John Wiley & Sons, Ltd.

Probing the debromination of the flame retardant decabromodiphenyl ether in sediments of a boreal lake

After decades of using polybrominated diphenyl ethers (PBDEs) as flame retardants, a large reservoir of these toxins has accumulated in ecosystems worldwide. This study used an innovative approach to examine whether the fully brominated PBDE, decabromodiphenyl ether (decaBDE), degrades to more toxic congeners in aquatic environments. We incubated intact sediment microcosms with high‐purity [13C]decaBDE in a remote boreal lake to assess its debromination under ambient conditions. Although the addition of [13C]decaBDE increased total PBDE concentrations in sediment over 10‐fold, the relative amount of [13C]decaBDE in sediment did not change significantly over a 1‐month incubation. However, observation of small quantities of lower brominated [13C]BDEs lent support to the hypothesis that decaBDE is slowly debrominated. We observed a significant increase in octa‐ and nonaBDEs in profundal, but not littoral, sediment over 30 days. A second experiment in which sediment was incubated under different light and oxygen regimes yielded a surprising result—oxygen significantly stimulated the formation of octa‐ and nonaBDEs. We also conducted a large‐scale in situ enclosure experiment in which we followed the fate of experimentally‐added decaBDE in sediment over 26 months, but this study yielded little evidence of decaBDE debromination. Overall, we suggest that the debromination of decaBDE occurs very slowly, if at all, in natural sediment of boreal lakes, in contrast to the rapid degradation kinetics reported by most laboratory‐based studies, which are usually conducted by dissolving decaBDE in organic solvents. Our findings reinforce the need for field studies on contaminant fate to inform environmental policy decisions. This article is protected by copyright. All rights reserved

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