以模擬生態系統探討殺菌劑待克利在水田環境中消退與分佈

Dissipation and distribution of difenoconazole in a model paddy field ecosystem

待克利為一系統性之三唑類殺菌劑，國內登記於防治水稻紋枯病。本研究應用“半開放式模擬生態系統”，探討待克利（difenoconazole）施用於台灣地區水田環境下的分佈，及在田水、土壤及稻株中之降解情形。一期稻作種植後56天連續3次施用待克利24.9 %乳劑商品8.3 g/ha與24.9 g/ha，最後一次施藥後定期採集土壤、水體及植株樣品分析待克利殘留量。試驗結果顯示待克利在本地水田土壤、水體及植株中之降解反應方程式符合化學動力學的一階反應（first order kinetics），在水田土壤、水體及植株之消散半量期（DT_（50））分別為19-23天、9-10天及6-9天。待克利施用後在環境主要分佈於水域中，水稻植株上濃度明顯高於環境濃度，依推薦使用量施用待克利，收獲後之稻穀，碾製成糙米後，糙米中待克利殘留量為0.08 mg/kg。

"Difenoconazole (3-chloro-4-[4-methyl-2-(1H-1,2,4-triazol-1-ylmethyl)-1,3-dioxolan- 2-yl] phenyl 4-chlorophenyl ether) is a systemic triazole fungicide and is registered for the control of rice sheath blight in Taiwan. The degradation of difenoconazole in flooded soils, water, and rice plants was studied with a semi-open model ecosystem under local conditions. Fifty six days after the rice was planted, rice plants were separately treated 3 times with 24.9 % difenoconazole of 8.3 g/ha and 24.9 g/ha, respectively. Water, soil, and rice plants were sampled and analyzed during rice growing periods, and a hulled rice sample was also sampled and analyzed after harvesting. The results showed that difenoconazole degraded in flooded soils, water, and rice plants. The degradation equations were in accordance with first-order kinetics. DT_(50) values of difenoconazole in soils, field water, and rice plants were 19-23, 9-10, and 6-9 days, respectively. The concentration of difenoconazole in rice plants was higher than those in the other environmental compartments. The residue of difenoconazole in the harvested hull rice sample was 0.08 mg/kg with the recommended application rate and method."