Resonant ion-pair formation in electron recombination with HF^+

The cross section for resonant ion-pair formation in the collision of low-energy electrons with HF^+ is calculated by the solution of the time-dependent Schrodinger equation with multiple coupled states using a wave packet method. A diabatization procedure is proposed to obtain the electronic couplings between quasidiabatic potentials of ^1Sigma^+ symmetry for HF. By including these couplings between the neutral states, the cross section for ion-pair formation increases with about two orders of magnitude compared with the cross section for direct dissociation. Qualitative agreement with the measured cross section is obtained. The oscillations in the calculated cross section are analyzed. The cross section for ion-pair formation in electron recombination with DF^+ is calculated to determine the effect of isotopic substitution.Comment: 12 pages, 12 figure

Quantitative biomonitoring of PAHs using the barnes mussel (Elliptio complanata)

The elimination rate constants (k2) of nine polycyclic aromatic hydrocarbons (PAHs) were examined for the freshwater mussel Elliptio complanata. The concentrations of fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benzo[a]anthracene, chrysene, benzo[b]fluoranthene, and indeno[1,2,3-c,d]-pyrene revealed a significant inverse relationship with time and their k2 values ranged from 0.10 to 0.22 day-1. The k2 values of these significantly cleared PAHs were similar to k2 values observed for nonmetabolized organochlorines in mussels previously reported in the literature. The inverse relationship between k2 and Kow provides evidence that the nine PAHs were being passively eliminated from the mussels and that they can be used to calibrate the mussel as a quantitative biomonitor. A general expression relating elimination rate constants and chemical Kow is derived for hydrophobic contaminants in E. complanata. The k2 versus log Kow regression equation for mussels developed herein was similar to other studies documenting the elimination of PCBs and PAHs in a number of bivalve species

Polybrominated diphenyl ethers (PBDEs) in Great Lakes fish: Levels, patterns, trends and implications for human exposure

Levels of polybrominated diphenyl ethers (PBDEs) were measured in edible portions of Great Lakes fish, with the goal of examining patterns/trends and evaluating implications for human exposure. A total of 470 fillets of 18 fish species collected from various parts of the Canadian waters of the Great Lakes between 2006 and 2013 were analyzed for 17 (expanded to 33 in 2009) PBDEs. For a limited number of species, fillet to whole body and fillet to eggs PBDEs were compared to examine pattern and concentration among tissue types. Levels and patterns of PBDEs varied dramatically within and among the 18 fish species. Bottom dwelling Common Carp (and White Sucker) exhibited the highest ∑ PBDE levels (27–71 ng/g). Lake Trout and Lake Whitefish from Lake Superior had higher levels than those from the other Great Lakes; otherwise the spatial trend was Lake Ontario ≫ Erie ~ Huron ~ Superior. The measured levels would result in restriction on consumption of only Common Carp from the Toronto waterfront area, which is in proximity to the most urbanised region on the Canadian side of the basin. Deca-BDE was the major congener in panfish, while BDE-47 was the major congener in top predators and its contribution to ∑ PBDE increased with the contamination. Although ∑ PBDE was related to fish length and lipid content when all measurements were pooled, the relationships were variable for individual sampling events (species/location/year). Whole body ∑ PBDE for bottom dweller Brown Bullhead and Common Carp were 2.6–4.9 times greater and egg ∑ PBDE for four fatty Salmon/Trout species were same to 6.5 times greater than the corresponding fillet concentrations. Levels of major lower brominated PBDEs appear to have declined in fish fillets by 46–74% between 2006/07 and 2012. Although PBDE in existing consumer items will remain in-use for a while, it will likely not result in appreciable accumulation of PBDEs in fish. Based on an overall assessment, regular monitoring of PBDEs in Great Lake fish can be replaced with targeted surveillance and focus can be shifted to other in-use flame retardants. © 201

High levels, partitioning and fish consumption based water guidelines of perfluoroalkyl acids downstream of a former firefighting training facility in Canada

High levels of perfluoroalkyl acids (PFAAs), especially perfluorooctane sulfonic acid (PFOS), have been observed at locations in/around/downstream of the sites where PFOS-based firefighting foam was used repeatedly for a prolonged period. In this study, we conducted a detailed investigation of PFAA contamination in the Lake Niapenco area in Ontario, Canada, where among the highest ever reported levels of PFOS were recently measured in amphipods, fish and snapping turtle plasma. Levels and distribution of PFAAs in water, sediment and fish samples collected from the area varied widely. An upstream pond beside a former firefighting training area (FFTA) was confirmed as the source of PFAAs even 20 years after the last use of the foam at the FFTA. Recent PFOS concentration in water (~ 60 ng/L) at Lake Niapenco, about 14 km downstream of the pond, was still 3–7 × higher than the background levels. For PFOS, Log KD ranged 1.3–2.5 (mean ± SE: 1.7 ± 0.1), Log BAFs ranged 2.4–4.7 (3.4 ± 0.05), and Log BSAFs ranged 0.7–2.9 (1.7 ± 0.05). Some fish species-specific differences in BAF and BSAF were observed. At Log BAF of 4.7, fish PFOS levels at Lake Niapenco could reach 15,000 ng/g, 100 × greater than a “do not eat” advisory benchmark, without exceeding the current drinking water guideline of 300 ng/L. A fish consumption based water guideline was estimated at 1–15 ng/L, which is likely applicable worldwide given that the Log BAFs observed in this study were comparable to those previously reported in the literature. It appears that PFAA in the downstream waters increased between 2011 and 2015; however, further monitoring is required to confirm this trend. © 201

High levels of perfluoroalkyl acids in sport fish species downstream of a firefighting training facility at Hamilton International Airport, Ontario, Canada

A recent study reported elevated concentrations of perfluorooctane sulfonic acid (PFOS) and other perfluoroalkyl acids (PFAAs) in surface water, snapping turtles, and amphipods in Lake Niapenco, downstream of Hamilton International Airport, Ontario, Canada. Here, our goals were to 1) determine the extent of PFAA contamination in sport fish species collected downstream of the airport, 2) explore if the airport could be a potential source, and 3) compare fish PFOS concentrations to consumption advisory benchmarks. The PFOS levels in several sport fish collected from the three locations closest to the airport (. 70. km) were comparable to or below the average concentrations in fish as observed in the literature and were generally below the benchmarks. With regards to perfluorocarboxylates (PFCAs), there was no significant decrease in concentrations in fish with distance from the airport and levels were comparable to or below the average concentrations observed in the literature, suggesting that the airport is not a significant source of PFCAs in these fish species. PFOS-based aqueous film-forming foam (AFFF) was used at a firefighting training facility at the airport in the 1980s to mid-1990s. Taken together, our results provide evidence that the historical use of AFFF at the airport has resulted in fish PFOS concentrations that exceed the 95th percentile concentration of values reported in the literature to date. © 2014

Spatial and temporal variability of PCBs in Detroit River water assessed using a long term biomonitoring program

An assessment of polychlorinated biphenyls (PCBs) in water of the Detroit River, North America, was performed using mussel biomonitoring data generated between 1996 and 2010. The study included a temporal monitoring program at six locations and an enhanced spatial survey performed during 2002. Mussels were transplanted at biomonitoring stations and collected after 21-226d. A toxicokinetic model was used to perform steady state and control corrections followed by an equilibrium partitioning model to estimate bioavailable water concentrations of PCBs. Bioavailable water concentrations of PCBs were similar in magnitude and trends to dissolved water concentrations reported in previous studies using direct sampling approaches. PCB concentrations exhibited complex temporal patterns at the six biomonitoring stations with multi-year declines in PCB trajectories between 1996 and 2002 and less consistent trends occurring across stations in later years. Spatial patterns of PCBs during 2002 revealed significantly higher water contamination on the US side of the river (seasonal average mean±standard error (SE) sum PCB concentration of 0.63±0.11ngL-1) compared to the Canadian side (mean±SE sum PCB concentration of 0.09±0.01ngL-1). Spatial/temporal variability of bioavailable PCB concentrations was greatest between countries, followed by moderate variation across years and by river reach (upstream, midstream and downstream sections within a country) and lowest when comparing intra-seasonal variation. © 2012 Elsevier Ltd