Study On The Distribution And Degradation Of Pesticide Chlorothalonil In Grape Plants And Soil

In recent years,which the problem of pesticide residues has been a hot topic.With the growing area fruits and vegetables of various,it’s becoming more and more serious about the pesticide residues.Many agricultural products were detected a large number of pesticide residues.It threatens human health and safety pollutes of environment in great level.Therefore,in this paper,Chlorothalonil was used as research material to study the residual characteristics and degradation mechanism of pesticides in grapes and their surrounding environment.Systematic research,including:（1）Established the optimization of analytical methods for the determination of chlorothalonil residues in grapes,soil and water（2）Studying on Distribution and Degradation of Chlorothalonil in Grape Plants and Soil（3）It’s considered that the adsorption,Degradation and Leaching Migration of chlorothalonil in Different Soils.The main purpose that this thesis is to study the distribution,degradation and leaching characteristics of chlorothalonil in grape plants and their surrounding environment,it’s provide that the practical scientific of theoretical basis and rational useful chlorothalonil pesticides in fruits and vegetables in the future.In article,a solid-phase microextraction GC/MS method was established in the first,in order to determine of pesticide residues in grapes,soil and water.The results showed that the optimum conditions for solid-phase microextraction were:a 65μm PDMS/DVB extraction head,which was extracted at 50°C for 10 min at 600 r·Min^-1,10%NaCl concentration.In the range of 0.02².00μg·mL^-1,the peak areas of several organochlorine pesticides showed a good linear relationship with the corresponding concentrations,and the correlation coefficients were all greater than0.9992.Within the range of different concentrations,the target analyzes of recovery rate were in 83.3%⁹3.4%,which the relative standard deviation was in 2.5%⁸.4%.It’s suitable that the requirements for the detection of pesticide residues in fruit products,meanwhile,not only can reduce the operation time and detection costs,but also provide a reference for pesticides in fruit,soil and water pesticide residues in the future.Field experiments were conducted that study the distribution and degradation characteristics of chlorothalonil in grape fruits,leaves,and soil.The results showed that under different concentrations of treatment,one spray and several samplings of chlorothalonil in fruits,leaves,and soil of grapes were degraded.The rates are all faster in the early stage and gradually slower in the later stages.With the increase of the application concentration,the half-life and residue are also increasing.Respectively,the half-lives of fruits,leaves and soil are 8.30 to 12.72 days,10.07 to12.83 days,and 15.16 to 17.11.,the leaves were the main pesticide residues;after 7days of application,the residual amount of chlorothalonil in grape fruits was lower than that of chlorothalonil at MRL（0.5 mg·kg-1）,referring to the maximum residue limit set by China.The use of chlorothalonil on grapes was conducted at a safety interval of 7 days.The application of the drug was performed at different concentrations.The dietary intake risk values of all women were slightly higher than those of men;however,the risk quotient was within the acceptable range of the population.Finally,in order to study the adsorption,degradation,and leaching of chlorothalonil in different soils,the physicochemical properties of the soil indicate that the pH and cation exchange capacity may be the key factors affecting the adsorption capacity of these two soils.The factors that affect the two vary in the main component..The adsorption kinetics experiments showed that the adsorption constants of clay and sand were 6.7158 and 1.2568,respectively,indicating that the adsorption capacity of clay was more than the sandy soil.It showed that the degradation kinetics were consistent with the first-order kinetic equation under different concentrations of application which the experiment of soil residue and degradation in different simulated soils.The degradation rates of the two soils were T1>T2>T3.The half-life changed with the increase of the application concentration.The half-lives of clay were 9.79 d,9.12 d,and 12.83 d,respectively,and the half-lives of sand were 15.07 d,23.90 d,and 27.07 d,respectively.The experiment of soil leaching and migration changes showed that the chlorothalonil content in the leachate of the two soils was lower than the in the column,which most of them remained in the soil column,0¹0 cm（topmost）.The highest residue indicates that chlorothalonil is not easy to migrate downward with the leaching solution.The depth of soil layer is extremely significantly related to the residual amount.Therefore,the residual amount decreases with the increase of soil depth.To sum up,in order to reduce the pollution of pesticides to the environment and groundwater,the useful of the pesticides must be applied scientifically at the recommended dose.