Sunday, 22 January 2012
Morphology and Optical Properties of Sea Salt Aerosol
Hall E (New Orleans Convention Center )
The scattering of light due to the presence of aerosols tends to cause atmospheric cooling. Sea salt aerosol is the largest yearly emission by mass into the atmosphere. These aerosols are present above all oceans, and therefore cause a large-scale scattering of light that impacts the global climate. Aerosols cause atmospheric cooling, but the amount of cooling is still being quantified. Morphological differences in the structure of sea salt aerosol can cause changes in the scattering of light, which then have the potential to affect large-scale climate systems. The differences in the morphologies of mixtures of several sea salt aerosol components, including sodium chloride/sodium acetate (NaCl/NaOAc) and sodium chloride/sodium bromide (NaCl/NaBr), were examined in this study. Using a transmission electron microscope (TEM) equipped with energy dispersive x-ray spectroscopy (EDS) and Selected Area Electron Diffraction (SAED), the morphologies of each system were closely examined, and phase-separated structures were further examined using EDS. The extinction of certain particles could be measured using cavity ring-down aerosol extinction spectroscopy (CRD-AES). It was determined that NaCl/NaBr aerosol systems undergo phase separation at varying ratios, such as 25:75, 50:50, and 75:25 NaCl/NaBr. It was then determined with EDS that the system was phase separated into two distinct systems, each with their own morphology. The same tests were done on NaCl/NaOAc systems of the same ratios, but it still remains unclear whether or not any phase separation occurred. Thus, the purpose of this experiment was to examine the morphology and optical properties of the NaBr/NaCl phase-separated structures, as well as investigate the possibilities of other phase-separation relationships using CRD-AES and the TEM.