The Degradation And Residue Of Thifluzamide And Kresoxim-methyl In Wheat And Its Adsorption On Soil Mineral

In order to find out the residual digestion of 50% Thifluzamide and kresoxim-methyl in wheat samples after the application of Thifluzamide and kresoxim-methyl as the main components in wheat.With the help of GC-ECD detection technology,the method of simultaneous analysis and detection of Thifluzamide and kresoxim-methyl ester residues in wheat samples was studied and established by adding recovery experiments.On this basis,a field experiment in line with GAP code was used to systematically and comprehensively study its residual digestion on wheat.In addition,batch balance method was used to study the adsorption and influencing factors of Thifluzamide and kresoxim-methyl on five soil minerals.These studies can not only to scientifically evaluate the dietary risk to provide data support in the wheat,and can also provide guidance pesticide formulations containing these two active ingredients will provide a scientific basis for rational fertilization,and the pollution caused by the residual environmental governance provides an effective way to repair and feasible techniques and methods.The main research results are as follows:(1)Simultaneous analysis and detection of Thifluzamide and kresoxim-methyl in wheat samples: wheat samples were extracted with acetonitrile,purified by neutral alumina column,and determined by GC-ECD;When the addition concentrations of Thifluzamide and kresoxim-methyl were 0.01 mg/kg,0.05 mg/kg and 0.50 mg/kg,respectively,the recovery of addition in wheat grains was 85.5%?105.9%,and the relative standard deviation was 6.5%?9.1%.The recovery of wheat straw was 85.5%?105.1% and the relative standard deviation was 7.1%?9.6%.The quantitative limits of wheat grain and wheat straw were both 0.01mg/kg,and the minimum detection amount was 1 10-11 g.The method is simple to operate,and its sensitivity,accuracy and precision meet the technical requirements of pesticide residue detection in China.(2)Residual digestion of Thifluzamide and kresoxim-methyl in wheat: the digestion of Thifluzamide and kresoxim-methyl in wheat grains conforms to the first-order kinetic equation Ct=C0·e-kt,and the correlation coefficient is between 0.7686 and 0.9929,both reaching the significance level.The half-life of etofenurate in wheat was 2.1d?5.3d,and that of Thifluzamide was 4.9d?8.3d.This indicated that kresoxim-methyl and Thifluzamide were easily digested in wheat grains and could not cause residual contamination.The residue of kresoxim-methyl and Thifluzamide in wheat: at 21 d after the last application,the residue of kresoxim-methyl in wheat grain was <0.01?0.078 mg/kg,and that in wheat straw was 0.035?5.487 mg/kg.The residue of Thifluzamide in wheat was <0.01?2.836 mg/kg,and the residue of wheat straw was 8.803?18.223 mg/kg.At 28 days after the last application,the residue of etofenurate in the small wheat grains was <0.01?0.079 mg/kg,and the residue in the wheat straw was 0.018?5.122 mg/kg.The residue of Thifluzamide in wheat was <0.01?1.846 mg/kg,and that in wheat straw was 5.150?17.907 mg/kg.(3)Dietary risk assessment of Thifluzamide and kresoxim-methyl in wheat grains: at 28 days after the last application,the median STMR and maximum HR of kresoxim-methyl in wheat grains were 0.017mg/kg and 0.079 mg/kg respectively.The median STMR and HR of Thifluzamide residues in wheat were 1.097 mg/kg and 1.645 mg/kg respectively.According to the situation of pesticide registration in China and China's per capita dietary structure,obtained the general population.Consult to estimate the daily intake of amide is 0.0332 mg,3.6% of the daily intake,kresoxim-methyl estimated intake of 0.0023 mg per day,accounts for only 0.01% of the daily intake,so think,kresoxim-methyl and Thifluzamide residue of amide in wheat grain won't cause unacceptable risk to health of the general population.According to the results of dietary risk assessment report,the recommended MRL value of Thifluzamide on wheat grain is 2.0 mg/kg.The reasonable use of 50% kresoxim-methyl · Thifluzamide water dispersible granule on wheat is suggested as follows: 50% kresoxim-methyl · Thifluzamide water dispersible granule was diluted with water for 2 times on wheat with 180 g.A.i /ha(dosage: 24.0g/ mu),and the recommended safe interval was 28 d.(4)Adsorption of Thifluzamide and kresoxim-methyl in the five soil minerals(Montmorillonite,Kaolinite,Illite,Magnetite,Goethite): the adsorption equilibrium time of Thifluzamide and kresoxim-methyl in the five soil minerals was between 10 h and 24 h.The adsorption kinetic process was best described by pseudo second-order kinetic equation,followed by particle diffusion equation,and the worst was Elovich equation.The isothermal adsorption process was best described using Linear and Freundlich adsorption models(both reaching the significance level),but less well described using Langumir adsorption model(not reaching the significance level).The adsorption isotherms of kresoxim-methyl and Thifluzamide showed "S type" instead of "L type".Temperature to kresoxim-methyl and Thifluzamide cefuroxime acid: the influence of five kinds of minerals in the soil adsorption when temperature from 5 ? to 25 ?,the adsorption quantity increases gradually,reached the maximum at 25 ?,with the increase of temperature after its adsorption capacity gradually decreases.Effect of pH value on adsorption of kresoxim-methyl and Thifluzamide in five kinds of soil minerals: kresoxim-methyl: when the pH value increases from 3.0 to 5.0,the adsorption amount of magnetite to etheryl ester gradually decreases and reaches the minimum value when the pH value is 5.0,and the adsorption amount of the other four kinds of soil minerals increases significantly.When the pH value rose from 5.0 to 7.0,the magnetite adsorption slowly increased,and the other four soil minerals significantly decreased,reaching the minimum value when the pH value was 7.0;When the pH value increased from 7.0 to 11.0,the adsorption amounts of the five soil minerals all showed different degrees of increasing trend.When the pH value was 11.0,they all reached the maximum value.Thifluzamide : when p H from 3.0 to 5.0,montmorillonite,kaolinite and illite Thifluzamide injunctions on the adsorption quantity increase gradually,the pH value of 5.0 up to the maximum,when the pH from 5.0 to 9.0,after its adsorption capacity gradually decreases,the p H value of 9.0 up to the minimum,but when pH from 9.0 to 11.0,its adsorption amount gradually rise again;However,the adsorption of Thifluzamide by goethite and magnetite decreased significantly when the pH value increased from 3.0 to 5.0,and then slowly increased when the pH value increased from 5.0 to 11.0.kresoxim-methyl and Thifluzamide in the infrared spectral analysis of the five kinds of soil minerals,kresoxim-methyl mainly through hydrogen bonding and surface complexation effect such as adsorption in kaolinite,through hydrogen bonding and charge transfer effect such as adsorption in montmorillonite stone,through hydrogen bonding,surface complexation and charge transfer effect such as adsorption in illite,goethite and magnetite;Thifluzamide is mainly adsorbed in kaolinite by charge transfer,in montmorillonite by hydrogen bond and charge transfer,and in illite,goethite and magnetite by hydrogen bond,surface complexation and charge transfer.