Surfactants are organic molecules that have surface active properties that reduce the surface tension of solutions. Surfactants can be found in marine water systems and originate from both natural and anthropogenic sources. These compounds are characterized by having a hydrophilic head and a hydrophobic tail. This chemical structure causes surfactants to accumulate and orient themselves on the surface of the ocean in a microlayer of organic molecules. This layer influences the air-sea gas exchange and the compounds, including surfactants, which enters the atmosphere as primary marine aerosols through the bubble bursting process. The characterization and quantification of marine surfactants has been investigated through techniques such as tensiometry and colorimetry, however, the identities of marine surfactants have largely gone uncharacterized. In order to constrain the chemical characterization of these unknown surfactants, I developed a solid phase extraction to efficiently isolate surfactants from aqueous marine samples and analyze dissolved organic matter (DOM) using high resolution mass spectrometry1. This method was validated using analytical standards and then applied to DOM collected from the Delaware Bay to characterize the organic molecules present. The formulaic characterizations, based on the mass spectra, are supported by principal component analysis which showed sample differentiation based on the interfacial tension and presence of surfactants within the samples. This analysis shows strong tidal influences on the DOM composition within the Delaware Bay and produces data that can be compared to open ocean samples that are not influenced by tide and riverine inputs.
1. Burdette, T. C.; Frossard, A. A., Characterization of seawater and aerosol particle surfactants using solid phase extraction and mass spectrometry. J. Environ. Sci. 2021, 108, 164-174.