益達胺、陶斯松和亞托敏對兩種環境底棲指標生物(端足蟲和搖蚊)之影響

Abstract

近年來農藥的使用日趨頻繁，人們為了改善生活之品質、增加作物產量或環境衛生需求等原因，將大量的化學用品應用在生活中，這些化學用品最終幾乎都會進入水體，對水中的非目標生物造成影響，化學藥品在環境中之流佈和殘留的能力均是造成毒性高低的因子。以指標生物進行急毒性及慢毒性試驗為評估化學品在環境中之毒性的重要方法之一。 淡水生態系中富含多種生物，這些生物的棲息地可分為水體及底泥，目前我國用於檢測水生生物毒性之指標通常採用水蚤及魚類，但兩者皆為代表水體之生物，顯示水體殘留農藥對於底棲生物毒性資料的缺乏。搖蚊和端足蟲均為各地常見的底棲生物，端足蟲廣泛的分布在淡水生態系中，該物種為生態系中之分解者，且可做為多種中高階消費者的食物；搖蚊為淡水生態系中最常見的昆蟲之一，且其在不同的生命階段均對於不同層級的消費者造成影響，此兩種生物對於食物鏈和生態系中都十分重要。因搖蚊為完全變態昆蟲，生命週期較短，且其慢性終點 (羽化率、生質量和成蟲雌雄比) 較容易觀察，因此近年來成為新興之底棲指標生物。此試驗分別以三種臺灣常見農藥，益達胺、陶斯松和亞托敏對於搖蚊和端足蟲進行急毒性試驗，並參考急毒性之LC50進行慢毒性試驗。試驗期間觀察其對於搖蚊和端足蟲於短期之致死效應濃度和搖蚊在長期暴露中所導致的羽化成功率和雌雄比之改變，並使用Probit計算各個終點的效應濃度。 結果顯示，和美國環境保護局 (USEPA) 之生物毒性資料行比較，益達胺、陶斯松和亞托敏對於水生無脊椎生物均屬於劇毒。和臺灣主要河川所檢測出的殘留濃度比對後結果顯示，三種藥物在環境水體中的殘留量均未到達本次試驗搖蚊和端足蟲的急毒性LC50；而益達胺和陶斯松在環境水體中的殘留量則可能對於搖蚊的羽化率及雌雄比產生風險。

In recent years, application of pesticide has been more common. For approving qulity of life, increasing the production and requirement of environment, these chemical materials have been used frequently and they almost were transported into the water ecosystem. Acute and chronic toxicity test of indicator organisms is an important way to assess the environmental risk of chemical materials. There are many creatures that living in water ecosystem. Their main habitats include water body and sediment. The organisms that are used in water ecosystem toxicity test in Taiwan are fish and daphnia, but they can only represent the non-target organism of water body. Chironomidae (Chironomus sp.) and amphipod (Hyalella azteca) are common sediment organism. As a decomposer, amphipods distribute widely in the fresh water in the world. As a predator, these creature are preyed by consumers from several levels, that makes amphipod become a irreplac eable species. Chironomidae is one of universal insect in water ecosystem that can effect different level of preyers in different life stage. Charactersistic that being a holometabolous species, short life cycle and observable chronic endpoint (emergence, biomass and sex ratio of adults), makes it become a rising indicator organism of sediment. These two species are explosed in imidacloprid, Chlorpyrifos and azoxystrobin for toxicity test. Lethal and sublethal (emergence and sex ratio) endpoint are observed during test duration. Half lethal concentration (LC50) of imidacloprid, Chlorpyrifos and azoxystrobin to H. Azteca are 24.4, 0.38 and 513.4 μg L-1, respectively, to Chironomus sp. are 19.4, 0.27 and 237.7μg L-1, respectively. Half effective concentration (emergence) of imidacloprid, Chlorpyrifos and azoxystrobin to Chironomus sp. are 0.107, 0.062 and 128.14 μg L-1, respectively. Sex ratio effected concentration (SEC) of three pesticide to Chironomus sp. are 0.074, 0.053 and 144.85 μg L-1, respectively. Comparing with toxicity data of water ecosystem from USEPA. Three pesticides are classified as high toxic for water organisms. Chironomus sp. that exposed in imidacloprid and azoxysrobin may affected during emergence stage and Chlorpyrifos may cause some impacts during pupa stage. Comparing data of pesticides residues in Taiwan’s main rivers with test data, concentration of residues are lower than LC50 of two species in these test. But concentration of imidacloprid’s and chlorpyrifos’ residues in river are higher than EC50 of emergence and SEC that shows these two pesticides environment may cause influence to non-targeted organisms in long run.