Photoréactivité de la métamitrone et mécanisme de photosensibilisation par le mélange riboflavine/substances humiques

Abstract

The photodeamination of the herbicide metamitron (M T) was studied in pure water by irradiation with continuous and pulsed light. This study leads to understand the mechanism of this photochemical reaction and to demonstrate the formation of nitrous acid and desaminometamitron (DAM) as main product. Two origi nal transients resulting from the photolysis of MT and leading to deamination were de tected and characterized. We also studied the influence of humic substances ( HS) from various sources (humic and fulvic acids, soil or peat) on the degradation of t rimethylphenol (TMP) photosensitized by riboflavin (Ri). Humic acids (HA) have a prooxidant effect on the phototransformation for low concentrations and antioxidant for high ones. A reactional mechanism was proposed in both cases. Fulvic acids (FA) have almost no effect