Physical and Chemical Characterization of Fresh and Aged Biomass Burning Emissions
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Biomass burning (BB) emissions and their oxidation products contribute significantly to Earth's radiation budget. Limited knowledge of BB emissions and their oxidation products leads to large uncertainties in climate models. This study focused on characterization of fresh and atmospherically aged BB emissions in regard to their physical, optical and chemical properties. An oxidation flow reactor (OFR) was used to mimic atmospheric oxidation processes. The OFR was characterized for its hydroxy radical production rate, particle transmission efficiency, residence time distribution, and different time scales responsible for determining the fate of organic compounds in the OFR. To study the change in aerosol size due to atmospheric processes (for example, hygroscopic growth and evaporation/condensation), an algorithm to derive aerosol size change during the atmospheric processes using the full-aerosol size distribution was verified experimentally. The emission factors of atmospherically important pollutants were determined from the combustion of globally and regionally important biomass fuels. The measured fuel mass-based emission factors (EFs) of particulate matter (PM), organic carbon (OC), elemental carbon (EC), carbon monoxide (CO), and nitrogen oxides (NOx) were in the ranges of 1.48 - 7.98, 0.85 - 6.56, 0.02 - 0.16, 0.42 - 16.26 and 0.00 - 0.11 mg g-1, respectively. The total particle numbers emission factor were in the range of 2.88 1012 - 24.41 1012 # g-1. The ratio of organic mass to total carbon mass for the emissions from combustion of these fuels ranged from 1.04 0.04 to 1.34 0.24. The effect of the OFR aging on combustion emissions for their optical properties, size distribution and concentrations are also discussed.