The Residues And Adsorption Of Hexaconazole And Kasugamycin In Paddy Field

Hexaconazole and kasugamycin which belong to triazoles and antibiotics fungicides respectively have certain prevention effects on rice sheath blight. In order to track residual metabolism level of hexaconazole and kasugamycin after their application in paddy fields as well as the environmental pollution timely and accurately, this research explored the scientific and reasonable methods of field spraying to ensure the safe use of alcohol kasugamycin of hexaconazole. In this research, we systematically studied the residual degradation of hexaconazole and kasugamycin which are active ingredients of 15% hexaconazole and kasugamycin suspending agent used in the paddy fields. Based on this, we analyzed the adsorption behavior and its influential factors of hexaconazole and kasugamycin in 5 typical kinds of soil minerals. The results of the study are as follows:(1) Through optimization experiment, we explored and established the analysis method for residual degradation of hexaconazole in paddy fields. Paddy fields water was extracted by petroleum ether; paddy field soil and rice plant was extracted by the mixed solution of petroleum ether and acetone (1:1, v/v) and was purify by the Florisil-phase extraction after salting out; chaff, brown rice and rice straw were extracted by the mixed solution of petroleum ether and acetone (1:1, v/v) and the extracting solution was purify by the Florisil-phase extraction. Fortified recovery of hexaconazole in brown rice is 85.5%? 105.9%, with a relative standard deviation of 4.8%?5.8%, and minimum detectable amount is 1.0×10-11g. They all met the requirements of the analysis and detection technology of pesticide residue.(2)Through optimization experiment, we explored and established the analysis method for residual degradation of kasugamycin in paddy fields. The sample of paddy fields water was directly filtered by Buchner funnel; the sample of paddy fields soil was extracted by the mixed solution of methyl alcohol and water (3:7,v/v), and the extracting solution PH was adjusted to 3 by diluted hydrochloric acid; rice plant, rice straw, chaff and brown rice was extracted by the mixed solution of methyl alcohol and water (3:7, v/v), the extracting solution PH was adjusted to 3 by diluted hydrochloric acid, and was purified by silicagel column. Fortified recovery of kasugamycin in brown rice is 69.4%?94.2%, with a relative standard deviation of 4.7%?7.4%, and minimum detectable amount is of 1.0×10-9g. They all met the requirements of the analysis and detection technology of pesticide residue.(3) By the degradation dynamics and final vestigital experience, after 15% hexaconazole·kasugamycin suspending agent was applied to paddy, its active ingredient hexaconazole and kasugamycin's degradation regularity and residue levels in rice had been studied and discussed. Degradation dynamics experimental results showed that:The degradation of hexaconazole in paddy water, soil and rice plants followed first-order kinetic equation, and the half of its degradation were 2.01d?2.52d,8.61d?12.74d and 5.71d? 8.28d; After 3d drug delivery, the residual quantity of kasugamycin in paddy water, soil and rice plant was not detected, indicating that hexaconazole and kasugamycin in paddy fields belonged to easily digested pesticides. Final vestigital experimental results showed that:21d after the last time drug delivery, the residual quantity of hexaconazole and kasugamycin in brown rice was much less than MRL (0.10mg/kg) in rice (brown rice)which was tentatively stipulated in China. Therefore, the fair use of 15% hexaconazole·kasugamycin suspending agent in rice is suggested as follows:Highest preparations dosage is 50 ml/acre (750 g/ha, the active ingredient dosage is 112.50 g a.i./ha), the maximum is twice spraying quarterly, safety interval is 21d.(4) We made preliminary research on the adsorption behavior of hexaconazole and kasugamycin in 5 typical kinds of soil minerals. The result shows that the adsorption equilibrium time of hexaconazole and kasugamycin in supplied soil minerals not maintains the same, and the finally selected equilibration time is 24 hours. At the same time, four kinetic equations are used to fit the equation, showing that the pseudo-first-order kinetic equation has the lowest fitting degree, and the pseudo-second-order kinetic has the highest fitting degree; the overall trend of isothermal adsorption curves is basically the same and the adsorption capacity increases gradually with the increase of the concentration. At the same time, three isothermal adsorption models are used to fit the model, and the result shows that the adsorption model of Langmuir has the lowest fitting degree, the adsorption model of Freundlich has the highest fitting degree. The adsorption quantity of the five supplied soil mineral toward hexaconazole goes up and then goes down with the increase of PH and the adsorption quantity becomes high in weak acid, alkaline and neutral environment. The adsorption quantity of kasugamycin in acidic conditions goes down with the increase of PH. Kasugamycin resolves under alkaline condition. Raising temperature can boost the adsorption of hexaconazole and kasugamycin in montmorillonite, kaolinite, bump stone, zeolite and needle ironstone, but the effect is not dramatic. Kf, the adsorption constant of hexaconazole and kasugamycin in supplied soil minerals, has no significant relationship with the specific surface area of soil minerals, the zero point charge and the cation exchange capacity.