混合施用農藥對水中非目標生物之毒性效應

Abstract

病蟲害防治的農藥在環境中具有延續性與重疊性，混合施用可同時防治病蟲害，但對於環境水體中非目標生物之毒害，尚未被廣泛研究。本研究探討混合施用農藥對於水中非目標生物水蚤 (Daphnia pulex) 、端足蟲 (Hyalella azteca) 、小球藻 (Chlorella vulgaris) 之毒性，並比較殺菌劑貝芬替 (Carbendazim) 、甲基多保淨 (Thiophanate-methyl) 與殺蟲劑益達胺 (Imidacloprid) 對於三種水中非目標生物之毒性以及不同品種間之差異。試驗皆以急毒性試驗進行，計算半致死濃度 (Lethal Concentration 50, LC50) ，並進行統計與相關性分析。在水蚤毒性試驗中，單獨暴露貝芬替的LC50為0.10 mg L-1、甲基多保淨為17.47 mg L-1、益達胺為62.17 mg L-1，混合暴露分別將益達胺無觀察危害反應劑量與最低觀察危害反應劑量和貝芬替混合，毒性不受影響，以等毒性混合貝芬替與益達胺之毒性效應為拮抗作用；等毒性混合甲基多保淨與益達胺之毒性效應為協同作用。在端足蟲毒性試驗中，單獨暴露貝芬替的LC50為0.41 mg L-1、益達胺為0.053 mg L-1、甲基多保淨為1.72 mg L-1，等毒性混合甲基多保淨與益達胺以及貝芬替與益達胺在端足蟲上的毒性效應皆為協同效應。對小球藻而言，三種農藥皆不會造成明顯生長抑制的毒性效果。結果顯示，對於貝芬替水蚤較端足蟲敏感，對於益達胺端足蟲則是較水蚤來得更加敏感，而混合後的協同效應說明了低劑量下，殺菌劑與殺蟲劑的混合仍有毒性提高的風險存在。

The mixed application of pesticides can control diseases continually, but the risk of mixture toxicity on aquatic non-target organisms is still not investigated. This research is aimed to investigate the toxic effect of fungicide and insecticide mixed application to daphnia (Daphnia pulex), amphipod (Hyalella azteca), and green algae (Chlorella vulgaris) and compare pesticides’ toxicity and aquatic organisms’ sensibility to pesticides. The exposing tests are using acute toxicity tests, calculating the lethal concentration 50 and undergo static and correlation analysis. In D. pulex’s toxicity tests, LC50 of cabendazim is 0.10 mg L-1, thiophanate methyl is 17.47 mg L-1, and imidacloprid is 62.17 mg L-1. In mixed exposing toxicity tests, toxicity of carbendazim with NOAEL and LOAEL imidacloprid is not affected. The joint toxic effect of equitoxic mixing carbendazim and imidacloprid is antagonistic effect, on the contrast, the joint effect of equitoxic mixing thiophanate methyl and imidacloprid is synergistic effect. In H. azteca’s toxicity tests, LC50 of cabendazim is 0.41 mg L-1, thiophanate methyl is 1.72 mg L-1, and imidacloprid is 0.053 mg L-1. The joint effect of equitoxic mixing cabendazim and imidacloprid is synergistic effect, also in equitoxic mixing thiophanate methyl and imidacloprid. In C. vulgaris’s toxicity tests, these three pesticides show no obvious growth inhibition effect. Results show that for carbendazim D. pulex is more sensitive than H. azteca, for imidacloprid H. azteca in much more than D. pulex. H. azteca is generally equally sensitive towards organic xenobiotics as D. pulex. The synergistic effect shows that combinations resulted in greater than additive toxicity are greatest concern in ecotoxicology.