According to Table , the decrease of RH from 89% to 37% leads to the increase of aerosol viscosity by several orders of magnitude, and this can be attributed to enriching sucrose in micro-droplets (from 2 M to 4 M, see Table ). Table also shows that these estimated droplet viscosities are within the lower and upper limits defined by binary aqueous STS and binary aqueous sucrose at the same RHs, justifying the input parameters utilized in the present work. . It is well known that the Stokes-Einstein equation could be invalid for small molecules, such as water and O 3 , diffusing in a viscous organic matrix. According to literature, the diffusion coefficients of O 3 in protein bovine serum albumin at the viscosity of 10 4 -10 5 Pa s were found to be around 10 -7 -10 -8 cm 2 s -1 , which are a few orders of magnitude larger than those estimated by the Stokes-Einstein equation. Nevertheless, Figure demonstrates that the simulated reaction timescale is not sensitive to the increase of D b,O up to 1 × 10 -5 cm 2 s -1 , which is the upper limit defined by pure water, indicating that the potential invalid Stokes-Einstein relationship for O 3 should not affect the aerosol kinetics studied here. Finally, if the Stokes-Einstein relationship is also invalid for S 2 O 2- 3 , the viscosities determined from D b,T (see Table ) could be regarded as the lower limit of viscosity for the ternary STS : sucrose system in 2 : 4 mass ratio.