PHOTOLYSIS OF SMOKE DYES ON SOILS

Photolysis of an azo, a quinophthalone, and several anthraquinone smok e dyes was studied on soil surfaces. Initially, rapid photodegradation of each dye occurred, followed by a period of much slower rate of los s, indicating that the remaining fraction of the dye was photochemical ly protected. The average mean depths of photolysis ranged from 0.33 t o 0.68 mm for outdoor studies and from 0.42 to 0.73 mm for lab studies . The magnitude of the mean depths of photolysis suggests that photode gradation of the dyes occurs through indirect photochemical processes. Photolysis products for only two of the dyes could be identified. Pho tolysis of Disperse Red 9 resulted in the formation of 1-aminoanthraqu inone, whereas Solvent Yellow 33 photodegraded to give 2-carboxyquinol ine and phthalic anhydride. Reaction mechanisms involving sensitized p hoto-oxidation by singlet oxygen are consistent with the formation of these reaction products.