Studies On Photostabilization Of Trifluralin On Solid Media Surfaces

High pressure mercury lamp(L-IPML),xenon and sunlight were used as light sources in the present experiment. Photolytic kinetics of trifluralin(TF)on silica gel, quartz sand and bentonite surfaces,and the effects of some combined pesticides, surfactants, dyes and metal ions on photostability of TF on the adsorbents were studied. Then, the photostabilization mechanism and bioactivity of TF in the state of adsorption were further investigated. The main results were summarized as following I .Photolytic kinetics of TF on four kinds of adsorbents were studied under 1-IPMIL .The result manifested that photostability of TF was affected by different solid media surfaces. The half lives of TF adsorbed on glass, silica gel, quartz sand and bentonite were 24.78 minutes,98.51 minutes,106.41 minutes and 220.42 minutes respectively. The photostabilization of TF adsorbed on bentonite was most obvious. 2.Some combined pesticides and surfactants could alter the photolytic rate of TF on silica gel under sunlight When mixed with pyrethroids or butachlor in the ratio of 1: I,the photolytic rate of TF increased. When the dosage ratio of pyrethroids or butachlor and IF was 10: 1,the half-life of TF was put off. But when the ratio was 1 :5,some of them could accelerate the photodecomposition of TF while others retarded the photodegradation of TF. Auethrin could make TF degrade slowly on quartz sand and the half-life of TF co-existing with auethtin was as 1 .64 times as that of IF alone. Besides, fenvalerate could strengthen the photostability of IF adsorbed on bentonite. After 18 hours of irradiation, the photolytic rate of TF alone was 27.05% while the rate of TF combined with fenvalerate was only 5.4 1%.Effects of eight kinds of surfactants on the photolysis of TF was also evaluated. SDS was demonstrated as a photosensitizer, while ABS displayed remarkably photoquenching effect and the half-life of TF in the latter treatment was as 35.79 times as that of TF alone. Some surfactants could increase the photostability of TF adsorbed on bentonite. 111 The effects of CPC on the photostabilization of TF was observed significantly. The half-life of IF was prolonged 6.27 times. 3. Effect of several dyes on the photostabilization of TF on silica gel was also studied. Alt of them could delay the photolysis of IF under sunlight, while the effects of crystal violet and viboflavin were especially obvious and the half lives of IF in these treatments were prolonged as 14.64 times and 4.25 times as that of IF alone respectively. The photodegradation of IF adsorbed on quartz sand and bentonite was also affected by the above dyes. In addition, cationic ion of iron could postpone the photodegradation of IF adsorbed on silica gel, quartz sand and bentonite. 4. While crystal violet (CV) existed, IF adsorbed on bentonite could be photo- stabilized significantly. The remaining of IF alone was only 12.10% after 14 hours of irradiation alone on bentonite under HPMIL. But on B-CV complexes, the remaining of IF were 58.25%, 52.14% and 48.3 5%, corresponding to different equilibrium concentration of CV, that is 0.1mM, 0.2mM and 0.4mM respectively. The result demonstrated that although CV could enchance the photostabilization of IF ,different concentration displayed different effects on the photostability of IF. The better outcome was observed while the equilibrium concentration of CV was 0.1mM. Therefore, explanation about the...