修飾及未修飾奈米零價鐵對秀麗隱桿線蟲之毒性研究

奈米零價鐵 (Nanoscale zerovalent iron, NZVI) 具有粒徑小、比表面積大及強還原性等特性，被廣泛運用於現地土壤與地下水的污染整治中。研究指出經表面修飾過的NZVI可以提升在地下水中的移動速率，若以疏水性表面修飾劑修飾更可以提升油相污染物的移除速率。整治過程中大量的NZVI釋放於環境中，但對於NZVI在地下水中的宿命、生態環境及人體健康的衝擊尚未明朗。本研究以秀麗隱桿線蟲 (Caenorhabditiselegans, C. elegans) 為模式動物，探討未修飾NZVI，或以聚丙烯酸 (PAA)、十六烷基三甲基溴化銨 (CTAB) 及聚甲基丙烯酸甲酯 (PMMA) 修飾之NZVI在不同溶液中，以及亞鐵離子及奈米氧化鐵 (Fe2O3) 之毒性。藉由觀察線蟲的死亡率、繁殖率及體長改變以了解NZVI是否會對生物造成影響。在24小時急性暴露過程中，修飾及未修飾NZVI、Fe2+及Fe2O3對線蟲的死亡率影響不顯著。經48小時暴露後，線蟲的體長受到NZVI的影響，而Fe2+的影響更為明顯。經72小時的暴露，線蟲的繁殖率明顯受到NZVI及Fe2+影響，在高濃度暴露下 (500、750 mg/L) 線蟲無法產出後代。同時在高濃度暴露下 (500、750 mg/L) 我們觀察到體內孵化 (bag of worms, BOW) 的情形發生，可能是因為NZVI產生的Fe2+及活性氧物種(reactive oxygen species, ROS) 對線蟲造成氧化壓力使得線蟲無法產卵而使幼蟲在體內孵化。Fe2O3對體長及繁殖率沒有造成影響。此外在顯微鏡的觀察下，NZVI會附著在線蟲的外表上，而線蟲也會攝食NZVI，與體內氧氣反應產生ROS對線蟲造成毒性。雖然在短期暴露之下NZVI的毒性不顯著，但若以長期來看仍會對生物造成影響。

關鍵字

奈米零價鐵；表面修飾；秀麗隱桿線蟲；生物毒性

並列摘要

Nanoscale zero-valent iron (NZVI) has been used for the remediation of contaminated groundwater as a reductant. In order to enhance its mobility, NZVI has been surface-modified with polymers or surfactants to increase its stability in aqueous phase. Hydrophobic modifiers will also improve the affinity of NZVI with non-aqueous phase liquids. Although great amount of NZVI may be to release to the environment, the fate and ecotoxicological effects of NZVI remain unclear. In this study we investigated the toxicity of bare NZVI, polyacrylic acid (PAA), polymethylmethacrylate (PMMA) or cetyltrimethylammonium bromide (CTAB) modified NZVIs in different solution phases, Fe2O3 nanoparticles and Fe2+ on nematodes, Caenorhabditis elegans (C. elegans), by using different toxic endpoint such as lethality, reproductivity and morphological change. Under acute exposure (24 h), C. elegans were slightly affected by various types of NZVI suspensions, Fe2O3 and Fe2+. After 48h of exposure, the lengths of C. elegans were affected by all types of NZVI suspensions, as well as Fe2+ solution. After 72h of expose, the reproductivity of C. elegans was significantly decreased by NZVI suspensions and Fe2+ solution. Fe2O3 showed no toxicity to C. elegans. We have also observed the ‘bag of worms’ phenotype, which is characterized by failed egg-laying and may occur in the stressed environment which is produced by the oxidation of NZVI and the release of Fe2+ and reactive oxygen species. From the observation under the microscope, we found that NZVI particles were attached on C. elegans and inside its intestinal track which would react with internal substances and produce ROS causing the toxicity. The experimental results showed that although the stable NZVIs may not cause death in C. elegans, but it does pose adverse effects other than death, which are the potential impact of NZVI.

並列關鍵字

nanoscale zero-valent iron ； surface modification ； Caenorhabditis elegans ； ecotocixity

參考文獻

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修飾及未修飾奈米零價鐵對秀麗隱桿線蟲之毒性研究

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