利用自動更水式全底泥暴露系統評估鄰苯二甲酸二（2-乙基己基）酯污染底泥對青鱂魚之慢毒性影響

Using the Larval Swimming Activity of Medaka Fish (Oryzias latipes) to Assess the Toxicity of DEHP Contaminated Sediment

10.6499/JSGR.2017.0401.005

江麗芬(Li-Fen Chiang)；吳柏成(Po-Cheng Wu)；陳佩貞(Pei-Jen Chen)

自動更水式全底泥試驗系統 ； 鄰苯二甲酸酯類 ； 鄰苯二甲酸二（2- 乙基己基）酯 ； 青鱂魚(Oryzias latipes) ； 慢毒性 ； sediment testing intermittent water renewal system (STIR) ； phthalate esters (PAEs) ； Di(2-ethylhexyl)phthalate (DEHP) ； medaka (Oryzias latipes) ； chronic toxicity

土壤及地下水污染整治

4卷1期（2017 / 01 / 01）

73 - 84

繁體中文

鄰苯二甲酸二（2- 乙基己基）酯（di(2-ethylhexyl)phthalate, DEHP）為常用的塑化劑，在底泥及水體環境中經常被檢測出之新興污染物。DEHP 具高疏水性及親脂性（log kow = 7.5)，易於累積在底泥或生物體中。然而，DEHP 的急毒性（acute toxicity）低，目前對於底泥毒性評估的檢測方法及相關研究較為缺乏，針對底泥中塑化劑污染對水生生物的慢毒性效應（chronic toxicity）更是所知有限。因此，本研究旨在利用自動更水式系統搭配全底泥暴露法（whole sediment exposure），來評估底泥DEHP 污染對青鱂魚苗（Oryzias latipes）之長期慢毒性效應，包括生長因子（ 如體長和體重)、抗氧化壓力酵素（ 如CAT、SOD、GST 和GR）及泳動行為等生物指標的影響，藉此建立針對DEHP 污染之有效且靈敏的生物毒害效應評估方法。研究結果顯示，添加DEHP 於人造底泥（250 ~ 1000 mg-DEHP/kg)，經21 天暴露後，青鱂魚幼魚的體長與體重隨DEHP 劑量升高而降低，且高濃度DEHP 底泥（500 及1000 mg-DEHP/kg)會顯著降低幼魚的GST 酵素（Gultathione S-transferases）活性，以及生物累積於魚體內。為了更有效量測底泥中DEHP 對青鱂魚苗的影響，本研究搭配魚苗泳動行為進行分析。結果顯示，暴露（7天）於DEHP 底泥（500 mg/kg）的魚苗泳動行為（如活動時間百分比、平均速度及絕對旋轉角度等行為指標）與空白底泥組相比有明顯的差異，顯示底泥中的DEHP 會干擾青鱂魚苗的游泳行為，如造成活動力下降及產生特定方向之偏好。

1. Introduction/Background Di(2-ethylhexyl)phthalate (DEHP) is a kind of phthalate esters (PAEs) as plasticizer commonly used in the plastic products and ubiquitously detected in surface water and sediment in the worldwide. DEHP with the property of low solubility is easy to bind to clay minerals and then be deposited in sediment as a pollutant source. Sediment-bound DEHP could be remobilized by bioturbation or flood events, and thus become available and pose a hazard to aquatic biota. However, at present there are limited methods for sediment toxicity tests that focus on long term sediment chronic exposure using a vertebrate aquatic species such as fish. This study aims to establish a chronic whole sediment exposure method by using a sediment testing intermittent water renewal (STIR) system with the early life stages of medaka (Oryzias latipes) fish to assess the chronic effect of DEHP-contaminated sediment. 2. Material and Methods The synthetic sediment was well mixed in a glass jar with a rolling mill and used as reference sediment to prepare the DEHP-spiked sediment (250 ~ 1000 mg-DEHP/kg-sediments). To optimize the condition of the chronic whole sediment exposure method using a sediment testing intermittent water renewal system (Figure 1), two factors (the volume of saturated sediment and the frequency with which the exposes water was changed) were tested. Tested fish (seven day post hatching larvae, 20 fish per beaker) were added to the exposure beaker and then placed in the STIR system for seven-21 days-exposure with a 14hr-light/10hrdark photoperiod at 26 ± 1°C. After the end of DEHP exposure, the medaka larvae were used to access locomotor activity (e.g., mobility, mean velocity, maximum velocity, absolute turn angle and relative turn angle) or measure growth factors (body weight and body length) and activities of antioxidant enzymes (e.g., GST, GR, SOD and CAT). The DEHP concentrations in overlaying water, sediment and fish bodies were quantified by HPLCDAD or GC-MS following the microwave extraction for sediment and fish samples and solid phase extraction for water samples, respectively. 3. Results and Discussion The results showed that the optimal operating condition for the chronic sediment exposure of medaka larvae is the use of 100 mL saturated sediment and 175 mL overlaying water with one time of water renewal every day (Figure 2). DEHP-contaminated sediments (250, 500 and 1000 mg-DEHP/kg) with a 21-days exposure inhibited the growth of medaka larvae by dose-dependently decreasing the body weight, body length (Figure 3) and antioxidant activities such as glutathione S-transferase (GST) (Figure 4). We also showed that the concentration of DEHP in medaka larvae was 26.09 ± 4.0 and 27.62 ± 1.9 mg- DEHP/kg-fish for the sediment treatment of 250 and 500 mg-DEHP/kg-sediment, respectively (Table 1). Furthermore, the swimming activities of medaka larvae were significantly affected and the decrease of the mobility and mean velocity of larvae (Figure 5) after seven day-exposures to DEHP-spiked sediment (500 mg/kg). 4. Conclusion This study successfully established a whole sediment exposure method in a STIR system to evaluate the chronic effects of DEHP spiked artificial sediments on medaka larvae. The results revealed that DEHP contaminated sediments significantly decreased the larval activities (mobility and mean velocity), the body length, the body weight and GST activities of medaka larvae, probably via the oral consumption of contaminated sediments by fish. Our results imply the chronic toxic effect of DEHP contamination in sediment to aquatic life such as fish.

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