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. 2017 May 21;44(10):5167–5177. doi: 10.1002/2017GL073056

Figure 2.

Figure 2

The RH dependencies of the effective hygroscopicity parameter κ OA,eff for isoprene‐ and monoterpene‐derived SOA. (a) The hygroscopicity parameter κ OA,eff for laboratory‐generated 100 nm particles from IP photooxidation [blue diamonds, O:C = 0.89; Pajunoja et al., 2015], organic aerosol sampled at the SOAS site in Alabama (red squares, O:C = 0.63 ± 0.06), and as predicted using two state‐of‐the‐art thermodynamic models (SPARC and AIOMFAC). The SPARC equilibrium calculations are presented for a case accounting for the solubility of the SOA components only (dashed lines) as well as a case including also treatment of adsorptive water uptake and nonideality of the aqueous phase. The AIOMFAC + EVAPORATION calculations account for mixture nonideality, a potential liquid‐liquid phase separation, coupled gas‐particle partitioning of semivolatile organic vapors and water, and a mass‐transfer correction for semisolid organic particles at low RH. (b) Same as Figure 2a but for MT ozonolysis SOA [red diamonds, O:C = 0.56; Pajunoja et al., 2015] and organic aerosol sampled at the SMEAR II station in Hyytiälä, Finland (blue squares, O:C = 0.63 ± 0.06). For details of the experiments and the model calculations, see SI.