Phytotransformation of benzotriazoles.

Plant roots interact with organic pollutants and some of these contaminants can be phytotransformed. Root uptake of 1-H-benzotriazole and its derivatives, tolyltriazole, 5-methyl benzotriazole, and 1-hydroxy benzotriazole was studied. At levels below the toxic threshold of about 100 mg/L, triazoles appear to be incorporated into plant tissue. Their concentration in the aqueous phase of the culture decreases with time and they cannot be extracted from the plant material using methanol. Hydroponic studies with sunflowers (Helianthus annuus) were used to investigate the behavior of the solution concentration versus time and to determine kinetic parameters for plant uptake of triazoles. Plants actively take up the triazoles at a rate greater than predicted by transpiration stream-concentration factor and plant-water uptake. Analyses of the data for phytotransformation rate versus concentration were performed to establish the kinetic model for the removal process. Except for 1-hydroxy-benzotriazole, triazole disappearance in plant systems followed the Michaelis-Menten kinetic model (commonly found for enzyme-catalyzed reactions) better than a first order rate model. However, the fit for the first order model was improved when normalizing to the plant fresh weight, which was assumed to be an approximate measure of the changing root surface area. Experiments with other plant species are in progress.