Research On The Environmental Behavior Of Thiamycin In Water And Soil And Its Residue On Citrus

A rapid,efficient and sensitive liquid chromatography-tandem mass spectrometry(LC-MS/MS)way of residue analysis was established for the determination of benziothiazolinone in citrus,water,and soil in this paper.3%benziothiazolinone suspension concentrate was carried out on citrus for digestion and final experiment in Guizhou,Guangxi and Hunan of 2017 and in Guizhou,Anhui,Hunan,Jiangsu,Zhejiang,Hubei,Yunnan,Guangdong and Guangxi of 2018.The final residue data were tested to provide a reasonable application method and dietary exposure risk assessment.The environmental behavior test of benziothiazolinone was conducted in labortory.the hydrolysis,photolysis,soil degradation,soil adsorption,migration and leaching behavior of benziothiazolinone were investigated.The behavior of benziothiazolinone in soil and water environment was investigated and used to infer the degradation and transfer of benziothiazolinone in natural conditions.The pretreatment analysis method of benziothiazolinone was optimised in citrus.The influence of recoveries for extraction solvent,the volume of extraction solvent,extraction procedure and sorbents was investigated,and orthogonal test was carried out to investigate the extraction conditions for the best condition.The linear relationship of benziothiazolinone was satisfactory ranged from 0.05-10μg/m L,the R~2 was 0.9949-0.9998,the limit of detection(LOD)was 0.006-0.06 mg/kg,the limit of quantification(LOQ)was 0.02-0.2 mg/kg.The spiked concentrations of benziothiazolinone were 0.02,0.2,2 and 10 mg/kg in whole citrus,citrus peel,citrus pulp and water,0.2,2 and 10mg/kg in soil.The average recoveries of benziothiazolinone in whole citrus,citrus peel,citrus pulp were 79.31%-98.68%with RSDs of 0.63%-7.60%,the average recoveries were 99.64%-102.72%in water with RSDs of 1.57%-3.24%,the average recoveries were 74.40%-103.67%with RSDs of 0.92%-8.28%.The method is applied to determine field trial samples at 12 sites in two years.The terminal residue of benziothiazolinone was<0.02-0.61 mg/kg,the dissipation residue was<0.02-0.16 mg/kg and the result was not accord with the first-order kinetic model.The chronic dietary exposure risk of benziothiazolinone according to STMR in citrus.Risk quotient values(RQ)was calculated for different age groups.On the basis of the result of long-term risk assessment,RQ values were all<1,indicating that the chronic dietary exposure risk is acceptable in China when the pesticide was sprayed at the recommended dose.Hydrolysis experiment of benziothiazolinone at different initial concentrations,p H buffer solution and temperature was simulated in labortory.The results show that the degradation of benziothiazolinone in aqueous solution was slow,these factors did not promote the degradation of benziothiazolinone strongly.The acid condition could accelerate the degradation of benziothiazolinone slightly,but there was no obvious degradation of benziothiazolinone under other conditions.The photochemical degradation kinetics and influencing factors of benziothiazolinone aqueous solution in different initial concentration,p H buffer solution,light source and light intensity were studied.The results show that the photolysis experiment of benziothiazolinone under different conditions accords with the first-order kinetic equation,and the degradation rates of benziothiazolinone will increase with concentration increasing in aqueous solution.In the photolysis experiment of p H,the degradation rate of benziothiazolinone is obviously slower than that of 7 and 9 when the p H values is 4,but the degradation dynamics under neutral and alkaline conditions are basically the same.The degradation of benziothiazolinone content in five soils was tested from different provinces and cities at laboratory simulation.The three conditions soils of non-sterilization,sterilization and water accumulation were adopted.The degradation half-lives of benziothiazolinone in Jilin,Beijing,Anhui,Guizhou and Shandong soils were 0.08,1.89,1.23,3.44 and 26.66 d in non-sterilization conditions,8.04,6.80,31.50,46.21 and 86.64 d for sterilization,and 0.18,0.35,0.4,2.21 and 4.53 d in water accumulation,respectively.The degradation half-life of non-sterilization soil is much larger than that of sterilized soil.Therefore,microorganisms are the main factors in the degradation of benziothiazolinone in soil,among which anaerobic microbe play a major role in this test.The sorption-desorption behavior of benziothiazolinone was investigated using shake equilibrium method in 5 soils.The sorption-desorption behavior in Beijing,Anhui,Guizhou and Shandong soils were in accordance with the freundlich model well.The organic carbon adsorption coefficient(Koc)is 2553.70-13270.71,and the free energy(△G)is between-18.10 and-20.98 k J/mol,indicated the adsorption is dominated by physical adsorption.The hysteresis coefficient(H)is 0.7-1.0 and there is no obvious hysteresis behavior.The adsorption capacity in the soil was Anhui soil>Shandong soil>Beijing soil>Guizhou soil.The adsorption capacity difference of benziothiazolinone is the result of the comprehensive action of various physical properties at the tested soil.In this paper,the migration and leaching of soil were studied by thin layer chromatography and soil column leaching respectively.The R_f value of soil migration is 0.26-0.58,and the order of mobility is Anhui soil>Shandong soil>Guizhou soil>Beijing soil>Jilin soil.leaching experiments showed that the contents of benziothiazolinone in different soil columns are different.According to the content of benziothiazolinone in leachate,it can be inferred that the soil leaching in Shandong Province is easier to cause more pollution to groundwater,while the soil in Jilin,Beijing and Anhui Province is not easy to cause more pollution to groundwater.