photo-oxidation smog chamber experiments were performed toinvestigate the primary emissions and secondary aerosol formation from twodifferent log wood burners and a residential pellet burner under differentburning conditions: starting and flaming phase. Emissions were sampled fromthe chimney and injected into the smog chamber leading to primary organicaerosol (POA) concentrations comparable to ambient levels. The compositionof the aerosol was measured by an Aerodyne high resolution time-of-flightaerosol mass spectrometer (HR-TOF-AMS) and black carbon (BC)instrumentation. The primary emissions were then exposed to xenon light toinitiate photo-chemistry and subsequent secondary organic aerosol (SOA)production. After correcting for wall losses, the average increase inorganic matter (OM) concentrations by SOA formation for the starting andflaming phase experiments with the two log wood burners was found to be afactor of 4.1±1.4 after five hours of aging. No SOA formation wasobserved for the stable burning phase of the pellet burner. The startupemissions of the pellet burner showed an increase in OM concentration by afactor of 3.3. Including the measured SOA formation potential, averageemission factors of BC+POA+SOA, calculated from CO emission, werefound to be in the range of 0.04 to 3.9 g/kg wood for the stable burningpellet burner and an old log wood burner during startup respectively. SOAcontributed significantly to the ion CHO at mass tocharge ratio 60, a commonly used marker for primary emissions of woodburning. This contribution at 60 can overcompensate for the degradation oflevoglucosan leading to an overestimation of the contribution of woodburning or biomass burning to the total OM. The primary organic emissionsfrom the three different burners showed a wide range in O:C atomic ratio(0.19−0.60) for the starting and flaming conditions, which also increasedduring aging. Primary wood burning emissions have a rather low relativecontribution at 43 ( 43) to the total organic mass spectrum. Thenon-oxidized fragment CH has a considerable contributionat 43 for the fresh OA with an increasing contribution of the oxygenatedion CHO during aging. After five hours of aging, the OAhas a rather low CHO signal for a given COfraction, possibly indicating a higher ratio of acid to non-acid oxygenatedcompounds in wood burning OA compared to other oxygenated organic aerosol (OOA).