Surface Partitioning and Stability of Pure and Mixed Films of 8−2 Fluorotelomer Alcohol at the Air−Water Interface

Abstract

Fluorotelomer alcohols (FTOHs) have been suggested as possible precursors for perfluorinated carboxylic acids and have been detected in the troposphere over several North American sites. Although the gas-phase chemistry of several FTOHs has been extensively studied, the heterogeneous chemistry of these compounds has yet to be explored at the same depth. In this study, the surface activity of 8−2 FTOH at the air−water interface was investigated using a Langmuir trough. Isotherms of both the pure telomer alcohol and equimolar mixtures with stearic acid were collected. The objective of these experiments was to characterize the pure and mixed films and understand their heterogeneous chemistry, which can be used as a representative model for that of organic films on atmospheric surfaces, such as those found on oceans and aqueous aerosols. A consequence of FTOHs partitioning to the air−water interface is the possibility of their transport and widespread distribution and deposition using atmospheric aerosols. Our results indicate that 8−2 FTOH evaporates rapidly off the subphase surface in the pure samples, but when mixed with stearic acid, the evaporation rate is significantly reduced, indicating stabilization of the film. Atmospherically relevant consequences for 8−2 FTOH partitioning to the air−water interface are discussed in detail.