AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
Abstract View
Contribution of Water-Soluble “Brown Carbon” Organic Species to Light Absorption by Biomass-Burning Aerosols
DEEP SENGUPTA, Vera Samburova, Chiranjivi Bhattarai, Michealene Iaukea-Lum, Adam Watts, Hans Moosmuller, Andrey Khlystov, Desert Research Institute
Abstract Number: 705 Working Group: Aerosol Chemistry
Abstract The water soluble fraction of Brown Carbon (BrC) is abundant in both primary and secondary biomass-burning organic aerosols and is considered to be a significant contributor to overall light absorption by aerosols. Humic Like Substances (HULIS), which are complex high-molecular weight atmospheric organic structures, are the largest constituent of water-soluble BrC fraction by mass. Therefore, quantifications of HULIS and their light absorption properties are needed to reduce the uncertainties in radiative forcing estimates for atmospheric biomass-burning aerosols.
In our experiments, selected fuels of regional and global importance were burned under controlled conditions using the DRI biomass combustion chamber. To mimic the atmospheric oxidation process (5-7 days) of biomass-burning smoke, we performed aging of gas- and particle-phase emissions using a Potential Aerosol Mass (PAM) flow reactor Primary and PAM-aged biomass-burning aerosols were collected on Teflon filters (d=47 mm), soaked in ultrahigh-purity water, and extracted twice in 20 mL of water under ultrasonic agitation for 20 min. The HULIS fraction was separated from inorganics and low molecular weight organics by solid-phase extraction. HULIS were then quantitatively analyzed using Ultra-High Performance Liquid Chromatography (UPLC) coupled with Evaporative Light Scattering Detector (ELSD). To estimate the contribution of HULIS to the overall light absorption by biomass-burning aerosols, HULIS extracts were analyzed with the UV-Vis spectrophotometry technique. Resulting HULIS absorption spectra and mass absorption coefficients were compared with UV-Vis absorption properties of the total water-soluble and non-water-soluble (hexane) fractions. These experiments provide an insight into the effects of atmospheric aging of HULIS in biomass burning aerosols on their light absorption properties.