AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Investigating Effects of Ambient Temperature on Hygroscopic Properties of Atmospheric Aerosol using ATR-IR
YONG LIU, Dong Fu, University of Colorado Denver
Abstract Number: 53 Working Group: Aerosols, Clouds, and Climate
Abstract Phase and hygroscopic properties of atmospheric particles affect global radiation budget and atmospheric composition by changing light scattering and absorption abilities and reactivity of aerosol. Temperature in the troposphere spans over a wide range from 217K in the tropopause to close to room temperature at sea level. At present, our knowledge about the role of ambient temperature in hygroscopic properties such as deliquescence, efflorescence, and hygroscopic growth of aerosol, especially water soluble organic salts, is still fairly limited. In the present work, we demonstrated feasibility of using an environmental cell coupled to an ATR-IR spectrometer to probe hygroscopic behavior of atmospheric aerosol and the temperature dependence. We selected several model aerosol samples of atmospheric importance (NaCl, NaNO3, and (NH4)2SO4) first to validate the approach. We determined values of deliquescence relative humidity (DRH) and efflorescence relative humidity (ERH) by integrating absorbance of H2O bands from infrared spectra as a function of RH. We also calculated water to solute ratios (WSR) and growth factors (GF) with the integrated absorbance values of H2O band and corresponding infrared active bands. We compared the results with our bulk water activity measurement and literature data and obtained an excellent agreement. This indicates that our approach is capable of acquiring reliable temperature dependent hygroscopic data. In this study, we also investigated temperature dependent hygroscopic property of CH3SO3Na, an important composition of chemically processed aerosol samples in marine boundary layer. In addition, our results showed that the ambient temperature in the troposphere could play an important role in hygroscopic properties of atmospheric aerosol, but it is largely dependent on the compositions.