以模擬生態系統探討殺菌劑亞賜圃在水田環境中之命運及其消散趨勢

Dissipation and distribution of isoprothiolane in a model paddy field ecosystem

亞賜圃為系統性含硫雜環化合物殺菌劑，國內登記於防治水稻稻熱病。本試驗應用“半開放式模擬生態系統”，研究亞賜圃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。二期稻作種植後於抽穗期施用亞賜圃40 %乳劑1 L/ha與3 L/ha，施藥後定期採集土壤、水體及植株樣品分析亞賜圃殘留量。結果顯示亞賜圃在水稻田土壤、水體與植體中會發生降解，以化學動力學的一階反應方程式估算，在水田土壤、水體及植株之消散半量期（DT_（50））分別為11-30天、12-14天及5-6天。亞賜圃施用後在環境中主要分佈於水域，植株上濃度明顯高於環境濃度，依推薦使用量施用亞賜圃，施藥42天後收獲之稻穀經碾製成白米後，白米中亞賜圃殘留量為0.13 mg/kg。

"Isoprothiolane (di-isopropyl 1,3-dithiolane-2-ylidenemalonate) is a systemic thiolane fungicide and is registered for the control of rice blast in Taiwan. The degradation of isoprothiolane in flooded soils, water, and rice plants was studied in a semi-open model ecosystem under local conditions. In the heading stage, rice plants were separately treated with 40% isoprothiolane at 1 and 3 L/ha. Water, soil, and rice plants were sampled and analyzed during the rice growing periods, and rice samples was also taken and analyzed after harvesting. The results showed that isoprothiolane degraded in flooded soils, water, and rice plants. DT50 values for the dissipation of isoprothiolane in soils, field water, and rice plants were 11~30, 12~14, and 5~6 days, respectively. The concentration of isoprothiolane in rice plants was higher than those in the other environmental compartments. The residue of isoprothiolane in the harvested rice sample was 0.13 mg/kg with the recommended application rate and method."