Polybrominated Diphenyl Ethers in Sediments from Arkansas, Illinois and Indiana of the United States
Sediment samples were collected from Arkansas, Illinois and Indiana of the United States and analyzed for polybrominated diphenyl ethers (PBDEs) and decabromodiphenyl ethane (DBDPE). BDE209 was found at 34,000 and 5,600 ng/g in the surface sediments and peaked at 57,000 and 48,000 ng/g at the two locations nearest to the manufacturing facilities in southern Arkansas, the highest levels ever reported in sediments worldwide. The DBDPE concentrations of 744, 870 and 2,400 ng/g found at the three locations closest to the manufacturing facilities are also the highest in sediment reported to date worldwide. The concentrations of total PBDEs (Σ49BDEs) ranged from 90 to 400 ng/g and from 1,900 to 3,500 ng/g in the surface sediments from Illinois and Indiana, respectively. BDE209 was dominant in the sediments of all locations, accounting for 69-97% of the total PBDEs. The surface concentrations in Arkansas samples versus distances from the sampling locations to manufacturing facilities fitted the Gaussian Plume Dispersion model (R2 of 0.98 for BDE209 and 0.90 for DBDPE). The spatial trends and the temporal trends suggest that the manufacturing facilities were the significant sources of BDE209 and DBDPE found in the sediments in Arkansas. The variation in congener distribution along the sediment depth suggests in situ debromination of BDE209 at one site, particular in upper sediment layers. Two nonabromodiphenyl ethanes (nona-BDPEs) were found at the site with elevated levels relative to DBDPE, suggesting the debromination of DBDPE. In order to understand PBDE debromination pathway, 13 congeners (BDEs 209, 208, 207, 206, 196, 183, 154, 153, 100, 99, 85, 47 and 28) in hexane were individually exposed to natural sunlight with different time segments up to 64 hours. Overall, 74 product congeners were detected. For the reactant congeners with <9 bromines, photolytic removal of bromines at meta position was preferred while the bromines at para positions were relatively resistant to debromination. The vulnerability of ortho bromines was generally in between. No preference of debromination at the substitution positions was found for the congeners with >=9 bromines. The total molar mass of PBDEs decreased dramatically during the sunlight exposure, indicating the formation of non-PBDE substances.
SubjectPolybrominated Diphenyl Ethers