Studies On Photochemical Degradation Of Ethametsulfuron-methyl In Aqueous Solution

The direct photolysis of ethametsulfuron-methyl in aqueous solution irradiated by high pressure lamb light(HPML) and sunlight was investigated.The effects of different light sources, temperature,pH, halogen ions, metal ions, surfactants, different types of water, pigments , NO2-,NO3-,Fe3+,H2O2 and Fe3+:H2O2 on the photodegradation of ethametsulfuron-methyl in aqueous solution were studied. The main study results were summarized as follows:1. Under the room temperature, ethametsulfuron-methyl was very hard to be hydroliyed in different natural water.2. The photolysis rate of ethametsulfuron-methyl under HPML was easily degraded and the photolysis kinetics of ethametsulfuron-methyl in aqueous solution followed a first order reaction. The photodegradation half-life of Ethametsulfuron-methyl in aqueous solution under HPML was 23.05min and the photolysis rate of ethametsulfuron-methyl under sun and xenonlamp wasn't obvious degraded from six to eight hours.3. The photolysis rate of ethametsulfuron-methyl in four different types of water under HPML were found to increase by the order of distilled water >lake water (Chaohu lake)>cropland wanter>pond water. The photolysis kinetics of ethametsulfuron-methyl in aqueous solution followed a first order reaction.4. Under HMPL irradiation, photolysis rate constant of ethametsulfuron-methyl increased with water temperature.To take the photolysis rate constant at 20℃as 1.00, the photolysis rate constant at 30℃and 40℃were 1.05 and 1.25. The photolysis rate constant didn't increase when temperature was more than 40℃.5. Ethametsulfuron-methyl in acid conditions was easier to be photo-degradated, and in alkaline conditions, ethametsulfuron-methyl was hard to be photo-degradated.The photolysis rate of ethametsulfuron-methyl under different pH was: pH4>pH 7>pH 9.6. Surfactants emulsion 601#,emulsion 404#,emulsion 700# had adverse effects on the photolysis of ethametsulfuron-methyl. The adverse effects of emulsion 601# was obvious.The high condence of emulsion 601# had a strong adverse effects on the photolysis of ethametsulfuron-methyl. The photoquenching effect of ethametsulfuron-methyl raised as the concentration of emulsion 404# and emulsion 700# increased.7. Riboflavin had the photosensitivity effect on the photolysis of ethametsulfuron-methyl only when it concentration was on the low level.As the concentration of riboflavin increased, the photosensitivity turned into photoquenching effect.Crystal violet had the photoquenching effect on the photolysis of ethametsulfuron-methyl.8. Under HPML, The photolysis rate of ethametsulfuron-methyl was decreased by the increasement of NO2- and NO3-'s concentration. NO2- and NO3- had adverse effects on the photolysis of ethametsulfuron-methyl.9. Halogen ions had adverse effects on the photolysis of ethametsulfuron-methyl. As the concentration of I-,Br-,Cl- increased, the adverse effects were strengthened. the ability of the adverse effects of the three Halogen ions were:I->Br->Cl-.10.Under HPML ,different metallic ion had the photosensitivity or adverse effects on the photodegradation of ethametsulfuron-methyl. Mn2+,Zn2+,Fe2+ had the photosensitivity effect on the photolysis of ethametsulfuron-methyl and the effect was enhanced by the increase of the concentration. Cu2+ and Pb2+ had adverse effects on the photolysis of ethametsulfuron-methyl.11. Fe3+ had the photosensitivity effect on the photolysis of ethametsulfuron-methyl,and the photosensitivity effect was enhanced by the increase of the concentration of Fe3+. When the concentration of Fe3+ added to 25mg·L-1,the photodegradation half-life of ethametsulfuron-methyl falled from 19.74min down to 12.86min. H2O2 also had the photosensitivity effect on the photolysis of ethametsulfuron-methyl,and the photosensitivity effect was enhanced by the increase of the concentration of H2O2. When the concentration of H2O2 added to 25mg·L-1,the photodegradation half-life of ethametsulfuron-methyl falled from 20.21min down to 10.61min. The photosensitivity effect of Fe3+:H2O2 was more strengthend than the independent effect of Fe3+ and H2O2.