Dissolved organic matter (DOM) produced by marine biota partitions to the uppermost surface of the ocean, known as the sea surface microlayer (SSML), where DOM is transferred to sea spray aerosol (SSA) upon wave breaking. Although sugars are generally regarded as water soluble and surface-inactive, it is hypothesized that marine carbohydrates cooperatively adsorb to other surface-active material to yield sugar enrichment in the SSML and in SSA. We are examining interfacial morphology and molecular organization of SSML proxy films to better understand saccharide transfer to SSA. Alginate served as a marine-relevant model polysaccharide that readily gels in the presence of calcium cations. Palmitic acid was spread into a monolayer at the air-water interface of alginate and artificial seawater solutions. Surface tensiometry measurements revealed that surface tension decreases upon addition of alginate to the subphase, suggesting that alginate gels are surface-active. Infrared reflection-absorption spectroscopy probed alginate surface activity and palmitic acid molecular organization via functional group vibrational signatures, indicating that alginate adsorbs and intercalates into the monolayer. Further spectroscopic investigation is underway to better characterize the interfacial molecular organization. Lastly, Brewster angle microscopy visualized changes in palmitic acid monolayer domain morphology after introducing alginate to the underlying subphase. In the future, physical properties of the laboratory SSML proxy film will be compared to SSML samples collected on field campaigns.

Interfacial characterization of polysaccharide enrichment in sea surface microlayer proxy films

2019 Fall National Meeting

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