Fig. 6. (a) Comparison of the dependence of diffusion constants on viscosity for organic aerosols (see main text for full details). The grey envelope indicates the relationship calculated from the Stokes–Einstein equation with molecular radii of 0.2 and 1 nm (top and bottom of envelope, respectively). Diffusion constants for water in sucrose, citric acid and α-pinene SOA are shown by the black line, green line and orange bars, respectively. The upper limit on the diffusion constant that can be determined from the optical tweezers approach is shown by the dotted blue line. Diffusion constants and viscosities for the protein bovine serum albumin (BSA) in aqueous solution are shown by the purple bars; those for ozone in aqueous-BSA are shown by the blue bars. The diffusion constant for pyrene in α-pinene SOA is shown by the pink square. The range of diffusion coefficients for ozone in shikimic acid aerosol is shown by the red bar, measured over the RH range 12 to 71% RH. (b) The effective vapour pressures for MA in ternary aqueous sucrose/MA aerosol as a function of viscosity. (c) The dependencies of the reactive uptake coefficient for ozone on aqueous MA/sucrose, and N2O5 and OH on aqueous citric acid aerosol are shown by the diamonds, circles and triangles, respectively.
