The Study On Environmental Behavior And Degradation Mechanism Of Vanisulfane(XCLSBM)

Vanisulfane is a high-efficiency and low-toxic green pesticide developed by the team of Academician Song Baoan of Guizhou University.It has a good effect on the treatment of yellow mosaic disease in plants.It is a new candidate antiviral agent.This topic takes Vanisulfane as the research object.Using the high performance liquid phase detection method,the photodegradation and hydrolysis laws and influencing factors of Vanisulfane were studied through indoor simulation experiments,and the adsorption-desorption properties of Vanisulfane in three different soils and the influence on the activities of main soil enzymes were explored.Finally,the degradation products and possible degradation pathways of Vanisulfane were determined by a high-resolution liquid-phase mass spectrometer,so as to provide a scientific basis for the environmental safety evaluation and safe use of Vanisulfane.The main research results of this paper are as follows:1.The photodegradation laws of Vanisulfane under different light sources,different concentrations,different temperatures,different acidity and different environmental factors were studied by high performance liquid chromatography.Among them,the half-lives under mercury lamp and xenon lamp irradiation are 3.13 min and 31.22 min,respectively,and the price reduction rate under mercury lamp is much higher than that under xenon lamp.The photodegradation rate of Vanisulfane decreases with the increase of the initial concentration and increases with the increase of temperature.However,when the temperature rises to about45℃,the degradation rate of Vanisulfane fluctuates little.The main reason is that in the photodegradation,thermal energy Increasing has a certain limit to the improvement of reaction rate.The half-lives under the conditions of p H 5,7,and 9 are 57.76 min,33.97 min,46.21 min,respectively,indicating that the photolysis of Vanisulfane is inhibited to a certain extent under acidic or alkaline conditions,and the degree of inhibition is greater than that of alkaline conditions.Four representative ions of common environmental factors were selected to explore the impact on the photolysis of Vanisulfane.Among them,Fe³⁺and NO₃^-ions can promote hydrolysis.The possible reason is that active free radicals are generated,while the halide ions Cl^-and I^-are the opposite.They inhibit the hydrolysis of Vanisulfane,and the higher the ion concentration,the stronger the inhibition.2.The hydrolysis of Vanisulfane is the same as photolysis,and the degradation under different conditions basically conforms to the first-order kinetic equation.The influence of different concentrations,different temperatures,and different acidity aqueous solutions on its hydrolysis was explored.The rate constants of Vanisulfane solutions with initial concentrations of 0.5,2,5,and 10 mol/L at 25℃are 0.0074,0.0051,0.0033,and 0.0025,respectively.The hydrolysis rate also decreases with the increase in concentration,and the hydrolysis half-life is in Between 93.67-277.26d,indicating that Vanisulfane belongs to a kind of difficult-to-hydrolyze pesticide.Under different p H conditions,neutral conditions have the fastest hydrolysis and acidic conditions have the slowest hydrolysis.Under the conditions of 15℃,25℃and 35℃,the hydrolysis rate of Vanisulfane increased to a certain extent with the increase of temperature.The activation energy in the p H 5,7,and 9 solutions were 18.47,24.06,and 15.59 k J/mol,respectively.The reaction coefficients are 1.29,1.39,and 1.23,respectively.It can be judged that the temperature has the greatest influence on the hydrolysis under neutral conditions.3.The adsorption and desorption of Vanisulfane in three different types of soils,Jiangxi red soil,Nanjing loess,and Northeast black soil,can all fit the Freundlich model.In the adsorption process,the adsorption capacity is Northeast black soil>Nanjing loess>Jiangxi red soil.In desorption,red soil has the strongest desorption capacity,and black soil has the weakest desorption capacity.The adsorption capacity of the three soils for Vanisulfane decreases with the increase of temperature,and the adsorption coefficient 1/n is less than 1,which belongs to L-type adsorption,that is,the lower the concentration of Vanisulfane in the soil,the stronger the adsorption capacity of the soil.At different temperatures,the free energy of adsorption in the three tested soils is less than 40 k J/mol,indicating that the adsorption mechanism of Vanisulfane in the three soils is mainly reversible physical adsorption.Under the condition of 25℃,the adsorption constants of the three soils have a good linear relationship with soil p H and soil organic matter content,and the adsorption equilibrium is reached in about 12 hours,but the desorption behavior in the three soils has a hysteresis phenomenon.4.Study the effect of Vanisulfane on the soil enzyme activity in the three soils,and found that different concentrations of Vanisulfane（0.1mg/kg,1mg/kg,10mg/kg）have a greater impact on the soil enzyme activity.On the effect of urease activity,in 45 days,different concentrations of Vanisulfane mainly inhibited urease in the three soils.Among them,the loess was continuously inhibited,and the black soil had an activation process in the early stage,but the red soil was indeed inhibited first and then The process of activating the last reinhibition.Different concentrations of Vanisulfane have a greater impact on the urease activity in the three soils,which is laterite.Among the effects on invertase activity,different concentrations of Vanisulfane basically have no effect on the invertase activity in red soil,but it has a consistent inhibitory effect on the invertase activity in loess and black soil,and the degree of inhibition on loess is greater than that on red soil.Among the effects on catalase activity,at 0 d,different concentrations of Vanisulfane can activate the catalase activity in red soil and black soil,but have an inhibitory effect on loess.After a period of time,Vanisulfane also has an inhibitory effect on the catalase activity in red soil,and the inhibitory effect has no obvious relationship with the concentration.After 20 days,the catalase activity on loess soil was transformed into activation,especially in the high-concentration experimental group,the activation effect was more obvious,while the black soil experienced the process of activation-inhibition-activation,which was also more prominent in the high-concentration experimental group.5.Finally,the photodegradation products of Vanisulfane in aqueous solution were analyzed and identified by high performance liquid chromatography tandem flight mass spectrometer,and the degradation pathway was explored.Under the irradiation of a 20 W mercury lamp,8 degradation products were analyzed,and their possible degradation pathways were analyzed,mainly including the rupture of chemical bonds,reduction to aldehydes,and intramolecular dehydration.