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Enviroscan Ukrainian Institute of Speleology and Karstology


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Speleology in Kazakhstan

Shakalov on 04 Jul, 2018
Hello everyone!   I pleased to invite you to the official site of Central Asian Karstic-Speleological commission ("Kaspeko")   There, we regularly publish reports about our expeditions, articles and reports on speleotopics, lecture course for instructors, photos etc. ...

New publications on hypogene speleogenesis

Klimchouk on 26 Mar, 2012
Dear Colleagues, This is to draw your attention to several recent publications added to KarstBase, relevant to hypogenic karst/speleogenesis: Corrosion of limestone tablets in sulfidic ground-water: measurements and speleogenetic implications Galdenzi,

The deepest terrestrial animal

Klimchouk on 23 Feb, 2012
A recent publication of Spanish researchers describes the biology of Krubera Cave, including the deepest terrestrial animal ever found: Jordana, Rafael; Baquero, Enrique; Reboleira, Sofía and Sendra, Alberto. ...

Caves - landscapes without light

akop on 05 Feb, 2012
Exhibition dedicated to caves is taking place in the Vienna Natural History Museum   The exhibition at the Natural History Museum presents the surprising variety of caves and cave formations such as stalactites and various crystals. ...

Did you know?

That fault breccia is the assemblage of broken rock fragments frequently found along faults. the fragments may vary in size from inches to feet.?

Checkout all 2699 terms in the KarstBase Glossary of Karst and Cave Terms


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Featured articles from Cave & Karst Science Journals
Chemistry and Karst, White, William B.
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Featured articles from other Geoscience Journals
Karst environment, Culver D.C.
Mushroom Speleothems: Stromatolites That Formed in the Absence of Phototrophs, Bontognali, Tomaso R.R.; D’Angeli Ilenia M.; Tisato, Nicola; Vasconcelos, Crisogono; Bernasconi, Stefano M.; Gonzales, Esteban R. G.; De Waele, Jo
Calculating flux to predict future cave radon concentrations, Rowberry, Matt; Marti, Xavi; Frontera, Carlos; Van De Wiel, Marco; Briestensky, Milos
Microbial mediation of complex subterranean mineral structures, Tirato, Nicola; Torriano, Stefano F.F;, Monteux, Sylvain; Sauro, Francesco; De Waele, Jo; Lavagna, Maria Luisa; D’Angeli, Ilenia Maria; Chailloux, Daniel; Renda, Michel; Eglinton, Timothy I.; Bontognali, Tomaso Renzo Rezio
Evidence of a plate-wide tectonic pressure pulse provided by extensometric monitoring in the Balkan Mountains (Bulgaria), Briestensky, Milos; Rowberry, Matt; Stemberk, Josef; Stefanov, Petar; Vozar, Jozef; Sebela, Stanka; Petro, Lubomir; Bella, Pavel; Gaal, Ludovit; Ormukov, Cholponbek;
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Your search for kinetics (Keyword) returned 110 results for the whole karstbase:
Showing 16 to 30 of 110
EARLY DEVELOPMENT OF KARST SYSTEMS .1. PREFERENTIAL FLOW PATH ENLARGEMENT UNDER LAMINAR-FLOW, 1994,
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Groves C. G. , Howard A. D. ,
Modeling of flow and solutional processes within networks of interconnected conduits in limestone aquifers indicates that enlargement occurs very selectively during the early stages of karst aquifer development under laminar flow. If initial flow paths are uniform in size, almost all enlargement occurs along a single set of connected conduits that lie along a direct path between recharge and discharge locations and are aligned along the hydraulic gradient. With a sufficiently large variation in initial aperture widths, enlargement occurs along the flow path offering the least resistance to flow, but since flow rates in laminar flow are proportional to the fourth power of diameter but only linearly proportional to hydraulic gradient, the preferentially enlarged set of fractures may follow an indirect path. Results disfavor earlier suggestions that nonselective cave patterns result from artesian flows (at least under laminar flow conditions) and that all passages should be competitive until the onset of turbulent flow

Recent flowstone growth rates: field measurements and comparison to theoretical results, 1995,
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Baker A. , Smart Pl. ,
The model of calcite precipitation kinetics of D. Buhmann and W. Dreybrodt, based on the rate laws of L.N. Plummer et al., is used to predict cave flowstone growth rates. These theoretically modelled growth rates are compared to actual growth rates of recent samples found in cave and mine sites in southwest England. A good agreement is found between modelled and actual growth rates within the 95% confidence level of the determinations, although in general modelled growth rates overestimate actual growth rate by between 2.4 and 4.7 times. Several reasons for this overestimation are discussed, including uncertainties arising from the experimental data of L.N. Plummer et al., seasonal shut-off of water flow onto the flowstones and significant variations in the growth rate determining parameters during the period of flowstone growth. For one flowstone an underestimation of growth rate is observed and is explained by the presence of rimstone pools which pond water on the sample surface

IMPACT OF AN EXCEPTIONAL STORM EPISODE ON THE FUNCTIONING OF KARST SYSTEM - THE CASE OF THE 22/9/92 STORM AT VAISON-LA-ROMAINE (VAUCLUSE, FRANCE), 1995,
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Lastennet R. , Mudry J. ,
Karstification is a slow geodynamical process, controlled by the interaction between dissolution kinetics and flow dynamics. Moreover, mechanisms of network clogging by calcite precipitation or non-soluble clay accumulation are slow and continuous phenomena. This evolution of a karst system can be widely modified during exceptional rainfall episodes, such as the 22/09/92 storm (> 300 mm) near Vaison-la-Romaine. Such an impulse can modify the hydraulical behaviour of a massif, by unclogging the outlets of the saturated zone or the drainage network of the aquifer, and change hydrodynamical features of a spring (storage capacity etc.). This phenomenon has been demonstrated in a north Vaucluse karst aquifer whose recession coefficient has increased 7-fold and stored volume divided by 6

HYDRODYNAMIC CONTROL OF INORGANIC CALCITE PRECIPITATION IN HUANGLONG RAVINE, CHINA - FIELD-MEASUREMENTS AND THEORETICAL PREDICTION OF DEPOSITION RATES, 1995,
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Liu Z. H. , Svensson U. , Dreybrodt W. , Yuan D. X. , Buhmann D. ,
Hydrochemical and hydrodynamical investigations are presented to explain tufa deposition rates along the flow path of the Huanglong Ravine, located in northwestern Sichuan province, China, on an altitude of about 3400 m asl. Due to outgassing of CO2 the mainly spring-fed stream exhibits, along a valley of 3.5 km, calcite precipitation rates up to a few mm/year. We have carried out in situ experiments to measure calcite deposition rates at rimstone dams, inside of pools and in the stream-bed. Simultaneously, the downstream evolution of water chemistry was investigated at nine locations with respect to Ca2 Mg2, Na, Cl-, SO42-, and alkalinity. Temperature, pH, and conductivity were measured in situ, while total hardness, Ca-T, and alkalinity have been determined immediately after sampling, performing standard titration methods. The water turned out to be of an almost pure Ca-Mg-HCO3 type. The degassing of CO2 causes high supersaturation with respect to calcite and due to calcite precipitation the Ca2 concentration decreases from 6 . 10(-3) mole/l upstream down to 2.5 . 10(-3) mole/l at the lower course. Small rectangular shaped tablets of pure marble were mounted under different flow regimes, i.e., at the dam sites with fast water flow as well as inside pools with still water. After the substrate samples had stayed in the water for a period of a few days, the deposition rates were measured by weight increase, up to several tens of milligrams. Although there were no differences in hydrochemistry, deposition rates in fast flowing water were higher by as much as a factor of four compared to still water, indicating a strong influence of hydrodynamics. While upstream rates amounted up to 5 mm/year, lower rates of about 1 mm/year were observed downstream. Inspection of the marble substrate surfaces by EDAX and SEM (scanning electron microscope) revealed authigeneously grown calcite crystals of about 10 mu m. Their shape and habit are indicative of a chemically controlled inorganic origin. By applying a mass transfer model for calcite precipitation taking into account the reaction rates at the surface given by Plummer et al. (1978), slow conversion of CO2 into H and HCO3-, and diffusional mass transport across a diffusion boundary layer, we have calculated the deposition rates from the hydrochemistry of the corresponding locations. The calculated rates agree within a factor of two with the experimental results. Our findings confirm former conclusions with respect to fast flow conditions: reasonable rates of calcite precipitation can be estimated in reducing the PWP-rate calculated from the chemical composition of the water by a factor of about ten, thus correcting for the influence of the diffusion boundary layer

EARLY DEVELOPMENT OF KARST SYSTEMS .2. TURBULENT-FLOW, 1995,
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Howard A. D. , Groves C. G. ,
A simulation model developed to explore patterns of fracture enlargement within incipient limestone karst aquifers has been extended to turbulent flow. In contrast to the highly selective passage enlargement that occurs early in cave network development under laminar flow, the transition to turbulent flow results in more general passage enlargement, leading to maze networks when initial fractures are large and hydraulic gradients are high. These results support previously published hypotheses for the development of maze patterns, including formation within structural settings that have created initially large fractures or within flow systems periodically inundated by flooding. Maze development is also favored under turbulent flow when passages are entirely water filled, and where the groundwater flow system is long-lived. By contrast, branched patterns are most common when passages become free-surface subterranean streams, because depression of the piezometric surface along main passages, downcutting along main passages, and possible infilling with sediment of side passages limit the sharing of discharge among interconnected fractures or bedding planes that promote maze development

The dissolution and conversion of Gypsum and Anhydrite., 1996,
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Klimchouk Alexander
The development of karst is a complex system driven by the dissolution of a host rock and the subsequent removal of dissolved matter by moving water. It is the process that, at various stages, initiates or triggers associated processes including erosion, collapse and subsidence. The dissolution of sulphate rocks proceeds by different mechanisms and at different rates to those associated with the dissolution of carbonate rocks. For each rock type different factors influence the process. This chapter is an attempt to summarise the present knowledge of the dissolution chemistry and kinetics of gypsum and anhydrite. These are important for the genetic interpretation of karst features in these rocks. The gypsum-anhydrite-gypsum transitions and recrystallization processes are also addressed, because of their importance to karst development.

Speleogenesis in Gypsum., 1996,
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Klimchouk Alexander
Satisfactory explanation of the origin and development of caves (speleogenesis) is a core problem of karst studies. Karst evolves as a circulation system, organised and interconnected through a conduit structure. Such a system may include superficial inputs and outputs, expressed as or related to karst landforms. However, there may be no such components if the system is represented entirely by conduits as in the case with deep-seated intrastratal karst. The main differences between speleogenesis in gypsum and in carbonate rocks lie in the chemistry and kinetics of their dissolution, in some of the lithological or structural peculiarities of the respective rocks and formations, and in their hydrogeological characteristics. The present chapter considers how these factors influence cave origin and development.

The kinetics of the reaction CO2 + H2O --> H+ + HCO3- as one of the rate limiting steps for the dissolution of calcite in the system H2O - CO2 - CaCO3., 1996,
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Dreybrodt W. , Lauckner J. , Zaihua L. , Svensson U. , Buhmann D.

The kinetics of the reaction CO2?>H? as one of the rate limiting steps for the dissolution of calcite in the system H2O-CO2-CaCO3, 1996,
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Dreybrodt W, Lauckner J, Liu Zh, Svensson U, Buhmann D,
Dissolution of CaCO3 in the system H2O-CO2-CaCO3 is controlled by three rate-determining processes: The kinetics of dissolution at the mineral surface, mass transport by diffusion, and the slow kinetics of the reaction H2O CO2 = H HCO3-. A theoretical model of Buhmann and Dreybrodt (1985a,b) predicts that the dissolution rates depend critically on the ratio V/A of the volume V of the solution and the surface area A of the reacting mineral. Experimental data verifying these predictions for stagnant solutions have been already obtained in the range 0.01 cm < V/A < 0.1 cm. We have performed measurements of dissolution rates in a porous medium of sized CaCO3 particles for V/A in the range of 2 . 10(-4) cm and 0.01 cm in a system closed with respect to CO2 using solutions pre-equilibrated with an initial partial pressure of CO2 of 1 . 10(-2) and 5 . 10(-2) atm. The results are in satisfactory agreement with the theoretical predictions and show that especially for V/A < 10(-3) cm dissolution is controlled entirely by conversion of CO2 into H and HCO3-, whereas in the range from 10(-3) cm up to 10(-1) cm both CO2-conversion and molecular diffusion are the rate controlling processes. This is corroborated by performing dissolution experiments using 0.6 mu molar solutions of carbonic anhydrase, an enzyme enhancing the CO2-conversion rates by several orders of magnitude. In these experiments CO2 conversion is no longer rate limiting and consequently the dissolution rates of CaCO3 increase significantly. We have also performed batch experiments at various initial pressures of CO2 by stirring sized calcite particles in a solution with V/A = 0.6 cm and V/A = 0.038 cm. These data also clearly show the influence of CO2-conversion on the dissolution rates. In all experiments inhibition of dissolution occurs close to equilibrium. Therefore, the theoretical predictions are valid for concentrations c less than or equal to 0.9 c(eq). Summarising we find good agreement between experimental and theoretically predicted dissolution rates. Therefore, the theoretical model can be used with confidence to find reliable dissolution rates from the chemical composition of a solution for a wide field of geological applications

Principles of early development of karst conduits under natural and man-made conditions revealed by mathematical analysis of numerical models, 1996,
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Dreybrodt W,
Numerical models of the enlargement of primary fissures in limestone by calcite aggressive water show a complex behavior. If the lengths of the fractures are large and hydraulic heads are low, as is the case in nature, dissolution rates at the exit of the channel determine its development by causing a slow increase of water flow, which after a long gestation time by positive feedback accelerates dramatically within a short time span. Mathematical analysis of simplified approximations yields an analytical expression for the breakthrough time, when this happens, in excellent agreement with the results of a numerical model. This expression quantifies the geometrical, hydraulic, and chemical parameters determining such karat processes. If the lengths of the enlarging channels are small, but hydraulic heads are high, as is the case for artificial hydraulic structures such as darns, it is the widening at the entrance of the flow path which determines the enlargement of the conduit. Within the lifetime of the dam this can cause serious water losses, This can also be explained by mathematical analysis of simplified approximations which yield an analytical threshold condition from which the safety of a dam can be judged. Thus in both cases the dynamic processes of karstification are revealed to gain a deeper understanding of the early development of karst systems. As a further important result, one finds that minimum conditions, below which karstification cannot develop, do not exist

Dedolomitization as a driving mechanism for karst generation in Permian Blaine formation, southwestern Oklahoma, USA, 1997,
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Raines M. A. , Dewers T. A. ,
Cyclic deposits of Permian shales, dolomites, and halite and gypsum-bearing strata in the Blaine Formation of Southwestern Oklahoma contain abundant karst features. The present study shows that an important mechanism of karst development in these sequences is dedolomitization, wherein gypsum and dolomite in close spatial proximity dissolve and supersaturate groundwaters with respect to calcite. The net loss of mass accompanying this process (dolomite and gypsum dissolution minus calcite precipitation) can be manifest in secondary porosity development while the coupled nature of this set of reactions results in the retention of undersaturated conditions of groundwater with respect to gypsum. The continued disequilibrium generates karst voids in gypsum-bearing aquifers, a mineral-water system that would otherwise rapidly equilibrate. Geochemical modeling (using the code PHRQPITZ, Plummer et al 1988) of groundwater chemical data from Southwestern Oklahoma from the 1950's up to the present suggests that dedolomitization has occurred throughout this time period in evaporite sequences in Southwestern Oklahoma. Reports from groundwater well logs in the region of vein calcite suggest secondary precipitation, an observation in accord with dedolomite formation In terms of the amounts of void space produced by dissolution, dedolomitization can dominate gypsum dissolution alone, especially in periods of quiescent aquifer recharge when gypsum-water systems would have otherwise equilibrated and karst development ceased. Mass balance modeling plus molar volume considerations show that for every cubic cm of original rock (dolomite plus gypsum), there is 0.54 cm(3) of calcite and 0.47 cm(3) of void space produced Only slightly more pore space results if the dedolomitization reaction proceeds by psuedomorphic replacement of dolomite by calcite than in a reaction mechanism based on conservation of bicarbonate

Experimental studies of halite dissolution kinetics, 1. The effect of saturation state and the presence of trace metals, 1997,
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Alkattan M. , Oelkers E. H. , Dandurand J. L. , Schott

Mixed transport reaction control of gypsum dissolution kinetics in aqueous solutions and initiation of gypsum karst, 1997,
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Raines M. A. , Dewers T. A. ,
Experiments with gypsum in aqueous solutions at 25 degrees C, low ionic strengths, and a range of saturation states indicate a mixed surface reaction and diffusional transport control of gypsum dissolution kinetics. Dissolution rates were determined in a mixed flow/rotating disc reactor operating under steady-state conditions, in which polished gypsum discs were rotated at constant speed and reactant solutions were continuously fed into the reactor. Rates increase with velocity of spin under laminar conditions (low rates of spin), but increase asymptotically to a constant rate as turbulent conditions develop with increasing spin velocity, experiencing a small jump in magnitude across the laminar-turbulent transition. A Linear dependence of rates on the square root of spin velocity in the laminar regime is consistent with rates being limited by transport through a hydrodynamic boundary layer. The increase in rate with onset of turbulence accompanies a near discontinuous drop in hydrodynamic boundary layer thickness across the transition. A relative independence of rates on spinning velocity in the turbulent regime plus a nonlinear dependence of rates on saturation state are factors consistent with surface reaction control. Together these behaviors implicate a 'mixed' transport and reaction control of gypsum dissolution kinetics. A rate law which combines both kinetic mechanisms and can reproduce experimental results under laminar flow conditions is proposed as follows: R = k(t) {1 - Omega(b)() zeta [1 - (1 2(1 - Omega(b)())(1/2)]} where k(t) is the rate coefficient for transport control, and Omega(b)() is the mean ionic saturation state of the bulk fluid. The dimensionless parameter zeta(=Dm(eq)()/2 delta k() where m(eq)() = mean ionic molal equilibrium concentration, D is the diffusion coefficient through the hydrodynamic boundary layer, delta equals the boundary layer thickness and k() is the rate constant for surface reaction control) indicates which process, transport or surface reaction, dominates, and is sensitive to the hydrodynamic conditions in the reactor. For the range of conditions used in our experiments, zeta varies from about 1.4 to 4.5. Rates of gypsum dissolution were also determined in situ in a cavern system in the Permian Blaine Formation, southwestern Oklahoma. Although the flow conditions in the caverns were not determinable, there is good agreement between lab- and field-determined rates in that field rate magnitudes lie within a range of rates determined experimentally under zero to low spin velocities A numerical model coupling fluid flow and gypsum reaction in an idealized circular conduit is used to estimate the distance which undersaturated solutions will travel into small incipient conduits before saturation is achieved. Simulations of conduit wall dissolution showed-member behaviors of conduit formation and surface denudation that depend on flow boundary conditions (constant discharge or constant hydraulic gradient and initial conduit radius. Surface-control of dissolution rates. which becomes more influential with higher fluid flow velocity, has the effect that rate decrease more slowly as saturation is approached than otherwise would occur if rates were controlled by transport alone. This has the effect that reactive solutions can penetrate much farther into gypsum-bearing karst conduits than heretofore thought possible, influencing timing and mechanism of karst development as well as stability of engineered structures above karst terrain

Thermodinamic equilibrium, kinetics, activation barriers, and reaction mechanisms for chemical reactions in karst terrains., 1997,
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White W.

Thermodynamic equilibrium, kinetics, activation barriers, and reaction mechanisms for chemical reactions in Karst Terrains, 1997,
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White W. B. ,
Chemical reactions pertinent to karst systems divide broadly into (a) speciation reactions within aqueous solutions, (b) dissolution/precipitation and other acid/base reactions between aqueous solutions and solid minerals, and (c) redox reactions involving various carbon and sulfur-bearing species. As a backdrop against which other chemistry can be evaluated, selected phase diagrams and equilibrium speciation diagrams were calculated for the system Ca--Mg--O--H--C--S. The kinetics of reactions within this system span time scales from milliseconds for homogeneous reactions in solution through hundreds of hours for carbonate mineral dissolution reactions, to geologic time scales for reactions such as the aragonite/calcite inversion or the oxidation/reduction of native sulfur. In purely inorganic systems, kinetic barriers, typically on the order of tens of kJ/mole, are set by nucleation processes and by activated complex formation. Biological processes impact the purely inorganic chemistry by the following mechanisms: (a) Secretions and waste products from biological activity or consumption of CO2 by organisms changes the chemistry in the microenvironments of reaction surfaces. Oxidation potentials, pH, and ion activities may be modified, thus shifting equilibria. (b) Reaction rates may be increased due to modification of activated complexes and thus the activation barriers to reaction. (c) Organic compounds or microorganisms may act as substrates, thus lowering nucleation barriers. The preservation of microorganisms in cave deposits does not necessarily prove a cause and effect relationship

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