Residue Dynamics Of Difenoconazole In Banana And Soil And Its Hydrolysis And Photolysis

Difenoconazole is a kind of triazole pesticides that is being popularized to use all over the world today. At present, the study for Difenoconazole was focused on agricultural applications, as well as aspects of its mechanism. In order to comprehensively evaluate environmental security of difenoconazole and its reasonable application node and ecological environmental restoration, the residue dynamics of difenoconazole in banana and soil, the hydrolysis and photolysis of difenoconazole were studied, them were also determined. The main conclusion obtained were listed as follows.1. The analysis method for determination of difenoconazole residue by GC was established. The recoveries ranged from 79% to 94.2%, the coefficient variation ranged from 2.14%-6.34% in banana; The recoveries were ranged from 85.7% to 98.4%, the coefficient variation ranged from 3.21%-5.64% in banana pulp. The recoveries were ranged from 77.5% to 93.4%, the coefficient variation ranged from 3.32%-5.64% in soil. The recoveries were ranged from 84.2%-98.7%,80.6%-99.0%,86.5%-98.6%, the coefficient variation ranged from 1.87%-3.88%,1.41%-5.14%,2.07%-5.03% in the buffer solutions of pH5, pH7 and pH9. The recoveries were ranged from 80.2%-91.7%,79.8%-90.4%, the coefficient variation ranged from 2.89%-6.24%,2.62%-6.64% in the pond water and river water. The method was characterized with simplicity, high sensitivity, accuracy and precision.2. A field experiment was conducted to reveal residue dynamics of difenoconazole 25% EC in banana and soil. The result shows that difenoconazole degraded rapidly in the banana, but lowly in the soil relatively. Results of the two-year experiment showed that half-life of difenoconazole in the banana was 10.24-12.91d and in the soil was 27.29-35.36d. When the banana was sprayed 3 to 4 times with 125 and 187.5 mg/kg, difenoconazole 25% EC, the last application was done 21d before harvesting, the residue of difenoconazole in the harvested banana was 0.187-0.443mg/kg,35d was 0.079-0.274mg/kg,42d was 0.019-0.059mg/kg. The residue of difenoconazole in the banana pulp was lower than banana. The last application was done 21d before harvesting, the residue of difenoconazole in the harvested banana pulp was 0.097-0.233mg/kg,35d was 0.032-0.134mg/kg,42d was only 0.031mg/kg. The residue of difenoconazole in the soil was higher than banana, when the last application was done 21d,35d,42d before harvesting, the residue of difenoconazole in the soil was 0.252-0.472mg/kg,0.118-0.296mg/kg,0.039-0.139mg/kg. According to the experiment result, the application rules are followed:in the banana growth period, the usage of difenoconazole should not above 3 times and the highest concentration should be 125mg/kg, the safe interval period should be 35 days.3. The hydrolysis of difenoconazole were studied in aqueous solutions. Results were obsevred as follow:(1) Hydrolysis of difenoconazole increased as the pH value of the solution went up, and its hydrolysis half-life in the buffer solutions of pH5, pH7 and pH9 were 315.07,11.53 and 1.33d at the temperature of 25℃. (2) Hydrolysis of difenoconazole in the buffer solutions of pH7 increased as the temperature went up. Hydrolysis half-life were 20.81,11.53,6.80 and 2.14d at the temperature of 15,25,35 and 45℃, and the temperature coefficient of hydrolysis for difenoconazole was 2.22. The mean activation enegry(E) and enthalpy(ΔH) for hydrolysis of difenoconazole was 55.53kJ/mol and 53.01kJ/mol. The activation entropy(ΔS) decreased as the temperature went up, and the mean activation entropy was-92.45 kJ/mol-k. (3) Hydrolysis half-life of difenoconazole in natural water such as pond water, river water and ultra-Pure water was 4.47,7.31 and 12.49d when the culture conditions are the same.4. The photolysis of difenoconazole in aqueous solutions and organic solvents was studied under the sunlight and the UV light. The results showed that:(1) The photolytic rate of difenoconazole was very fast in organic solvents under the UV light. The photolytic half life in the acetone, methanol, hexane were 6.92h,7.71h and 10.03h. (2) The photolytic half life was 4.98h in aqueous solutions under the UV light. However, the photolytic half life was 277.26h under sunlight. (3) The photolytic rates of difenoconazole in different aquatic solutions showed that photolytic half life was 96.27h in river water under sunlight, it is faster than in other water. Under the UV light, the half life was 4.98h in ultra-pure water it is faster than in other water.