Reliable Ultra Trace Analysis of Cd, U and Zn Concentrations in Greenland Snow and Ice by Using Ultraclean Methods for Contamination Control

This study presents ultraclean procedures used in the challenging task of determining trace elements at or below the pg/g concentration level encountered in Greenland snow and ice. In order to validate these ultraclean procedures, recent snowfall and Holocene ice from northwest Greenland were analyzed for Cd, U, and Zn concentrations. The total procedural blanks brought through the entire measurement procedure proved to be negligible, compared to trace element concentrations, measured in snow and ice samples. This validates the overall practicality of the proposed ultraclean procedures, thereby ensuring the reliable measurements of ultra-trace analysis. A comparison between our study and published data shows that improper procedures employed throughout all stages, from field sampling to analysis to elevate the concentrations by several orders of magnitude, relative to the reliable concentration ranges. The risk of contamination exposure for selected trace elements appears to increase in the order of U < As ≤ Pb < Cd < Zn. Reliable measurements of Cd, U, and Zn concentrations in snow and ice allowed us to interpret the data in terms of seasonal variations in the inputs of crustal and anthropogenic sources to Greenland ice sheet.

Source, contribution and microbial N-cycle of N-compounds in China fresh snow

The importance and contribution of nitrogen compounds and the related microbial nitrogen cycling processes in fresh snow are not well understood under the current research background. We collected fresh snow samples from 21 cities that 80% are from China during 2016 and 2017. Principal component analysis showed that SO₄^2- were in the first principal component, and N-compounds were the second. Furthermore, the main pollutant ions SO₄^2- and NO₃^- were from anthropogenic sources, and SO₄^2- contributed (61%) more to the pollution load than NO₃^- (29%), which were confirmed through a series of precipitation mechanism analysis. We selected five N-cycle processes (consist of oxidation and reduction processes) for molecular biology experiments, including Ammonia-oxidation process, Nitrite-oxidation process, Denitrification process, Anaerobic-ammoxidation process (Anammox) and Dissimilatory nitrate reduction to ammonium process (DNRA). Except ammonia-oxidizing archaeal (AOA) and bacterial (AOB) amoA genes (above 10⁷ copies g^-1), molecular assays of key functional genes in various nitrogen conversion processes showed a belowed detection limit number, and AOB abundance was always higher than AOA. The determination of the microbial transformation rate using the ¹⁵N-isotope tracer technique showed that the potential rate of five N-conversion processes was very low, which is basically consistent with the results from molecular biology studies. Taken together, our results illustrated that microbial nitrogen cycle processes are not the primary biological processes causing the pollution in China fresh snow.

Assessing the ecophysiological response of a mountain grassland community to ski slope management through isotopic composition

A scarce natural snow cover forces an increasing use of artificial snow on ski slopes and returns a small amount of snowmelt water available to plants outside the pistes at the beginning of the growing season. We tested if the use of artificial snow on the ski slopes and the decreased natural snow cover outside the ski slopes lead to changes in the leaf ecophysiology of dominant species in a ski area located in Northern Italy. Using carbon (¹³C/¹²C) and oxygen (¹⁸O/¹⁶O) stable isotope ratios in plant leaves, we estimated the intrinsic water use efficiency (iWUE) and we speculated about changes in photosynthesis and stomatal conductance. Furthermore, carbon and nitrogen concentration, pigments and dry matter content, and the specific area of leaves were measured. We found a higher iWUE of the plants on the ski slopes than outside, probably because the plants on the ski piste are exposed to a condition close to waterlogging that can lead them to regulate their stomata differently than the plants outside the pistes. This behaviour was observed particularly in Ranunculus acris and in Tussilago farfara, for these species the water surplus on the piste may have affected the plants' gas exchanges.

Atmospheric deposition of polychlorinated biphenyls to seasonal surface snow at four glacier sites on Svalbard, 2013-2014

During spring 2014 we collected annual surface snow from four glacial sites on Svalbard, an archipelago in the European Arctic. The sampling sites are 230 km apart from west to east, but are at varying elevations, affecting local atmospheric contaminant inputs. Samples were analyzed for 209 polychlorinated biphenyl (PCB) congeners. The western sites, Holtedahlfonna and Kongsvegen, had the highest ∑PCB flux (26.7 pg cm^-2 yr^-1 at Kongsvegen) while the lowest was at Lomonosovfonna, in central Svalbard (14.4 pg cm^-2 yr^-1). The greatest difference between sites was the trichlorobiphenyl homologue which was nearly four times greater at Kongsvegen than the eastern site at Austfonna. The most concentrated congeners at each site were PCB-52, 70 + 74, 95, 101, 110 comprising 32-39% of ∑PCB, similar to Clophen 40 which is comprised 27% of these congeners. Similar variance of these congeners in samples and Clophen 40 was verified by principal components analysis. Air mass back trajectories from likely source areas for all sites were similar, indicating no difference in frequency or distribution of PCB from long-distances, suggesting local PCB sources contributing to Kongsvegen. We found 2,3-DiCB (PCB-5) and 3,3'-DiCB (PCB-11) at all sites; neither was found in western commercial PCB mixtures. PCB-5 may be from the Russian PCB product "Trichlorobiphenyl" or is residue from production of pigment violet 23. PCB-11 may come from waste incineration in northern Europe containing various pigments. These results, in comparison to earlier data from Lomonosovfonna, suggest that PCB inputs are variable and are not declining over time.

Distribution of Policyclic aromatic hydrocarbons in a snow cover in the territory of Ivanovo city, Russia

The paper presents the results of a study of the content of 12 polyaromatic hydrocarbons (PAHs) in the snow cover of the city of Ivanovo (Russian Federation). It is shown that their average content exceeds the background level by 6.6 times, which made it possible to identify for which compounds the admission channels are associated with transboundary transport (naphthalene, pyrene, benz [b]fluorantin, benzo [a]pyrene and dibenz [a,h]anthracene), and for which with local emission sources (anthracene, phenanthrene, fluoranthene, chrysene, benz [k]fluorantin, and benzo [g,h,i]perylene). According to the known indicator ratios of the concentrations of PAHs, the main sources of release (pyrogenic and mixed) PAHs into the environment were estimated. The combination of experimental data in combination with factor analysis allowed identifying priority PAHs (naphthalene, fluoren, fluoranthene, benzo [a]pyrene and benzo [g,h,i]perylene), which should be included in the environmental monitoring programs of the region. Environmental risk assessments are given, which showed that the level of pollutant does not always adequately reflect the environmental impact for the territories. Thus, the contribution to the total PAH concentration of benz [b]fluorantin is only 9%, and to the amount of environmental risk - 51%. This must be taken into account in order to prioritize the control of individual components of PAHs in environmental objects.

Self-contamination from clothing in microplastics research

Self-contamination should not be underestimated when quantifying microplastics (MPs) in environmental matrices. Standardised and validated methodologies for MP sampling, extraction, and analysis are lacking. The various applications of plastics in our society have made them ubiquitous, even in clothing, rendering MP self-contamination inevitable. In the present study, we sampled lake sediment, snow, and ice, purposefully wearing red overalls composed of cotton; fibres from which we could quantify using Fourier-Transform Infrared Spectroscopy (FTIR), serving as an indication of possible self-contamination from clothes. The suitability of cotton as a representation of MP contamination was also evaluated. For all detected fibres, 25 ± 1%, 20 ± 7%, and 8 ± 6% for snow, ice, and sediment, respectively, originated from sampling attire. These findings demonstrate that self-contamination can play a significant role when quantifying MP pollution, highlighting that sampling conducted to date might have overestimated the presence of MP or even contaminated MP-free samples.

Microbial mercury methylation in the cryosphere: Progress and prospects

Mercury (Hg) is one of the most toxic heavy metals, and its cycle is mainly controlled by oxidation-reduction reactions carried out by photochemical or microbial process under suitable conditions. The deposition and accumulation of methylmercury (MeHg) in various ecosystems, including the cryospheric components such as snow, meltwater, glaciers, and ice sheet, and subsequently in the food chain pose serious health concerns for living beings. Unlike the abundance of knowledge about the processes of MeHg production over land and oceans, little is known about the sources and production/degradation rate of MeHg in cryosphere systems. In addition, processes controlling the concentration of Hg and MeHg in the cryosphere remains poorly understood, and filling this scientific gap has been challenging. Therefore, it is essential to study and review the deposition and accumulation by biological, physical, and chemical mechanisms involved in Hg methylation in the cryosphere. This review attempts to address knowledge gaps in understanding processes, especially biotic and abiotic, applicable for Hg methylation in the cryosphere. First, we focus on the variability in Hg concentration and mechanisms of Hg methylation, including physical, chemical, microbial, and biological processes, and transportation in the cryosphere. Then, we elaborate on the mechanism of redox reactions and biotic and abiotic factors controlling Hg methylation and biogeochemistry of Hg in the cryosphere. We also present possible mechanisms of Hg methylation with an emphasis on microbial transformation and molecular function to understand variability in Hg concentration in the cryosphere. Recent advancements in the genetic and physicochemical mechanisms of Hg methylation are also presented. Finally, we summarize and propose a method to study the unsolved issues of Hg methylation in the cryosphere.

Isotopic evidence for seasonality of microbial internal nitrogen cycles in a temperate forested catchment with heavy snowfall

The Hokuriku district of central Japan receives high levels of precipitation during winter, largely in the form of snow. This study aimed to elucidate the internal nitrogen dynamics in this temperate forested region with heavy snowfall using the triple oxygen and nitrogen isotopic compositions of NO₃^-. The isotopic compositions of NO₃^- in atmospheric depositions (P and Tf), with terrestrial components of the soil layer (A0, S25, S55, and S90), ground water (G), and output (St) were measured from 2015 to 2016 in a forested catchment located in the southern area of the Ishikawa Prefecture, Japan. Seasonal distributions of Δ¹⁷O(NO₃^-) showed a decreasing trend from the inputs to outputs of the ecosystem. We found relatively constant Δ¹⁷O(NO₃^-) values in the output components (G and St), but found highly fluctuating Δ¹⁷O(NO₃^-) values resulting from the seasonal variations in the nitrification activity within soil waters. Specifically, we observed a lower nitrifying activity in the top soil layer throughout cold periods, presumably due to the input of cold melted snow water. The general trend of increasing δ¹⁵N(NO₃^-) value from the input to output components, with the changes in denitrification hotspots from shallow to deeper soil layer, can be observed between warm and cold periods. Thus, the seasonal changes of hotspots related to microbial nitrification and denitrification could be noted due to the seasonal changes in the isotopic compositions of nitrate. The estimated ecosystem-scale gross nitrification and denitrification rates are low; however, the output components are relatively stable with low concentrations of nitrate, indicating that the plant uptake of nitrogen most probably occurs at greater rates and scales in this forested ecosystem. Future nitrogen deposition and the vulnerable dynamics of snow melting are likely to have impactful consequences on such localities.

Diversity of metals and metal-interactive bacterial populations in different types of Arctic snow and frost flowers: Implications on snow freeze-melt processes in a changing climate

Arctic snow has been shown to be a reactive interface for key physical, chemical, and microbiological processes, affecting the Arctic's oxidation, biodiversity, radiation, and climate. To explore the potential links between snow-borne metal contaminants and metal-interactive bacteria, to freezing/melting processes, we performed concurrent chemical characterization, genomic, and morphological analysis of five different Arctic snowpack (accumulated, blowing, fresh falling, surface hoar, and wind pack snow) and frost flower in Utqiaġvik (Barrow), Alaska, using Montreal urban snow as reference. Several complementary analytical techniques, including triple quad ICP-MS/MS along with various chromatography techniques, thermal ionization mass spectrometer (TIMS), high-resolution transition electron microscopy with electron dispersive X-ray spectroscopy (HR-TEM/EDS), and next generation sequencing (NGS), were deployed. Distinct metal composition and bacterial distribution among samples were observed. The concentration of 27 different transition, post-transition, rare, and radioactive metals were determined in molten snow and frost flower, as well as filtered samples. The range of three highest detected metal concentrations among samples were: Hg (3.294-134.485 μg/L), Fe (0.719-34.469 μg/L), and Sr (1.676-19,297.000 μg/L). NGS analysis led to the identification of metal interacting bacteria in all types of snow and frost flowers in the Arctic (blowing snow (1239), surface hoar snow (2243), windpack (2431), frost flowers (1440)), and Montreal urban snow (5498)) with specific bacterial genera such as: Acinetobacter, Arcenicella, Azospirillum (surface hoar snow), Arthrobacter, Paenibacillus (blowing snow), and Cycloclasticus, OM182 clade (frost flower). Several types of bacteria with confirmed or associated ice nucleation activity were observed in different types of snow, and frost flower including Pseudomonas genera (e.g., Pseudomonas fluorescens), Flavobacterium, Corynebacterium, and Pseudoxanthomonas. The implications of the above findings to snow-air interactions including nanoparticles, namely during melting and freezing cycles, and to probe the impact of various natural and anthropogenic activities are herein discussed.

REDUCTION IN AMBIENT GAMMA DOSE RATE FROM RADIOCESIUM DUE TO SNOW COVER

In the present study, variations in ambient gamma dose rate associated with snow cover were examined in a radioactive-contaminated site in Fukushima Prefecture, Japan. The ambient gamma dose rates decreased with increasing snow depth. The reduction trends were different between fresh snow (0.1-0.2 g/cm3) and granular snow (0.3-0.4 g/cm3) depending on snow density. Snow cover water content (snow water equivalent) calculated from snow depth and density was a key parameter governing the reduction in the ambient gamma dose rate. The ambient gamma dose rates reduced to 0.6 and 0.5 at 4 g/cm2 and 8 g/cm2 of snow water equivalent, respectively. Based on gamma-ray flux density distributions, the ambient gamma dose rates from the primary gamma rays decreased more compared to those from scattered gamma rays due to snow cover.

Athabasca oil sands region snow contains efficient micron and nano-sized ice nucleating particles

The Athabasca Oil Sands Region (AOSR) in Alberta, Canada, is an important source of atmospheric pollutants, such as aerosols, that have repercussions on both the climate and human health. We show that the mean freezing temperature of snow-borne particles from AOSR was elevated (-7.1 ± 1.8 °C), higher than mineral dust which freezes at ∼ -15 °C and is recognized as one of the most relevant ice nuclei globally. Ice nucleation of nanosized snow samples indicated an elevated freezing ability (-11.6 ± 2.0 °C), which was statistically much higher than snow-borne particles from downtown Montreal. AOSR snow had a higher concentration (∼2 orders of magnitude) of >100 nm particles than Montreal. Triple quadrupole ICP-(QQQ)-MS/MS analysis of AOSR and Montreal snow demonstrated that most concentrations of metals, including those identified as emerging nanoparticulate contaminants, were much more elevated in AOSR in contrast to Montreal: 34.1, 34.1, 16.6, 5.8, 0.3, 0.1, and 9.4 mg/m³ for Cr, Ni, Cu, As, Se, Cd, and Pb respectively, in AOSR and 1.3, 0.3, 2.0, <0.03, 0.1, 0.03, and 1.2 mg/m³ in Montreal snow. High-resolution Scanning Transmission Electron Microscopy/Energy-dispersive X-ray Spectroscopy (STEM-EDS) imaging provided evidence for various anthropogenic nano-materials, including carbon nanotubes resembling structures, in AOSR snow up to 7-25 km away from major oil sands upgrading facilities. In summary, particles characterized as coming from oil sands are more efficient at ice nucleation. We discuss the potential impacts of AOSR emissions on atmospheric and microphysical processes (ice nucleation and precipitation) both locally and regionally.

Snow gauge undercatch and its effect on the hydrogen and oxygen stable isotopic composition of precipitation

We investigated the influence of post-collection changes and snow gauge undercatch on the stable isotopic compositions of winter precipitation. Post-collection changes by evaporation or sublimation can be severe, and may be minimized, but not eliminated, by emptying collection gauges immediately after snowfall. Snow gauge undercatch caused two main effects: a small direct effect caused by preferential separation of snow particles during snowfall, and a much larger effect on the measured stable isotopic compositions of average annual precipitation as a result of under representation of winter precipitation. Despite these effects, however, we found little change to calculated local meteoric water lines (LMWL) for Saskatoon, SK, Canada. A comprehensive 27-year LMWL for Saskatoon which incorporates these effects can be described by δ²H = 7.69 ± 0.096 × δ¹⁸O - 2.22 ± 1.72 (r² = 0.97, n = 208).

Hydrochemical assessment (major ions and Hg) of meltwater in high altitude glacierized Himalayan catchment

Snowpack and glacial melt samples were collected to understand the hydrochemical, isotopic characteristics and the source of Hg contamination in high altitude glacierized Himalayan catchment. Both the snow and glacial melt were acidic in nature with calcium and magnesium as the dominant cations and bicarbonate and chloride as the dominant anions. The major ion concentrations for cations were found to be Ca²⁺ > Mg²⁺ > Na⁺ > K⁺ and HCO₃^- > Cl^- > SO₄^2- > NO₃^- for anions. The atmospheric processes like the precipitation source and aerosol scavenging control the snow chemistry and the weathering of the rocks modify the hydrochemistry of glacial melt. The samples of both the snow and glacial melt were classified as Ca-Mg-HCO₃^- type. The concentration of Hg in snow (154.95 ng L^-1) and glacial melt (112.04 ng L^-1) was highest (still lower compared to the maximum permissible limit (1000 ng L^-1) by WHO in drinking water) during summer season (August-September) and lowest (snow 2.2 and 40.01 ng L^-1 for glacial melt) during winter (November). The results reveal that mercury concentration in snowpacks is attributed to the combined mixing of long-range transport of pollutants via westerlies throughout the year and the industrial effluents coming from highly industrial belts of Panjab, Haryana, Rajasthan, Indo-Gangetic plains, and neighboring areas via southwest monsoons during August-September. However, in glacial melt, the Hg concentration was typically controlled by rate of melting, leaching, and percolation. Higher degree and rate of glacial melting decreases the Hg concentration in glacial melt. Stable isotopic analysis and backward air mass trajectory modeling also corroborate the source of precipitation from southwest monsoons during August-September, with its air mass trajectories passing through the highly industrialized belts of Indo-Gangetic plain and adjoining areas.

Elucidation of contamination sources for poly- and perfluoroalkyl substances (PFASs) on Svalbard (Norwegian Arctic)

A combination of local (i.e. firefighting training facilities) and remote sources (i.e. long-range transport) is assumed to be responsible for the occurrence of per- and polyfluoroalkyl substances (PFASs) in Svalbard (Norwegian Arctic). However, no systematic elucidation of local PFASs sources has been conducted yet. Therefore, a survey was performed aiming at identifying local PFAS pollution sources on the island of Spitsbergen (Svalbard, Norway). Soil, freshwater (lake, draining rivers), seawater, meltwater run-off, surface snow and coastal sediment samples were collected from Longyearbyen (Norwegian mining town), Ny-Ålesund (research facility) and the Lake Linnévatnet area (background site) during several campaigns (2014-2016) and analysed for 14 individual target PFASs. For background site (Linnévatnet area, sampling during April to June 2015), ΣPFAS levels ranged from 0.4 to 4 ng/L in surface lake water (n = 20). PFAS in meltwater from the contributing glaciers showed similar concentrations (~ 4 ng/L, n = 2). The short-chain perfluorobutanoate (PFBA) was predominant in lake water (60-80% of the ΣPFASs), meltwater (20-30%) and run-off water (40%). Long-range transport is assumed to be the major PFAS source. In Longyearbyen, five water samples (i.e. 2 seawater, 3 run-off) were collected near the local firefighting training site (FFTS) in November 2014 and June 2015, respectively. The highest PFAS levels were found in FFTS meltwater run-off (118 ng/L). Perfluorooctane sulfonic acid (PFOS) was the most abundant compound in the FFTS meltwater run-off (53-58% PFASs). At the research station Ny-Ålesund, seawater (n = 6), soil (n = 9) and freshwater (n = 10) were collected in June 2016. Low ΣPFAS concentrations were determined for seawater (5-6 ng/L), whereas high ΣPFAS concentrations were found in run-off water (113-119 ng/L) and soil (211-800 ng/g dry weight (dw)) collected close to the local FFTS. In addition, high ΣPFAS levels (127 ng/L) were also found in freshwater from lake Solvatnet close to former sewage treatment facility. Overall, at both FFTS-affected sites (soil, water), PFOS was the most abundant compound (60-69% of ΣPFASs). FFTS and landfill locations were identified as major PFAS sources for Svalbard settlements.

Light-absorbing impurities in snow of the Indian Western Himalayas: impact on snow albedo, radiative forcing, and enhanced melting

Seasonal snow cover in the Himalayas acts as source of fresh water for several Asian rivers such as Indus, Ganges, Brahmaputra, and Yangtze. Early loss of seasonal snow exposes the ice layer of the glaciers directly to sunlight, consequently leading to their ablation and alterations in discharge of glacier-fed rivers. Therefore, any alteration in the melting rate of the Himalayan snow pack can significantly affect the ecological balance in the region. Besides global warming, enhanced melting of snow, caused by light-absorbing impurities (LAIs) such as dust and elemental carbon (EC), has also been recognized as prominent cause of enhanced melting of snow in the Himalayas of China and Nepal. However, in light of vast area of the Himalayas and persistent emissions from India, studies, emphasizing the potential of LAIs to substantially affect the snow radiation budget of snow cover in IWHs, are still scanty. Therefore, in this study, field campaigns were made on three glaciers, i.e., Hamta, Beas Kund, and Deo Tibba, in IWHs to collect snow samples for estimation of LAIs. Snow of the studied glaciers was observed to be contaminated with 13.02 to 74.57 ng/g of EC and 32.14 to 216.54 μg/g of dust. Albedo simulations done using SNow and ICe Aerosol Radiation (SNICAR) model indicated that besides the changes caused by increased grain size, EC and dust, cumulatively induced 0.60 to 32.65% reduction in albedo of snow. Further assessment, constrained by measurements, illustrated that radiative forcing (RF), of 1.8 to 80 W/m², was instigated due to enhanced thermal absorption of snow. Ten hours of daily mean RFs in this range could correspond to 3 to 9.65 mm/d of snow melt and contribute significantly in reducing the seasonal snow cover in IWHs. Considering the consequences of LAIs-induced snow melt and lack of in situ observations in the IWHs, the outcomes of this study could assist researchers and policy makers in developing efficient climate models and framing mitigation measures, respectively.

Perfluorinated alkyl substances in snow as an atmospheric tracer for tracking the interactions between westerly winds and the Indian Monsoon over western China

Snow is an efficient scavenger for the deposition of contaminants. Atmospheric transport and snow deposition jointly control the distribution of pollutants in remote mountain/polar regions. But can the contaminants contained within snow be used to reflect the interactions of air circulation patterns? The physicochemical properties of perfluoroalkyl substances (PFASs) are unique because of their high water solubilities. Taking advantage of this, 15 surface-snow and 3 snow-pit samples were collected across a vast area of western China (spanning 20° of latitude and 25° of longitude), to investigate the concentrations, composition profiles (fingerprints), and deposition fluxes of PFASs. Both a high concentration (3974 pg/L) and deposition flux (4.0 μg/m²/yr) for a total of 16 PFASs were found in the snow at Yulong, the most southern sample site, possibly because of its close proximity to source regions of pollutants in South Asia and high rate of snow deposition. Perfluorobutanoic acid was the most commonly found chemical in snow, but in general the PFAS composition in the snow of western China showed large spatial differences, with long-chain (C > 10) PFASs being relatively dominant in the north and west of the region and short-chain (C < 6) PFASs in the south and east. On the basis of the different compositions of PFASs in the snow of western China and the previously reported features of pollutant sources in Europe and India, we found that PFASs in snow can be used as an atmospheric tracer for tracking the interactions between westerly winds and the Indian Monsoon. The belt along 33°N is a key location where both the Indian Monsoon and westerly winds can arrive/interact; however, the contribution of the monsoon was found to be above 70%, while that of the westerly winds can be lower than 30%. The western part of the 33°N belt was found to be more vulnerable to the Indian Monsoon, and could be grouped into the monsoon domain, while the influence of the westerly winds increased from west to east along the belt. This finding is opposite to previous results, which reported that the western part of the 33°N belt was mainly under the influence of the westerly winds, and for the first time quantifies the relative contribution of westerly winds and the Indian Monsoon to the atmospheric transport of chemicals.

Effect of snowmelt infiltration on groundwater recharge in a seasonal soil frost area: a case study in Northeast China

The effect of spring snowmelt infiltration in a seasonal soil frost area on groundwater recharge was evaluated by systematically monitoring meteorological factors, soil temperature and humidity, groundwater table and temperature, electrical conductivity, and the value of δ¹⁸O in a small field site over a 2-year period. The variation of soil temperature and humidity, groundwater table during the freezing period, and the snowmelt period respectively, as well as their correspondence to the relevant environmental factors, and the influencing factors of the permeability of frozen layer were analyzed. The results showed that the evaluation of precipitation infiltration in seasonal soil frost areas should be divided into three stages: a non-freezing period, a freezing period, and a snowmelt period. Snow is the main form of precipitation during the freezing period, and groundwater cannot be recharged. During the snowmelt period of spring, the snow cover that accumulated during the freezing period infiltrates together with rainfall and has a significant effect on groundwater recharge. The general precipitation infiltration process occurs after the frozen soil thaws completely. These research results can improve the accuracy of groundwater recharge calculations for snowmelt infiltration in the seasonal soil frost area of Northeast China and provide a scientific basis for the evaluation and management of regional water resources.

Environmental conditions affecting re-release from particulate matter of 4-Nonylphenol into an aqueous medium

4-nonylphenol is a persistent organic pollutant with endocrine-disrupting properties. A nonpolar product of microbial degradation derived from the surfactant nonylphenol polyethoxylate, 4-nonylphenol is capable of long-range transport attached to particulates. Bioactive concentrations of 4-nonylphenol have been found in the surface water, soils, snow, and particulate matter of the Eastern Sierra Nevada Mountains (USA) hundreds of miles from their origins. As a result of particulate deposition, seasonal and glacial snow pack concentrations measured 20 to 100 times higher than in surface waters. Batch desorption assays were run on particulate matter dosed with 4-nonylphenol. Desorption was measured in 63 to 500 μm particles under 2 different temperature conditions with varying fractions of organic carbon in turbulent or undisturbed states. Lower temperatures (4 °C) decreased the mean percentage of 4-nonylphenol released from particulates in disturbed and undisturbed conditions, whereas the mean percentage of 4-nonylphenol released at 20 °C was reduced by agitation. The effect of agitation at 4 °C was not practically or statistically significant. Particulates with a higher percentage of organic carbon (75%) released very little of the bound 4-nonylphenol (0.53%) compared with particulates containing 4 to 5% of organic carbon that released up to 13%. Larger particles released the least amount of 4-nonylphenol, whereas smaller particles released the most amount. Water and sediment samples taken from below the Palisades Glacier in the Sierra Nevada Mountains showed the greatest 4-nonylphenol concentrations directly below the glacier, implying that glacial particulates will release adsorbed 4-nonylphenol. Environ Toxicol Chem 2019;38:350-360. © 2018 SETAC.

Influence of gaseous and particulate species on neutralization processes of polar aerosol and snow - A case study from Ny-Ålesund

The inter-conversion of nitrogen and sulfur species between the gas and particulate phases and their interaction with alkaline species influences the acidity of the aerosols and surface snow. To better understand these processes, a short field campaign was undertaken in Ny-Ålesund, Svalbard, during 13th April 2012 to 24th April 2012. Air measurements were carried out through a particulate sampler equipped with denuders and filter packs for simultaneous collection of trace gases (HNO₃, NO₂, SO₂ and reactive nitrogen compounds) and aerosols, with daily collection of snow samples. Ionic composition of the samples was analyzed using ion chromatography technique. The results suggested that nitrate-rich aerosols are formed when PAN (peroxy acetyl nitrate) disassociates to form NO₂ and HNO₃ which further hydrolyzes to form pNO₃^- (particulate nitrate). This resulted in a high contribution of pNO₃^- (62%) to the total nitrogen budget over the study area. The acidity of the aerosols and snow evaluated through cation/anion ratio (C/A) indicated alkaline conditions with C/A>2. The bicarbonates/carbonates of Mg²⁺ played an important role in neutralization processes of surface snow while the role of NH₃ was dominant in aerosol neutralization processes. Such neutralization processes can increase the aerosol hygroscopicity causing warming. Chloride depletion in the snow was significant as compared to the aerosols, indicating two important processes, scavenging of coarse sea salt by the snow and gaseous adsorption of SO₂ on the snow surface. However, a more systematic and long term study is required for a better understanding of the neutralization processes and chemical inter-conversions.

Effects of snow depth manipulation on the releases of carbon, nitrogen and phosphorus from the foliar litter of two temperate tree species

The effect of snow depth on litter decomposition in cold regions has attracted substantial attention, but the importance of snow depth to the releases of carbon (C), nitrogen (N), and phosphorus (P) and the underlying mechanisms remain unclear. The releases of C, N, and P from the foliar litter of Pinus koraiensis and Quercus mongolica in response to snow depth changes were examined for 12 months in a temperate forest of Northeast China via a snow depth manipulation experiment that included snow-addition (SA), snow-removal (SR), and control (CK) treatments. We found that the SA treatment promoted the releases of C, N, and P from the foliar litter during the snow-covered season but slowed these processes during the following snow-free season; however, the SR treatment produced the opposite results. Compared with the CK treatment, the SA treatment increased the annual releases of C, N, and P by 2.52%, 0.50%, and 4.68%, respectively, whereas the SR treatment decreased the corresponding values. The elemental release during the snow-covered season was associated with the freeze-thaw cycle (FTC) and microbial biomass, whereas that during the snow-free season was mainly controlled by the temperature of the litter layer. Our findings indicated that the snow depth promoted the releases of C, N and P from the foliar litter of the two tree species, especially during the snow-covered season. These results deepen the understanding of the biogeochemical cycling in cold regions under global climate change scenarios.

Fragrances and PAHs in snow and seawater of Ny-Ålesund (Svalbard): Local and long-range contamination

Polar regions are fragile ecosystems threatened by both long-range pollution and local human contamination. In this context, the environmental distribution of the Personal Care Products (PCPs) represent a major knowledge gap. Following preliminary Antarctic studies, Fragrance Materials (FMs) were analyzed in the seawater and snow collected in the area of Ny-Ålesund, Svalbard, to investigate local and long-range contamination. Polycyclic Aromatic Hydrocarbons (PAHs), including Retene, were determined in parallel to help the identification of the governing processes. Concentrations of FMs up to 72 ng L^-1 were detected in the surface snow near the settlement and at increasing distances, in relation to the prevailing winds. PAHs follow a similar scheme, with levels of Retene up to 1.8 μg L^-1, likely deriving from the occurrence of this compound in the coal dust due to the previous mining activities in the area. The snow seasonal deposition of FMs and PAHs was estimated in a snowpit dug at the top of the Austre Brøggerbreen glacier, indicating the long-range atmospheric transport (LRAT) of these compounds.

Uranium record from a 3 m snow pit at Dome Argus, East Antarctica

Understanding the distribution and transport of Uranium is important because it can lead to both chemical and radiological toxicity. This study presents the Uranium concentrations time series from 1964 to 2009 obtained from a 3 m deep snow pit at Dome Argus, East Antarctic Plateau. The data shows that Uranium concentrations vary from 0.0067 pg g-1 to 0.12 pg g-1, with a mean concentration of 0.044 pg g-1. Its mean concentration is 2-3 folds lower than at West Antarctica study sites, such as the Antarctic Peninsula (mean 0.12 pg g-1), IC-6 (Ice Core-6) (mean 0.11 pg g-1) and a suite of ice cores from the US ITASE traverse. Before the mid-1980s, the varieties of Uranium concentrations are relatively stable, with a very low mean concentration of 0.016 pg g-1and its main source is sea salt deposition, while a small number of anthropogenic sources are likely to be caused by Uranium mining operations in South Africa. A remarkable increase of Uranium concentrations has occurred since the mid-1980s (by a factor of ~ 9) compared with the amount before the mid-1980s. This increase coincides with the Uranium records at IC-6 and Antarctic Peninsula (DP-07-01) during the same period, and are mostly attributed to Uranium mining operations in Australia as a potential primary anthropogenic Uranium source. Our observations suggest that Uranium pollution in the atmosphere might have already become a global phenomenon.

Seasonal soil/snow-air exchange of semivolatile organic pollutants at a coastal arctic site (Tromsø, 69°N)

Soils are a major reservoir of semivolatile organic pollutants such as polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs), and exert a control on their atmospheric occurrence. We present here an assessment of the atmospheric occurrence and seasonality of soil/snow-air partitioning and exchange of PCBs, PAHs, hexachlorobenzene (HCB), and hexachlorocyclohexanes (HCHs) in the arctic city Tromsø, northern Norway. The fugacities of the organic pollutants in soils and snow were determined using a soil fugacity sampler by equilibrating the air concentrations with those in the surface soil/snow. The concentrations in soils did not show a significant seasonality. Conversely, the ambient air concentrations and the soil (or snow) fugacity showed a clear seasonality for PCBs, HCH, HCB and some PAHs, related to temperature. Fugacities in soil/snow were correlated with those in the ambient gas phase, suggesting a close seasonal air-soil/snow coupling. Generally, there was a net deposition or close to equilibrium conditions during the winter, which contrasts with the net volatilization observed during the warmer periods. The chemicals with lower octanol-air partition coefficients showed a larger tendency for being volatilized and thus remobilized from this coastal arctic environment. Conversely, the more hydrophobic compounds were close to air-soil/snow equilibrium or showed a net deposition.

Semi volatile organic compounds in the snow of Russian Arctic islands: Archipelago Novaya Zemlya

Environmental contamination of the Arctic has widely been used as a worldwide pollution marker. Various classes of organic pollutants such as pesticides, personal care products, PAHs, flame retardants, biomass burning markers, and many others emerging contaminants have been regularly detected in Arctic samples. Although numerous papers have been published reporting data from the Canadian, Danish, and Norwegian Arctic regions, the environmental situation in Russian Arctic remains mostly underreported. Snow analysis is known to be used for monitoring air pollution in the regions with cold climate in both short-term and long-term studies. This paper presents the results of a nontargeted study on the semivolatile organic compounds detected and identified in snow samples collected at the Russian Artic Archipelago Novaya Zemlya in June 2016. Gas chromatography coupled to a high-resolution time-of-flight mass spectrometer enabled the simultaneous detection and quantification of a variety of pollutants including those from the US Environmental Protection Agency (EPA) priority pollutants list, emerging contaminants (plasticizers, flame retardants-only detection), as well as the identification of novel Arctic organic pollutants, (e.g., fatty acid amides and polyoxyalkanes). The possible sources of these novel pollutants are also discussed. GC-HRMS enabled the detection and identification of emerging contaminants and novel organic pollutants in the Arctic, e.g., fatty amides and polyoxyalkanes.

Hg in snow cover and snowmelt waters in high-sulfide tailing regions (Ursk tailing dump site, Kemerovo region, Russia)

Gold-bearing polymetallic Cu-Zn deposits of sulphur-pyrite ores were discovered in the Novo-Ursk region in the 1930s. The average content of mercury (Hg) was approximately 120 μg/g at the time. A comprehensive study of Hg distribution in waste of metal ore enrichment industry was carried out in the cold season on the tailing dump site and in adjacent areas. Mercury concentration in among snow particulate, dissolved and colloid fractions was determined. The maximal Hg content in particulate fraction from the waste tailing site ranged 230-573 μg/g. Such indices as the frequency of aerosol dust deposition events per units of time and area, enrichment factor and the total load allowed to establish that the territory of the tailing waste dump site had a snow cover highly contaminated with dust deposited at a rate of 247-480 mg/(m²∙day). Adjacent areas could be considered as area with low Hg contamination rate with average deposition rate of 30 mg/(m²∙day). The elemental composition of the aerosol dust depositions was determined as well, which allowed to reveal the extent of enrichment waste dispersion throughout adjacent areas. The amount of Hg entering environment with snowmelt water discharge was estimated. As a result of snowmelting, in 2014 the nearest to the dump site hydrographic network got Hg as 7.1 g with colloids and as 5880 g as particles. The results obtained allowed to assess the degree of Hg contamination of areas under the impact of metal enrichment industry.