The Study Of Halosulfuron-methyl Hydrolysis And Photolysis Characteristics

Halosulfuron-methyl was a new kind Sulfonylurea herbicide found by Nissan Chemicaland Monsanto first. It was widely used to prevent and wipe out broadleaf weeds and sedge weedin wheat, corn, rice, sugar and other crops. Because of the high activity, selectivity and lowdosage of halosulfuron-methyl in field, it was popular in the market. Very few comprehensiveresearches on the behavior of halosulfuron-methyl in the environment has not been studied,although it is an efficient, harmfulless pesticide and it is applied widely. In order to correctlypredict oxyfluorfen environmental behaviors and correct evaluation of their environmentalsafety; We provided important scientific evidence for people to reasonable use of the pesticidesand reduce its adverse impact on environment and human health. We investigated the hydrolysisand photolysis of halosulfuron-methyl. The dynamics of halosulfuron-methyl hydrolysis andPhotolysis were studied in laboratory simulation experiments by HLPC-UV.Firstly we studied the hydrolysis behaviors of halosulfuron-methyl. The results showed that:In the pH buffer solution with4、7、9, the hydrolysis half lives were8.9d、14.6d、0.7d，it canbe seen that the hydrolysis rate of halosulfuron-methyl in the alkaline conditions was faster thanneutral and acidic conditions. Halosulfuron-methyl hydrolysis rate constant increased withinereasing temperature, indieating that the halosulfuron-methyl hydrolysis influenced by thetemperatures, the results showed: inhibition of hydrolysis at low temperature, high temperatureaccelerated hydrolysis; halosulfuron-methyl hydrolysis half-lives at25℃、35℃、45℃were18.9d、10.2d、5.9d. The hydrolysis rates in four different types of water were: lake water> riverwater>field water> distilled water, the half-lives were3.6d、5.2d、7.4d、11.0d. The half-life inriver water was shortest and in the distilled water was the longest. The half-life of thehalosulfuron-methyl in the surfactant solution (Tween60, Span60, sodium dodecyl sulfate,calcium dodecylbenzene sulfonate) were15.5d、15.7d、12.4d、13.9d. There are many humicacids in the natural water, and the humic acids also play an important role in the hydrolysis ofhalosulfuron-methyl. With the increasing of humic acids concentration, halosulfuron-methylhydrolysis rate constant inereased, and its degradation rate also accelerated.Meanwhile,This article also studied the Photolysis behaviors of oxyfluorfen, high-Pressuremercury lamp and xenon lampas light sources of the dynamie for its Photolysis. In the pH buffersolution with4、7、9, the photolysis half lives were86.4h、4.1h、13.3h，it can be seen thatthe photolysis rate of halosulfuron-methyl in the neutral conditions was faster than alkaline andacidic conditions. Halosulfuron-methyl could be photodegraded in acetonitrile rapidly. In contrast, the halosulfuron-methyl could hardly be degraded in acetone. The nitrate havephotosensitization effect on the photolysis of halosulfuron-methyl. With the concentration ofnitrate increases, photosensitization effect increased. The photolysis rates in four different typesof water were: river water> distilled water>lake water>field water>, the half-lives were14.2h、54.6h、69.3h、72.7h, the half-life in river water was shortest and in the distilled water was thelongest. The Photolysis in different lights were different fairly; The Photolysis rate ofhalosulfuron-methyl under high pressure mercury lamp constant was faster than the rate in thexenon lamp. The photolysis of halosulfuron-methyl was under the high mercury lamp, can beseen that oxyfluorfen in the Short wave length light is relatively unstable and degradated easily,in long-wave length light source is relatively stable and the photolysis diffieultly.