Distribution of hexabromocyclododecane in Detroit River suspended sediments

The distribution of hexabromocyclododecane (HBCD) isomers (α, β and γ) was determined in Detroit River suspended sediments using liquid chromatography tandem mass spectrometry (LC/MS/MS). Individual isomers of HBCD were measured at concentrations ranging from <0.025 to 1.9 ng/g (dry wt.) for the α-isomer, <0.025 to 0.28 ng/g for the β-isomer, and <0.025 to 2.3 ng/g for the γ-isomer. Concentrations of total HBCD ranged from <0.075 to 3.7 ng/g. Roughly two-thirds of HBCD profiles in suspended sediments were dominated by the γ-isomer, and were similar to profiles of commercial technical mixtures. Profiles in the remaining samples were dominated by the α-isomer. The β-isomer was consistently detected at substantially lower levels than the other isomers; this isomer is a minor constituent in the commercial technical mixtures. Seasonal sampling showed significant shifts in the relative ratios of the HBCD isomers. The spatial distribution of HBCD in the Detroit River was similar to other persistent organic pollutants (e.g., PCBs), and showed a strong association with urban/industrial activities in the watershed. However, the highest HBCD concentrations (2.6–3.7 ng/g) were associated with areas of contemporary industrial activity, and were much lower than maximum concentrations of PCBs (2.2 μg/g) found in areas of the Detroit River associated with historical industrial activity.