Development and application of thermodynamic models of chemical equilibrium in multi-phase organic/electrolyte/water mixtures for prediction of atmospheric organic particulate matter levels

This dissertation advances the modeling of particulate matter formation in atmospheric aerosols containing organic compounds, inorganic salts, and water. A thermodynamic framework is developed that allows unrestricted gas–particle partitioning and liquid–liquid phase separation, supported by X‑UNIFAC.2, an extended activity‑coefficient model incorporating middle‑range ionic interactions. Model predictions show good agreement with chamber measurements of secondary organic aerosol formation. The work further extends the two‑product SOA model to account for humidity effects, water uptake, activity coefficients, molecular weight variation, and phase separation. Together, these improvements enhance the physical realism and predictive capability of aerosol models used in atmospheric chemistry.