Enantioselective Bioaccumulation of Hexabromocyclododecane and Congener-Specific Accumulation of Brominated Diphenyl Ethers in an Eastern Canadian Arctic Marine Food Web

Abstract

The extent of trophic transfer of the three diastereoisomers of hexabromocyclododecane (HBCD) and seven brominated diphenyl ether (BDE) congeners was examined in components of an Arctic marine food web from eastern Canada. Alpha and gamma-HBCD diastereoisomers were detected in all species and total (sigma) HBCD concentrations ranged from 0.6 +/- 0.2 pg/g (geometric mean +/- 1 x standard error (SE), lipid weight (lw)) in arctic cod to 3.9 +/- 0.9 ng/g (lw) in narwhal. beta-HBCD was below method detection limits in all the samples. Mean sigmaBDE (sum of seven congeners) concentrations ranged from 0.4 +/- 0.2 ng/g (lw) in walrus to 73 +/- 10 ng/g (lw) in zooplankton. The relative trophic status of biota was determined by nitrogen stable isotopes (delta15N), and results indicated clear differences in HBCD isomer and BDE congener profiles with trophic level (TL). Trophic magnification was observed for the alpha-diastereoisomer and BDE-47 as concentrations increased with increasing TL in the food web, whereas there was trophic dilution of gamma-HBCD and BDE-209 through the food web. Only the (-)alpha-enantiomer showed a strong positive relationship between concentration and TL (p < 0.01) with a trophic magnification factor (TMF) value of 2.2. A small but significant increase in the enantiomeric fraction value of the alpha-enantiomers with TL was also observed (r2 = 0.22, p < 0.005), implying that there is an overall preferential enrichment of the (-)alpha-enantiomer relative to the (+)alpha-enantiomer likely due to the greater bioaccumulation potential of the (-)alpha-enantiomer and/or to the greater susceptibility of the (+)alpha-enantiomer to metabolism.

Occurrence and biomagnification of organohalogen pollutants in two terrestrial predatory food chains

“…In the present study, the BMF of a-HBCD was >1 in the ratÀowl food chain, which was in line with previous studies. However, the BMF of a-HBCD in the sparrowÀkestrel food chain was less than 1 (Table A.1), which contradicted most aquatic studies wherein biomagnification potential was observed for a-HBCD Tomy et al, 2008a). Similarities were also found for DP in the studied food chains.…”

“…Tomy et al (2008a) found a strong positive relationship between the fraction of (À)-a-HBCD and trophic level, indicating the greater bioaccumulation potential of the (À)-aenantiomer and/or the greater metabolic susceptibility of the (+) a-enantiomer along with increasing trophic level. However, Janák et al (2008) observed a shift from the relative accumulation of (À)-a-HBCD in prey (herring, 0.24) to the relative accumulation of (+)-a-HBCD in predators (guillemot, 0.53).…”

Levels, isomer profiles and chiral signatures of particle-bound hexabromocyclododecanes in ambient air around Shanghai, China

“…The enrichment or discrimination of individual HBCD enantiomers were subsequently observed for organisms from other sites (e.g. Harrad et al, 2009b;He et al, 2010;Janák et al, 2008;Köppen et al, 2010;Peck et al, 2005;Tomy et al, 2008). As for a-HBCD, different species have different preferences for (þ)-or (À)-a-HBCD enantiomers.…”

“…The EFs of a-, b-and g-HBCD for commercial products and the sampling areas in Shanghai are calculated, with the assumption that HBCD standards are racemic mixtures (Table 1). Because mobile phase and column bleed can cause deviations in EFs of HBCD standards from 0.5 (Tomy et al, 2008), we corrected our EFs using 13 C 12 -labeled HBCDs. The…”

“…Thermal rearrangement and photo-isomerization also occur between these three diastereomers, especially between g-and a-HBCDs (Harrad et al, 2009a;Heeb et al, 2008aHeeb et al, , 2008bKöppen et al, 2008). Moreover, enantiomers of the three diastereomers exhibited different enrichment in biota samples with non-racemic signatures (Abdallah and Harrad, 2011;Covaci et al, 2006;Eljarrat et al, 2009;Esslinger et al, 2011;Harrad et al, 2009bHarrad et al, , 2010He et al, 2010;Köppen et al, 2010;Peck et al, 2005;Tomy et al, 2008). Two meso forms d-HBCD and 3-HBCD have been found by Heeb et al (2005) in commercial HBCD in concentration of 0.5% and 0.3%, respectively.…”