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

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 (delta N-15 and delta C-13) 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 alpha-HBCD in birds feeding in an aquatic environment and that of gamma-HBCD in birds feeding in a terrestrial environment, whereas no clear preference for alpha isomer or gamma isomer was found in birds that inhabited freshwater wetland. A significant positive correlation between delta C-13 and percentage of alpha-HBCD was observed, indicating the importance of diet exposure pathways in the determination of HBCD diastereoisomer pattern. The enantiomer fractions (EFs) for alpha-HBCD differed substantially between aquatic and terrestrial bird species with a significant enrichment of (+) alpha-HBCD enantiomer for aquatic birds and a preferential enrichment of (-) alpha-HBCD enantiomer for terrestrial birds. The similarity in diastereoisomer profiles of HBCD and the EFs of alpha-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 alpha-HBCD and TBBPA as concentrations increased with the TLs of the birds defined by delta N-15, but only alpha-HBCD showed a strong positive relationship (p=0.001). The biomagnification factors for alpha- and gamma-HBCD and TBBPA were calculated based on individual predator/prey feeding relationships for two species.