The Residue Behavior Of Phenthoate In Rice Environment

Phenthoate (O, O-dimethyl-S-(alpha-ethoxycarbonyl-benzyl) is a kind of systemic organophosphorus pesticide developed by Italian Monte Kasiha company, which firstly put it into industrial production successfully. The phethoate has a significant control efficiency on rice stem borer, yellow stem borer and rice leaf roller. It has a less toxic to non-target organism or degraded rapidly in vivo, so it can be a replacement of high-toxic pesticides, which was urgently needed in rice production. This article has researched the dissipation dynamics of phenthoate in rice and the degradation and absorption in soil and water in laboratory, which provide a scientific basis for establishing the safe use of standard of pesticide.A simple, rapid residue analytical method of phenthoate in paddy water, soil, rice plant, grain and rice husk was developed. The residue of phenthoate in rice plant was extracted with petroleum ether, concentrated over activated carbon column, cleaned up with ethyl acetate, and determined by GC using equipped with an electron capture detector. The residue of phenthoate was extracted from the other samples with petroleum ether, filtrated by Buchner funnel, concentrated and determined by GC using equipped with an electron capture detector. The detected limit of GC-ECD for phenthoate is0.001ng. The minimum detectable concentration in paddy water is0.001mg/kg, in soil and grain is0.004mg/kg, rice husk and plant0.01mg/kg.Results of field test showed that, after spraying1.5times of the recommended dose, the half lives of phenthoate in paddy water, soil and rice plant was0.92-2.20d,6.55-10.23d and2.28-4.33d, respectively. The results of ultimate residue test of2009and2010showed the ultimate residues of phenthoate showed it is30days that the phenthoate residue was degraded below0.05mg/kg in rice plant,0.3mg/kg in rice husk,0.05mg/kg in grain. Therefore it is recommended that the safety interval was30days for the recommended dose. The MRL of phenthoate was recommended as0.05mg/kg.According to the test of the degradation and absorption of phenthoate in soil and water showed the rate went more quickly with the increase of soil temperature. The half lives of phenthoate were12.24、7.64and3.52d, respectively, when the soil temperature was10℃,20℃,30℃. When the water content increased, the phenthoate degraded more rapidly. The half lives of phenthoate were10.66、11.65、6.53d under the pH was5,7,9, respectively. The presence of microbes would promote the degradation of phenthoate. In unsterilized and sterilized soil the half lives of phenthoate were7.64d and10.67d, respectively. The absorption of phenthoate in the three kinds of soils conformed to Freundich equation, and the absorption went stronger with the increasing of organic carbon content. The phenthoate absorption by soil belonged to physisorption with changes of free energy less than40kJ-mol-1.This research has studied the dissipation dynamics of phenthoate in Beijing and Fuzhou district, combined with the data of the test the test of the degradation and absorption of phenthoate in soil and water, delivered a suggestion for the MRL and the safety interval of phenthoate, providing a scientific basis for establishing the safe use of standard of pesticide at the time.