TY - JOUR
T1 - Water activity and activation diameters from hygroscopicity data - Part I
T2 - Theory and application to inorganic salts
AU - Kreidenweis, S. M.
AU - Koehler, K.
AU - DeMott, P. J.
AU - Prenni, A. J.
AU - Carrico, C.
AU - Ervens, B.
PY - 2005
Y1 - 2005
N2 - A method is described that uses particle hygroscopicity measurements, made with a humidified tandem differential mobility analyzer (HTDMA), to determine solution water activity as a function of composition. The use of derived water activity data in computations determining the ability of aerosols to serve as cloud condensation nuclei (CCN) is explored. Results for sodium chloride and ammonium sulfate are shown in Part I. The methodology yields solution water activities and critical dry diameters for ammonium sulfate and sodium chloride in good agreement with previously published data. The approach avoids the assumptions required for application of simplified and modified Köhler equations to predict CCN activity, most importantly, knowledge of the molecular weight and the degree of dissociation of the soluble species. Predictions of the dependence of water activity on the mass fraction of aerosol species are sensitive to the assumed dry density, but predicted critical dry diameters are not.
AB - A method is described that uses particle hygroscopicity measurements, made with a humidified tandem differential mobility analyzer (HTDMA), to determine solution water activity as a function of composition. The use of derived water activity data in computations determining the ability of aerosols to serve as cloud condensation nuclei (CCN) is explored. Results for sodium chloride and ammonium sulfate are shown in Part I. The methodology yields solution water activities and critical dry diameters for ammonium sulfate and sodium chloride in good agreement with previously published data. The approach avoids the assumptions required for application of simplified and modified Köhler equations to predict CCN activity, most importantly, knowledge of the molecular weight and the degree of dissociation of the soluble species. Predictions of the dependence of water activity on the mass fraction of aerosol species are sensitive to the assumed dry density, but predicted critical dry diameters are not.
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U2 - 10.5194/acp-5-1357-2005
DO - 10.5194/acp-5-1357-2005
M3 - Article
AN - SCOPUS:21244466265
SN - 1680-7316
VL - 5
SP - 1357
EP - 1370
JO - Atmospheric Chemistry and Physics
JF - Atmospheric Chemistry and Physics
IS - 5
ER -