Sodium and magnesium are major components of sea salt aerosols. Their salts of chlorides, sulfates and nitrates are hygroscopic. In this research, water activities of aqueous solutions of NaCl-MgCl2 (molar ratio 1:1), NaNO3-Mg(NO3)2 (1:1), Na2SO4-MgSO4 (1:1), NaCl-Mg(NO3)2 (1:1 and 3:1), NaCl-MgSO4 (1:1), and NaNO3-MgSO4 (1:1) were measured from dilute concentrations to high supersaturations using an electrodynamic balance. We employed a dynamic method, which is based on continuous measurements of the balancing voltage of the particle as a result of a step decrease of the relative humidity (RH) of the feed to the electrodynamic balance. Good agreements are found between the predictions of the ZSR (Zdanovskii-Stokes- Robinson) and the KM (Kusik and Meissner) models and the experimental data, with the exception of Na2SO4-MgSO4 solutions. Analysis of the time-series data reveals that Na2SO4-MgSO4 solution has a lower evaporation rate than other solutions. We postulate that this is due to internal mass transfer limitation when the particle forms a gel at high concentration. Partial crystallization of NaCl-MgCl2, NaCl-Mg(NO3)2 (3:1), and NaCl-MgSO4 mixtures occurs in the measurements taken at low RHs. The particles continue to lose water as RH decreases further. Other systems, including NaCl- Mg(NO3)2 (1:1), do not crystallize even at RH = 30%. Crystallization of NaCl is suppressed when sufficient amount of nitrate is present. (C) 2000 Elsevier Science Ltd.
Bibliographical noteGenerated from Scopus record by KAUST IRTS on 2023-07-06
ASJC Scopus subject areas
- Environmental Science(all)
- Atmospheric Science