Rare earth elements (REE) are essential for low-carbon and digital technologies, yet their primary sources remain geologically restricted and geopolitically vulnerable. This study shows that volcanic geothermal skarn systems can host substantial high REE concentration. Using core and cutting samples from a 2500 m deep geothermal borehole in the Sabatini volcanic district (central Italy), we reconstruct the chemical zonation and metasomatic evolution of calc-silicate reservoir formed by high-temperature fluid-mediated magma-carbonate interaction. Whole-rock and mineral chemistry indicate that light REE (LREE) are concentrated in an upper (ca. 400 m thick) vesuvianite-rich interval, whereas heavy REE (HREE) are preferentially incorporated in garnet at greater depths. Vesuvianite is identified as the dominant REE host (> 9000 ppm total REE), and accounting for most of the REE budget. Although the economic potential of the Sabatini skarn reservoir remains to be evaluated, geometry-based estimates indicate the Sabatini skarn as a potentially high-grade REE deposit at global scale. The widespread occurrence of similar skarn systems in Quaternary volcanic districts of Italy, coupled with extensive carbonate decarbonation in magmatic arcs, suggests that fluid-mediated magma-carbonate interaction in volcanic environments may represent an unexplored mechanism for REE enrichment and redistribution of metals within the continental crust.

This study investigates how external insulation materials used for energy efficiency affect indoor radon accumulation, using a scale model room built with ignimbrite, a highly radon-emitting volcanic rock. Two insulation materials—mineral wool (open-cell, 98% porosity) and extruded polystyrene (XPS, closed-cell, >95%)—were applied to the outer walls of the model room. Their effects were tested in combination with three internal radon barriers (silane-terminated membrane, silicone sealant, bitumen membrane) and under varying ventilation rates (0.11 h−1 and 0.44 h−1). Radon concentrations were measured using calibrated detectors over five experimental phases. Without ventilation, XPS increased indoor radon by up to +351%, while mineral wool showed a milder effect (+26%). The silicone sealant reduced radon by up to 90%, outperforming other barriers. Ventilation significantly lowered radon levels, simulating the “flushing” effect of wind. The combination of impermeable insulation and lack of air exchange led to the highest radon accumulation. High-performance insulation can compromise indoor air quality by trapping radon, especially in buildings with high geogenic radon potential. Effective mitigation requires pairing insulation with high-performing radon barriers and adequate ventilation. These findings highlight the need to balance energy efficiency with indoor environmental safety.

Cilla G., Dramis F., Fubelli G., Maceroni D., Malocco S., Materazzi M., Remigio M., Soligo M., U/Th dating of pre-Holocene calcareous tufa deposits in the Umbria-Marche Apennine (Italy). (IT ISSN 0391-9838, 2025). This note describes the characteristics of two calcareous tufa (freshwater travertine) deposits found in the Umbria-Marche Apennine. The first has grown in the Laverinello Valley, a tributary of the upper Potenza River, along the road from the village of Poggio Sorifa; the second deposit originated in Val di Sasso (Sasso Valley), a tributary of the upper Esino River, on the edge of a waterfall, currently inactive and disconnected from the present drainage network. The U/Th dating of samples taken from the investigated tufa deposits (55 +/- 6 ka BP-58 +/- 6 ka BP, 65 +/- 8 ka BP-67 +/- 5 ka BP, respectively) places them in the Upper Pleistocene, corresponding to sharp warming peaks within cooling periods. These dates seem to support the genetic model of freshwater travertine deposition proposed by Dramis et al. (1999), based on the control exerted by the formation in the aquifer of a reversed thermal gradient in correspondence with climate warming.

Tectonically raised paleoshorelines have been recently identified along the southern fault scarps of the Mt. Fellino and Roccarainola horst blocks, which are part of the northeastern border of the Campania Plain coastal basin (southern Apennines, Italy). Such horst blocks are bounded to the south by the Polvica Fault, a roughly E-W trending normal fault. The sequence of uplifted paleoshorelines has been studied in detail by integrating geomorphological, structural and stratigraphical analyses to assess the Quaternary uplift of the Mt. Fellino and Roccarainola horst blocks. Yet, the staircase of paleoshorelines is still not chronologically well constrained. Aimed at constraining the uplift history of Mt. Fellino and Roccarainola horst blocks and the rate of activity of the Polvica fault, in this study, we integrate former knowledge on paleoshorelines with a geomorphological analysis to map erosional terraces, that we interpret as remnants of shore platforms. We apply the synchronous correlation method, driven by new and a former Th-230/U-234 dating of calcite veins cutting marine sands, to infer the age of the paleoshorelines and terraces. Based on the synchronous correlation, the mapped paleoshorelines and terraces are correlated with sea-level peaks of the late Early to Late Pleistocene. In particular, the paleoshorelines along the Mt. Fellino ridge are correlated with the Marine Isotope Stage (MIS) 7e and 9c or 11, while the oldest terrace is correlated with the sea-level peak of 980 ka. Using inferred paleoshorelines ages, we estimate the uplift rate of the Polvica Fault footwall. The uplift rate varies from c. 0.2 mm/yr close to the western fault tip up to c. 0.5-0.6 mm/yr in the East, in the Roccarainola block. We combine surface evidence with subsurface data from a shallow well to constrain the vertical throw of the Polvica Fault. A mean fault throw rate of c. 0.4 mm/yr in the last c. 1 Ma is estimated for the central part of the PF. Assuming that the Polvica Fault is still active, we estimate the maximum expected earthquake by means of empirical relationship and obtain a Mw similar to 6.2 value and recurrence interval value of c. 1,200 yr. Historical seismicity activity of the PF has not been acknowledged to date. However, our results raise the crucial question of an in-depth assessment of the seismic hazard for the densely populated Campania Plain.

In the retro-wedge side of a mountain chain undergoing back-arc extension, the progressive development of the fluvial network is controlled by the interaction of the uplift of the orogen, the activity of tectonic structures, and the climate. Many studies have evidenced the continuous competition between the activity of the normal faults that generate intermontane basins and rivers that incise and erode headward. Less attention has been paid to the role of the extensional structures that border the basins at the foot of the orogen and close to the base level (the back-arc basin) in the development of the hydrography draining their footwall. Could these structures influence or even prevent the integration of the fluvial network into the retro-wedge side of an uplifting orogen? To answer to this question, we studied the Aniene R., a tributary of the Tiber R. that drains the western side of the central Apennines (Italy). Studying the geometry of the topography and hydrography of its basin, surveying some key areas, dating deposits, and inverting its longitudinal profile, we reconstructed the landscape evolution of the drainage basin. In particular, we provide new evidence on the involvement of the structures bordering the low-standing extensional basins in the drainage development. Indeed, the flexural uplift of their footwall can hamper their flow down to the base level closing temporary the upstream drainage basin and so influencing the alternating phases of erosion and deposition controlled by uplift and climate.

Indoor radon is classified as a carcinogen because it can lead to lung cancer. Some radon preventive strategies are related to building protection with radon barrier materials whose capacity to stop the gas depends on the diffusion coefficient, which can be calculated using different techniques. In this article, we propose a new experimental device, called TESTMAT, to measure the radon diffusion coefficient, using a weak radon source, to prevent radiation protection oversight. The device is small and made from PVC. The sample of the tested material is placed between the source and the receiver containers, as indicated by ISO/TS 11665-13 standard. Since a non-stationary radon diffusion occurs in the system, we developed a specific software, ENDORSE, to model radon activity concentrations in the receiver chamber and the diffusion through the material by applying the explicit finite difference method. The software utilizes Montecarlo simulation to determine the error associated with the diffusion coefficient. Different tests were performed to calibrate the system and assess the value and the evolution of background radon during the two-week measurement. When working with low-activity radon sources, this parameter cannot be neglected, particularly with the best performing membranes. An adequate sample holder was selected to guarantee a good airtightness, with a leakage constant of only 7 % of the radon decay constant. The minimum detection limits were calculated based on the material thickness and the source intensity. The system was finally tested with three commercially available waterproofing membranes and results compared with expected values, based on literature.

Indoor radon is one of the most significant contributors to lung cancer after smoking. Mitigation strategies based on protecting buildings with radon barrier materials, combined with home ventilation or room pressurization, are regularly used. A scale model room made from a porous ignimbrite rich in radon precursors was used as an analogue to test the efficiency of fifteen airtight membranes to reduce radon levels, also in combination with room pressurization. The results of these experiments were considered together with previous ones to propose the scale model room approach as a tool for rapidly evaluating the performance of specially designed radon barrier materials, and for radiation exposure assessment. Relative reduction of indoor radon (RIR) ranges from −20 to −94%. The most effective materials were FPO membrane, single-component silane-terminated polymer membranes and synthetic resins. The presence of additives likely modified the composition and structure of some products, improving their radon barrier capacity. The introduction of room pressurization further reduced radon levels in the model room where the membranes were applied. The overpressure necessary to reach RIRs of the order of 85–90% is very low for materials that powerfully stop radon even without ventilation, but necessarily higher for poorer membranes.

Indoor radon surveying and remediation were implemented in a single-family home affected by high levels of indoor radon in the Celleno municipality (central Italy) with the aim of identifying the contribution of radon sources, evaluating the factors affecting radon entry into the building, and reducing radon risk. Average radon levels were relatively low at the ground floor (286 ± 202 Bq m−3) and first floor (167 ± 84 Bq m−3) in autumn when the temperature was still warm and the windows were open, but increased up to 2776 ± 1768 Bq m−3 and 970 ± 202 Bq m−3 in the first half of December, when the heating system was on and the windows were closed. The inner walls of the pilot room at the ground floor, semi buried on one side, were then treated with a waterproof product (a silane terminated polymer) and the average radon was halved (1475 ± 1092 Bq m−3) in the following month, which was still characterised by winter conditions. Radon entry in the room was identified and sealed with the same product, and a radon accumulation space behind a NE-SW oriented wall was naturally ventilated, reducing radon below the reference level in April with northerly winds conditions.

Soil and groundwater contamination by NAPLs (Non-Aqueous Phase Liquids) is certainly a big issue for protecting the environment. In situ clean-up actions are routinely applied to mitigate the risk and are supplemented by monitoring surveys to assess the degree, extension, and evolution of the contamination. Radon gas is here used as a tracer of contamination because of its high solubility in non-polar solvents that produce a reduced concentration of the gas in polluted soil and groundwater with reference to radon levels in adjacent “clean” areas. This approach was employed in two sites where gasoline and diesel spillage occurred, causing soil and groundwater contamination. The two case studies were chosen because of their difference in terms of the hydrogeological features, age of the spillage, composition of residual NAPLs, and clean-up measures to test the advantages and limits of this approach in a variety of settings. Radon data, NAPL concentration in the groundwater (mainly total hydrocarbons, Methyl Tertiary-Butyl Ether and Ethyl Tertiary-Butyl Ether) and the depth of the groundwater table were periodically collected in surveys that spanned a period of two years. This dataset was statistically processed using principal component analysis to unravel which factors and attenuation processes are working in the sites and the response of the radon deficit approach to this complex series of phenomena concurrently occurring there.

The central Apennines are a Cenozoic fold-and-thrust belt that has been affected by post-orogenic extension in its axial region since the end of the early Pliocene (ca. 4 Ma). Post-orogenic extension generated several intermontane basins bounded by high-angle normal faults, striking NW-SE, subparallel to the backbone of the chain. The Monte Pettino and the Monte Marine seismogenic faults (MPF, MMF) are the boundary faults of the western portion of the late Pliocene-Quaternary L’Aquila intermontane basin. Their long-term activity is typified by exhumed fault cores that coexist with active fault strands localised at the fault hanging walls, providing evidence of a polyphase tectonic activity. The fault cores are decorated by diffuse dolomitization, which indicates structurally controlled fluid-flow and metasomatism. To constrain the long-term (space-time) evolution of the MPF-MMF faults, we integrated fieldwork, stable isotope systematics (δ18O, δ13C and Δ47), carbonate thermoluminescence and U-Th dating. Our results highlight two main tectonic phases, with different structural evolution and fluid-rock interaction. The first phase corresponds to the development of a major cataclastic zone, defined by meter-thick, SW-dipping (65-70°), fault cores exposed at the piedmont of the MPF-MMF ridges. The C-O systematics of the cataclasite and of the associated calcite slickenfibers, which are in the range of the carbonate bedrock, indicate a "closed" system behaviour during fault nucleation and development. Preliminary results from Δ47 thermometry of syn-kinematic carbonate structures indicate temperatures of 34 ± 2 °C. Thermoluminescence dating of dolomite clasts in the fault zone indicates age in the range of 3.0 – 3.4 Ma, whilst the cataclastic fault core is younger (< 800 ka). The second phase is mainly recorded in upper Pleistocene sedimentary Breccias (ca. 350 ka) which unconformably cover the bedrock and the exhumed fault cores at the SE termination of the MPF. It consists of anastomosed, high-angle WNW-ESE striking fault strands, spaced meters apart and with cm-m displacements, associated with carbonate veining and travertines. Stable isotopes measured from the fault slickenfibers, carbonate veins and travertines show negative δ13C and δ18O values, suggesting a depositional system dominated by meteoric fluid ("open" system) with an important contribution of organic carbon. Travertines and veins precipitated at colder temperatures (12 ± 4 °C), in the range of the average local air temperatures, thus excluding precipitation from a hydrothermal circuit. Moreover, their U-Th ages range between 182 and 331 ka, compatible with the temporal constraints from stratigraphic data. Structural and isotopic results do not support tectonic reactivation of the cataclastic core of the MPF during the middle-late Pleistocene, confirming the stratigraphic evidence. Our results provide the first absolute age constraint on the post-orogenic extensional faulting in the L’Aquila basin, demonstrating a two-stage fault activity, characterised by a change from localised (from ca. 3 to ca. 0.8 Ma) to delocalised faulting (200-300 ka to present). We infer that this change in the style of extensional faulting was consequence of the evolving rheological structure of the fault zones, primarily regulated by the feedback and interactions involving structurally-controlled fluid flow, rock metasomatism and cataclastic processes in space and time.

Travertine depositional systems are the surficial evidence of an active geothermal system developing in the upper crust. They are often associated with further geothermal manifestations, such as gas vents (mainly CO2) and thermal springs from which the travertine develops. The distribution of the geothermal manifestations and the growth of the travertine deposits are strictly controlled by active, potentially seismogenic structures. Thus, the study of the geothermal manifestations including travertine deposits can provide information on the seismotectonic setting of an area, revealing the fault occurrence, orientation, and kinematics. In this paper we present a study focused on the relationships among Late Pleistocene-Holocene travertine deposits, still in deposition, thermal springs, gas vents and the Neogene-Quaternary faults in the Monte Amiata Volcano-Geothermal area. Results from a new detailed field mapping aimed at (i) reconstructing the isolated travertine bodies in an area of about 2 km2, in terms of geometry, age (by U/Th radiometric dating) and depositional setting, and (ii) refining the structural dataset on the substratum rocks (formed by Tuscan and Ligurian Units) allowed to define the main faults controlling the geothermal manifestations and related travertine deposition. We highlight fault arrays compatible with a releasing step-over zone which geometry has been partly inherited by previous structures. At the same time, the study on travertine deposits allowed to recognize Late Pleistocene-Holocene fissure ridge-type and mound-type travertine deposits developed along the traces of faults, which still control, locally, gas emission and the location of thermal springs. We also discuss the tectonic setting in the framework of the evolution of the Monte Amiata Volcano- Geothermal area and in the seismotectonic setting.

Non-polar liquids released in environment cause a long-term soil and groundwater contamination. The costs associated with a multi-year remediation are high and the uncertainty in the allotment of legal responsibilities could defer the decontamination planning. Therefore, a reliable method to assess the residence time of spilled Non-Aqueous Phase Liquids (NAPLs) in soil is highly needed. In this paper, a method, using low environmental radioactivity and radiometric dating, is described and applied to real contaminations. After being alpha-recoiled from 232Th in soils,228Ra accumulates in light NAPLs, generating 228Th. A disequilibrium clock, based on gamma-spectrometric determination of the ratio 228Th/228Ra, was conceived to measure the residence time of LNAPL pollutants in a soil. The pollutant extraction and gamma-counting procedures are described. This approach inverts the role played by pollutants and contaminated matrixes, because the flux of alpha recoil from soil generates in pollutants a reliable model of "closed system", which is preserved in LNAPLs due to the peculiar properties of non-polar liquids. All case studies are sited in Italy and have been supported by preliminary lab tests. Dating tests of 15 samples (including LNAPLs, contaminated soils and oil socks) were performed, in most cases, blindly. Then, the results were compared to historical data about contaminations. A good correlation between test results and site history was generally obtained. But an increasing error has to be considered in old contaminations due to the nonlinear nature of disequilibrium time equation. Other reasons of discrepancies, due to system opening, include the use of surfactants, the presence of significant amount of MnO2 in soil and the interactions of different spillages. The outcomes of this research evidence the possibility to precisely date the contamination both in soil and in non-polar liquids, offering a potential tool to settle legal disputes. Further studies could broad and improve the applicability of the method.

Indoor radon is the second cause of lung cancer. Mitigation strategies are based on (i) building protection with radon barrier materials, (ii) increasing home ventilation or (iii) room pressurization. A scale model room created with a porous ignimbrite rich in radon precursors was used as an analogue to test the indoor radon reduction ability of various radon barrier materials in a real room. The properties of these materials were tested with and without room pressurization by introducing outdoor air at different flow rates. The best materials reduced indoor radon up to 80% and, when the highest pressurization was applied, to 93%.

An accurate record of preindustrial (pre-1900 CE) sea level is necessary to contextualize modern global mean sea level (GMSL) rise with respect to natural variability. Precisely dated phreatic overgrowths on speleothems (POS) provide detailed rates of Late Holocene sea-level rise in Mallorca. Statistical analysis indicates that sea level rose locally by 0.12 to 0.31 m (95% confidence) from 3.26 to 2.84 thousand years (ka) ago (2σ) and remained within 0.08 m (95% confidence) of preindustrial levels from 2.84 ka to 1900 CE. This sea-level history is consistent with glacial isostatic adjustment models adopting relatively weak upper mantle viscosities of ~1020 Pa s. There is virtual certainty (>0.999 probability) that the average GMSL rise since 1900 CE has exceeded even the high average rate of sea-level rise between 3.26 and 2.84 ka inferred from the POS record. We conclude that modern GMSL rise is anomalous relative to any natural variability in ice volumes over the past 4000 years.

This study integrates field, geochronological and geochemical data to constrain fluid circulation in the damage and core zone of the seismogenic Monte Morrone Fault System (MMFS), central Apennines (Italy). Faulting along the MMFS evolved from a diffuse deformation at the damage zone towards progressive localisation of a narrower fault core and, finally, to (re)activation of discrete slip surfaces at shallower crustal conditions. Multiple generations of carbonate mineralisations, including veins and slickfibers, occur along the main fault surfaces. Carbonate mineralisations are locally fractured and incorporated in the surrounding cataclasites, documenting repetitive structurally-controlled fluid infiltration during transient episodes of permeability creation and destruction. Stable carbon and oxygen isotopes of the carbonate mineralisations document a dominant meteoric water source probably mixed with deeper circulating waters having longer residence time. Clumped-isotope yield formation temperatures of vein and slickenfibers in the range between 23 and 40 degrees C. U-Th dating of carbonate mineralisations yield Middle Pleistocene ages (from 268 to 189 ka BP), with a 10-15-ka cyclicity that we link to the coseismic rejuvenation of the structural permeability in the fault zone. We propose that fault-related mineralisations recorded the interactions among tectonic deformation and climate during the Quaternary. Our study is the first documentation of fault-controlled recurrence intervals in fluid infiltration in a seismically active fault of central Apennines.

Groundwater age can differ when determined by radioactive tracers due to different retardation factors. According to Krishnawami et al. 1982, Radon isotopes supply to groundwater is considered as a measure of the supply of Radium isotopes. This assumption considerably affects the estimation of the Ra retardation factor. Briganti et al. 2020 reports how the different groundwater supply mechanisms of Ra and Rn should be considered in order to avoid a relevant variation between the real water residence time and the age calculated. In the same work an alternative method for estimating Ra retardation factor is proposed without using Rn data as a comparison term. A synthesis of the main results of laboratory tests is presented in order to describe possible applications of the method. References Briganti A., Voltaggio M., Tuccimei P. & Soligo M. 2020. Radium in groundwater hosted in porous aquifers: estimation of retardation factor and recoil rate constant by using NAPLs. SN Appl. Sci. 2, 1934 (2020). https://doi.org/10.1007/s42452-020-03610-4 Krishnaswami S., Graustein W.S., Turekian K.K., Dowd J.F. 1982. Radium, thorium and radioactive lead isotopes in groundwaters: application to the in situ determination of adsorption-desorption rate constants and retardation factors. Water Resour. Res. 18:1633–1675.

The Neogene to Quaternary southern Apennines mountain belt is flanked to the SW by the Tyrrhenian Sea back-arc basin, which was formed since late Miocene times. Extensional tectonics related to back-arc basin formation affected the Tyrrhenian margin of the southern Apennines since the Quaternary with formation of a series of horst and graben structures. Huge amounts of existing surface, subsurface and offshore data indicate that subsidence on the order of thousands of metres affected the grabens, and remarkable flights of marine terraces are indicative of Quaternary uplift of the horst blocks. The highest and older marine terraces, Early Pleistocene in age, occur up to several hundreds of metres above the sea level. A huge number of former studies have provided fundamental data on both the outcropping (raised) and buried paleoshorelines and littoral deposits, the chronological framework for the identified relative sea level fluctuations mostly rests on local-scale relative chronology reconstructions constrained by dating that are still quite rare and sparse. Detail-scale geomorphological-geological mapping, integrated with Quaternary stratigraphy, aimed at the recognition, characterisation and dating of raised marine terraces and paleoshorelines (tidal notches, platform inner edges) has been carried out in several key areas of the southern Apennines Tyrrhenian Sea margin, from Campania, in the North, to northern Calabria, in the South. The field surveys have been carried out both in rocky coasts (where continental deposits cover and sometimes hide the paleoshorelines) and in the two main alluvial-coastal basins, namely the Campania and Sele River plains. The new geochronological data constrain the ages of several late Middle Pleistocene to Late Pleistocene sea level markers, allowing a better definition of the vertical motions in each study area. Overall, the time-space distribution of the vertical motions on the regional scale is better reconstructed, along with the framework of the Quaternary surface uplift of the southwestern slope of the southern Apennines mountain belt.

Raised paleoshorelines were detected in the eastern margin of the Campania Plain, which is one of the largest coastal basins in the Tyrrhenian back-arc basin system associated with the Neogene to Quaternary Apennine orogen. The paleoshoreline remnants crop out at variable elevations at several sites, including quarry cuts, which provide excellent 3D exposures of the coastal landforms and deposits, the associated continental sediments and faults dissecting those landforms and deposits. Based on the integration of geomorphological, stratigraphic, micropaleontological and facies analyses with structural data, we reconstructed shoreline development in response to erosional/depositional processes governed by relative sea level change in the framework of coeval extensional tectonics. Most of the paleoshoreline remnants are assigned to three displaced marine terraces that, based on new U-series dating, are related to the late part of the Middle Pleistocene. The faults offsetting the marine terraces (namely, E-W striking normal faults and NNW striking transfer faults) are interpreted as part of a single, segmented extensional fault system controlled by roughly N-S to NNW-SSE horizontal extension. The identified extensional system, being consistent with the regional structure imaged by seismic data, represents the first field evidence of the tectonics controlling the formation of the Campania Plain basin. Our results, providing new direct evidence that effectively complements the large amount of existing subsurface datasets, allow for a significant step forward in the understanding of the tectonic and sedimentary processes governing the Quaternary development of the Tyrrhenian back-arc basin margin.