PHOTOLYSIS OF AQUEOUS CHLORINE AT SUNLIGHT AND ULTRAVIOLET WAVELENGTHS .2. HYDROXYL RADICAL PRODUCTION

The number of reactive free radicals (OH and Cl) produced per molecule of photolytically degraded aqueous chlorine was determined by following the degradation rate of added organic trace compounds which respond to OH and Cl radicals but that are resistant both to direct photolysis and to chlorine in the dark. Yields of OH production varied strongly with pH and slightly with the wavelength of irradiation. OCl- yielded 0.1 OH (pH > 8), both at sunlight wavelengths and at 255 nm. HOCl (pH 5) yielded 0.7 OH at sunlight wavelengths and 0.9 OH at 255 nm. The OH radical produced would oxidize any organic compound present following well-established competition kinetics. Sunlight photodegradation of chlorine decreased chloroform formation in filtered lake water due to destruction of the chlorine residual.