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.