六溴环十二烷（HBCD）是一类用于电子、电器产品和建筑材料的重要溴系阻燃剂，其使用量在所有溴系阻燃剂中处于第三位。HBCD已在环境介质和生物样品中广泛检出。虽然其在工业用HBCD产品中以γ-HBCD为主，但已有研究发现，在大部分生物样品中α-HBCD是其主要组分，同时，也有一些底栖水生生物及人体组织样品中的HBCD以g-HBCD异构体为主。然而，对造成这种组成差异的原因，目前尚不清楚。
中科院所广州地球化学研究所有机地球化学国家重点实验室麦碧娴研究组对采自广东清远电子垃圾区的各种鸟类及其食物和相关环境样品中的HBCD进行了系统分析，发现HBCD在鸟体内的异构体组成与其栖息环境和食源存在较大的关联性。在水生鸟类池鹭体内α-HBCD是主要甚至唯一被检出组分；在陆生鸟内中则发现γ-HBCD是主要组分；而在一些湿地水鸟体内，则没有统一的选择性富集α-或者γ-HBCD的现象。结合稳定碳同位素分析，并与鸟类相应食物和环境样品的比对，该研究组发现这种生物体内选择性富集某一HBCD立体异构体的现象，既受生物体内代谢作用影响，也受其食源影响。
同时，该研究还发现捕食者与被捕食者之间具有相似的手性组成，这表明生物体内发现的HBCD手性选择性富集现象，并不必然是生物体内发生手性选择性代谢的结果，从食物中继承也是一个重要原因。
这一研究成果对解释生物体内HBCD的选择性富集现象，提供了新的视角，也为正确认识HBCD的生物富集与转化提供了科学依据。（生物谷Bioon.com）
生物谷推荐英文摘要：
Environ. Sci. Technol. DOI: 10.1021/es1032597
Tetrabromobisphenol-A and Hexabromocyclododecane in Birds from an E-Waste Region in South China: Influence of Diet on Diastereoisomer- and Enantiomer-specific Distribution and Trophodynamics
Ming-Jing He, Xiao-Jun Luo, Le-Huan Yu, Juan Liu, Xiu-Lan Zhang, She-Jun Chen, and Bi-Xian Mai
Tetrabromobisphenol-A (TBBPA) and three diastereomers of hexabromocyclododecane (HBCD) were examined in the muscles of six bird species and their diet collected from an e-waste recycling region (Qingyuan) in South China. Stable isotope ratios (δ15N and δ13C) were analyzed to measure the diet source and trophic levels (TLs) of the birds. The median TBBPA and HBCD concentrations in the birds ranged from 28 to 173 and not detectable to 1995 ng/g lipid weight, respectively. The diastereoisomeric pattern shows the predominance of α-HBCD in birds feeding in an aquatic environment and that of γ-HBCD in birds feeding in a terrestrial environment, whereas no clear preference for α isomer or γ isomer was found in birds that inhabited freshwater wetland. A significant positive correlation between δ13C and percentage of α-HBCD was observed, indicating the importance of diet exposure pathways in the determination of HBCD diastereoisomer pattern. The enantiomer fractions (EFs) for α-HBCD differed substantially between aquatic and terrestrial bird species with a significant enrichment of (+) α-HBCD enantiomer for aquatic birds and a preferential enrichment of (?) α-HBCD enantiomer for terrestrial birds. The similarity in diastereoisomer profiles of HBCD and the EFs of α-HBCD between prey (fish) and predator (Chinese pond heron) also suggested that dietary exposure is an important contributor for the observed diastereoisomer- and enantiomer-specific distribution of HBCD in birds. Trophic magnification was observed for α-HBCD and TBBPA as concentrations increased with the TLs of the birds defined by δ15N, but only α-HBCD showed a strong positive relationship (p = 0.001). The biomagnification factors for α- and γ-HBCD and TBBPA were calculated based on individual predator/prey feeding relationships for two species.
