title: Characterizing the aging of biomass burning organic aerosol by use of mixing ratios: a meta-analysis of four regions.
abstract: Characteristic organic aerosol (OA) emission ratios (ERs) and normalized excess mixing ratios (NEMRs) for biomass burning (BB) events have been calculated from ambient measurements recorded during four field campaigns. Normalized OA mass concentrations measured using Aerodyne Research Inc. quadrupole aerosol mass spectrometers (Q-AMS) reveal a systematic variation in average values between different geographical regions. For each region, a consistent, characteristic ratio is seemingly established when measurements are collated from plumes of all ages and origins. However, there is evidence of strong regional and local-scale variability between separate measurement periods throughout the tropical, subtropical, and boreal environments studied. ERs close to source typically exceed NEMRs in the far-field, despite apparent compositional change and increasing oxidation with age. The absence of any significant downwind mass enhancement suggests no regional net source of secondary organic aerosol (SOA) from atmospheric aging of BB sources, in contrast with the substantial levels of net SOA formation associated with urban sources. A consistent trend of moderately reduced ΔOA/ΔCO ratios with aging indicates a small net loss of OA, likely as a result of the evaporation of organic material from initial fire emissions. Variability in ERs close to source is shown to substantially exceed the magnitude of any changes between fresh and aged OA, emphasizing the importance of fuel and combustion conditions in determining OA loadings from biomass burning.
authors.affiliation: Centre for Atmospheric Science, School of Earth, Atmospheric and Environmental Science, University of Manchester, Manchester, United Kingdom. matthew.jolleys@postgrad.manchester.ac.uk
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Jolleys
authors.forename: Hugh
authors.initials: H
authors.lastname: Coe
authors.forename: Gordon
authors.initials: G
authors.lastname: McFiggans
authors.forename: Gerard
authors.initials: G
authors.lastname: Capes
authors.forename: James D
authors.initials: JD
authors.lastname: Allan
authors.forename: Jonathan
authors.initials: J
authors.lastname: Crosier
authors.forename: Paul I
authors.initials: PI
authors.lastname: Williams
authors.forename: Grant
authors.initials: G
authors.lastname: Allen
authors.forename: Keith N
authors.initials: KN
authors.lastname: Bower
authors.forename: Jose L
authors.initials: JL
authors.lastname: Jimenez
authors.forename: Lynn M
authors.initials: LM
authors.lastname: Russell
authors.forename: Michel
authors.initials: M
authors.lastname: Grutter
authors.forename: Darrel
authors.initials: D
authors.lastname: Baumgardner
mesh_terms: D000336:Aerosols / Q000032:analysis*; D000354:Africa, Western; D018533:Biomass; D002248:Carbon Monoxide / Q000032:analysis; D005390:Fires; D009930:Organic Chemicals / Q000032:analysis*; D013997:Time Factors
chemical_list: D000336:Aerosols; D009930:Organic Chemicals; D002248:Carbon Monoxide