Early hypogenic carbonic acid speleogenesis in unconfined  limestone aquifers by upwelling deep-seated waters  with high CO&lt;sub&gt;2&lt;/sub&gt; concentration: a modelling approach

Abstract. Here we present results of digital modelling of a specific setting of hypogenic carbonic acid speleogenesis (CAS). We study an unconfined aquifer where meteoric water seeps through the vadose zone and becomes saturated with respect to calcite when it arrives at the water table. From below, deep-seated water with high pCO2 and saturated with respect to calcite invades the limestone formation by forced flow. Two flow domains arise that host exclusively water from the meteoric or deep-seated source. They are separated by a water divide. There by dispersion of flow, a fringe of mixing arises and widening of the fractures is caused by mixing corrosion (MC). The evolution of the cave system is determined by its early state. At sites with high rates of fracture widening, regions of higher hydraulic conductivity are created. They attract flow and support one-by-one mixing with maximal dissolution rates. Therefore, the early evolution is determined by karstification originating close to the input of the upwelling water and at the output at a seepage face. In between these regions, a wide fringe of moderate dissolution is present. In the later stage of evolution, this region is divided by constrictions that originate from statistical variations of fracture aperture widths that favour high dissolution rates and focus flow into this region. This MC-fringe instability is an intrinsic property of cave evolution and is present in all scenarios studied. We have investigated the influence of defined regions with higher fracture aperture widths. These determine the cave patterns and suppress MC-fringe instabilities. We have discussed the influence of the ratio of upwelling water flux rates on the rates of meteoric water. This ratio specifies the position of the mixing fringe and consequently that of the cave system. In a further step, we have explored the influence of time-dependent meteoric recharge. Furthermore, we have modelled scenarios where waters are undersaturated with respect to calcite. These findings give important insight into mechanisms of CAS in a special setting of unconfined aquifers. They also have implications for the understanding of corresponding sulfuric acid speleogenesis (SAS).

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Early hypogene Carbonic Acid Speleogenesis in unconfined limestone aquifers by upwelling deep-seated waters with high CO<sub>2</sub> concentration: A first modelling approach

10.5194/hess-2020-473 ◽

2020 ◽

Author(s):

Franci Gabrovšek ◽

Wolfgang Dreybrodt

Keyword(s):

Meteoric Water ◽

Carbonic Acid ◽

Water Flux ◽

Intrinsic Property ◽

Unconfined Aquifer ◽

Forced Flow ◽

High Pco2 ◽

Fracture Aperture ◽

Dissolution Rates ◽

Cave System

Abstract. Hypogene caves originate from upwelling deep-seated waters loaded with CO2 that mix with meteoric waters in a limestone aquifer. Here we present first results on digital modelling of Carbonic Acid Speleogenesis (CAS). We study an unconfined aquifer where meteoric water seeps through the vadose zone and becomes saturated with respect to calcite when it arrives at the water table. From below deep-seated water with high pCO2 and saturated with respect to calcite invades the limestone formation by forced flow. Two flow domains arise that host exclusively water from the meteoric or the deep-seated source. They are separated by a water divide. There by dispersion of flow, a fringe of mixing arises and widening of the fractures is caused by mixing corrosion (MC). The evolution of the cave system is determined by its early state. At sites with high rates of fracture widening regions of higher hydraulic conductivity are created. They attract flow and support one by one mixing with maximal dissolution rates. Therefore, the early evolution is determined by karstification originating close to the input of the upwelling water and at the output at a seepage face. In between these regions, a wide fringe of moderate dissolution is present. In the later stage of evolution, this region is divided by constrictions that originate from statistical variations of fracture aperture widths that favour high dissolution rates and focus flow into this region. This MC-fringe-instability is an intrinsic property of cave evolution and is present in all scenarios studied. We have investigated the influence of defined regions with higher fracture aperture widths. These determine the cave patterns and suppress MC-fringe-instabilities. We have discussed the influence of the ratio of upwelling water flux rates to the rates of meteoric water. This ratio specifies the position of the mixing fringe and consequently that of the cave system. In a further step, we have explored the influence of time dependent meteoric recharge. Furthermore, we have modelled scenarios where waters are undersaturated with respect to calcite. These findings give important insight into mechanisms of hypogene speleogenesis. They also have implications to the understanding of sulfuric acid speleogenesis (SAS).

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Fractional governing equations of transient groundwater flow in unconfined aquifers with multi-fractional dimensions in fractional time

Earth System Dynamics ◽

10.5194/esd-11-1-2020 ◽

2020 ◽

Vol 11 (1) ◽

pp. 1-12 ◽

Cited By ~ 1

Author(s):

M. Levent Kavvas ◽

Tongbi Tu ◽

Ali Ercan ◽

James Polsinelli

Keyword(s):

Groundwater Flow ◽

Governing Equation ◽

Water Flux ◽

Unconfined Aquifer ◽

Saturated Porous Media ◽

Unconfined Aquifers ◽

Heavy Tailed ◽

Consistent Equation ◽

Fractional Dimensions ◽

Fractional Space

Abstract. In this study, a dimensionally consistent governing equation of transient unconfined groundwater flow in fractional time and multi-fractional space is developed. First, a fractional continuity equation for transient unconfined groundwater flow is developed in fractional time and space. For the equation of groundwater motion within a multi-fractional multidimensional unconfined aquifer, a previously developed dimensionally consistent equation for water flux in unsaturated/saturated porous media is combined with the Dupuit approximation to obtain an equation for groundwater motion in multi-fractional space in unconfined aquifers. Combining the fractional continuity and groundwater motion equations, the fractional governing equation of transient unconfined aquifer flow is then obtained. Finally, two numerical applications to unconfined aquifer groundwater flow are presented to show the skills of the proposed fractional governing equation. As shown in one of the numerical applications, the newly developed governing equation can produce heavy-tailed recession behavior in unconfined aquifer discharges.

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Kinetics of carbonate mineral dissolution in CO2-acidified brines at storage reservoir conditions

Faraday Discussions ◽

10.1039/c6fd00048g ◽

2016 ◽

Vol 192 ◽

pp. 545-560 ◽

Cited By ~ 12

Author(s):

Cheng Peng ◽

Benaiah U. Anabaraonye ◽

John P. Crawshaw ◽

Geoffrey C. Maitland ◽

J. P. Martin Trusler

Keyword(s):

Kinetic Model ◽

Carbonic Acid ◽

Dissolution Kinetics ◽

Carbonate Reservoir ◽

Mineral Dissolution ◽

Direct Reaction ◽

Carbonate Mineral ◽

Dissolution Rates ◽

Saturated Water ◽

Kinetics Of

We report experimental measurements of the dissolution rate of several carbonate minerals in CO2-saturated water or brine at temperatures between 323 K and 373 K and at pressures up to 15 MPa. The dissolution kinetics of pure calcite were studied in CO2-saturated NaCl brines with molalities of up to 5 mol kg−1. The results of these experiments were found to depend only weakly on the brine molality and to conform reasonably well with a kinetic model involving two parallel first-order reactions: one involving reactions with protons and the other involving reaction with carbonic acid. The dissolution rates of dolomite and magnesite were studied in both aqueous HCl solution and in CO2-saturated water. For these minerals, the dissolution rates could be explained by a simpler kinetic model involving only direct reaction between protons and the mineral surface. Finally, the rates of dissolution of two carbonate-reservoir analogue minerals (Ketton limestone and North-Sea chalk) in CO2-saturated water were found to follow the same kinetics as found for pure calcite. Vertical scanning interferometry was used to study the surface morphology of unreacted and reacted samples. The results of the present study may find application in reactive-flow simulations of CO2-injection into carbonate-mineral saline aquifers.

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Buffer systems in the rumen of sheep. I. pH and bicarbonate concentration in relationship to pCO2.

Australian Journal of Agricultural Research ◽

10.1071/ar9550115 ◽

1955 ◽

Vol 6 (1) ◽

pp. 115 ◽

Cited By ~ 30

Author(s):

AW Turner ◽

VE Hodgetts

Keyword(s):

Carbon Dioxide ◽

Carbonic Acid ◽

High Pco2 ◽

Bicarbonate Concentration ◽

Bulk Fluid ◽

Ruminal Fluid ◽

Arterial Blood ◽

Wide Range ◽

The Relationship ◽

Hasselbalch Equation

Experiments are described which emphasize the importance of avoiding loss of carbon dioxide when estimating the pH or bicarbonate concentration of ruminal fluid. The high pCO2 of ruminal fluid is stressed; this may be 10 times or more as great as that of arterial blood. The relationship between pCO2, pH, and [HCO3-] was examined in terms of the Henderson-Hasselbalch equation over a wide range of pCO2. From this, the pK1' of the carbonic acid system in four ruminal fluids was determined as 6.21-6.28, mean 6.25. The higher pH of saliva-free samples of ruminal fluid withdrawn by suction through a tube passed down the oesophagus, as compared with that of the bulk fluid obtained through a ruminal fistula, is considered to be due to loss of carbon dioxide during collection. A better estimate of intraruminal pH is obtained, even when salivary contamination occurs, if such samples are equilibrated with a sample of the animal's ruminal gas; if this is not practicable, an arbitrary gas mixture of high pCO2, e.g. 50 per cent. carbon dioxide and nitrogen, may be used.

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Dissolution rates and vadose zone drainage from strontium isotope measurements of groundwater in the Pasco Basin, WA unconfined aquifer

Journal of Hydrology ◽

10.1016/j.jhydrol.2005.07.044 ◽

2006 ◽

Vol 321 (1-4) ◽

pp. 39-58 ◽

Cited By ~ 23

Author(s):

Michael J. Singleton ◽

Katharine Maher ◽

Donald J. DePaolo ◽

Mark E. Conrad ◽

P. Evan Dresel

Keyword(s):

Vadose Zone ◽

Unconfined Aquifer ◽

Strontium Isotope ◽

Dissolution Rates ◽

Isotope Measurements

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Geological modelling of clay diagenesis in sandstones

Clay Minerals ◽

10.1180/claymin.1982.017.1.03 ◽

1982 ◽

Vol 17 (1) ◽

pp. 5-22 ◽

Cited By ~ 62

Author(s):

Andrew Hurst ◽

Hilary Irwin

Keyword(s):

Meteoric Water ◽

Sea Water ◽

Water Flux ◽

Sedimentary Basins ◽

Hydraulic Head ◽

Primary Sources ◽

Diffusion Controlled ◽

Dissolved Species ◽

Marine Facies ◽

Diagenetic Reactions

AbstractPorewater composition is the main control on diagenetic reactions in sandstones. Porewater has two possible contrasting primary sources: (i) fresh meteoric water, which is dilute and acidic, (ii) sea-water, which is alkaline and more concentrated than meteoric water. During burial, unstable minerals equilibrate with these porewaters, thus increasing the concentrations of dissolved species. A simple manometer model is used to describe the diagenesis of interconnected (fluvial or deltaic) sandstones. This model illustrates the following geological relationships: (a) a hydraulic head causes meteoric waters to penetrate deep into sedimentary basins, typically generating authigenic kaolinite; (b) decrease of the hydraulic head (by lowering the land level or by raising sea level) causes concentrated brines to rise within the basin, typically forming illitic cements; (c) enclosed sandstones (marine facies) are isolated from meteoric water flux and only receive fluxes when fault-induced or when uplifted. Kaolinite morphology and distribution are identified as being flux- or diffusion-controlled.

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HYPOGENIC FEATURES IN MARONIA CAVE, THRACE, GREECE. EVIDENCE FROM MORPHOLOGIES AND FLUID INCLUSIONS.

Bulletin of the Geological Society of Greece ◽

10.12681/bgsg.11260 ◽

2017 ◽

Vol 43 (2) ◽

pp. 948 ◽

Cited By ~ 1

Author(s):

M. Vaxevanopoulos ◽

V. Melfos

Keyword(s):

Fluid Inclusion ◽

Meteoric Water ◽

Elevated Temperatures ◽

Middle Eocene ◽

Morphological Characteristics ◽

Hydrothermal Fluids ◽

Cave System ◽

Karst Systems ◽

Two Peaks ◽

Of Greece

The evolution of caves is usually controlled by meteoric water seepage into karst systems (epigenic process). In some cases, caves are formed by ascending fluids the aggressiveness of which is gained in depth. Such cavities are defined as hypogenic. Many caves considered previously as epigenic are now reinterpreted as hypogenic. Most Greek hypogenic caves are related with confined speleogenesis in karstic rocks near to impermeable rock exposures. At the present study the hypogenic features of the Maronia cave in Thrace of Greece, are described. The cave system is developed in a relatively thin layer of eroded Nummulitic limestones with a Middle Eocene age. Medium scale morphological characteristics such as cupolas and feeders indicate rising flow of solutions. In addition, fluid inclusion studies in selected calcite spars from the cave show elevated temperatures of formation (93 to 164ºC with two peaks at 100 and 140 ºC) from circulating hydrothermal fluids.

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Hydro-geochemical and isotopic characterization of the deep groundwater from coal bearing in Mining district, Northern Anhui Province, China

Water Practice & Technology ◽

10.2166/wpt.2013.033 ◽

2013 ◽

Vol 8 (3-4) ◽

pp. 330-341 ◽

Cited By ~ 1

Author(s):

Song Chen ◽

He Rong Gui ◽

Lin Hua Sun

Keyword(s):

Meteoric Water ◽

Carbonic Acid ◽

Major Ions ◽

Anhui Province ◽

Mining District ◽

Multivariate Statistical ◽

Water Line ◽

Meteoric Water Line ◽

Multivariate Statistical Approach ◽

Isotopic Characterization

Hydro-geochemistry and isotopes were used to understand the geochemical character and origin of the groundwater from coal bearing aquifer in Northern Anhui province, China. Twenty three groundwater samples were collected, and the isotopic composition δD, δ18O and major ions were analyzed, conventional graphical and multivariate statistical approach was completed and the result showed: three groups of groundwater could be divided form the rectangular field, the Ca-Mg-Cl, Na-Cl-SO4 and Na-HCO3 type water; the feldspar weathering is dominating weathering process, whereas, the sulfuric acid is the weathering agent along with the carbonic acid; the groundwater mainly supplied from the meteoric water for all the plots are below the local meteoric water line and global meteoric water line, the values of δD are drifted obviously, what could be caused by the exchange reaction of δD between groundwater and alkyl.

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Fractional governing equations of transient groundwater flow in unconfined aquifers with multi-fractional dimensions in fractional time

10.5194/esd-2019-37 ◽

2019 ◽

Author(s):

M. Levent Kavvas ◽

Tongbi Tu ◽

Ali Ercan ◽

James Polsinelli

Keyword(s):

Groundwater Flow ◽

Governing Equation ◽

Water Flux ◽

Unconfined Aquifer ◽

Saturated Porous Media ◽

Numerical Application ◽

Unconfined Aquifers ◽

Consistent Equation ◽

Fractional Dimensions ◽

Fractional Space

Abstract. In this study, a dimensionally-consistent governing equation of transient unconfined groundwater flow in fractional time and multi-fractional space is developed. First, a fractional continuity equation for transient unconfined groundwater flow is developed in fractional time and space. For the equation of groundwater motion within a multi-fractional multi-dimensional unconfined aquifer, a previously-developed dimensionally consistent equation for water flux in unsaturated/saturated porous media is combined with the Dupuit approximation to obtain an equation for groundwater motion in multi-fractional space in unconfined aquifers. Combining the fractional continuity and groundwater motion equations, the fractional governing equation of transient unconfined aquifer flow is then obtained. Finally, a numerical application to an unconfined aquifer groundwater flow problem is presented to show the skills of the proposed fractional governing equation.

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