Surfactants in atmospheric aerosols.

The concentration and characteristics of anionic and cationic aerosol surfactants at a range of locations were determined as methylene blue active substances (MBAS) and ethyl violet active substances (EVAS) for anionic surfactants and as disulfine blue active substances (DBAS) for the cationic surfactants. Results showed that the anionic surfactants (in the pmol m(-3) range) dominated the concentration of surfactant in atmospheric aerosols. The concentration of both MBAS and EVAS is typically higher on the finer aerosol fractions. Further study on the aerosols found both MBAS and EVAS had the ability to reduce the surface tension of aqueous extracts of the aerosol. MBAS were more readily destroyed on exposure to a high intensity of UV light than were EVAS. The source of these seemingly ubiquitous compounds is not clear, but we note that anionic surfactants are easily derived from degraded or oxidized soots, especially that from diesel engines.