Experimental Examination of the Ammonium Nitrate/Ammonium Sulfate/Water Phase Diagram: Implications for Cirrus Cloud Formation
Abstract
Aqueous atmospheric aerosols in the troposphere are known to contain ammonium, nitrate, and sulfate ions in varying ratios. Thus, the physical chemistry of the ternary ammonium nitrate/ammonium sulfate/water system must be studied to further understand tropospheric aerosols, aerosol chemistry, and cirrus cloud formation mechanisms. We have studied the thermodynamic properties of the ammonium nitrate/ ammonium sulfate/water system using differential scanning calorimetry and infrared spectroscopy of thin films at low temperatures. This is the first study focused on low temperatures, as previous experimental work on this system has been above 273 K. We have combined our experimental results with historical melting point data at high temperatures to create a liquid/solid phase diagram of the ammonium nitrate/ammonium sulfate/water system for temperatures below 343 K. Using phase diagram theory and alkemade lines, we predict which solids are stable at equilibrium for all concentrations within the studied region. Finally we have compared our predicted solids and final melting temperatures to the Aerosol Inorganics Model (AIM).
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2006
- Bibcode:
- 2006AGUFM.A33A0971B
- Keywords:
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- 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0305 Aerosols and particles (0345;
- 4801;
- 4906);
- 0320 Cloud physics and chemistry