Di Lorenzo, Robert APlace, Bryan KVandenBoer, Trevor CYoung, Cora J2021-12-042021-12-042018-02-06Di Lorenzo, R.A., Place, B.K., Vandenboer, T.C., Young, C.J.* 2018 Composition of size-resolved aged boreal fire aerosols: Brown carbon, biomass burning tracers, and reduced nitrogen. ACS Earth and Space Chemistry 2:278-285, doi:10.1021/acsearthspacechem.7b00137.10.1021/acsearthspacechem.7b00137http://hdl.handle.net/10315/38847Aerosols that were size-resolved into 13 fractions between 10 nm and 18 μm were collected from an aged boreal forest wildfire plume in July 2013. Samples were extracted into water and analyzed for molecular-size-resolved brown carbon (BrC), biomass burning (BB) markers, reduced nitrogen compounds, and elemental composition. Absorption of BrC was primarily in fine-mode aerosols and dominated by high-molecular-weight compounds (>500 Da). The molecular size distribution of BrC was conserved across aerosol sizes, with a decrease in the importance of large molecules in smaller aerosols. The aerosol-size-resolved composition of BrC absorption was different than those of the two BB markers, non-sea-salt potassium and levoglucosan, suggesting that they may not be suitable for identifying BB BrC in aged plumes. Strong correlations were observed between BrC and the reduced nitrogen compounds ammonium, dimethylamine, and diethylamine. In aerosols with high BrC and reduced nitrogen, there was a strong cationic excess. These observations could be caused by (i) uptake of ammonium and alkylamines to form stable salts with organic acids or (ii) reactive uptake to form imines or enamines that were hydrolyzed during the BrC extraction process.enThis document is the unedited Author’s version of a Submitted Work that was subsequently accepted for publication in ACS Earth and Space Chemistry, copyright © American Chemical Society after peer review. To access the final edited and published work see https://pubs.acs.org/articlesonrequest/AOR-js8aJYbHG26ZUGrKwxhJbiomass burning, brown carbon, molecular absorption, alkylamines, boreal wildfire, size-resolved aerosols, organic aerosolArticlehttps://pubs.acs.org/doi/abs/10.1021%2Facsearthspacechem.7b00137