Hydrothermal alteration exerts strong control on shallow permeability and degassing dynamics in geothermal systems. Here, we investigate how soil alteration influences near-surface gas flow by combining in situ petrophysical measurements with horizontal and vertical subsurface gas-concentration profiles at the Rotokawa geothermal field, New Zealand. These data are compared against unoccupied aerial system (UAS) thermal surveys of collapse structures across the field. Soil permeability at Rotokawa ranges from 8.7 × 10–14 to > 6.5 × 10–13 m2, highlighting strong meter- to decimeter-scale heterogeneity in shallow soil properties. Pumice-rich horizons are the main conduits for CO2 and CH4 flow, whereas clay-rich horizons locally act as semiconfining layers that promote CO2 accumulation and lateral diversion (leading to concentrations of > 4 × 104 ppm). Since CO2 does not condense under near-surface conditions, the clay layers promote horizontal flow along permeable beds until gas encounters a high-permeability escape route or collapse-related discontinuity. Collapse structures locally disrupt and reorganize flow by acting as conduits or sinks that focus, capture, or redistribute gases near their margins. The gas profiles reveal patterns consistent with a shallow gas–steam decoupling zone in which steam condensation may contribute to sealing processes, as previously observed in steam-heated geothermal systems worldwide. These coupled effects of soil type and structural and alteration controls explain the spatial heterogeneity of surficial degassing at Rotokawa and provide a framework for interpreting evolving degassing patterns in similar steam-heated geothermal systems. In the context of the reported decrease in diffuse CO2 emissions at Rotokawa, progressive shallow sealing and gas refocusing may have contributed to apparent changes in emission patterns, alongside reservoir processes, recharge variability, environmental effects, and methodological uncertainty.

Estimating ecological flows is essential in rivers to achieve the objectives defined by the EU Water Framework Directive 2000/60/EC (WFD). In the framework of an agreement with the Autorità di Bacino Distrettuale dell’Appennino Centrale, the work aims to present the results of an integrated approach developed to consider various factors affecting the river’s ecological flow (hydrological, hydrobiological, hydrogeological, hydro-morphological, and hydrochemical). The present study focuses on the Nera River, a main tributary of the Tiber River, which is primarily fed by groundwater from limestone aquifers. The river catchment hosts strategic water resources that are crucial for providing drinking water and sustaining aquatic ecosystems. Moreover, river water is utilized for hydropower generation, fish farming, and various recreational activities along the river. The ecological status was rated as good based on the New Index of the Ecological Status of Fish Communities (NISECI), along with physicochemical characterization of river water and hydromorphological characteristics as criteria for its definition. Based on a regional model specifically developed for brown trout of rivers in the Tiber River basin (thus applicable to the Nera River), the minimum ecological flow was set at approximately 2.92 m³/s. Based on flow-duration curves, the average and maximum ecological flow values were also identified as 3.71 and 5.07 m³/s, respectively. The analyses carried out by the Water Exploitation Index Plus (WEI+) revealed medium-to-high stress in the catchment; therefore, withdrawals should be carefully re-planned to minimize further impacts on water-dependent ecosystems. The approach proposed for the Nera River highlights the importance of conducting focused, multidisciplinary studies in areas where groundwater withdrawals interact with groundwater-dependent ecosystems, thereby supporting regional management plans that address the needs of both humans and aquatic ecosystems.

In Europe 65% of drinking water and 25% of water for agricultural irrigation come from groundwaters. Thermal and mineral groundwaters have an important role in society, for well-being and for economic purposes. Although widespread Alpine aquifers are critically important and highly vulnerable, regional-scale quantitative and qualitative studies on these groundwater resources remain remarkably limited. In this work we compiled a geo-dataset named ARETA (Alpine caRbon cyclE daTAset), containing more than 3,000 chemical analyses of georeferenced spring waters obtained both from the literature (technical reports, scientific publications, books, and other bibliographic sources) and from unpublished data collected during 2011-2022 fieldworks. For fewer than 20% of spring waters, analysis of the isotopic composition of water and carbon were also included, as well as flow rate values. The ARETA dataset significantly advances knowledge by addressing key geographic and hydrogeochemical gaps within the Alpine chain. Its broad coverage makes it an invaluable resource, especially when integrated with other established databases for large-scale studies. The dataset is publicly available at Figshare1.

Estimating ecological flows (EFs) in rivers is crucial for meeting the Water Framework Directive (WFD) 2000/60/EC goals. To develop an EF model, it is essential to use biological indicators to reliably record the impacts of human-induced alterations on aquatic ecosystems. The adaptability of fish to annual flow variability makes them a significant biological quality element (BQE). Consequently, using fish as bioindicators is a powerful tool for assessing the impact of changes in the hydrological regime on the natural communities within a river system. The new index of the ecological status of fish communities (NISECI) is a methodology developed in Italy that uses fish communities as BQEs to assess the ecological status of rivers, as directed by the WFD. We aimed to apply the NISECI to define the transition from the minimum vital flow (MVF), currently in force in Italian legislation, to the EF, as per the WFD. Specifically, we defined NISECI values for 26 stretches of river located within the Tiber River basin hydrographic network and characterized the physicochemical and hydromorphological conditions. Fish and environmental data were collected between July 2024 and May 2025. For summer flow rates (the low-flow season), we equated the EF to the MVF at locations where WFD objectives had been met (i.e. good ecological status). In the other cases, we predicted an increase in flow rate depending on the deviation from good ecological status. In line with this holistic multidisciplinary approach, we based variation in the quantity, quality, and timing of water discharge envisioned by the EF concept on the natural flow duration curves calculated for the Tiber River basin.

This work introduces a low-cost, custom-built, portable Internet of Things (IoT)-based Accumulation Chamber (IoT-AC), which integrates an ESP32 microcontroller, a Sensirion SCD30 CO2 sensor, and a servomotor for air homogenization, all controlled by a user-friendly, cross-platform application. Laboratory calibration confirmed the system's exceptional linearity (R2 0.9997) from CO2 rates of ~1 to ~1400 ppm·s-1, corresponding to CO2 diffuse fluxes ranging from ~30 (i.e., organic background fluxes) to ~38,900 g·m-2·d-1 (i.e., high fluxes in volcanic areas). During a rigorous field campaign at the Nea Kameni volcano in Santorini, Greece, the IoT-AC demonstrated a striking similarity to an industry-standard. Geostatistical analysis of the parallel datasets yielded comparable estimates of total diffuse flux (~9 tons·day-1 of CO2). This study validates the IoT-AC as a viable and scalable open-source alternative for diffuse soil volcanic CO2 monitoring, successfully lowering the financial barrier to high-quality data collection, making it accessible within practically any scientific budget, and hence enabling quantitative improvements in volcanic hazard assessment and the resolution of critical uncertainties in global volcanic carbon budgets.

Energy request from renewable sources is increasing due to high energy demand and the need of a more sustainable use of the resources. Among renewable sources, geothermal energy represents a powerful tool to reduce the energy dependence on fossils contributing to reducing the impact of climate change. Despite its high potential, geothermal energy has historically had a limited role in Italy, confined to the well known Tuscany areas, although it could have a more widespread exploitation satisfying local energy demands through both direct and indirect uses. The Emotion Project (GeochEMical characterization of geOThermal manifestations in Italy and development of the natIONal geothermal fluid web portal) is a three-year broad-scope project (2023-2025) funded by the Italian Ministry of University and Research in the framework of ten-year INGV PIANETA DINAMICO Research-Program (https://progetti.ingv.it/it/emotion). The ambition of EMOTION project is to accelerate the geothermal exploration for low, medium and high temperature (enthalpy) resources by a detailed geochemical characterization of the manifestations of geothermal interest located in central-northern Italy and to develop a solid and public web portal of all Italian geothermal manifestations, including those already studied in the central-southern part of the country (Vigor Project). Here we present first year results obtained by a detailed critical review of available geochemical information on thermal springs, mineral waters and gas emissions. These data represent the starting point to identify interesting and data-missing areas to be further investigated by new geochemical campaigns planned for 2024. Eleven Italian Regions were investigated (Tuscany, Umbria, Marches, Emilia Romagna, Liguria, Piedmont, Aosta Valley, Lombardy, Trentino Alto Adige, Veneto and Friuli Venezia Giulia) by a research team belonging to INGV, University of Florence, Perugia, Genoa and Calabria. The review data were collected from scientific papers, unpublished theses, regional datasets, reports and well logs (e.g., AGIP), other web portals and unpublished data. More than 4000 fluid manifestation information, among which thermal and cold springs, wells, bubbling polls, dry vents and fumaroles were collected and organized in a database, as homogeneous as possible. The database includes geographical data, geochemical analysis of major, minor, trace ad isotopic species, physics-chemical parameters and information on water table level and flow rate. To get hints on reservoir temperatures, chemical-physical processes ruling fluid circulation and to discriminate manifestations of geothermal interest from the others, a selection was made considering specific criteria, proposing also a first approach to standardizing geochemical data, potentially useful in the framework of opening and sharing scientific data.

The systematic sampling of the main fumaroles of Solfatara (Campi Flegrei, Italy) started during the bradyseismic crisis of 1983-84. In the late 1990s, diffusive CO2 emissions measurements also became part of the monitoring activity through systematic campaigns. In these 40 years of investigations almost unique databases were created including thousands of chemical and isotopic analyses of fumaroles and hundreds estimations of the diffuse CO2 emission. These databases provided the base of numerous geochemical and interdisciplinary scientific works to understand the processes occurring in the hydrothermal-magmatic system of Campi Flegrei, a caldera in unrest since 2005. The main results obtained by this effort indicate the pivotal role of magma degassing in the current crisis of Campi Flegrei. The deep magmatic fluids are injected into the hydrothermal system during episodes of magma degassing. These injections cause pressurization and heating of the hydrothermal systems, earthquakes, ground deformations, changes in fumarole compositions and escalating CO2 emission at the surface. The expulsion of these fluids constitutes the most energetic process currently occurring at Campi Flegrei; it is, in fact, more energetic than ground deformation and seismic activity. In this work, we present a review of these different aspects.

The Pannonian Basin (PB), in Central-Eastern Europe, is a continental area characterized by widespread presence of natural resources, high heat fluxes and outgassing of deep-sourced fluids (i.e. mantle-magma and/or crustal-derived). Moreover, the region is interested by ascent of the asthenosphere and a thin lithosphere (≈75 km). Here, we review 40 years of geochemical studies on natural gas emissions in the PB system and nearby areas providing the first comprehensive geochemical characterization of gas manifestations for the Croatian segment of PB. We use stable isotope (δ13CCO2) geochemistry, noble gases data, and CHe systematics to reconcile geochemical information with geophysical and geodynamic models at regional scale, and hence to characterize (i) the source/s of fluids outgassing at the surface and (ii) the main processes occurring during their storage in, and transit through, the crust.The chemical composition of the emitted fluids is very heterogeneous in the PB. We identify three distinct gas types (CO2-dominated, N2-dominated, and CH4-dominated) that are variably distributed in different sectors of PB. The He isotopic composition range from 0.07 to 6.32Ra (Ra is the air He isotopic signature), suggesting the coexistence of crustal and mantle components in the area. Furthermore, the same components also occur in the Croatian PB, where the He isotopic ratios range from 0.02 Ra to 2.21 Ra. The groundwater circulation in the PB implies an addition of atmospheric-derived noble gas component to the deep fluids (mantle vs crust-derived). The volumetric gas/water ratios (Vg/Vl) are highly variable (0.002 to 66) with the highest values in N2-dominated samples, and correlate with atmospheric-derived 20Ne concentration, pointing to shallow gas origin for these samples (relative to CO2 and CH4-dominated samples). The CHe systematics, coupled with the δ13C of CO2, indicates extensive chemical and isotopic fractionation due to partial dissolution of gas in water in the shallow crustal layers and consequent CO2 trapping in deep aquifers and/or in precipitating carbonates. In addition, methanogenesis could work as an additional potential CO2 sink in the crust. The mantle-derived He flux, on a regional scale, is estimated at 1.7 × 1010 to 1.7 × 1012 atoms m−2 s−1, one order of magnitude greater than found by O'Nions and Oxburgh (1988), and similar to what found in other tectonically active regions. The mantle-related CO2 flux computed using CO2/3He ratios and the mantle He fluxes, range between 103 and 105 mol·km−2·year−1. Despite representing a rough estimation, these values are in the range of the CO2 fluxes in active and quiescent worldwide volcanic systems. We propose the transfer of mantle-derived volatiles to occurs through lithospheric faults in the PB and adjacent regions, although the presence of magmatic intrusions in crustal layers is an additional contributing factor.

Pululahua is a potentially active andesite and dacite lava dome complex. This paper presents the results of a survey focused on carbon dioxide (CO2) diffuse degassing at Pululahua, which was conducted during the 2017 International Association of Volcanology and Chemistry of the Earth's Interior (IAVCEI) Commission of the Chemistry of Volcanic Gases (CCVG) 13th Gas Workshop. Our objective was to conduct a comprehensive investigation of CO2 diffuse degassing by employing standard methods for measuring CO2 flux and temperature, and data processing. These methods were applied to map the spatial distribution of the measured parameters, investigate the origin of CO2, and quantify the volcanic CO2 output within the surveyed area of Pululahua. We carried out a total of 350 soil CO2 flux and 329 soil temperature measurements and collected 12 gas samples for carbon isotopic composition analysis, surrounding the three youngest domes in the complex. In addition, seventeen CO2 flux measurements over a thermal water pool were performed. Our findings indicate that the diffuse emission at Pululahua's crater floor is fed by both biogenic and volcanic CO2. Fluxes from each source are similar in magnitude, with approximately 90% of the measurements falling into an intermediate flux range. The occurrence of volcanic CO2 emissions is supported by the carbon isotopic composition. Diffuse degassing distribution highlights a CO2 anomaly surrounding the younger domes within the crater. We estimated the CO2 diffuse emission using both statistical and geostatistical approaches over area of 3.36 km2, resulting in values of 154.2 t d−1 and 126.2 t d−1 respectively. Based on the geostatistical quantification of the total CO2 emission from soil degassing, Pululahua's crater volcanic CO2 contribution is estimated between 59 and 97 t d−1. Finally, the potential hazards associated with the release of cold CO2 at Pululahua's crater are also discussed.

Valley of Death, discovered almost half a century ago and located in the very upper reaches of the river Geysernaya, about 7 km from the Geyser Valley in Kamchatka, is famous for occurrences of dead animals there. During field work in August 2023, the soil CO2 flux was measured using the accumulation chamber method in the lower section of the Valley of Death. On an area of 6.2 x 10(3) m(2), the flux was measured at 100 randomly distributed points. At several points a MultiGas device was used for analysis of the composition of soil gases (CO2, H2S, SO2). Data processing showed the presence of a single "hydrothermal" population of the CO2 flux. The average CO2 flux was found to be 1272 g m- 2 d(-1), with the maximum value of 28,984 g m- 2 d-(1). The average weight ratio of CO2/H2S was 14.7 +/- 4, and thus, the "deadly" part of the surface of Death Valley in August 2023 emitted -8 t d(-1) of CO2 and - 0.54 t d(-1) of H2S. The soil temperature at the measurement points was close to the air temperature and did not correlate with the CO2 flux. Such value of the CO2 flux corresponds not <3.5 kg s(-1) of hydrothermal steam condensed beneath the degassing part of Valley of Death.

Pululahua is a potentially active andesite and dacite lava dome complex. This paper presents the results of a survey focused on carbon dioxide (CO2) 2 ) diffuse degassing at Pululahua, which was conducted during the 2017 International Association of Volcanology and Chemistry of the Earth's Interior (IAVCEI) Commission of the Chemistry of Volcanic Gases (CCVG) 13th Gas Workshop. Our objective was to conduct a comprehensive investigation of CO2 2 diffuse degassing by employing standard methods for measuring CO2 2 flux and temperature, and data processing. These methods were applied to map the spatial distribution of the measured parameters, investigate the origin of CO2, 2 , and quantify the volcanic CO2 2 output within the surveyed area of Pululahua. We carried out a total of 350 soil CO2 2 flux and 329 soil temperature measurements and collected 12 gas samples for carbon isotopic composition analysis, surrounding the three youngest domes in the complex. In addition, seventeen CO2 2 flux measurements over a thermal water pool were performed. Our findings indicate that the diffuse emission at Pululahua's crater floor is fed by both biogenic and volcanic CO2. 2 . Fluxes from each source are similar in magnitude, with approximately 90% of the measurements falling into an intermediate flux range. The occurrence of volcanic CO2 2 emissions is supported by the carbon isotopic composition. Diffuse degassing distribution highlights a CO2 2 anomaly surrounding the younger domes within the crater. We estimated the CO2 2 diffuse emission using both statistical and geostatistical approaches over area of 3.36 km2, 2 , resulting in values of 154.2 t d- 1 and 126.2 t d- 1 respectively. Based on the geostatistical quantification of the total CO2 2 emission from soil degassing, Pululahua's crater volcanic CO2 2 contribution is estimated between 59 and 97 t d- 1 . Finally, the potential hazards associated with the release of cold CO2 2 at Pululahua's crater are also discussed.

Passive rift systems are often characterized by CO2 degassing, witnessed by the presence of mineral and thermal springs, bubbling pools, mofetes. Despite these field manifestations, the quantitative estimation of the CO2 budget released to the atmosphere from these geodynamic structures is not well constrained. Here, we examine the chemistry of 169 springs, the isotopic composition of the dissolved carbon (delta C-13(TDIC)) of 33 springs and the dissolved gases composition of 6 springs from the French Massif Central, part of the European Cenozoic Rift System (ECRIS), in order to describe the CO2 degassing process and to compute the CO2 emission rate released from groundwaters at regional scale. Water-gas-rock models reveal that the separation of gas from the liquid phase occurs at P-T conditions between 10 bar-180 degrees C and 1 bar-10 degrees C. The carbon mass and isotopic balance of spring waters of the French Massif Central allow us to compute a total deeply-sourced CO2 emission rate of 1.52 +/- 0.14 x 10(9) mol yr(-1), suggesting that the CO2 release from passive rift systems is significant at global scale and should be considered in the present-day global Earth degassing budget. The comparison of our data to other continental rift systems shows a high variability of CO2 emission rates, highlighting that more detailed studies are needed to constrain the CO2 flux from this geodynamic setting that, at present, is likely underestimated.

Arctic regions are among the fastest warming areas of the planet. Increasing average temperatures over the last five decades have deepened the thawing of the upper-most layer of permafrost across the Arctic, which contains significant amounts of organic carbon. The progressive deepening of seasonal thawing releases carbon that is used by active microorganisms which also produce greenhouse gases, potentially onsetting a positive feedback on global warming. Despite their importance in controlling organic matter degradation and greenhouse gas fluxes to the atmosphere, there is a lack of data on activity and dynamics of microbial communities in High Arctic soils in response to seasonal thaw. This report describes three specific expeditions performed on the Svalbard archipelago, carried out within the framework of the PRA (Italian Arctic Research Program) project Melting-ICE, performed between February and October 2022, reporting site characteristics and samples collected. The project aims to investigate the diversity and activity of active layer microbial communities across a full season thaw cycle, correlating microbial diversity with gas fluxes and composition. During these expeditions, a total of eight different sites were selected to investigate the microbiology and geochemistry of soils, as well as to estimate the gas fluxes from the soil to the atmosphere. The data collected in the field, combined with the results obtained in the laboratory, will provide a snapshot of the seasonal activity of the microbial communities present in the permafrost’s active layer. The three campaigns will provide data to estimate the impact of permafrost melting on the carbon cycle and the role of microorganisms in the release of greenhouse gases.

Arctic regions are among the fastest warming areas of the planet. Increasing average temperatures over the last five decades have deepened the thawing of the upper-most layer of permafrost across the Arctic, which contains significant amounts of organic carbon. The progressive deepening of seasonal thawing releases carbon that is used by active microorganisms which also produce greenhouse gases, potentially onsetting a positive feedback on global warming. Despite their importance in controlling organic matter degradation and greenhouse gas fluxes to the atmosphere, there is a lack of data on activity and dynamics of microbial communities in High Arctic soils in response to seasonal thaw. This report describes three specific expeditions performed on the Svalbard archipelago, carried out within the framework of the PRA (Italian Arctic Research Program) project Melting-ICE, performed between February and October 2022, reporting site characteristics and samples collected. The project aims to investigate the diversity and activity of active layer microbial communities across a full season thaw cycle, correlating microbial diversity with gas fluxes and composition. During these expeditions, a total of eight different sites were selected to investigate the microbiology and geochemistry of soils, as well as to estimate the gas fluxes from the soil to the atmosphere. The data collected in the field, combined with the results obtained in the laboratory, will provide a snapshot of the seasonal activity of the microbial communities present in the permafrost’s active layer. The three campaigns will provide data to estimate the impact of permafrost melting on the carbon cycle and the role of microorganisms in the release of greenhouse gases.

&lt;p&gt;The French Massif Central (central-southern France) and the Eifel region (central-western Germany) are both young volcanic systems and considered dormant. They are part of the European Cenozoic Rift System (ECRIS) and show similar surficial manifestations of ongoing hydrothermal activity. For example, both areas exhibit numerous low flow rate CO&lt;sub&gt;2&lt;/sub&gt;-rich springs, mainly occurring in concomitance of faults and fractures inherited from the Variscan orogeny.&lt;/p&gt;&lt;p&gt;Here, the chemical and isotopic characterization of different fresh water bodies (springs, wells, rivers and volcanic lakes) has been provided. The composition of dissolved gases and the isotopic signatures of dissolved carbon indicate that meteoric water infiltrated and then interacted with a CO&lt;sub&gt;2&lt;/sub&gt;-rich, mantle-related, component. The majority of studied water samples exhibit pCO&lt;sub&gt;2&lt;/sub&gt; between 0.3 and 1 bar and the total dissolved inorganic carbon (TDIC) is of the order of 0.01 mol/kg. At surface, most spring water samples are oversaturated with calcite, dolomite, chalcedony and quartz and are in equilibrium with amorphous silica. The correlation between the TDIC and its isotopic composition (&amp;#948;&lt;sup&gt;13&lt;/sup&gt;C&lt;sub&gt;TDIC&lt;/sub&gt;) suggests that part of the analysed water samples experienced a degassing process prior to or immediately after emergence. The computed CO&lt;sub&gt;2&lt;/sub&gt; flux transported by groundwaters is of the same order of magnitude of the global baseline theorized for geothermal areas. This indicates that passive rifts systems contribute to the atmospheric CO&lt;sub&gt;2&lt;/sub&gt; content and highlights the importance of taking into account each carbon source in the study of the global carbon cycle.&lt;/p&gt;

In the central part of Tuscany region (Italy), is located the Larderello – Travale geothermal system which is a large-scale steam dominated system with reservoir temperatures that can exceed 350°C (Bellani et al. 2004). The characteristic high heat flow in this particular area is due to the presence of a thermal anomaly caused by the intrusion of a big Pliocene batholith into the upper crust (Musumeci et al. 2002). This work is aimed at investigating the relationships between carbon emissions and heat, particularly to analyse the distribution of CO2, CH4 and soil temperatures in the Monterotondo Marittimo and Sasso Pisano areas. Three hundred measurements of gas fluxes from the soil have been performed using the accumulation chamber method. CO2 fluxes range from 0.1 gm-2d-1 to about 20,000 gm-2d-1, while CH4 fluxes, available for a lower number of points, vary between 0 and 637 gm-2d-1. Soil temperatures were also measured at each location and ranges from 8.0 °C to 100 °C, with an average of 39.8 °C.CO2 fluxes show a polymodal statistical distribution with (i) a background population characterised by an average CO2 flux in the order of 16.0 g m-2 d-1 and (ii) anomalous populations with an average CO2 flux of 400 g m-2 d-1 and 1600 g m-2 d-1 for Sasso Pisano and Monterotondo Marittimo respectively. Not null CH4 fluxes were measured only at points with a CO2 flux in the range of the anomalous CO2 flux population. The statistical distribution of the CH4 resulted more complex with two populations characterized by an average value of 0.8 g m-2d-1 and 174 g m-2d-1 respectively, probably reflecting differences in the gas transport mechanism in the soil and/or soil permeability, which is largely variable in the areas with anomalous flux.The areas characterized by anomalous soil gas fluxes, show also an evident soil temperature anomaly (reaching values close to 100 °C), suggesting that soil degassing is accompanied by a significant process of steam condensation. In the anomalous areas, the CO₂/CH₄ ratios by weight vary between 1.6 x 10-4 to 1.0 x 10-1 and fall in the range of variation observed for the geothermal fluids of the Larderello-Travale region (Truesdell & Nehring, 1978; Chiodini et al., 1991; Chiodini & Marini, 1998).Assuming that the soil is heated by steam condensation, a thermal energy release associated to the degassing process of about 200 MW is estimated for Monterotondo Marittimo, an energy release >15 MW is estimated for Sasso Pisano, where the measurements are still in progress.

Changes in groundwater flow in response to strong earthquakes are widely described in many tectonic environments. For example, a post-seismic discharge variation is often attributed to an increase of bulk permeability due to co-seismic fracturing and/or to a change in the role of faults in acting as conduits/barrier to groundwater flow.We take as an example the fractured aquifer of the Mts. Sibillini carbonate massif, in Central Italy, which were affected by a strong and prolonged extensional seismic sequence in 2016-17. The sequence was characterized by an M=6.5 event (mainshock), an M=6 event, an M=5.9 event, up to 60 M>4 events and several M>5 earthquakes. The strongest events caused rupturing of the topographic surface for a cumulative length in the order of 30 km and an important portion of aftershocks occurred at depths where groundwater is stored.As a response to the seismic sequence, the main NNW-directed groundwater flow was diverted to the west and a discharge deficit was observed at the foot-wall of the activated fault system with a relevant discharge increase, accompanied by geochemical variations, at the fault system hanging-wall.By integrating geo-structural reconstructions, seismological and ground deformation data, artificial tracer tests results and a 4-years discharge and geochemical monitoring campaign data, we show that the observed groundwater variations are due to a combination of permeability increase along the activated fault systems and hydraulic conductivity increase of the hanging-wall block due to fracturing, extension and subsidence, which determined a fast aquifers emptying. Seismicity temporarily triggered a change of the pre-existing predominant along-faults-strike NNW-SSE oriented regional flow to a west-directed flow, perpendicular to faults strike. We discuss the position of the aquifer with respect to the activated faults and how this affected the observed phenomena. REFERENCECambi, C., Mirabella, F., Petitta, M., Banzato, F., Beddini, G., Cardellini, C., ... & Valigi, D. (2022). Reaction of the carbonate Sibillini Mountains Basal aquifer (Central Italy) to the extensional 2016–2017 seismic sequence. Scientific Reports, 12(1), 1-13. DOI: 10.1038/s41598-022-26681-2

Karst hydrosystems represent one of the largest global drinking water resources, but they are extremely vulnerable to pollution. Climate change, high population density, intensive industrial, and agricultural activities are the principal causes of deterioration, both in terms of quality and quantity, of these resources. Samples from 172 natural karst springs were collected in the whole territory of Greece. To identify any geogenic contamination and/or anthropogenic pollution, analyses of their chemical compositions, in terms of major ions and trace elements, were performed and compared to the EU limits for drinking water. Based on chloride content, the collected karst springs were divided into two groups: low-chloride (< 100 mg L-1) and high-chloride content (> 100 mg L-1). An additional group of springs with calcium-sulfate composition was recognised. Nitrate concentrations were always below the EU limit (50 mg L-1), although some springs presented elevated concentrations. High contents in terms of trace elements, such as B, Sr, As, and Pb, sometimes exceeding the limits, were rarely found. The Greek karst waters can still be considered a good quality resource both for human consumption and for agriculture. The main issues derive from seawater intrusion in the aquifers along the coasts. Moreover, the main anthropogenic pollutant is nitrate, found in higher concentrations mostly in the same coastal areas where human activities are concentrated. Finally, high levels of potentially harmful trace elements (e.g. As, Se) are very limited and of natural origin (geothermal activity, ore deposits, etc.).

The continuous monitoring and real time analysis of chemical-physical parameters of freshwater flows is of fundamental importance for numerous strategic activities. For instance, the management of water resources, environmental monitoring and the study of chemical-physical and quantitative variations before and after major seismic events affecting areas where important aquifers are located. A low-cost and energy autonomous wireless sensing system has been developed for continuous water chemical-physical monitoring. In particular, the sensing system is capable of measuring the dissolved carbon dioxide (dCO2) in water along with salinity, conductivity and temperature through a low-power (< 3 mW) infrared sensor.