Abstract View
Direct Comparison of the Submicron Aerosol Hygroscopicity of Water-Soluble Sugars and Ammonium Sulfate-Organic Mixtures
PATRICIA RAZAFINDRAMBININA, Joseph Nelson Dawson, Kotiba A. Malek, Tim Raymond, Dabrina Dutcher, Akua Asa-Awuku, Miriam Freedman, University of Maryland
Abstract Number: 161
Working Group: Aerosols, Clouds and Climate
Abstract
Water-soluble organic compounds (WSOC) can exist in the atmosphere as aerosol particles. Both man-made and naturally occurring WSOC aerosol particles can readily uptake water and form droplets that can affect the particle’s overall effect on climate forcing. Understanding the water uptake ability of such particles is key to improving current climate models. In this study, we examine the validity and reliability of three water uptake measurement methods by investigating the hygroscopicity and cloud condensation nuclei (CCN) activity of four atmospherically relevant sugars: sucrose, levoglucosan, trehalose, and raffinose. In addition to small sugars, we present the water uptake of select WSOC as internal and external mixtures with ammonium sulfate at sub and supersaturated conditions. At subsaturated conditions, the optical growth factor (fRH) obtained from cavity ring-down spectroscopy measurements and the geometric growth factor (Gf) from humidified tandem differential mobility analyses was converted to the single parameter hygroscopicity, κ. κ allows subsaturated hygroscopic properties to be compared to supersaturated measurements made by the cloud condensation nuclei counter (CCNC), as measured critical activation diameters (dp50) can be directly converted into κ. Values reported in this work show that the single parameter hygroscopicity term for the selected WSOC is molecular weight dependent. κ-values obtained from the three methods were comparable in precision, with systematic deviations in the average mean for each method.