Study On Degradation And Residue Of Tricyclazole In Ecological Environment Of Paddy And Its Hydrolysis

Tricyclazole is a kind of fungicide within the suction. It was always used in preventing and curing rice blast. Tricyclazole came to China for a long time. The studying on tricyclazole almost focus on the capability of preventing and curing the rice blast. But little information was availabled about its hydrolysis. In this paper, the residue degradation of tricyclazole in paddy has be studed; and the effect of tricyclazole hydrolysis has be studed on the pH, temperature, surface active agents and the presence of inorganic salt. It has a very great practical significance to promote and reasonably use the pesticide in our country, and to evaluate the safety after using. The major results were obtained as follows:(1) Under natural conditions in China, the degradation of tricyclazole in ecological environment followed the chemical reaction kinetic equation. in and three test points test The results of the test in Hunan Changsha, Guangxi Nanning, Zhejiang Hangzhou in 2008 and 2009 showed that:the degradation half time of tricyclazole was 7.87 d～9.00 d in the paddy water, with an average half-time of 8.33 d; the degradation half time was 10.56 d～11.42d in the paddy soil, with an average half-time of 10.93 d; in the degradation half time was 7.48 d～8.11d in rice plants, with an average half-life of 7.81 d.(2) The final residue indicated that when the rice plant was sprayed 2 to 3 times with 25% tricyclazole in the dosage of 1500 g/hm2 and 2250 g/hm2, and the last application was done at 7,14 or 21 days before harvesting, when the last application was done at 21 days before harvesting, the residues of tricyclazole in paddy soil ranged from 0.073 to 0.219 mg/kg; the residues of tricyclazole in rice plant changed from 0.557 to 1.198 mg/kg; the residues of tricyclazole in rice hull was from 0.736 to 1.874 mg/kg; the residues of tricyclazole in rice changed from 0.094 to 0.366 mg/kg. The residues of tricyclazole in rice were lower than 1.0 mg/kg. It suggested that the MRL of tricyclazole in rice was 1.0 mg/kg.(3) The hydrolysis rates of tricyclazole were different at different pH values. The hydrolysis rate of tricyclazole in alkaline solution was lower than in neuter solution or acid solution. The results showed that, when pH=3, the half-life of tricyclazole hydrolysis was 64.78 d; when pH=5, the half-life of hydrolysis was 56.82 d; when pH=7, the half-life of hydrolysis was 47.80 d; when pH=9, the half-life of hydrolysis was 41.26 d; when pH=11, the half-life of hydrolysis was 37.67 d.(4) The hydrolysis rate of tricyclazole accelerated with the rise of temperature. When the temperature was 15℃, the hydrolysis half-life of tricyclazole was 100.46 d. When the temperature was 25℃, the hydrolysis half-life was 60.80 d. When the temperature was 35℃, the hydrolysis half-life was 30.01d. Even the temperature increased 10℃, then the hydrolysis rate of tricyclazole accelerated 1.84 times as much as that before.(5) Different surfactant had dfifferent effect on the hydrolysis rate of tricyclazole. The anionic surfactant (SDBS) could increase the speed of the hydrolysis of tricyclazole. The cationic surfactant (CTAB) could decrease the speed of the hydrolysis of tricyclazole. The nonionic surfactant (TW-80) did not have special influence on the hydrolysis of tricyclazole.(6) Added strong acid and strong base salts (NaCl, KCl, CaCl2, NaNO3) into tricyclazole agueous. Due to salting-out effect which restrained hydrolysis of tricyclazole, when the concentration of NaCl, KCl, CaCl2, NaNO3 changed from 0 to 1 mol/L, the hydrolysis half-life of tricyclazole increased 0.88%,7.55%,11.76%, 31.04%, respectivily. Added strong base and weak acid salt (NaHCO3) into tricyclazole's agueous solution, because dissociation of this salt can make water alkaline, it could accelerate its hydrolysis. When the concentration of NaHCO3 ranged from 0 to 1 mol/L, the hydrolysis half-life of tricyclazole decreased 75.47%.