PCDD/Fs, dioxin-like, and non-dioxin like PCBs in the sediments of high Arctic fjords, Svalbard

Polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) are highly toxic organic compounds, and very few studies on their presence in polar environments have been conducted. This study assessed the concentration and distribution of PCDD/Fs, dioxin-like polychlorinated biphenyls (DL-PCBs), and non-dioxin-like polychlorinated biphenyls in selected fjords of the Svalbard archipelago in Norway. The ∑PCDD/Fs observed for Raudfjorden, Smeerenburgfjorden, Magdalenefjorden, and Kongsfjorden were 22.80 pg/g, 25.65 pg/g, 18.27 pg/g, 33.50 pg/g, and 21.69 pg/g, respectively. The WHO's toxic equivalents values of both ∑PCDD/Fs and ∑DL-PCBs were comparatively higher than those reported in other polar regions. Of the four fjords studied, the sediments from Kongsfjorden exhibited the presence of the most toxic materials, including PCB-126 and PCB-169, of DL-PCBs. More than 80% of the total analysed PCDD/Fs were comprised of highly chlorinated congeners (hexa-to-octa forms). More studies are required to understand the destination and transport of these hazardous pollutants in high Arctic sediments.

Mercury in the sediments of freshwater lakes in Ny-Ålesund, Arctic

Mercury and its speciation in aquatic ecosystems have been assessed globally. Even though previous studies were limited to Arctic freshwater lakes, they are highly significant in the context of the changing climate. The present study is based on sediment samples collected from three Arctic freshwater lakes over a period of 4 years (2015-2018). The samples were analysed for total mercury (THg), methyl mercury (MHg), and various mercury fractions. The observed mean THg and MHg concentrations were 22.23 ng/g and 0.41 ng/g respectively; these values were comparable with those for other Arctic freshwater lakes. The mercury content significantly varied among the years as well as among the lakes. Changes in snowdrift and meltwater inputs, which are the major sources of water for the lakes, may have influenced the sediment mercury content along with geographical location and increased productivity. The results of MHg indicated the susceptibility of lake sediments to methylation. The major fractions observed were the organo-chelated form of mercury, followed by the elemental and water-soluble forms. These results indicate the availability of mercury for methylation. Hence, it is necessary to conduct more studies on the influence of climate change, mercury release through permafrost melting, and atmospheric deposition.

Rate of sediment accumulation and historic metal contamination in a tidewater glacier fjord, Svalbard

The sedimentation rates in Arctic fjords are influenced by the changes in the glacial inputs. The recent studies have indicated the retreat of glaciers due to climate change and subsequent increase in melt water outflow with high content of debris. The debris may contain natural and anthropogenically originated contaminants. The present study analysed the sedimentation rate in inner Kongsfjorden, Ny-Ålesund, Svalbard using ²¹⁰Pb/²¹⁰Po dating technique. The sedimentation rate ranged between 0.22 and 0.37 cm/year during the last 112 years. The average sedimentation rate obtained was 0.28 cm/y. The rate has been increased during the last 20 years and it might be due to the increased influx of glacial melt water containing debris. Metals and other elements showed an increasing trend towards the surface and observed high deposition rate since 1970s, indicating influence of industrial emissions and it can be a potential threat to Arctic biota.

Relative affinities of bovine brain 14 kDa galactose lectin binding to individual endogenous gangliosides

Sugar-specific binding of bovine brain 14 kDa galactose-binding lectin (BBL) to individual endogenous gangliosides (GM1, GM2, GD1a, GD1b and GT1b) was studied using affinity electrophoresis of ganglioside-lectin mixture in polyacrylamide gel at pH 8.3. Unbound (free) lectin moved ahead while ganglioside-lectin complex moved very little. Sugar-specificity of binding was confirmed by reversal of the interaction by (i) presence of lactose along with the lectin and (ii) pretreatment of gangliosides with another galactose-binding lectin, Ricinus communis agglutinin. Stoichiometry of ganglioside-BBL interaction revealed that GT1b had the highest affinity for the lectin followed by GD1b and GM2, while GM1 and GD1a had the least affinity. Results indicated that a terminal sialic acid moiety covering a galactose moiety may at times enhance BBL recognition of the latter and that changes in ganglioside pattern is a possible modulator of lectin function in vivo.

Major bovine brain stem glycoproteins sugar-specifically recognized by endogenous 14 kDa galactose-binding lectin

In order to identify the complementary glycoproteins (receptors) that are recognized in bovine brain stem by endogenous 14 kDa galactose-binding lectin (BBL), probable glycoproteins were first selected by affinity chromatography of soluble tissue glycoproteins on Rinicus communis agglutinin (RCA)-Sepharose since this lectin had similar sugar specificity to the endogenous lectin. From Western blot of RCA-binding glycoproteins, the lectin, as its peroxidase conjugate sugar-specifically recognized chiefly an 84 kDa glycoprotein subunit and a few minor subunits. On alkaline pH PAGE of the RCA-binding brain stem glycoproteins, a prominent fast moving protein was separated which, on electroelution and dot blotting, was also recognized by BBL sugar-specifically. This glycoprotein was composed of 55 kDa and 58 kDa subunits as seen by SDS-PAGE and was also immunologically distinct from the 84 kDa subunit. Qualitative test on dot blots of the electroeluted glycoproteins using peroxidase conjugates of plant lectins of varying specificities as well as the human serum anti-alpha-galactoside antibody indicated differences in carbohydrate composition between the 84 kDa subunit and the alkaline PAGE fast moving glycoprotein. Membrane-bound brain stem glycoproteins were not recognized by BBL.

Sugar-specific interaction of bovine brain beta-galactoside-binding lectin with endogenous gangliosides

Sugar-specific binding of the 14 kDa beta-galactoside-binding lectin from bovine brain grey matter to mixed endogenous gangliosides was demonstrated by affinity electrophoresis and hemagglutination inhibition. Gangliosides prepared by Folch extraction, base treatment and silica gel chromatography, when incorporated in native or desialated form in polyacrylamide gel above their critical micellar concentration, arrested the mobility of the lectin during electrophoresis at pH 8.2. This effect was sugar-specific since it was reversed if lactose, but not sucrose, was present in the gel. Also, retention of the brain lectin by ganglioside and its reversal by lactose were concentration-dependent. In presence of bovine serum albumin, at pH 7.4 native and desialylated gangliosides equally inhibited agglutination of trypsinized rabbit red cells by bovine brain lectin, but not that by the alpha-galactoside-specific antibody from human serum. Results suggested the possibility of endogenous gangliosides acting as cell surface receptors in mediation of brain lectin function.