多氯联苯醚在不同营养级水生生物体内的富集效应和转化特征研究

Polychlorinated diphenyl ethers (PCDEs) are structurally similar to polychlorinated biphenyls (PCBs). PCDEs have shown various eco-toxicological effects and have been ubiquitously detected in aquatic environment. It is very significant to reveal potential water environmental risks of PCDEs by studying their enrichment and transformation behaviors in aquatic organisms. In the current study, three types of aquatic organisms Scenedesmus obliquus, Daphinia magna and zebrafish that lay in different trophic levels were selected as the test organisms and a short-term indoor simulating aquatic food chain was established. Then, the enrichment effects and transfer laws of typical PCDEs in the aquatic food chain were investigated. The bioaccumulation ability of PCDEs in three types of aquatic organisms were quantitatively compared. In addition, relationships between the molecular structures and bioaccumulation ability of PCDEs were discussed. Using preparative chromatography, gas chromatography-mass spectrometry and high resolution mass spectrometry, the biotransformation products of PCDEs with typical structures in three types of aquatic organisms were separated and analyzed. The metabolism pathways of PCDEs in three aquatic organisms were proposed and the similarities and differences of PCDEs biotransformation characteristics in three kind aquatic organisms were discussed. The present study contributes to intensively understanding the migration and transformation rules and mechanisms of PCDEs in the aquatic ecosystem, and also provides significant scientific basis for ecological risks assessment of the water environment.

多氯联苯醚(PCDEs)结构与多氯联苯类似，具有多种生态毒理效应，在水体和沉积物中已有较多检出，研究PCDEs在水生生物体内的富集转化行为对揭示其潜在的水环境风险具有重要意义。本课题拟以典型的PCDEs为研究对象，选用斜生栅藻、大型蚤和斑马鱼三种处于不同营养级层次的水生生物，构建室内模拟水生生物食物链，探索这类化合物经水相接触暴露后在三种水生生物体内的富集效应和传递规律，定量地比较三种生物对PCDEs的生物富集能力，并探讨PCDEs分子结构与其生物富集能力之间的关系。同时，借助制备色谱、气相色谱-质谱和高分辨质谱等分析手段，对PCDEs在三种水生生物体内的转化代谢产物进行分离与鉴定，尝试构建相应的代谢转化途径，并比较其转化特征的异同。本课题的开展，有助于阐明PCDEs在水生生态系统中的迁移转化规律和机理，可为评估其水环境风险提供基础科学依据。

多氯联苯醚（PCDEs）是一类结构与多氯联苯（PCBs）类似的有机污染物，可对生物造成多种明显毒理效应，具有相当的生态和健康风险。本课题针对PCDEs开展了以下研究工作：1）分析了15种PCDEs在巢湖表层水、悬浮颗粒物及底泥中的分布水平，发现其在该三种环境介质中的总浓度范围分别为0.28-2.47 ng/g d.w.、0.33-2.01 ng/g d.w.和0.35-2.02 ng/L。2）测得了8种PCDEs对绿藻、大型蚤和斑马鱼的急性毒性效应，其相应半数致死剂量分别为0.07-8.99 mg/L（96 h-EC50），0.02-6.25 mg/L（48 h-LC50）和0.02-5.64 mg/L（96 h-LC50）。这些所获得的PCDEs水环境浓度及急性毒性数据为后续水体暴露实验的浓度设定提供了科学依据。3）研究了PCDEs在“绿藻-大型蚤-斑马鱼”室内模拟水生生物食物链的富集传递行为，测定得到10种PCDEs在绿藻、大型蚤和斑马鱼中的生物富集因子分别为0.84-4.23 L/kg脂肪、1.93-9.73 L/kg脂肪和0.793-8.506 L/kg脂肪，同时发现氯原子取代数目对PCDEs的生物富集能力具有明显影响。另外，研究指出PCDEs在大型蚤中富集能力最强，斑马鱼次之，在绿藻中最低。除DE外，其他PCDEs在模拟食物链中的营养级转移因子均大于1.0，证实了这些化合物具有一定的生物放大能力。4）探究了4,4’-di-CDE在三种不同营养级水生生物体内的代谢转化过程，发现其在绿藻和大型蚤中仅能通过脱氯反应生成4-mono-CDE。而4,4’-di-CDE在斑马鱼体内的代谢途径主要包括三种：一是脱氯生成4-mono-CDE；二是羟基化生成2-HO-4,4’-di-CDE；三是甲氧基化生成2-MeO-4,4’-di-CDE。代谢产物丰度的分析结果表明，甲氧基化反应为4,4’-di-CDE在斑马鱼体内的主要代谢途径。斑马鱼体内目标化合物代谢途径相对丰富，可能是因为斑马鱼体内代谢酶种类较多。本研究可为评估PCDEs的水环境风险提供有力的基础支持。