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年度	106	專案性質	實驗性質
專案類別	研究專案	研究主題	底泥
申請機構	國立屏東科技大學	申請系所	環境工程與科學系
專案主持人	謝季吟	職等/職稱	教授
專案中文名稱	河川底泥金屬生物有效性的評估方法
中文關鍵字	底泥、生物有效性、酸揮發性硫化物、同時提取金屬、Hyalel
專案英文名稱	Methods for assessing metal bioavailability in river sediments
英文關鍵字	Sediment, Bioavailability, Acid volatile sulfides, Simultaneously extracted metals, Hyalella azteca, Diffusive gradients in thin films
執行金額	800,000元
執行期間	2017/1/9 至 2017/11/30
計畫中文摘要	台灣溪流環境水流湍急，造成棲地環境物化特性的快速變動，許多污染物被沖刷而蓄積在水體底層表面。底泥為許多底棲生物棲息之場所，亦為溪流水體潛在污染來源，其中有許多包括物化交互作用、硫化物和生物等因子都會影響汙染物的生物可利用性。本研究將嘗試結合化學評估和生物毒性測試來預測底泥和孔隙水中金屬的生物可利用性。除了利用會影響平衡分配的酸揮發性硫化物及同時提取金屬分析判斷台灣南部武洛溪及牛稠溪之底泥金屬生物毒性，主要目的還希望能探討不同萃取模式(全量金屬及稀釋酸萃取)及擴散梯度薄膜裝置等多面向來判斷底泥金屬之生物可利用性，並搭配底棲端足蟲Hyalella azteca (10天及28天全底泥急慢毒性及48小時孔隙水毒性)試驗進行水生生態系統危害程度(Tiers evaluations)評估，另外也利用潛在生態風險指數 (potential risk index) 來判斷各樣站底泥金屬在不同季節之風險等級。 本研究透過底泥基本物化性質可得知牛稠溪以砂粒為主，而武洛溪則以坋粒比例較高。總有機碳介於0.38%~4.27%，其中以樣站N2最低，樣站WR4最高。利用不同底泥品質指標(台灣底泥品質指標上下限值、TEL/PEL、共識法底泥品質基準)判斷底泥污染程度之結果顯示，武洛溪高於上限值之比例大於牛稠溪，其中又以武洛溪W4高於三種指標上限值，及污染最為嚴重。以平衡模式法進行評估結果顯示，武洛溪W4經三種指標(以ΣSEM/AVS > 9、ΣSEM–AVS > 2μmol/g及ΣSEM-AVS/foc＞130μmol/g)，底泥金屬含量皆會對水生生物及人體健康造成不利影響，為本研究底泥金屬毒性最高之樣站；而底泥金屬影響程度最低樣站為N5、及W2，在三種指標均未超過閾值。擴散梯度薄膜技術結果顯示，放置現地96h之DGT 與實驗室之吸附具有顯著相關。序列萃取搭配RAC計算之結果顯示武洛溪(W1~W5)樣站無風險或低風險之比例介於62.5(W2) ~87.5% (W3)；其中以金屬Mn評估之風險值最高。牛稠溪流域之風險比例介於為50.0~87.5%，以Mn及Zn 產生之風險值最高。潛在生態危害風險指數評估結果顯示，單一及多重底泥金屬污染評估結果均顯示武洛溪較牛稠溪相對污染嚴重之流域。 全底泥毒性試驗急毒性顯果顯示，以W1存活最佳，枯水期N3、N4及W3與豐水期於試驗終點並未觀察到任何存活個體；慢毒性試驗結果顯示樣品暴露之個體體長及重量均低於控制組，且藉由統計分析結果顯示均具有顯著性差異，顯示樣站污染物對生物體體長與體重均具有明顯抑制效應。孔隙水急毒性試驗結果顯示，武洛溪各樣站平均存活率低於牛稠溪，顯示因雨量或地區變化所存在溶解性污染物對底棲無脊椎動物具急毒性效應。 根據統計分析結果顯示，Cu濃度對於底泥慢毒性試驗之成長效應(體長)具有顯著性相關 (p<0.05)；重量則與孔隙水中Cd、Co、Cu及Ni濃度具有顯著性相關(p<0.05)，顯示生物體長時間暴露於溶解性污染物儘管並未直接產生生物死亡，但可能抑制其成長。此外，根據DGT濃度與生物體累積之金屬濃度進行線性迴歸結果顯示，吸附於DGT之Cu與Mn金屬與端足蟲生物體累積濃度呈正相關。 綜合各種以化學為基礎的潛在金屬生物利用性預測生物毒性之能力差異很大。並沒有一種方法足以完全預測其生物毒性，但初估能力排序依序為DGT >全量消化(總金屬濃度)> 孔隙水> 序列萃取 > 稀釋酸 > SEM-AVS模式。本研究數據未來能提供底泥金屬污染物生物有效性評估，其對管理者在品質準則施行及風險定量上是非常重要的。
計畫英文摘要	Sediment not only provides habitat for benthic organisms, it is also a potential source of contamination of streams and therefore has a significant influence on the aquatic environment. Many contaminants are washed into and stored in bottom waters and subsequently change the physical and chemical characteristics of the habitat. Sediments are complex, within which many processes (physical/chemical interactions, acid volatile sulfide [AVS] interaction, and biological) occur that affect contaminant bioavailability. A combination of chemical assessment and biological toxicity testing was conducted to predict the toxicity of metals in sediments or pore water. Equilibrium partitioning models using AVS were applied simultaneously with extracted metals analyses to evaluate the bioavailability of sediment metals that exhibit toxic effects from the Niuchou and Wuluo Rivers. Their bioavailabilities were compared in multiple approaches to determine which DGT-metal fluxes were useful for predicting the acute and chronic toxicities of multiple metals in selected sediments. That acid extracting metal (AEM) measurements provide more information on labile and biologically available sediment phases also remains unclear. Therefore, their toxic effects were evaluated using the amphipod Hyalella azteca (10-day and 28-day for whole sediments and 96-hr for pore waters) to assess their hazard (Tier 1, Tier 2, and Tier 3) to aquatic ecosystems. The potential risk index was applied to clarify the degree of ecological risk in the tested sediments. In this study, a basic physico-chemical assessment showed that sediments in the Niuchou River were mainly composed of sand while in the Wuluo River consisted of a higher proportion of silt. Total organic carbon ranged from 0.38% to 4.27%, with the lowest found at site N2 and the highest at site WR5. The degree of contamination, based on different sediment quality indicators (Taiwan sediment quality guidelines, TEL / PEL, CBSQGs), indicated that metals in sediments exceeded upper guideline limits more often in the Wuluo River than in the Niuchou River. Among sampling sites, W4 in Wuluo exceeded all three guideline limits, which indicated more serious pollution. Three indicators (ΣSEM / AVS > 9, ΣSEM – AVS > 2 μmol/g, and ΣSEM - AVS / foc > 130 μmol/g) implied that metals in W4 sediments exerted the highest toxicity and therefore had the greatest adverse impacts on aquatic life. The lowest impacts from metals were at sites N5 and W2, and did not exceed all three indicators. Our results showed that diffusion gradient thin films (DGT) under a 96-hr in situ field exposure were significantly correlated with adsorbed mass in laboratory tests. A combination of the sequence extraction technique and risk assessment code calculation (RAC) showed that the risk in the Wuluo River was in the range of 62.5 (W2) ~ 87.5% (W3) and the highest risk was from Mn. The risk for the Niuchou River was between 50.0 ~ 87.5%, with higher risk values being found for Mn and Zn. The potential ecological risk index showed that serious sediment contamination in the Wuluo River was from either single or multiple sediment indicators. Whole sediment acute toxicity tests showed that survival at site N1 was highest and that there were no survivors at sites N3, N4, and W3 by the end of the trial. Chronic toxicity testing showed that the growth (body length and weight) of H. azteca was lower than in controls and that there were statistically significant differences among samples, indicating that the contaminants had significant inhibitory effect on growth. Average survival (pore water) in the Wuluo River was lower than in the Niuchou River, indicating that the presence of dissolved contaminants may have acute effects on benthic invertebrates. Cu concentration was significantly correlated (p < 0.05) with the growth (body length) of exposed biota in sediment toxicity tests. Body weights were significantly correlated with Cd, Co, Cu, and Ni concentrations in porewater (p < 0.05), indicating that dissolved contaminants over extended periods of time may inhibit growth but not cause death directly. In addition, this relationship was observed for DGT measurements of Cu and Mn accumulating in H.azteca. In summary, the ability of different chemistry-based measures to predict potential metal bioavailability to H. azteca varied considerably. None of the methods appeared to be particularly precise; however, our preliminary conclusion is that they followed the descending order of DGT > total metal concentrations > porewater concentration > sequential extraction > dilution acid concentration > SEM–AVS mode. Useful information could be provided to regulators when using this contamination evaluation during the process of quantifying risk and implementing related guidelines.