Introduction Lake Ontario is one of the world’s largest lakes with a surface area of 19,000 km 2 and an average depth of 86 m. In addition to supporting valuable commercial and recreational fisheries, it is the major source of drinking water to surrounding US and Canadian metropolitan areas 1. Canadian researchers recently reported that polybrominated diphenyl ethers (PBDEs) are rapidly increasing in Lake Ontario fish tissue since the early 1980s 2. PBDEs have been widely used in manufacturing as an additive flame retardant 3. We analyzed extracts of large volume surface water samples collected on Lake Ontario in the Fall of 1999 to establish baseline information on Lake Ontario surface water PBDE concentrations, dominant congeners and distribution between suspended solids and dissolved phases. This is the first report of PBDEs being measured in North American surface waters. Sampling Methodology Large volume surface water samples were collected during fall isothermal conditions with the assistance of U.S. EPA’s research vessel the Lake Guardian (Fig. 3). Lake water was pumped into the samplers using an intake tube suspended from a boom off the side of the vessel and towed 1 m below the surface (Figs. 4 & 5) Duplicate samples were collected in the eastern, central and western basins of the lake (Fig. 6). Samples were collected over 24 hrs while covering an ~50 km 2 grid pattern to collect a spatially and temporally integrated sample. Surface water was pumped through a glass fiber filter cartridge (1 µm nominal porosity) to capture contaminants bound to suspended solids and then through two columns each holding 35 g of XAD resin (divinylbenzene- styrene copolymer) to capture dissolved hydrophobic contaminants (Figs. 7, Table 1). Fig. 3 Research Vessel Lake Guardian U.S. EPA Great Lakes National Program Fig. 4 Water intake tube attached to streamlined steel weight. Fig. 5 Towing water intake off the side of the vessel. Analytical Methods Filter samples and XAD resins were spiked with a suite of 13C labeled internal standards, soxhlet extracted overnight with dichloromethane, and the extract fractionated on a Florisil™ column. The Florisil column fraction containing ortho-substituted PCBs was concentrated down to 20 µL and analyzed for PBDEs using a pressure programmed DB-5HT column and detected by EI positive ion HRMS at 10,000 mass resolution, in selected ion mode, monitoring two peaks in the molecular ion cluster. The method was calibrated with a set of 41 PBDE congeners (mono to decabromo, based on Cambridge Isotope Labs analytical standard #EO-4980). PBDEs were quantitated against 13C labeled internal standards and individual response factors were determined for each reported congener. Results Concentrations of PBDEs in Lake Ontario surface waters are ~ 6 pg/L with ~80% in the dissolved phase (Fig. 9). Duplicate samples showed good agreement. BDE-47 and BDE-99 are the most abundant congeners together making up ~60% of total PBDEs (Fig. 10). Fig. 10 Total (dissolved + solids) concentrations of most abundant PBDE congeners detected in Lake Ontario surface waters (pg/L), Fall Fig. 9 Lake Ontario surface water dissolved and suspended solids PBDES concentrations (pg/L) collected Fall Comparison of the mass of PBDEs found on the first and second XAD columns show that the first column captured most (>90%) of the total dissolved phase PBDEs. BDE-47 and BDE-99 were not detected on the second columns (Fig. 11). Fig. 11 Mass of dissolved PBDE congeners captured on the first and second XAD resin columns, Western Basin. Reported surface water PBDE concentrations were corrected for lab contamination by subtracting procedural blank concentrations on a batch specific basis. Three of the four batches of samples were analyzed in a newly constructed lab. Procedural blanks from the new lab showed ~ 5 to 10 times higher PBDE concentrations than blanks from the older lab (Figs 12 & 13). It was determined that the lining of the ventilation ducts in the new lab (Lab #2) contained percent levels of PBDEs. The absence of BDE-47 and BDE-99 on the second XAD column, analyzed separately from the first, provides good evidence that reported PBDE surface water concentrations are not simply the result of lab contamination. Fig. 12 Total PBDE (pg/sample) detected in procedural Blanks. Fig. 13 Dominant PBDE congeners Procedural Blanks. Discussion BDE-47 and BDE-99 are the dominant PBDE congeners in Lake Ontario surface waters accounting for more than 60% of total PBDEs. These are also reported to be the dominant congeners in Lake Ontario lake trout tissue 2. The finding that ~80% of PBDEs are in the dissolved phase is surprising but may be partly a consequence of the low total suspended solids concentrations present in Lake Ontario surface water (<1 to 2 mg/l). Most of the mass of PCBs in Lake Ontario surface water are also found in the dissolved phase. The absence of BDE-47 and BDE-99 on second XAD columns indicates that all of these congeners were captured by the first XAD column. XAD would appear to be an effective extraction media for these two congeners of interest. The presence of percent levels of PBDE in analytical lab air duct- work points out the need for careful consideration of the chemical composition of all lab building materials when doing low level detection work (pg) for PBDEs. Conclusions Total PBDEs are ~ 4 to 6 pg/L in open waters; PBDE congeners tetra-47BDE & penta-99BDE make up ~60% of total; > 80% of PBDEs are in the dissolved phase; Similar PBDE concentrations and congener distribution across the Lake. Parts per quadrillion concentrations of PBDE can be quantified in surface waters using large volume sampling techniques. Acknowledgements Funding and logistical support was provided by U.S. EPA’s Great Lakes National Program (Chicago Office) and EPA Region 2 (New York Office). Thanks also to the staff at Axys Analytical Special thanks to the Captain and Crew of the R/V Lake Guardian who made this project possible. References 1 Flint, R.W.; Stevens, R.J.J., State University of New York at Buffalo, 1989, Great Lakes Monograph No Luross J.M., Alaee M., Sergeant D., Whittle M., and Solomon K., Spatial and Temporal Distribution of Polybrominated Diphenyl Ethers in Lake Trout from the Great Lakes. Presented at the 2 nd Annual Workshop on Brominated Flame Retardants in the Environment, Burlington, Ontario, June 5-6, De Boer, J.; de Boer, K.; Boon, J.P., Handbook of Env. Chemistry, 2000, 3, Part K, Junk, G. A.; Richard, J.J.; Grieser, M.D.; Witiak, J.L.; Arguello, M.D.; Vick, R.; Svec, H.J.; Fritz, J.S.; Calder, G.V., J. of Chromatography, 1974, 99, Swackhammer, D.L.; Armstrong, D.E., J. Great Lakes Res., 1987, 13, Litten, S.; Donlon, J., Enhanced toxics sampling for trace organics in Lake Ontario New York State Department of Environmental Conservation, Bureau of Watershed Assessment and Research, Division of Water, 50 Wolf Rd., Albany, NY.. Fig. 1 Lake Ontario is the last in the chain of the Great Lakes receiving approximately 90% of its inflow from upstream lakes. Fig. 2 PBDE trends observed in Lake Ontario lake trout tissue (adapted from Luross et al. 2000). ~I meter deep Lake XAD Resin #2 Capture suspended solids Capture “break through” compounds from first XAD column. Nytex Netting XAD Resin #1 Glass Fiber Filter Surface Water Intake Filter out plankton & debris Capture dissolved contaminants Flow Meter Overflow to Lake Fig. 7 Schematic of Large Volume Sampler XAD columns were placed in series to increase the total volume of resin available to capture dissolved contaminants. The extraction efficiency of the first XAD column can be evaluated by analyzing the columns separately. Ideally, no hydrophobic contaminants should be found on the second column. One advantage of large volume sampling is that any detection limit can be achieved provided a large enough sample volume is processed. XAD has been a tool for concentration of environmental contaminants in water for over 25 years 4,5. Western sampling area Eastern Central Lake Ontario Province of Ontario New York State Fig. 6 Fall 1999 Lake Ontario surface water sampling locations. Table 1. Sample volumes (Liters) processed for XAD (dissolved phase) and filter (suspended solids) samples. XAD columns Filter cartridge, glass fiber Fig 8. Large volume sampler ng/g Lipid Frederick Luckey, New York State DEC Simon Litten, New York State DEC Establishing Baseline Levels of PBDEs in Lake Ontario Surface Water Brian Fowler, AXYS Analytical Services