Underground Atmosphere Research Articles

The World’s Largest Bauxite-Bearing Province, Fouta Djallon–Mandingo (West Africa). Part 4: a Zoning Mechanism in Laterite Bauxite-Bearing Weathering Crust

The results of detailed exploration and year-round observations of the hydrogeological regime at large deposits, as well as special hydrochemical studies of various types of water and changes in the gas composition of the underground atmosphere in the lateritic weathering crust, of the very large bauxite-bearing province, Fouta Djallon–Mandingo, thanks to a reliable factual base, made it possible for the first time to draw a number of important conclusions about the conditions and features of zoning formation in the lateritic weathering profile. The weathering profile consists of two metasomatic columns spatially combined in plan, but vertically separated: an upper one, consisting of hydroxides and oxides of iron and aluminum, and a lower one, composed of clayey eluvium and products of hydration and decomposition of aluminosilicates—polymineral clays and kaolinite. In both columns, the processes of change begin with the same rainwater, but differ in the hydrodynamic parameters in each of the columns. Changes in the weathering profile occur in accordance with the main patterns of low-temperature infiltration metasomatism. The modern hydrogeological and gas regime in bauxite-bearing lateritic covers controls the mineralogical and geochemical zoning. Features of biological and soil processes and hydrodynamics and hydrochemistry in the weathering profile lead to a threshold nature of the change in physicochemical and biochemical conditions, providing the action of geochemical (oxidation, reduction, gley, adsorption) barriers, which is the main mechanism of zonal distribution of matter in lateritic weathering crusts.

THE WORLD’S LARGEST FOUTA DJALLON–MANDINGO BAUXITE PROVINCE (WEST AFRICA): PART 4. THE MECHANISM OF ZONING FORMATION IN LATERITE BOXITE-BEARING WEATHERING CRUSTS

Obtained as a result of detailed exploration and year-round observations of the hydrogeological regime at large deposits, as well as special hydrochemical studies of various types of water and changes in the gas composition of the underground atmosphere in the lateritic weathering crust of the largest bauxite-bearing province FDM, thanks to a reliable factual base, allowed us to draw a number of important conclusions on the conditions and features of the formation of zoning in the lateritic weathering profile for the first time. The weathering profile consists of two metasomatic columns spatially combined in plan, but vertically separated: the upper, lateritic cover, composed mainly of the products of the final hydrolysis of lateritic weathering, that is, hydroxides and oxides of iron and aluminum; the lower one, composed of clayey eluvium, products of hydration and decomposition of aluminosilicates - polymineral clays and kaolinite. In both columns, the processes of changing begin with the same rainwater, but differ in hydrodynamic parameters in each of the columns. Changes in the weathering profile occur in accordance with the main patterns of low-temperature infiltration metasomatism. The modern hydrogeological and gas regime in the bauxite-bearing lateritic covers controls the mineralogical and geochemical zoning. Peculiarities of biological and soil processes, hydrodynamics and hydrochemistry in the weathering profile lead to the threshold nature of the change in physicochemical and biochemical conditions, providing the action of geochemical (oxidative, reducing, gley, adsorption) barriers - the main mechanism of zonal distribution of matter in lateritic crusts.

Применение изотопов радона для изучения вариаций напряженного состояния горных пород при прогнозе землетрясений

The results of interpretation of monitoring observations of radon-220 (thoron) and radon-222 monitoring observations, carried out in 2002-2004 on the Northern Tien-Shan, are presented. Prognostic capabilities of thoron as a short-term earthquakes precursor are shown. It is noted that the anomalies of thoron are more contrast in comparison with anomalies of radon-222. Insufficient contrast of radon-222 anomalies is explained by methodological in observations by seismic radon stations. The behavior of thoron during the earthquake preparation agrees with the previously established spatial-temporal patterns for radon-222 (Kozlova et al., 2021 Radon isotopes are most suitable for monitoring observations of the earthquake preparation process using gases that are part of the underground atmosphere. The prospect of using other gases is limited by the absence of their continuous generation, by the presence of a cumulative effect, and by the difficulty of registration. The above also applies to the use for prognostic purposes of variations in the content of chemical compounds dissolved in groundwater.

Classification of the Ocnele Mari saline from the point of view of gas emissions (CH4 and CO2)

Currently in Romania there are six salt mines which exploit the salt through underground mine workings: Dej salt mine, Tg. Ocna salt mine, Slanic Prahova salt mine, Ocnele Mari salt mine, Cacica salt mine, and Praid salt mine. The purpose of the present paper work is to establish the methane release (explosive gas) and the carbon dioxide release regime in mine workings from Praid salt mine in order to classification. This verification of the Ocnele Mari salt mine classification has been carried out during September 2021 and there have been taken into account the following elements: - Geological and technical-mining conditions of the salt deposit related to Dej mining perimeter; - Results of the quantitative and qualitative measurements from the underground mine workings regarding: a) Circulated air flows; b) Measured methane and carbon dioxide concentrations; c) Absolute flows registered; d) Accumulation capacity of gas in the deposit; e) Gas concentrations and pressure in the massif. - Existing evidences and documentations regarding the previous gas occurrences and their manner of manifestation; - Establishing the way in which the gas is released into the underground atmosphere of the mine workings. Based on the observations and on the carried out measurements, on the analysis of the studied geological and mining elements, there has been made the classification proposal of the Ocnele Mari salt mine from the point of view of gas emissions (methane and carbon dioxide)

Managing the Dust Degree –Related Risks in Valea Jiului Collieries: A Synthesis

Abstract The paper aims to make a synthesis regarding the risks associated with the presence of industrial dust in the underground atmosphere of the coal mines. Thus, in the first part of it are presented relevant aspects regarding the health risk associated with the exposure to silica dust, as well as the flammability and explosiveness of the coal dust, in correlation with the mechanism of the explosion. The second part is dedicated to identifying and substantiating measures to combat the explosiveness of coal dust. In presenting the mentioned measures, the emphasis is placed on highlighting the scope and the specific advantages and disadvantages of each measure, with particular emphasis on the possibilities offered by the use of less employed techniques in mining operations in the Jiu Valley, such as it is, for example, the treatment of mining works with hygroscopic substances. The purpose of the authors is to offer the experts in the field of management of occupational safety and health in the mining industry an overview, in conjunction with specific information elements that facilitate the decision-making processes regarding the minimization of the hazards associated with the degree of coal dustiness in the Jiu Valley collieries.

Hydrogeological control on carbon dioxide input into the atmosphere of the Chauvet-Pont d'Arc cave.

Carbon dioxide (CO2) concentration (CDC) is an essential parameter of underground atmospheres for safety and cave heritage preservation. In the Chauvet cave (South France), a world heritage site hosting unique paintings dated 36,000years BP, a high-sensitivity monitoring, ongoing since 1997, revealed: 1) two compartments with a spatially uniform CDC, a large volume (A) (40,000 to 80,000m3) with a mean value of 2.20±0.01% vol. in 2016, and a smaller remote room (B) (2000m3), with a higher mean value of 3.42±0.01%; 2) large CDC annual variations with peak-to-peak amplitude of 2% and 1.6% in A and B, respectively; 3) long-term changes, with an increase of CDC and of its annual amplitude since 1997, then faster since 2013, reaching a maximum of 4.4% in B in 2017, decreasing afterwards. While a large effect of seasonal ventilation is ruled out, monitoring of seepage at two dripping points indicated that the main control of CDC seasonal reduction was transient infiltration. During periods of water deficit, calculated from surface temperature and rainfall, CDC systematically increased. The carbon isotopic composition of CO2, correlated with water excess, is consistent with a time-varying component of CO2 seeping from above. The CO2 flux, which is the primary driver of CDC in A and B, inferred using box modelling, was found to confirm the relationship between water excess and reduced CO2 flux into A, compatible with a more constant flux into B. A buoyancy-driven horizontal CO2 flow model in the vadose zone, hindered by water infiltration, is proposed. Similarly, pluri-annual and long-term CDC changes can likely be attributed to variations of water excess, but also to increasing vegetation density above the cave. As CDC controls the carbonate geochemistry, an increased variability of CDC raises concern for the preservation of the Chauvet cave paintings.

Comprehensive consultation model for explosion risk in mine atmosphere-CCMER

Mine gas explosion is one of the most feared hazards in the coal industry worldwide. More often one gas explosion related accident can cause the death of multiple coal miners. Examination of recent mine explosion disasters that have occurred in the worldwide reveals that most explosions originated from or around the sealed areas. Therefore, a good understanding of the atmospheric status in a sealed coal mine area is crucial in preventing and reducing accidents associated with mine combustible gases and also for planning and implementing a mine rescue strategy. In this paper, a PC based computer gas explosion consultation software model developed by the authors is introduced. This model is called CCMER (Comprehensive Consultation Model for Explosion Risk in Mine Atmosphere). The computer model is a comprehensive, reliable and user-friendly one. The nature of “comprehensive” means the model can be used to consult the explosibility of a gas sample taken from underground atmosphere, can assist engineers to know how explosion dangerous the situation is or what the risk degree is for a not-explosive atmosphere, and also can perform quantified analyses on the changing time span between not-explosive state and explosive state to guide the recuse works. All of those works are very important to mine operators understanding the mine atmosphere and then taking proper measures to control the potential risk. In addition to that, usages of developed computer program are also very easy. Users can operate the program without possessing an in-depth knowledge on computer and mathematical theory. Until today, CCMER has been successfully employed in numerous cases of designing and assessing various mine atmospheres during the past decades. The reliability of mathematical models used in CCMER has also been proven by such applications.

Controlling 212Bi to 212Pb activity concentration ratio in thoron chambers

It is necessary to establish a reference atmosphere in a thoron chamber containing various ratios of 212Bi to 212Pb activity concentrations (C(212Bi)/C(212Pb)) to simulate typical environmental conditions (e.g., indoor or underground atmospheres). In this study, a novel method was developed for establishing and controlling C(212Bi)/C(212Pb) in a thoron chamber system based on an aging chamber and air recirculation loops which alter the ventilation rate. The effects of main factors on the C(212Bi)/C(212Pb) were explored, and a steady-state theoretical model was derived to calculate the ratio. The results show that the C(212Bi)/C(212Pb) inside the chamber is mainly dependent on ventilation rate. Ratios ranging from 0.33 to 0.83 are available under various ventilation. The stability coefficient of the ratios is better than 7%. The experimental results are close to the theoretical calculated results, which indicates that the model can serve as a guideline for the quantitative control of C(212Bi)/C(212Pb).

Molecular adaptive convergence in the α-globin gene in subterranean octodontid rodents

Tuco-tucos (Ctenomys) and related coruros (Spalacopus) are South American subterranean rodents. An energetically demanding lifestyle within the hypoxic/hypercapnic underground atmosphere may change the selective regime on genes involved in O2 transport in blood. In addition, some species of tuco-tucos may be found at high altitude, thus facing additional reductions in changes O2 availabily. We examined sequence variation in the alpha globin subunit gene of hemoglobine in these lineages, within a robust phylogenetic context. Using different approaches (classical and Bayesian maximum likelihood (PAML/Datamonkey) and alternatives methods (TreeSAAP)) we found at least 2 sites with evidence of positive selection in the basal branch of Octodontidae, but not in tuco-tucos. These results suggest some adaptive changes associated to fossoriality, but not strictly to life underground.

Role of soil pore structure in water infiltration and CO2 exchange between the atmosphere and underground air in the vadose zone: A combined laboratory and field approach

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.

Determinants of rodent longevity in the chaperone-protein degradation network.

Proteostasis is an integral component of healthy aging, ensuring maintenance of protein structural and functional integrity with concomitant impact upon health span and longevity. In most metazoans, increasing age is accompanied by a decline in protein quality control resulting in the accrual of damaged, self-aggregating cytotoxic proteins. A notable exception to this trend is observed in the longest-lived rodent, the naked mole-rat (NMR, Heterocephalus glaber) which maintains proteostasis and proteasome-mediated degradation and autophagy during aging. We hypothesized that high levels of the proteolytic degradation may enable better maintenance of proteostasis during aging contributing to enhanced species maximum lifespan potential (MLSP). We test this by examining proteasome activity, proteasome-related HSPs, the heat-shock factor 1 (HSF1) transcription factor, and several markers of autophagy in the liver and quadriceps muscles of eight rodent species with divergent MLSP. All subterranean-dwelling species had higher levels of proteasome activity and autophagy, possibly linked to having to dig in soils rich in heavy metals and where underground atmospheres have reduced oxygen availability. Even after correcting for phylogenetic relatedness, a significant (p < 0.02) positive correlation between MLSP, HSP25, HSF1, proteasome activity, and autophagy-related protein 12 (ATG12) was observed, suggesting that the proteolytic degradation machinery and maintenance of protein quality play a pivotal role in species longevity among rodents.

Stationary and transient thermal states of barometric pumping in the access pit of an underground quarry

The transition zone between free and underground atmospheres hosts spectacular phenomena, as demonstrated by temperature measurements performed in the 4.6m diameter and 20m deep vertical access pit of an abandoned underground quarry located in Vincennes, near Paris. In summer, a stable stratification of the atmosphere is maintained, with coherent temperature variations associated with atmospheric pressure changes, with a barometric tide S2 larger than 0.1°C peak to peak. When the winter regime of turbulent cold air avalanches is initiated, stratification with pressure induced signals can be restored transiently in the upper part of the pit, while the lower part remains fully mixed and insensitive to pressure variations. The amplitude of the pressure to temperature transfer function increases with frequency below 5×10−4Hz, with values at 3×10−5Hz varying from 0.1°C·hPa−1 at the bottom up to 2°C·hPa−1 towards the top of the pit. These temperature variations are accounted for by cave breathing, which is pressure induced motion of air amplified by the large volume of the quarry. This understanding is supported by a numerical model including advective heat transport, heat diffusion, and heat exchange with the pit walls. Mean lifetime in the pit is of the order of 9 to 13h, and barometric pumping results in an effective ventilation rate of the quarry of the order of 10−7s−1. This study illustrates the important role of barometric pumping in heat and matter transport between atmosphere and lithosphere. The resulting stationary and transient states, revealed in this pit, are probably a general feature of functioning interface systems, and therefore are an important aspect to consider in problems of contaminant transport, or the preservation of precious heritage such as rare ecosystems or painted caves.

Revised Explosibility Diagram to Judge Best Practice of Controlling an Explosive Gas-Mixture

Gas explosions or mine fires present the safety threats for coal miners or mine rescues members. For an explosive atmosphere in the underground mine, careful determination of its explosibility status and applying some mitigations to switch an explosive atmosphere into a non-explosive one are very important for any underground rescues or a mine fire extinguishment. However, due to the complicated compositions in an underground sealed atmosphere, accurate determination of the explosibility of such atmosphere status is always a knotty problem for mining engineers. Beside of that, a proper estimation method for the needed time span when an explosive atmosphere is artificially or naturally changed into a non-explosive is also urgently desired. In order to improve the mine safety, this paper is going to address such mentioned problems. The original Coward explosibility diagram is modified with handling the combination effects of different inert gases for more accurate determining the explosibility of an underground sealed atmosphere which consists of complex gas compositions. Then, based on the revised explosibility diagram, a set of mathematical equations are theoretically derived to estimate the inertisation time of a sealed mine atmosphere by using different inerting approaches. Such research efforts can help mine operators understand the risk and provide a tool to control such atmosphere away from dangerous conditions. In order to demonstrate the research findings, at the end of the paper, the explosibility of gas sample taken from a real mine has been analyzed by using the revised Coward diagram. Also, the different inertisation time durations of various mitigation measures for such underground atmosphere have also been calculated.

Two mitochondrial genes under episodic positive selection in subterranean octodontoid rodents

Tuco-tucos (Ctenomys) and related coruros (Spalacopus) are South American subterranean rodents. An energetically demanding lifestyle within the hypoxic, underground atmosphere may change the selective regime on oxidative phosphorylation. We examined whether weak and/or episodic positive directional selection affected the evolution of two mitochondrial genes (COX2, CytB), in a background of purifying selection in these lineages. We estimated rates of synonymous (dS) and non-synonymous (dN) substitutions and found: 1) significantly higher dN/dS ratio in subterranean groups relative to non-subterranean related species, and 2) two codons in each gene under episodic selection: 94 and 277 of COX2 and 269 and 307 of CytB.

A prototype mass spectrometer for in situ analysis of cave atmospheres

Research in cave environments has many applications: studying local hydrogeologic activity, paleoclimate studies, analyzing white nose syndrome in bat populations, analogs for underground atmospheres in mining facilities, carbon sequestration efforts, and terrestrial analogs for planetary caves. The atmospheres of many caves contain tracers of current geological and biological activity, but up to this point, in situ studies have been limited to sensors that monitor individual components of the cave atmosphere. A prototype cave mass spectrometer system was assembled from commercial off-the-shelf parts to conduct surveys of atmospheric compositions inside four local Texas caves and to perform atmospheric analysis of two aquifer wellheads to a depth of 60 m. We found increased levels of CO(2) in all caves and, surprisingly, increased levels of O(2) in Bracken Bat Cave. Aquifer wellhead measurements showed indications of methane, other hydrocarbons, and other constituents not anticipated.

The role of near-surface cavities in the carbon dioxide cycle of karst areas: evidence from the Carburangeli Cave Natural Reserve (Italy)

Hydrological, chemical and meteorological data collected during the years 2006–2007 at Carburangeli Cave (Italy) have provided new insights on the near-surface cycle of carbon dioxide, particularly concerning the role played by fractures and karst conduits. Carbon dioxide is trapped in the underground atmosphere essentially when its temperature is lower than the outer one. By contrast, convective air circulation disperses all the excess CO2 in the external environment when the thermal differential is inverted. The network of fractures and karst conduits then works, in the vadose zone, as a re-circulator of CO2 from the soil to the atmosphere. The total amount of CO2 fixed in the underground is controlled, during the wet season, by the amount of infiltrating waters, which act as the main carrier of CO2 in the subsoil. By contrast, during the dry season, gravitational drainage is responsible for the accumulation of carbon dioxide in the underground voids. The quantitative balance demonstrated that the degassed CO2 amounts are one order of magnitude higher than the dissolved CO2. In light of this, if the near-surface outgassing processes are not taken into account, CO2 budgets may be affected by significant errors.

Radon exchange dynamics in a karst system investigated by radon continuous measurements in water: first results

In 2008 the underground Karst Laboratory of Bossea Cave started research on radon exchange dynamics between bedrock, cave waters (main collector and percolations) and indoor underground atmosphere. Radon air concentrations, normally high, increase more and more during the collector's floods. An explanation of this is a radon-water solubilisation process more effective in flood events, because of a greater rock-water contact surface. Radon is then carried by water into the cave and released into the air. To verify this, continuous measurements of radon concentration are needed not only in the air, but also in the waters of the cave. So a new device for continuous radon monitoring in water was tested, connected to the AlphaGuard radon monitor. For the first 6 months of 2010, for different sections of the cave, the correlations between radon in the air, radon in the waters and the collector's stream flow fluctuations were presented and discussed.

Gamma radiation dose rate in indoor, outdoor and underground atmosphere around Tehri dam project, Uttarakhand, India

The natural pollution level due to gamma radiation was measured in about 22 residential houses around the Tehri Dam Project in Uttarakhand state by using Environmental Radiation Dosimeter. Both urban and rural houses were selected for the measurements. The recorded gamma dose rate in indoor atmosphere was found to vary from 25.1 μR/h to 67 μR/h with a mean value 38.6 μR/h whereas in traditional rural houses the obtained values varied from 42.6 μR/h to 83.5 μR/h with mean value 60.3 μR/h. In outdoor atmosphere, it was found to vary from 25.1 μR/h to 60 μR/h with an average value 35.8 μR/h. It is observed that the dose rates are higher in rural houses than that in modern houses. Efforts have also been made to observe deviation of dose rate in the underground (Power House) atmosphere of Tehri Dam Project in vertical and horizontal mode. It was observed that dose rate remain almost same in horizontal mode, but a significant variation has been found in the vertical mode. In addition, the variation of dose rate with type of building material, trend and mode of construction of houses and the age of houses are also discussed in detail.

Towards Safer Working: The Hazards and the Risks of Introducing Electrical Equipment in British Coal Mines up to About 1930

The need for on-going and co-ordinated research, development and testing in any industry is generally essential to its continued well being. However, in the case of the coal mining industry, where potentially explosive atmospheres are often present, the need for fundamental knowledge is of paramount importance. Whilst the dangers of explosion arising from the ignition of firedamp and/or coal dust had long been a cause of concern and subject to much investigation, the introduction of electrical equipment into such hazardous underground atmospheres, from about 1880 onwards, brought with it another, hitherto, unknown source of ignition — that of open-sparking. Given the readily demonstrable advantages that electricity had over the existing motive powers of steam and compressed air its rapid and increasing use was inevitable. However, the risks arising from open-sparking had to be first identified and then techniques developed to ensure that such equipment could operate safely. Much of the early investigations and development was undertaken by the equipment manufacturers themselves, a few academic institutions and even the occasional individual. The absence of any co-ordinated research or guidance by official or Government bodies resulted in a fragmented in an ad hoc and, in some cases, confusing situation. This paper begins by outlining the dangers of firedamp and coal dust explosions, and some of the early research activity, before considering the problem of open-sparking itself. It then discusses the early attempts by various bodies and individuals to understand the mechanism and the development of various techniques to prevent open-sparking, before concluding that, had a central or governmental body been established at an earlier date to co-ordinate both these areas of research, then the introduction of electricity underground into coal mines would probably have been achieved more rapidly, with greater confidence and more safely.

Construção de um modelo computacional para o circuito de ventilação da Mina Esperança

A ventilação em uma mina tem como principal objetivo o fornecimento de um fluxo de ar puro a todos os locais de trabalho em subsolo, em quantidades suficientes para assegurar as condições de higiene e segurança dos trabalhadores. A análise da eficiência ou do dimensionamento de um circuito de ventilação pode ser feita por meio de técnicas diretas de análise (algoritmo de Hardy Cross e Leis de Kirchhoff). Essas técnicas são extremamente trabalhosas quando se dispõe de um circuito de muitas malhas. Para uma análise mais detalhada ou previsão de mudanças no circuito de ventilação, empregam-se técnicas de simulação computacional. Essas técnicas foram utilizadas para a construção de um modelo computacional da distribuição do fluxo de ar para a Mina Esperança (SC), tendo como objetivo a adequação do atual circuito de ventilação a NR-22 e o aumento da quantidade de ar fornecida a cada painel em lavra para 2000 m³/min. Na construção do modelo foram utilizados dados de vazão, diferença de pressão estática, geometria das galerias e as características dos ventiladores. Esses dados, correlacionados pelo simulador, indicaram valores de vazão e pressão compatíveis aos medidos na mina, com diferenças entre os valores simulados e medidos de até 20%, sendo essa diferença adotada, pela equipe de trabalho, para validação dos modelos computacionais. De posse do modelo validado, estudaram-se diversos cenários de lavra futura, antevendo os valores de vazão e pressão a serem encontrados. Portanto as técnicas computacionais para a análise de redes de fluxo comprovaram ser uma importante ferramenta de projeto, diminuindo custos e racionalizando os recursos disponíveis.