Hygroscopicity and cloud condensation nucleation activities of hydroxyalkylsulfonates

Hydroxyalkylsulfonates may contribute significantly to atmospheric particles; however, their hygroscopic properties and cloud condensation nuclei (CCN) activities remain unknown. In this study, three complementary techniques were utilized to examine the hygroscopicity of sodium hydroxymethanesulfonate (NaHMS), sodium 2-hydroxyethylsulfonate (NaHES), and ammonium 2-hydroxyethylsulfonate (NH4HES) under subsaturated and supersaturated environments. The mass changes in the three hydroxyalkylsulfonates at different relative humidities at 25 degrees C were examined by a vapor sorption analyzer, and the mass growth factors were measured to be 3.25 +/- 0.01 for NaHMS, 3.32 +/- 0.02 for NaHES, and 3.34 +/- 0.04 for NH4HES at 90% RH. Their hygroscopic growth was investigated by a humidity tandem differential mobility analyzer, and hygroscopic growth factors were 1.78 +/- 0.02 for NaHMS, 1.71 +/- 0.02 for NaHES, and 1.68 +/- 0.03 for NH4HES at 90% RH. Furthermore, the CCN activities of NaHMS, NaHES, and NH4HES were explored, and their single hygroscopicity parameters (kappa(ccn)) were measured to be 0.649 +/- 0.097 for NaHMS, 0.559 +/- 0.069 for NaHES, and 0.434 +/- 0.073 for NH4HES. In addition, the hygroscopic growth and CCN activities of binary mixtures of ammonium sulfate with one of the three hydroxyalkylsulfonates were also examined.