Dissipation Of Carbendazim、Chlorothalonil And Chlorpyrifos In Vegetables And Soil Inside And Outside The Greenhouse

The worm and humidity conditions in greenhouse cause substantive proliferation of plant diseases and pests which result in extensive and frequent applications of pesticides. Based on the survey of pesticide applications in greenhouse production of vegetables, two fungicides (carbendazim and chlorothalonil) and one insecticide (chlorpyrifos) were selected as target pesticides in this study. The analytical methods for the determination of carbendazim, chlorothalonil and chlorpyrifos in pakchoi, tomato, cucumber and soil were primarily established, respectively. The dissipation characteristics of these pesticides on pakchoi, tomato, cucumber, and in soil were investigated inside and outside the greenhouse. The accumulation possibility of these pesticides in soil and the residual dynamics of the major metabolite of chlorothalonil were also examined in the greenhouse after their successive applications. The main results are summarized as follows:A survey concerning formulation, content, application dosage, application frequency and interval of pesticides used in greenhouse production of vegetables, and preharvest interval was performed in Nanjing, Jiangsu and Jiaxing, Zhejiang, respectively. The data showed the following characteristics:various pesticide(s) are frequently applied and thus large amount of pesticides are introduced into the system; most of the farmers are inscience in the applications and risks of pesticides. The highly frequent application of various pesticides in the greenhouse production of vegetables might lead to a potential threat to vegetable safety and soil health. The risk analysis of pesticide applications indicated that carbofuran, chlorpyrifos, carbendazim, phorate, dichlorvos, mancozeb (ethylene thiourea), acephate (methamidophos), chlorothalonil, zineb (ethylene thiourea) and fenvalerate are the potential high risk pesticides for the greenhouse production of vegetables.The quantification methods of carbendazim, chlorothalonil and chlorpyrifos in pakchoi, tomato, cucumber, and soil were established by high performance liquid chromatography (HPLC) or gas chromatography (GC). The recoveries of carbendazim at levels of0.05-150mg kg-1in the vegetables and soil ranged from70.9%to91.6%with relative standard deviation (RSD) of1.2%-10.9%, and the recoveries of chlorothalonil at levels of0.01-300mg kg-1ranged from70.4%to97.3%with RSD of0.3%-10.4%, and the recoveris of chlorpyrifos at levels of0.01～100mg kg’1ranged from79.8%to104.5%with RSD of0.65%-9.8%. The detection limit of carbendazim was0.05mg kg-1, and those of both chlorothalonil and chlorpyrifos were0.01mg kg-1.The dissipation of carbendazim, chlorothalonil and chorpyrifos in pakchoi, tomato, cucumber, and soil was fitted to the first-order model. The hermetic environment of greenhouse and seasons change altered dissipation behavior of these pesticides in the vegetables and soil. The dissipation rates of these three pesticides in the vegetables and soils were much slower in the greenhouse than those in the open field. Furthermore, their dissipation rates were much slower in the winter than those in the summer.The residual amounts of three pesticides in the soil increased with their increasing application concentrations under the same application frequency. An obvious accumulation of carbendazim, chlorothalonil and chlorpyrifos was observed with application times. The major metabolite4-hydroxy chlorothalonil of chlorothalonil could accumulate in the vegetable soil with increasing application times or dosages.