Abstract View
Size-dependent Impacts of Atmospheric Oxidation on Ice Nucleating Particles from Sea Spray Emissions
PAUL DEMOTT, Thomas Hill, Kathryn Moore, Russell Perkins, Josephine Rudd, Liora Mael, Chathuri Kaluarachchi, Hansol Lee, Kathryn Mayer, Alexei Tivanski, Vicki Grassian, Kimberly Prather, Colorado State University
Abstract Number: 588
Working Group: Aerosols, Clouds and Climate
Abstract
Certain particles emitted as sea spray from bubble bursting act as ice nucleating particles (INPs) via containing ice nucleation active entities as molecular components. The ocean thereby provides a source for glaciating marine supercooled clouds. Many factors impact the atmospheric lifetime of marine INPs. One factor not previously evaluated is the impact of photochemical aging. We have explored the potential for this via measurements made using wave flume production of sea spray aerosols, an oxidation flow reactor for exposing particles to atmospheric oxidation by hydroxyl radicals, two INP measurement methods, and morphological and compositional analyses of collected singe INPs. Immersion freezing ability was determined from -10 to -28ºC through droplet freezing assays of filter-collected aerosols (PM10), and at -30ºC for single INPs at PM1.5 sizes using a continuous flow diffusion chamber (CFDC). Single INPs from the CFDC were collected for analysis (and refreezing) in cold stage Atomic Force Microscopy and Raman spectroscopy systems, and for transmission electron microscopy analysis.
Any amount of aging (0.5 to 5 days equivalent) by hydroxyls led to decreases in INP concentrations by up to 50 times at a single temperature. This effect varied over the course of a laboratory phytoplankton bloom, and PM10 INPs, that dominated nascent INP emissions, suffered roughly an order of magnitude higher loss of ice nucleation activity than did PM1.5 INPs. Morphological and compositional data indicated that periods with the least oxidation impact at submicron sizes were periods dominated by organic/inorganic particles other than core-shell sea salt/organics. Alternately, core-shell particles were most associated with destruction of INPs by oxidation. Results imply a constant competition between production and destruction of marine INPs over oceans, and the size-dependent and chemical nature of this process requires elaborated study in order to be accounted for in atmospheric modeling.