Research On The Degradation Of Several Typical Pesticide Residues In Rice

This research studies about degradation of several typical pesticide in rice.It's aim to find a way of regulating the storage conditions to accelerate the degradation of pesticide residues.The main results are as follows:?This report established a way of RP-HPLC to determine the degradation of Imidacloprid,1-Naphthalenyl methyl carbamate,Fenitrothion,Chlorpyrifos-methyl and Deltamethrin in rice.Using acetonitrile as extractin agent and then extract and purify the samples by Qu ECh ERS Kit.The linear range from 0.1mg/kg to 10.0mg/kg,the detection limits between 0.0062mg/kg and 0.0125mg/kg,the recovery rates between 75.17% and 100.59%,the RSD range from 0.44% to 11.24%.?The research studies about the degradation of the pesticide which is influenced by the storage conditions of rice such as temperature,relative humidity and illumination duration.With the increase of temperature,the degradation rate of the 5 kinds of pesticide are increasing.When the temperature is increased to a certain value,the degradation rate reach the top and then it is going to down with the temperature rising again.Because with the rising of temperature the pesticide volatilization is strengthen which result in reinforcing the degradation of pesticide.Generally speaking,the microbial activity is range from 25? to 35?,when the temperature is beyond of this scope,the activity of microbiology is inhibited which lead to decrease the degradationg of pseticides.As the relative humidity rises,the degradation rate of the 5 kinds of pesticide showed different degrees of speed.Among which,the degradation of Imidacloprid,1-Naphthalenyl methyl carbamate and Deltamethrin rise first and then slow down,Fenitrothion and Chlorpyrifos-methyl's degradation rate always increase.This may be related to the hydrolysis of pesticide,the pesticide moecules interact with water molecules which damage the structure of the pesticide,thus accelerate the degradation rate.Meanwhile,relative humidity has a great effects on microbial growth and reproduction,too high humidity may be inhibit the microbiology's activity,which result in reducing the degradationg of pesticide by microorganisms.The increase of light duration accelerat the degradation rate.Among them,Deltamethrin showed least sensitive to light,the photolysis rate was lower than other pesticides.Fenitrothion and Chlorpyrifos-methyl's degradation were most quickly,then followed by Imidacloprid and 1-Naphthalenyl methyl carbamate.?This research stduies about the optimal storage conditions whicn can promote rice pesticide residue degradation by all factors interaction experiments.The best storage conditions are 35?,75%?relative humidity?and 6h/d of light.Under this conditons,we found that the degradation model are fit for exponential function model and the degradation of first-order equations are followed: Y =5.73e^{-0.118 x} ?Y =6.0798e^{-0.095 x} ?Y=7.0766e^{-0.053 x} ?Y=7.9649e^{-0.08 x} ?Y=5.3122e^{-0.049 x},the half-life period are: 1.623d?2.887d?9.326d?7.177d?2.152 d.According to the kinetic equations,we can establish the pesticide degradation model.Assuming that the spraying concentration is C,the half-life period is T,then substitute into the equation to get the half-life period of the 5 kinds of pesticide are: T_0.5=?ln2-ln C?/0.206?T_0.5=?ln2-ln C?/0.1715?T_0.5=?ln2-ln C?/0.1037?T_0.5=?ln2-ln C?/0.166?T_0.5=?ln2-ln C?/0.082.The time required for degradation of 90% are: T_0.9=?ln10-ln9C?/0.206?T_0.9=?ln10-ln9C?/0.1715?T_0.9=?ln10-ln9C?/0.1037?T_0.9=?ln10-ln9C?/0.166?T_0.9=?ln10-ln9C?/0.082.According to the MRLs of national standard of the 5 kinds of pesticide,the storage time need to be at least of 40d?2d?6.5d?54.7d?48.2d,so,the rice which contains the 5 kinds of pesticide should take about 60 days' storage then can be edible.