Glacial River Research Articles

Organophosphate esters in Tianshan glacier runoff: Occurrence, degradation, risk, and flux

Organophosphate esters (OPEs) are a class of chemicals of emerging concern. However, little is known about the environmental behavior, transformation and ecological risk of OPEs in mid-latitude glacial environments. This study investigated the concentration and composition characteristics of organophosphate triesters (tri-OPEs) and organophosphate diesters (di-OPEs) in the runoff of Urumqi No. 1 Glacier and Koxkar Glacier in the Tianshan Mountains, and estimated the output of them from glacial rivers. The total concentration of tri-OPEs (Σ13tri-OPEs) was 8565 pg/L in glacier surface meltwater and 6568 pg/L in proglacial rivers. Di-OPEs exhibited lower concentrations, with 99 pg/L and 117 pg/L (Σ10di-OPEs) in glacier surface meltwater and proglacial rivers, respectively. Tri-OPEs exhibited clear diurnal variations, which are presumed to be related to environmental temperature, while di-OPEs did not show an obvious trend. Although risk quotients (RQs) indicated that the concentrations of OPEs pose minimal risk to the glacier aquatic environment, the Toxicological Priority Index (ToxPi) score results showed that tris(2-chloroethyl) phosphate (TCEP) has the highest priority and therefore requires more attention. The total output flux of OPEs (Σ13tri-OPEs and Σ10di-OPEs) in glacial rivers throughout the entire Tianshan region was estimated to be ∼ 847 kg/year. Given the continuity of glacial melting and the accumulation of emerging pollutants in glaciers, the process of melting poses an increasing risk to freshwater resources, warranting heightened attention.

Hydrographic and hydrochemical characteristics of selected groundwater outflows in desert and semi-desert areas

The presence of natural groundwater outflows depends on many factors, such as lithology, geological structure, and climate. Areas with particularly poor crenological recognition are arid and semi-arid regions, primarily due to rarity of groundwater outflows in these locations. The article presents the hydrographic and hydrochemical characteristics of selected groundwater outflows in arid and semi-arid areas. In addition to hydrographic mapping, basic physical parameters of water were measured in selected springs, such as temperature (T, °C), electrolytic conductivity (EC, μS∙cm–1), and reaction (pH, –). Laboratory analyses determined the major cations and anions in water: Ca2+, Mg2+, Na+, K+, NH4+, SO42−, Cl−, NO3−, Br−, PO43−,. The analyses were performed using an ion chromatograph Metrohm 850 Professional IC. Twenty-four natural groundwater outflows in South America, Africa, and Asia were selected for research. It was found that the vast majority of outflows are transit sources. Their supply area may be far from discharge points. The supply source is rainwater or meltwater from high mountain massifs. Other types of outflow are springs of alluvial fans and braided rivers. They are fed by waters from glacial rivers, which infiltrate alluvial deposits and flow back to the surface. Hydrochemical analysis has shown that the physicochemical properties of water in dry areas vary significantly. Still in the hydrochemical type, there is a predominance of sulphate, chloride, and sodium ions. This distinguishes the spring waters from these areas in temperate latitudes, which are dominated by bicarbonate and calcium ions.

Oxidation is a potentially significant methane sink in land-terminating glacial runoff

Globally, aquatic ecosystems are one of the largest but most uncertain sources of methane, a potent greenhouse gas. It is unclear how climate change will affect methane emissions, but recent work suggests that glacial systems, which are melting faster with climate change, may be an important source of methane to the atmosphere. Currently, studies quantifying glacial emissions are limited in number, and the role of methanotrophy, or microbial methane oxidizers, in reducing atmospheric emissions from source and receiving waters is not well known. Here we discuss three potential sites for methane oxidation that could mitigate emissions from glaciers into the atmosphere: under ice oxidation, oxidation within proglacial lakes, and oxidation within melt rivers. The research presented here increases the number of glacial sites with methane concentration data and is one of only a few studies to quantify the net microbial activity of methane production and oxidation in two types of land-terminating glacial runoff (lake and river). We find that oxidation in a glacial river may reduce atmospheric methane emissions from glacial melt by as much as 53%. Incorporating methane oxidation in estimates of glacial methane emissions may significantly reduce the estimated magnitude of this source in budgeting exercises.

Rainfall Impacts Dissolved Organic Matter and Cation Export From Permafrost Catchments and a Glacial River During Late Summer in Northeast Greenland

ABSTRACTOngoing and amplified climate change in the Arctic is leading to glacier retreat and to the exposure of an ever‐larger portion of non‐glaciated permafrost‐dominated landscapes. Warming will also cause more precipitation to fall as rain, further enhancing the thaw of previously frozen ground. Yet, the impact of those perturbations on the geochemistry of Arctic rivers remains a subject of debate. Here, we determined the geochemical composition of waters from various contrasting non‐glacial permafrost catchments and investigated their impact on a glacially dominated river, the Zackenberg River (Northeast Greenland), during late summer (August 2019). We also studied the effect of rainfall on the geochemistry of the Zackenberg River, its non‐glacial tributaries, and a nearby independent non‐glacial headwater stream Grænse. We analyzed water properties, quantified and characterized dissolved organic matter (DOM) using absorbance and fluorescence spectroscopy and radiocarbon isotopes, and set this alongside analyses of the major cations (Ca, Mg, Na, and K), dissolved silicon (Si), and germanium/silicon ratios (Ge/Si). The glacier‐fed Zackenberg River contained low concentrations of major cations, dissolved Si and dissolved organic carbon (DOC), and a Ge/Si ratio typical of bulk rock. Glacial DOM was enriched in protein‐like fluorescent DOM and displayed relatively depleted radiocarbon values (i.e., old DOM). Non‐glacial streams (i.e., tributaries and Grænse) had higher concentrations of major cations and DOC and DOM enriched in aromatic compounds. They showed a wide range of values for radiocarbon, Si and Ge/Si ratios associated with variable contributions of surface runoff relative to deep active layer leaching. Before the rain event, Zackenberg tributaries did not contribute notably to the solute export of the Zackenberg River, and supra‐permafrost ground waters governed the supply of solutes in Zackenberg tributaries and Grænse stream. After the rain event, surface runoff modified the composition of Grænse stream, and non‐glacial tributaries strongly increased their contribution to the Zackenberg River solute export. Our results show that summer rainfall events provide an additional source of DOM and Si‐rich waters from permafrost‐underlain catchments to the discharge of glacially dominated rivers. This suggests that the magnitude and composition of solute exports from Arctic rivers are modulated by permafrost thaw and summer rain events. This event‐driven solute supply will likely impact the carbon cycle in rivers, estuaries, and oceans and should be included into future predictions of carbon balance in these vulnerable Arctic systems.

Distinct influences of altitude on microbiome and antibiotic resistome assembly in a glacial river ecosystem of Mount Everest

The profound influences of altitude on aquatic microbiome were well documented. However, differences in the responses of different life domains (bacteria, microeukaryotes, viruses) and antibiotics resistance genes (ARGs) in glacier river ecosystems to altitude remain unknown. Here, we employed shotgun metagenomic and amplicon sequencing to characterize the altitudinal variations of microbiome and ARGs in the Rongbu River, Mount Everest. Our results indicated the relative influences of stochastic processes on microbiome and ARGs assembly in water and sediment were in the following order: microeukaryotes < ARGs < viruses < bacteria. Moreover, distinct assembly patterns of the microbiome and ARGs were found in response to differences in altitude, the latter of which shift from deterministic to stochastic processes with increasing differences in altitude. Partial least squares path modeling revealed that mobile genetic elements (MGEs) and viral β-diversity were the major factors influencing the ARG abundances. Taken together, our work revealed that altitude-caused environmental changes led to significant changes in the composition and assembly processes of the microbiome and ARGs, while ARGs had a unique response pattern to altitude. Our findings provide novel insights into the impacts of altitude on the biogeographic distribution of microbiome and ARGs, and the associated driving forces in glacier river ecosystems.

Use of satellite imagery to estimate distribution and abundance of Cumberland Sound beluga whales reveals frequent use of a glacial river estuary

Limiting disturbance in critical habitats is an important part of ensuring the well-being and sustainability of populations at risk, such as Cumberland Sound beluga whales (Delphinapterus leucas). Using non-disruptive Very High Resolution (VHR) satellite imagery, an emerging tool in cetacean monitoring, we aimed to estimate summer abundance and identify critical habitat for Cumberland Sound beluga whales. Specifically we looked in fiords that comprise their summer distribution, such as Clearwater Fiord where there is a large estuary, an important habitat to many beluga populations. Satellite images of the area were collected in 2020 and 2021, at 30 cm resolution, and in 2022 at 50 cm resolution. We evaluated beluga whale distribution using Kernel density, and identified critical habitats as areas consistently part of the beluga whale core distribution across years. Clearwater Fiord abundance estimates were corrected for whales that were too deep to be identified in the images. The estimates were significantly lower in 2021 (197 whales, 95%CI: 180-216) and 2022 (194 whales, 95%CI: 172-218) compared to 2020 (393 whales, 95%CI: 366-422). Other fiords were only imaged in 2021 and 2022, resulting in average corrected abundance estimates for all fiords of 462 (95% CI: 425-502) and 252 (95%CI: 226-280) beluga whales, respectively. Downsampling of 30 cm images to 50 cm resulted in up to 45% fewer whales detected. The only critical habitat identified within the summer distribution was in Clearwater Fiord, in or near the estuary freshwater plume and in a bay to the west of the plume. The identified critical habitats should be areas of consideration in the continued discussion on the protection and sustainability of the Cumberland Sound beluga whale population.

A Comprehensive Biogeochemical Assessment of Climate‐Threatened Glacial River Headwaters on the Eastern Slopes of the Canadian Rocky Mountains

AbstractClimate change is driving the loss of alpine glaciers globally, yet investigations about the water quality of rivers stemming from them are few. Here we provide an overview assessment of a biogeochemical data set containing 200+ parameters that we collected between 2019 and 2021 from the headwaters of three such rivers (Sunwapta‐Athabasca, North Saskatchewan, and Bow) which originate from the glacierized eastern slopes of the Canadian Rocky Mountains. We used regional hydrometric data sets to accurately model discharge at our 14 sampling sites. We created a Local Meteoric Water Line (LMWL) using riverine water isotope signatures and compared it to collected regional rain, snow, and glacial ice signatures. Principal component analyses of river physicochemical measures revealed distance from glacier explained more data variability than other spatiotemporal factors (i.e., season, year, or river). Discharge, chemical concentrations, and watershed areas were then used to model site‐specific open water season yields for 25 parameters. Chemical yields followed what would generally be expected along river continuums from glacierized to montane altitudinal life zones, with landscape characteristics driving chemical sources and sinks. For instance, particulate chemical yields were generally highest near source glaciers with proglacial lakes acting as settling ponds, whereas most dissolved yields varied by parameter and site. As these headwaters continue to evolve with glacier mass loss, the data set and analyses presented here can be used as a contemporary baseline to mark future change against. Further, following this initial assessment of our data set, we encourage others to mine it for additional biogeochemical studies.

Dissolved silicon and nitrogen in glacial rivers and water of Blago bay (Russian Arctic, Novaya Zemlya): origin, variability and spreading

Hydrochemical studies of watercourses and the water area of Blagopoluchia bay (Novaya Zemlya, Arctic, Russia) have been carried out. The concentrations of nutrients in rivers and streams are higher than those in the water area of Blagopoluchia bay. It is shown that the concentration of silicon in constantly flowing rivers is 1–13 μM, the concentration of NO3 — 0.5–8, for small and temporary streams these values are higher and are in the range of 18–46 μM Si, 1–11 μM NO3– . The influence of streams and rivers flowing into Blagopoluchia Bay on the water area of the bay is local and extends to 1 km from the mouth, and does not influence the Kara Sea nutrient content.

Enhancing Flood Simulation in Data-Limited Glacial River Basins through Hybrid Modeling and Multi-Source Remote Sensing Data

Due to the scarcity of observational data and the intricate precipitation–runoff relationship, individually applying physically based hydrological models and machine learning (ML) techniques presents challenges in accurately predicting floods within data-scarce glacial river basins. To address this challenge, this study introduces an innovative hybrid model that synergistically harnesses the strengths of multi-source remote sensing data, a physically based hydrological model (i.e., Spatial Processes in Hydrology (SPHY)), and ML techniques. This novel approach employs MODIS snow cover data and remote sensing-derived glacier mass balance data to calibrate the SPHY model. The SPHY model primarily generates baseflow, rain runoff, snowmelt runoff, and glacier melt runoff. These outputs are then utilized as extra inputs for the ML models, which consist of Random Forest (RF), Gradient Boosting (GDBT), Long Short-Term Memory (LSTM), Deep Neural Network (DNN), Support Vector Machine (SVM) and Transformer (TF). These ML models reconstruct the intricate relationship between inputs and streamflow. The performance of these six hybrid models and SPHY model is comprehensively explored in the Manas River basin in Central Asia. The findings underscore that the SPHY-RF model performs better in simulating and predicting daily streamflow and flood events than the SPHY model and the other five hybrid models. Compared to the SPHY model, SPHY-RF significantly reduces RMSE (55.6%) and PBIAS (62.5%) for streamflow, as well as reduces RMSE (65.8%) and PBIAS (73.51%) for floods. By utilizing bootstrap sampling, the 95% uncertainty interval for SPHY-RF is established, effectively covering 87.65% of flood events. Significantly, the SPHY-RF model substantially improves the simulation of streamflow and flood events that the SPHY model struggles to capture, indicating its potential to enhance the accuracy of flood prediction within data-scarce glacial river basins. This study offers a framework for robust flood simulation and forecasting within glacial river basins, offering opportunities to explore extreme hydrological events in a warming climate.

Improvement of streamflow simulation by combining physically hydrological model with deep learning methods in data-scarce glacial river basin

Robust streamflow simulation at glacial basins is essential for the improvement of water sustainability assessment, water security evaluation, and water resource management under the rapidly changing climate. Therefore, we proposed a hybrid modelling framework to link the SWAT+ model considering glacial hydrological processes (GSWAT+) with Gated Recurrent Unit (GRU) neural networks to improve the model simulations and to establish a framework for the robust simulation and forecast of high and low flows in glacial river basins, which could be further used for the explorations of extreme hydrological events under a warming climate. The performance of different models (GSWAT+, GRU, and GRU-GSWAT+, respectively) were thoroughly investigated based on numerical experiments for two data-scarce glacial watersheds in Northwest China. The results suggested that the hybrid model (GRU-GSWAT+) outperformed both the individual deep learning (DL) model (GRU) and the conventional hydrological model (GSWAT+) in terms of simulation and prediction accuracy. Notably, the proposed hybrid model considerably enhanced the simulations of low and high flows that the conventional GSWAT+ failed to capture. Furthermore, utilizing suitable data integration (DI) schemes on feature and target sequences can substantially help to strengthen model stability and representativeness for monthly and annual streamflow sequences. Specifically, introducing one order differential method and decomposition approach, such as ensemble empirical signal decomposition (EEMD) and complete EEMD with adaptive noise (CEEMDAN), into feature and target sequences enriched the learnable ancillary information, which consequently strengthened the predictive performance of the proposed model. Overall, the proposed hybrid model with the suitable DI scheme has the potential to significantly enhance the accuracy of streamflow simulation in data-scarce glacial river basins. This hybrid model not only upheld the fundamental physical principles from the GSWAT+ model, but also considerably mitigated the accumulated bias errors, which caused by the shortage of climate data and inadequate hydrological principles, by using DL based model and DI schemes.

New strategies for the new environment in Spitsbergen fjords (Arctic). Scattering of the feather star Heliometra glacialis (Echinodermata, unstalked crinoid) clinging to a crab

This publication presents an unusual behavior of a comatulid crinoid that was tentatively attributed to Heliometria glacialis (Echinodermata, Crinoidea, Heliometrinae). This unstalked crinoid was observed clinging on Hyas sp. crabs in the inner part of the Spitsbergen fjords heavily loaded with suspension runoff. In situ observations were made using a 16-h and 45-min time-lapse sequence showing the decompositions of Atlantic cod. During the exposure, apart from typical organisms such as carrion crustaceans, crabs, and starfish, three individuals of crinoids were observed. One of the crinoids was clinging to the edge of the platform for most of the exposure. The remaining two individuals were observed attached to the carapace of Hyas sp. crabs for 6 h 55 min. It was also found, based on analysis of the video material from 202 locations examined in the summer season between 2015 and 2020 using a drop camera, two additional locations showing comatulid crinoids. Both locations in the Ekmanfjorden and in the interior of the Vanmijenfjorden are areas under the strong influence of a glacier meltwater plum or a glacial river runoff. So far, comatulid crinoids have been found mainly in locations outside of the influence of turbid waters from fjords. We interpret this new behavior within comatulid crinoids as an adaptation that help colonize new regions gradually exposed by the retreating glaciers.

Glacial meltwater and seasonality influence community composition of diazotrophs in Arctic coastal and open waters.

The Arctic Ocean is particularly affected by climate change with unknown consequences for primary productivity. Diazotrophs-prokaryotes capable of converting atmospheric nitrogen to ammonia-have been detected in the often nitrogen-limited Arctic Ocean but distribution and community composition dynamics are largely unknown. We performed amplicon sequencing of the diazotroph marker gene nifH from glacial rivers, coastal, and open ocean regions and identified regionally distinct Arctic communities. Proteobacterial diazotrophs dominated all seasons, epi- to mesopelagic depths and rivers to open waters and, surprisingly, Cyanobacteria were only sporadically identified in coastal and freshwaters. The upstream environment of glacial rivers influenced diazotroph diversity, and in marine samples putative anaerobic sulphate-reducers showed seasonal succession with highest prevalence in summer to polar night. Betaproteobacteria (Burkholderiales, Nitrosomonadales, and Rhodocyclales) were typically found in rivers and freshwater-influenced waters, and Delta- (Desulfuromonadales, Desulfobacterales, and Desulfovibrionales) and Gammaproteobacteria in marine waters. The identified community composition dynamics, likely driven by runoff, inorganic nutrients, particulate organic carbon, and seasonality, imply diazotrophy a phenotype of ecological relevance with expected responsiveness to ongoing climate change. Our study largely expands baseline knowledge of Arctic diazotrophs-a prerequisite to understand underpinning of nitrogen fixation-and supports nitrogen fixation as a contributor of new nitrogen in the rapidly changing Arctic Ocean.

Spatial characterization of chemical weathering in a proglacial river system, southcentral Alaska

Major constituent concentrations (Na+, K+, Ca2+, Mg2+, HCO3−, SO42−, Cl−, NO3−) were determined for a 121 km reach of the proglacial Matanuska River, associated tributaries, and five additional glacial rivers on the Kenai Peninsula of southcentral Alaska during peak flow conditions in July 2019. Mass balance and mixing models were utilized to gain insight to chemical weathering processes and carbon feedback implications along the sampling transect. Solute compositions of the Matanuska River varied spatially, shifting from carbonate dominance near the terminus of the Matanuska Glacier to a carbonate-silicate weathering signature in the lower reaches of the river. Geochemical modeling suggests that carbonate dissolution closest to the Matanuska Glacier terminus is driven by sulfuric acid produced from the oxidation of sulfide minerals in the subglacial and proglacial system that acts as a source of CO2. This contrasts with the lower reaches of the Matanuska River, its tributaries, and other Kenai glacial rivers, where mineral dissolution is dominated by carbonic acid and weathering acts as a sink of atmospheric CO2. The spatial variations observed in stream and river compositions are predominantly attributed to the local lithological variations across the catchment, with subglacial weathering signatures observed in the meltwater solute compositions closest to the Matanuska Glacier terminus. This study highlights the importance of spatial sampling in proglacial systems, as proglacial water chemical signatures and carbon feedback implications can shift significantly away from the glacial terminus.

Size-age population structure of an endangered and anthropogenically introgressed northern Adriatic population of marble trout (Salmo marmoratus Cuv.): insights for its conservation and sustainable exploitation.

Salmonid species are main actors in the Italian socio-ecological landscape of inland fisheries. We present novel data on the size-age structure of one of the remnant Italian populations of the critically endangered marble trout Salmo marmoratus, which co-occurs with other stocked non-native salmonids in a large glacial river of the Lake Maggiore basin (Northern Italy-Southern Switzerland). Like other Italian native trout populations, the Toce River marble trout population is affected by anthropogenic introgression with the non-native brown trout S. trutta. Our sample includes 579 individuals, mainly collected in the Toce River main channel. We estimated the length-weight relationship, described the population size-age structure, estimated the age-specific growth trajectories, and fit an exponential mortality model. A subset of the sample was also used to measure numerical and biomass density. The estimated asymptotic maximum length is ~105 cm total length (TL). Mean length at first maturity is ~55 cm TL, and mean length at maximum yield per recruit is ~68 cm TL. Approximately 45-70% of the population are estimated to die annually, along with a fishing annual mortality of ~37%, with an exploitation ratio of ~0.5. The frequency distribution of length classes in a sample collected by angling shows that ~80% of the individuals that could be retained according to the current recreational fishing regulations likely never reproduced, and large fish disproportionally contributing to recruitment are fished and retained. We identify possible overfishing risks posed by present regulations, and propose updated harvest-slot length limits to mitigate such risks. More detailed and long-term datasets on this system are needed to more specifically inform the fishery management and monitor the effects of any change in the management strategy on the size-age structure of the marble trout population of the Toce River.

Glacial meltwater determines the balance between autotrophic and heterotrophic processes in a Greenland fjord

Global warming accelerates melting of glaciers and increases the supply of meltwater and associated inorganic particles, nutrients, and organic matter to adjacent coastal seas, but the ecosystem impact is poorly resolved and quantified. When meltwater is delivered by glacial rivers, the potential impact could be a reduction in light and nutrient availability for primary producers while supplying allochthonous carbon for heterotrophic processes, thereby tipping the net community metabolism toward heterotrophy. To test this hypothesis, we determined physical and biogeochemical parameters along a 110-km fjord transect in NE Greenland fjord, impacted by glacial meltwater from the Greenland Ice Sheet. The meltwater is delivered from glacier-fed river outlets in the inner parts of the fjord, creating a gradient in salinity and turbidity. The planktonic primary production was low, 20-45 mg C m-2 d-1, in the more turbid inner half of the fjord, increasing 10-fold to around 350 mg C m-2 d-1 in the shelf waters outside the fjord. Plankton community metabolism was measured at three stations, which displayed a transition from net heterotrophy in the inner fjord to net autotrophy in the coastal shelf waters. Respiration was significantly correlated to turbidity, with a 10-fold increase in the inner turbid part of the fjord. We estimated the changes in meltwater input and sea ice coverage in the area for the last 60 y. The long-term trend and the observed effects demonstrated the importance of freshwater runoff as a key driver of coastal ecosystem change in the Arctic with potential negative consequences for coastal productivity.

Soil diazotrophic abundance, diversity, and community assembly mechanisms significantly differ between glacier riparian wetlands and their adjacent alpine meadows.

Global warming can trigger dramatic glacier area shrinkage and change the flux of glacial runoff, leading to the expansion and subsequent retreat of riparian wetlands. This elicits the interconversion of riparian wetlands and their adjacent ecosystems (e.g., alpine meadows), probably significantly impacting ecosystem nitrogen input by changing soil diazotrophic communities. However, the soil diazotrophic community differences between glacial riparian wetlands and their adjacent ecosystems remain largely unexplored. Here, soils were collected from riparian wetlands and their adjacent alpine meadows at six locations from glacier foreland to lake mouth along a typical Tibetan glacial river in the Namtso watershed. The abundance and diversity of soil diazotrophs were determined by real-time PCR and amplicon sequencing based on nifH gene. The soil diazotrophic community assembly mechanisms were analyzed via iCAMP, a recently developed null model-based method. The results showed that compared with the riparian wetlands, the abundance and diversity of the diazotrophs in the alpine meadow soils significantly decreased. The soil diazotrophic community profiles also significantly differed between the riparian wetlands and alpine meadows. For example, compared with the alpine meadows, the relative abundance of chemoheterotrophic and sulfate-respiration diazotrophs was significantly higher in the riparian wetland soils. In contrast, the diazotrophs related to ureolysis, photoautotrophy, and denitrification were significantly enriched in the alpine meadow soils. The iCAMP analysis showed that the assembly of soil diazotrophic community was mainly controlled by drift and dispersal limitation. Compared with the riparian wetlands, the assembly of the alpine meadow soil diazotrophic community was more affected by dispersal limitation and homogeneous selection. These findings suggest that the conversion of riparian wetlands and alpine meadows can significantly alter soil diazotrophic community and probably the ecosystem nitrogen input mechanisms, highlighting the enormous effects of climate change on alpine ecosystems.

Distribution and sources of REEs in suspended particulate matter of cryospheric water in northeast Tibetan plateau

Rare earth elements (REE) are widely used as tracers for surface processes due to their zonal differences in composition and special geochemical indicators. In this study, we collected 30 glacial meltwater samples from a large area of the northeastern Tibetan Plateau region and analyzed the REE composition of suspended particulate matter (SPM, d > 0.45 μm) to explore the spatial distribution, origins and the influencing factors of REE in SPM. Results suggested that chondrite-normalized REE distribution patterns were characterized by steep LREE and relatively flat HREE, which is different from that of PAAS-normalized. The high (La/Sm)N ratio and low (Gd/Yb)N ratio indicated that the degree of LREE fractionation was higher than that of HREE. We found an obvious correlation between REE concentration and SPM concentration, indicating that REE concentration in glacial runoff was significantly affected by SPM contents. It was found that Ce/Ce* decreased first and then increased with the decrease of altitude in the glacial river basins, which may contribute to weathering, oxidation, and physicochemical property of the water environment in the study areas. At the glacier forefield, the degree of weathering is intense, resulting in the highest Ce/Ce* value in the altitude between 3200 and 4800 m. However, this was not obvious in non-glacial regions. Compared REE geochemical parameters (e.g., LREE/HREE, Eu/Eu*, LaN/SmN) of SPM in the glacier basin with those of Asian potential dust sources and long-range transport (LRT) dust deposited on the studied glaciers, we found that the SPM in the glacial river basins is affected by lithology of parent materials, the LRT dust from the surrounding deserts, the release of ice/snow dust, and the detrital material from local rock weathering. This study provides a new perspective on the composition, distribution and variation in the altitude of REE in the glacial river basin of the northeast TP, and thus is of significance to improve the understanding of the source and migration process of REE in SPM of glacial river basins.

FEATURES OF THE CONTENT OF MICROELEMENTS MO, MN, ZN IN THE GLACIER WATER OF THE CENTRAL CAUCASUS FOR THE PERIOD 2019-2021

The results of a study of the content of the main microelements (Mo, Mn, Zn) in the waters of three glacial rivers of the Central Caucasus with glacial feeding during winter low water periods and summer rain floods are presented. It is shown that in the dynamics of their concentrations there is a downward trend from the zone of the upper reaches to the zone of entry into the low-mountain zone and the features of the level of pollution inherent in each river in the upper reaches. The studies were carried out over a three-year period — from 2019 to 2021. The main water pollutants in the rivers Malka, Baksan, Terek have been identified. The concentrations of trace elements in the water of mountain rivers during the main phases of the hydrological regime are presented. A comparative interannual analysis was carried out.

Microbial Response to Increased Temperatures Within a Lava-Induced Hydrothermal System in Iceland: An Analogue for the Habitability of Volcanic Terrains on Mars.

Fossil hydrothermal systems on Mars are important exploration targets because they may have once been habitable and could still preserve evidence of microbial life. We investigated microbial communities within an active lava-induced hydrothermal system associated with the 2014-2015 eruption of Holuhraun in Iceland as a Mars analogue. In 2016, the microbial composition in the lava-heated water differed substantially from that of the glacial river and spring water sources that fed into the system. Several taxonomic and metabolic groups were confined to the water emerging from the lava and some showed the highest sequence similarities to subsurface ecosystems, including to the predicted thermophilic and deeply branching Candidatus Acetothermum autotrophicum. Measurements show that the communities were affected by temperature and other environmental factors. In particular, comparing glacial river water incubated in situ (5.7°C, control) with glacial water incubated within a lava-heated stream (17.5°C, warm) showed that microbial abundance, richness, and diversity increased in the warm treatment compared with the control, with the predicted major metabolism shifting from lithotrophy toward organotrophy and possibly phototrophy. In addition, thermophilic bacteria isolated from the lava-heated water and a nearby acidic hydrothermal system included the known endospore-formers Geobacillus stearothermophilus and Paenibacillus cisolokensis as well as a potentially novel taxon within the order Hyphomicrobiales. Similar lava-water interactions on Mars could therefore have generated habitable environments for microbial communities.

Hydrogeological Model of the Forefield Drainage System of Werenskioldbreen, Svalbard

The significant recession of Arctic glaciers caused by climate warming is expanding their proglacial zones. Thus, their importance for the hydrology of glacierised basins is growing. In contrast to the surface waters in such areas, the role of groundwater in the hydrological balance of Svalbard catchments is poorly known. This paper presents the hydrogeological conditions and groundwater flow within the permafrost active layer in the forefield of the Werenskioldbreen glacier basin (44.1 km2), 61% of which is glacierised. Based on field studies of groundwater in the 2017 ablation season and laboratory analyses of the hydrogeological properties of proglacial sediments, a three-dimensional groundwater flow model (FEFLOW) for part of the glacier forefield (4.8 km2) was developed. The main results show the components and characteristics of the groundwater balance and indicate the preferential groundwater flow paths. The volume of water retained in the sediments of the marginal zone is 1.0073 mln m3. The maximum potential free pore space that could be filled by water is 2.0689 mln m3. The calculated groundwater discharge for average conditions is 6076.9 m3 d−1, which is about 2% of the total seasonal catchment runoff from the main glacial river. The results of the spatial analysis for the groundwater depth and the groundwater flow directions are also presented. There need to be further detailed studies of hydrogeological processes in glacial basins in Svalbard in order to develop existing knowledge.