Heat-induced generation of hydroxyl radicals and other redox-active species in seawater

The process of heat-induced generation of hydroxyl radicals in seawater was studied using coumarin-3-carboxylic acid as a fluorescent detector of (OH)-O-.. The rate constants of (OH)-O-. thermo-production were determined in the temperature range of 40 to 60degreesC. The activation energy for thermal production of (OH)-O-. in seawater was 25 kcal/mol. It was found that this reaction is affected by (OH)-O-. scavengers, additional oxygenation of solution, catalase, and iron chelators. Deferoxa mine (desferal), an iron chelator used in therapy, enhanced the rate constant for this reaction many-fold. It was shown that heat-induced (OH)-O-. production in seawater at 28degreesC is about 1% of the (OH)-O-. photochemical production caused by maximal daytime irradiation with natural sunlight. The rate of (OH)-O-. thermoproduction at 28degreesC was three orders of magnitude greater than the average rate of (OH)-O-. production in water due to natural background radiation. The thermally induced generation of an unidentified reducing agent(s), in seawater was investigated by the use of Ellman's reagent. The kinetic parameters of the process were evaluated.