ABIOTIC DEGRADATION OF HALOBENZONITRILES - INVESTIGATION OF THE PHOTOLYSIS IN SOLUTION

This paper presents first experiments of laboratory investigations of the photodegradation by direct photolysis (lambda > 290 nm) of choloro tahlonil, dichlobenil, chloroxynil, bromoxynil, and ioxynil in aqueous , pH-buffered, and organic solutions and the calculation of the quantu m yields. The photolysis of chlorothalonil in water is low, with a cor responding low quantum yield (Phi = 0.0001). Dichlobenil is photostabl e under the laboratory conditions used. The photoreactivity of bromoxy nil and ioxynil was found to be comparable in aqueous solutions and ab out three times lower with respect to chloroxynil. The quantum yields obtained in water of chloroxynil, bromoxynil, and ioxynil are Phi = 0. 0060, 0.0093, and 0.0034, respectively. Half-lives of the pesticides i n the environment with respect to direct irradiation are estimated usi ng UV spectra and quantum yields as input variables obtained in the la boratory. (C) 1998 Academic Press