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Composition and light absorption of N-containing aromatic compounds in organic aerosols from laboratory biomass burning
Citation:
Xie, M., X. Chen, M. Hays, AND A. Holder. Composition and light absorption of N-containing aromatic compounds in organic aerosols from laboratory biomass burning. Atmospheric Chemistry and Physics. Copernicus Publications, Katlenburg-Lindau, Germany, 19(5):2899-2915, (2019). https://doi.org/10.5194/acp-19-2899-2019
Impact/Purpose:
This manuscript presents the composition of nitroaromatic compounds found in biomass burning emissions. Nitroaromatic compounds are a class of brown carbon chromophores detected in ambient particulate matter. In this work we show that nitroaromatic compounds contribute to near UV and short wavelength visible absorption from biomass burning smoke and are unique from other types of brown carbon, such as that from secondary organic aerosol.
Description:
The compositional details of nitroaromatic compounds (NACs) emitted during biomass burning (BB) and their contribution to light-absorbing organic carbon (OC), also termed brown carbon (BrC), are poorly understood. In this study, three laboratory BB experiments were conducted with two U.S. pine forest understory fuels typical of those consumed during prescribed fires. During the experiments, submicron aerosol particles were collected on filter media and subsequently solvent-extracted and analyzed for their optical and chemical properties. Fourteen NACs were identified in these samples, four of which (C10H11NO4, C10H11NO5, C11H13NO5 and C11H13NO6) have not been observed previously in chamber-based secondary organic aerosols, and are expected to have methoxyphenol-type structure specific to the pyrolized biomass lignin based on mass spectral evidence, suggesting these compounds may be unique to BB aerosols. In composite flaming and smoldering samples, the total NACs show similar average mass contributions to organic matter for the three BB experiments, ranging from 0.11 ± 0.017 to 0.13 ± 0.059%. The NAC distributions in these samples were also similar. The average contribution of total NACs to sample extracts absorption for flaming samples (0.80 ± 0.23 – 2.44 ± 0.67%) are higher than that for smoldering samples (0.12 ± 0.047 – 1.00 ± 0.40%). However, more light-absorbing compounds with high molecular weight need to be identified to explain the unknown fractions (> 95%) of BrC absorption.
URLs/Downloads:
DOI: Composition and light absorption of N-containing aromatic compounds in organic aerosols from laboratory biomass burning
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