Spatial Distribution, Air-Water Fugacity Ratios and Source Apportionment of Polychlorinated Biphenyls in the Lower Great Lakes Basin

Polychlorinated biphenyls (PCBs) continue to be contaminants of concern across the Great Lakes. It is unclear whether current concentrations are driven by ongoing primary emissions from their original uses, or whether ambient PCBs are dominated by their environmental cycling. Freely dissolved PCBs in air and water were measured using polyethylene passive samplers across Lakes Erie and Ontario during summer and fall, 2011, to investigate their spatial distribution, determine and apportion their sources and to asses their air–water exchange gradients. Average gaseous and freely dissolved ∑29 PCB concentrations ranged from 5.0 to 160 pg/m3 and 2.0 to 55 pg/L respectively. Gaseous concentrations were significantly correlated (R2 = 0.80) with the urban area within a 3−20 km radius. Fugacity ratios indicated that the majority of PCBs are volatilizing from the water thus acting as a secondary source for the atmosphere. Dissolved PCBs were probably linked to PCB emissions from contaminated sites and areas of concern. Positive matrix factorization indicated that although volatilized Aroclors (gaseous PCBs) and unaltered Aroclors (dissolved PCBs) dominate in some samples, ongoing non-Aroclor sources such as paints/pigments (PCB 11) and coal/wood combustion showed significant contributions across the lower Great Lakes. Accordingly, control strategies should give further attention to PCBs emitted from current use sources

Synthetic organic toxicants in Lake Superior

Numerous synthetic organic toxicants have been reported in Lake Superior in the past quarter century although relatively few industrial centers are located on its shores. The chemicals enter the lake primarily through atmospheric deposition via transport from regional and distant sources. This contribution discusses research issues regarding the processes by which the chemicals enter and exit the lake, their in-lake cycling and bioaccumulation, and recently reported potential toxicological effects. Research issues that remain for historically important synthetic organic toxicants are discussed as well as those of emerging chemicals of concern. Although concentrations of some historically important toxicants are decreasing in Lake Superior\u27s waters through volatilization and sedimentation and burial, abiotic and biotic in-lake cycling opens routes of entry into the lake\u27s lower food web, contributing to concentrations in fish that warrant consumption advisories in certain cases. Concentrations of some non-polar emerging chemicals of concern that are increasing in production (such as polybrominated diphenyl ethers) can be expected to increase in the lake and be subject to similar processes occurring to historically important persistent organic pollutants unless regulatory intervention leads to decreasing atmospheric emissions. Other emerging chemicals of concern await measurement in Lake Superior. Our ability to understand the fate and effects of synthetic organic toxicants on the Lake Superior ecosystem, whether they are \u27legacy\u27 chemicals or emerging chemicals of concern, is limited by the availability of techniques to determine physical-chemical properties, concentrations, fluxes, bioaccumulation pathways and rates, and mechanisms of toxicity. Future research on synthetic organic toxicants in Lake Superior relies on advances in development of these techniques. Policy decisions must take into account the variety factors that lead to the presence of the chemicals in the lake and their toxic effects

Perfluoroalkyl Substances Increase the Membrane Permeability and Quorum Sensing Response in <i>Aliivibrio fischeri</i>

Perfluoroalkyl substances (PFAS) are used in a variety of products and are ubiquitous in the environment. They have been found to associate with eukaryotic cell membranes and alter membrane properties. Bacteria are exposed to elevated concentrations of PFAS in some environments; nevertheless, the effect of PFAS exposure on microbial membranes has not yet been studied. Some quorum sensing pathways require the passive diffusion of signaling molecules through cell membranes. Quorum sensing initiates a variety of bacterial processes, such as biofilm formation and antibiotic production. If PFAS exposure increased the microbial quorum sensing response, these processes could be initiated at lower population densities, with wide-ranging ramifications for PFAS-impacted environments. This study examined the effect of perfluorinated alkyl sulfonates and carboxylates on quorum sensing in a model bacterium, <i>Aliivibrio fischeri</i>. Results showed that cultures exposed to PFAS were brighter after they received the signaling molecule. The observed increase in luminescence was dose-dependent and increased with the fluorinated carbon number. Specifically, perfluorooctanesulfonate increased luminescence at levels as low as 10 μg/L. PFAS-exposed bacteria were also more permeable to a semi-membrane permeable dye. Therefore, it is likely that increased permeability was, at least in part, the cause of increased luminescence