Photodegradation of Irgarol 1051 in water

The photodegradation of a novel antifouling agent with high algicidal activity, Irgarol 1051 (2-methylthio-4-tert-butylamino-6-cyclopropylamino-s-triazine), has been investigated. Irgarol 1051 is fairly stable toward hydrolysis in water, and has been detected in European coastal and lake waters since its introduction in the late 1980's. Irgarol 1051 dissolved in six different aqueous solutions was exposed to solar irradiation for 6 months. Its rates of photodegradation in natural sea water and river water were much higher than those in pure water and buffered solutions (pH 5, 7, and 9). It appears that unknown photosensitizers in the natural waters accelerated the photodegradation of Irgarol 1051. Three significant photodegradation products ("RT5.8", "RT7.8", and "RT8.7") were observed. The degradation product RT7.8 was produced just in the natural waters and persisted for only several weeks. The other two degradation products (RT5.8 and RT8.7) were much more stable, even after 6 months irradiation. The latter (RT8.7) was produced mainly in buffer solutions, and the former (RT5.8) was produced in all the 6 aqueous solutions tested and was identified by GC-MS analysis as the compound 2-methylthio-4-tert-butylamino-6-amino-s-triazine, which had been found as a biodegradation product during the fungal biotransformation of Irgarol 1051. Thus biodegradation and photodegradation processes in natural waters both have the same major degradation product.