Study On The Dynamic Degradation And Residual Regularity Of Propamocarb In Pepper And Its Photolysis In Soil

This paper have investigated the detection method of Propamocarb residue in pepper and soil sample and the degradation dynamics residual behavior of Propamocarb in paper and soil under natural environment and the photochemical degradation of the Propamocarb in soil. It has provided scientific evidences for environmental remediation, the security evaluation of ecological environment and the reasonable use of Propamocarb. The main results are summarized as following:(1) Established the GC-NPD method for the detection of Propamocarb residues in pepper(fresh pepper, dried pepper) and soil sample. The average recovery is 84.1%-106.8%, coefficient of variation is between 0.8%-7.9%. The minimum detectable concentration of Propamocarb in fresh pepper and soil both are 0.05mg/kg and 0.10mg/kg in dried pepper. This method can be used for testing the residual quantity of Propamocarb in pepper and soil by the department of agriculture; food and environmental monitoring.(2) The simulation test in Hunan, Guangdong and Zhejiang have studied the degradation dynamics of Propamocarb in pepper and soil. The degradation of Propamocarb in pepper and soil are both accord with first order kinetics equation:Ct=C0e-kt; the degradation half life is 4.01-8.92d and 5.08-7.66d. The results show that Propamocarb disappears fast in pepper and soil it is easily degradation pesticide.(3) Under the natural condition of this three province, using 66.5% Propamocarb Hydrochloride AS on pepper follow the pesticide apply method and application rate which are recommended, after the last pesticide application more than 7 days, the maximum residue of Propamocarb is 0.870mg/kg. It’s accord with the maximum residue limit(MRL) of Propamocarb in pepper in China:3.0mg/kg. According to the experimental result the reasonable use technical standards of 66.5% Propamocarb Hydrochloride AS on pepper is proposed:In the pepper growing season,66.5% Propamocarb Hydrochloride AS with the dose of 1650 ml/ha (the active ingredients of Propamocarb is 1191.3 g/ha) is sprayed on pepper for preventing insect pests by mixing with water 750 L/ha, applying at most 3 times (spraying interval is 7-10 days), the safe interval is 7 days.(4) The photodegradation of Propamocarb in soil is accord with chemical reaction kinetic equation.Under HPML irradiation photolysis rate of soil Propamocarb was significantly faster than the photolysis rate of sunlight, half lives were 121.6h and 203.8h. Adjust the soil pH value have a great effect on the photolysis of Propamocarb, half-life(pH=10) is shorter than half-life(pH=7) by 67.2%. Adding 0-200mg/kg TiO2, the photodegradation rate of soil Propamocarb gradually increases with the increase of TiO2 concentration. Adding a certain amount of Fe3+ to enhance the photocatalytic effect of TiO2 is significant, photolysis rate of soil in Propamocarb TiO2 under the condition of different ratio of Fe3+/Ti02: 10:200> 20:200> 5:200> 0:200, the half-life of respectively are 33.6h, 50.2h,55.0h and 72.9h.