AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
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Physical and Chemical Characterization of Fresh and Aged Emissions from Open Combustion of Biomass Fuels
CHIRANJIVI BHATTARAI, Vera Samburova, Deep Sengupta, Michealene Iaukea-Lum, Adam Watts, Hans Moosmuller, Andrey Khlystov, Desert Research Institude
Abstract Number: 598 Working Group: Combustion
Abstract Biomass burning (BB) emissions and their atmospheric oxidation products can contribute significantly to radiative forcing (RF) of climate. This forcing could either be positive or negative, depending on whether light scattering or light absorption dominates the optical properties of the emitted particles. It has been long established that in addition to light scattering, BB organic aerosols (BBOA) contribute to direct absorption of solar radiation due to the presence of the so-called brown carbon (BrC). Very little is known about this fraction of BBOA, its abundance in BB emissions, its optical properties, and chemical evolution in the atmosphere. This lack of knowledge leads to large uncertainties in climate models. In this presentation we will describe a laboratory BB study aimed for comprehensive optical, physical, and chemical characterization of both fresh and aged BB emissions, as well as its main findings. In this study, Aerodyne Oxidative Flow Reactor (OFR) was used to mimic atmospheric oxidation processes. The OFR was characterized in terms of OH production rate, residence time distribution (RTD), and particle transmission efficiency. Emission factors of main air pollutants [particulate matter, organic carbon (OC) and elemental carbon (EC), nitric oxide (NO)] were determined for globally and regionally important biomass fuels: Siberian peat, Florida peat, FASMEE (fuels from high-elevation (2740 m) boreal forest) and Hawken fire (fuels from Reno, NV, USA, representing semi-arid dryland). Measured emission factors (EF) for OC ranged from 0.85 (± 0.24) mg/g to 6.56 (± 1.40) mg/g with the EFs for EC ranges 0.02 (± 0.01) mg/g to 0.16 (± 0.01) mg/g. The ratio of organic mass to total organic carbon mass for these fuel ranged from 1.04 (± 0.04) to 1.34 (± 0.24). The effect of oxidation processes on aerosol size distribution and optical properties will also be discussed.