Based on our extrapolations (Fig. ), guaiacol-NO 3 SOA is most often in a semi-solid state in the planetary boundary layer (≲ 1 km in altitude) and a glassy phase state in the free troposphere (1km ≲ altitude ≲ 18 km). The liquid state is only predicted for a limited region of the planetary boundary layer (≳ 80 ° latitude). In constant, a liquid state is predicted for almost all conditions in the planetary boundary layer for guaiacol-OH SOA (Fig. ). A glassy phase state can limit heterogeneous reactions. In addition, a glassy phase state can potentially act as a heterogeneous nucleus for ice formation in the atmosphere, although the importance of the glassy phase state for ice nucleation is still a matter of debate. Mixing time is defined as the time it takes for the concentration of the diffusing species at the particle's center to deviate by less than 1/e from the equilibrium concentration. Knowledge of the mixing time of organic molecules within SOA particles is important for forecasting both the size distribution and mass of SOA particles. Additionally, mixing time plays a key role in anticipating the long-range transport of pollutants trapped in SOA particles. Most chemical transport models assume the mixing times of organic molecules is < 1 h.