奈米氧化鋅之陸域生態毒性—以福山萵苣、非洲大蝸牛、秀麗隱桿線蟲為例

Abstract

奈米氧化鋅 (zinc oxide nanoparticles, ZnO-NPs) 因具有良好的光催化、抗UV、抗菌等能力，廣泛的應用在工業、農業、民生用品中。每年有大量之ZnO-NPs持續排放至環境生態系統。土壤為環境汙染物的累積終點之一，然而現有毒理研究大多探討水域生態，陸域生態相關毒理資料相對缺乏。本研究分為兩部分：(1) 利用福山萵苣 (Lactuca sativa) 以及非洲大蝸牛 (Achatina fulica) 作為目標生物，探討食物鏈傳輸ZnO-NPs對於生物體之生物累積、傳遞速率及毒性效應；(2) 利用秀麗隱桿線蟲 (Caenorhabditis elegans) 探討土壤慢性暴露ZnO-NPs所造成之毒性影響，並且進行陸域環境風險評估。第一部分研究結果顯示，幼苗期福山萵苣土壤暴露8天 1000 mg/kg ZnO-NPs，不會影響其生物質量 (biomass) 及根長度；而在暴露100 mg/kg以上的ZnO-NPs會從根部吸收，並轉移分布到葉子中。在土壤-萵苣-蝸牛之食物鏈實驗，餵食非洲大蝸牛經生長在100 mg/kg以上ZnO-NPs之福山萵苣葉子，ZnO-NPs會經由食物鏈傳輸累積在非洲大蝸牛體內。此外，實驗結果顯示ZnO-NPs主要累積於非洲大蝸牛的內臟，並且會造成DNA損傷。在毒理動力學模型 (toxicokinetic model) 的參數中，BAF > 1；在損傷評估模型 (damage assessment model) 的參數中，隨著ZnO-NPs濃度及暴露天數增加，會造成非洲大蝸牛之損害累積。第二部分研究結果顯示，C. elegans土壤慢性暴露ZnO-NPs，隨著濃度增加，會顯著抑制其生長及生殖能力。在環境風險評估結果中，發現預測之ZnO-NPs環境濃度不會對C. elegans造成毒性風險 (RQ < 1)。總結本研究結果，ZnO-NPs透過食物鏈傳輸會對非洲大蝸牛造成基因毒性，因此在陸域生態中ZnO-NPs可能仍具有潛在風險。

ZnO nanoparticlees due to their good photocatalysis, anti-UV, and antibacterial properties, they have been widely used in industrial, agricultural, and residential products. A large amount of ZnO-NPs continue to entering into the environmental ecosystem. Soil is one of the destinations of environmental pollutants. Comparing with the aquatic environments, less research focus on the terrestrial ecosystem. This study consists of two parts：(1) Lactuca sativa and Achatina fulica were used as target organisms to explore the bioaccumulation, trophic transfer, and toxicity of ZnO-NPs.(2) Chronic soil exposure to ZnO-NPs in Caenorhabditis elegans, and to conduct environment risk assessment. For part 1, the results showed that soil exposure of 1000 mg/kg ZnO-NPs for 8 days, ZnO-NPs did not affect the biomass and root length of L. sativa at the seedling stage. Above 100 mg/kg, ZnO-NPs were absorbed from the roots and transported to leaves. In the soil-lettuce-snail food chain experiments, A. fulica with feeding L. sativa leaves which were previously exposed to 100 mg/kg or above ZnO-NPs caused bioaccumulation through trophic transfer. In addition, ZnO-NPs mainly accumulated in the internal organs of A. fulica and caused DNA damage. In TK model, BAF > 1；In DAM model, ZnO-NPs caused damage in a dose and time dependent manner. In the second part of the study, the results showed that chronic exposure to ZnO-NPs inhibited the growth and reproduction of C. elegans in soil in a dose dependent fashion. Moreover, the predicted environmental concentration of ZnO-NPs did not pose a potential risk to C. elegans (RQ <1) in soil. Taken together, ZnO-NPs may cause genotoxicity to A. fulica through trophic transfer, thus ZnO-NPs may still have potential risks in terrestrial ecosystem.