Spatial Distribution of Persistent Organic Pollutants in Surface Sediment Samples of Lake Huron
thesisposted on 27.02.2015 by Prabha G. Ranasinghe
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The purpose of this study was to determine the levels of selected PCBs, PBDEs, and novel halogenated flame retardants (nXFRs) in the surface sediments of Lake Huron. Surface sediment samples were collected from 59 locations of Lake Huron in 2012. Samples were extracted using accelerated solvent extraction (ASE). The extracts were cleaned up and fractionated with a silica gel / alumina adsorption chromatographic column. Concentrations were determined using gas chromatography (GC) coupled with a triple quadrupole mass spectrometer (QQQMS) for PCBs and PBDEs, and a single quadrupole mass spectrometer (MS) for decabromodiphenyl ether (BDE 209) and nXFRs. Results show detectible levels of most PCBs, PBDEs, dechlorane plus (DPs), and dechlorane analogs. But lower detection rates were observed for most of the brominated non–PBDE flame retardants in Lake Huron surface sediment samples. The total PCB concentrations (Σ39PCB) were in the range of 0.05 to 91 ng/g with a median of 3.73 ng/g; and PCBs 138, 146, 153, and 110 are among the most abundant congeners. Total PBDE (Σ9BDE) concentrations varied from 0.04 ng/g to 54 ng/g; and BDE209 was the most abundant BDE congener, followed by BDE 47. The BDE 209 accounts for more than 92% of the total mass of the Σ9BDE. The detection rate of DP was higher than of other chlorinated flame retardants. Anti-DP was the most abundant compound in this chemical group. Other non- brominated flame retardants including 1, 2-bis (2, 4, 6-tribromophenoxy) ethane (BTBPE), hexabromobiphenyls (HBB), 2-ethylhexyl-2,3,4,5-tetrabromo benzoate (EHTBB), deca abromodiphenyl ether (DBDPE), pentabromotoluene (PBT), 2,2’,4,4’,5,5’-hexabromobiphenyl (BB153), allyl 2,4,6-tribromophenyl ether (ATBPE) were also detected at comparatively high levels. Higher levels of PCBs were found in the sediments collected from Saginaw Bay than at other sampling sites, and the North Channel has the lowest PCB level. In contrast, halogenated flame retardants were found in higher concentrations in the samples collected in the North Channel. This suggests the presence of possible sources of pollution near the North Channel.