ISOLATION OF MARINE MICROLAYER FILM SURFACTANTS FOR EXSITU STUDY OF THEIR SURFACE PHYSICAL AND CHEMICAL-PROPERTIES

Surface-active organic matter from natural marine microlayers has been isolated by solid phase adsorption using reversed phase (C18) cartridges. Surfactants collected from a suite of microlayer films in the California Bight and the Gulf of Maine and isolated by this technique were respread on clean seawater to reconstitute surface films which exhibited surface pressure-area (pi-A) isotherms and static (Gibbs) surface elasticities closely approximating those measured for films formed by diffusion in the original fresh microlayer samples. Microlayer-subsurface (10 cm depth) carbon enrichment factors were estimated to range from 3.9 to 16. The estimated mean recovery of microlayer dissolved organic carbon (DOC) was 20 +/- 5%. The select hydrophobic DOC fraction isolated was the dominant surfactant class responsible for microlayer film characteristics as measured quasi-statically, even though other relatively hydrophilic DOC fractions which may have been enriched in the microlayer were not absorbed and passed through the isolation procedure. This technique allows collection of marine microlayer films for systematic ex situ study and correlation of their surface physical and chemical properties. For the first time, the pi-A isotherms for microlayer films can be expressed on a specific area basis and, in cases where molecular weights can be estimated, according to mean molecular area.