Trifluralin photolysis in natural waters and under the presence of isolated organic matter and nitrate ions: kinetics and photoproduct analysis

The aquatic photochemistry of trifluralin has been investigated under simulated solar irradiation (Suntest apparatus) in different types of natural waters (sea, river and lake water) as well as in distilled water. In order to examine the effect of dissolved organic matter (DOM), photodegradation of the tested herbicide was also examined under the presence of humic and fulvic acids isolated from Pamvotis Lake at various concentrations. The influence of nitrate ions on the degradation kinetics was also examined. It was found that photodegradation proceeds via a pseudo first-order reaction in all cases and that the presence of DOM inhibits the photolysis reaction whereas rate constants measured in the presence of NO3- ions indicated higher degradation efficiency. Kinetic experiments were monitored by GC-FTD with half-lives ranging from 7.22 to 50.58 min. In addition Microtox bioassay (vibrio fischeri) was employed in evaluating the ecotoxicity of irradiated solutions. The major photodecomposition products formed mainly through dealkylation, cyclization and reduction processes were isolated by means of solid phase extraction (SPE) and were identified by GGMS. Based upon this byproduct identification, a possible degradation pathway is proposed for the photolysis of trifluralin in aqueous media. (C) 2004 Elsevier B.V. All rights reserved.