Radon gas is considered a significant hazard to human health due to its radioactive character and its relationship with lung cancer. In response, national and international organizations have developed regulations to reduce radon exposure in indoor environments. In this study, novel nanocomposites based on styrene-butadiene-styrene (SBS) copolymers and bitumen were developed by incorporating two-dimensional (2D) nanomaterials to create effective physical barriers against radon gas. The resulting materials were evaluated for potential application in the building sector to mitigate radon permeation. The best-performing formulations achieved radon diffusion coefficients on the order of 10-12 m2/s, below the limit established by European Directive 2013/59/EURATOM for radon barrier materials. Mechanical and physical characterization confirmed that the incorporation of nanofillers did not significantly alter the properties of the SBS-bitumen matrix. Overall, the developed nanocomposites exhibit promising performance as functional barrier materials for reducing indoor radon exposure and improving building health safety.

Radon is a naturally occurring radioactive gas that accumulates inside poorly-ventilated environments, posing significant health risks due to its association with lung cancer. This study analyzes indoor radon dynamics in a building located within a former uranium mine in Saelices el Chico (Spain), evaluating the effectiveness of natural and mechanical ventilation for radon mitigation. Experimental measurements were conducted to monitor radon levels over time, supported by a CFD model that simulated both indoor and outdoor environments while accounting for terrain-induced wind effects. This modeling approach improved boundary condition accuracy, revealing up to 20% discrepancies between raw meteorological data and simulated environments. A seasonal analysis was performed under representative weather conditions and compared with a forced ventilation scenario using an industrial fan to continuously supply fresh air. The mechanical ventilation model showed strong agreement with experimental results. Findings indicate that mechanical ventilation substantially enhances air renewal-reaching up to 2.21 air changes per hour (ACH)-whereas natural ventilation only provides 0.13-0.25 ACH, corresponding to renewal times between 4 and 8 hours. As a result, simulated radon concentrations inside the studied room dropped from over 10,000 Bq/m3 under natural conditions to about 2,000 Bq/m3 within just one hour after implementing the mechanical setup. These findings demonstrate the critical role of mechanical ventilation in reducing radon accumulation and improving indoor air quality, particularly in buildings with limited openings, suboptimal airflow paths, or low wind conditions where natural ventilation becomes ineffective.

Within the Preventive Conservation Plan framework established for the Cave of Altamira, the continuous monitoring of environmental variables constitutes one of the focal points for preserving the parietal art contained therein. This paper presents new aspects of the ventilation of the Cave of Altamira derived from detecting short-period thermal fluctuations observed in different areas inside the cave. For 2021 and 2022, there are periods with daily air temperature oscillations, mainly in the summer and early autumn, corresponding to day/night thermal variations. The concentration of CO2 was considered as a passive tracer to investigate air exchange dynamics. We observed temporally correlated fluctuations in CO2 levels across three interior rooms (Hall, Crossing, and Polychromes Room). This pattern suggests the influence of a shared ventilation pathway or a common driver of gas exchange with the exterior. The correlations between these fluctuations and the variations of the indoor/outdoor air thermal gradient in each area indicate that these gradients could explain, to a large extent, the variations of CO2 concentration during the period analysed. These results allow us to know more precisely the behaviour of the concentration of this gas inside the cave and to better characterise the cave's ventilation.

The protection of first responders from radioactive contamination with alpha emitters that may result from a radiological accident is of great complexity due to the short range of alpha particles in the air of a few centimeters. To overcome this issue, for the first time, a system mounted on a UAS for the near-real-time remote measurement of alpha particles has been developed, tested, and calibrated. The new system, based on an optical system adapted to be installed on a UAS in order to measure the UV-C fluorescence emitted by alpha particles in the air, has been tested and calibrated, carried out in the laboratory and in field experiments using UV-C LEDs and 241Am sources. In experimental flights, the probability of detecting a point source was determined to be approximately 60%. In the case of a surface extended source, a detection efficiency per unit surface activity of 10 counts per second per MBq cm−2 was calculated. A background count rate of UV-C of around 26 ± 28 s−1 for an integration time of 0.1 s was measured during flights, which led to a decision threshold surface activity of 5 MBq cm−2.

A comparison of low-cost radon monitors was conducted at the Laboratory of Natural Radiation (LNR). The monitors we evaluated were EcoQube, RadonEye, RadonEye Plus2, Spirit, ViewPlus, ViewRadon and WavePlus. An AlphaGUARD monitor calibrated at the Laboratory of Environmental Radioactivity of the University of Cantabria (LaRUC), accredited for testing and calibration according to ISO/IEC 17025, provided the reference value of radon concentration. The temporal stability of the monitors was studied, obtaining a percentage of missing records ranged from 1% to 19% of the data. The main technical characteristics studied were temporal stability, measurement ranges, accuracy, correlation and response time. The main results show that the measurement ranges align with those specified by their manufacturers, with percentage differences with respect to the reference monitor of between 5% and 16%. The diversity found for response time is remarkable, with values ranging from 1 to 15 h, with Pearson correlation factors between 0.63 and 0.90.

Pile dwelling sites in Mediterranean lakes face increasing threats to their conservation and safeguarding from climate change and its associated impacts. The primary objective of this study is to investigate the influence of climate change and water table fluctuations on the preservation of archaeological layers, with a particular focus on organic layers and wooden remains. Based on a combination of lake water level fluctuation analysis, water table measurements, and stratigraphic data, we managed to gauge the effects of recent water table fluctuations on the preservation of the occupation levels at the Neolithic site of La Draga (Lake Banyoles). By simulating and analysing the relationship between water table levels and their effects on the stratigraphic sequence, we were able to identify areas that are most susceptible to the impact of water table fluctuations and therefore potential post-depositional processes. Moreover, statistical analysis of recent hydrological data has shown that there is a direct relationship between lake level and water table at the settlement. This would have been a factor affecting the preservation of both artefacts and deposits since the occupation of La Draga. Thus, the importance of considering hydrological factors when analysing and interpreting lakeside archaeological sites is highlighted.

Radon gas is the largest source of public exposure to naturally occurring radioactivity.Radon activity concentration maps, based on atmospheric measurements, as well as radon flux maps can help Member States to comply with the EU Council Directive 2013/59/Euratom and, particularly, with the identification of Radon Priority Areas.Radon can also be used, as a tracer, to improve Atmospheric Transport Models and to indirectly estimate greenhouse gas (GHG) fluxes.This is important for supporting successful GHG mitigation strategies.One approach to estimate GHG fluxes on local to regional scale is the socalled Radon Tracer Method (RTM), which is based on the night-time correlation between atmospheric concentrations of radon and GHG measured at a given station together with information on the radon flux data within the station footprint.Thus, atmospheric monitoring networks are interested or are already measuring atmospheric radon activity concentrations using different techniques but a metrological chain to ensure the traceability of all these measurements was missing.Since 2020 a large consortium engaged in the project traceRadon [1] to develop the missing traceability chains to improve the respective sensor networks http://traceradon-empir.eu/ .This paper presents results in the areas: Novel 226 Ra standard sources with continuous controlled 222 Rn emanation rate, radon chambers aimed to create a reference radon atmosphere and a reference field for radon flux monitoring.The achieved results are making new calibration services far beyond the state of art possible.

The noble and radioactive gas radon is well known to be the most important source of public exposure to natural environmental radioactivity in indoor environments (workplaces, homes, etc.). Consequently, it is important to identify radon-prone areas, where radon fluxes are high, and also to develop and apply mitigation measures when radon activity concentrations of indoor areas exceed guideline values.However, radon is also known by the climate and atmospheric research communities to be a useful environmental tracer and it is nowadays being used in several studies such as the improvement of atmospheric transport models or the indirect estimation of GHG fluxes by the Radon Tracer Method. These previous applications will benefit from the availability of radon flux maps.Stakeholders and scientists involved in radiation protection and climate analysis may benefit from reliable continuous radon flux measurements to validate and improve existing and future radon flux maps. In the framework of the project traceRadon (EMPIR reference 19ENV01) a full metrology chain has been designed and built for radon flux measurements.The work and the challenges related to this type of measurement will be presented here together with possible guidelines for carrying out continuous radon flux measurements in the field.

Since 2020 a large consortium has been engaged in the project EMPIR 19ENV01 traceRadon to develop the missing traceability chains to improve the sensor networks in climate observation and radiation protection. This paper presents results in the areas of: Novel 226Ra standard sources with continuous controlled 222Rn emanation rate, radon chambers aimed to create a reference radon atmosphere and a reference field for radon flux monitoring. The major challenge lies in the low activity concentrations of radon in outdoor air from 1 Bq∙m-3 to 100 Bq∙m-3, where below 100 Bq∙m-3 there is currently no metrological traceability at all. Thus, measured values of different instruments operated at different locations cannot be compared with respect to their results. Whin this paper, new infrastructure is presented, capable of filling this gap in traceability. The achieved results make new calibration services, far beyond the state of art, possible.

As part of a contract with ENRESA (National Radioactive Waste Company S.A. is a Spanish public company responsible for the management of radioactive waste), after the closure of the uranium mill factory in Andújar, Spain, continuous measurements of the radon flux have been carried out on an annual basis using activated carbon detectors following a methodology established in our laboratory (ISO 11665-7, 2012). The results obtained and their usefulness are presented from the point of view of control of the closure conditions established by the competent authority in order to minimize the impact of the site on the environment.

High-quality, long-term measurements of terrestrial trace gas emissions are important for investigations of atmospheric, geophysical and biological processes to help mitigate climate change and protect the environment and the health of citizens. High-frequency terrestrial fluxes of the radioactive noble gas Rn-222, in particular, are useful for validating radon flux maps and used to evaluate the performance of regional atmospheric models, to improve greenhouse gas emission inventories (by the radon tracer method) and to determine radon priority areas for radiation protection goals.A new automatic radon flux system (Autoflux) was developed as a transfer standard (TS) to assist with establishing a traceability chain for field-based radon flux measurements. The operational characteristics and features of the system were optimized based on a literature review of existing flux measurement systems. To characterize and calibrate Autoflux, a bespoke radon exhalation bed (EB) facility was also constructed with the intended purpose of providing a constant radon exhalation under a specific set of controlled laboratory conditions. The calibrated Autoflux was then used to transfer the derived calibration to a second continuous radon flux system under laboratory conditions; both instruments were then tested in the field and compared with modeled fluxes.This paper presents (i) a literature review of state-of-the-art radon flux systems and EB facilities; (ii) the design, characterization and calibration of a reference radon EB facility; (iii) the design, characterization and calibration of the Autoflux system; (iv) the calibration of a second radon flux system (INTE_Flux) using the EB and Autoflux, with a total uncertainty of 9 % (k = 1) for an average radon flux of similar to 1800 mBq m-2 s-1 under controlled laboratory conditions; and (v) an example application of the calibrated TS and INTE_Flux systems for in situ radon flux measurements, which are then compared with simulated radon fluxes. Calibration of the TS under different environmental conditions and at lower reference fluxes will be the subject of a separate future investigation.

In cave environments, water vapor condensation occurs naturally when warmer/wet air masses flow close to colder cave surfaces. Artificial microclimate perturbations in show caves can enhance this process, leading to potential deterioration of rock art and degradation of speleothems. Here we investigate the triple oxygen and hydrogen isotopic compositions of condensation water in Altamira Cave (Cantabria, northern Spain) to evaluate the potential of stable isotopes in the study of condensation mechanisms in caves. We assess the role of cave ventilation in the spatiotemporal isotopic variability of condensation water in Altamira Cave. To this end, water drops that condense naturally on artificial supports in different parts of the cave were collected for 7 years and their isotopic compositions (delta O-17, delta O-18, SD and derived parameters O-17-excess and d-excess) were compared to those of droplets with no apparent dripping taken from the cave ceiling (i.e. presumably condensation water) and fast dripping points (i.e. infiltration water) during the same period. Condensation waters in the outmost cave sectors, closer to the entrance, show higher delta O-17, delta O-18 and SD values during the cave ventilation period (June to October) compared to the rest of the year. This seasonal pattern can be explained by changes in the contributions of two moisture sources for condensation: advection of allochthonous water vapor from outside during the cave ventilation period and recycling of autochthonous vapor generated from cave dripwater during the stagnation period. In contrast, the isotopic values of condensation waters in the inner cave sectors are similar to those of infiltration water, with insignificant seasonal variability. This suggests that water condensation in the inner cave sectors is sourced by autochthonous vapor, with no significant contributions of external moisture, even during the cave ventilation period. We conclude that allochthonous water vapor condenses preferentially in the Entrance Hall and does not affect significantly the rest of the cave. These results are relevant for the management of Altamira Cave and for future investigations on condensation mechanisms in cavities elsewhere.

Radon flux measurements provide information about how much radon rises from the ground toward the atmosphere, thus, they could serve as good predictors of indoor radon concentrations. Although there are many different mapping methods with many different input data, radon flux data are generally missing and are not included for the delineation of radon priority areas (RPA). The aim of this literature review is to investigate to what extent radon flux was used, or could be used, for the delineation of RPAs. Numerous factors influencing radon flux were identified, but quantifying their contribution to radon flux measurement still remains a challenge. Different methods and measuring devices were used for the determination of radon flux, thus it is necessary to identify possible inconsistencies in order to harmonise different radon flux measurements. Due to the complexity of radon flux measurements, only two countries were identified to have performed national surveys on outdoor radon, which were of much smaller scale compared to those on indoor radon. A positive correlation between radon flux and radon quantities, such as radon in soil gas and indoor radon, indicates that radon flux could be used as an input parameter for the estimation of RPA. By reviewing radon flux models, it was concluded that up-to-date modelled radon flux maps have reached excellent spatial resolution and will be further improved, hence, they could serve as an input for the estimation and delineation of RPA.

Radon (222Rn), a radioactive gas of natural origin, was listed by the World Health Organization in 2009 as the second largest cause of lung cancer (3–14%) after tobacco. Global awareness of the importance of controlling its concentration in water led to the implementation of the European Directive 2013/51/Euratom, which establishes permitted levels in drinking water. This study applies a mathematical model to determine 222Rn concentration in water supplying an artificial aquifer over the full range of recharge/discharge conditions (volumes and times, and therefore flows). This was done by creating an artificial aquifer on a laboratory scale, which reproduces the recharges and discharges experienced by real aquifers through rainwater or groundwater. The equipment used in this study was an RTM 2100 with a specific system for continuous monitoring of 222Rn in water, a high-purity Ge detector for gamma spectrometry, and a portable liquid scintillation counter (LSC) called Triathler for specific measurements of 222Rn in water. The aim of this paper is to show the application of the mathematical model under different recharge/discharge conditions applied to the artificial aquifer. The concentration of 222Rn in water determined by the model can also be used as a tracer to find the origin and volume of water that reaches a real aquifer.

Doses from the exposure to outdoor radon are typically an order of magnitude smaller than those from indoor radon, causing a greater interest on investigation of the latter for radiation protection issues. As a consequence, assessment of radon priority areas (RPA) is mainly based on indoor radon measurements. Outdoor radon measurements might be needed to guarantee a complete estimation of radiological risk and may help to improve the estimation of RPA. Therefore, authors have analysed the available literature on outdoor radon to give an overview of outdoor radon surveys and potential correlation with indoor radon and estimation of RPA. The review has shown that outdoor radon surveys were performed at much smaller scale compared to indoor radon. Only a few outdoor radon maps were produced, with a much smaller density, covering a larger area, and therefore putting doubt on the representativeness of this data. Due to a large variety of techniques used for outdoor radon measurements and requirement to have detectors with a high sensitivity and resistance to harsh environmental conditions, a standardised measurement protocol should be derived. This is no simple endeavour since there are more applications in different scientific disciplines for outdoor radon measurements compared to indoor radon.

Interlaboratory exercises are a good tool to compare the response of different systems to the same quantity and to identify possible inconsistencies between them. One of the main goals of the EMPIR 19ENV01 traceRadon project is to harmonize radon flux measurements based on different systems and methodologies. In the framework of the traceRadon Project, two radon flux intercomparison campaigns were carried out in October 2021 at high and at low radon source areas. Four institutions participated in the field intercomparison exercises with their own systems. Every system was based on a specific radon monitor (diffusion or pump mode) and an accumulation chamber (with manual or automatic opening). Radon fluxes were calculated by each participant using both exponential and linear fittings of the radon activity concentration measured over time within the accumulation chambers. The results of this study show mainly: (i) the exponential approach is not advisable due to the variability of the radon flux and the leakage of the systems during long-time measurements; (ii) the linear approach should be applied to minimize the measurement period in agreement with the time response and sensitivity of the monitors; (iii) radon flux measured at high radon source areas (radium content of about 800 Bq kg−1) risks being underestimated because of the influence of advective effects; (iv) radon flux measured at low radon source areas (radium content of about 30 Bq kg−1) may present large uncertainties if sensitive radon monitors with pump mode are not used.

A study is presented on rapid episodes of air exchange in the Polychrome Room of the Altamira Cave (Cantabria, Spain) using continuous monitoring of radon and CO2 tracer gases, as well as environmental parameters such as internal and external air temperature. For this, criteria have been developed to carry out an inventory of these types of events during the 2015–2020 period. Most of the degassing-recharging events occur over several hours or days, especially during spring and autumn. This means that the room can be significantly ventilated during these short periods of time, posing an exchange of energy and matter with potential impact in the preservation of the rock art present inside. In addition, the hypothesis that temperature gradients between the internal and external atmosphere is one of the main factors that induces degassing has been tested. To this end, correlation analysis has been carried out between the different magnitudes involved in this study, such as radon and CO2 concentrations, and air temperature gradients. A total of 37 degassing-recharging events have been analyzed for the 5 year studied period. The distribution of the duration of the events have been described, as well as that of the correlations between the degassing and recharge stages of each event, showing significant values of r coefficients for the correlation with temperature gradients between the internal and external atmosphere.

Generally, high-quality and long-term measurements of gas fluxes from soil are required to investigate atmospheric, geophysical and biological processes needed to protect the climate, the environment and the health of citizens. In particular, high-frequency flux measurements of the radioactive noble gas 222 Rn from soils may be useful for validating radon flux maps and models used by the radiation protection community to determine Radon Prone Areas and by the climate community to improve greenhouse gas emission inventories using the Radon Tracer Method. For the first time ever, the EMPIR 19ENV01 project traceRadon provides the complete necessary infrastructure and metrology chain for radon flux observations. This infrastructure consists of: i) a 222 Rn Exhalation Bed (EB) facility to provide reference radon fluxes under controlled laboratory conditions; ii) a Transfer Standard (TS) instrument to be calibrated using the EB and used as a reference monitor for in situ measurements; and iii) inter-comparison campaigns of radon flux systems under in situ environmental conditions. The first two of these products were designed and built after a literature reviews of current devices and requirements. Here we present the design and characterization, both theoretical and experimental, of a 222 Rn EB facility and a TS instrument and their application to calibrate radon flux systems with a total uncertainty of 9 % (k=1) for an average radon flux of about 1800 mBq m -2 s -1 . The full calibration protocol is also presented together with the guidelines to select a radon flux system and use it for in situ field campaigns.

An interlaboratory comparison for European radon calibration facilities was conducted to evaluate the establishment of a harmonized quality level for the activity concentration of radon in air and to demonstrate the performance of the facilities when calibrating measurement instruments for radon. Fifteen calibration facilities from 13 different European countries participated. They represented different levels in the metrological hierarchy: national metrology institutes and designated institutes, national authorities for radiation protection and participants from universities. The interlaboratory comparison was conducted by the German Federal Office for Radiation Protection (BfS) and took place from 2018 to 2020. Participants were requested to measure radon in atmospheres of their own facilities according to their own procedures and requirements for metrological traceability. A measurement device with suitable properties was used to determine the comparison values. The results of the comparison showed that the radon activity concentrations that were determined by European calibration facilities complying with metrological traceability requirements were consistent with each other and had common mean values. The deviations from these values were normally distributed. The range of variation of the common mean value was a measure of the degree of agreement between the participants. For exposures above 1000 Bq/m3, the variation was about 4% for a level of confidence of approximately 95% (k=2). For lower exposure levels, the variation increased to about 6%.