Enhanced uptake of PAHs by organic-coated aqueous surfaces

We report direct laser-induced fluorescence measurements of the uptake of the polycyclic aromatic hydrocarbons (PAHs) anthracene and pyrene to the air-aqueous interface for pure water and for water coated with an organic film. The surface uptake coefficients of anthracene and pyrene to the air-water interface are estimated to be on the order of 10(-5). For both PAHs, the surface uptake coefficients for uptake to a 1-octanol-coated water surface increase by a factor of 2-3 over those determined for the pure water surface. The surface uptake of pyrene to a hexanoic-acid-coated interface does not display this enhancement, though there is a small enhancement of its equilibrium partitioning to hexanoic-acid-coated surfaces. Resolved fluorescence spectra of pyrene adsorbed onto 1-octanol-coated surfaces indicate that pyrene is in a less polar environment there than when adsorbed at hexanoic-acid-coated interfaces.