Mixing State of Submicrometer Sea Spray Particles Enriched by Insoluble Species in Bubble-Bursting Experiments

Abstract

Measurements of size distribution, hygroscopicity, and volatility of submicrometer sea spray particles produced by the bubble busting of artificial and natural seawater were conducted to determine their mixing state and volume fractions of hygroscopic and nonhygroscopic species or volatile and nonvolatile species. The particles sprayed from artificial seawater having insoluble silica particles were found to be an external mixture of two groups of particles having hygroscopic growth factors (HGFs) of 1.33 (an internal mixture of nonhygroscopic silica particles and hygroscopic salt species) and 1.68 (a similar mixture having more salt species) when the mass ratio of insoluble particles to dissolved salts was higher than 2. For sea spray particles from natural seawater, the external mixing was not significantly observed because of a high concentration of dissolved salts. The HGFs of sea spray particles (80-140 nm) from natural seawater were in the range of 1.70-1.76, which were lower than from pure artificial seawater (1.87), and the HGFs had no change before and after membrane filtration of seawater, suggesting that the sea spray particles from natural seawater contained a significant amount of nonhygroscopic dissolved organic matter in addition to hygroscopic salt species. The volume fraction of the nonhygroscopic species ranged from 20% to 29%, and the highest value was observed for seawater samples from the site where strong biological activity occurred, suggesting that biological materials played an important role in the formation of nonhygroscopic organic matter. Volatility measurements also identified the existence of volatile organic species in single particles from natural seawater, with the volume fraction of volatile species evaporated at 1008C being 4%-5%.

Direct aerosol chemical composition measurements to evaluate the physicochemical differences between controlled sea spray aerosol generation schemes

“…This method of enriching the seawater with organic matter allows for natural dynamic ecosystem processes to shape the composition of the organic matter in the seawater, similar to the types of interactions found in natural phytoplankton blooms (Azam and Malfatti, 2007;Pomeroy et al, 2007;Teeling et al, 2012). While the total chlorophyll a concentration in these experiments is an indirect indicator of the autotrophic biomass, it is notable that various controlled SSA generation studies have shown that the amount of organic matter imparted to SSA is only a weak function of the seawater chlorophyll concentration, and depends instead on the amount and composition of organic matter in the seawater Collins et al, 2013;Prather et al, 2013;Park et al, 2014;Quinn et al, 2014). Total organic carbon (TOC) concentrations in the seawater were measured by means of the high temperature combustion method (Shimadzu Scientific Instruments) after acidifying the sample with 12N hydrochloric acid.…”

“…These studies produce SSA from disintegrating foam in natural seawater or proxy materials mainly by means of sintered glass bubblers or plunging water jets. (Sellegri et al, 2006;Keene et al, 2007;Tyree et al, 2007;Fuentes et al, 2010b;Hultin et al, 2010;Bates et al, 2012;Park et al, 2014). Since it is well known that SSA is produced by the bursting of air bubbles at the sea surface (e.g., Blanchard and Woodcock, 1957;Lewis and Schwartz, 2004;de Leeuw et al, 2011), the differences between generation methods for SSA in the laboratory differ primarily by the method of bubble production.…”

“…Recent reports indicate that pneumatic atomization does not produce particles of similar physical or chemical properties to those generated by bubble bursting (Fuentes et al, 2010b;Gaston et al, 2011). Until recently, two different bubble production techniques have been utilized for laboratory studies of aerosol composition: (1) air (or N 2 ) forced through sintered glass filters ("frits") (Cloke et al, 1991;Keene et al, 2007;Wise et al, 2009;Fuentes et al, 2010b;Modini et al, 2010;Park et al, 2014), and (2) impinging water jets (Facchini et al, 2008;Fuentes et al, 2010b;Hultin et al, 2010). A new approach introduced by produces SSA using reproducible breaking waves in a linear wave channel filled with natural, filtered seawater.…”

Biological Impacts on Carbon Speciation and Morphology of Sea Spray Aerosol

“…Although the transfer of insoluble species has been examined in the past, 48 concentration and emission of graphitic carbon from the SSML is a unique observation with implications for radiative transfer and carbon cycling between the ocean and the atmosphere.…”

Impact of anions on the surface organisation of lipid monolayers at the air–water interface

“…[15] Sea spray aerosol has been shown to comprise more than just sodium chloride; it contains other inorganic salts as well as biologically produced organic species. [16] While the majority of submicrometre SSA particles contain mostly sea salts (i.e. NaCl, KCl, MgCl 2 and CaCl 2 ), SSA particles contain increasing levels of organic species (relative to inorganic species) as particle diameter decreases to submicrometre sizes.…”