Degradation Of Acephate And Its Metabolite Methamidophos In Reap And Soil And Their Behavior Of Hydrolysis And Photolysis In Aqueous Solution

The degradation kinetic and residue level of acephate and its metabolite methamidophos were studied in rape and soil. Their behavior of hydrolysis and photolysis in aqueous solution were researched. The main conclusions are summarized as follows:1. The residue of acephate and methamidophos in wet samples(rape, soil and water) was extracted with acetone and dichloromethane. After being concentrated by evaporation, the re-extracts were cleaned up by a solid-phase extraction column of GCB. The final residue can be detected by gas chromatography with mass-spectrum detection with high sensitivity. The average recoveries from untreated samples fortified with acephate and methamidophos at rates of 0.05, 0.1, 1.0 mg/kg ranged from 82.9% to 96.9%, and the coefficient of variation was from 0.89% to 7.31 %. The lowest detectable concentration of various samples were 0.002 mg/kg, 0.002 mg/kg, 0.003 mg/kg in rape, soil and water respectively. The methods have showed good extraction and cleaning-up procedure. The method was validated by conducting linearing, good repeatability, sensitivity, precision and detection limits.2. When high dosage 72 a.i.g /mu water solution of 40% acephate EC were applied in degradation field experiment, residue and half-life of acephate in rape werel40.78 mg/kg and 1.36 days, on soil were 2.807 mg/kg and 1.84 days respectively. The first-order degradation kinetics of acephate was Ct=133.01e^-0.5107t in rape and C_t =3.0167e^-0.3775t in soil.The results showed that acephate was easy to degrade in rape and soil. Through analyzing and comparing the obtained mass spectra with the standard mass spectra, the metabolite methamidophos could identify. Its first-order degradation kinetics was C_t=6.5753e^-0.2422t in rape and C_t =0.234e^0.2255t in soil. The half-life was 2.86 days and 2.98 days relatively.The final residual field experiment of acephate was applied in rape and soil for two and three times with high dose (72 a.i.g/mu) and low dose(32a.i. g/mu).The rape and soil all had detected acephate and its metabolite methamidophos. Interval a week, the residual concentration of acephate and methamidophos in rape were 0.019¹.352mg/kg and 0.013⁰.179 mg/kg respectively. Interval 14 days, the residual concentration of acephate and methamidophos in rapes were 0.003⁰.205 mg/kg and 0 0.376mg/kg respectively. When the applying dosage and times were increased, the residue of acephate and methmidophos increased also. Interval 21 days, the GC-MS cannot detected the residues. The degradation rate in soil was slower than in rape.3. Hydrolysis kinetics of acephate and methamidophos at various buffer solution in different temperature were studied. The results indicated that the degradation rate of acephate and methamidophos were closely related to the pH values and temperatures.(1)Under temperature of 25℃ and dark conditions, the half-life of acephate and methamidophos at buffer solution of pH5.0,5.7, 7.0,...