Resolving the origin and flowpaths of meltwaters in Arctic glacierized catchments, beyond the traditional atmospheric versus water-rock framework, is crucial for understanding how weathering processes evolve with glacier retreat and regulate solute export. We investigated the hydrochemistry and isotopic composition of glacial meltwaters and proglacial streams in the Kongsfjorden region (Svalbard), integrating major ions and stable water isotopes with coupled 87Sr/86Sr and δ11B analyses during the early melt season. Major ion systematics reveal a dominant marine aerosol imprint, indicating that early meltwater chemistry is largely controlled by snowpack flushing of sea-spray deposits accumulated in the winter snowpack. Strong Na–Cl correlations and B/Na ratios close to those of seawater support this interpretation. Nevertheless, sea-salt corrections and isotopic tracers demonstrate measurable crustal contributions. Radiogenic 87Sr/86Sr values (>0.720 in the Midtre Lovénbreen and Kongsvegen basins) cannot be explained by marine input or carbonate dissolution alone and instead require interaction with rubidium (Rb)-rich siliciclastic or metamorphic lithologies. Boron isotopes further constrain the relative contribution of these sources, with estimated marine B fractions ranging from approximately 30%–80% across catchments. Coupled 87Sr/86Sr–δ11B isotope systematics identify mixing between a marine aerosol component and at least two crustal end-members (carbonate and metamorphic/siliciclastic), highlighting glacier-specific differences linked to hydrological routing and local geology. Our results show that the combined use of Sr and B isotopes provides a powerful geochemical framework to disentangle atmospheric marine inputs from crustal weathering processes in Arctic glacial meltwaters. They further indicate that, even under early melt-season conditions dominated by snowpack flushing, water–rock interaction still modulates meltwater chemistry. This study represents the first application of δ11B isotopes to Arctic glacial and proglacial waters and one of the few investigations employing Sr isotopes in Arctic continental meltwater systems. The integrated 87Sr/86Sr–δ11B framework provides a robust isotopic baseline for assessing evolving weathering regimes and solute export pathways in rapidly changing polar environments.

Geothermal energy represents an important aspect of the ongoing green transition; therefore, geothermal reservoirs have to be properly investigated and studied in many and different aspects. In this frame, the Larderello geothermal field represents an important energy resource for the Tuscan region, and the first geothermal reservoir to be used for energy production. It is a vapor-dominated reservoir producing superheated steam and characterized by areas where the permeable formations of the shallower reservoir outcrops, with thermal manifestations at the surface, such as fumaroles and steaming-ground. In particular, the Le Biancane area, one of the main outcropping zones, represents a potential recharge point where meteoric water can infiltrate through the carbonate-anhydrite formations of the Tuscan Nappe. Although the Larderello geothermal system has been studied since the beginning of the last century, a detailed and systematic investigation of the recharge in the infiltration potential areas is still missing. Indeed, only few chemical and isotopic data of meteoric waters and geothermal fluids in the Le Biancane area are available. These are not enough to give information on the main infiltration areas and origin of the geothermal fluids, considering also the re-injection of spent fluids that has been introduced since the ’70 in some of the wells. Therefore, with the aim to analyse in detail the recharge in the Le Biancane area, 11 fumaroles and 37 cold and thermal springs were sampled. In order to be able to well define the isotopic marker of this area, the investigated springs were selected on a wider area surrounding Le Biancane, on a regional scale. Two sampling campaigns have been carried out, one after the rainy season in May/June 2023 and one after the dry season in October 2023. From isotopic analyses on fumarole condensates, differences in δD and δ18O were evident highlighting the possibility that these fluids undergo different processes before reaching the surface. Furthermore, fumaroles were analysed, among the many components, also for COS, which represents a new potential geo-indicator. On the other hand, regarding the water recharge investigation, in this work we will present the results of the isotopic hydrological approach on the spring samples.

We evaluated the geothermal resources of Vulcano Island considering the available geological, geochemical, and geophysical information in the framework of the conceptual model of La Fossa magmatic-geothermal system. Having ascertained that the shallow groundwaters of the Vulcano Porto plain are heated by geothermal steam and gases and are not directly impacted by magmatic fluids, we have adopted the CO2Pand temperature distribution in these shallow groundwaters to delimit the areal extension of the underlying geothermal aquifer, which is 0.777 km2 and 0.752 km2 based on the CO2Pand temperature maps respectively, in agreement with the area from MT data, 0.7 km2. The revised volume method was used considering the specific productivity of liquid-dominated geothermal systems, 40 t center dot h-1 center dot km-3, and assuming that the geothermal aquifer has a thickness of 2.8 km and a temperature of 200-275 degrees C. The hourly production rate of geothermal fluids resulted to be in the range 84.2-87.0 t center dot h-1, while the extractable thermal and electrical powers turned out to be 25 +/- 6(1 sigma) MWt and 8.3 +/- 2.0 MWe, respectively. Drilling of one or two production wells and one reinjection well (depth in the order of 1.5-2.0 km) could be therefore a suitable technical solution.

The use of a conceptual model of reference and modelling of relevant processes is mandatory to correctly interpret chemical and isotopic data. Adopting these basic guidelines, we have interpretated the unprecedented increase in the H2S(g) concentration and the concurrent unexpected decrease in the δ34S value of H2S(g) recorded since 2018 in the fumarolic effluents of the Bocca Grande fumarolic vent at Solfatara, Campi Flegrei caldera, in the framework of our conceptual model of the Solfatara magmatic–hydrothermal system. Assuming that the magma chamber situated at depths ≥ 8 km was filled at the end of the 1982–1984 bradyseismic crisis and no refilling episodes took place afterwards, as suggested by gas geochemistry, the concentration and the δ34S value of H2S(g) of the Bocca Grande fumarolic effluents are controlled by closed-system degassing of the melt at depths ≥ 8 km and disproportionation of SO2 in the deep hydrothermal reservoir (6.5–7.5 km depth) hosted in carbonate rocks where H2S equilibrates. These processes have been active during the last 40 years, but 41.1% (±6.4%) of the sulfur initially stored in the melt (2200 mg/kg) was lost in the 4-year period of April 2018–April 2022. This marked loss of S from the melt in 2018–2022 might be due to the high solubility of sulfur in the melt, which caused its preferential separation during the late degassing stages. These findings are of utmost importance for the surveillance of the Solfatara magmatic–hydrothermal system during the ongoing bradyseismic crisis.

Abstract. We revised the conceptual model of the Solfatara magmatic-hydrothermal system based on the results of new gas-geoindicators (Marini et al., 2022) and the available geological, volcanological, and geophysical information from surface surveys and deep geothermal wells. Using the new gas-geoindicators, we monitored the temperature and total fluid pressure over a time interval of ~40 years: (i) in the shallow reservoir (0.25–0.45 km depth), where CO equilibrates; (ii) in the intermediate reservoir (2.7–4.0 km depth), where CH4 attains equilibrium; (iii) in the deep reservoir (6.5–7.5 km depth), where H2S achieves equilibrium. From 1983 to 2022, the temperature and total fluid pressure of the shallow reservoir did not depart significantly from ~220 °C and ~25 bar, whereas remarkable, progressive increments in temperature and total fluid pressure occurred in the intermediate and deep reservoirs, with peak values of 590–620 °C and 1200–1400 bar in the intermediate reservoir and 1010–1040 °C and 3000–3200 bar in the deep reservoir, in 2020. The revised conceptual model allowed us to explain the evolution of: (a) pressurization-depressurization in the intermediate reservoir, acting as the “engine” of bradyseism, (b) time changes of total fluid pressure in the deep reservoir, working as the “on-off switch” of magmatic degassing. We also used the revised conceptual model to predict possible future scenarios in the lack of external factors.

Silicic caldera volcanoes present major volcanic and seismic hazards but also host dynamic hydrothermal and groundwater systems and a rich but largely unexplored subsurface biosphere. Many of these volcanoes are hosted in rift settings. The intricate connections and feedbacks among magmatism, rifting, hydrothermal processes, and the biosphere in these complex systems remain poorly understood, necessitating subsurface joint observations that are only enabled by scientific drilling. The CALDERA (Connections Among Life, geo-Dynamics and Eruptions in a Rifting Arc caldera) project workshop funded by the International Continental Scientific Drilling Program (ICDP) gathered multi-disciplinary international experts in January 2023 to advance planning of a scientific drilling project within one of these dynamic, rift-hosted calderas, the Okataina Volcanic Centre (OVC), Aotearoa New Zealand. The OVC's high eruption rate, frequent unrest events and earthquake swarms, location in a densely faulted rapidly extending rift, abundant groundwater–geothermal fluid circulations, and diverse surface hot spring microbiota make it an ideal location for exploring a connected geo-hydro-biosphere via scientific drilling and developing a test bed for novel volcano monitoring approaches. Drilling configurations with at least two boreholes (∼ 200 and ∼ 1000–1500 m deep) were favoured to achieve the multi-disciplinary objectives of the CALDERA project. Decadal monitoring including biosphere activity and composition has the potential to evaluate the response of the hydro-bio system to volcano-tectonic activity. In addition to the OVC caldera-scale datasets already available, site surveys will be conducted to select the best drilling locations. The CALDERA project at the OVC would provide, for the first time, an understanding of volcanic–tectonic–hydrological–biological connections in a caldera–rift system and a baseline for global comparisons with other volcanoes, rifts, and hydrothermal systems. CALDERA would serve as an unprecedented model system to understand how and how quickly the subsurface biosphere responds to geologic activities. Discoveries will improve assessment of volcanic and seismic hazards, guide the sustainable management and/or conservation of groundwater and geothermal resources and microbial ecosystems, and provide a forum for interweaving mātauranga Māori and Western knowledge systems.

The origin of methane in hydrothermal fluids has long been a subject of debate – whether it is abiotic or biotic. In this study, we aim to unravel and quantify the sources of CH4 in active hydrothermal systems by adopting a holistic approach analyzing well characterized high-temperature hydrothermal fluids (∼230–310 °C) in Iceland. We employ a broad variety of geochemical and isotope indicators, encompassing chemical and isotope compositions of the targeted fluids. These signatures are then compared with results from chemical and isotope kinetic models and data from sedimentary-hosted hydrothermal systems. Carbon species in these fluids include CO2 (2.60–184 mmol/kg), CH4 (2.39·10−4–0.325 mmol/kg), dissolved organic carbon (4.78·10−3–0.112 mmol/kg), and CO (1.89·10−6–4.16·10−4 mmol/kg). Carbon and helium isotopes suggest a relatively uniform mantle-derived source of CO2 (δ13C-CO2: −4.80 to −1.50 ‰, CO2/3He: 1.49·109–4.14·1010 14C-CO2: 0.11–2.42 pMC). Methane, in contrast, has multiple sources. Overall, chemical equilibria among carbon species (CO2, CH4, CO) is not attained, suggesting kinetic controls. Tritium content (<0.8–1.42 TU) and hydrologic constraints indicate relatively short hydrothermal fluid residence times (∼5–200 years), with occasional inputs from older water components. Within this short timeframe, CH4 concentrations vary from lower, to significantly higher than those calculated using CO2 reduction kinetics. The isotope composition (δD-CH4: −172 to −138 ‰, δ13C-CH4: −32.0 to −24.6 ‰; 14C-CH4: 0.36–11.54 pMC) and geochemical and isotope modeling suggest that the majority (>80–90 %) of CH4 originates from a radiocarbon inactive source, i.e. mantle CH4, reduction of mantle CO2 and/or old organic matter, with relatively small contributions from both marine (<20 %) and terrestrial (<10 %) dissolved organic carbon. Measured isotopic compositions of CH4 do not match those expected for mantle-derived CH4 as well as values generated from reduction of mantle-derived CO2. Instead, differences in δD-CH4 and δ13C-CH4 values exist between systems fed by meteoric water and those fed by seawater, challenging the assumption of a uniform CO2 source and invariable reaction mechanisms. Differences between systems are best explained by variable extent of thermal decomposition and primary variations in the isotope composition of marine and terrestrial organic matter. Also, δD-CH4 and δ13C-CH4 values in meteoric water-fed systems closely resemble those in the Öxarfjördur sedimentary-hosted systems. In summary, our data supports a predominant thermogenic origin of CH4 in both seawater and terrestrial hydrothermal fluids in Iceland. The source of organic matter appears to be a combination of modern dissolved organic carbon and older sedimentary deposits. In addition, some of the hydrothermal systems studied (Krafla, Reykjanes, Theistareykir) which are characterized by low CH4 concentrations, may contain a significant portion of CH4 that may originate from CO2 reduction.

&lt;p&gt;Surface water and groundwater are changing rapidly because of significant climate warming in the Arctic region [1,2]. Arctic amplification has intensified the melting of snow cover and glaciers, as well as widespread permafrost degradation, leading to a prominently increase of the annual discharge of some Arctic rivers [3,4]. This results in dramatic impacts on the surface water transition and freshwater circulation that, in turn, can cause localized permafrost thaw [5], allowing greater connection between deep groundwater and surface water pathways. Groundwater is a crucial component of the hydrological cycle, affecting ecosystems and human communities in Arctic regions.&lt;/p&gt; &lt;p&gt;In high-latitude regions, evaluating groundwater flux and storage and river discharge is challenging due to a lack of trusted and publicly available hydrogeological data. Changes in river flows and groundwater discharge will alter fluxes of freshwater and terrigenous material (e.g., sediment, nutrients, and carbon), with implications for biodiversity in both freshwater and marine ecosystems. The rapid glacier melting affects weathering processes, resulting in the mobilization-transport of pollutants, microorganisms stored for a long time, and turbid meltwaters. Consequently, more timely and accurate evaluation of surface and groundwater is urgently required.&lt;/p&gt; &lt;p&gt;Thanks to its geographical characteristics, the retreating glaciers, the research stations and infrastructures, and the studies carried out in the past and present, the Bayelva catchment near Ny-&amp;#197;lesund (Western Svalbard-Norway) is an ideal site for surveys aimed at increasing knowledge on hydrology dynamics and associated effects, in the continuum from glaciers to the fjord.&lt;/p&gt; &lt;p&gt;In this framework, within the ICEtoFLUX project (MUR/PRA2021 project-0027) field campaigns were conducted in the spring and summer of 2022 in the Bayelva River catchment, from its glaciers and periglacial/proglacial systems up to the Kongsfjorden sector significantly affected by the river.&amp;#160; The activities were aimed at quantifying hydrologic processes and related transport of pollutants and microbial biomass and activities. Suprapermafrost groundwater was monitored by four piezometers installed along a hillslope to investigate how subsurface and surface waters interact during active layer development.&lt;/p&gt; &lt;p&gt;Water samples were repeatedly collected for analysing physical-chemical-isotopic-biological parameters. Main rain events and monthly total precipitation were sampled for stable isotopes.&lt;/p&gt; &lt;p&gt;The first results suggest that, in general, electrical conductivity and total suspended solids increase from the glacier to the Bayelva monitoring station, which is located less than 1 km far from the coast. Seasonal evolution of physical-chemical features was also observed. Results from piezometers indicate that the underground flow is spatially and temporally heterogeneous, both quantitatively and from a physical-chemical-isotopic-biological point of view. A general increase of electrical conductivity over the melt season was registered for groundwater and streamwater. First evidence on organic pollutants and microbe transport are also discussed.&lt;/p&gt; &lt;p&gt;[1] Fichot, C.G. et al. 2013. Sci. Rep., 3, 1053.&lt;/p&gt; &lt;p&gt;[2] Morison, J. et al. 2012. Nature, 481, 66&amp;#8211;70.&lt;/p&gt; &lt;p&gt;[3] McClelland, J.W. et al. 2006. Geophys. Res. Lett., 33, L06715.&lt;/p&gt; &lt;p&gt;[4] Wang, P. et al. 2021. Res. Lett., 16, 034046.&lt;/p&gt; &lt;p&gt;[5] Zheng, L. et al. 2019. J. Geophys. Res. Earth Surf., 124, 2324&amp;#8211;2344.&lt;/p&gt;

The natural park of Le Biancane is located in the southern sector of the Larderello-Travale geothermal field (LTGF). It extends over an approximately 100,000 m2 area where the impermeable caprock is locally absent and deep fluids may directly reach the surface. Through a multidisciplinary approach including measurements of soil CO2 flux (total output of 11.5 t day-1), soil temperature (average 34.4 degrees C), stable isotope and chemical data on fluids from fumaroles (dominated by a mixture of geothermal gases and air or gases from air-saturated meteoric water), and structural analysis of the formation outcropping, we found that anomalous CO2 emissions are positively correlated with shallow temperature anomalies. These are in restricted locations adjacent to vents and fumaroles, where a network of well-connected fractures (preferentially NW-SE and NE-SW orientated and with steep dips) drains efficiently allowing upward migration of the deep fluids and the energy toward the surface.

Non-steady-state closed dynamic accumulation chambers are widely used to measure the respiration of terrestrial ecosystems, thanks to their low cost, low energy consumption and simple transportability, that allow measurements even in hostile and remote environments. However, the assessment of the accuracy and precision associated with the measurement system (independently of possible disturbances due to chamber-soil interactions) is rarely reported. This information is instead necessary for basic quality control, to compare data obtained by different devices and regression models and to provide Confidence Intervals (CIs) on the carbon flux values. This study quantifies the uncertainty associated with emission flux measurements, with a focus on very low fluxes. Calibration tests using different accumulation chambers and CO 2 sensors were performed, and fluxes were calculated by means of different models (parametric, non-parametric and flux models). The results of this work show that the linear regression model has the best reproducibility when compared to the other tested models, regardless of the sensor used and the chamber volumes, while the second order polynomial regression has the best accuracy. We remark the importance of building a calibration curve in the range of the expected flux values, with an interval between the lowest and highest imposed flux that should not exceed two orders of magnitude. To evaluate the reproducibility of the measurement, performing replicates for each imposed flux value is essential. We also show that it is necessary to carefully identify the best time interval for interpolating the CO 2 concentration curve in order to guarantee reproducibility and accuracy in flux estimates.

Volcanic and/or geothermal gases provide essential information on the activity of a volcanic system, on magma degassing and on the origin and evolution of fluids. Their study represents one of the most powerful technique to understand the dynamics of systems and to monitor the volcanic activity (dormant state, but also unrest and/or eruption phase). Volcanic/geothermal gases are complex mix of chemical elements and compounds. Starting from the study of their chemical composition, many equilibrium reactions in gas phase were introduced in the past as possible geothermometers and geobarometers, and they actually used to estimate the thermodynamic conditions in deep system (both in volcanic or geothermal area) and in volcanic surveillance. However, depending on the system, known geothermal-barometric reactions are not able to accurately describe the thermodynamic conditions of reservoirs, highlighting the need for new geothermometric reactions. Of course, the opportunity to develop new “geothermometers/geobarometers functions” depends to the availability of analytical techniques able to detect and quantify new chemical compounds of interest, often at low to very low concentration levels (ppb). The GC-ICP-MS (gas chromatography-inductively coupled plasma-mass spectrometry), one of the most useful hyphenated method (Michalski R. et al., 2006; Easter R.N. et al., 2010), combines the high separation capacity of the GC with the high sensitivity and specificity of the ICP-MS. Chemical compounds containing C, S and O are abundant in volcanic/geothermal gases and they can be detected at low levels via GC-ICP-MS technique. The development of new specific analytical methods for volcanic/geothermal gas analysis (in particular for what concern new compounds) may provide the chance to introduce new gas equilibrium as a “key” to better understand thermodynamic and redox conditions at depth. Dry gas samples from fumaroles of the La Solfatara di Pozzuoli (Bocca Grande, Bocca Nuova and Pisciarelli) and for crater area in the Vulcano island were analysed, studying the distribution of sulphur-bearing species. The results obtained are very satisfactory in terms of chromatographic separation and detection limits, making the GC-ICP-MS method very promising in the study of volcanic/geothermal gases.

The Bocca Grande and Bocca Nuova fumaroles have mean outlet temperatures of 161.4°C and 145.4°C, respectively, indicating that they discharge superheated (dry) gas mixtures. Water (688,900 to 873,100 μmol/mol) and CO2 (125,000 to 308,700 μmol/mol) constitute together 99.3 to 100 mol % of these fluids, which can be considered binary CO2-H2O gas mixtures to a first approximation. Therefore, first of all, the main characteristics of the binary CO2-H2O system were summarized in this chapter. Although a general review of the equations of state (EOS) is beyond the scope of this book, an excursus on this topic was deemed necessary to contextualize the three distinct approaches adopted to evaluate the deviations from the ideal gas behavior of H2O and CO2 as well as the effects of steam condensation during the isenthalpic expansion of Bocca Grande and Bocca Nuova fluids, namely, the EOS of Gallagher et al. (1993), the GERG-2008 EOS together with the virial EOS, and the Peng-Robinson EOS. It turned out that deviations from ideality cannot be neglected at temperatures higher than 195-210°C and pressures greater than 15-30 bar approximately. The Peng-Robinson EOS was also used to compute the fugacity coefficients not only of H2O and CO2 but also of H2, CH4, and CO in the gas mixtures with CO2 mole fraction of 0.05, 0.10, 0.20, 0.30, and 0.40. Calculations were performed separately for the ternary mixtures H2O-CO2-H2, H2O-CO2-CH4, and H2O-CO2-CO, adopting the mean concentrations of H2, CH4, and CO of Solfatara fumarolic fluids and computing the H2O mole fraction by difference to unity. Fugacity coefficients were calculated (i) at the P,T conditions of the isenthalpic expansion path, (ii) at the P,T conditions fixed by coexistence of the vapor phase with a brine containing either 21 wt% or 33.5 wt% NaCl, and (iii) for the linear P-T decompression path, that is, assuming that total fluid pressure and temperature increase linearly from the critical point of water to the values of the magmatic endmember M1 of Caliro et al. (2014), 2879 bar and 1120°C. In all these decompression paths, the fugacity coefficients of non-polar gases increase with increasing P,T deviating gradually from unity, whereas the fugacity coefficient of H2O decreases with increasing P,T, departing progressively from one. The ensuing practical implication is that the analytical mole fraction ratios of carbon gases may be utilized in geothermometric-geobarometric functions without incurring excessive errors, whereas use of the analytical H2/H2O mole fraction ratio leads to significant errors in computed equilibrium temperatures and pressures. ■■■

Deviations from ideality were considered to implement an H2S-H2 geothermometer and three different H2S-H2-H2O geothermometers based on the heterogeneous gas-solid equilibria involving pyrite-pyrrhotite, pyrite-fayalite-quartz, pyrite-magnetite, and pyrite-hematite. The results obtained by using these geothermometers suggest that the H2S concentration of Solfatara fluids is probably controlled by other reactions. Therefore, two distinct heterogeneous gas-solid equilibria comprising anhydrite and calcite were utilized to develop a H2S-CO2 geothermometer (also involving H2 and H2O) and a H2S-CH4 geothermometer (also including H2O), again considering the fugacity coefficients of relevant gas species. The computed H2S-CO2 equilibrium temperatures and pressures increase almost continuously with time, from (a) 667±24°C, 1308±102 bar, in June 1983–July 1984, to (b) 990±30°C, 2958±146 bar in 2019-2020, for Bocca Grande, and 1010±37°C, 3034±183 bar in 2019-2020, for Bocca Nuova. Assuming that gas species equilibrate with anhydrite and calcite in the deepest part of the carbonate layer situated at a depth of 6 - 7 km (to be considered as an educated guess), there was a balance between total fluid pressure and external pressure in June 1983–July 1984. In contrast, a continuous increment in the excess fluid pressure (i.e., the difference between the fluid pressure and the overburden pressure) took place during the last twenty years and this increment was particularly marked in the last 3-4 years, possibly explaining the on-going resurgence of the entire Campi Flegrei caldera. The H2S-CH4 geothermometer was used to compute the CH4 concentration in the zone where H2S and CO2 equilibrate with anhydrite and calcite. Methane concentration turned out to be very low, as expected in magmatic fluids, presumably somewhat modified by absorption in deep brines and interaction with carbonate rocks. Deviations from ideality were also considered to calculate the redox potential of Solfatara fluids (at the H2S-CO2 equilibrium temperature) which turned out to be similar to those of some melt inclusions from the active Italian volcanoes. Hydrogen sulfide concentrations of Solfatara fluids were also used to evaluate the fugacities of other sulfur species such as S2, SO2, and COS. ∎∎∎

The continuous acquisition of CO2 soil flux data has been started on Mt Etna in November 2021, with the aim of assessing a first balance between CO2 from volcanic and biological origin. Our long-term goal is an interdisciplinary study of volcanic, biological, ecological, biogeochemical, climatic and biogeographical aspects, including the anthropogenic impact on the environment. All aspects are integrated in the study of the so-called Critical Zone, i.e. the layer between the deep rock and the top of the vegetation where the main biological, hydrological and geological processes of the ecosystem take place. The new research activity at Mt Etna is performed within the framework of the PON-GRINT project for infrastructure enhancement (EU, MIUR), and it adds up to activities going on at Grand Paradiso National Park (Italian Alps), and Ny Alesund (Svalbard, NO, High Arctic) in the framework of the IGG-CNR Critical Zone Observatories. During the first phase of the project, two fixed stations were installed in two sites at Piano Bello (Valle del Bove, Milo), in an area where the endemic Genista aetnensis grows. An Eddy Covariance system for net CO2 ecosystem exchange measurement and a weather station will be installed in 2022. Carbon stable isotopes data will be acquired periodically using in-situ instrumentation (i.e. Delta Ray). The installation sites are selected after CO2 soil flux surveys around the volcano using a portable accumulation chamber. The two stations installed at Piano Bello consist of an automatic accumulation chamber fixed to the ground, a mobile lid with a diffusion infrared sensor for measuring CO2, a data logger and a sensor for measuring soil moisture and temperature. The accumulation chambers are programmed to acquire data on ecosystem respiration every hour for all day. Data are transmitted to the IGG data collection center. The new IGG-CNR Mt Etna CZO will contribute investigating CO2 fluxes at the soil-vegetation-atmosphere interface in different geological and environmental contexts. We benefit from the collaboration with the National Institute of Geophysics and Volcanology (INGV), the Ente Parco dell'Etna, and the Dipartimento Regionale dello Sviluppo Rurale e Territoriale di Catania.

High-resolution magnetotelluric and gravity data have been collected over the Kiejo-Mbaka geothermal field, located along the NW–SE trending Mabka fault, in the Karonga Rift basin (East Africa Rift System). Such resolution allowed to reconstruct the field structure with unprecedented detail. Resistivity modelling has been obtained by three-dimensional finite-differences inversion of MT data, while density modelling has been accomplished by surface-oriented inversion of gravity data. Geophysical modelling has identified two sedimentary sub-basins separated by the Mbaka fault ridge, exposing the basement; these previously unknown sedimentary fills have a maximum thickness of ca. 1.5 km. The estimation of the clay cation exchange capacity (CEC) from magnetotellurics identifies a layer of low-temperature smectite alteration in the south-western sub-basin sediments, interpreted as a clay cap. The resulting updated conceptual model of the Kiejo-Mbaka geothermal system is therefore a fault-controlled system with lateral leakage into the sediments, expectably implying a larger reservoir volume than previously estimated.