Hygroscopicity of organic compounds from biomass burning and their influence on the water uptake of mixed organic ammonium sulfate aerosols

摘要: Abstract. Hygroscopic behavior of organic compounds, including levoglucosan, 4-hydroxybenzoic acid, and humic as well their effects on the hygroscopic properties ammonium sulfate (AS) in internally mixed particles are studied by a hygroscopicity tandem differential mobility analyzer (HTDMA). The compounds used represent pyrolysis products wood that emitted from biomass burning sources. It is found acid aerosol only slightly take up water, starting at RH (relative humidity) above ~70%. This contrasted continuous water absorption levoglucosan range 5–90% RH. However, no growth observed for particles. Predicted uptake using ideal solution theory, AIOMFAC model E-AIM (with UNIFAC) consistent with measured factors levoglucosan. use these models without consideration crystalline phases not appropriate to describe organics do exhibit uptake, such acid. Mixed consisting or different mass fractions, reduced amount 80% (above AS deliquescence) relative pure same mass. mixtures fractions agree predictions thermodynamic models. Use Zdanovskii–Stokes–Robinson (ZSR) relation lead good agreement assuming an insoluble phase. Deviations HTDMA measurement mainly due occurrence microscopical solid phase restructuring increased humidity (morphology effects), which considered containing reproduced ZSR relation. Lastly, surrogate selection some most abundant burning. growths increasing fraction representing ambient conditions wet dry seasonal period Amazon basin, significant prior deliquescence sulfate. absorptions several (including levoglucosan) close those binary sulfate, indicating constitutes major contribution (and beyond) Hence, certain can substantially affect point overall particle uptake.