Accumulation of atmospheric radionuclides and heavy metals in cryoconite holes on an Arctic glacier

Arctic plasmidome analysis reveals distinct relationships among associated antimicrobial resistance genes and virulence genes along anthropogenic gradients

Polar regions are relatively isolated from human activity and thus could offer insight into anthropogenic and ecological drivers of the spread of antibiotic resistance. Plasmids are of particular interest in this context given the central role that they are thought to play in the dissemination of antibiotic resistance genes (ARGs). However, plasmidomes are challenging to profile in environmental samples. The objective of this study was to compare various aspects of the plasmidome associated with glacial ice and adjacent aquatic environments across the high Arctic archipelago of Svalbard, representing a gradient of anthropogenic inputs and specific treated and untreated wastewater outflows to the sea. We accessed plasmidomes by applying enrichment cultures, plasmid isolation and shotgun Illumina sequencing of environmental samples. We examined the abundance and diversity of ARGs and other stress-response genes that might be co/cross-selected or co-transported in these environments, including biocide resistance genes (BRGs), metal resistance genes (MRGs), virulence genes (VGs) and integrons. We found striking differences between glacial ice and aquatic environments in terms of the ARGs carried by plasmids. We found a strong correlation between MRGs and ARGs in plasmids in the wastewaters and fjords. Alternatively, in glacial ice, VGs and BRGs genes were dominant, suggesting that glacial ice may be a repository of pathogenic strains. Moreover, ARGs were not found within the cassettes of integrons carried by the plasmids, which is suggestive of unique adaptive features of the microbial communities to their extreme environment. This study provides insight into the role of plasmids in facilitating bacterial adaptation to Arctic ecosystems as well as in shaping corresponding resistomes. Increasing human activity, warming of Arctic regions and associated increases in the meltwater run-off from glaciers could contribute to the release and spread of plasmid-related genes from Svalbard to the broader pool of ARGs in the Arctic Ocean.

Spatial distribution characteristics of soil heavy metals in Sabao Chaqu watershed of Tuotuo river, Qinghai-Tibet Plateau based on geographic detector

The Qinghai-Tibet Plateau belongs to the area of extremely fragile environment and sensitive to human activities. In recent years, more and more human interference has been detected in this area. In this study, 128 surface soil samples were collected from the Sabao Chaqu watershed of the Tuotuo river at the source of the Yangtze River on the Qinghai-Tibet Plateau. The soil pollution status and spatial distribution characteristics of Cd, Hg, As, Cu, Pb, Cr, Zn and Ni were evaluated by soil accumulation index, enrichment factor, pollution index and geographical detector. The results showed that the average contents of As, Cd, Pb and Zn in the study area were 1.2-3.64 times higher than soil background values of Tibet, while the contents of Hg, Cr, Cu and Ni were lower than the background values, while the average content of As was higher than the soil pollution risk screening value (GB15618-2018), and the pollution index showed that As was in a low pollution state, while the other 7 heavy metals were in a safe state. There were significant differences in the spatial distribution of 8 heavy metals and there was a significant correlation with soil properties and distance factors. Factor detection showed that natural factors had the strongest explanatory power to the contents of As, Cd, Cr, Cu and Ni, distance from the lake and soil Sc content had the strongest explanatory power to Hg content, and anthropogenic factors had the strongest explanatory power to Pb content. Interaction detection revealed that the q values of the strongest interaction explanatory power for As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn were 2.81, 4.30, 1.26, 2.47, 2.33, 1.59, 6.37, and 5.08 times higher than their strongest factor detection explanatory power, respectively. The interaction between anthropogenic factors and other factors has an important influence on the spatial differentiation of heavy metals in the study area. Risk detection showed that the average contents of As, Cd, Cr, Cu, Hg, Ni, Pb and Zn were the highest in the subregions of MgO, TS, Sc, X6, X13, MgO, TN and X4, respectively. Comprehensive study shows that the spatial differentiation of As, Cd, Cr, Cu, Ni and Zn is mainly affected by natural factors, but there are also some anthropogenic factors, the spatial differentiation of Hg is affected by both natural factors and atmospheric deposition, and the spatial distribution characteristics of Pb are mainly affected by anthropogenic factors.

Exploring bacterial diversity in Arctic fjord sediments: a 16S rRNA-based metabarcoding portrait

The frosty polar environment houses diverse habitats mostly driven by psychrophilic and psychrotolerant microbes. Along with traditional cultivation methods, next-generation sequencing technologies have become common for exploring microbial communities from various extreme environments. Investigations on glaciers, ice sheets, ponds, lakes, etc. have revealed the existence of numerous microorganisms while details of microbial communities in the Arctic fjords remain incomplete. The current study focuses on understanding the bacterial diversity in two Arctic fjord sediments employing the 16S rRNA gene metabarcoding and its comparison with previous studies from various Arctic habitats. The study revealed that Proteobacteria was the dominant phylum from both the fjord samples followed by Bacteroidetes, Planctomycetes, Firmicutes, Actinobacteria, Cyanobacteria, Chloroflexi and Chlamydiae. A significant proportion of unclassified reads derived from bacteria was also detected. Psychrobacter, Pseudomonas, Acinetobacter, Aeromonas, Photobacterium, Flavobacterium, Gramella and Shewanella were the major genera in both the fjord sediments. The above findings were confirmed by the comparative analysis of fjord metadata with the previously reported (secondary metadata) Arctic samples. This study demonstrated the potential of 16S rRNA gene metabarcoding in resolving bacterial composition and diversity thereby providing new in situ insights into Arctic fjord systems.

Impacts of anthropogenic activities and glacial processes on the distribution of chemical elements in Billefjord, Svalbard, Arctic

The Arctic region is undergoing rapid and extensive transformations due to global climate change. This study investigated the spatial distribution of 31 chemical elements in eight locations in Billefjord, Svalbard, Arctic, with varying degrees of anthropogenic and glacial influences. The west coast of Billefjord has experienced a greater historical anthropogenic impact, while the east coast has larger glaciers and shows less visible evidence of direct human impact. Over 450 topsoil samples collected in the west (abandoned mining town Pyramiden, and glacial valleys of Elsa, Ferdinand, Sven) and east coast of the fjord (glacial valleys of Ebba, Pollock, Ragnar and nearby the Nordenskiöld glacier). These samples were extracted and analyzed by ICP-OES. The results revealed complex distributions of elements among the locations. Nordenskiöld glacier area, along with other locations in the eastern part of the Billefjord, had significantly higher levels of most elements (20 out of 31; As, B, Ca, Cd, Co, Cr, Cu, K, Li, Mg, Mo, Sb, Se, Sn, Sr, Ti, Tl, U, V, Zr). In contrast, Ferdinand Valley and other locations on the western side of the fjord had the lowest mean concentrations of most elements (18 out of 31; B, Ca, Cu, Cd, K, Li, P, Mg, Mo, Sb, Se, Sn, Sr, Ti, Tl, U, V, Zr). These findings highlight the significant influence of glacial processes on the elemental composition of soils within the region. The meltwater flow originating from glaciers in the sampled valleys contributes to the local element load, while the loss of glacier mass is associated with decreased element concentrations within these valleys. These results underscore the complexity of element distribution in the study area and emphasize the necessity for continuous monitoring efforts in this unique and environmentally sensitive region.

Unveiling threats to glacier biota: Bioaccumulation, mobility, and interactions of radioisotopes with key biological components

Contemporary melting glaciers are considered a secondary source of pollutants including radionuclides. Cryoconite - biogenic sediment on the glacier surface - exhibits high concentrations of natural and anthrophogenic radioisotopes. Understanding the interactions between radioisotopes and organisms is essential for evaluating their potential impact on glacier-related ecosystems. Using a multidimensional approach and intensive sampling (17 glaciers), we investigated the relationships between activity concentrations of 137Cs and 210Pb and various biotic components of cryoconite such as the amount of organic matter, chlorophyll concentration, the ratio of cyanobacteria to all bacteria, and size of cryoconite granules. Additionally, to better understand the bioavailability and fate of radioisotopes in this ecosystem, we measured the uptake ratio of 137Cs, 210Pb, 238Pu, and 239+240Pu in the top consumers, and examined the mobility of radioisotopes by measuring 137Cs and 210Pb activity concentrations after a parallel extraction using media with different specific ion exchange capacities. The activity concentrations of both 137Cs and 210Pb showed a large variability reaching 5.8 kBq kg-1 and 7.2 kBq kg-1, respectively. Their activity concentrations were positively related to the amount of organic matter, however, the 210Pb also increased with the chlorophyll concentration. This might be due to the difference in the deposition of both elements: lead, being deposited constantly, binds also to currently developing communities, while caesium deposition peaked in the 1960s. The mobility analysis revealed that the loosely bound fraction of 210Pb was more strongly related to organic-metallic complexes than 137Cs. Firmly bound radioisotope fractions (anhydrous interlayer sites of minerals) were three times higher for 137Cs than for 210Pb. The median uptake ratios of radioisotopes were determined as 0.07-0.111 for 137Cs, 0.177 for 210Pb, 0.07 for 239+240Pu. Our findings emphasize the importance of organisms in the accumulation of radioisotopes on glaciers and suggest an impact of radionuclides on glacier organisms.

Distribution of 137Cs in the marine environment from King George Island (Southern Shetlands, maritime Antarctica)

The article presents data on the activity of the radionuclide 137Cs in seawater, sediment, macroalgae, and zoobenthos from different locations in Admiralty Bay, King George Island, maritime Antarctica. The activity of 137Cs in the macrophytobenthos remained relatively stable across species, oscillating at the level of 1 Bq kg-1dw. However, a few individuals exhibited higher activity, particularly at stations closer to the glacier front. This result could have been caused by specific conditions resulting from melting glaciers and meltwater inflow and mixing with oceanic water. The activities of 137Cs in zoobenthic were in the range from 0.12 Bq kg-1dw (Asteroidea) to 24.2 Bq kg-1dw (Porifera) and the total doses in marine species were several orders of magnitude lower than reference levels. Stable isotopes of δ13C and δ15N suggest that the main factor influencing 137Cs activity may be the source of carbon (marine vs. terrestrial/glacial), rather than feeding strategy or trophic niches.

137Cs and isotopic ratios of Pu and U in lichens and mosses from Russian Arctic areas

Knowledge of past anthropogenic sources of radionuclide contamination in Russian Arctic areas is important to assess the radioecological situation of these less-studied regions. Therefore, we investigated the sources of radionuclide contamination in Russian Arctic in the 1990s. Lichen and moss samples were collected from 1993 to 1996 in Kola Peninsula, Franz Josef Land, and few other locations. The activity concentration of 137Cs was determined from the archived samples by gamma spectrometry in 2020. After radiochemical separation of Pu and U isotopes from the lichens and mosses, mass ratios 240Pu/239Pu, 234U/238U, 235U/238U, and 236U/238U were determined by mass spectrometry. 137Cs activity concentrations at the sampling date were found to vary from 3.1 ± 1.4 (Inari, Finnish-Russian border) to 303 ± 7 (Kola Peninsula) Bq/kg. The ranges of isotopic ratios were 0.0592 ± 0.0007 to 0.253 ± 0.082 for 240Pu/239Pu, (4.89 ± 3.91) × 10-5 to (6.86 ± 0.04) × 10-5 for 234U/238U, 0.0072104(21) to 0.007376(41) for 235U/238U, and from below 1 × 10-7 to (2.65 ± 0.19) × 10-6 for 236U/238U, respectively. Based on the measured isotopic ratios and characteristic isotopic ratios of known contamination sources, the main Pu and U sources in the sampled lichens and mosses are global fallout, the Chernobyl accident, and possibly local nuclear activities. These results contribute to further understanding of past nuclear events and resulting nuclear contamination in Russian Arctic terrestrial areas.

Legacy radionuclides in cryoconite and proglacial sediment on Orwell Glacier, Signy Island, Antarctica

Cryoconite is a specific type of material found on the surface of glaciers and icesheets. Samples of cryoconite were collected from the Orwell Glacier and its moraines, together with suspended sediment from the proglacial stream on Signy Island, part of the South Orkney Islands, Antarctica. The activity concentrations of certain fallout radionuclides were determined in the cryoconite, moraine and suspended sediment, in addition to particle size composition and %C and %N. For cryoconite samples (n = 5), mean activity concentrations (±1SD) of ¹³⁷Cs, ²¹⁰Pb_un and ²⁴¹Am were 13.2 ± 20.9, 66.1 ± 94.0 and 0.32 ± 0.64 Bq kg^-1, respectively. Equivalent values for the moraine samples (n = 7) were 2.56 ± 2.75, 14.78 ± 12.44 and <1.0 Bq kg^-1, respectively. For the composite suspended sediment sample, collected over 3 weeks in the ablation season, the values (± counting uncertainty) for ¹³⁷Cs, ²¹⁰Pb_un and ²⁴¹Am were 2.64 ± 0.88, 49.2 ± 11.9 and <1.0 Bq kg^-1, respectively. Thus, fallout radionuclide activity concentrations were elevated in cryoconite relative to moraine and suspended sediment. In the case of ⁴⁰K, the highest value was for the suspended sediment (1423 ± 166 Bq kg^-1). The fallout radionuclides in cryoconite were 1-2 orders of magnitude greater than values in soils collected from other locations in Antarctica. This work further demonstrates that cryoconite likely scavenges fallout radionuclides (dissolved and particulate) in glacial meltwater. In the case of ⁴⁰K, the greater value in suspended sediment implies a subglacial source. These results are amongst the relatively few that demonstrate the presence of fallout radionuclides in cryoconites at remote locations in the Southern Hemisphere. This work adds to the growing contention that elevated activities of fallout radionuclides, and other contaminants, in cryoconites are a global phenomenon and may be a risk to downstream terrestrial and aquatic ecosystems.

Impact of anthropogenic contamination on glacier surface biota

Glaciers are ecosystems and they host active biological communities. Despite their remoteness, glaciers act as cold condensers where high precipitation rates and cold temperatures favor the deposition of pollutants. These contaminants include a broad range of substances, including legacy pollutants, but also compounds still largely used. Some of these compounds are monitored in the environment and their effects on the ecosystems are known, in contrast others can be defined as emerging pollutants since their presence and their impact on the environment are still poorly understood (e.g. microplastics, radionuclides). This review aim to provide an overview of the studies that have investigated the effects of pollutants on the supraglacial ecosystem so far. Despite the distribution of the pollutants in glacier environments has been discussed in several studies, no review paper has summarized the current knowledge on the effects of these substances on the ecological communities living in glacier ecosystems.

Unveiling the extreme environmental radioactivity of cryoconite from a Norwegian glacier

This study is a first survey of the occurrence of artificial (¹³⁷Cs, ²⁴¹Am, ²⁰⁷Bi, Pu isotopes) and natural (²¹⁰Pb, ²²⁸Ac, ²¹⁴Bi, ⁴⁰K) radionuclides in Norwegian cryoconite. Cryoconite samples were collected before (12 samples) and after (5 samples) a rainfall event, after which 7 cryoconite holes dissapeared. The concentrations of radionuclides in cryoconite samples from the Blåisen Glacier are compared with data from the Arctic and Alpine glaciers. Cryoconite samples from the studied glacier had extremely high activity concentrations of ¹³⁷Cs, ²⁴¹Am, ²⁰⁷Bi and ^239+240Pu (up to 25,000 Bq/kg, 58 Bq/kg, 13 Bq/kg and 131 Bq/kg, respectively) and also high concentrations of organic matter (OM), comparing to other Scandinavian and Arctic glaciers, reaching up to ~40% of total mass. The outstandingly high concentrations of ¹³⁷Cs, ²⁴¹Am, Pu isotopes, and ²⁰⁷Bi on the Blåisen Glacier are primarily related to bioaccumulation of radionuclides in organic-rich cryoconite and might be enhanced by additional transfers of contamination from the tundra by lemmings during their population peaks. The presumed influence of intense rainfall on radionuclide concentrations in the cryoconite was not confirmed.

Cryoconite - From minerals and organic matter to bioengineered sediments on glacier's surfaces

Cryoconite is a mixture of mineral and organic material covering glacial ice, playing important roles in biogeochemical cycles and lowering the albedo of a glacier surface. Understanding the differences in structure of cryoconite across the globe can be important in recognizing past and future changes in supraglacial environments and ice-organisms-minerals interactions. Despite the worldwide distribution and over a century of studies, the basic characteristics of cryoconite, including its forms and geochemistry, remain poorly studied. The major purpose of our study is the presentation and description of morphological diversity, chemical and photoautotrophs composition, and organic matter content of cryoconite sampled from 33 polar and mountain glaciers around the globe. Observations revealed that cryoconite is represented by various morphologies including loose and granular forms. Granular cryoconite includes smooth, rounded, or irregularly shaped forms; with some having their surfaces covered by cyanobacteria filaments. The occurrence of granules increased with the organic matter content in cryoconite. Moreover, a major driver of cryoconite colouring was the concentration of organic matter and its interplay with minerals. The structure of cyanobacteria and algae communities in cryoconite differs between glaciers, but representatives of cyanobacteria families Pseudanabaenaceae and Phormidiaceae, and algae families Mesotaeniaceae and Ulotrichaceae were the most common. The most of detected cyanobacterial taxa are known to produce polymeric substances (EPS) that may cement granules. Organic matter content in cryoconite varied between glaciers, ranging from 1% to 38%. The geochemistry of all the investigated samples reflected local sediment sources, except of highly concentrated Pb and Hg in cryoconite collected from European glaciers near industrialized regions, corroborating cryoconite as element-specific collector and potential environmental indicator of anthropogenic activity. Our work supports a notion that cryoconite may be more than just simple sediment and instead exhibits complex structure with relevance for biodiversity and the functioning of glacial ecosystems.

Isotopic signatures of plutonium and uranium at Bikar atoll, northern Marshall Islands

We present plutonium (Pu) and uranium (U) isotopic fingerprints (or signatures) in environmental samples collected at Bikar Atoll. Bikar is the second -most northern atoll of the Republic of the Marshall Islands, and therefore an important reference point to evaluate the extension of the regional fallout from the Pacific Proving Grounds (PPG) in Bikini and Enewetak Atolls. Previous studies have shown that regional fallout from atmospheric nuclear weapon testing (NWT) in Bikini and Enewetak has resulted in elevated levels of fallout radionuclides in this atoll. In order to optimally interpret the isotopic fingerprints, we compare our results with data obtained in eleven certified reference materials, representing different contamination sources. As well as ²³⁸Pu, ²³⁹Pu, ²⁴⁰Pu, ²⁴¹Pu, ²³⁸U and ²³⁵U, this study also encompasses less commonly reported radionuclides such as ²⁴²Pu, ²⁴⁴Pu and ²³⁶U. We show the importance of combining numerous fingerprints for improved assessment of the source of a nuclear contamination. In samples from Bikar, Pu and U isotope ratios were found to vary within narrow ranges. Pu and U fingerprints suggest that regional fallout from the Castle Bravo test in March 1954 was the main source of the contamination. This was further confirmed by two different age dating approaches that estimated 1954 as the year of the contamination. We demonstrate that use of an exponential function to approximate the yield of heavy radionuclides in thermonuclear explosions with increasing mass is a valid approach for estimating the age of a contamination. We show that, if sufficient radionuclide activity concentration measurement results with low uncertainties are available, this method is robust.

Radioecological and geochemical peculiarities of cryoconite on Novaya Zemlya glaciers

In recent years, cryoconite has received growing attention from a radioecological point of view, since several studies have shown that this material is extremely efficient in accumulating natural and anthropogenic radionuclides. The Novaya Zemlya Archipelago (Russian Arctic) hosts the second largest glacial system in the Arctic. From 1957 to 1962, numerous atmospheric nuclear explosions were conducted at Novaya Zemlya, but to date, very little is known about the radioecology of its ice cap. Analysis of radionuclides and other chemical elements in cryoconite holes on Nalli Glacier reveals the presence of two main zones at different altitudes that present different radiological features. The first zone is 130-210 m above sea level (a.s.l.), has low radioactivity, high concentrations of lithophile elements and a chalcophile content close to that of upper continental crust clarkes. The second zone (220-370 m a.s.l.) is characterized by high activity levels of radionuclides and "inversion" of geochemical behaviour with lower concentrations of lithophiles and higher chalcophiles. In the upper part of this zone (350-370 m a.s.l.), ¹³⁷Cs activity reaches the record levels for Arctic cryoconite (5700-8100 Bq/kg). High levels of Sn, Sb, Bi and Ag, significantly exceeding those of upper continental crust clarkes, also appear here. We suggest that a buried layer of contaminated ice that formed during atmospheric nuclear tests serves as a local secondary source of radionuclide contamination. Its melting is responsible for the formation of this zone.

Sources, fate and distribution of inorganic contaminants in the Svalbard area, representative of a typical Arctic critical environment-a review

Global environmental changes not only contribute to the modification of global pollution transport pathways but can also alter contaminant fate within the Arctic. Recent reports underline the importance of secondary sources of pollution, e.g. melting glaciers, thawing permafrost or increased riverine run-off. This article reviews reports on the European Arctic-we concentrate on the Svalbard region-and environmental contamination by inorganic pollutants (heavy metals and artificial radionuclides), including their transport pathways, their fate in the Arctic environment and the concentrations of individual elements in the ecosystem. This review presents in detail the secondary contaminant sources and tries to identify knowledge gaps, as well as indicate needs for further research. Concentrations of heavy metals and radionuclides in Svalbard have been studied, in various environmental elements since the beginning of the twentieth century. In the last 5 years, the highest concentrations of Cd (13 mg kg^-1) and As (28 mg kg^-1) were recorded for organic-rich soils, while levels of Pb (99 mg kg^-1), Hg (1 mg kg^-1), Zn (496 mg kg^-1) and Cu (688 mg kg^-1) were recorded for marine sediments. Increased heavy metal concentrations were also recorded in some flora and fauna species. For radionuclides in the last 5 years, the highest concentrations of ¹³⁷Cs (4500 Bq kg^-1), ²³⁸Pu (2 Bq kg^-1) and ^{239 + 240}Pu (43 Bq kg^-1) were recorded for cryoconites, and the highest concentration of ²⁴¹Am (570 Bq kg^-1) was recorded in surface sediments. However, no contamination of flora and fauna with radionuclides was observed.

A High-Arctic flow-through lake system hydrochemical changes: Revvatnet, southwestern Svalbard (years 2010-2018)

Lake ecosystems are strongly coupled to features of their surrounding landscapes such as geomorphology, lithology, vegetation and hydrological characteristics. In the 2010-2018 summer seasons, we investigated an Arctic flow-through lake system Revvatnet, located in the vicinity of the coastal zone of Hornsund fjord in Svalbard, characterising its hydrological properties and the chemical composition of its waters. The lake system comprises of a small upper lake and a large lower one, the latter cone-shaped, with -29.1 m maximum depth. With near-neutral pH (full range 6.5-8.4) and low EC (7-147 μS cm-1), the lake has rather similar characteristics to many Arctic lakes. Metal and metalloid concentrations were either similar across the lake system or increased downstream (except Zn, which has important ore-bearing veins in the upper part of the catchment), which is consistent with the likely slow dissolution of suspended particles within the lakes. The ∑PAHs concentrations ranged from <MDL to 2151 ng L-1, and according to the indicator PAHs concentration ratios, they originated from a mixture of combustion processes (they were not petrogenic). Principal component analysis showed that seasonal variability was the most characteristic feature of the chemical composition of these waters, although there appear to be consistent changes with time (sampling year) as well. Future research should explore the occurrence of high maxima in the concentrations of priority pollutants, such as PAHs, metals and metalloids (e.g. As).

Bacterial diversity and their metabolic profiles in the sedimentary environments of Ny-Ålesund, Arctic

Sedimentary environments in the Arctic are known to harbor diverse microbial communities playing a crucial role in the remineralization of organic matter and associated biogeochemical cycles. In this study, we used a combination of culture-dependent and culture-independent approaches to understanding the bacterial community composition associated with the sediments of a terrestrial versus fjord system in the Svalbard Arctic. Community-level metabolic profiling and growth response of retrieved bacterial isolates towards different carbon substrates at varying temperatures were also studied to assess the metabolic response of communities and isolates in the system. Bacterial species belonging to Cryobacterium and Psychrobacter dominated the terrestrial and fjord sediment retrievable fraction. Amplicon sequencing analysis revealed higher bacterial diversity in the terrestrial sediments (Shannon index; 8.135 and 7.935) as compared to the fjord sediments (4.5-5.37). Phylum Proteobacteria and Bacteroidetes dominated both terrestrial and fjord sediments. Phylum Verrucomicrobia and Cyanobacteria were abundant in terrestrial sediments while Epsilonbacteraeota and Fusobacteriia dominated the fjord sediments. Significant differences were observed in the carbon substrate utilization profiles between the terrestrial and fjord sediments at both 4 °C and 20 °C incubations (p < 0.005). Utilization of N-acetyl-D-glucosamine, D-mannitol and Tween-80 by the sediment communities and bacterial isolates from both systems, irrespective of their temperature incubations implies the affinity of bacteria for such substrates as energy sources and for their survival in cold environments. Our results suggest the ability of sediment bacterial communities to adjust their substrate utilization profiles according to condition changes in the ecosystems and are found to be less influenced by their phylogenetic relatedness.

The effects of urban vehicle traffic on heavy metal contamination in road sweeping waste and bottom sediments of retention tanks

Diffuse pollution formed during a surface runoff on paved surfaces is a source of heavy metals (HMs) of various origin. This research study indicates the connection between bottom sediments of retention tanks located on urban streams and road sweeping wastes (RSW) that migrate during surface runoff to the stormwater drainage systems with discharge to the retention tanks. Moreover, we test the primary sources of HMs in RSW by analysing the mechanical wastes (MW) produced by vehicles in order to track the relationship between car parts and HMs deposited in the retention tanks receiving the surface runoff from streets. To identify the origin of HMs diverse source tracking approaches were used: statistical methods, Pb isotope ratios, and the flag element ratio approach. MW presented a very high HMs content (max observed values in mg/kg d.w.: 10477-Zn, 3512-Cu, 412-Pb, 3.35-Cd, 226-Ni, and 633-Cr), while for RSW the HMs content was similar to the bottom sediments. The total carcinogenic risk raises concerns due to the Cr content. The source of Zn was tyre wear and traffic. Ni, Cr, Fe, and Cd were correlated to Zn and shared a common/similar origin. PCA suggested that Cu features quasi-independent behaviour. The Pb isotopic ratios of RSW indicated Pb enrichment originating from coal combustion, while the gasoline and diesel source of Pb was excluded. The Pb isotopic ratios characteristic for MW were in within the following ranges: 1.152-1.165 (²⁰⁶Pb/²⁰⁷Pb), 2.050-2.085 (²⁰⁸Pb/²⁰⁶Pb), and 2.350-2.418 (²⁰⁸Pb/²⁰⁷Pb). The complex analysis of HMs origin confirmed the motorization origin of HMs: Zn, Cr, Ni, and Cd, except Pb (coal combustion as the main source) and Cu (non-uniform origin). The results of various source tracking methods were coherent, but Pb isotope ratios alone brought important information allowing to link Pb in sediments to the atmospheric deposition of coal combustion products.

90Sr level and behaviour in the terrestrial environment of Spitsbergen

The research was focused on the level and distribution of 90Sr in various parts of the terrestrial environment of Spitsbergen. The mean activity concentrations were noted lower in peats and soils than in cryoconite. Analysis of vertical variation of 90Sr for soils and peats as well as isotopic ratios of 137Cs/90Sr and 239+240Pu/90Sr for cryoconite clearly showed substantial migration or depletion of the considered radionuclide. Due to the large dispersion of isotopic signatures, the 90Sr provenance was difficult to identify in the examined region. However, observed high mobility of the 90Sr might indicate the global fallout origin.

Black Carbon as a Source of Trace Elements and Nutrients in Ice Sheet of King George Island, Antarctica

Enormous deglaciation in the polar and mountainous regions of the Earth is associated not only with large-scale climatic changes but also with the global transfer of black carbon (BC) microparticles, which accumulate on the surface of glaciers and lead to changes in albedo and the rate of degradation of ice. BC is the product of an incomplete combustion of fossil fuels, volcanic eruptions, and wildfires. The accumulation of organogenic microparticles leads to the formation of cryoconites, which are dust made of a combination of small rock particles and the result of anthropogenic activities (fossil fuel combustion) that play a special role in deglaciation. Here, we describe the content of trace metals and nutrients in accumulation of the BC from glaciers of Fildes Peninsula, King George Island, Western Antarctica. The analysis of trace metals concentrations showed that most of the studied elements (Cr, Pb, Zn, Ni) have a volcanic origin; at the same time, Cd and Cu have been accumulated as a result of anthropogenic activity. The content of nutrients in BC are most similar with Technosols, which forms near the scientific station at King George Island. The particles of BC can be translocated into organisms, which could pose a significant risk for living organisms and humans.

Biotope and biocenosis of cryoconite hole ecosystems on Ecology Glacier in the maritime Antarctic

Despite recent great interest in glacier ecosystems in the continental Antarctic, little is known about their maritime counterparts. Our study presents descriptive data on cryoconite sediments and cryoconite holes on Ecology Glacier (King George Island) to accomplish three main objectives: (a) to identify main eukaryotic (algae, invertebrates) and prokaryotic (cyanobacteria) components of microbial communities; (b) to provide a "baseline" of community composition, organic matter and artificial contamination; and (c) to identify key abiotic factors that might be important in community assembly. Cryoconite holes were sampled along an altitudinal gradient of Ecology Glacier in January, mid Austral Summer 2017. Cryoconite holes located in lower altitude were deeper than those located in the middle and the highest altitude. Seventeen species of algae and cyanobacteria with biomass of 0.79 to 5.37 μg/cm³ have been found in sediments. Dominant species were cyanobacterial Pseudanabaena frigida and Bacillariophyceae Microcostaus sp. Biomass of Bacillariophyceae was significantly higher than that of Chlorophyta and Cyanobacteria. We found three species of rotifers (potentially two new to science) and for the first time a glacier dwelling Acari (suspension feeder, Nanorchestes nivalis). Organic matter content ranged from 5.4% to 7.6%. Investigated artificial radionuclides included ¹³⁷Cs, ²³⁸Pu, ^239+240Pu and ²⁴¹Am. ²¹⁰Pb seems to be related to organic matter content. Overall, cryoconite holes on Ecology Glacier present unique habitats that serve as biodiversity hotspots of psychrophiles, source of organic matter, matrices for radioactivity tracking and model for observing changes in supraglacial ecosystems in the maritime Antarctic.

Occurrence of integrons and antibiotic resistance genes in cryoconite and ice of Svalbard, Greenland, and the Caucasus glaciers

The prevalence of integrons and antibiotic resistance genes (ARGs) is a serious threat for public health in the new millennium. Although commonly detected in sites affected by strong anthropogenic pressure, in remote areas their occurrence, dissemination, and transfer to other ecosystems is poorly recognized. Remote sites are considered as a benchmark for human-induced contamination on Earth. For years glaciers were considered pristine, now they are regarded as reservoirs of contaminants, thus studies on contamination of glaciers, which may be released to other ecosystems, are highly needed. Therefore, in this study we evaluated the occurrence and frequency of clinically relevant ARGs and resistance integrons in the genomes of culturable bacteria and class 1 integron-integrase gene copy number in the metagenome of cryoconite, ice and supraglacial gravel collected on two Arctic (South-West Greenland and Svalbard) and two High Mountain (the Caucasus) glaciers. Altogether, 36 strains with intI1 integron-integrase gene were isolated. Presence of class 1 integron-integrase gene was also recorded in metagenomic DNA from all sampling localities. The mean values of relative abundance of intI1 gene varied among samples and ranged from 0.7% in cryoconite from Adishi Glacier (the Caucasus) to 16.3% in cryoconite from Greenland. Moreover, antibiotic-resistant strains were isolated from all regions. Genes conferring resistance to β-lactams (bla_SHV, bla_TEM, bla_OXA, bla_CMY), fluoroquinolones (qepA, qnrC), and chloramphenicol (cat, cmr) were detected in the genomes of bacterial isolates.

Heavy Metals in a High Arctic Fiord and Their Introduction with the Wastewater: A Case Study of Adventfjorden-Longyearbyen System, Svalbard

Longyearbyen is the largest settlement on Svalbard archipelago, with 2400 permanent residents and approximately 150,000 tourists visiting every year. The city annually releases approximately 285,000 m3 of untreated wastewater to the nearby Adventfjorden. To date, the environmental impact of this continuous input has been studied mainly regarding the sediments and benthic fauna in the fiord. Here, we present results from a study of raw wastewater entering Adventfjorden as well as heavy metals concentrations in the water column within the fjord itself. Two surveys were carried out in summer and autumn season 2018, to establish physical and chemical properties of water at various locations. Trace elements (V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Hg, As, Cd, Pb, U), total suspended solids (TSS) and total organic carbon (TOC) were measured. Our results show that Longyearbyen’s raw wastewater introduces low concentrations of heavy metals to the fiord, but due to the growing number of inhabitants and tourists, it should be monitored to avoid degradation of Adventfjorden ecosystem

Sources and variation of isotopic ratio of airborne radionuclides in Western Arctic lichens and mosses

This research concerned radioactivity of lichens and mosses from coastal zones of the Canadian Arctic and Alaska. Over 50 samples were collected from 7 positions during two scientific expeditions in 2012 and 2013. The tundra contamination caused by anthropogenic radionuclides was relatively low, reaching mean values with SD's of: 17.4 ± 3.5 Bq/kg for ⁹⁰Sr, 14.0 ± 2.9 Bq/kg for ¹³⁴Cs, 38.4 ± 7.5 Bq/kg for ¹³⁷Cs, 0.86 ± 0.24 Bq/kg for ^239+240Pu, 0.065 ± 0.017 Bq/kg for ²³⁸Pu and 0.50 ± 0.13 Bq/kg for ²⁴¹Am. The increase of activity concentration with increasing latitudes was noticed mostly in regard to ⁹⁰Sr, Pu isotopes and ²⁴¹Am. The analysis of isotopic ratios exhibited dominant contribution of the global fallout (+SNAP 9A satellite re-entry fallout) for the presence of plutonium isotopes and ²⁴¹Am. The Fukushima fallout signature was identified in a few lichens from Alaska. However, the influence of additional unknown factor on the occurrence of ⁹⁰Sr and ¹³⁷Cs has been detected in western part of Canadian Arctic. Natural radioisotopes of thorium and uranium were found throughout the entire investigated region and the average values of activity concentration with SD's were as follows: 2.92 ± 0.47 Bq/kg for ²³⁰Th, 2.61 ± 0.48 Bq/kg for ²³²Th, 4.32 ± 0.80 Bq/kg for ²³⁴U and 3.97 ± 0.71 Bq/kg for ²³⁸U. Examined Western Arctic tundra was not affected with any technically enhanced natural radioactivity.

First evidence of microplastic contamination in the supraglacial debris of an alpine glacier

Contamination by plastic debris has been documented in most regions of the world, but their occurrence in high mountain areas has not been investigated to date. Here we present the first report of the occurrence and amount of microplastic in any terrestrial glacier environment. In the supraglacial debris of the Forni Glacier (Italian Alps), we observed the occurrence of (mean ± standard error) 74.4 ± 28.3 items kg^-1 of sediment (dry weight). This amount is within the range of variability of microplastic contamination observed in marine and coastal sediments in Europe. Most plastic items were made by polyesters, followed by polyamide, polyethylene and polypropylene. We estimated that the whole ablation area of Forni Glacier should host 131-162 million plastic items. Microplastic can be released directly into high elevation areas by human activities in the mountain or be transported by wind to high altitude. The occurrence of microplastic on Forni Glacier may be due to the gathering of debris coming from the large accumulation area into the relatively smaller ablation area of the glacier, as a consequence of its flow and melting.

Extreme levels of fallout radionuclides and other contaminants in glacial sediment (cryoconite) and implications for downstream aquatic ecosystems

Glaciers in most parts of the world are retreating, releasing water and sediments to downstream rivers. Studies have found elevated levels of fallout radionuclides (FRNs) and other contaminants in glacial sediments, especially cryoconite, in European glaciers and Greenland. However, there are no equivalent studies for glaciers in North America. We report concentrations of FRNs (i.e. ¹³⁷Cs, ²¹⁰Pb_un and ²⁴¹Am) and other contaminants (i.e. metal(loids), phosphorus) in cryoconite and proglacial sediments from a glacier in British Columbia, Canada, and compare values to suspended sediments from the downstream river. The mean concentrations of ¹³⁷Cs, ²¹⁰Pb_un and ²⁴¹Am in cryoconite were 2,123 ± 74, 7,535 ± 224 and 11.5 ± 3.0 Bq kg⁻¹, respectively, which are an order of magnitude greater than those for most soils and surficial materials. FRNs were much lower in suspended sediments and decreased with distance away from the glacier. Geochemical elements were enriched in cryoconite relative to local clastic materials and upper continental crust. Concentrations of FRNs in cryoconite were correlated with organic matter, which suggests this is important in controlling the scavenging of hydrophobic contaminants in glacial meltwater. Low concentrations of FRNs and contaminants in suspended sediments suggest that glacial meltwater and the delivery of cryoconite have limited impact on downstream aquatic ecosystems.

Accumulation of Atmospheric Mercury in Glacier Cryoconite over Western China

Cryoconite is a granular aggregate, comprised of both mineral and biological material, and known to accumulate atmospheric contaminants. In this study, cryoconite was sampled from seven high-elevation glaciers in Western China to investigate the spatial and altitudinal patterns of atmospheric mercury (Hg) accumulation in the cryoconite. The results show that total Hg (Hg_T) concentrations in cryoconite were significant with relatively higher Hg accumulation in the southern glaciers (66.0 ± 29.3 ng g^-1), monsoon-influenced regions, than those in the northern glaciers (42.5 ± 20.7 ng g^-1), westerlies-influenced regions. The altitudinal profile indicates that Hg_T concentrations in the northern glaciers decrease significantly with altitude, while those in the southern glaciers generally increase toward higher elevations. Unexpectedly high accumulation of methyl-Hg (MeHg) with an average of 1.0 ± 0.4 ng g^-1 was also detected in the cryoconite samples, revealing the surface of cryoconite could act as a potential site for Hg methylation in alpine environments. Our preliminary estimate suggests a storage of ∼34.3 ± 17.4 and 0.65 ± 0.28 kg of Hg_T and MeHg from a single year of formation process in the glacier cryoconite. Therefore, glacier cryoconite could play an important role in Hg storage and transformation, which may result in downstream effects on glacier-fed ecosystems under climate warming scenario.

Post-Depositional Biodegradation Processes of Pollutants on Glacier Surfaces

Glaciers are important fresh-water reservoirs for our planet. Although they are often located at high elevations or in remote areas, glacial ecosystems are not pristine, as many pollutants can undergo long-range atmospheric transport and be deposited on glacier surface, where they can be stored for long periods of time, and then be released into the down-valley ecosystems. Understanding the dynamics of these pollutants in glaciers is therefore important for assessing their environmental fate. To this aim, it is important to study cryoconite holes, small ponds filled with water and with a layer of sediment, the cryoconite, at the bottom, which occur on the surface of most glaciers. Indeed, these environments are hotspots of biodiversity on glacier surface as they host metabolically active bacterial communities that include generalist taxa able to degrade pollutants. In this work, we aim to review the studies that have already investigated pollutant (e.g., chlorpyrifos and polychlorinated-biphenyls (PCBs)) degradation in cryoconite holes and other supraglacial environmental matrices. These studies have revealed that bacteria play a significant role in pollutant degradation in these habitats and can be positively selected in contaminated environments. We will also provide indication for future research in this field.

The sources of high airborne radioactivity in cryoconite holes from the Caucasus (Georgia)

Cryoconite granules are mixtures of mineral particles, organic substances and organisms on the surface of glaciers where they decrease the ice albedo and are responsible for formation of water-filled holes. The contaminants are effectively trapped in the cryoconite granules and stay there for many years. This study evaluates the contamination level of artificial and natural radionuclides in cryoconite holes from Adishi glacier (Georgia) and identifies the sources of contamination based on activity or mass ratios among artificial radionuclides. Results revealed high activity concentrations of fallout radionuclides reaching 4900 Bq/kg, 2.5 Bq/kg, 107 Bq/kg and 68 Bq/kg for ¹³⁷Cs, ²³⁸Pu, ^239+240Pu and ²⁴¹Am, respectively. The main source of Pu is global fallout, but the low ²⁴⁰Pu/²³⁹Pu atomic ratios also indicated local tropospheric source of ²³⁹Pu, probably from the Kapustin Yar nuclear test site. Also, high activity ratios of ²⁴¹Am/^239+240Pu could originate from Kapustin Yar. The natural radionuclides originate from the surrounding rocks and were measured to control the environmental processes. ²¹⁰Pb in cryoconite granules comes predominantly from the atmospheric deposition, and its activity concentrations reach high values up to 12000 Bq/kg.

Plasmids of Psychrotolerant Polaromonas spp. Isolated From Arctic and Antarctic Glaciers - Diversity and Role in Adaptation to Polar Environments

Cold-active bacteria of the genus Polaromonas (class Betaproteobacteria) are important components of glacial microbiomes. In this study, extrachromosomal replicons of 26 psychrotolerant Polaromonas strains, isolated from Arctic and Antarctic glaciers, were identified, sequenced, and characterized. The plasmidome of these strains consists of 13 replicons, ranging in size from 3,378 to 101,077 bp. In silico sequence analyses identified the conserved backbones of these plasmids, composed of genes required for plasmid replication, stable maintenance, and conjugal transfer. Host range analysis revealed that all of the identified plasmids are narrow-host-range replicons, only able to replicate in bacteria of closely related genera (Polaromonas and Variovorax) of the Comamonadaceae family. Special attention was paid to the identification of plasmid auxiliary genetic information, which may contribute to the adaptation of bacteria to environmental conditions occurring in glaciers. Detailed analysis revealed the presence of genes encoding proteins potentially involved in (i) protection against reactive oxygen species, ultraviolet radiation, and low temperatures; (ii) transport and metabolism of organic compounds; (iii) transport of metal ions; and (iv) resistance to heavy metals. Some of the plasmids also carry genes required for the molecular assembly of iron-sulfur [Fe-S] clusters. Functional analysis of the predicted heavy metal resistance determinants demonstrated that their activity varies, depending on the host strain. This study provides the first molecular insight into the mobile DNA of Polaromonas spp. inhabiting polar glaciers. It has generated valuable data on the structure and properties of a pool of plasmids and highlighted their role in the biology of psychrotolerant Polaromonas strains and their adaptation to the environmental conditions of Arctic and Antarctic glaciers.

Trace elements in Polytrichum commune and Polytrichastrum formosum from the Karkonosze Mountains (SW Poland)

The Karkonosze National Park, an unique mountainous biosphere reserve, is influenced by long-distance anthropogenic atmospheric transport of among others trace elements and additionally by local tourist centres, which may be supplementary sources of pollution. Discharged trace elements are non-degradable, and their level must be precisely monitored. Therefore, the concentrations of As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Mo, Ni, Pb, Rb and Zn in Polytrichum commune and Polytrichastrum formosum collected from the Karkonosze sites influenced only by long-range pollution and from sites in the vicinity of local tourist centres were established. P. commune and P. formosum revealed the ability to accumulate higher concentrations of trace elements while growing in locally contaminated sites in comparison with sites free from such pollution. Therefore, both species may be utilised for bioindication in the Karkonosze National Park. Elevated levels of trace elements in both species (except for Hg) in comparison with concentrations typical for mosses from unpolluted sites point to the existence of pollution of this area. P. commune was a better bioindicator of Cd, Co, Cr, Cu, Mo, Ni, Pb and Rb than P. formosum, probably because of the larger gametophytes and its morphology, which appears prone to an increased uptake of trace elements from the atmosphere.

Metals in Racomitrium lanuginosum from Arctic (SW Spitsbergen, Svalbard archipelago) and alpine (Karkonosze, SW Poland) tundra

Arctic-alpine tundra habitats are very vulnerable to the input of relatively small amounts of xenobiotics, and thus their level in such areas must be carefully controlled. Therefore, we collected the terrestrial widespread moss Racomitrium lanuginosum (Hedw.) Brid. in Spitsbergen in the Arctic moss lichen tundra and, for comparison, in the Arctic-alpine tundra in the Karkonosze (SW Poland). Concentrations of the elements Cd, Co, Cr, Cu, Fe, Hg, Li, Mn, Mo, Na, Ni, Pb, V, and Zn in this species and in the parent rock material were measured. We tested the following hypothesis: R. lanuginosum from Spitsbergen contains lower metal levels than the species from the Karkonosze collected at altitudes influenced by long-range transport from former Black Triangle industry. Principal component and classification analysis (PCCA) ordination revealed that mosses of Spitsbergen were distinguished by a significantly higher Na concentration of marine spray origin and mosses of Karkonosze were distinguished by significantly higher concentrations of Cd, Cr, Cu, Fe, Hg, Li, Mn, Pb, V, and Zn probably from long-range atmospheric transport. The influence of the polar station with a waste incinerator resulted in significantly higher Co, Li, and Ni concentrations in neighbouring mosses in comparison with this species from other sites. This investigation contributes to the use of R. lanuginosum as a bioindicator for metal contamination in Arctic and alpine tundra regions characterised by severe climate habitats with a restricted number of species. This moss enables the control of pollution usually brought solely by long-range atmospheric transport in high mountains as well as in Arctic areas.

Sources of 137Cs to an Arctic fjord (Hornsund, Svalbard)

Although primary sources of anthropogenic ¹³⁷Cs have decreased nowadays, the Arctic is exposed to a variety of secondary sources. These include riverine run-off, oceanic currents, drifting sea ice, melting glaciers and permafrost. Recent reports underline the role of glaciers, specifically cryoconite holes, in radionuclide accumulation. Therefore, this study investigates the hypothesis that melting glaciers are an important means of delivering ¹³⁷Cs for Arctic fjord (Hornsund, Svalbard). As marine sediments are the final sink for most contaminants, seven 30-40 cm long sediment cores collected in 2016 were investigated for ¹³⁷Cs activity concentration. Five were collected in a transect from the central to the outer part of the fjord while two were collected within one km of the different melting tidewater glaciers. Sediment layers were dated using ²¹⁰Pb to reveal the history of ¹³⁷Cs accumulation. The measured ¹³⁷Cs activity concentrations ranged from <0.1 to 7.7 Bq kg^-1. The activity concentrations ranging from 0.3 to 3.1 Bq kg^-1 were measured in surface (0-2 cm) sediments. The total ¹³⁷Cs inventories were calculated for five station and ranged from 322 to 908 Bq m^-2, of which 29-34 Bq m^-2 were deposited within the last decade. At two stations characterized by largest sediment accumulation rates only the last decade inventories were calculated and they ranged from 13 to 444 Bq·m^-2. The mean of ¹³⁷Cs fluxes calculated for last decade ranged from 2.7 to 44.1 Bq m^-2yr^-1. The history of ¹³⁷Cs environmental inputs was well revealed in the sediments as the ¹³⁷Cs penetration depth agreed with the time of its introduction to the Arctic and the most pronounced ¹³⁷Cs activity concentration peak was found in sediments dated for circa 1963. Although ¹³⁷Cs fluxes and inventories were largest in the glacial bay (Brepollen), the ¹³⁷Cs was diluted in a large amount of sedimenting material. Based on the results in this study, the glaciers do not appear to act as important sources of ¹³⁷Cs to the marine environment in the Hornsund fjord.

History of heavy metal accumulation in the Svalbard area: Distribution, origin and transport pathways

In this study temporal changes of Pb, Zn, Cd and Cu concentrations were studied in 19 dated sediment cores collected from Svalbard fjords and the Barents Sea. The main aim was to study spatial and historical variations in heavy metal concentrations, deposition rates and sources in the context of different metal transport pathways. Metal concentrations ranged from 5.7 to 45.8 mg kg^-1 for Pb, from 13.4 to 54.5 mg kg^-1 for Cu, from 0.01 to 0.90 mg kg^-1 for Cd and from 55.6 to 130.4 mg kg^-1 for Zn. Some fjords were unpolluted by heavy metals while in others a clear signal of metal enrichment was found (outer Kongsfjorden, Hornsund, Adventfjorden). Large-scale processes such as atmospheric and oceanic transport were found to be important drivers of heavy metal contaminant distribution. The significance of global drivers varied among the fjords, due to coupling with local processes. Outer fjord parts, the most impacted by oceanic transport, were characterized by the excess ²⁰⁶Pb/²⁰⁷Pb values of ∼1.17, while the inner basins were characterized by the excess ²⁰⁶Pb/²⁰⁷Pb of ∼1.14 suggesting possible different importance of Pb sources (marine currents and atmospheric transport).

Concentrations of polycyclic aromatic hydrocarbons and trace elements in Arctic soils: A case-study in Svalbard

A combined assessment on the levels and distribution profiles of polycyclic aromatic hydrocarbons (PAHs) and trace elements in soils from Pyramiden (Central Spitsbergen, Svalbard Archipelago) is here reported. As previously stated, long-range atmospheric transport, coal deposits and previous mining extractions, as well as the stack emissions of two operative power plants at this settlement are considered as potential sources of pollution. Eight top-layer soil samples were collected and analysed for the 16 US EPA priority PAHs and for 15 trace elements (As, Be, Cd, Co, Cr, Cu, Hg, Mn, Mo, Ni, Pb, Sn, Tl, V and Zn) during late summer of 2014. The highest levels of PAHs and trace elements were found in sampling sites located near two power plants, and at downwind from these sites. The current PAH concentrations were even higher than typical threshold values. The determination of the pyrogenic molecular diagnostic ratios (MDRs) in most samples revealed that fossil fuel burning might be heavily contributing to the PAHs levels. Two different indices, the Pollution Load Index (PLI) and the Geoaccumulation Index (Igeo), were determined for assessing soil samples with respect to trace elements pollution. Samples collected close to the power plants were found to be slightly and moderately polluted with zinc (Zn) and mercury (Hg), respectively. The Spearman correlation showed significant correlations between the concentrations of 16 PAHs and some trace elements (Pb, V, Hg, Cu, Zn, Sn, Be) with the organic matter content, indicating that soil properties play a key role for pollutant retention in the Arctic soils. Furthermore, the correlations between ∑16 PAHs and some trace elements (e.g., Hg, Pb, Zn and Cu) suggest that the main source of contamination is probably pyrogenic, although the biogenic and petrogenic origin of PAHs should not be disregarded according to the local geology.

Airborne radionuclides in the proglacial environment as indicators of sources and transfers of soil material

A survey of artificial (¹³⁷Cs, ²³⁸Pu, ^239+240Pu, ²⁴¹Am) and natural (²²⁶Ra, ²³²Th, ⁴⁰K, ²¹⁰Pb) radioactive isotopes in proglacial soils of an Arctic glacier have revealed high spatial variability of activity concentrations and inventories of the airborne radionuclides. Soil column ¹³⁷Cs inventories range from below the detection limit to nearly 120 kBq m^-2, this value significantly exceeding direct atmospheric deposition. This variability may result from the mixing of materials characterised by different contents of airborne radionuclides. The highest activity concentrations observed in the proglacial soils may result from the deposition of cryoconites, which have been shown to accumulate airborne radionuclides on the surface of glaciers. The role of cryoconites in radionuclide accumulation is supported by the concordant enrichment of the naturally occurring airborne ²¹⁰Pb in proglacial soil cores showing elevated levels of artificial radionuclides. The lithogenic radionuclides show less variability than the airborne radionuclides because their activity concentrations are controlled only by the mixing of material derived from the weathering of different parent rocks. Soil properties vary little within and between the profiles and there is no unequivocal relationship between them and the radionuclide contents. The inventories reflect the pathways and time variable inputs of soil material to particular sites of the proglacial zone. Lack of the airborne radionuclides reflects no deposition of material exposed to the atmosphere after the 1950s or its removal by erosion. Inventories above the direct atmospheric deposition indicate secondary deposition of radionuclide-bearing material. Very high inventories indicate sites where transport pathways of cryoconite material terminated.

Bacteria contribute to pesticide degradation in cryoconite holes in an Alpine glacier

Organic contaminants deposited on glacier snow and ice are subject to partitioning and degradation processes that determine their environmental fate and, consequently, their accumulation in ice bodies. Among these processes, organic compound degradation by supraglacial bacteria has been investigated to a lesser extent than photo- and chemical degradation. We investigated biodegradation of the organophosphorus insecticide chlorpyrifos (CPF), a xenobiotic tracer that accumulates on glaciers after atmospheric medium- and long-range transport, by installing in situ microcosms on an Alpine glacier to simulate cryoconite hole systems. We found that biodegradation contributed to the removal of CPF from the glacier surface more than photo- and chemical degradation. The high concentration of CPF (2-3 μg g^-1 w.w.) detected in cryoconite holes and the estimated half-life of this compound (35-69 days in glacier environment) indicated that biodegradation can significantly reduce CPF concentrations on glaciers and its runoff to downstream ecosystems. The metabolic versatility of cryoconite bacteria suggests that these habitats might contribute to the degradation of a wide class of pollutants. We therefore propose that cryoconite acts as a "biofilter" by accumulating both pollutants and biodegradative microbial communities. The contribution of cryoconite to the removal of organic pollutants should be included in models predicting the environmental fate of these compounds in cold areas.

Cryoconite as a temporary sink for anthropogenic species stored in glaciers

Cryoconite, the typical sediment found on the surface of glaciers, is mainly known in relation to its role in glacial microbiology and in altering the glacier albedo. But if these aspects are relatively well addressed, the same cannot be said about the geochemical properties of cryoconite and the possible interactions with glacial and peri-glacial environment. Current glacier retreat is responsible for the secondary emission of species deposited in high-altitude regions in the last decades. The role played by cryoconite in relation to such novel geochemical fluxes is largely unknown. Few and scarce observations suggest that it could interact with these processes, accumulating specific substances, but why, how and to what extent remain open questions. Through a multi-disciplinary approach we tried to shed lights. Results reveal that the peculiar composition of cryoconite is responsible for an extreme accumulation capability of this sediment, in particular for some, specific, anthropogenic substances.

Concentrations and origin of polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) in sediments of western Spitsbergen fjords (Kongsfjorden, Hornsund, and Adventfjorden)

Contaminant profiles in sediment cores represent valuable natural archives of environmental contamination, by which contaminant sources and historical changes in contaminant input and cycling may be recognized. In the present study, we discuss the sedimentary profiles and historical trends of organic contaminants - polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) - in three fjords of the Svalbard archipelago differing in environmental conditions and anthropogenic impact. The obtained results revealed no significant differences between the fjords Hornsund and Kongsfjorden, in the average levels of the analyzed contaminants. Levels ranging from 0.05 to 1.47 ng/g d.w. for ∑7 PCBs and from 37.3 to 1973 ng/g d.w. for ∑12 PAHs were measured. The observed spatial and temporal differences in contaminant levels are rather related to local variations in the fjords associated with the location of sampling stations. Higher concentrations of the ∑7 PCBs exceeding 1.00 ng/g d.w. were measured in sediment cores collected in the inner parts of both fjords, which remain under the influence of melting glacier outflows. Important concentrations of these contaminants were noticed in layers deposited recently, suggesting intensive supply of these substances from secondary sources. The observed levels are generally low and well below known established no effect levels. Only the concentration of fluoranthene exceeded the threshold effect level at several sampling stations. Moreover, fluoranthene concentrations in almost all Adventfjorden sediment layer samples were above probable effect levels, which can indicate a risk of adverse effects in exposed benthic organisms. The fluoranthene/pyrene and phenthrene/anthracene ratios, which are used for identification of hydrocarbon sources, suggest a dominance of PAHs of pyrolytic genesis in Kongsfjorden and Hornsund. In Adventfjorden, hydrocarbons of petrogenic origin were predominant. However, other sources like coal dust from stores on land are also possible at this location.