The thermodynamic properties of aqueous systems that constitute aerosol particles in the mid and upper troposphere will be investigated. Because, depending on their phase, these aerosols may be involved in cirrus cloud formation and contribute to earth's radiation balance, their phase diagrams and relative humidity/solute concentration relationships will be studied. Temperature-dependent deliquescence relative humidity (DRH) and concentration/activity relationships will be measured using humidity-controlled thermogravimetric analysis (HTGA) for several aqueous dicarboxylic acids in the range 303 - 253 K: malonic (C3H4O4), oxalic (C2H2O4), succinic (C4H6O4), maleic (C4H4O4), malic (C4H6O5), and glutaric (C5H8O4). Low temperature liquid/solid equilibrium phase diagrams will also be investigated. Enthalpies of transition, the temperature-dependent DRH, and concentration/activity relationships will be measured using differential scanning calorimetry (DSC), infrared spectroscopy of thin films, and HTGA for ternary systems of dicarboxylic acids, ammonium sulfate, and water.
The results of this research will be used to validate and constrain atmospheric aerosol models. Undergraduate students will be extensively involved in laboratory experimental work, data analysis, and communication of results. A new research grade humidity-controlled thermogravimetric analyzer (HTGA) will be purchased, which will enhance the research and teaching infrastructure at the grantee institution. Students will gain extensive experience with FTIR and DSC instruments as well as the HTGA.
