title: Molecular Characterization of Brown Carbon in Biomass Burning Aerosol Particles.
abstract: Emissions from biomass burning are a significant source of brown carbon (BrC) in the atmosphere. In this study, we investigate the molecular composition of freshly emitted biomass burning organic aerosol (BBOA) samples collected during test burns of sawgrass, peat, ponderosa pine, and black spruce. We demonstrate that both the BrC absorption and the chemical composition of light-absorbing compounds depend significantly on the type of biomass fuels. Common BrC chromophores in the selected BBOA samples include nitro-aromatics, polycyclic aromatic hydrocarbon derivatives, and polyphenols spanning a wide range of molecular weights, structures, and light absorption properties. A number of biofuel-specific BrC chromophores are observed, indicating that some of them may be used as source-specific markers of BrC. On average, ∼50% of the light absorption in the solvent-extractable fraction of BBOA can be attributed to a limited number of strong BrC chromophores. The absorption coefficients of BBOA are affected by solar photolysis. Specifically, under typical atmospheric conditions, the 300 nm absorbance decays with a half-life of ∼16 h. A "molecular corridor" analysis of the BBOA volatility distribution suggests that many BrC compounds in the fresh BBOA have low saturation mass concentration (<1 μg m-3) and will be retained in the particle phase under atmospherically relevant conditions.
authors.affiliation: Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99354, United States.
authors.forename: Peng
authors.initials: P
authors.lastname: Lin
authors.affiliation: Department of Chemistry, University of California , Irvine, California 92697, United States.
authors.forename: Paige K
authors.initials: PK
authors.lastname: Aiona
authors.affiliation: Multiphase Chemistry Department, Max Planck Institute for Chemistry , Mainz, 55128, Germany.|National Institute for Environmental Studies, Tsukuba-City, Ibaraki 305-8506 Japan.
authors.forename: Ying
authors.initials: Y
authors.lastname: Li
authors.affiliation: Department of Chemistry, University of California , Irvine, California 92697, United States.|Multiphase Chemistry Department, Max Planck Institute for Chemistry , Mainz, 55128, Germany.
authors.forename: Manabu
authors.initials: M
authors.lastname: Shiraiwa
authors.affiliation: Physical Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99354, United States.
authors.forename: Julia
authors.initials: J
authors.lastname: Laskin
authors.affiliation: Department of Chemistry, University of California , Irvine, California 92697, United States.
authors.forename: Sergey A
authors.initials: SA
authors.lastname: Nizkorodov
authors.affiliation: Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99354, United States.
authors.forename: Alexander
authors.initials: A
authors.lastname: Laskin
mesh_terms: D000336:Aerosols; D001272:Atmosphere / Q000737:chemistry; D018533:Biomass; D002244:Carbon; D006207:Half-Life
chemical_list: D000336:Aerosols; D002244:Carbon