Deliquescence Behavior of Organic/Ammonium Sulfate Aerosol

Recent studies have shown that tropospheric aerosols composed of internal mixtures of organics with sulfates are quite common with the organic composing up to 50% of the particle mass. The influences of the organics on the chemical and physical properties of the aerosol are not known. In this paper, we report the solubility of a series of dicarboxylic acids in saturated ammonium sulfate solution as a function of temperature. We also report the deliquescence relative humidity (DRH) of the pure dicarboxylic acids and of mixtures of dicarboxylic acids with ammonium sulfate. For the systems studied, we find that the presence of water-soluble dicarboxylic acids caused deliquescence to occur at a lower relative humidity (RH) than pure ammonium sulfate. In contrast, the less soluble dicarboxylic acids had no measurable effect on the deliquescence relative humidity of ammonium sulfate

Phase Changes in Internally Mixed Maleic Acid/Ammonium Sulfate Aerosols

A temperature controlled flow tube system equipped with Fourier transform infrared (FTIR) detection of particle phase and relative humidity was used to measure the deliquescence and efflorescence of ammonium sulfate, maleic acid, and internally mixed maleic acid/ammonium sulfate particles. Our results indicate that maleic acid aerosols begin to take up water starting at a low relative humidity, ∼20%, and continue the constant uptake of water until the final deliquescence relative humidity (DRH), 89%, is reached. Internally mixed particles containing maleic acid and ammonium sulfate were found to deliquesce at a lower relative humidity (RH) than either of the pure species. Efflorescence studies indicated that while pure maleic acid particles crystallize at ∼18% RH, pure ammonium sulfate and all mixed aerosols effloresce at or just below 30% RH. Taken together, our results suggest that the presence of water-soluble organics internally mixed with ammonium sulfate aerosol could increase the range of conditions under which the aerosol is a solution

Deliquescence Behavior of Organic/Ammonium Sulfate Aerosol

Recent studies have shown that tropospheric aerosols composed of internal mixtures of organics with sulfates are quite common with the organic composing up to 50% of the particle mass. The influences of the organics on the chemical and physical properties of the aerosol are not known. In this paper, we report the solubility of a series of dicarboxylic acids in saturated ammonium sulfate solution as a function of temperature. We also report the deliquescence relative humidity (DRH) of the pure dicarboxylic acids and of mixtures of dicarboxylic acids with ammonium sulfate. For the systems studied, we find that the presence of water-soluble dicarboxylic acids caused deliquescence to occur at a lower relative humidity (RH) than pure ammonium sulfate. In contrast, the less soluble dicarboxylic acids had no measurable effect on the deliquescence relative humidity of ammonium sulfate

Phase Changes in Internally Mixed Maleic Acid/Ammonium Sulfate Aerosols

A temperature controlled flow tube system equipped with Fourier transform infrared (FTIR) detection of particle phase and relative humidity was used to measure the deliquescence and efflorescence of ammonium sulfate, maleic acid, and internally mixed maleic acid/ammonium sulfate particles. Our results indicate that maleic acid aerosols begin to take up water starting at a low relative humidity, ∼20%, and continue the constant uptake of water until the final deliquescence relative humidity (DRH), 89%, is reached. Internally mixed particles containing maleic acid and ammonium sulfate were found to deliquesce at a lower relative humidity (RH) than either of the pure species. Efflorescence studies indicated that while pure maleic acid particles crystallize at ∼18% RH, pure ammonium sulfate and all mixed aerosols effloresce at or just below 30% RH. Taken together, our results suggest that the presence of water-soluble organics internally mixed with ammonium sulfate aerosol could increase the range of conditions under which the aerosol is a solution