AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
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Molecular Characterization of Individual Chromophores in Atmospheric Brown Carbon
PENG LIN, Lauren Fleming, Nir Bluvshtein, Yinon Rudich, Sergey Nizkorodov, Julia Laskin, Alexander Laskin, Pacific Northwest National Laboratory
Abstract Number: 397 Working Group: Aerosol Chemistry
Abstract The chemical composition and optical properties of brown carbon chromophores pertinent to different biomass burning emissions are investigated using high performance liquid chromatography coupled to a photo diode array and high resolution mass spectrometry detectors. Brown carbon chromophores identified using this approach are attributed several classes of chemical compounds, with nitroaromatic compounds being the most common and most strongly absorbing species. In combination, nitroaromatic compounds account for 50-80% of the total visible light absorption (> 400 nm) by brown carbon extractable with water and organic solvents. Our results indicate that nitroaromatic compounds, in particular nitrophenols, are important brown carbon chromophores in aged biomass burning organic aerosol, suggesting that night time chemistry of ▪NO3 and N2O5 with particles may play a significant role in atmospheric transformations of brown carbon. The absorption spectra of the brown carbon chromophores were found to depend on the extraction solvent and on solution pH, implying that aerosol acidity is an important factor controlling light absorption properties of brown carbon.