Abstract View
Dynamic Mixing State Effects on the Hygroscopicity of Ammonium Sulfate – Water Soluble Organic Compound Mixtures
PATRICIA RAZAFINDRAMBININA, Kotiba A. Malek, Kristin DiMonte, Tim Raymond, Dabrina Dutcher, Miriam Freedman, Akua Asa-Awuku, University of Maryland
Abstract Number: 6
Working Group: Aerosols, Clouds and Climate
Abstract
In the atmosphere, hygroscopic aerosol particles can uptake water and form clouds that will in turn reflect or absorb solar radiation, indirectly affecting the Earth’s climate and net radiative forcing. Submicron organic species compose ~50% of tropospheric aerosol particles by mass, which includes a subset of water-soluble organic compounds (WSOC) that are known to readily mix with ammonium sulfate. However, knowledge of the mixing state and its effect on hygroscopicity is limited. In this research, internal and external mixtures of ammonium sulfate with sucrose, levoglucosan, and adipic acid were able to be produced, and a laminar flow mixing tube facilitated the mixing state evolution of the mixtures. A cloud condensation nuclei counter (CCNC) and a humidified tandem differential mobility analyzer (H-TDMA) measured the water uptake of mixtures at subsaturated and supersaturated conditions. Here, we present the changes in experimental water uptake and cloud condensation nuclei activity with mixing states as a single hygroscopicity parameter (κ), and compare it to a predicted value derived from the Zdanovskii-Stokes-Robinson (ZSR) model. This work shows the complexity of binary internal and external mixtures and results imply that: (1) Organic-inorganic mixtures can produce non-ideal solutions that modify droplet solution. (2) Mixing state can be observed and defined by a function of the organic-inorganic composition ratio, which can aid the improvement of global climate models.