Fluorochemicals (FCs) are oxidatively recalcitrant, environmentally persistent, and resistant to most conventional treatment technologies. FCs have unique physiochemical properties derived from fluorine which is the most electronegative element. Perfluorooctanesulfonate (PFOS), and perfluorooctanoate (PFOA) have been detected globally in the hydrosphere, atmosphere and biosphere. Reducing treatment technologies such as reverses osmosis, nano-filtration and activated carbon can remove FCs from water. However, incineration of the concentrated waste is required for complete FC destruction. Recently, a number of alternative technologies for FC decomposition have been reported. The FC degradation technologies span a wide range of chemical processes including direct photolysis, photocatalytic oxidation, photochemical oxidation, photochemical reduction, thermally-induced reduction, and sonochemical pyrolysis. This paper reviews these FC degradation technologies in terms of kinetics, mechanism, energetic cost, and applicability. The optimal PFOS/PFOA treatment method is strongly dependent upon the FC concentration, background organic and metal concentration, and available degradation time.

Treatment technologies for aqueous perfluorooctanesulfonate (PFOS) and perfluorooctanoate (PFOA)

The overlooked short- and ultrashort-chain poly- and perfluorinated substances: A review.

Perfluorinated chemicals (PFCs) are distributed throughout the environment. In the case of perfluorinated alkyl carboxylates and sulfonates, they can be classified as persistent organic pollutants since they are resistant to environmentally relevant reduction, oxidation, and hydrolytic processes. With this in mind, we report on the reductive defluorination of perfluorobutanoate, PFBA (C_3F_7CO_2−), perfluorohexanoate, PFHA (C_5F_(11)CO_2−), perfluorooctanoate, PFOA (C_7F_(15)CO_2−), perfluorobutane sulfonate, PFBS (C_4F_9SO_3−), perfluorohexane sulfonate, PFHS (C_6F_(13)SO_3−), and perfluorooctane sulfonate, PFOS (C_8F_(17)SO_3−) by aquated electrons, eaq−, that are generated from the UV photolysis (λ = 254 nm) of iodide. The ionic headgroup (-SO_3− vs -CO_2−) has a significant effect on the reduction kinetics and extent of defluorination (F index = −[F−]_(produced)/[PFC]_(degraded)). Perfluoroalkylsulfonate reduction kinetics and the F index increase linearly with increasing chain length. In contrast, perfluoroalkylcarboxylate chain length appears to have a negligible effect on the observed kinetics and the F index. H/F ratios in the gaseous fluoro-organic products are consistent with measured F indexes. Incomplete defluorination of the gaseous products suggests a reductive cleavage of the ionic headgroup occurs before complete defluorination. Detailed mechanisms involving initiation by aquated electrons are proposed.

Reductive defluorination of aqueous perfluorinated alkyl surfactants: effects of ionic headgroup and chain length.

Numerous international scientific assessments and related articles have, during the last decade, described the observed and potential impacts of climate change as well as other related environmental stressors on Arctic ecosystems. There is increasing recognition that observed and projected changes in freshwater sources, fluxes, and storage will have profound implications for the physical, biogeochemical, biological, and ecological processes and properties of Arctic terrestrial and freshwater ecosystems. However, a significant level of uncertainty remains in relation to forecasting the impacts of an intensified hydrological regime and related cryospheric change on ecosystem structure and function. As the terrestrial and freshwater ecology component of the Arctic Freshwater Synthesis, we review these uncertainties and recommend enhanced coordinated circumpolar research and monitoring efforts to improve quantification and prediction of how an altered hydrological regime influences local, regional, and circumpolar-level responses in terrestrial and freshwater systems. Specifically, we evaluate (i) changes in ecosystem productivity; (ii) alterations in ecosystem-level biogeochemical cycling and chemical transport; (iii) altered landscapes, successional trajectories, and creation of new habitats; (iv) altered seasonality and phenological mismatches; and (v) gains or losses of species and associated trophic interactions. We emphasize the need for developing a process-based understanding of interecosystem interactions, along with improved predictive models. We recommend enhanced use of the catchment scale as an integrated unit of study, thereby more explicitly considering the physical, chemical, and ecological processes and fluxes across a full freshwater continuum in a geographic region and spatial range of hydroecological units (e.g., stream-pond-lake-river-near shore marine environments).

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/2015JG003133

Transitions in Arctic ecosystems: Ecological implications of a changing hydrological regime

Recent trends in the liquid chromatography-mass spectrometry analysis of organic contaminants in environmental samples.

The presence of perfluorocarboxylates (PFCAs) in the environment is of increasing concern, following the discovery of perfluoroalkyl acids (PFAs) in wildlife and human samples. Here we report a method forthe determination of (C2-C9) PFCAs by preparing the 2,4-difluoroanilides of the acids and analyzing by using GC-MS. Detector response was linear over the range 0.1 -1000 pg of each perfluoroalkyl anilide. A complete suite of PFCAs can be analyzed in an individual sample with the PFCAs detected at levels similar to or lower than those determined by other methods. For a comparison between the present method and the more common LC-MS/MS method, 10 replicates of a sewage treatment plant discharge were analyzed for perfluoro-octanoic acid (PFOA) using both methods. Results were nearly identical with low standard deviation (GC-MS 30.9 +/- 1.88 ng/L; while the LC-MS/MS 34.7 +/- 3.05 ng/L). PFCA concentrations for water samples collected from depth profiles in mid-Lake Ontario were analyzed by GC-MS with most PFCAs (C2-C8) present above the detection limit (0.5 ng/L). Major PFCAs were trifluoroacetate (TFA) (100 ng/L) and perfluorobutanoate (PFBA) (> 5 ng/L). Results for PFOA (2.5 ng/L) were in good agreement with recent analyses by LC-MS/MS. PFCAs were also detected in the precipitation samples at concentrations lower than those of the samples from the lake profiles or sewage treatment plants (STPs) effluent. Since PFOA levels may be less than the lower detection limit (<0.5 ng/L) in 1 L samples, a method for large volumes using XAD-7 resin was developed that allows detection to 0.01 ng/L. This method was applied to Lake Superior samples which produced good agreement for C6-C9 PFCAs between regular analysis (GC-MS) and the XAD-7 followed by GC-MS analysis.

Analysis for perfluorocarboxylic acids/anions in surface waters and precipitation using GC--MS and analysis of PFOA from large-volume samples.

Perfluorinated chemicals (PFCs) have been recorded in many types of marine and freshwater ecosystems. The aim of the present study was to examine meromictic lakes and their catchments on the far northern coast of Ellesmere Island, Nunavut, Canada, and to evaluate the results in the context of climate change. Our analyses revealed the presence of several PFCs in catchment snowpack, inflowing streams, lake water, and the aquatic food web of Lake A (83˚00 ʹ N, 75˚30ʹ W), showing that dispersal of these contaminants reaches the northern limit of the terrestrial High Arctic. However, the concentrations were low (total PFCs: 27 - 754 pg L -1 for water, 134 - 848 pg L -1 for melted snow, 5 - 2149 pg g -1 wet weight for fish; PFOS: 66 pg g -1 dry weight in surficial sediments) and at or below values reported to date in the literature for other remote lakes. PFHpA, PFOA, and PFNA were the main compounds detected in water and melted snow, while PFNA, PFDA, and PFUnA were the predominant compounds in the aquatic biota, indicating their bioaccumulative potential. Salinity-temperature-depth profiles suggested that most of the present contaminant load enters the lake via streams and flows directly under the lake ice to the ocean. The onset of summer open water in this perennially ice-covered lake in response to climate warming, and the increased duration of open water in recent years, have implications for the distribution, transport, and retention of PFCs in Arctic lakes.

http://pubs.aina.ucalgary.ca/arctic/Arctic65-3-245.pdf

Perfluorinated Chemicals in Meromictic Lakes on the Northern Coast of Ellesmere Island, High Arctic Canada

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Analysis for perfluorocarboxylic acids/anions in surface waters and precipitation using GC--MS and analysis of PFOA from large-volume samples.

Perfluorinated Chemicals in Meromictic Lakes on the Northern Coast of Ellesmere Island, High Arctic Canada