Accumulation Principle And Management Strategy For Pesticide Residue In Rice

Rice is one of the most principal grain produces in Chinese agriculture, more than65% of the population feed on rice in China. Quality safety of rice has become dominateproblem which is concerned because a grate deal of pesticides were applied to. The articlethat analysis the dynamical principle of frequent pesticides on the rice, and then primarilyexplored the preventability measures to control the pesticide residues and countermeasuresto safety precautions, the results are list below.1. Residual dynamics of Fipronil, Chlorpyrifos, Imidacloprid and Buprofezin on the ricewere studied using gas chromatography. The results indicated the half-lives of Fipronil,Chlorpyrifos. Buprofezin and Imidacloprid on the rice were 2.59, 4.89, 2.76 and 3.49days respectively. Buprofezin and Imidacloprid were applied to rice three times basedon the double recommended dosage, within the preharvest interval 14 days, the finalresidues of buprofezin and imidacloprid were 0.0057mg/kg, 0.018mg/kg, which werebelow the Maximum Residue Limits. Fipronil was applied to rice three times based onthe double recommended dosage, within the preharvest interval 14 days, the finalresidue was 0.024mg/kg, which is above the the Maximum Residue Limits lever.Chlorpyrifos was applied to rice two times based on the recommended dosage,withinthe preharvest interval 14 days, the final residue was 0.57mg/kg, which is above the theMaximum Residue Limits lever.2. Application of conbined pesticides was an available preventability strategy forreducing pesticide residues, we wanted to introduce Fipronil to combine Triazophos,Phoxim and Chlorpyrifos respectively, after bioassay screening, the optimizationproportion(active ingredient)were 1:35, 1:35, 1:24 and co-toxicity coefficient were185.28, 154.12, 130.66 respectively, which enhanced insecticidal activity. The result offinal residue indicated that the mixture Fipronil- Triazophos and Fipronil- Phoxim wereapplied to rice two times based on referrence dosage 405g/ha, within the preharvestinterval 14 days, the final residues of Fipronil, Triazophos, Phoxim were all nodetection(＜0.001mg/kg); the mixture Fipronil- Chlorpyrifos was applied to rice two times based on referrence dosage 375g/ha, within the preharvest interval 21days, thefinal residues of Fipronil was no detection, the Chlorpyrifos residue in rice was0.043mg/kg which was within the Maximum Residue Limits.3. Appropriate disposal methods to after-harvest have the value for reducing residualpesticides. Six frequent pesticides were sprayed on rice and then detection the changeof concentration after isolation, reposition, washing and boiling, the final degradationrate of buprofezin, imidacloprid, chlorpyrifos, triazophos, acephate and Fipronil was94.54%, 98.16%, 96.03%, 96.49%, 100.00% and 96.16% respectively. The degradationrate of pesticides were markedly difference in the different disposals, the reposition andboiling were the main degradation method of six pesticides (p＜0.05), isolation was alsoimportant degradation method of imidacloprid.Based on the above results, strictly in accordance with the recommended dosage ofapplication and to control the times of application, postpone the recommended preharvestinterval of Chlorpyrifos, application of conbined pesticides and post-harvest were throughisolation, reposition, washing, boiling and other control methods. Rice can be based thesemethods for the initial control pesticide residues of the entire process.