HR: 1340h
AN: A13B-1178    [Abstracts]
TI: Mass flux and ionic composition of foam droplets generated from natural and artificial seawaters
AU: * Allen, J O
EM: joallen@asu.edu
AF: Arizona State University, Department of Chemical Engineering, PO Box 876006, Tempe, AZ 85287-6006, United States
AU: * Allen, J O
EM: joallen@asu.edu
AF: Arizona State University, Department of Civil and Environmental Engineering, Tempe, AZ 85287, United States
AU: Tyree, C A
EM: ctyree@asu.edu
AF: Arizona State University, Department of Chemical Engineering, PO Box 876006, Tempe, AZ 85287-6006, United States
AB: In the remote marine boundary layer (MBL), sea salt aerosol (SSA) particles are an abundant and climatologically important class of particles. Wind stress on the ocean surface produces whitecap foams, which are the main source of SSA particles. Laboratory foams designed to mimic oceanic whitecaps were generated using a range of bubbling flow rates and aqueous media: unfiltered seawater, filtered seawater, artificial seawater, and mixtures of filtered and artificial seawater. We have reported on the fluxes of submicron particles by number; here we report mass and composition of sub- and supermicron SSA. Foam droplets were conditioned to 80% relative humidity and collected using a microorifice impactor. These substrates were analyzed by ion chromatography and atomic absorption spectroscopy. Sufficient aerosol matter was collected to accurately characterized mass distributions in the diameter range D_a,80 = 0.56 - 5.6 μm. The ionic composition of seawater was conserved during the foam bubble bursting process. Enrichment factors (EF) calculated relative to Na⁺ for Cl^-, SO^2-₄, Mg²⁺, Ca²⁺, and K⁺ were all indistinguishable from 1 with a precision of approximately 20%. The mass flux of submicron SSA was consistent with our earlier measurement of number flux. The mass flux of supermicron SSA (D_a,80 = 1.0 - 5.6 μm) was comparable to that for the submicron particles. In contrast to submicron SSA, which was approximately unaffected by the aqueous media composition, supermicon SSA mean diameters and fluxes varied with aqueous media composition. Filtered and unfiltered natural seawater exhibited a distinct peak in the range D_a,80 = 1.8 - 2.5 μm. The present results support the hypothesis that seawater organic matter affects the mass and size of supermicron SSA particles.
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0312 Air/sea constituent fluxes (3339, 4504)
DE: 0330 Geochemical cycles (1030)
DE: 3339 Ocean/atmosphere interactions (0312, 4504)
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting