The Residual And Degeradation Of Nitenpyram In Paddy Field And Its Adsorption In Five Kinds Of Soil Tested

Nitenpyram is a kind of insecticide which is belong to tobacco imide. This pesticide was widely used in all kinds of crops,vegetables and fruit s. It is maily prevent from the sucking pests.This study analysised the r esidue and degradation of nitenpyram systematically in paddy water,soil a nd straw. Its adsorption was probed in the five kinds of soil tested. It was very important to assess the safety of nitenpyram after it was appli ed in paddy filed, and to provide some fundamental datas for scientific application of nitenpyram.The main conclusions were as follows:The methods of HPLC analysis of nitenpyram was established.The paddy s traw and paddy water were extracted by Dichloromethane,and the paddy soil,ric e and rice hull were extracted by methanol,then purified by a florisil chromagr aphy column,subsequently detected by HPLC with UV detector.The minimum d etectable amount of nitenpyram was6.0×10-10g and the lowest detectable conce ntrations in paddy water,paddy soil,paddy straw,rice hull was1.5×10-3mg/L,7.5×10-3mg/kg,1.5×10-2mg/kg,1.5×10-2mg/kg,1.5×10-2mg/kg,respectively.W hen the added concentration of nitenpyram ranged from0.05to5.00mg/k g,the average recoveries changed from70.39%to87.08%and the RSD of variations were ranged from0.84%-4.58%for different kinds of sample tested.The degradation of nitenpyram followed a equation of one-grade chemical reaction dynamics in the different kinds of sample, and its average degradation half-life of nitenpyram was1.90d in paddy water from Hunan Changsha,Zheji ang Hangzhou and Guizhou Guiyang, its average half-life was2.21d in paddy soil,and its average half-life was4.78d in paddy straw,respectively,This showed that nitenpyram is an easily degradable pesticides (T<30d).The recommended a mount of usage60g.a.i/ha and higher usage90g.a.i/ha of nitenpyram were advised to apply to the paddy field4or5times during the paddy growth pe riod and the interval should be7days, the residue of nitenpyram in rice was less than the lowest detectable concentration1.5×10-2mg/kg) and was lower t han the corresponding MRL value(0.5mg/kg).The adsorption of nitenpyram in five kinds of soil tested were consistent w ell with the Freundlich isotherm equation;Its adsorption was the strongest in th e black soil from Shandong while the adsorption was weakest in the river alluv ial soil from Hunan.The adsorption free energy of nitenpyram in five kinds of soil tested as less than40kJ/mol,what indicates that its adsorption in soil belon ged to physical adsorption process.In the same concentration and valence,the change of value of Kf was NH4+>Na+about the competitive adsorption capacity of different cation when nitenp yram was coexisted with NaCl、NaNO3or NH4Cl in five kinds of soil tested;u nder the same condition,the competitive adsorption capacity of different anion was different,and the change of value of Kf was No3+<Cl+in red soil from Hu nan、the river alluvial soil from Hunan and the blown soil from Shandong and Henan. The adsorption free energy of nitenpyram in five kinds of soil tested a s less than40kJ/mol,what indicates that the adsorption of nitenpyram in soil belonged to physical adsorption process.