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A flood event affecting Pindal Cave, a UNESCO World Heritage site, introduced a substantial amount of external sediments and waste into the cave. This event led to the burial of preexisting sediments, altering the biogeochemical characteristics of the cave ecosystem by introducing heightened levels of organic matter, nitrogen compounds, phosphorus, and heavy metals. The sediments included particulate matter and waste from a cattle farm located within the water catchment area of the cavity, along with diverse microorganisms, reshaping the cave microbial community. This study addresses the ongoing influence of a cattle farm on the cave ecosystem and aims to understand the adaptive responses of the underground microbial community to the sudden influx of waste allochthonous material. Here, we show that the flood event had an immediate and profound effect on the cave microbial community, marked by a significant increase in methanogenic archaea, denitrifying bacteria, and other microorganisms commonly associated with mammalian intestinal tracts. Furthermore, our findings reveal that one year after the flood, microorganisms related to the flood decreased, while the increase in inorganic forms of ammonium and nitrate suggests potential nitrification, aligning with increased abundances of corresponding functional genes involved in nitrogen cycling. The results reveal that the impact of pollution was neither recent nor isolated, and it was decisive in stopping livestock activity near the cave. The influence of the cattle farm has persisted since its establishment over the impluvium area, and this influence endures even a year after the flood. Our study emphasizes the dynamic interplay between natural events, anthropogenic activities, and microbial communities, offering insights into the resilience of cave ecosystems. Understanding microbial adaptation in response to environmental disturbances, as demonstrated in this cave ecosystem, has implications for broader ecological stu

A data-driven approach insensitive to the initial conditions was developed to extract governing equations for the concentration of CO2 in the Altamira cave (Spain) and its two main drivers: the outside temperature and the soil moisture. This model was then reformulated in order to use satellite observations and meteorological predictions, as a forcing. The concentration of CO2 inside the cave was then investigated from 1950 to 2100 under various scenarios. It is found that extreme levels of CO2 were reached during the period 1950–1972 due to the massive affluence of visitors. It is demonstrated that it is possible to monitor the CO2 in the cave in real time using satellite information as an external forcing. For the future, it is shown that the maximum values of CO2 will exceed the levels reached during the 1980s and the 1990s when the CO2 introduced by the touristic visits, although intentionally reduced, still enhanced considerably the micro corrosion of walls and pigments.

Cave heritage is often threatened by tourism or even scientific activities, which can lead to irreversible deterioration. We present a preventive conservation monitoring protocol to protect caves with rock art, focusing on La Garma Cave (Spain), a World Heritage Site with valuable archaeological materials and Palaeolithic paintings. This study assessed the suitability of the cave for tourist use through continuous microclimate and airborne particles monitoring, biofilm analysis, aerobiological monitoring and experimental visits. Our findings indicate several factors that make it inadvisable to adapt the cave for tourist use. Human presence and transit within the cave cause cumulative effects on the temperature of environmentally very stable and fragile sectors and significant resuspension of particles from the cave sediments. These environmental perturbations represent severe impacts as they affect the natural aerodynamic control of airborne particles and determine bacterial dispersal throughout the cave. This monitoring protocol provides part of the evidence to design strategies for sustainable cave management.

The genus Crossiella contains two species, C. equi, causing nocardioform placentitis in horses, and C. cryophila, an environmental bacterium. Apart from C. equi, which is not discussed here, environmental Crossiella is rarely reported in the literature; thus, it has not been included among “rare actinobacteria”, whose isolation frequency is very low. After C. cryophila, only five reports cover the isolation of Crossiella strains. However, the frequency of published papers on environmental Crossiella has increased significantly in recent years due to the extensive use of next-generation sequencing (NGS) and a huge cascade of data that has improved our understanding of how bacteria occur in the environment. In the last five years, Crossiella has been found in different environments (caves, soils, plant rhizospheres, building stones, etc.). The high abundance of Crossiella in cave moonmilk indicates that this genus may have an active role in moonmilk formation, as evidenced by the precipitation of calcite, witherite, and struvite in different culture media. This review provides an overview of environmental Crossiella, particularly in caves, and discusses its role in biomineralization processes and bioactive compound production.

Rull cave is a karstic cave located in Vall d’Ebo (Alicante, Southeast of Spain) developed in massive Miocene conglomerates and Cretaceous limestones. Processes in soil above Rull cave and outdoor atmosphere directly influence the underground environment of the cave. Continuous and discrete monitoring of cave atmosphere and soil (from 2012 to 2022) allows to characterise the spatial distribution and temporal variations of the gaseous concentration (222Rn and CO2) and understand the relationship between the processes which occurred in the 3-component system (soil-cave-atmosphere). Besides the presence of visitors, Rull cave maintains stable values of mean temperature (16.2 °C) and relative humidity (97.6%). In an annual cycle the cave presents two different gaseous stages (stagnation and ventilation). Maximum average values of CO2 and 222Rn concentration are reached within the stagnation stage, in the warmest period of the year. On the contrary, in the ventilation stage (in the coldest months) the cave reaches the lowest concentrations in its inner atmosphere. For the study period, daily average CO2 and 222Rn concentrations are 2008 ppm and 1745 Bq/m3, respectively. Results show that the dynamics of 222Rn and CO2 in the cave air follow different patterns defined by the complex relationships between external and internal factors. Findings from this study provide substantial information about the environmental situation of the cave atmosphere in terms of air quality for visitors and workers.

Los ambientes kársticos son los ecosistemas subterráneos más representativos a escala global ya que ocupan aproximadamente el 20 % de la superficie terrestre, albergan cavidades próximas a la superficie y forman parte de lo que se conoce como Zona Crítica de la Tierra. A pesar de que podrían jugar un papel importante en la regulación de la composición de la atmósfera externa, los ecosistemas subterráneos aún no han sido incluidos en las estimaciones globales de los balances de los principales GEI, pero son cada vez más numerosos los trabajos de investigación en este campo..., Karstic environments are the most representative underground ecosystems on a global scale since they cover approximately 20% of the land surface of the Earth and contain shallow caves that belong to the Critical Zone of the Earth. Although they could play an important role in regulation of the external atmosphere composition, the underground ecosystems have not yet been included in the annual carbon balances of the main GHGs. However, the research interest in this field has recently increased...

In the absence of sunlight, caves harbor a great diversity of microbial colonies to extensive biofilms with different sizes and colors visible to the naked eye. One of the most widespread and visible types of biofilm are those with yellow hues that can constitute a serious problem for the conservation of cultural heritage in many caves, such as Pindal Cave (Asturias, Spain). This cave, declared a World Heritage Site by UNESCO for its Paleolithic parietal art, shows a high degree of development of yellow biofilms that represents a real threat to the conservation of painted and engraved figures. This study aims to: 1) identify the microbial structures and the most characteristic taxa composing the yellow biofilms, 2) seek the linked microbiome reservoir primarily contributing to their growth; 3) seed light on the driving vectors that contribute to their formation and determine the subsequent proliferation and spatial distribution. To achieve this goal, we used amplicon-based massive sequencing, in combination with other techniques such as microscopy, in situ hybridization and environmental monitoring, to compare the microbial communities of yellow biofilms with those of drip waters, cave sediments and exterior soil. The results revealed microbial structures related to the phylum Actinomycetota and the most characteristic bacteria in yellow biofilms, represented by the genera wb1-P19, Crossiella, Nitrospira, and Arenimonas. Our findings suggest that sediments serve as potential reservoirs and colonization sites for these bacteria that can develop into biofilms under favorable environmental and substrate conditions, with a particular affinity for speleothems and rugged-surfaced rocks found in condensation-prone areas. This study presents an exhaustive study of microbial communities of yellow biofilms in a cave, which could be used as a procedure for the identification of similar biofilms in other caves and to design effective conservation strategies in caves with valuab

Castañar Cave (Caceres, Spain) is a unique show cave known for its high natural radiation levels. This study presents a comprehensive analysis of its prokaryotic diversity, specifically focusing on investigating the influence of environmental conditions and substrate characteristics on the prokaryotic community structure in the cave sediments. Additionally, the research aims to evaluate the potential impact of human activities on the cave ecosystem. The identification of distinct bioclimatic zones within the cave was made possible through a combination of environmental and microbial monitoring (ATP assays). The results reveal sediment texture as a significant factor, notably affecting the structure, diversity, and phylogenetic variability of the microbial community, including both Bacteria and Archaea. The proportion of clay minerals in sediments plays a crucial role in regulating moisture levels and nutrient availability. These substrate properties collectively exert a significant selective pressure on the structure of prokaryotic communities within cave sediments. The molecular approach shows that heterotrophic bacteria, including those with chitinolytic enzymes, primarily inhabit the cave. Furthermore, chemoautotrophic nitrifiers such as the archaea Nitrososphaeria and the genus Nitrospira, as well as methanotrophic bacteria from the phyla Methylomirabilota, Pseudomonadota, and Verrucomicrobiota, are also present. Remarkably, despite being a show cave, the cave microbiota displays minimal impacts from human activities and the surface ecosystem. Prokaryotic populations exhibit stability in the innermost areas, while the tourist trail area experiences slightly higher biomass increases due to visitor traffic. This suggests that conservation efforts have successfully limited the entry of external nutrients into the innermost cave areas. Additionally, the results suggest that integrating biomarkers like ATP into environmental monitoring can significantly enhance the m

En el singular yacimiento de El Sidrón se han producido una impactante serie de acontecimientos relacionados con las actividades y comportamientos de la especie neandertal, integradas en unos procesos del medio físico peculiares, sazonadas con la proximidad de la mejor materia prima silícea asturiana, y con un peculiar encadenamiento de situaciones expeditivas y rápidas. Todo ello integrado en una investigación interdisciplinar., At the unique site of El Sidrón there have been an impressive series of events related to the activities and behaviors of the Neandertal species, integrated into peculiar environmental processes, seasoned with the proximity of the best Asturian siliceous raw material, and with a peculiar chain of expeditious and fast situations. All this integrated into an interdisciplinary investigation.

Understanding the dynamics and spatial distribution of gases in the subterranean atmospheres is essential to increase the reliability of carbon balances in karst ecosystems or the paleoclimate reconstructions based on cave deposits. This scientific information is also very valuable for cave managers to ensure the safety of visitors and the conservation of the subterranean heritage. Through a comprehensive monitoring of the main air parameters in a shallow temperate cave, we decipher the physical drivers and mechanisms involved in the CO2 and radon exchange between the cave and the outer atmosphere, and how this process is triggered by the changes of local weather. Our results reveal that the biphasic infiltration (water plus air) in the network of penetrative structures from the overlying soil and host rock exercise remarkable control over the cave environment, delaying the thermal response of the cave air to the outer climate-driven changes and also the gaseous transfer between the cave atmosphere and the exterior. The cave location concerning the karstified outcrop determines that this subterranean site acts as a gas emitter during summer, which is contrary to what happens in many other caves. Prominent gas entrapment at a micro-local level is also registered in some upper galleries.

At the unique site of El Sidrón there have been an impressive series of events related to the activities and behaviors of the Neandertal species, integrated into peculiar environmental processes, seasoned with the proximity of the best Asturian siliceous raw material, and with a peculiar chain of expeditious and fast situations. All this integrated into an interdisciplinary investigation, En el singular yacimiento de El Sidrón se han producido una impactante serie de acontecimientos relacionados con las actividades y comportamientos de la especie neandertal, integradas en unos procesos del medio físico peculiares, sazonadas con la proximidad de la mejor materia prima silícea asturiana, y con un peculiar encadenamiento de situaciones expeditivas y rápidas. Todo ello integrado en una investigación interdisciplinar

En esta investigación hemos estudiado, por primera vez, microclimas kársticos como sistemas dinámicos no lineales. En particular, hemos analizado y modelizado los microclimas de las cuevas españolas de Altamira y El Rull y sus conexiones con el clima exterior. Con este objetivo, hemos utilizado la técnica de modelización global, la cual pretende extraer modelos directamente de datos observacionales. Esta técnica está bien adaptada al estudio de sistemas complejos reales y se apoya en los teoremas de embedding. El embedding permite, en principio, reconstruir sistemas usando las variables disponibles y algunas de sus derivadas; por tanto, abre la posibilidad de modelizar microclimas kársticos incluso si algunas variables de estado no están disponibles o no pueden medirse en la práctica. También ha demostrado ser aplicable a series temporales muy cortas, lo cual constituye también una ventaja en comparación con otros tipos de modelización. Los microclimas de cuevas están dirigidos por el clima exterior. La variedad de climas externos y de configuraciones de las cavidades lleva a una variedad de microclimas kársticos. No obstante, uno de los controles más relevantes es normalmente la diferencia de temperatura entre el interior y el exterior. En general, los microclimas kársticos son muy estables en relación a variables como la temperatura o la humedad (comparadas con las exteriores). Por el contrario, los niveles de CO2 y 222Rn en el aire muestran notables oscilaciones estacionales a lo largo del año, por lo que estos gases son adecuados para caracterizar las dinámicas de las atmósferas de cuevas. Los microclimas de cuevas se suelen entender como la superposición de componentes deterministas y estocásticas. La hipótesis de una componente determinista frecuentemente se considera ineludible porque es una hipótesis habitual en la física clásica y porque las aproximaciones que permiten detectar determinismo a partir de datos observacionales son escasas. El haber encontrado

El Sidrón Cave is an archaeological and anthropological reference site of the Neanderthal world. It shows singular activity related to cannibalisation, and all existing processes are relevant to explain the specific behaviour of the concerned individuals. This paper presents geoarchaeological data, primarily based on mineralogical and petrographic techniques, from an investigation of the nature of the encrustations or hard coatings that affect a large part of the Neanderthal bone remains and their relationship with the depositional and post-depositional processes at the archaeological site. Crusts and patina were found to be numerous and diverse, mainly composed of calcite and siliciclastic grains, with different proportions and textures. The analysis indicated different origins and scenarios from their initial post-mortem accumulation to the final deposit recovered during the archaeological work. The presence of micromorphological features, such as clotted-peloidal micrite, needle-fibre calcite (NFC) aggregates, clay coatings, iron–manganese impregnation, and/or adhered aeolian dust may indicate that a significant proportion of the remains were affected by subaerial conditions in a relatively short period of time in a shelter, cave entrance, or shallower level of the karstic system, prior to their accumulation in the Ossuary Gallery.

The purpose of this paper is to model numerically the dynamics of CO2 and 222Rn in cave atmospheres, particularly in the noteworthy Cave of Altamira (Spain). We aim to get a better understanding of the nature of these dynamics and their couplings with climatic controls, more specifically the soil water content, which role in the said dynamics poses some questions. For the first time, we apply the global modeling technique in the field of cave microclimate and atmospheric composition. The global modeling technique is a methodology based on the theory of nonlinear systems and designed to extract mathematical models directly from observational time series. We were able to extract four global models from our data. These models represent a step forward from the existent conceptual ones. They also show that CO2 and 222Rn dynamics can be approximated by low-dimensional, deterministic systems, which can be chaotic or, at least, close to chaos; this has decisive methodological consequences for future research. Moreover, the global modeling technique was used for the first time in a non-autonomous formulation; this enabled the possibility of studying the influence of the external forcing (soil water content) on the gas concentration in different scenarios.

Of the several critical challenges present in environmental microbiology today, one is the assessment of the contribution of microorganisms in the carbon cycle in the Earth-climate system. Karstic subterranean ecosystems have been overlooked until recently. Covering up to 25% of the land surface and acting as a rapid CH4 sink and alternately as a CO2 source or sink, karstic subterranean ecosystems play a decisive role in the carbon cycle in terms of their contribution to the global balance of greenhouse gases. Recent data indicate that microbiota must play a significant ecological role in the biogeochemical processes that control the composition of the subterranean atmosphere, as well as in the availability of nutrients for the ecosystem. Nevertheless, there are still essential gaps in our knowledge concerning the budgets of greenhouse gases at the ecosystem scale and the possible feedback mechanisms between environmental-microclimatic conditions and the rates and type of activity of microbial communities in subterranean ecosystems. Another challenge is searching for bioactive compounds (antibiotics) used for treating human diseases. At present, there is a global health emergency and a strong need for novel biomolecules. In recent decades, great research efforts have been made to extract antibiotics from marine organisms. More recently, caves have been receiving considerable attention in search of novel antibiotics. Cave methanotrophic and heterotrophic bacteria are producers of bioactive compounds and may be potential sources of metabolites with antibacterial, antifungal or anticancer activities of interest in pharmacological and medical research, as well as enzymes with a further biotechnological use. Here we also show that bacteria isolated from mines, a still unexplored niche for scientists in search of novel compounds, can be a source of novel secondary metabolites.

Understanding the fluctuations in cave air concentrations and their climatic control is substantial not only to preserve the quality of indoor atmospheres but also to avoid the risk related to the presence of hazardous substances. In this study, we investigated the most influential factors affecting 222Rn and CO2 concentrations, the nature of their dynamics, and their coupling with climatic variations. For this purpose, we combined a set of mathematical methods that included a statistical and wavelet analysis of a 6-year time series in Rull Cave (Spain). Generally, the 222Rn and CO2 dynamic in cave air showed similar patterns. However, the obtained results show that these gases have a different frequency response. Thus, the annual component of 222Rn and CO2 is controlled by the relationship between external and internal temperatures. At low frequencies, both gases are affected by the same variables when the cave atmosphere reaches a minimum concentration. However, when the cave atmosphere is isolated from the outdoors, 222Rn and CO2 behave differently and disturbance caused by the visitors is evidenced in terms of the CO2 concentration; the latter observation was confirmed by the wavelet analysis at high frequencies. In contrast, the 222Rn concentration shows important variations following rainfall, which was weakly identified in the CO2 concentration.

The Necropolis of Carmona, which has more than 600 tombs carved in calcarenites, is among the most important Roman burial sites preserved in southern Spain. The tombs in the Necropolis show severe alteration and multiple weathering processes after being excavated at the end of the nineteenth century without a preventive conservation plan. The archaeological site shows strong anthropic modifications related to different excavation stages and in relation to the construction of facilities for the visiting public. In particular, the exposure of the buried tombs to meteoric conditions and anthropic modification of natural drainage have led to an important acceleration of the deterioration of the tombs. The conservation status of the Necropolis was defined through a comprehensive geo‐environmental study that combined field observations and laboratory data, modelling and digital mapping and environmental monitoring. Results allow a methodology to be developed providing guidelines to minimize potential risks when excavating new tombs (now buried) in the future. Moreover, the most suitable prospective areas can be defined inside the Necropolis in terms of the environmental, geological and geomorphological conditions which will enhance the preservation of newly exhumed tombs. Geo‐environmental preventive conservation methods that we propose can be entirely applied to other large archaeological sites completely exposed to open‐air atmospheric conditions.

KarsTS 2.2 is free, open-source, R-based software for microclimate time series, especially suited to the study of underground or highly insulated environments. The time series of interest include air temperature, humidity, and CO2 and 222Rn content, amongst others. These time series usually pose problems such as gaps, outliers, noise or relative shortness. KarsTS was born as a package for gap filling and thus, it offers multiple univariate and multivariate gap-filling tools well suited to these variables. However, as KarsTS was intended to be a self-sufficient program, it soon grew to encompass several tools for linear and nonlinear time series analysis, preprocessing and plotting. Indeed, many of these variables show a nonlinear behavior that is often disregarded; for this reason, we aim to spread and facilitate the use of some methodologically appropriate analysis tools, even amongst researcher that do not feel comfortable using a console. In this paper, we introduce an overview of KarsTS functionality and we show its potential through some practical application examples on four-year time series of temperature from the Rull cave (Spain).

The Roman Necropolis of Carmona (Sevilla, Spain) has experienced a severe deterioration since the accidental discovery in 1868 and subsequent archaeological excavations starting in 1882. To this deterioration contributed the location in a soft calcarenite rock quarry, the adverse environmental conditions and the numerous and extensive wrong archaeological and managing interventions along more than a century. The cultural, artistic and religious importance of this Necropolis converts the protection and conservation of this archaeological site in a major issue. This work present the data obtained in a multidisciplinary research were geology, geomorphology, micro-environmental and climatic monitoring, rock petrophysical characterization, description of weathering forms and biological colonization were considered in order to propose corrective measures to minimize deterioration.

El relleno sedimentario que alberga el registro arqueológico y antropológico de la Galería del Osario (cueva de El Sidrón) presenta una alta complejidad, tanto en los tipos de sedimentos como en su distribución espacial en la cavidad. Los principales factores que rigen esta complejidad son la naturaleza episódica y altamente energética de gran parte de las unidades litoestratigráficas reconocidas y la irregular geometría del propio conducto, que compartimenta significativamente las áreas de deposición. A modo de resumen puede indicarse que en la Galería del Osario quedan representados todos los tipos de materiales detríticos típicos de depósitos alóctonos en ambiente kárstico; desde materiales bien seleccionados de granulometría fina representativos de facies de encharcamiento (arcillas de la unidad O) o de desbordamiento (Unidad IV), a depósitos groseros mal seleccionados correspondientes a coladas de barro y detritos en masa (Unidad II y base de unidad III), pasando por típicas facies fluvio-kársticas o de canal compuestas por materiales arenosos con laminaciones y estructuras de flujo (unidades I y II). Los restos óseos se concentran en la unidad III. El área fuente se sitúa en cotas superiores a la Galería del Osario, es decir, en los niveles intermedio o superior del sistema kárstico, y el depósito o entrada de material óseo a la Galería del Osario se activaría en episodios de alta energía relacionado con eventos de inundación y/o tormenta., The sedimentary infill bearing the archaeological and anthropological record of the Ossuary Gallery (the Sidrón cave) shows high complexity in both sediment types and their spatial distribution in the cavity. The main factors that govern this complexity are the episodic and highly energetic nature of the recorded sedimentary infill units and the irregular geometry of the gallery itself, which significantly compartmentalized areas of deposition. Briefly, all types of typical allochthonous detrital material deposits in karst environments are represented in the Ossuary Gallery; from well-sorted fine-grained sediment facies representative of backswamp (clays of the unit O) or slackwater (Unit IV), to poorly-sorted coarse-grained deposits corresponding to mudflows and debris flows (Unit II and Unit III base), and typical channel facies composed of laminated sands and silts (units I and II). The bone and lithic remains are concentrated in unit III. The source area is above the Ossuary Gallery, at the intermediate or higher karst levels. The input of archeological material to the Ossuary Gallery was triggered in high energy episodes in association to flood events and / or storms.

The soils above caves represent a membrane that regulates the connection between the underground environment and the outside atmosphere. In this study, soils from two different field sites (Cueva de Altamira and Cueva del Rull in Spain) are investigated. Field results are analysed and linked to laboratory tests. Several laboratory experiments are performed to quantify CO2 diffusion coefficients and water infiltration rates in these soils under different degrees of soil water saturation and compaction. Tests confirm that the grain size distribution, organic matter content, mineral composition and water content of soils affect gas transport through the soil pore network. Both field and lab results reveal that Altamira soil has a coarser texture and therefore has higher CO2 diffusion coefficients, infiltration rates and hydraulic conductivity values than Rull soil. Rull soil contains a higher proportion of fine particles and organic matter, which explains the lower fluid transport coefficients. When soils are near saturation, fluid transport does not depend on the physical properties of soil but depends on the soil water content. In this state, liquid transport regulates the available space within the soil pores, which leads to a reduction in the gaseous diffusion coefficient of the soil. After rainfall episodes, the connection between the exterior atmosphere and underground cavities is hindered due to a rise in the soil water content, which is responsible for the closure of the overlying membrane. This study demonstrates that soil-produced CO2 reaches the underground atmosphere through diffusion processes that are controlled by the intrinsic properties of soil (porosity, grain size distribution, texture, mineralogy and organic matter content) and soil water content.

A geological and geomorphological analysis has been performed in the necropolis of Dra Abu el-Naga in order to understand the role played by these two factors in the development of the sacred landscape. The investigation focuses upon two aspects of the development of the necropolis, the selection criteria for tomb location and the reconstruction of the ancient funerary landscape. Around 50 tombs were surveyed, analysing the characteristics of their host rock and classifying them according to a modified Rock Mass Rating Index, in order to understand how rock quality affected tomb construction. This analysis resulted in the definition of five rock-quality classes (I to V) from very good to very poor rock. The geological study also resulted in a proposed geological-geomorphological model for the evolution of this zone of the Theban necropolis that complements previous works by other authors. Due to the lack of precise dating evidence this chronology is a relative one and is based on the chronology given by other authors for similar deposits and events. Two catastrophic events, represented by mega-landslides, have been identified, the first one predates the deposition of early Pleistocene fluvial deposits, and the second one possibly occurred during the middle-late Pleistocene. Two weathering surfaces developed under wetter than present climatic conditions and have been tentatively correlated to the mid-late Pleistocene humid period and the African-Humid Period (early-mid Holocene).

Los ambientes subterráneos, ampliamente distribuidos en los distintos ecosistemas terrestres, contienen un volumen significante de aire subterráneo con altas concentraciones de CO2 producido en el suelo. Concretamente, los sistemas kársticos constituyen emisores o almacenes temporales naturales de CO2 que, durante su estado de ventilación, emiten CO2 a la atmósfera. La caracterización de la dinámica gaseosa de estos ambientes subterráneos es, por tanto, fundamental para conocer y determinar el intercambio gaseoso que se produce entre los mismos y la atmósfera exterior. El estudio se centra, fundamentalmente, en la Cueva del Rull aunque, de forma paralela, también se han estudiado ciertos aspectos de la Cueva de Altamira para poder comparar los resultados de ambos espacios subterráneos y poder relacionarlos entre sí. Se ha desarrollado un estudio de los parámetros microclimáticos y gases traza (CO2 y 222Rn) con el objetivo de estudiar la evolución natural de su dinámica gaseosa y la influencia que las visitas ejercen en ella, puesto que se trata de una cueva visitable. El análisis de los datos registrados se realiza implementando el análisis de wavelets. Otro punto de la investigación se aborda mediante el estudio del suelo que existe sobre una cueva. El suelo forma parte de la membrana que separa la atmósfera subterránea de la exterior, y es responsable de regular la conexión existente entre ambas. Por esta razón, dos suelos diferentes, ubicados sobre dos cuevas distintas (Cueva del Rull y Cueva de Altamira) han sido estudiados, tanto en campo como mediante ensayos de laboratorio. El estudio de la dinámica gaseosa de la Cueva del Rull (CO2 y 222Rn) ha demostrado su dependencia de los parámetros climáticos, fundamentalmente de la diferencia de temperaturas entre el interior y el exterior. La conexión entre la atmósfera subterránea y la exterior queda controlada por el estado del suelo ubicado sobre las cuevas. La temperatura y humedad del suelo son responsables de la

This study is based on field monitoring of a cave-soil-atmosphere system validated with laboratory experiments. CO2 and 222Rn 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 CO2 production on various time scales. Soil CO2 at the Rull site reaches values higher than 3000 ppm in April–May, but falls to nearly 1000 ppm during the summer. Maximum CO2 values in the cave are reached in the warmest months and are in accordance with soil CO2 values. The maximum CO2 concentration in the cave is 3470 ppm on average, while the minimum is 623 ppm. To describe the field findings, CO2 production and diffusion experiments related to the soil behaviour were developed. The results show that the soil CO2 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 CO2 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 57 kg of CO2 was emitted from the cave to the atmosphere in an annual cycle, considering a cave volume of 9915 m3. 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 CO2 production. In this situation, the Rull cave will experience changes in the stored and subsequently exchanged annual amount of CO2.

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.

The rock-cut tomb–chapel of Djehuty (Luxor, Egypt, 1470 bc) was excavated and restored including a mineralogical, chemical, textural and petrophysical study of mortars and host rocks together with micro-environmental parameter recordings to deduce the techniques used by the ancient Egyptian builders. The host rock is made by alternations of massive, nodular and finely bedded micritic limestone and the tomb was excavated in the stratigraphic section with better mechanical properties. Different types of gypsum and lime mortars were found in the funerary complex: mortar for bedding, exterior render, surface repair and decoration, and interior plaster and coating. Mortars show formulae according to their specific applications and locations. The sources of the raw materials for the mortar reveal a local provenance. Micro-environmental conditions play an important role in the evolution of the mortar pastes, and determine the current characteristics and stability of mortars. Results from this research will make it possible to design mortars compatible with conservation in the funerary complex of Djehuty and to define safe micro-environmental conditions for the preservation of such mortars and paintings.

La gran diversidad intrínseca del karst y la variedad de campos científicos desde los que ha sido estudiado este medio ha generado un espectacular aumento de su conocimiento. Ese avance ha venido acompañado también de nuevas incógnitas y nuevos planteamientos. El presente trabajo trata de recoger una pequeña muestra de esa amplia diversidad, asociada a un elevado grado de especialización, que de forma integrada permite completar el puzzle del karst. Inicialmente, se presenta una revisión sintética del concepto de karst, del proceso de karstificación y de las morfologías asociadas al mismo. Seguidamente, y planteado a partir de una serie de interrogantes, se muestran algunos aspectos y curiosidades relacionadas con el karst. Las características microclimáticas subterráneas, el karst no tradicional o los depósitos y mineralizaciones asociados al karst, son algunos de los temas que se incluyen en este trabajo y que puede interesar a los docentes que imparten docencia sobre el karst., The great intrinsic diversity of karst and the variety of scientific fields in which it has been studied has generated a dramatic increase in our knowledge about it. This advance has also been accompanied by new questions and issues that open the door to new approaches. Our work intends to show a small sample of the wide diversity, often associated with a high degree of specialization, which allows completing the karst puzzle. In the first place, this paper provides a synthetic review of the concept of karst, the karstification process and the morphologies associated with it. Next, starting with a few questions, it shows some aspects and curiosities related to karst. The features of the underground microclimate, the non-traditional karst or deposits and mineralization associated with karst, are some of the topics included in this work, which can be interesting for the teachers dealing with the topic of karst in their classes.

In recent years, methane (CH4) has received increasing scientific attention because it is the most abundant non-CO2 atmospheric greenhouse gas (GHG) and controls numerous chemical reactions in the troposphere and stratosphere. However, there is much that is unknown about CH4 sources and sinks and their evolution over time. Here we show that near-surface cavities in the uppermost vadose zone are now actively removing atmospheric CH4. Through seasonal geochemical tracing of air in the atmosphere, soil and underground at diverse geographic and climatic locations in Spain, our results show that complete consumption of CH4 is favoured in the subsurface atmosphere under near vapour-saturation conditions and without significant intervention of methanotrophic bacteria. Overall, our results indicate that subterranean atmospheres may be acting as sinks for atmospheric CH4 on a daily scale. However, this terrestrial sink has not yet been considered in CH4 budget balances.

The Circular Mausoleum tomb in the Roman Necropolis of Carmona was carved on a calcarenite sequence in an ancient quarry located in the town of Carmona, Southern Spain. This rock-cut tomb, representative of Roman burial practices, currently suffers from serious deterioration. A detailed survey over several years permitted the identification of the main tomb's pathologies and damaging processes, which include loss of material (scaling, flaking, granular disintegration), surface modifications (efflorescences, crusts and deposits) and extensive biological colonization. The results obtained in this study indicated that anthropogenic changes were largely responsible and enhanced the main alteration mechanisms observed in the Circular Mausoleum. Based on the deterioration diagnosis, effective corrective actions were proposed. This study shows that any conservative intervention in the interior of the tomb should be preceded by accurate in situ measurements and laboratory analyses to ascribe the source of the deterioration damages and thus designing effective treatments.

San Roque church (Campeche, Mexico) was built at the end of the 17th century with a micritic limestone and lime mortar in baroque style. In 2005 the church exhibited heavy biodeterioration associated with the development of extensive dark green phototrophic-based biofilms. Several cyanobacteria belonging to the order Chroococcales and lichenized fungi (Toninia nordlandica, Lobaria quercizans, Lecanora subcarnea, Cystocoleus ebeneus) were predominant in the dark biofilm samples, as revealed by DNA-based molecular techniques. In 2009, a cleaning and restoration intervention was adopted; however, after few months, microbial recolonization started to be noticeable on the painted church walls, representing an early phototrophic-based recolonization. According to molecular analysis, scanning electron microscopy observations and digital image analysis of cross sections, new phototrophic-based colonization, composed of cyanobacteria and bryophytes, developed mainly beneath the restored mortars. The intrinsic properties of the mortars, the tropical climate of Campeche and the absence of a biocide treatment in the restoration protocol influenced the recolonization of the church façades and enhanced the overall rate of deterioration in a short-term period.

The Etruscan civilisation originated in the Villanovan Iron Age in the ninth century BC and was absorbed by Rome in the first century BC. Etruscan tombs, many of which are subterranean, are one of the best representations of this culture. The principal importance of these tombs, however, lies in the wall paintings and in the tradition of rich burial, which was unique in the Mediterranean Basin, with the exception of Egypt. Relatively little information is available concerning the biodeterioration of Etruscan tombs, which is caused by a colonisation that covers the paintings with white, circular to irregular aggregates of bacteria or biofilms that tend to connect each other. Thus, these colonisations sometimes cover extensive surfaces. Here we show that the colonisation of paintings in Tomba del Colle is primarily due to bacteria of the order Rhizobiales (Alphaproteobacteria), which were likely influenced by the neighbouring rhizosphere community and the availability of nutrients from root exudates.

A MATLAB-based computer code has been developed for the simultaneous wavelet analysis and filtering of several environmental time series, particularly focused on the analyses of cave monitoring data. The continuous wavelet transform, the discrete wavelet transform and the discrete wavelet packet transform have been implemented to provide a fast and precise time–period examination of the time series at different period bands. Moreover, statistic methods to examine the relation between two signals have been included. Finally, the entropy of curves and splines based methods have also been developed for segmenting and modeling the analyzed time series. All these methods together provide a user-friendly and fast program for the environmental signal analysis, with useful, practical and understandable results.

CO2 exchange between terrestrial ecosystems and the atmosphere is key to understanding the feedbacks between climate change and the land surface. In regions with carbonaceous parent material, CO2 exchange patterns occur that cannot be explained by biological processes, such as disproportionate outgassing during the daytime or nighttime CO2 uptake during periods when all vegetation is senescent. Neither of these phenomena can be attributed to carbonate weathering reactions, since their CO2 exchange rates are too small. Soil ventilation induced by high atmospheric turbulence is found to explain atypical CO2 exchange between carbonaceous systems and the atmosphere. However, by strongly altering subsurface CO2 concentrations, ventilation can be expected to influence carbonate weathering rates. By imposing ventilation-driven CO2 outgassing in a carbonate weathering model, we show here that carbonate geochemistry is accelerated and does play a surprisingly large role in the observed CO2 exchange pattern of a semi-arid ecosystem. We found that by rapidly depleting soil CO2 during the daytime, ventilation disturbs soil carbonate equilibria and therefore strongly magnifies daytime carbonate precipitation and associated CO2 production. At night, ventilation ceases and the depleted CO2 concentrations increase steadily. Dissolution of carbonate is now enhanced, which consumes CO2 and largely compensates for the enhanced daytime carbonate precipitation. This is why only a relatively small effect on global carbonate weathering rates is to be expected. On the short term, however, ventilation has a drastic effect on synoptic carbonate weathering rates, resulting in a pronounced diel pattern that exacerbates the non-biological behavior of soil–atmosphere CO2 exchanges in dry regions with carbonate soils.

The paintings from Tomba della Scimmia, in Tuscany, are representative of the heavy bacterial colonization experienced in most Etruscan necropolises. The tomb remained open until the late 70′s when it was closed because of severe deterioration of the walls, ceiling and paintings after decades of visits. The deterioration is the result of environmental changes and impacts suffered since its discovery in 1846. We show scanning electron microscopy and molecular studies that reveal the extent and nature of the biodeterioration. Actinobacteria, mainly Nocardia and Pseudonocardia colonize and grow on the tomb walls and this process is linked to the availability of organic matter, phyllosilicates (e.g. clay minerals) and iron oxides. Nocardia is found metabolically active in the paintings. The data confirm the specialization of the genera Nocardia and Pseudonocardia in the colonization of subterranean niches.

Fluctuations of trace gas activity as a response to variations in weather and microclimate conditions were monitored over a year in a shallow volcanic cave (Painted Cave, Galdar, Canary Islands, Spain). 222Rn concentration was used due to its greater sensitivity to hygrothermal variations than CO2 concentration. Radon concentration in the cave increases as effective vapour condensation within the porous system of the rock surfaces inside the cave increases due to humidity levels of more than 70%. Condensed water content in pores was assessed and linked to a reduction in the direct passage of trace gases. Fluctuations in radon activity as a response to variations in weather and microclimate conditions were statistically identified by clustering entropy changes on the radon signal and parameterised to predict radon concentration anomalies. This raises important implications for other research fields, including the surveillance of shallow volcanic and seismic activity, preventive conservation of cultural heritage in indoor spaces, indoor air quality control and studies to improve understanding of the role of subterranean terrestrial ecosystems as reservoirs and/or temporary sources of trace gases.

Different types of land use are usually present in the areas adjacent to many shallow karst cavities. Over time, the increasing amount of potentially harmful matter and energy, of mainly anthropic origin or influence, that reaches the interior of a shallow karst cavity can modify the hypogeal ecosystem and increase the risk of damage to the Palaeolithic rock art often preserved within the cavity. This study proposes a new Protected Area status based on the geological processes that control these matter and energy fluxes into the Altamira cave karst system. Analysis of the geological characteristics of the shallow karst system shows that direct and lateral infiltration, internal water circulation, ventilation, gas exchange and transmission of vibrations are the processes that control these matter and energy fluxes into the cave. This study applies a comprehensive methodological approach based on Geographic Information Systems (GIS) to establish the area of influence of each transfer process. The stratigraphic and structural characteristics of the interior of the cave were determined using 3D Laser Scanning topography combined with classical field work, data gathering, cartography and a porosity–permeability analysis of host rock samples. As a result, it was possible to determine the hydrogeological behavior of the cave. In addition, by mapping and modeling the surface parameters it was possible to identify the main features restricting hydrological behavior and hence direct and lateral infiltration into the cave. These surface parameters included the shape of the drainage network and a geomorphological and structural characterization via digital terrain models. Geological and geomorphological maps and models integrated into the GIS environment defined the areas involved in gas exchange and ventilation processes. Likewise, areas that could potentially transmit vibrations directly into the cave were identified. This study shows that it is possible to define a Protected