Environment Safety Evaluation Of The Triazophos·chlorpyrifos In Paddy Fields

An efficient compound organophosphorus pesticides formed by triazophos and chlorpyrifos is widely used in China’s rice production process. In order to get a comprehensive evaluation about applications in paddy field environment, some field experiments have been done to test its security and from the experiments we can understand its digestion dynamics and residue level to evaluate the risk of residues. Through the aquatic organisms acute toxicity tests we evaluate the safety of its environmental toxicology. Finally, by using USEPA techniques, we evaluate the pesticide’s ecological risk in paddy field environment in China.This dissertation established a detection residue analysis method on paddy water、 paddy soil and rice plant of triazophos chlorpyrifos by (GC/PFPD)method.The results indicated that the average recoveries of this method of triazophos ranged from80.5%～106.1%with the relative standard deviations of5.4%～8.0%and the average recoveries of this method of chlorpyrifos ranged from79.1%～109.4%with the relative standard deviations of2.6%～8.5%when triazophos·chlorpyrifos was spiked level of0.01～1.0mg/kg. The sensitivity and accuracy of the method are conform to the requirements of the residual analysis, can be used in the pesticide residues in rice detection. After two years out of6field experiment, studied the degradation dynamics of triazophos chlorpyrifos in rice plant、paddy soil and paddy water and its final residues in rice plant、brown rice and rice husk, The average half lives of trazophos in rice plant and paddy soil were1.6days and4.0days, the average half lives of chlorprifos in rice plant and paddy soil were1.5days and4.0days,but the half lives of triazophos·chlorpyrifos in paddy water only existed in Shangdong and Tianjin. These results showed that triazophos chlorpyrifos was the degradable fungicides. The final residue test indicated that when the rice plant was sprayed3times with32%triazophos·chlorpyrifos EW in the highest dosage of432g·ai/hm2, the last application was done at21days before harvesting, the residue of triazophos did not exceed0.044mg/kg, lower than our MRL0.05mg/kg,and the last application was done at14days before harvesting, the residue of chlorpyrifos did not exceed 0.098mg/kg, lower than our MRL0.1mg/kg,show that its safe interval was21days before harvesting. A cute toxicity of32%triazophos·chlorpyrifos EW to aquatic organisms was studied.The results show chlorpyrifos to Brachydanio rerio acute toxicity96h LC50was2.15mg/L,Daphnia magnastraus48h EC50acute toxicity was2.15mg/L, with reference to our country the toxic effects of standard grade,this pesticide was classified to be moderate in toxicity to Brachy danio rerio and high to Daphnia magnastraus; Using GENEEC model and the actual monitoring test to get the environment exposure of the triazophos·chlorpyrifos in paddy fields, evaluate the ecological risk of the pesticide according to the USEPA the pesticide ecological risk assessment technology,show that triazophos·chlorpyrifos did a high risk to Brachydanio rerio and Daphnia magnastraus,and a relatively low risk to Scenedesmus obliquus.Above all, the digestion rate faster and the residue level is low of the triazophos·chlorpyrifos used in paddy, so it is safety to human’s health,as long as control the dosage and harvest time; But greater effects on the safety of the pesticides on aquatic organisms, especially for aquatic animals (Brachydanio rerio and Daphnia magnastraus), its ecological risk are high risk. therefore, applying the pesticide should be reasonable and must be in strict accordance with the instructions in paddy, pay special attention to avoid pesticide pollution in the aquatic environment, or the use of triazophos chlorpyrifos should be restricted in paddy fields.