HR: 0800h
AN: A31A-0801    [Abstracts]
TI: Chemical Composition of Laboratory Generated Seafoam Particles
AU: * Tyree, C A
EM: corey.tyree@asu.edu
AF: Arizona State University, Chemical & Materials Engineering PO Box 876006, Tempe, AZ 85287-6006 United States
AU: Alexandrova, O A
EM: olga.alexandrova@asu.edu
AF: Arizona State University, Chemical & Materials Engineering PO Box 876006, Tempe, AZ 85287-6006 United States
AU: Allen, J O
EM: joallen@asu.edu
AF: Arizona State University, Chemical & Materials Engineering PO Box 876006, Tempe, AZ 85287-6006 United States
AB: Remote marine aerosols include a significant number of sea-salt particles that may be effective cloud condensation nuclei. For example, O`Dowd and Smith (1993) found that remote marine aerosols in the particle size range 0.1-3.0 μm were dominated by sea-salt particles in the case of moderate-to-high wind speeds. Measurements of the flux of sub-micron sea-salt particles for the same wind speed vary by orders of magnitude, which indicate that other parameters, for example, may have a role in their production (Reid et al., 2001). Previous laboratory experiments using artificial seawater have shown that organic content (Garrett, 1968) and salinity (M†rtensson et al., 2003) affect sea-salt particle production. We present laboratory measurements of sea-salt particles generated from seawater foams and compare them to measurements of remote marine particles. Foam droplets were generated by bubbling air through a fine pore diffuser into aqueous media in a precleaned glass column. The effect of salinity was studied by varying the salinity of artificial seawater over the range 0-3.5%. The effect of organic content was also studied by diluting filtered seawater with artificial seawater. Size distributions of dried seafoam droplets were measured using a scanning mobility particle sizer. Seafoam particles were also size segregated and collected using a Micro-Orifice Uniform Deposit Impactor. Collected material was analyzed for sodium, chloride, sulfate, and dissolved organic carbon (DOC). Sub-micron particle size distributions were unimodal with a mean diameter of ~100 nm in agreement with recent seafoam laboratory experiments (Martensson et al., 2003). This mode is comparable to the "accumulation" mode particles typical of the remote marine environment and known to contain significant amounts of sea-salt (Bates et al., 1998). The size and number of seafoam particles were dependent on salinity; mean droplet size and total number concentration increased with salinity. Surprisingly, the size and number of seafoam particles was independent of organic content; this is in contrast to previous laboratory experiments that showed seafoam particle numbers were enhanced when surface-active organics were added to artificial seawater (Garrett, 1968). We present recent measurements of the composition and enrichment of laboratory seafoam particles, which we propose approximate remote marine boundary layer particles.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 3339 Ocean/atmosphere interactions (0312, 4504)
DE: 4504 Air/sea interactions (0312, 3339)
DE: 4801 Aerosols (0305, 4906)
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005