| The spatial distributions and temporal trends of polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) were investigated in the sediments of the Great Lakes. Totally 16 Sediment cores were taken far offshore in different locations of Lakes Superior, Michigan, Huron, Ontario and Erie, and segmented in 0.5 to 5 cm intervals. Samples were Soxhlet-extracted, cleaned up by silica gel fractionation, and the concentrations of 10 PBDE congeners (including decabromodiphenyl ether, BDE-209) and 39 PCB congeners (for Lake Superior, 19 PCB congeners) were measured by GC-MS in SIM mode. The year of sediment deposition was estimated using 210Pb dating technique, and sediment characterized for bulk density, organic matter, organic carbon and elemental contents of nitrogen and oxygen. For each sampling location, concentration profiles were constructed against sediment depth. Based on the results of sediment dating, the chronology of PBDE input flux was derived from the concentration data. Ranges of PBDE inventories in the sediments were estimated to assess the chemical accumulation.;For all the five Great Lakes, PBDEs manifest different temporal trends from PCBs in each core. In contrast to recent decline or level-off trends in PCB fluxes, the sedimentary records of PBDEs generally show a significant increase in recent years, and match the increasing trend in production and usage of PBDEs since the 1970s. The OC (organic carbon content) normalized average concentrations of Sigma9PBDEs in surficial sediments are in the order of ON > ER > LM > HU > SU, lakewisely, similar to the order of current PBDEs fluxes in the Great Lakes. The findings revealed that BDE-209 is the most abundant congener among PBDEs in the sediments, followed by BDE-47 and BDE-99. |
