滇池鱼类典型环境内分泌干扰物生物富集及毒性效应研究

【作者】 刘晶靓；

【导师】 潘学军；

【作者基本信息】 昆明理工大学 ， 环境科学， 2012， 博士

【摘要】 环境内分泌干扰物(EDCs)是指干扰生物体内保持自身平衡和调节发育过程中天然激素合成、分泌、运输、代谢、结合、反应或消除的外源性化学物质。这类物质的存在会干扰人类及野生动物内分泌系统,从而对机体的生殖发育、免疫系统、神经系统等多方面产生异常效应,如野生鱼类雌雄同体和雌性化现象的频发,人类睾丸癌、前列腺癌、乳腺癌、子宫癌发病率的增加等。EDCs,尤其是类固醇类和酚类EDCs,因其对环境暴露生物体正常生长发育和繁殖带来的潜在危害而成为当前科学界和公众共同关注的热点问题之一目前,各国均在河流和湖泊中发现了类固醇类和酚类EDCs污染,其在水体及底泥中的污染来源、分布特征和环境归宿等研究已日益完善。但是对鱼类及其它水生生物中此类物质污染特征和富集水平的研究却十分有限,EDCs较低的含量和复杂基质的干扰致使其分析检测成为了较大的挑战。因此,建立生物样品中准确、灵敏的化学分析方法已成为EDCs研究亟需解决的问题。此外,国际上大部分毒性效应研究主要是针对成熟的实验鱼类(如斑马鱼、青鳉和黑头软口鲦)进行实验室急性毒性试验或高浓度暴露实验,缺乏实验室长期环境浓度暴露的数据,难以将实验结果应用于实际水域中生物效应及环境风险的评价。本论文以前期研究中发现的滇池水体中普遍存在的类固醇类和酚类EDCs为切入点,包括雌酮(E1)、17-β-雌二醇(E2)、17-a-乙炔基雌二醇(EE2)、雌三醇(E3)、辛基酚(4-t-OP)、壬基酚(4-NP)、双酚A (BPA)和枯烯基酚(4-CP),深入研究滇池鱼类(鲫鱼、鲤鱼和银白鱼)中8种类固醇类和酚类EDCs的富集特征和组织分布,并进一步以滇池特有鱼类高背鲫鱼为实验鱼类,从滇池网式放养、污水处理厂网箱暴露和实验室模拟暴露三方面开展毒性效应研究。将环境分析化学与污染物暴露引起的毒理学效应相结合,综合评估滇池水体中EDCs的生物效应和毒性危害。研究成果可以为滇池水系此类污染物治理对策与措施的制定提供科学依据,具有明显的理论意义、社会环境意义和应用价值。(1)建立了生物样品中8种类固醇类和酚类EDCs的分析方法,包括样品的采集、微波辅助萃取(MAE)、凝胶渗透色谱净化(GPC)、固相萃取(SPE)、衍生化和气相色谱-质谱联用(GC-MS)检测。对生物样品前处理过程进行条件优化,并将GPC技术应用到生物样品的净化中。结果表明,MAE的最佳条件是以30mL甲醇为萃取溶剂,在110℃下萃取20min; GPC的最佳条件是以乙酸乙酯/环己烷(1：1,v/v)为流动相,选择7-14min为目标化合物馏分的收集时间段；SPE的最佳条件是选择Sep-Pak C18柱富集目标化合物,以15mL乙酸乙酯为洗脱溶剂。该方法平均回收率为51.5%-100.6%,相对标准偏差为2.3%-12.7%,检出限为0.3-0.7ng/g,具有良好的回收率和重现性。应用该方法对急性暴露鱼样中的类固醇类和酚类EDCs进行了分析检测,充分验证该方法可应用于环境生物样品中痕量类固醇类和酚类EDCs的定量测定。(2)完成了滇池典型鱼类(鲤鱼、鲫鱼和银白鱼)肌肉及各组织器官中类固醇类和酚类EDCs的分布特征及生物富集规律研究。结果表明,肌肉样品中酚类EDCs (4-t-OP、4-CP、4-NP和BPA)的浓度分别为ND-4.6ng/g、ND-4.4ng/g、ND-18.9ng/g和10.1-83.5ng/g；类固醇类EDCs污染相对较轻,其浓度均低于11.3ng/g。由于食性、生活习性以及在食物链中所处营养级的差别,不同鱼类中类固醇类和酚类EDCs的污染水平存在较大的差异。银白鱼中目标化合物浓度最高,是鲫鱼肌肉中浓度的2-3倍,鲤鱼介于银白鱼和鲫鱼之间。鲤鱼和鲫鱼各组织中类固醇类和酚类EDCs的浓度也存在明显的差异,基本符合肝脏>鳃>肌肉这一规律。在已知水体和鱼类肌肉中酚类EDCs浓度的基础上,计算出滇池鱼类中酚类EDCs的生物富集因子(BCF)为18-97。通过分析类固醇类EDCs实验室BCF值及其在肌肉中的浓度,预测出滇池水体中类固醇类EDCs的浓度为4.4-18.0ng/L,接近其它水体中已报道的浓度。研究结果证明,滇池鱼类中存在着不容忽视的EDCs污染和危害,部分EDCs污染已达到产生生物毒性效应的水平,并可能对暴露人群产生一定的健康风险。此外,滇池鱼类肌肉及组织中EDCs的污染水平也可以用来作为评价滇池水体EDCs污染的一个重要指标。(3)以滇池固定区域网式放养的高背鲫鱼为真实环境对照组,同步进行昆明第五污水处理厂出水暴露实验,综合评价污水处理厂出水中多种EDCs长期复合暴露对高背鲫鱼的生物富集和毒性效应。结果表明,污水处理厂出水存在着一定浓度的类固醇类和酚类EDCs,对暴露鱼类产生了一系列的毒性效应,如性腺生长的抑制、肝脏指数和血浆中Vtg含量的增加,并发现评价指标的变化与污水处理厂出水中类固醇类和酚类EDCs在鱼体内的富集积累程度有关。因此,类固醇类和酚类EDCs在暴露鱼类中的富集浓度也可以作为衡量污水处理厂出水中该类物质毒性效应的评价指标。(4)通过鱼类急性毒性试验得到E2和EE2对高背鲫鱼鱼苗的96h半致死浓度(LC50)分别为0.403mg/L和0.149mg/L。建立了实验室流水暴露系统,对高背鲫鱼进行16个月低剂量典型EDCs(E2和EE2)的单一及复合暴露实验。结果表明,实验室长期低剂量E2和EE2暴露对高背鲫鱼产生了显著的生物富集作用。E2和EE2对高背鲫鱼具有较强的毒性效应,如生长状况和性腺生长的抑制、肝脏指数和血浆中Vtg含量的增加,且EE2的毒性强于E2。此外,低浓度E2和EE2的混合暴露对脏器指数和Vtg含量的影响强于单一暴露。急性毒性试验和实验室长期暴露实验的结果均表明高背鲫鱼对典型EDCs(E2和EE2)具有较强的敏感性,可以作为潜在的模型动物用于EDCs的野外及实验室暴露研究。更多还原

【Abstract】 Endocrine disrupting chemicals (EDCs) are defined as exogenous agents that interfere with the production, release, transport, metabolism, binding, action, or elimination of natural hormones in the body. These compounds are responsible for the maintenance of homeostasis and the regulation of developmental processes. EDCs may disturb the function of endocrine system in human and wildlife and consequently cause adverse effects on development, reproduction, immune and nervous system of organism. The adverse effects, such as hermaphrodism (male and female gonads in a single individual) and feminization in wild fish, and breast, prostate and testicular cancer in human, have been widely reported. EDCs, particularly steroids and phenols, have attracted a great deal of scientific and public attention worldwide due to their potential adverse effects on the normal reproduction and development of environmentally exposed organisms.Currently, steroids and phenols have been detected in rivers and lakes all over the world. Sources, distribution characteristics and environmental fate of steroids and phenols in water and sediment were also estimated. However, their occurrence in fish and other aquatic organisms has been reported in only a limited number of studies and their bioaccumulation has not been well studied. The low levels of EDCs and complex matrix (contain a number of potentially interfering compounds) make measurement and monitoring of these contaminants in biological samples challenging. Thus, the development of an analytical method for the accurate determination of EDCs in biological samples is of crucial importance. In addition, toxicity studies are popular in the use of ideal experimental fish, such as zebrafish (Danio rerio), medaka (Oryzias latipes) and fathead minnow (Pimephales spromelas). Most toxicity data available are restricted to acute toxicity test or short-term exposure experiment in laboratory. Therefore, the lack of long-term exposure data often limits their application in the assessment of biological effects and environmental risk of EDCs in aquatic environment.In this study, typical representatives of steroidal and phenolic EDCs, including estrone (El),17β-estradiol (E2),17a-ethynylestradiol (EE2), estriol (E3),4-tert-octylphenol (4-t-OP),4-cumylphenol (4-CP),4-nonylphenol (4-NP) and bisphenol A (BPA), are collectively selected as target compounds, which have been found in water samples collected from Dianchi Lake in our previous studies. The objective of this study was to investigate the bioaccumulation characteristic and tissue distribution of steroidal and phenolic EDCs in wild fish collected from Dianchi Lake, including crucian carp(Carassius auratus), carp (Cyprinus carpio) and silvery minnow (Anabarilius alburnops), and to estimate the effects of steroidal and phenolic EDCs on high-back crucian carp(Carassius auratus) by exposure experiment in WWTP effluents, Dianchi Lake and laboratory. Biological effects and environmental risks of EDCs on fish in Dianchi lake were also comprehensively examined by combining the experiments of environmental analytical chemistry and toxicological exposure. The research results would provide scientific basis for making strategies and measures of EDCs in Dianchi catchment, which has remarkable significances in theory, social, environmental health and engineering application.(1) An improved method was developed for the simultaneous determination of eight steroidal and phenolic EDCs in biological samples. The proposed method were consisted of sample collection, microwave-assisted extraction (MAE), automated gel permeation chromatography (GPC), solid phase extraction (SPE), derivatization and gas chromatography-mass spectrometry (GC-MS) analysis. The optimal extraction and cleanup procedures were investigated using MAE, GPC and SPE. Experimental results indicated that the most efficient extraction was achieved by using MAE with methanol as solvent at an extraction temperature of110℃for20min. The cleanup of extracts was carried out by GPC on a Biobeads S-X3column with cyclohexane/ethyl acetate (1:1, v/v) as mobile phase. Target compounds were eluted in the fraction from7-14min retention time. Moreover, the cleanest extracts were obtained by solid phase extraction with C-18cartridges after the elution with15mL ethyl acetate. The method was validated by spiked samples which showed good recovery and reproducibility. The overall recoveries ranged between55.1%and100.6%, with relative standard deviations (RSD) of2.3-12.7%for the entire procedure. Method detection limits (MDL) ranged from0.3to0.7ng g-1dry weight (dw). Performance of the method was demonstrated by its application on tissues from fish exposed to high concentration of EDCs in the laboratory. The developed method is a promising approach for the analysis of steroid and phenolic endocrine disrupting chemicals in various biological samples.(2) The distribution and bioaccumulation of steroidal and phenolic EDCs were studied in various tissues of wild fish species from Dianchi Lake, China. In muscle tissue, phenols (4-t-OP,4-CP,4-NP and BPA) were detected in fish from each sampling site, with maximal concentrations of4.6,4.4,18.9and83.5ng/g dw, respectively. Steroids were found at lower levels (<11.3ng/g dw) and less frequently in muscle samples. An interspecies difference in concentrations was evident due to their feeding preference, general behavior and trophic level. Indeed, it was found at the highest levels in silvery minnow but at levels2-3times lower in crucian carp, carp showed intermediate levels. Moreover, the concentrations of steroids and phenols in the gill, liver, and muscle were very variable. The highest concentrations were found in the liver, followed by those in the gill and the lowest in muscle. The field BCF values of phenols in the18to97range were calculated in different fish species. The estimated concentrations of steroids in water were in the range of4.4-18.0ng/L, which were in the proper range compared with those reported by other researchers. These results showed that steroidal and phenolic EDCs were likely ubiquitous contaminants in wild fish. In addition, muscle and tissue concentrations could be a valid means by which to assess the contamination of EDCs in surface water.(3) Compared with fish controls caged in Dianchi Lake, the biological effects and bioaccumulation of steroidal and phenolic EDCs were assessed in high-back crucian carp exposed to WWTP effluents. The results indicated that high-back crucian carp readily accumulated steroidal and phenolic EDCs from WWTP effluents, resulting in the enhanced synthesis of vitellogenin (Vtg), the inhibition of gonad growth and the increase of liver metabolism. Some of the differences in biological response appeared to relate to differences in EDCs uptake and metabolism. Therefore, the presence of steroidal and phenolic EDCs in muscle samples of high-back crucian carp could be used as an effective biomarker of exposure to WWTP effluents, considering the capacity of bioaccumulation of this species.(4) In acute toxicity test, the96h half-lethal concentrations (LC50) of E2and EE2to juvenile high-back crucian carp were0.403mg/L and0.149mg/L, respectively. The biological bioaccumulation and toxicological effects of E2and EE2were assessed in high-back crucian carp exposed to low concentrations of E2and EE2(single and binary mixture exposure) in flow-through exposure system for16months. The results showed that high-back crucian carp readily accumulated E2and EE2from single and binary mixture exposure group, resulting in the inhibition of growth status and gonad growth, the increase of Vtg levels and liver metabolism. High-back crucian carp were generally more sensitive to EE2than E2exposure. Moreover, the biological effects of binary mixture of E2and EE2at the low concentration were more potent than that of individual compounds when GSI, HSI and Vtg were used as endpoint. The results of acute toxicity test and long-term exposure experiment in laboratory indicated that high-back crucian carp were sensitive to typical EDCs and may be chosen as potential model species in field and laboratory studies.更多还原