Study On The Residue Behavior Of SYP-1620 And Its Photo-degradation In The Paddy Field

It was researched the degradation behavior of pesticides and its laws in the natural environment and crop that was very important for evaluation its ecological environment safety, and can offer details for its scientific and rational use, and established standards. Photochemical degradation is an important way of degradation in the natural environment, many research has shown that the photochemical degradation of pesticides not only bore directly on the its use effects,but also impacted the results of its environmental impact assessment. SYP-1620 is strobilurin Fungicides, which has good compatibility with environment,it belongs to low toxicity and persistent pesticides.Therefore studying its photochemical degradation and residual degradation behavior in the paddy field has important practical significance. This paper researched the residual degradation of SYP-1620 in the paddy field under different natural environment. and under high-pressure mercury lamp, the influence of the different concentrations of SYP-1620, different kinds of organic solvents, different pH value, different kinds of photocatalyst on its photochemical degradation were probed also. The major findings are as follows:(1)Under the condition of our natural environment, the degradation process of SYP-1620 in the paddy field accords to the chemical reaction series. At test points of Hunan, the average half-life of degration SYP-1620 in the paddy water, soil, straw, were 8.51d,8.31d and 6.41d respectively; at test point of Hangzhou, were 7.5d,12.5, and 7.3d respectively; at test point of Guangxi were 6.4d,8.5 and 7.5d respectively. Its degradation rate decreaseed by rice straw, water, soil.(2)After 21d of the last pesticide application, the residues of SYP-1620 in the paddy soil, rice straw, rice hull, brown rice at three points in Changsha, Hunan, Nanning, Guangxi, Hangzhou,Zhejiang were ranged from 0.082mg/kg to 0.267 mg/ kg, from 0.215 mg/kg to 0.514 mg/kg, from 0.323 mg/kg to 0.673 mg/kg, from 0.192 mg/kg to 0.430 mg/kg respectively. Therefore, this paper suggests that the provisional maximum residue limits (MRL) of SYP-1620 in the brown rice is 0.5mg/kg in China by referring to the provisions of French. (3)By conducting photolysis experiments in the pH value of the aqueous solution for the 3.0,4.0,5.0,7.0,9.0,11.0, it arrived at a conclusion that the photochemical degradation rate of SYP-1620 decreased with the increase of pH value. This suggested that SYP-1620 is relatively stable in alkaline, while it is to the benefit of photochemical degradation in acibic.(4) The photodegradation rate of SYP-1620 in various organic solvents was acetate> acetone> ethanol> methanol> petroleum ether in sequence.(5) Different concentrations of photo-oxidation all have catalytic effect on the photochemical degradation of SYP-1620. With the increasing concentration of photo-oxidation catalyst, the catalysis increased. The catalysis of different kinds of photo-oxidation catalysts was H202>TiO2>Fe2O3 in sequence.(6) Na2SO4, K2S04 play a catalytic role on photolysis of SYP-1620. With the concentration of K2SO4 increased, it the impacted on photolysis of SYP-1620 increased, while the K2SO4 plays a greater effect than Na2SO4.KNO3, KH2PO4 inhibited the photolysis. With the concentration of KNO3, KH2PO4 increased, it impacted on photolysis of SYP-1620 decreased, while the KH2PO4 plays a greater effect than KNO3...