Characteristics of different volatility classes of organic compounds emitted by a municipal solid waste incineration plant

Despite their important contributions to primary aerosols and roles as precursors of secondary organic aerosols, emission data for different volatility classes of intermediate-volatility and semi-volatile organic compounds (IVOC/SVOC) from combustion sources are limited. This study reports gas and particle emissions measurements for a municipal solid waste incineration facility using online mass spectrometry (i.e., proton transfer reaction-time-of-flight mass spectrometer for the gas phase and soot particle aerosol mass spectrometer for the particle phase) and offline chemical analyses (e.g., gas chromatography–tandem mass spectrometry and liquid chromatography–tandem mass spectrometry) under a variety of isothermal dilution conditions to determine the volatility distributions of organic compounds. For the volatility distribution, which represents the total emission distribution of gases and particles as a function of saturation concentrations (C∗), the peak heights are nearly the same for volatile bins with C∗ = 0 μg m−3 and 105 μg m−3, and the sum of the emissions in those bins account for 40% of the emission amounts in the volatility range of low-volatility organic compounds to IVOC (10−2 < C∗ < 106 μg m−3). The organic aerosol (OA) emission factor (EFOA) was estimated to increase 27 fold due to vapor condensation when decreasing the flue gas temperature from 200 °C to 25 °C without dilution. This increase is considered to be attributed to condensable particulate matter (CPM). However, the subsequent isothermal dilution of flue gas under realistic dilution conditions resulted in a significant decrease in EFOA. Estimates based on volatility distributions showed that when the dilution factor (DF) reached 100, EFOA was estimated to be approximately 10% that in the undiluted exhaust at 25 °C, indicating that significant evaporation of CPM occurred. The air temperature after dilution also affected EFOA, which was estimated using the volatility distributions at different temperatures and varied from −80% (40 °C) to 110% (0 °C) of the EFOA value at 25 °C. We showed that the dilution factor and the air temperature after dilution are critical factors affecting the EFs of organic compounds in the particle and gas phases, and that it is important to determine the volatility distribution of emissions in order to understand how they affect the EF dependence.