电子垃圾拆解地河流沉积物和鱼体中四溴双酚A的转化产物特征及形成机制研究

Tetrabromobisphenol A (TBBPA) is currently one of the largest volume brominated flame retardants, and it is used extensively in electronics and other consumer products. Since a global ban on polybrominated diphenyl ethers and hexabromocyclohexane under the Stockholm Convention on POPs, the situation of “irregular and uncontrolled use” of TBBPA and its derivatives as alternative chemicals in the manufacturing process is becoming more and more serious in China. TBBPA can enter to environmental media and organisms through various pathways, such as release from TBBPA manufacturing and processing of TBBPA-based materials, and emissions during the primitive e-waste dismantling. The recent studies show that China is the most polluted region as affected by TBBPA, and the environmental monitoring data also show widely detectable of the chemicals. However, TBBPA has a short half-life in vivo that would limit its accumulation in organisms. Once TBBPA reaches the environment, different degradation or metabolic routes may account. The major route of degradation is the dehalogenation leading to debromination products. TBBPA can also be O-methylated to form TBBPA-monomethyl ether and TBBPA-dimethyl ether. These transformation products of TBBPA has been found in various environmental media and organisms such as sediments, peregrine falcon eggs, fishes and human breast milk. In these studies, the concentrations of some transformation products are close to or even higher than its parents TBBPA, indicated that formation of transformation products may largely affect the accumulation of TBBPA in biotas. However, only few available studies focus on transformation products of TBBPA in biotas were reported. Little is known about the pollution characteristics and transformation mechanism of TBBPA from the most serious polluted e-waste dismantling site of south China. The assessment of transformation products became an important aspect of risk assessment of TBBPA. In this proposal, an analytical method will be developed for the determination of TBBPA and its dehalogenation and O-methylated products, then the method will be used to study the pollution characteristics of surface sediment layer samples and fish muscle matrix from e-waste recycling zone. In addition, compound-specific isotope analysis using gas chromatography-combustion-isotope ratio mass spectrometry will be used to provide insight into the mechanism of TBBPA biotransformation in fish. The project is expected to provide data in the pollution characteristics and give insight into the transformation mechanism of TBBPA in biota. The result of this study will also be helpful to the ecological and health risk assessment of TBBPA.

四溴双酚A（TBBPA）是目前用量最大的溴系阻燃剂，在超过70%的电子电气设备中都有应用，尤其是其他溴系阻燃剂如多溴联苯醚和六溴环十二烷等被列入《POPs公约》禁用名单之后，TBBPA及其相关衍生物应用更加广泛，造成的污染近年也呈急速加剧态势。TBBPA在生产和使用过程中可通过多种途径进入环境介质和生物体，由于转化产物可能是TBBPA在生物体内主要的赋存形态，因此，相关转化产物的研究成为其风险评估的关键。本项目拟从TBBPA及其转化产物的分析方法入手，以典型高污染的电子垃圾拆解地河流沉积物和鱼体为主要研究对象，通过对脱溴和羟基-甲基化等两类代表性产物的分析来阐明其污染特征，结合单体稳定碳同位素技术探讨转化产物形成机制，并筛选出能够表征水生态系统TBBPA污染的典型暴露标志物，为准确综合评估TBBPA的潜在风险提供科学数据与技术支撑。

四溴双酚A（TBBPA）是目前使用量较大的溴系阻燃剂（BFRs），随着电子产业迅速发展，TBBPA在大气、土壤、水、沉积物以及生物体中普遍发现，引起了人们广泛的关注。本研究通过对典型高污染电子垃圾拆解园区及周边环境的水环境介质和水生生物中TBBPA及其转化产物的存在、分布、组成成分的研究，通过TBBPA生物染毒实验分析其TBBPA及其转化产物碳同位素分馏特征进行进一步验证，帮助我们理解TBBPA在水环境介质及水生生物中的行为、转化、归宿，并为其在其他环境生态系统中的转化行为提供参考。研究发现，TBBPA及其转化产物在环境介质及生物体中普遍存在，在不同采样点位TBBPA及其转化产物的污染水平也有差异。来自靠近电子垃圾拆解园区采样点位的样品，无论是沉积物或是生物样品中TBBPA及其转化产物的浓度都有明显的增加这表明原始的电子垃圾拆解活动是水环境介质和水生生物中这些污染物的主要来源。对于转化产物，无论在沉积物或是生物样品中，tirBBPA是占比最高的脱溴产物，其甲基化产物含量最丰富的为diMeO–TBBPA；除此以外，本研究也检测到了高浓度BPA，BPs中浓度最高的物质为2,4,6-BP。对比沉积物和生物中转化产物污染水平，发现脱溴产物在沉积物和生物中均有高污染水平，而甲基化产物主要出现在生物体中，沉积物中含量极低，说明甲基化产物更容易在生物体中转化并富集。对主要转化产物的生物–土壤/沉积物富集因子（BSAFs）研究也显示，diMeO–TBBPA在鱼和螺中BSAF值明显高于TBBPA，表明甲基化产物更容易使水生生物从沉积物中富集该物质。与此同时，通过对鱼体各组分（肌肉、鳃、内脏、肠道及其内容物）的分析研究，发现内脏（肝脏和肾脏）中甲基化产物的浓度要高于其他组织，这可能说明鱼体在主要代谢场所进行了甲基化转化。分析染毒实验鱼体中碳同位素分馏现象并没有明显显示出同位素分馏，并且转化产物含量较低难以富集达到同位素分析标准，还需进一步研究证明。本研究为TBBPA在典型污染场地水环境介质和水生生物中积累和生物转化提供了基础数据和科学分析，在日后研究中应当考虑转化产物的存在及健康风险，针对其转化产物的代谢机理、准确源解析还需要进一步的研究证明。