Suchergebnisse

Experimental tests in the cabinet carried out at the University of Oxford were financially supported by the European Commission under the Marie Curie program (FP7-PEOPLE-2012-IEF call, research project "NaturaLime"). This research has been supported by the Spanish Government (MICINN) (PID2020-116896RB-C21 and PID2020-116896RB-C22). ; This research focuses on the analysis of the influence of two secondary salt weathering processes on the durability of rocks exposed to marine environments: chemical dissolution of rock forming minerals and differential thermal expansion between halite and the hosting rock. These processes are scarcely treated in research compared to salt crystallisation. The methodology followed in this paper includes both in situ rock weathering monitoring and laboratory simulations. Four different calcite-bearing rocks (a marble, a microcrystalline limestone and two different calcarenites) were exposed during a year to a marine semiarid environment. Exposed samples show grain detachment, crystal edge corrosion, halite efflorescences and microfissuring. Crystal edge corrosion was also observed after the laboratory simulation during a brine immersion test. Calcite chemical dissolution causes a negligible porosity increase in all the studied rocks, but a significant modification of their pore size distribution. Laboratory simulations also demonstrate the deterioration of saltsaturated rocks during thermal cycles in climatic cabinet. Sharp differences between the linear thermal expansion of both a pure halite crystal and the different studied rocks justify the registered weight loss during the thermal cycles. The feedback between the chemical dissolution and differential thermal expansion, and the salt crystallisation of halite, contribute actively to the rock decay in marine environments. ; European Commission European Commission Joint Research Centre ; Spanish Government PID2020-116896RB-C21 PID2020-116896RB-C22

This research focuses on the analysis of the influence of two secondary salt weathering processes on the durability of rocks exposed to marine environments: chemical dissolution of rock forming minerals and differential thermal expansion between halite and the hosting rock. These processes are scarcely treated in research compared to salt crystallisation. The methodology followed in this paper includes both in situ rock weathering monitoring and laboratory simulations. Four different calcite-bearing rocks (a marble, a microcrystalline limestone and two different calcarenites) were exposed during a year to a marine semiarid environment. Exposed samples show grain detachment, crystal edge corrosion, halite efflorescences and microfissuring. Crystal edge corrosion was also observed after the laboratory simulation during a brine immersion test. Calcite chemical dissolution causes a negligible porosity increase in all the studied rocks, but a significant modification of their pore size distribution. Laboratory simulations also demonstrate the deterioration of salt-saturated rocks during thermal cycles in climatic cabinet. Sharp differences between the linear thermal expansion of both a pure halite crystal and the different studied rocks justify the registered weight loss during the thermal cycles. The feedback between the chemical dissolution and differential thermal expansion, and the salt crystallisation of halite, contribute actively to the rock decay in marine environments. ; Experimental tests in the cabinet carried out at the University of Oxford were financially supported by the European Commission under the Marie Curie program (FP7-PEOPLE-2012-IEF call, research project "NaturaLime"). This research has been supported by the Spanish Government (MICINN) (PID2020-116896RB-C21 and PID2020-116896RB-C22).

Uniaxial compressive strength (UCS) is the most used parameter to measure rock strength. However, restrictions in sampling large volume of material, the need of very large set of results and onsite characterisation of UCS non-destructively are requirements in many scientific and engineering investigations. The estimation of UCS from a single non-destructive or minimally invasive technique (NDT) may result incomplete because each NDT is sensitive to different compositional and textural factors. This paper combines open porosity, P-wave velocity, Leeb hardness and micro-drilling resistance force to estimate USC for a wide range of carbonate sedimentary rock types with different petrographic characteristics. Results reveal that mineralogical composition significatively affects micro-drilling resistance force profiles and P-wave velocity values, especially for quartz-bearing rocks. In addition, texture controls substantially the reproducibility of tests sensible to rock surface properties, such as Leeb hardness and micro-drilling resistance force. Fifteen simple and multiple expressions for UCS are fitted. Linear expressions have shown better coefficients of determination (R2) than non-linear equations because of the linearity shown by individual parameters. Curve fitting improves as the number of petrophysical parameters increase in the multiple linear regression analysis. The best correlation is found when the equation incorporates all the mechanical parameters obtained non-destructively as well as open porosity (R2 = 0.910). Leeb hardness is always the most significant variable of the fitted regressions and its addition into multiple linear equations causes an increase of R2. Open porosity also improves R2 whereas drilling force and P-wave velocity have a lower statistical weight in the expressions. The UCS estimation from all NDT, without considering open porosity, shows a good correlation (R2 = 0.899), which presents the advantage that they can be obtained non-destructively with portable equipment and can provide a numerous set of results at relatively low cost. ; This work was supported by the Spanish Government [grant number RTI2018-099052-B-I00] and Regional Government of Madrid (Spain) [Top Heritage, grant number S2018/NMT-4372].

Fire is a major decay agent of rocks and can generate immediate catastrophic effects as well as directional and anisotropic damage that affect long-term weathering processes. Temperature increase is the most relevant factor, among other components in a fire, generating mineral transformations and bulk mechanical damage. Mineralogical changes at high temperatures are key to understanding the overall mechanical behaviour. However, most studies to date were carried out after rock specimens were heated to a target temperature and cooled down to room temperature. Therefore, these studies are missing the observation of the actual mineral processes during heating. This paper aims to compare mineralogical changes in crystalline rocks during heating by means of XPS and different XRD techniques. Samples of four different granitoids were heated to several temperatures up to 1000 °C to evaluate their chemical and structural changes. Results show how standardised thermal expansion coefficients are not a suitable indicator of the bulk effect of high temperatures on rocks. Results also show how thermal expansion estimations from XRD lattice measurements may be an alternative to bulk dilatometric tests, as they can be performed with limited sampling, which may be necessary in some studies. Nevertheless, XRD and XPS results need to be interpreted carefully in relation to the bulk effects of temperature increase in the rocks, as the structural behaviour may seemingly contradict the macroscopic effect. ; This research was funded by "Top Heritage (P2018/NMT-4372) programme from the Regional Government of Madrid (Spain)", "Grants PIC2020-116896RB-C21", "PIC2020-116896RB-C22" funded by MCIN/AEI/ 10.13039/501100011033," Grant AICO/2020/175" by the Regional government of Comunidad Valenciana (Spain).

Radon is a radioactive gas produced from the natural radioactive decay of uranium and is found in almost all rocks and soils. In confined places (e.g., dwellings, workplaces, caves, and underground mines), radon may accumulate and become a substantial health risk since it is considered the second most important cause of lung cancer in many developed countries. Radon risk assessment commonly considers either field or estimate values of the radon concentration and the gas permeability of soils. However, radon risk assessment from single measurement surveys to radon potential largescale mapping is strongly sensitive to the soil texture variability and climate changes, and particularly, to the soil water content dynamic and its effect on soil gas permeability. In this paper, the gas permeability of soils, and thus, the estimation of radon risk, is studied considering the effect of three different climates following the Köppen classification and four soil textures on soil water content dynamics. This investigation considers the CLIGEN weather simulator to elaborate 100-year length climatic series; Rosseta 3 pedotransfer function to calculate soil hydraulics parameters, and the HYDRUS-1D software to model the dynamics of water content in the soil. Results reveal that climate strongly affects gas permeability of soils and they must be considered as an additional factor during the evaluation of radon exposure risk. The impact of climate and texture defines the soil water content dynamic. Coarse soils show smaller gas permeability variations and then radon risk, in this case, is less affected by the climate type. However, in clay soils, the effect of climate and the differences in soil water content derive in gas permeability variations between 100 and 1,000 times through an annual cycle. As a result, it may cross the boundary between two radon risk categories. Results deeply confirm that both climate and texture should be compulsory considered when calculating the radon exposure risk and in the definition of new strategies for the elaboration of more reliable geogenic radon potential largescale maps. ; This work was supported by the Spanish Ministry of Science, Innovation, and Universities [grant number RTI2018-099052-BI00] and Regional Governments of Comunidad Valenciana (Spain) [grant number AICO/2020/175]. A pre-doctoral research fellowship (PRE2019-088294) was awarded to SG-O for the project RTI2018-099052-BI00.

Heavy-metal sources in urban environments include automobile exhaust, fuel combustion, tires, road asphalt, weathering of building materials, and/or industrial activities. The presence of heavy metals in urban stormwaters constitutes a potential risk for water resources and aquatic life. Results from the present study demonstrated the effectiveness of two different lightweight aggregates (LWAs), Arlita and Filtralite, to remove heavy metals (Ni, Cu, Zn, Cd, and Pb) present in aqueous solutions. These materials were selected because they previously showed great results for water treatment and because of their physicochemical properties. The removal efficiency of the studied materials was evaluated with batch tests containing solutions contaminated with heavy metals (with individual and multiple contaminants) at different concentrations mixed with the LWA particles. Filtralite showed a better performance in heavy metal removal than Arlita: higher adsorption capacity for all metals, and lower release of metals from contaminated particles into washing water. The average removal capacities in tests developed with solutions containing individual contaminants for Arlita and Filtralite were 76% and 90%, respectively, although the values varied across the different contaminants. Metal elimination by LWAs was more effective with individual contaminated solutions than with multielemental ones. The analysis of the adsorption curves, the mineral precipitation on the LWA surface, and the geochemical modeling confirmed that two different mechanisms are responsible for the heavy-metal removal. First, the rough surface of the LWA presents sorbing surface sites of the forming minerals, resulting in the ion-exchange reactions of metal ions. Second, the LWA–water interaction causes an increase in solution pH, which triggers the precipitation and coprecipitation of the metals in the form of oxide and hydroxides. The study confirms that the use of Arlita and especially Filtralite present promising potential to remove heavy metals from urban stormwaters. ; This research was funded by the University of Alicante under the project GRE17-12, Generalitat Valenciana under the project GV/2020/059 and the Spanish Government under the project RTI2018-099052-B-I00.

Radon is a natural source of radioactivity and it can be found in all soils and rocks in the Earth. The presence of radon gas in indoor environments implies a serious risk for human health, already listed as carcinogenic by the World Health Organization. The most relevant methods to infer the risk for radon exposure are based on soil radon concentration and gas permeability that describe the effective radon movement in the soil. However, they neglect crucial soil properties and water content in soil, which can affect greatly soil permeability to gases. Additionally, soil permeability measurement remains expensive, difficult and time-consuming. In this paper we show a new and simple methodology to infer radon risk based on Rosetta3 pedotransfer function as well as soil texture and water content. We also determine the influence of soil texture both on the gas permeability variation in dependence on water content and on the parameter n of the van Genuchten –Mualem model, which establishes the shape of the relative permeability curves. We show that radon risk exposure may change importantly for the same soil with different soil water contents. We finally apply and validate the proposed method using radon permeability data from the Canadian component of the North American Soil Geochemical Landscapes Project (NASGLP). Results highlight that the proposed methodology provides reliable estimations of the gas permeability and reveal that the presence of water content may cross the boundary between two radon risk categories, and consequently, may change the radon risk category to safer situations. ; This work was supported by the Spanish Government [grant number RTI2018-099052-B-I00] and the University of Alicante [grant number GRE17-12].

In the westernmost Tethys, the Early Jurassic involved critical environmental changes affecting marine ecosystems. Brachiopods were particularly affected in the South-Iberian Palaeomargin. A late Sinemurian-early Pliensbachian tectonic event led to the collapse of shallow platforms related to the Atlantic Ocean opening. Subsequently, the early Toarcian Extinction Event occurred during a carbon cycle perturbation and the development of oxygen-depleted conditions, mainly affecting benthic communities. In the Subbetic Domain, brachiopod dynamics concur with these major environmental perturbation events. Geochemical imprint of brachiopod shells from this area has been analyzed revealing a clear synchrony between oscillations of trace elements content, global trends in the C and O cycling, and faunal diversity dynamics around critical bioevents, allowing to validate global and regional models related to the platform collapse and the early Toarcian biotic crisis. In the Sinemurian-Pliensbachian turnover and the Toarcian crisis, the redox-sensitive trace metals, REEs, and Fe content in the brachiopod shells show positive excursions. Nevertheless, their trend together with brachiopod diversity patterns, the lower TOC values, and the sedimentary data, support that oxygen depletion must have played a secondary role as environmental stress factor for the benthic fauna. Instead, an increasing temperature gradient is invoked to have played a decisive role, as demonstrated by the main faunal turnover and replacement events correlating with the palaeotemperatures from the peri-Iberian platforms. Shifts on palaeoproductivity, continental influx, and hydrothermal input are also deduced by the increasing concentrations of several trace elements, interpreted as complementary triggering factors of these Early Jurassic bioevents in the westernmost Tethys Ocean. ; En el Jurásico Inferior se registran diversos eventos críticos que influyeron significativamente en los ecosistemas marinos del Tethys occidental. Entre las comunidades bentónicas, en el Paleomargen Sudibérico, los braquiópodos se vieron particularmente afectados por dichos eventos. El episodio tectono-sedimentario distensivo asociado a la apertura del proto-Atlántico conllevó el colapso de las amplias plataformas someras imperantes en el Tethys hasta el Sinemuriense superior-Pliensbaquiense basal, con la consiguiente reorganización de los ecoespacios faunísticos. Posteriormente, el evento de extinción registrado en el Toarciense inferior, trajo consigo importantes alteraciones en el ciclo del carbono así como el desarrollo de condiciones anóxicas que afectaron principalmente a las comunidades bentónicas. En el dominio Subbético, la dinámica poblacional de los braquiópodos coincidió con estos importantes eventos de perturbación ambiental. Se ha analizado la impronta geoquímica registrada en conchas de braquiópodos del Subbético oriental, revelando una clara sincronía entre las oscilaciones del contenido en elementos traza, las tendencias globales en el ciclo del C y del O y la diversidad de la braquiofauna en torno a dichos eventos críticos, lo que permite validar modelos globales y regionales relacionados tanto con el evento de rifting incipiente de las plataformas someras en el Sinemuriense-Pliensbachiense, como con la crisis biótica global en torno al Toarciense inferior. En la renovación faunística verificada para el tránsito Sinemuriense-Pliensbachiense y para el evento de extinción del Toarciense, los metales traza sensibles a las condiciones redox, la concentración de REE y el contenido en Fe en las conchas de braquiópodos muestran excursiones positivas. Esta tendencia, junto a los patrones de diversidad de los braquiópodos, los bajos valores de TOC y las evidencias sedimentarias, sugieren que, en esta región, la anoxia debió representar un factor secundario como causa de estrés ambiental para la fauna bentónica. En cambio, se postula que el progresivo aumento de la temperatura jugó un papel determinante en las cuencas marginales del Tethys occidental, como se demuestra al correlacionar los principales eventos de renovación y sustitución faunística con las paleotemperaturas de las plataformas peri-ibéricas. Los cambios en la paleoproductividad, los aportes continentales y posibles contribuciones hidrotermales se relacionan asimismo con las oscilaciones de determinados elementos traza y se interpretan, por tanto, como factores coadyuvantes desencadenantes de estos bioeventos del Jurásico Inferior en el Tethys occidental. ; This research is a contribution to the IGCP-655 (Toarcian Oceanic Anoxic Event: Impact on marine carbon cycle and ecosystems), and was supported by projects CGL2015-66604-R, CGL2015-66835-P and PID2019-105537RB-100 (MINECO, Government of Spain) and P20_00111 (Junta de Andalucía), and the Research Groups VIGROB-167 (University of Alicante) and RNM-200 (University of Jaén).

In this investigation, two different varieties of 'Prada' limestones were studied: a dark grey texture, bearing quartz, clay minerals, organic matter and pyrites, and a light grey texture with little or no presence of such components. We have observed two effects of different intensity when heating the dark texture from 400 °C: (1) the explosion of certain samples and (2) greater thermal damage than in the light grey texture. Chemical and mineralogical composition, texture, microstructure, and physical properties (i.e. colour, open porosity, P and S-wave velocity) have been evaluated at temperatures of 105, 300, 400, and 500 °C in order to identify differences between textures. The violence of the explosive events was clear and cannot be confounded with ordinary splitting and cracking on thermally treated rocks: exploded samples underwent a total loss of integrity, displacing and overturning the surrounding samples, and embedding fragments in the walls of the furnace, whose impacts were clearly heard in the laboratory. Thermogravimetric results allowed the identification of a process of oxidation of pyrites releasing SO2 from 400 °C. This process jointly with the presence of microfissures in the dark texture, would cause a dramatic increase in pore pressure, leading to a rapid growth and coalescence of microcracks that leads to a process of catastrophic decay in rock integrity. In addition to the explosive events, average ultrasound velocities and open porosity showed a greater variation in the dark grey texture from 400 °C. That result also points towards a significant contribution of oxidation of pyrites on the thermo-chemical damage of the rock, among other factors such as the pre-existence of microfissures and the thermal expansion coefficient mismatch between minerals. Implications in underground infrastructure and mining engineering works are critical, as the explosive potential of pyrite-bearing limestones bears risk for mass fracturing and dramatic strength decay from 400 °C. Moreover, SO2 released has harmful effects on health of people and the potential to form acid compounds that corrode materials, shortening their durability and increasing maintenance costs. ; This work was supported by the Spanish Government [Grant number RTI2018-099052-B-I00] and by the Department of Geological and Geotechnical Engineering, Universitat Politècnica de València.

Mokattam limestone is the most frequent building stone used in the cultural heritage buildings in Historic Cairo (Egypt) and it is susceptible to the ongoing effects of salt weathering. A purpose-made simulation chamber was used to test in the laboratory the salt weathering on limestone samples from an active quarry at Helwan area (30 km, south Cairo) at different temperature regimes (20, 30 and 40°C). To assess the extent of the resulted decay, mechanical properties of the fresh quarry and tested samples after different regimes were investigated with non-destructive techniques (P-wave velocity and Leeb rebound hardness) and destructive techniques (uniaxial compression strength). The different mechanical measurements of the tested samples were notably affected after the different temperature regimes. Uniaxial compressive strength is highly correlated with Leeb rebound hardness while P-wave velocity showed a low relevance for the prediction of the strength of the tested samples. ; This study was supported by the Mission Sector of the High Education Ministry, Egypt and the Regional Government of Madrid and the European Social Fund under the project entitled Geomateriales 2 S2013/MIT-2914.

In this paper, we propose a new methodology for the automatic picking of P- and S- wave arrivals. The measurement of elastic wave velocities is crucial for characterisation of the elastic properties of rocks, as well as their physico-mechanical properties and durability. P-waves are easy to generate and acquire, whereas the acquisition and subsequent analysis of the S-waves present major difficulties in most investigations of rocks. In our proposed method the recorded signal is first pre-processed in the wavelet domain, removing low-frequency disturbances and filtering noise. The signal is then analysed in the time-domain to detect and characterise the first pulse and, subsequently, estimate the corresponding onset time. The automatic approach analyses all pulses detected in the output signal and selects the first pulse of the P or S wave relative to symmetry, amplitude and duration criteria. This triple check provides greater confidence in the obtained results. We record P- and S- waveforms through the transmission method for a broad range of sedimentary, igneous and metamorphic rocks used in buildings. Results are compared to manual picking, which is considered as a true or reference value. The recorded signals show that microstructural components of rocks have a strong influence on the output signal. Mineralogical composition, porosity and particle size affect the wave velocity, attenuation, wavelength and waveform, which in turn influences the manual picking of the onset time. The proposed methodology provides precise values of the onset time of P- and S- waves. The discrepancies between automatic and manual P- and S- wave picking are 0.7 and 4.4%, respectively. P-wave signals have a high signal-to-noise ratio and their arrival times are clear and easy to determine. However, the arrival time of S-waves presents significant problems, mainly for medium to coarse-grained rocks. In this case, the output signal is contaminated by P-waves and has a lower signal-to-noise ratio. Besides, propagation of the S-wave through the rock affects the frequency and waveform of the first pulse, which complicates manual picking of the onset time. The developed methodology distinguishes between the S-wave and the remaining P-waves contained in the transversal signal, independently of the skill and subjectivity of a human analyst. ; This work was supported by the Spanish Government [grant number RTI2018-099052-B-I00], Regional Government of Comunidad Valenciana (Spain) [grant number AICO/2016/098] and Madrid (Spain) [Top Heritage, grant number S2018/NMT-4372] and the University of Alicante [grant number GRE17-12]. Predoctoral fellowships were awarded to D. Crespo-Jimenez by the MEFP [FPU2017/04377 and BDNS 311327].

This work discusses the results from a set of physical and mechanical test conducted on 46 cubic samples of a granite from the north of Portugal widely used in local granite-built UNESCO World Heritage, heated in a furnace at temperatures ranging from 105 to 700º C and cooled under different conditions. Then, the obtained results are compared with an extensive database of published case studies, showing that porosity, unit weight, ultrasonic waves velocities, elastic modulus and uniaxial compressive stress variations are mostly related to the induced thermal-stress caused by the anisotropic thermal expansion of the mineral grains. Only mineralogy and specific gravity do not exhibit changes for the studied range of temperatures. For specimens heated to above 500ºC, degradation processes predominate due to alpha-beta phase transition in quartz grains, considerably increasing the linear crack density, length and width and reducing the rock properties. Regarding the influence of the cooling method, thermal effects are amplified when cooling is performed by water immersion because of the inhomogeneous shrinkage and the subsequent tension stress between adjacent particles due to temperature decrease that develop at different pace within the samples. Scanning electron microscopy confirms the increase of damage and the negative effect on the granite properties caused by thermal treatment from 500ºC and by water cooling. For temperatures lower than 500ºC a hardening effect slightly improving elastic modulus and uniaxial compressive strength is observed in slowly and quickly cooled samples. The derived conclusions considerably improve the knowledge about the behaviour against temperature of this type of granite, with the purpose of evaluating the integrity level of granite-built UNESCO cultural heritage of the north of Portugal. ; This work was partially funded by the University of Alicante (vigrob-157 Project, GRE17-011 and UAUSTI18-21, UAUSTI19-25 and UAUSTI20-20 projects), the Regional Governments of Comunidad Valenciana AICO/2020/175, the Spanish Ministry of Economy and Competitiveness (MINECO) and EU FEDER under Project TEC2017-85244-C2-1-P, the Spanish Ministry of Education, Culture and Sport under project CAS17/00392 and the Spanish Ministry of Science, Innovation and Universities project RTI2018-099052-BI00.

This paper combines ultrasonic parameters recorded from P- and S- waves and effective porosity to estimate uniaxial compressive strength, σC, and intrinsic permeability, k - two of the most crucial physical parameters used in stone conservation studies. The ultrasonic parameters have been chosen because they are sensitive to the microstructural properties of stones which influence both σC and k differently. Velocities of compressional or primary, Vp, and shear or secondary, Vs, elastic waves are related to porosity and the mineralogical composition; the waveform attenuation is related to the presence of vuggy macropores and pore and particle size; and the wavelength is related to the pore and particle size. Fifteen types of stones used in the Spanish built heritage were measured including calcarenites, sandstones, dolostones and travertines. Several simple and multiple predictive expressions for σC and k are fitted, which are quantified through the Pearson correlation coefficient, R. Curve fitting improves as the number of petrophysical parameters taken into account in the multiple linear regressions increases. The obtained Pearson's correlations values for σC are slightly higher than for k. The best correlation for σC (R = 0.921) and k (R = 0.903) is found when the predictive equation incorporates all of the elastic wave parameters obtained non-destructively, and the connected porosity. In general, effective porosity is statistically the most significant variable of the fitted regressions. The σC and k estimation from all the ultrasonic parameters, without considering connected porosity, shows a good correlation (R = 0.852 and 0.864, respectively). The addition of Vs to multiple regressions does not significantly improve the goodness of the fit. Consequently, the measurement of Vs is unnecessary as it is difficult and time-consuming. Finally, results also show that vuggy porosity (present in travertines) influences waveform attenuation and σC and k differently, relative to other microstructural properties; limiting the techniques use for stones with this type of porosity. Estimating σC and k using ultrasonic parameters exclusively is advantageous as the estimations can be obtained non-destructively using portable equipment, while also providing an acceptable goodness of fit. ; This work was supported by the Spanish Ministry of Science and Innovation (MCIN) [grant numbers RTI2018-099052-B-I00, PID2020-116896RB-C21 and PID2020-116896RB-C22] and Regional Government of Madrid (Spain) [Top Heritage, grant number S2018/NMT-4372]; a pre-doctoral research fellowship (FPU20/05157) awarded to N. Garcia-Martinez by the MCIN; and Ph.D. scholarship awarded to M. de Jongh by Historic Environment Scotland (Charity Number: SC045925).

Subsurface environments are non-negligible contributors to the net carbon balance because they act as natural sinks of CO2 and are responsible for the efflux to the Earth's atmosphere during their ventilation states. In this way, the characterization of the CO2 dynamics in these underground environments is essential to determine the gas exchange between both atmospheres. A complete microclimatic analysis and trace gas (CO2 and 222Rn) monitoring of Rull cave (southeast Spain) were conducted to characterize the natural dynamics and anthropogenic influence on the cavity. The analysis was accomplished by implementing wavelet analysis and resemblance techniques. This study enhances wavelet analysis as an efficient tool to analyse microclimatic time series, as it allows for the detection of the main periodicities of signals located in the time domain and the prevailing relationships between them. The analysis indicates that the low-frequency components of the signals were close to the identified annual natural cycles. For a 1-year cycle, the ventilation of the cavity causes the CO2 concentration to decrease from 3569 to 932 ppm in nearly 1 month, highlighting the existence of an output efflux from the cavity. On the contrary, the high-frequency components are linked to human perturbations caused by visitors in the cavity. ; This research was funded by the Spanish Ministry of Economy and Competitiveness Projects CGL2011-25162 and CGL2013-43324-R, and its programme Torres Quevedo (PTQ 13-06296 and PTQ 12-05601). A pre-doctoral research fellowship (BES-2012-053468) was awarded to C. Pla for the Project CGL2011-25162. Funding was also provided by the People Programme (Marie Curie Actions—Intra-European Fellowships, call 2013) of the European Union's Seventh Framework Programme (FP7/2007-2013) under REA Grant Agreement No. 624204.

This study is based on field monitoring of a cave-soil-atmosphere system validated with laboratory experiments. CO and Rn dynamics in the cavity are dependent on climatic parameters, mainly on the differences between the outdoor and indoor temperature. The annual cycles in the cave are characterized by two outstanding phenomena: cave gas recharge and ventilation when the cave acts as a gas sink or source. A permanent relationship with soil above the cave exists. The soil temperature and moisture are responsible for CO production on various time scales. Soil CO at the Rull site reaches values higher than 3000Â ppm in April–May, but falls to nearly 1000Â ppm during the summer. Maximum CO values in the cave are reached in the warmest months and are in accordance with soil CO values. The maximum CO concentration in the cave is 3470Â ppm on average, while the minimum is 623Â ppm. To describe the field findings, CO production and diffusion experiments related to the soil behaviour were developed. The results show that the soil CO production increases as the soil temperature and moisture increase according to a calculated logarithmic equation until the soil water content exceeds the saturation value. The soil-produced CO reaches the Rull cave by diffusion, which in Rull soil is reduced to approximately 60% when the soil water content increased from 0 to 30%. We estimated that 57Â kg of CO was emitted from the cave to the atmosphere in an annual cycle, considering a cave volume of 9915Â m. Finally, projections of the future climate at the study site confirm a general tendency for annual-mean conditions to be warmer and drier, which will directly affect the soil CO production. In this situation, the Rull cave will experience changes in the stored and subsequently exchanged annual amount of CO. ; This research was funded by the Spanish Ministry of Economy and Competitiveness projects CGL2011-25162 and CGL2013-43324-R and its programme Torres Quevedo (PTQ 13-06296 and PTQ 12-05601). A pre-doctoral research fellowship (BES-2012-053468) was awarded to C. Pla for the project CGL2011-25162. ; Funding was also provided by the People Programme (Marie Curie Actions—Intra-European Fellowships, call 2013) of the European Union's Seventh Framework Programme (FP7/2007-2013) under the REA grant agreement n624204 ; Peer Reviewed