Environmental Behavior Of Spirotetramat

Spirotetramat is a new pesticide developed by Bayer Crop Science(Germany),which belongs to the chemical class of tetronic acid derivative.It exhibits a unique property with a two-way systemicity and is transported within both the xylem and phloem.By interfering with the fat synthesis of insects,it can effective prevention and treatment of sucking mouthparts pests.Since spirotetramat is generally considered to be innocuous and lowly toxic,recently in China and abroad,only a few studies focused on the analysis of spirotetramat residue and its fate along with its metabolites in the environment.In this paper,spirotetramat was used as the research object.The method of residue analysis of spirotertamat and its four metabolites in spinach,soil and water was established.The effects of different environmental factors on the adsorption and desorption of spirotertamat in different types of soils were studied.The environmental metabolic behavior of spirotertamat in spinach.soil and water was studied.The major findings are as follows:(1)In this study,QuEChERS and solid phase extraction sample pretreatment methods and liquid chromatography-tandem mass spectrometry(LC-MS/MS)detection technology with negative ion scanning and multi-reaction monitoring mode(MRM)were used.The method of residue analysis of spirotertamat and its four metabolites in spinach,soil and water was established.The results showed that chromatographic resolution and sensitivity were the best when the acetonitrile-0.5%formic acid solution was used as the mobile phase.Through the study of sample pretreatment conditions,samples treated with 50 mg of N-propyl ethylenediamine(PSA)+graphitized carbon black(GCB)(1/1,m/m)with 0.1%formic acid-acetonitrile as the extraction solvent.The recoveries of spirotetramat and its four metabolites in spinach and soil were in accordance with the requirement of pesticide residue detection.The recovery rate of ethanol and its four metabolites in water was 80.44%～101.23%by using NH2 column as solid phase extraction column and 10 mL of dichloromethane as elution solvent.The method has the advantages of high recovery rate,low detection limit and good linearity.And it is suitable for simultaneous detection of spirotertamat and its four metabolites residues in spinach,soil and water.(2)The adsorption and desorption behavior of spirotetramat in soils was studied by using batch equilibrium method.The results showed that the Freundlich model can well fit the adsorption-desorption parameters of spirotetramat in six kinds of soils.The order of the adsorption capacity of the six kinds of soils to spirotetramat was:Guangzhou soil>Yangzhou soil>Beijing soil>Changchun soil>Chengdu soil>Pingxiang soil.Adsorption capacity of the soil to spirotetramat enhanced with increasing temperature,the adsorption behavior of spirotetramat is spontaneous.The effect of pH value on the adsorption behavior of spirotetramat in soil was significantly.Adsorption capacity of the soil to spirotetramat with the pH rises enhanced.The low content of humic acid(0.1%and 1%)increased the adsorption capacity of the soil to spirotetramat.Addition of surfactant(AS,CATB and Tween80),such that the adsorption capacity of 3 soils(Guangzhou soil,Changchun soil and Yangzhou soil)weakened and 3 soils(Beijing soil,Chengdu soil and Pingxiang soil)increased.From the hysteresis coefficient,spirotetramat was easy to desorption from the tested soil,which was difficult to accumulate in the soil for a long time and has certain migration characteristics.(3)The metabolic behavior of spirotetramat in different water environment was studied by indoor simulation experiment.The results showed that the half-life of spirotetramat in water was 13.59 d under light treatment,and its half-life in the water was 19.80 d in dark treatment.The degradation rate of spirotetramat was significantly changed in different pH buffer solution,and the degradation rate was significantly improved with the increase of pH value.When the solution was pH=9,the spirotertamat was almost completely degraded in water and almost completely degraded after 2 h,and the residual concentration of spirotertamat was only 0.0243 mg/kg.At different temperatures,the degradation rate of spirotetramat in water decreased with the increase of temperature,and its degradation half-life decreased.In different water environment conditions,two kinds of spirotetramt’s metabolites(B-enol and B-keto)were detected.It can be seen from the residual concentration of two metabolites that B-enol was the main metabolite of the spirotetramat in water.(4)The metabolic behaviors of spirotetramat in spinach and soil were studied by field experiment.The results showed that the degradation rates of spirotertamat were different in different media.When the 22.4%spirptetramat SC was applied at the field recommended dose and its double dose,in the spinach leaves,the degradation half-life of spirotertamat were 11.00 d and 10.66 d respectively.In spinach stalks,the half-life of spirotertamat were 10.66 d and 11.36 d,respectively.In the spinach roots,the degradation of spirotetramat was faster and the half-life was 4.36 d and 4.88 d respectively.In the soil,the degradation of spirotetramat was rapid and it was not easy to remain in the soil.the half-life of spirotertamat were 2.48 d and 3.42 d.The spirotertamat in different media have different metabolites.The main metabolites were B-enol,followed by B-keto and B-glu,in the spinach leaves.In the spinach stalk,spirotertamat could be metabolized to B-enol and B-glu,the residual concentration of B-enol is slightly higher than the residual concentration of B-glu.In the spinach roots,spirotetramat could be metabolized to B-enol,the highest residual concentration of it was 0.0336 mg/kg in the root.In the soils,two kinds of spirotetramt’s metabolites(B-enol and B-mono)were detected,which kept increasing in the soil and then rapidly digested.In this study,the method of LC-MS/MS residual analysis of spirotetramat and its four metabolites was established.The adsorption and desorption behaviors of spirotetramat in soils were investigated.The residual degradation of spirotetramat in different environmental media(spinach,soil and water)was explored,and its metabolites were clarified.This study will provide a basis for further elucidating the mechanism of migration and transformation of spirotetramat in the environment,and provide a method for the safety inspection of agricultural products.It provides an important theoretical basis for comprehensively revealing the environmental behavior of spirotetramat and assessing its environmental risks.