Stephen Kelly, Lawrence Berkeley National Laboratory
Atmospheric aerosols are responsible for the largest portion of uncertainty in current state-of-the-art climate models. Chemical and structural inhomogeneities in these nanometer to micrometer sized particles strongly influence how atmospheric aerosols interact with light and water vapor in the atmosphere and ultimately contribute to climactic heating or cooling. Furthermore, these inhomogeneities are altered by reactions with water vapor as the aerosols traverse through areas of high and low relative humidity in the atmosphere. We have used scanning transmission x-ray microscopy (STXM) to characterize changes in chemistry and microstructure for two types of aerosols. First, we see evidence for the preferential removal of chlorine in mixed NaCl/organic acid particles as the particles cycle between high and low relative humidities. Second, we have identified the phases in mixed organic/inorganic particles that exhibit a liquid-liquid phase separation at elevated relative humidities using in situ STXM measurements. These measurements add to the understanding of atmospheric aerosol processing and help to narrow the uncertainty in how these particles contribute to the global climate.
