Study On The Residual Behavior Of Tricyclazole And Propiconazole In Paddy And Soil

Tricyclazole and propiconazole are triazole fungicide and are widely applied in paddy because oftheir high efficacy on Pyricularia oryzae and Rhizoctonia solani. The residual levels and dissipation rateof tricyclazole and propiconazole in rice field ecosystem were investigated in field experiment done inTianjin, Jilin and Zhejiang during summer season in2011and2012. The results of propiconazole andtricyclazole in the rice crops and the soil is determined can provide evaluation for safe use regulation for525g/L tricyclazole&propiconazole SC in paddy field. These would contribute to protect agriculturaleco-environment and to assure the safety of human beings and animals. The main results are asfollowing:1. HPLC-DAD analytical methods for the residues of tricyclazole and GC-ECD analytical methodsfor propiconazole in rice, soil and water were developed. Tricyclazole residues were dealt withQuEChERS procedures followed by HPLC-DAD. Propiconazole residues were dealt with QuEChERSprocedures, and determined by GC-ECD after evaporating and reconstituting by methyl alcohol. Theresults showed that the average recovery rates of tricyclazole and propiconazole in samples were in arange of84.22%–106.09%and77.13%–108.19%, with their relative standard deviations of0.43%–5.7%and0.43%–5.7%. The minimum detectable limit of tricyclazole and propiconazole was1×10^-13g and1×10^-13g. The minimum detectable concentration of tricyclazole is0.2mg/kg in allsamples.The minimum detectable concentration of propiconazole is0.02mg/kg in rice straw and ricehull,0.002mg/kg in other samples. This method is quick, easy, cheap, effective, rugged and safe, whichare within the accepted range for residue determination.2. The residual levels and dissipation rate of tricyclazole and propiconazole in rice plant, soil, andwater were studied by a two-year and three-field experiments with the application of525g/Ltricyclazole&propiconazole SC in Tianjin, Jilin and Zhejiang. The rice, soil and paddy water weretreated with a dosage of945ga.i./ha. The dissipation process of propiconazole and tricyclazole followthe first-order kinetic reaction in plant, water and soil in the studies. The half lives of tricyclazole andpropiconazole in rice plant, soil and paddy water are3.82d⁴.07d and3.19d³.87d,6.54d⁷.53d and5.50d⁸.56d,6.60d¹2.6d and7.87d¹5.1d, respectively, which are all less than30days, so theybelong to a low residue and degradable fungicide.3. The final residue experiments were performed with two dosages in Tianjin, Jilin and Zhejiangeach year, recommendation and1.5times of the recommendation dosage. Both high and low applicationrates were used in two or three applications （7day interval each）, and the last spray was applied30,40or50day before harvest. The results showed that pesticide residues increase with the increasingfrequency and amount of pesticide application as well as increasing frequency of acquisition，themaximum residue of tricyclazole and propiconazole were0.223mg/kg and0.081mg/kg in brown riceafter30days of last application, respectively. They are both lower than the MRL for tricyclazole andpropiconazole in rice （2mg/kg and0.1mg/kg） in the National food safety standard “Maximum residuelimits for pesticides in food”, respectively. 4. The distributions of tricyclazole and propiconazole in rice were studied. The results showed thatthe residues of tricyclazole and propiconazole in rice were the lowest. As the main residualaccumulation parts, the rice hull and plant bore over90.9%of the pesticide residue.