Photochemical Reactions in Sunlit Surface Waters

Abstract

Photochem. processes are important pathways for the transformation of biol. refractory org. compds., including harmful pollutants, in surface waters. They include the direct photolysis of sunlight-absorbing mols., the transformation photosensitized by the triplet states of chromophoric dissolved org. matter (CDOM), and the reaction with photochem. generated radical transients. Differently from the direct photolysis, the other processes (often indicated as indirect photochem.) can also induce the phototransformation of compds. that do not absorb sunlight. The excited triplet states of CDOM, 3CDOM*, play a very important role in surface-water photoprocesses, both directly and as sources of singlet oxygen (1O2). The most important reactive radical species in surface waters are the hydroxyl radical .bul.OH, the carbonate radical CO3 -.bul. , and various peroxy radicals that can be produced upon degrdn. of dissolved org. matter (DOM), either chromophoric or not. Further radical species such as .bul.NO2, Cl2-.bul. and Br2-.bul. can be involved in the generation of harmful degrdn. intermediates such as arom. nitro, chloro, and bromoderivatives. [on SciFinder(R)]