Photosensitized degradation of terbuthylazine in water

We investigated the photodegradation of terbuthylazine, an s-triazine herbicide, in the presence of hydrogen peroxide (H 2O 2), titanium dioxide (TiO 2), acetone or humic substances. In the presence of H 2O 2 and UV light, the degradation of terbuthylazine quickly leads to the formation of ammeline. The degradation pathway consists of dealkylation reactions giving 2-chloro-4,6-diamino-1,3,5-triazine, and then ammeline through hydroxylation. Irradiation of terbuthylazine with simulated solar light in the presence of titanium dioxide gives also dealkylation products in the first stage of degradation. Acetone at ∗1 % (v/v) produces a 7-fold enhancement of the degradation rate. In the presence of humic substances, different results were obtained, depending on the origin of the substances tested. The humic acids isolated from a soil accelerate the degradation speed, whereas the fulvic acids from a small stream reduce it.