| Florasulam is a triazole pyrimidine sulfonamide herbicide,It was developed by Dow Agricultural Science in the mid-1990 s.The is mainly used in post-emergence stem and leaf treatment to control broadleaf weeds such as winter wheat,spring wheat,barley and lawn.Due to its wide range of use and strong mixability,florasulam has been widely used in recent years.In this paper,florasulam was used as the research object,and the degradation and transformation of the agent in water and soil environment were studied.Simulating natural light and ultraviolet light in the aquatic environment,studying the photolysis kinetics,photodegradat ion products,photodegradation mechanism,degradation pathways of florasulam and the addition of different substances in the water environment,and examining the degradation of florasulam by environmental factors Impact.Provide a scientific basis for its safe use and environmental safety.The main results of this thesis are as follows:(1)Determined the residue detection method of the herbicide florasulam in wheat grain,straw,water and soil by Qu ECh ERS treatment and ultra performance liquid chromatography tandem mass spectrometry.The extraction method and purification method were optimized in wheat grain,straw,water and soil matrix.Finally,the external standard method was used for quantitative determination.The results showed that when the concentration of florasulam was between 0.01 and 1 mg L-1,it showed a good linear relationship,and the correlation coefficient(r)of the correlation coefficient was 0.9997,which was detected in the above four matrices.The limit is 0.01 mg/L.The recovery rate was between 85.9% and 105.5%,and the relative standard deviations(RSDs)were between 1.3% and 9.8%.The limit of quantitation(LOQs)of the modified method was 100 ?g kg-1.The method is simple and rapid,and can meet the needs of detection of florasulam pesticide residues in wheat field environment.(2)The effects of photodegradation in the water environment were examined.The results showed that the residual amount of florasulam was almost undegraded under darkroom conditions.In this experiment,a photochemical reaction device was used,and the xenon lamp and mercury lamp were used as radiation sources respectively to obtain the degradation rate of florasulam under the irradiation of xenon lamp.Significantly lower than the degradation rate under mercury lamp,florasulam in the same source of radiation,different initial concentrations of florasulam can follow the first-order kinetic equation,and the photolysis rate of florasulam Its concentration gradually decreases.When the p H was 7 and 9,there was no significant difference in the degradation rate of florasulam,and the photolysis half-lives were 5.9 min and 6.0 min,respectively.When the solution was acidic,it inhibited the ionic form of difluorosulfonate.The amine has a half-life of 115.5 min.The photolysis half-life under neutral and alkaline conditions is significantly lower than the photolysis half-life under acidic conditions.(3)The effects of dissolved substances,insoluble substances and different water bodies on the photodegradation of florasulam were investigated.The results showed that in the range of 0.01-0.1 mg L-1,the photolysis rate of florasulam was increased with the increase of Fe3+ concentration,and the concentration range of 0.01-10 mg L-1,I-strongly inhibits the degradation of florasulam,and as the concentration increases,the inhibitory effect increases.When the concentration of nitrate ions is in the range of 0.01-10 mg L-1,the low concentration promotes the photolysis of florasulam.With the increase of concentration,the photolysis rate decreases and the inhibitory effect is obtained.The humectin,a common substance in natural water,was selected to simulate the suspension in water,and its effect on the degradation of florasulam was investigated.The results showed that humin significantly inhibited the degradation.(4)UPLC-QTof-MS technology was used to isolate and identify the photolysis products TPs of six florasulam in water environment,and based on the identified TPs and their evolution process,florasulam was inferred.The degradation mechanism leads to four degradation pathways,sulfonamide bond cleavage to form TPs2,intermolecular rearrangement to form SO2 isomerization compound TPs3,C-F bond cleavage to form TPs1,TPs4,TPs5,hydroxylation to form TPs6.The stability of the product in the water environment was speculated.TPs1-3,5 were rapidly degraded after reaching the maximum concentration in the formation process,and had poor photostability,which is a compound that is not easily accumulated in water.TPs4 and TPs6 have better photostability than florsulam,which may be the main substance causing water pollution.(5)Studies on the degradation of florasulam in an aqueous environment have shown.Under the same p H condition,the degradation rate of florasulam increased with the increase of temperature.The degradation half-life of the degradation half-life at 15°C> 25°C>35°C>45°C under different temperature conditions,45°C The degradation rate is the highest.In addition,experiments have confirmed that florasulam has a faster hydrolysis rate under alkaline conditions.When the temperature is 25°C,when the p H values of the solutions are 4,7 and 9,respectively,the degradation half-life of florasulam in water is respectively It is 115.5 min,86.6 min and 69.3 min.The hydrolysis degradation rate of florasulam under acidic condition is l ower than neutral and alkaline.(6)The degradation of florasulam in three different types of soils showed that when the culture temperature was 35°C,the degradation rate of black soil was the fastest,followed by yellow brown soil,while the degradation rate of red soil was the slowest.The degradation half-lives were 9.76 d,16.9 d,and 28.9 d,respectively.The degradation rate of florasulam in the same type of soil increased with the increase of temperature.The degradation rate of florasulam in unsterilized soil was about twice that of sterilized soil.Degradation rateis higher than sterilized soil. |
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