The Impact of Particle Size and Volatile Organics on the Light Absorption of Wildfire-like Brown Carbon Emissions from Wood Combustion
Constantinos Moularas, Irini Tsiodra, Nikolaos Mihalopoulos, Philip Demokritou, GEORGIOS A. KELESIDIS, Delft University of Technology
Abstract Number: 88
Working Group: Aerosol Physics
Abstract
Here, the light absorption of brown carbon (BrC) emitted by wood combustion is elucidated using a recently developed thermal decomposition platform coupled with a suite of real-time aerosol instrumentation and time-integrated sampling systems. The BrC particle size distribution, morphology and optical properties are closely controlled by increasing the combusted wood mass from 50 to 600 mg, finding excellent agreement with those measured for “real world” wildfire particulate matter (PM) emissions. Size-fractionation of such wildfire-like BrC reveals that the PM0.1-2.5 fraction contains high molecular weight, carcinogenic polycyclic aromatic hydrocarbons (PAHs) and absorbs up to five times more light compared to the PM0.1 fraction. Thus, increasing the combusted wood mass from 50 to 600 mg increases the PM0.1-2.5 concentration by a factor of about eight and enhances the overall BrC mass absorption cross-section, MAC, up to a factor of two. Condensation of volatile organic carbon (VOC) on BrC reduces its MAC up to 40 %. Still, the particle size seems to largely determine the BrC light absorption, as large VOC-rich particles absorb more light compared to small VOC-lean ones. The size-resolved BrC MAC measured here can be interfaced with climate models to estimate the climate impact of wildfire PM emissions.