Surface modified materials for active capture of enzymes.

The insertion of bis(diarylcarbene)s onto a glass fiber (GF) membrane surface provided an active coating for the direct capture of protein - exemplified by the enzyme, cellulase - through a mild diazonium coupling process which does not require additional coupling agents. Successful cellulase attachment on the surface was demonstrated by the disappearance of diazonium and formation of azo functions in the N 1s high resolution spectra, the appearance of carboxyl group in C 1s spectra, both observed by XPS; the -CO vibrational bond observed by ATR-IR; as well as the observation of fluorescence. Further, five support materials (polystyrene XAD4 bead, polyacrylate MAC3 bead, glass wool, glass fiber membrane, polytetrafluoroethylene membrane) with different morphology and surface chemistry, were examined in detail as supports for cellulase immobilization using this common surface modification protocol. Of interest is that such covalently bound cellulase on modified GF membrane gave both the highest enzyme loading (∼23 mg cellulase per g support), and retained more than 90% of activity after 6 cycles of re-use, compared with substantial loss of enzyme activity for physiosorbed cellulase after 3 cycles. Optimization of the degree of surface grafting and the effectiveness of a spacer between surface and enzyme for enzyme loading and activity were conducted. This work shows that carbene surface modification is a viable strategy for introducing enzymes onto a surface under very mild conditions and retaining a meaningful level of activity, and particularly, using GF membrane as a novel support provides a potential platform for enzyme and protein immobilization.

Levels and distribution profiles of Per- and Polyfluoroalkyl Substances (PFAS) in a high Arctic Svalbard ice core.

Per- and polyfluoroalkyl substances (PFAS) are a group of persistent organic contaminants of which some are toxic and bioaccumulative. Several PFAS can be formed from the atmospheric degradation of precursors such as fluorotelomer alcohols (FTOHs) as well as hydrochlorofluorocarbons (HFCs) and other ozone-depleting chlorofluorocarbon (CFC) replacement compounds. Svalbard ice cores have been shown to provide a valuable record of long-range atmospheric transport of contaminants to the Arctic. This study uses a 12.3 m ice core from the remote Lomonosovfonna ice cap on Svalbard to understand the atmospheric deposition of PFAS in the Arctic. A total of 45 PFAS were targeted, of which 26 were detected, using supercritical fluid chromatography (SFC) tandem mass spectrometry (MS/MS) and ultra-performance liquid chromatography (UPLC) MS/MS. C2 to C11 perfluoroalkyl carboxylic acids (PFCAs) were detected continuously in the ice core and their fluxes ranged from 2.5 to 8200 ng m-2 yr-1 (9.51-16,500 pg L-1). Trifluoroacetic acid (TFA) represented 71 % of the total mass of C2 - C11 PFCAs in the ice core and had increasing temporal trends in deposition. The distribution profile of PFCAs suggested that FTOHs were likely the atmospheric precursor to C8 - C11 PFCAs, whereas C2 - C6 PFCAs had alternative sources, such as HFCs and other CFC replacement compounds. Perfluorooctanesulfonic acid (PFOS) was also widely detected in 82 % of ice core subsections, and its isomer profile (81 % linear) indicated an electrochemical fluorination manufacturing source. Comparisons of PFAS concentrations with a marine aerosol proxy showed that marine aerosols were insignificant for the deposition of PFAS on Lomonosovfonna. Comparisons with a melt proxy showed that TFA and PFOS were mobile during meltwater percolation. This indicates that seasonal snowmelt and runoff from post-industrial accumulation on glaciers could be a significant seasonal source of PFAS to ecosystems in Arctic fjords.

Levels and Seasonal Trends of C1-C4 Perfluoroalkyl Acids and the Discovery of Trifluoromethane Sulfonic Acid in Surface Snow in the Arctic.

C1-C4 perfluoroalkyl acids (PFAAs) are highly persistent chemicals that have been found in the environment. To date, much uncertainty still exists about their sources and fate. The importance of the atmospheric degradation of volatile precursors to C1-C4 PFAAs were investigated by studying their distribution and seasonal variation in remote Arctic locations. C1-C4 PFAAs were measured in surface snow on the island of Spitsbergen in the Norwegian Arctic during January-August 2019. Trifluoroacetic acid (TFA), perfluoropropanoic acid (PFPrA), perfluorobutanoic acid (PFBA), and trifluoromethane sulfonic acid (TFMS) were detected in most samples, including samples collected at locations presumably receiving PFAA input solely from long-range processes. The flux of TFA, PFPrA, PFBA, and TFMS per precipitation event was in the ranges of 22-1800, 0.79-16, 0.19-170, and 1.5-57 ng/m2, respectively. A positive correlation between the flux of TFA, PFPrA, and PFBA with downward short-wave solar radiation was observed. No correlation was observed between the flux of TFMS and solar radiation. These findings suggest that atmospheric transport of volatile precursors and their subsequent degradation plays a major role in the global distribution of C2-C4 perfluoroalkyl carboxylic acids and their consequential deposition in Arctic environments. The discovery of TFMS in surface snow at these remote Arctic locations suggests that TFMS is globally distributed. However, the transport mechanism to the Arctic environment remains unknown.

The fate of poly- and perfluoroalkyl substances in a marine food web influenced by land-based sources in the Norwegian Arctic.

Although poly- and perfluorinated alkyl substances (PFAS) are ubiquitous in the Arctic, their sources and fate in Arctic marine environments remain unclear. Herein, abiotic media (water, snow, and sediment) and biotic media (plankton, benthic organisms, fish, crab, and glaucous gull) were sampled to study PFAS uptake and fate in the marine food web of an Arctic Fjord in the vicinity of Longyearbyen (Svalbard, Norwegian Arctic). Samples were collected from locations impacted by a firefighting training site (FFTS) and a landfill as well as from a reference site. Mean concentration in the landfill leachate was 643 ± 84 ng L-1, while it was 365 ± 8.0 ng L-1 in a freshwater pond and 57 ± 4.0 ng L-1 in a creek in the vicinity of the FFTS. These levels were an order of magnitude higher than in coastal seawater of the nearby fjord (maximum level , at the FFTS impacted site). PFOS was the most predominant compound in all seawater samples and in freshly fallen snow (63-93% of ). In freshwater samples from the Longyear river and the reference site, PFCA ≤ C9 were the predominant PFAS (37-59%), indicating that both local point sources and diffuse sources contributed to the exposure of the marine food web in the fjord. concentrations increased from zooplankton (1.1 ± 0.32 µg kg-1 ww) to polychaete (2.8 ± 0.80 µg kg-1 ww), crab (2.9 ± 0.70 µg kg-1 ww whole-body), fish liver (5.4 ± 0.87 µg kg-1 ww), and gull liver (62.2 ± 11.2 µg kg-1). PFAS profiles changed with increasing trophic level from a large contribution of 6:2 FTS, FOSA and long-chained PFCA in zooplankton and polychaetes to being dominated by linear PFOS in fish and gull liver. The PFOS isomer profile (branched versus linear) in the active FFTS and landfill was similar to historical ECF PFOS. A similar isomer profile was observed in seawater, indicating major contribution from local sources. However, a PFOS isomer profile enriched by the linear isomer was observed in other media (sediment and biota). Substitutes for PFOS, namely 6:2 FTS and PFBS, showed bioaccumulation potential in marine invertebrates. However, these compounds were not found in organisms at higher trophic levels.