Identification of Photoctalytic Degradation Pathways of 2-Cl-s-Triazine Herbicides and Detection of Their Decomposition Intermediates

The photocatalyticdegradation of three 2-chloro-s-triazineherbicides (simazine, propazine, atrazine) over TiO2 particles under simulated solar light has been investigated. In the early steps, the degradation progresses through competitive reactions such as oxidation of the side alkyl chain and substitution of chlorine with hydroxyl groups, the last process occurring for less than 10% of degradation. Further oxidative processes give rise to the formation of dealkylated products. Several intermediates have been detected by GC-MS and comprehensive degradation schemes are proposed. The three herbicides, bearing different alkyl groups, exhibit relevant differences in the relative role of the competitive degradationpathways.