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標題: | 自來水配水管材釋出之奈米二氧化鉛對青鱂魚的生物有效性及毒性效應評估 The Bioavailability and Toxicity Assessments of Lead Dioxide Nanoparticles From Drinking Water Distribution System in Medaka (Oryzias Latipes) |
作者: | Chun-Wei Chiang 江峻蔚 |
指導教授: | 陳佩貞 |
關鍵字: | 奈米二氧化鉛,青鱂,魚,生物有效性,急毒性試驗,抗氧化酵素活性分析,活性氧物種含量分析,神經毒性, nanoscale lead dioxide (nPbO2(s)),medaka (Oryzias Latipes),bioavailability,acute toxicity test,antioxidant enzymes activity,reactive oxygen species,neurotoxicity, |
出版年 : | 2013 |
學位: | 碩士 |
摘要: | 奈米二氧化鉛 (nPbO2(s)) 為加氯消毒之自來水系統中新發現的鉛管腐蝕產物,能由鉛管內壁直接脫落或溶解釋出可溶性鉛離子 (Pb2+(aq)) 而提高自來水中的鉛含量。研究指出鉛為有毒金屬及人類可能致癌物,長期攝取 Pb2+(aq) 會導致許多慢性疾病,其毒性機制多元而複雜,然而 nPbO2(s) 的生物毒性及對人體健康與生態安全的衝擊目前為止一無所知。本研究藉由粒徑分析及沉降試驗探討 nPbO2(s) 在水溶液隨時間的聚集沉降行為,並分析 nPbO2(s) 在不同水中基質 (如可溶性有機質,DOM) 存在下的顆粒行為及溶解性變化,藉此探討 nPbO2(s) 在水域生態中之宿命及生物有效性等議題。本研究亦利用日本青鱂魚 (Oryzias latipes) 幼魚為模式生物,評估 nPbO2(s) (0.25-25 mg/L) 及 Pb2+(aq) (0.25-2.0 mg/L) 對生物之毒性效應。研究結果顯示,相較於胚胎培養液 (ERM,高離子強度) 或去氯自來水 (TW,低離子強度) 溶液,nPbO2(s) 在去離子水 (DI) 中的團粒較為分散 (~100 nm) 及顆粒懸浮性較佳;添加腐植酸 (HA, 0.4 mg/L) 於 ERM 或 TW 溶液中則可有效地懸浮 nPbO2(s) ,表示影響 nPbO2(s) 聚集沉降行為與水中離子強度或 DOM 含量高低有關,但添加 HA 也會造成 nPbO2(s) 還原溶解釋放出 Pb2+(aq)。在生物有效性的測定中,nPbO2(s) 在以 ERM 為基質液時之生物有效性較高;添加 HA (0.4-0.5 mg/L) 於 ERM 或 TW 溶液中皆會降低 nPbO2(s) 對青鱂魚的生物有效性,這表示 HA 能有效懸浮 nPbO2(s) ,防止其聚集沉降於燒杯底部,因而使有啄食行為的青鱂魚攝取較少的 nPbO2(s)。毒性效應 (7 日暴露實驗) 的結果顯示, Pb2+(aq) (LC50 =0.323 mg/L) 對幼魚的急毒性大於 nPbO2(s) (LC50 > 25 mg/L)。暴露 nPbO2(s) 7天及14天皆會提高魚體內超氧歧化酶 (SOD) 活性及抑制過氧化氫酶 (CAT) 活性,而暴露 Pb2+(aq) 7天則會抑制 CAT 的活性,並造成體內 H2O2 含量上升,這表示 nPbO2(s) 或 Pb2+(aq) 會干擾生物抗氧化酵素系統的恆定。此外,經過 14 天的 nPbO2(s) 或 Pb2+(aq) 暴露皆會抑制青鱂魚幼魚乙醯膽鹼酯酶 (AChE) 的活性,顯示 nPbO2(s) 可能與 Pb2+(aq) 同樣具有神經毒性,詳細的作用機制仍待後續研究進一步探討。 Lead dioxide (nPbO2(s)), a nano-sized corrosion product newly identified in the water distribution systems, is formed via the chlorination of lead-containing plumbing materials. It can be detached as particulates or reduced to soluble lead to contaminate drinking water. Because of the historical use of lead pipes and chlorination worldwide, the generation of nPbO2(s) in the water distribution system poses a risk of lead exposure to human or aquatic life if it is discharged to aquatic environments. The environmental fate and toxicity of nPbO2(s) in the aquatic system, however, remain unclear at present. The objectives of this study are to investigate nPbO2(s) dynamic behaviors under different medium solution and assess bioavailability and causal toxicity of nPbO2(s) and lead ions (Pb2+(aq)) in medaka fish (Oryzias latipes). The larvae of medaka were treated with solutions containing nPbO2(s) at 0.25-25 mg/L or Pb2+(aq) at 0.25-2.0 mg/L (Pb equivalent concentrations) for a 7 or 14-day aqueous exposure. The results have shown that nPbO2(s) was more dispersed (~100 nm) and suspended in DI water than in embryo rearing medium (ERM) or dechloronated tapwater water (TW), while adding humic acid (HA, 0.4-0.5 mg/L) in the ERM or TW could effectively suspend nPbO2(s), indicating that ionic strength and dissolved organic matter (DOM) were the factors related to the aggregation and sedimentation of nPbO2(s). Humic acid also accelerated nPbO2(s) to release Pb2+(aq). In the bioavailability assay, higher bioavailability of nPbO2(s) to medaka larvae in ERM was due to the more uptake of aggregate nPbO2(s) by food-pecking behaviors, and it was less bioavailable in solutions that have higher humic acid and better suspension. Through 7-day acute toxicity test, Pb2+(aq) (LC50= 0.323 mg/L) is more acutely toxic to medaka larvae than nPbO2(s) (LC50 > 25 mg/L). Besides, intracellular levels of reactive oxygen species and activities of antioxidants such as superoxide dismutase (SOD) or catalase (CAT) were altered in larvae treated with nPbO2(s) (>5 mg/L) after 7-day and 14-day exposure. Pb2+(aq) also inhibited CAT activity and decreased O2- and OH-, but increased H2O2 content. Our results indicated nPbO2(s) or Pb2+(aq) could disturb the biological antioxidant enzyme system and may cause the accumulation of H2O2. In addition, exposures to nPbO2(s) or Pb2+(aq) showed that the acetylcholinesterase (AChE) activity was decreased in medaka larvae, which meant nPbO2(s) may be as neurotoxic as Pb2+(aq). However, the detailed toxic mechanism of nPbO2(s) needs further investigation. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/60759 |
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