The Stability Of Abamectin And Emamectin Benzoate And Its Safety Evaluation On Farmland Environment

The efficacy of abamectin and emamectin benzoate is broad-spectrum and high efficiency. They can be made into mixture with most of the pesticides. They is one of the largest amount and the most widely used insecticides in China currently. Although the residual period of abamectin and emamectin benzoate is short, it is possible to occur sudden pollution accident because both pesticides are the high toxicity to aquatic organisms. So it is necessary to study the residue toxicology, environmental behavior and environmental safety of these two insecticides. In this study we set up the method of detecting abamectin and emamectin benzoate in rice, water and soil, and explored the store condition of the derivative solution and the storage stability of abamectin and emamectin benzoate standard samples, preparation and broccoli sample. It can provide a basis for more comprehensive detection of abamectin and emamectin benzoate. At the same time, we also study the degradation laws. migration and release laws, temporal and spatial distribution of abamectin and emamectin benzoate in soil and water. Based on the above results, this dissertation indepth discuss the specific measures to control abamectin and emamectin benzoate polluted the water environment.Combining the research about the photolysis products of avermectin and emamectin benzoate standard samples, the safeties of avermectin and emamectin benzoate in farmland environment were comprehensive evaluated The specific research results are as follows:1. A sensitive, stable, applicable multi-residue analytical method was established. It adapted to detection of abamectin and emamectin benzoate in rice.water and soil. The minimum detectable concentrations of in rice, water and soil samples were:1μg/kg,0.1μg/L,1μg/kg, respectively. The adding recovery rates of this method were87.34%～101.81%. and the relative standard deviation was1.40%～7.64%. It Can be used for the departments about research, quality inspection of agricultural products, environmental monitoring to detect the avermectin and emamectin benzoate in rice, water and soil.2. The light have greater impact on the derivatization of avermectin and emamectin benzoate. When derivatized avoiding light, the detection recovery rates of the avermectin were higher to50.49%,and the detection recovery rates of emamectin benzoate were higher to60.84%than derivatized under light in the same concentration. The storage time of derivative solution also have greater impact on the accuracy of the detection. At room temperature, the derivative sample solution of avermectin and emamectin benzoate must be detected in180min and360min respectively. Those can not be detected in time should be refrigerated (4℃) or cryopreserved (-20℃), refrigerated storage time can not be exceed Id, the cryopreservation time can be prolong to5days.3. In this thesis, the stabilities of avermectin and emamectin benzoate in standard samples, preparation and vegetables (broccoli) were studied. Avermectin and emamectin benzoate standard samples had different levels of degradation under refrigerated conditions. In order to ensure the accuracy and reliability of the test data, low concentration (0.1mg/L) avermectin and emamectin benzoate standard samples stored under the4℃refrigerated conditions can not be more than1month, and high concentration (100mg/L) storage time can not be more than9months under the4℃refrigerated conditions. The shelf life of the three formulations of abamectin and emamectin benzoate (EC, water emulsion, microcapsule suspension) were about7months after unsealing. The digestion half-life avermectin and emamectin benzoate in vegetables (broccoli) were1.74d to3.04d at room temperature.and4.30d to9.40d under the4℃refrigerated conditions.So it can reduce the abamectin and emamectin benzoate residues in vegetable at room temperature.and under the4℃refrigerated conditions.Although it can maintain the freshness of vegetables that stored in refrigerated (4℃), the digestion of pesticide residues in vegetables slow down at the same time. The research samples of avermectin and emamectin benzoate must be storaged at-20℃,and the storage time was not more than4months.4. The persistence of abamectin and emamectin benzoate in three formulations in soil and water were microcapsule suspension> emulsion in water> emulsifiable concentration. When we use the microcapsule suspension of avermectin and emamectin benzoate, which can prolong the efficacy period, and improve the control effect.5. The photolysis results of avermectin and emamectin benzoate standard solution (acetonitrile) showed that:the photolysis products of avermectin and emamectin benzoate standard solution (acetonitrile) were C25H34O5(414). C1H22O7(278), C24H35O8(451) C17H33O4(301), C15H29O4(273), C19H21O6(345), C24H37O4(389), C16H28O3(268), C39H60O13(736), C17H29O6(329). According to the characteristics of the molecular structure and chemical bonding, under sunlight and high-pressure mercury lamp. the photolysis ways of avermectin and emamectin benzoate were molecular C14, and C21carbon-carbon and carboxyhemoglobin key fracture, C8and C17macrocyclic key fracture, G4and C13oleandrosyl fracture, C8a bit on the heterocyclic oxidation, further oxidized to generate hydroxyl and generate carbonyl at last, the molecular C33’ and C3" dealkylation and so on..6. The oscillation balance method was used to research the adsorption and desorption in three kinds of soils. The results showed that the adsorption equilibrium time of abamectin and emamectin benzoate in three kinds of soils was about1hour. The adsorption capacity sequence of three kinds of soils to abamectin and emamectin benzoate was black soil> red soil> paddy soil. However, The order of three kinds of soils desorbed abamectin and emamectin benzoate was red soil> paddy soil> black soil.The migration and release laws of abamectin and emamectin benzoate in paddy water and soil were researched. Avermectin and emamectin benzoate which were applied to paddy water would migrate to the soil gradually. The maximum content of avermectin in the soil appeared on the third day after application, and the maximum content of emamectin benzoate appeared on the first day after application. When avermectin and emamectin benzoate was applied in paddy soil, avermectin and emamectin benzoate in soil could release to paddy water after irrigation. The maximum content of avermectin in paddy water appeared on the second day after irrigation, and the concentration was0.0340mg/L. The maximum content of emamectin benzoate in paddy water appeared in the fifth hours after irrigation, and the concentration was0.0132mg/L. At the same original effective concentration. the concentration of avermectin in water was higher than emamectin benzoate. after7hours of irrigation. The concentration of abamectin and emamectin benzoate in paddy water at migration test was higher than the release test.7. Through further researchs of the temporal and spatial distribution of abamectin and emamectin benzoate in paddy water and soil. The results showed that avermectin and emamectin benzoate diffused from the surface water to lower water, and migrated to soil, when spraying on the surface of the water directly. On soil treatment, avermectin and emamectin benzoate was mainly distributed in the soil layer, and avermectin and emamectin benzoate in soil would release to the paddy water gradually. Spraying in two ways, within24hours, the distribution of avermectin and emamectin benzoate in paddy water was uneven. Abamectin and emamectin benzoate distribution is concentrated at the top4cm deep paddy soil. It was indicated that avermectin and emamectin benzoate were adsorbed by soil, would not cause the pollution of groundwater. Because the distribution of avermectin and emamectin benzoate in paddy water was uneven, and24hours after application, when drainage is needed to set the height of the drainage weir for3cm, the emissions of paddy water for70%(water depth of10cm), and the reduction rates of avermectin and emamectin benzoate emission for33.38%to39.32%, It can reduce avermectin and emamectin benzoate from paddy water to the other water environment.In the same pesticide concentration, when the drainage weir height was0cm,3cm,7cm,9cm,spraying the avermectin and emamectin benzoate on the paddy soil could reduce the emission of them than spraying on the surface of paddy water, the reduction rates of avermectin were:78.49%.86.54%,94.88%,98.44%at each drainage weir.and the reduction rates of emamectin benzoate were:74.16%,84.31%,94.26%,98.29%at each drainage weir. When we elected avermectin and emamectin benzoate to control the diseases and insect pest of rice, we sprayed pesticides at the field without water, and then irrigated after spraying1h. It not only can ensure the effect of pest control, but also can better prevent pesticides to flow from paddy water to other aquatic environment.