Fig. 2. Comparison of measured diffusion coefficients of water in α-pinene SOM with literature data. Laboratory measurements at 280 K (black crosses, with our parameterisation shown as a black line, with grey shaded uncertainty region) are compared with predictions from percolation theory at room temperature (blue circles, with blue shaded uncertainty region³⁰) and the semi-empirical method used by Berkemeier, et al. ⁵³ for low (orange dashed line and hatched error region, O:C = 0.3) and medium (red dashed line and hatched error region, O:C = 0.5) oxidation states at 280 K. Also shown are the diffusion coefficients predicted by the Stokes–Einstein (S–E) equation with a hydrodynamic diameter of water of 2 Å, using the room temperature viscosity measurements on chamber-generated α-pinene SOM by Renbaum-Wolff, et al. ¹¹ (generated using 80–100 ppb α-pinene and 300 ppb ozone, purple diamonds and bars), and on flow tube-generated α-pinene SOM (generated using 5 ppm α-pinene and 12 ppm ozone, green bars).