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The Arctic warms four times faster than the global average, resulting in widespread permafrost thaw. Organic matter that was stored in permanently frozen soil for up to millennia now becomes available to microbial decomposition. Warming might also alter microbial community composition and physiology and thus change the decomposition potential of soils. Our current knowledge about permafrost soil organic matter (SOM) composition and decomposition is limited, particularly in regard to the heterogeneity of permafrost landscapes, thus hampering our ability to predict possible permafrost soil feedbacks to climate change. The objective of this study was to characterize SOM and microbial community composition of the active layer and the upper permanently frozen soil from permafrost-affected polygonal lowland tundra.We collected more than 80 soil samples from four different soil layers (organic, mineral, cryoturbated, permanently frozen) from three developmental stages of ice-wedge polygons (low-center, flat-center, high-center polygons) in NW Canada, and analyzed organic matter composition by a pyrolysis-GC/MS fingerprinting approach and microbial community composition by amplicon sequencing of the 16S rRNA gene (bacteria, archaea) and the ITS1 region (fungi).Our results suggest that the spatial heterogeneity of permafrost soils is not only reflected in soil physical parameters, but also in the chemical composition of organic matter and the composition of microbial communities. The organic soil layer comprised both the highest microbial diversity and the most diverse SOM composition. The distribution of major compound classes (carbohydrates, lignins, lipids, N-compounds, phenols & aromatics) differed between organic, mineral, cryoturbated and permanently frozen organic matter. This pattern followed a gradient from low to high organic matter degradation with soil depth. Soil organic matter composition also differed among polygon types, indicating different decomposition pathways, likely depending on differences in vegetation and soil water availability. We also found distinct microbial communities for soils from low-center polygons, possibly driven by prevailing anoxic conditions in this landscape unit. Bacterial and archaeal communities differed among all soil layers, while only fungal communities from the organic soils differed from the other layers.The observed differences in SOM and microbial community composition among soil layers and polygon types highlight the importance of considering spatial heterogeneity when studying permafrost soils. Moreover, our results might help to explain observed differences in microbial decomposition patterns on different spatial scales and emphasize the need to include aspects of permafrost soil heterogeneity to finetune current ecosystem and climate models.This study is part of the EU H2020 project “Nunataryuk”.

The extensive work in AMAP on Arctic contamination by Persistent Organic Pollutants (POPs) illustrates the strong state of knowledge and data on contaminants in biota and water, but also highlights a stark data gap regarding contaminants in Arctic soils, particularly below the permafrost table. Here, we describe the work carried out on analyses and scaling of contaminants. A key aspect for being able to deliver geospatial databases is identifying which landscape properties we can use to scale the measured contaminant levels. Soils in the Canadian study area at Komakuk Beach (Yukon, CA) have been sampled and analysed for hexachlorobenzene (HCB), 54 polychlorinated biphenyl congeners (PCBs) and 22 individual polycyclic aromatic hydrocarbons (PAHs) in 89 active layer and permafrost core samples. The concentrations have been determined by using Thermo Scientific Dionex ASE 350 and Trace 1310 GC coupled with TSQ9000 TQMS, Thermo Scientific, at CNR-ISP Venice, Italy. The statistical parameters of data on HCB concentrations describe its scarce presence, with limited occurrences linked to the organic rich soil horizons. Overall, Σ54PCBs in soils collected in the catchment area were in the range from 0 to 5.33 pg/g. Both the content of individual PAHs and their total concentration vary widely from 0 to 121ng/g. The contribution of individual PAHs to the total amount is not the same and depends on the concentration of heavy 5–6-nuclear polyarenes and mainly 6-nuclear benzo[ghi]perylene. Our results show that the vertical distribution patterns of light 2–4-nuclear and heavy 5–6-nuclear PAHs are differentiated. Every class of OC is present in the deeper permafrost core portions only in High Centre Polygon (HCP) landform class, highlighting the role of hydrology and percolation in the contaminant distribution in permafrost soils and how these variables are enhanced in (semi-)degraded permafrost landforms. The model equations have been applied on the carbon content prediction maps for each study area, to export a first attempt of upscaling feasible for small coastal catchments in polygonal tundra environment. Contaminant concentrations ranges were calculated for different depth from 0 to 1 meter below the ground, following the carbon content prediction maps from Wagner et al. (sub.)

Climate change threatens the Earth’s biggest terrestrial organic carbon reservoir: permafrost soils. With climate warming, frozen soil organic matter may thaw and become available for microbial decomposition and subsequent greenhouse gas emissions. Permafrost soils are extremely heterogenous within the soil profile and between landforms. This heterogeneity in environmental conditions, carbon content and soil organic matter composition, potentially leads to different microbial communities with different responses to warming. The aim of the present study is to (1) elucidate these differences in microbial community compositions and (2) investigate how these communities react to warming.We performed short-term warming experiments with permafrost soil organic matter from northwestern Canada. We compared two sites characterized by different glacial histories (Laurentide Ice Sheet cover during LGM and without glaciation), three landscape types (low-center, flat-center, high-center polygons) and four different soil horizons (organic topsoil layer, mineral topsoil layer, cryoturbated soil layer, and the upper permanently frozen soil layer). We incubated aliquots of all soil samples at 4 °C and at 14 °C for 8 weeks and analyzed microbial community compositions (amplicon sequencing of 16S rRNA gene and ITS1 region) before and after the incubation, comparing them to microbial growth, microbial respiration, microbial biomass and soil organic matter composition.We found distinct bacterial, archaeal and fungal communities for soils of different glaciation history, polygon types and for different soil layers. Communities of low-center polygons differ from high-center and flat-center polygons in bacterial, archaeal and fungal community compositions, while communities of organic soil layers are significantly different from all other horizons. Interestingly, permanently frozen soil layers differ from all other horizons in bacterial and archaeal, but not fungal community composition.The 8-week incubations led to minor shifts in bacterial and archaeal community composition between initial soils and those subjected to 14 °C warming. We also found a strong warming effect on the community compositions in some of the extreme habitats: microbial community compositions of (i) the upper permanently frozen layer and of (ii) low-center polygons differ significantly for incubations at 4 °C and 14 °C. Yet, the lack of a community change in horizons of the active layer suggests that microbes are adapted to fluctuating temperatures due to seasonal thaw events.Our results suggest that warming responses of permafrost soil organic matter, if not frozen or water-saturated, may be predictable by current models. Process changes induced by short-term warming can be rather attributed to changes in microbial physiology than community composition.This work is part of the EU H2020 project “Nunataryuk”.

Recent decades have shown phases of very rapid warming in the Canadian Arctic. This raises a concern, also in reference to potential changes in permafrost active layer deepening, enhancing the fact that seawater, snow and soils are becoming important secondary sources remobilizing persistent organic pollutants (POPs). This work investigates the potential influence of permafrost on POPs distribution in the soils of two small coastal catchments at the Canadian Beaufort coast. One catchment is located south of Herschel Island on the mainland and was covered by the Laurentide ice sheet during the last glacial maximum (LGM), the second catchment is located westerly at Komakuk Beach and was ice-free during the LGM.Soils were sampled by horizon in the Active Layer from an open soil pit and by coring into the permafrost, near the top of the permafrost table and at 90 cm depth from the soil surface (99 samples form Ptarmigan Bay and 89 from Komakuk Beach). The total sampling depth was 1,0 m (including Active Layer and Permafrost). A random distribution of the points over the areas guaranteed the sampling over different Landforms, aiming to understand the contaminant concentration and distribution. Quantification of PAHs, PCBs, HCB was performed using GC-MS technique, a 7890A gas chromatographer coupled with a 5975C MSD System, Agilent Technologies, at CNR-ISP Venice, Italy.Preliminary results confirm that the mechanism responsible for the transport of POPs into the soil are believed to be gravity drainage and capillary suction into fissures and cracks. An accumulation of PAHs has been detected in the permafrost transient layer. It is probably related, as demonstrate in literature, to the accumulation and transport of soil organic carbon influence, as well as the changing in hydraulic barriers. The role of cryoturbation in the vertical transport and accumulation of POPs is also considered and discussed.The study has been conducted thanks to Grant Agreement number: 773421 — Nunataryuk — H2020-BG-2016-2017/H2020-BG-2017-1 ‘Permafrost thaw and the changing arctic coast: science for socio-economic adaptation — Nunataryuk’

We present the results obtained using an original open-source low-cost sensor (LCS) system developed to measure tropospheric O3 in a remote high altitude alpine site. We conducted our study at the Col Margherita Observatory (2543 m a.s.l.), a World Meteorological Organization Global Atmosphere Watch Regional Station (WIGOS Id: 0-380-0-MRG), located in the Italian Eastern Alps. The sensing system mounts three equivalent commercial low-cost sensors that have been calibrated using a laboratory standard (Thermo 49iPS), referenced to the Standard Reference Photometer #15 calibration scale by the WMO, before field deployment. Intra and inter-comparison between sensors and reference (Thermo 49c) have been conducted for six months from May to December 2018. The sensor’s dependence on the environmental meteorological variables has been considered and discussed. The evaluation of the analytical performances of this sensing system provides a limit of detection < 5 ppb, limit of quantitation < 17 ppb, linear dynamic range up to 250 ppb, intra-Pearson correlation coefficient (PCC) up to 0.96, inter-PCC > 0.8, bias > 3.5 ppb and ±8.5 at 95% of confidence. Thanks to the first implementation of an LCS System in an alpine site, we demonstrated how it is possible to obtain valuable data from a low-cost instrument in a remote harsh environment. This opens new perspectives for the adoption of a low-cost sensor network in atmospheric sciences. We further present our recent experience using LoRa to integrate the sensing system into a low-power wide-area network (LPWAN). We developed an end-node and a gateway, designing PCBs derived from the Arduino Mega, optimizing their power consumption and equipping them with batteries, a proper solar panel or wind turbine to ensure their autonomy while collecting environmental ozone and meteorological (T, RH, WS, WD) data. We drafted the communication software to send compressed data from end-nodes to gateways. The gateways are part of an openVPN with the main server located in Venice. The server also provides a postgreSQL database and a R-shiny web application for data visualization and manipulation. To enhance redundancy, the local data are also synchronized to a cloud database. In the next years, thanks to the Marie Skłodowska-Curie grant PIONEER, we will exploit our experiences to provide a comprehensive low-cost wireless sensor network to characterize transport of polluted air masses and provide long term climate data collection in support of the state-of-the-art instrumentation and established networks in remote alpine areas.BibliographyDallo F. et al.: Calibration and assessment of electrochemical low-cost sensors in remote alpine harsh environments, Atmospheric Measurement Techniques, amt-2020-483. In reviewAcknowledgements. This work was part of the Arctic Field Grant O3NET project, funded by the Research Council of Norway. The work received financial support by the National Project of Interest Next-Data (MIUR). The exploitation of the LoRa technology was performed with the ITIS "Max Planck" through the Remote Observatory SYstem (ROSY) "Alternanza scuola-lavoro" project. This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 844526

Arctic ecosystems outpace the global rate of temperature increases and are exceptionally susceptible to global warming. Concerns are raising that CO2 and CH4 released from thawing permafrost upon warming may induce a positive feedback to climate change. This is based on the assumption, that microbial activity increases with warming and does not acclimate over time. However, we lack a mechanistic understanding of carbon and nutrient fluxes including their spatial control in the very heterogeneous Arctic landscape. The objective of this study therefore was to elucidate the microbial controls over soil organic matter decomposition in different horizons of the active layer and upper permafrost. We investigated different landscape units (high-centre polygons, low-centre polygons and flat polygon tundra) in two small catchments that differ in glacial history, at the Yukon coast, Northwestern Canada.In total, 81 soil samples were subjected to short-term (eight weeks) incubation experiments at controlled temperature (4 °C and 14 °C) and moisture conditions. Heterotrophic respiration was assessed weekly, whereas physiological parameters of soil microbes and their temperature response (Q10) were determined at the end of the incubation period. Microbial growth was estimated by measuring the incorporation of 18O from labelled water into DNA and used to calculate microbial carbon use efficiencies (CUE). Microbial biomass was determined via chloroform fumigation extraction. Potential activities of extracellular enzymes involved in C, N, P and S cycling were measured using microplate fluorimetric assays.Cumulative heterotrophic respiration of investigated soil layers followed the pattern organic layers > upper frozen permafrost > cryoturbated material > mineral layers in both catchments. Microbial respiration responded strongly in all soils to warming in all soils, but the observed response was highest for organic layers and cryoturbated material at the beginning and end of the experiment. Average Q10 values at the beginning of the experiment varied between 1.7 to 4.3 with differences between horizons but converged towards Q10 values between 2.0min to 2.9max after eight weeks of incubation. Even though microbial biomass C did not change with warming, microbial mass specific growth was enhanced in organic, cryoturbated and permafrost soils. Overall, warming resulted in a 65% reduced CUE in organic horizons.Our results show no indication for physiological acclimatization of permafrost soil microbes when subjected to 8-weeks of experimental warming. Given that the duration of the season in which most horizons are unfrozen is rarely longer than 2 months, our results do not support an acclimation of microbial activity under natural conditions. Instead, our data supports the current view of a high potential for prolonged carbon losses from tundra soils with warming by enhanced microbial activity.This work is part of the EU H2020 project “Nunataryuk”.

Ongoing climate warming in the western Canadian Arctic is leading to thawing of permafrost soils and subsequent mobilization of its organic matter (OM) pool. Part of this mobilized terrestrial OM enters the aquatic system as dissolved organic matter (DOM) and is laterally transported from land to sea. Mobilized DOM is an important source of nutrients for ecosystems as it is available for microbial breakdown, the consequent turnover of the dissolved organic carbon (DOC) fraction of DOM serving as a potential source of greenhouse gases. We are beginning to understand spatial controls on the release of DOM as well as the quantities and fate of this material in large arctic rivers, but these processes remain systematically understudied in small, high-arctic watersheds, despite the fact that these particular watersheds experience strongest warming.We sampled soil (active layer and permafrost) and water (porewater and stream water) from two small catchments along the Yukon coast, Canada, during the summers of 2018 and 2019. We assessed the organic carbon quantity (using DOC and soil OC content), quality (d13C-DOC, C/N ratios and optical properties including components modelled with EEMs-PARAFAC), the turnover of DOM through incubation experiments as well as nutrients and stable water isotopes. We classify and compare different landscape units by quantitative and qualitative change across gradients from soil stocks down to the catchment outflow.Our results show that substantial variation in DOC concentrations exists among various landscape units as well as between active layer and permafrost. We find high soil carbon stocks and leaching potentials from these coastal tundra soils. Moreover, we find that permafrost DOM is utilized rapidly upon thaw. Using remote sensing-based landscape classification, we are planning to upscale carbon and nutrient fluxes for the panarctic coastal zone to account for small yet numerous high-arctic watersheds in lateral terrestrial OM transfer from land to sea Under current climate projections and with continued permafrost thaw altered lateral fluxes may have profound impacts on the arctic aquatic ecosystem and arctic carbon cycling.

In several areas of the world, water distribution and quality influence the local development; moreover water sometimes exceeds the World Health Organisation (WHO) drinking water limits, even if anthropogenic contamination is not present. As example, in the Main Ethiopian Rift Valley water distribution influences agriculture and breeding, as well as high concentration of many chemical elements should have a consequence on human health. The present study, carried out by the Department of Earth Science of the University of Turin in cooperation with LVIA, allowed a better understanding of the main hydrochemical features and groundwater distribution in the south-centre of the Main Ethiopian Rift Valley (MER). The research consisted in a census of the main water point (springs and wells) in the District of Shashemene, Arsi Negelle and Siraro; each of them have been examined with field instruments so that main physical features of the water and fluoride content have been defined.

Ongoing climate warming in the western Canadian Arctic is leading to thawing of permafrost soils and subsequent mobilization of its organic matter pool. Part of this mobilized terrestrial organic matter enters the aquatic system as dissolved organic matter (DOM) and is laterally transported from land to sea. Mobilized organic matter is an important source of nutrients for ecosystems, as it is available for microbial breakdown, and thus a source of greenhouse gases. We are beginning to understand spatial controls on the release of DOM as well as the quantities and fate of this material in large Arctic rivers. Yet, these processes remain systematically understudied in small, high-Arctic watersheds, despite the fact that these watersheds experience the strongest warming rates in comparison. Here, we sampled soil (active layer and permafrost) and water (porewater and stream water) from a small ice wedge polygon (IWP) catchment along the Yukon coast, Canada, during the summer of 2018. We assessed the organic carbon (OC) quantity (using dissolved (DOC) and particulate OC (POC) concentrations and soil OC content), quality (δ13C DOC, optical properties and source apportionment) and bioavailability (incubations; optical indices such as slope ratio, Sr; and humification index, HIX) along with stream water properties (temperature, T; pH; electrical conductivity, EC; and water isotopes). We classify and compare different landscape units and their soil horizons that differ in microtopography and hydrological connectivity, giving rise to differences in drainage capacity. Our results show that porewater DOC concentrations and yield reflect drainage patterns and waterlogged conditions in the watershed. DOC yield (in mg DOC g−1 soil OC) generally increases with depth but shows a large variability near the transition zone (around the permafrost table). Active-layer porewater DOC generally is more labile than permafrost DOC, due to various reasons (heterogeneity, presence of a paleo-active-layer and sampling strategies). Despite these differences, the very long transport times of porewater DOC indicate that substantial processing occurs in soils prior to release into streams. Within the stream, DOC strongly dominates over POC, illustrated by DOC/POC ratios around 50, yet storm events decrease that ratio to around 5. Source apportionment of stream DOC suggests a contribution of around 50 % from permafrost/deep-active-layer OC, which contrasts with patterns observed in large Arctic rivers (12 ± 8 %; Wild et al., 2019). Our 10 d monitoring period demonstrated temporal DOC patterns on multiple scales (i.e., diurnal patterns, storm events and longer-term trends), underlining the need for high-resolution long-term monitoring. First estimates of Black Creek annual DOC (8.2 ± 6.4 t DOC yr−1) and POC (0.21 ± 0.20 t yr−1) export allowed us to make a rough upscaling towards the entire Yukon Coastal Plain (34.51 ± 2.7 kt DOC yr−1 and 8.93 ± 8.5 kt POC yr−1). Rising Arctic temperatures, increases in runoff, soil organic matter (OM) leaching, permafrost thawing and primary production are likely to increase the net lateral OC flux. Consequently, altered lateral fluxes may have strong impacts on Arctic aquatic ecosystems and Arctic carbon cycling.