OCEANFILMS‐2: Representing coadsorption of saccharides in marine films and potential impacts on modeled marine aerosol chemistry

Abstract

Here we show that the addition of chemical interactions between soluble monosaccharides and an insoluble lipid surfactant monolayer improves agreement of modeled sea spray chemistry with observed marine aerosol chemistry. In particular, the alkane:hydroxyl mass ratio in modeled sea spray organic matter is reduced from a median of 2.73 to a range of 0.41–0.69, reducing the discrepancy with previous Fourier transform infrared spectroscopy (FTIR) observations of clean marine aerosol (ratio: 0.24–0.38). The overall organic fraction of submicron sea spray also increases, allowing organic mass fractions in the range 0.5–0.7 for submicron sea spray particles over highly active phytoplankton blooms. Sum frequency generation experiments support the modeling approach by demonstrating that soluble monosaccharides can strongly adsorb to a lipid monolayer likely via Coulomb interactions under appropriate conditions. These laboratory findings motivate further research to determine the relevance of coadsorption mechanisms for real‐world, sea spray aerosol production.

The Impact of Divalent Cations on the Enrichment of Soluble Saccharides in Primary Sea Spray Aerosol

“…This mechanism is most relevant to saccharide compounds that readily ionize at ocean pH, which significantly decreases the scope of compounds that will participate. for the (A) macromolecule-derived mechanism, shown here as the lipid A head group of lipopolysaccharides (LPS), (B) ion-mediated co-adsorption mechanism put forth by Burrows et al [57] and (C) divalent cation mediated co-adsorption (this paper).…”

“…To account for this, a second model iteration [57] considered the possibility of ionic interactions between the insoluble and soluble organics, and a second layer of co-operatively adsorbed soluble saccharides was added to the original layer of insoluble organics in the model SSML ( Figure 1B). The addition of the co-adsorption mechanism increases model-derived SSA organic mass fractions [57], leading to better agreement with ambient observations. To assess the validity of this idea, a series of sum-frequency generation (SFG) experiments with dipalmitoylphosphatidylcholine (DPPC, pK a = 3.8 [58,59]) and glucosamine (pK a = 7.58 [60]) were conducted.…”

“…Atmosphere 2018, 9, x FOR PEER REVIEW 3 of 18 approach replicates the seasonal and geographic variability in aerosol organic mass, but routinely underestimates observations of organic mass fractions (OMF) over a wide range of chlorophyll concentrations [56]. To account for this, a second model iteration [57] considered the possibility of ionic interactions between the insoluble and soluble organics, and a second layer of co-operatively adsorbed soluble saccharides was added to the original layer of insoluble organics in the model SSML ( Figure 1B). The addition of the co-adsorption mechanism increases model-derived SSA organic mass fractions [57], leading to better agreement with ambient observations.…”

Web Strategy to Convey Marine Biogeochemical Feedback Concepts to the Policy Community: Aerosol and Sea Ice

“…The biopolymeric chemistry of organic surfactants is featured here. It is likely that antifreeze proteins (exudates) are exerting unexpected influence on brine-ice interface structure along with its freeze-melt thermochemistry [29]. Saccharide gels may divert or even block fluid flow through the internal channel structure.…”

“…Coloration noted inside the sea ice system necessarily implies the presence of detrital organic macromolecules in brine channels. These are likely to affect ice rheology and thermodynamics -proteins are known to function as antifreeze agents [29].…”