title: Molecular-Size-Separated Brown Carbon Absorption for Biomass-Burning Aerosol at Multiple Field Sites.
abstract: Biomass burning is a known source of brown carbon aerosol in the atmosphere. We collected filter samples of biomass-burning emissions at three locations in Canada and the United States with transport times of 10 h to >3 days. We analyzed the samples with size-exclusion chromatography coupled to molecular absorbance spectroscopy to determine absorbance as a function of molecular size. The majority of absorption was due to molecules >500 Da, and these contributed an increasing fraction of absorption as the biomass-burning aerosol aged. This suggests that the smallest molecular weight fraction is more susceptible to processes that lead to reduced light absorption, while larger-molecular-weight species may represent recalcitrant brown carbon. We calculate that these large-molecular-weight species are composed of more than 20 carbons with as few as two oxygens and would be classified as extremely low volatility organic compounds (ELVOCs).
authors.affiliation: Department of Chemistry, Memorial University , St. John's, Newfoundland A1B 3X5, Canada.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Di Lorenzo
authors.affiliation: Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder , Boulder, Colorado 80309, United States.|Chemical Sciences Division, Earth System Research Laboratory, National Oceanic and Atmospheric Administration , Boulder, Colorado 80305, United States.
authors.forename: Rebecca A
authors.initials: RA
authors.lastname: Washenfelder
authors.affiliation: Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder , Boulder, Colorado 80309, United States.|Chemical Sciences Division, Earth System Research Laboratory, National Oceanic and Atmospheric Administration , Boulder, Colorado 80305, United States.
authors.forename: Alexis R
authors.initials: AR
authors.lastname: Attwood
authors.forename: Hongyu
authors.initials: H
authors.lastname: Guo
authors.forename: Lu
authors.identifier: 0000-0002-0021-9876
authors.initials: L
authors.lastname: Xu
authors.forename: Nga L
authors.initials: NL
authors.lastname: Ng
authors.forename: Rodney J
authors.initials: RJ
authors.lastname: Weber
authors.affiliation: Atmospheric Research & Analysis Inc. , Cary, North Carolina 27513, United States.
authors.forename: Karsten
authors.initials: K
authors.lastname: Baumann
authors.affiliation: Atmospheric Research & Analysis Inc. , Cary, North Carolina 27513, United States.
authors.forename: Eric
authors.initials: E
authors.lastname: Edgerton
authors.affiliation: Department of Chemistry, Memorial University , St. John's, Newfoundland A1B 3X5, Canada.
authors.forename: Cora J
authors.identifier: 0000-0002-6908-5829
authors.initials: CJ
authors.lastname: Young
mesh_terms: D000336:Aerosols; D000393:Air Pollutants; D001272:Atmosphere / Q000737:chemistry; D018533:Biomass; D002170:Canada; D002244:Carbon
chemical_list: D000336:Aerosols; D000393:Air Pollutants; D002244:Carbon