Singlet oxygen in surface waters. 3. Photochemical formation and steady-state concentrations in various types of waters

Abstract

For prediction of the rate with which organic compounds are oxidized and photoproducts formed in the aquatic environment by the 1O2 route, the steady-state concentrations of 1O2 in various waters were determined by using furfuryl alcohol as a trapping agent. Under noon, summer sunlight (Switzerland) in lake, river, and wastewaters, surface concentrations were (0.3-3) x 10-14 M 1O2 per mg of DOC/L. The more highly colored waters actually tend to produce less 1O2 for a given amount of adsorbed light. Separation of natural aquatic organic compounds by gel permeation chromatography resulted in fractions showing little correlation between 1O2 production efficiency and molecular weight, indicating that large macromolecular structures are not a prerequisite for the sensitization of 1O2 formation. Application of the specific 1O2 concentration data to the estimation of lifetimes of environmental pollutants yields half-lives as short as several hours only for a few especially reactive types of compounds but orders of magnitude longer for most of the compounds expected to be found in the aquatic environment.