Studies On Residual Degradation And Adsorption Of Difenoconazole And Propiconazole In Paddy

Difenoconazole and propicondzole were triazole fungicide applied in paddy,they showed good inhibitory effect on the rice sheath blight. The behavior and effect of difenoconazole and propicondzole in paddy were studied in the thesis in order to provide some fundamental datas for the enviormnent saefty and ecological enviroment effect assessment, and also conduce to scientific application of difenoconazole and propicondzole. It was necessary to develop an effective residue analysis method for monitoring the residue and degradation process of difenoeonazole and propicondzole in paddy.At the same time, it is also necessary to establish their reasonable application criterion, which was also basic for evaluating their safety to rice and environment. The main contents were as follows:Chapter 1:It was a survey article that it introduced physical and chemical properies and advancement on research and development of difenoconazole and propicondzole, respectively. Previous studies focused mainly on toxicity, characterist and efficacy, little information was available about their behvaior and effect in paddy. The thesis summarized briefly that current research informations of difenoconazole and propicondzole about toxicity, potency, analysis method.Chapter 2:An simultaneously detective and effective gas chromatography analysis methods were established to determine the residue of difenoconazole and propicondzole in paddy water, soil, straw, rice hull and brown rice. Samples were extracted with acetone, purified on liquid-liquid partition and the extract was purified by a chromography column of florisil, subsequently detected by gas chromatography with electron-capture detector. when the added amount changed from 0.01 to 0.50 mg/kg in the samples, the average recoveries of difenoconazole ranged from 80.81% to 112.85% and the coefficient of variations changed from 0.74% to 6.11%. While at the same added amount, the data of propicondzole ranged from 83.71% to 112.11% and changed from 2.52% to 7.29%, respectively. Detectable limits of difenoconazole residue in paddy water, soil, straw, rice hull and brown rice were 5×10-3 mg/L, 1.25×10-3,2.5×10-3,2.5×10-3,2.5×10-3 mg/kg, respectively,and detectable limits of propiconazole residue were 1×10-4 mg/L,2.5×10-4,5×10-4,5×10-4,5×10-4 mg/kg. The accuracy and delicacy of these analysis methods all reached the technique demands of residue analysis of pesticide.Chapter 3:Difenoeonazole and propiconazole 30% EC was applied in paddy for two years in Changsha,Kunming and Zhejiang, the results of degradation dynamics of difenoconazole and propicondzole revealed that the degradation dynamics of difenoeonazole and propiconazole accoreded with the first class kinetics equation in paddy water, soil and straw, moreover it had high correlation. The average degradation half-lives of difenoconazole were 6.67 days in paddy water,7.81 days in paddy soil and 6.01 days in paddy straw, respectively. At the same time, the average degradation half-lives of propicondzole were 6.57 days in paddy water,7.87 days in paddy soil and 6.04 days in paddy straw.These results indicated that difenoconazole and propiconazole could be easily degradable in paddy. The final residue experiment of difenoconazole and propicondzole in paddy soil, straw, rice hull and brown rice showed that when the 21th day after the last applied,the residues of difenoconazole and propiconazole were less than the maximum residue limit(0.05 mg/kg). So difenoeonazole and propiconazole 30% EC was applied on the condition of the experiment,the safety interval period was at least 21 days.Chapter 4:The adsoprtion behavior of difenoconazole and propicondzole was studied by batch experiment with six kinds of soils tested.The results showed:The adsorption equilibrium times of difenoconazole and propicondzole were 24 hours and 6 hours, respectively. It was found that adsorption process of difenoconazole and propicondzole could be described well with Freudlich isotherm equation and there adsorption belonged to physical adsorption.The strongest adsorption occurred on the soil from Hangzhou paddy, and it took place the weakest adsorption on soil from Taiyuan. Among the main physical and chemical characters,organic matter contents played an important role in the adsorption on soils tested,more than pH value and cation exchange capacity.Chapter 5:The degradation behavior of difenoconazole and propicondzole was studied by batch experiment with six kinds of soils tested.The results showed:the degradation dynamic was different from difenoconazole and propicondzole, The fastest degradation rate occurred on the soil from Hangzhou area, the degradation half-lives of difenoconazole and propicondzole were 13.75 days,6.85 days, and the slowest degradation rate on soil from Hangzhou paddy. the degradation half-lives of difenoconazole and propicondzole were 16.27 days,8.25 days. The organic matter contents played an important role in degradation half-lives of difenoconazole and propicondzole in six kinds of soils tested. Difenoconazole and propicondzole were hardly degrade on acidity condition, but easily degrade on alkalescent condition. The degradation half-lives had a poor correlation with cation exchange capacity, it indicated that they had litter impact on degradation of difenoconazole and propicondzole.