Application of several activity coefficient models to water-organic-electrolyte aerosols of atmospheric interest

[摘要] In this work, existing and modified activity coefficient models are examinedin order to assess their capabilities to describe the properties of aqueoussolution droplets relevant in the atmosphere. Five differentwater-organic-electrolyte activity coefficient models were first selectedfrom the literature. Only one of these models included organics andelectrolytes which are common in atmospheric aerosol particles. In the othermodels, organic species were solvents such as alcohols, and importantatmospheric ions like NH₄⁺ could be missing. The predictions ofthese models were compared to experimental activity and solubility data inaqueous single electrolyte solutions with 31 different electrolytes.Based on the deviations from experimental data and on the capabilities of themodels, four predictive models were selected for fitting of new parametersfor binary and ternary solutions of common atmospheric electrolytes andorganics. New electrolytes (H⁺, NH₄⁺, Na⁺,Cl^-, NO₃^- and SO₄^2-) and organics (dicarboxylicand some hydroxy acids) were added and some modifications were made to themodels if it was found useful. All new and most of the existing parameterswere fitted to experimental single electrolyte data as well as data foraqueous organics and aqueous organic-electrolyte solutions. Unfortunately,there are very few data available for organic activities in binary solutionsand for organic and electrolyte activities in aqueous organic-electrolytesolutions. This reduces model capabilities in predicting solubilities.After the parameters were fitted, deviations from measurement data werecalculated for all fitted models, and for different data types. Thesedeviations and the calculated property values were compared with those fromother non-electrolyte and organic-electrolyte models found in theliterature. Finally, hygroscopic growth factors were calculated for four 100 nmorganic-electrolyte particles and these predictions were comparedto experimental data and to predictions from other models.All of the newly fitted models show good agreement with experimental wateractivity data in binary and ternary solutions. One of the models is foractivities of non-electrolytes only, but the other three models show quitesmall deviations from measured electrolyte activities. Because there were notenough experimental data for organic and electrolyte activities, some modelsshow bigger deviation for mutual deliquescence relative humidities oforganic-electrolyte particles, but calculated growth factors for liquiddroplets are quite close to the experimental data. Even in cases withsomewhat bigger deviations, the results can be considered satisfactory,because they were calculated based mainly on the predictive properties of themodels.

[学科分类] 大气科学