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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 bathyphreatic is referring to water moving with some speed through downward looping passages in the phreatic zone [25]. see bathyphreatic zone, ground water, phreas.?

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 mass-balance (Keyword) returned 23 results for the whole karstbase:
Showing 1 to 15 of 23
Karstification without carbonic acid; bedrock dissolution by gypsum-driven dedolomitization, 1994, Bischoff Jl, Julia R, Shanks Wc, Rosenbauer Rj,
Aggressive karstification can take place where dolomite and gypsum are in contact with the same aquifer. Gypsum dissolution drives the precipitation of calcite, thus consuming carbonate ions released by dolomite. Lake Banyoles, in northeastern Spain, is a karst lake supplied by sublacustrine springs, and karstic collapse is occurring in the immediate vicinity of the lake. Lake water is dominated by Mg-Ca and SO 4 -HCO 3 , and is supersaturated with calcite that is actively accumulating in lake sediments. Water chemistry, sulfur isotope composition, local stratigraphy, and mass-balance modeling suggest that the primary karst-forming process at Lake Banyoles is dedolomitization of basement rocks driven by gypsum dissolution. Karstification takes place along the subsurface contact between the gypsiferous Beuda Formation and the dolomitic Perafita Formation. This process is here recognized for the first time to cause karstification on a large scale; this is significant because it proceeds without the addition of soil-generated carbonic acid. Gypsum-driven dedolomitization may be responsible for other karstic systems heretofore attributed to soil-generated carbonic acid

Aggressive karstification can take place where dolomite and gypsum are in contact with the same aquifer. Gypsum dissolution drives the precipitation of calcite, thus consuming carbonate ions released by dolomite. Lake Banyoles, in northeastern Spain, is a karst lake supplied by sublacustrine springs, and karstic collapse is occurring in the immediate vicinity of the lake. Lake water is dominated by Mg-Ca and SO4-HCO3, and is supersaturated with calcite that is actively accumulating in lake sediments. Water chemistry, sulfur isotope composition, local stratigrapy, and mass-balance modeling suggest that the primary karst-forming process at Lake Banyoles is dedolomitization of basement rocks driven by gypsum dissolution. Karstification takes place along the subsurface contact between the gypsiferous Beuda Formation and the dolomitic Perafita Formation. This process is here recognized for the first time to cause karstification on a large scale; this is significant because it proceeds without the addition of soil-generated carbonic acid. Gypsum-driven dedolomitization may be responsible for other karstic systems heretofore attributed to soil-generated carbonic acid

Rock salt is approximately 1000 times more soluble than limestone and thus displays high rates of geomorphic evolution. Cave stream channel profiles and downcutting rates were studied in the Mount Sedom salt diapir, Dead Sea rift valley, Israel. Although the area is very arid (mean annual rainfall approximate to 50 mm), the diapir contains extensive karst systems of Holocene age. In the standard cave profile a vertical shaft at the upstream end diverts water from a surface channel in anhydrite or elastic cap rocks into the subsurface route in the salt. Mass balance calculations in a sample cave passage yielded downcutting rates of 0.2 mm s(-1) during peak flood conditions, or about eight orders of magnitude higher than reported rates in any limestone cave streams. However, in the arid climate of Mount Sedom floods have a low recurrence interval with the consequence that long-term mean downcutting rates are lower: an average rate of 8.8 mm a(-1) was measured for the period 1986-1991 in the same sample passage. Quite independently, long-term mean rates of 6.2 mm a(-1) are deduced from C-14 ages of driftwood found in upper levels of 12 cave passages. These are at least three orders of magnitude higher than rates established for limestone caves. Salt cave passages develop in two main stages: (1) an early stage characterized by high downcutting rates into the rock salt bed, and steep passage gradients; (2) a mature stage characterized by lower downcutting rates, with establishment of a subhorizontal stream bed armoured with alluvial detritus. In this mature stage downcutting rates are controlled by the uplift rate of the Mount Sedom diapir and changes of the level of the Dead Sea. Passages may also aggrade. These fast-developing salt stream channels may serve as full-scale models for slower developing systems such as limestone canyons

The combined use of Sr-87/Sr-86 and carbon and water isotopes to study the hydrochemical interaction between groundwater and lakewater in mantled karst, 1996, Katz B. G. , Bullen T. D. ,
The hydrochemical interaction between groundwater and lakewater influences the composition of water that percolates downward from the surficial aquifer system through the underlying intermediate confining unit and recharges the Upper Floridan aquifer along highlands in Florida. The Sr-87/Sr-86 ratio along with the stable isotopes, D, O-18, and C-13 were used as tracers to study the interaction between groundwater, lakewater, and aquifer minerals near Lake Barco, a seepage lake in the mantled karst terrane of northern Florida. Upgradient from the lake, the Sr-87/Sr-86 ratio of groundwater decreases with depth (mean values of 0.71004, 0.70890, and 0.70852 for water from the surficial aquifer system, intermediate confining unit, and Upper Floridan aquifer, respectively), resulting from the interaction of dilute oxygenated recharge water with aquifer minerals that are less radiogenic with depth. The concentrations of Sr2 generally increase with depth, and higher concentrations of Sr2 in water from the Upper Floridan aquifer (20-35 mu g/L), relative to water from the surficial aquifer system and the intermediate confining unit, result from the dissolution of Sr-bearing calcite and dolomite in the Eocene limestone. Dissolution of calcite [delta(13)C = -1.6 permil (parts per thousand)] is also indicated by an enriched delta(13)C(DIC) (-8.8 to -11.4 parts per thousand) in water from the Upper Floridan aquifer, relative to the overlying hydrogeologic units (delta(13)C(DIC) < -16 parts per thousand). Groundwater downgradient from Lake Barco was enriched in O-18 and D relative to groundwater upgradient from the lake, indicating mixing of lakewater leakage and groundwater. Downgradient from the lake, the Sr-87/Sr-86 ratio of groundwater and aquifer material become less radiogenic and the Sr2 concentrations generally increase with depth. However, Sr2 concentrations are substantially less than in upgradient groundwaters at similar depths. The lower Sr2 concentrations result from the influence of anoxic lakewater leakage on the mobility of Sr2 from clays. Based on results from mass-balance modeling, it is probable that cation exchange plays the dominant role in controlling the Sr-87/Sr-86 ratio of groundwater, both upgradient and downgradient from Lake Barco. Even though groundwater from the three distinct hydrogeologic units displays considerable variability in Sr concentration and isotopic composition, the dominant processes associated with the mixing of lakewater leakage with groundwater, as well as the effects of mineral-water interaction, can be ascertained by integrating the use of stable and radiogenic isotopic measurements of groundwater, lakewater, and aquifer minerals

Dedolomitization as a driving mechanism for karst generation in Permian Blaine formation, southwestern Oklahoma, USA, 1997, 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

Geochemical evolution of a karst stream in Devils Icebox Cave, Missouri, USA, 1997, Wicks Carol M. , Engeln Joseph F. ,
A 3.7 km flowpath along the main stream channel in Devils Icebox Cave, Boone County, Missouri, was sampled on 23 January, 23 March and 18 September 1994. In January 1994, the water was oversaturated with respect to both calcite and dolomite, and only minor compositional changes were observed along the flowpath. In March 1994, the water was oversaturated with respect to calcite but undersaturated with respect to dolomite. Using a mass-balance approach, the composition of the stream water at downstream locations was predicted by dissolution of dolomite (a maximum of 0.16 mmol s-1) and by a minor amount of calcite precipitation (a maximum of 0.03 mmol s-1). In September 1994, there were increases in the Mg, Ca, and total inorganic carbon (TIC) mass fluxes that were due to the dissolution of dolomite (SIdolomiteSI is saturation index) and calcite (SIcalcite2 of the water should decrease downstream; however, we found an increase in the partial pressure of CO2 along the stream. The source of this additional CO2 is thought to be microbial degradation of bat guano. The decomposition of bat guano appeared to change the composition of the stream water during the period the bats are in the cave, and this change was reflected in the composition of the stream water collected in September 1994. Based on the length of the flowpath and on the average velocity of the water along the flowpath, the travel time of water in this karst stream is less than 4 days. The reactions that control the chemistry of the karst water must be those with equally short characteristic times: the dissolution of dolomite and calcite, CO2 exchange, and microbial degradation of organic matter

Estimating subsurface fissure apertures in karst aquifers from equilibrium activities, 1998, Field Ms, Mose Dg,
Rn-222 activities were determined for the karst aquifer underlying Walkersville, Maryland, in an area of ground-water discharge from a single geological unit during the summer and fall seasons, Radon-222 equilibrium activities in karst ground waters can be employed in mass-balance models to estimate microfissure, macrofissure, and conduit aperture dimensions, This approach defines Rn-222 generation and loss in karst aquifers as a function of fissure apertures and the U-238 content of the rock, High Rn-222 activities occur in tight fissures and low Rn-222 activities occur in conduits, In the vadose zone, Rn-222 activities are low as a result of degassing, especially if flow is turbulent and activities are decoupled from the phreatic zone, In the phreatic zone, if recharge to fissures causes a reduction of residence time below that required for equilibrium (approximate to 26 days), Rn-222 activities fall, At springs and in the vadose zone, after a rainfall event, Rn-222 activities increase as waters with long residence and with high Rn-222 activities are expelled from fissure and fracture storage, Field data and selected literature values were used to test the model, Models used to predict median microfissure apertures for this karst aquifer yield aperture estimates ranging from 2.8 mu m to 9.2 mu m. Median macrofissure apertures ranged from 5.53 cm to 5.88 cm, Median conduit apertures ranged from 1.16 m to 1.24 m, Comparison of the models results with published data on karst aquifers and observations at the field site suggest that the predicted apertures are reasonable

Changes in the isotopic and chemical composition of ground water resulting from a recharge pulse from a sinking stream, 1998, Katz B. G. , Catches J. S. , Bullen T. D. , Michel R. L. ,
The Little River, an ephemeral stream that drains a watershed of approximately ss km(2) in northern Florida, disappears into a series of sinkholes along the Cody Scarp and flows directly into the carbonate Upper Floridan aquifer, the source of water supply in northern Florida. The changes in the geochemistry of ground water caused by a major recharge pulse from the sinking stream were investigated using chemical and isotopic tracers and mass-balance modeling techniques, Nine monitoring wells were installed open to the uppermost part of the aquifer in areas near the sinks where numerous subterranean karst solution features were identified using ground penetrating radar. During high-flow conditions in the Little River, the chemistry of water in some of the monitoring wells changed, reflecting the mixing of river water with ground water. Rapid recharge of river water into some parts of the aquifer during high-flow conditions was indicated by enriched values of delta O-18 and delta deuterium (-1.67 to -3.17 per mil and -9.2 to -15.6 per mil, respectively), elevated concentrations of tannic acid, higher (more radiogenic) Sr-87/Sr-86 ratios, and lower concentrations of Rn-222, silica, and alkalinity compared to low-how conditions. The proportion of river water that mixed with ground water ranged from 0.10 to 0.67 based on binary mixing models using the tracers O-18, deuterium, tannic acid, silica, Rn-222, and Sr-87/Sr-86. On the basis of mass-balance modeling during steady-state how conditions, the dominant processes controlling carbon cycling in ground water are the dissolution of calcite and dolomite in aquifer material, and aerobic degradation of organic matter. (C) 1998 Elsevier Science B.V. All rights reserved

Geochemical modeling of groundwater in karst area and its application at Pingdingshan coalfield, 1998, Wang G. C. , Tao S. , Shen Z. L. , Zhong Z. X. ,
Several approaches including hydrogeochemistry and isotope hydrogeology have been used to investigate the karst groundwater systems at Pingdingshan coalfield in recent years. The results of the modeling and evaluation of groundwater chemistry, as parts of recent research progress at the area, are presented. The characteristics of Cambrian karst groundwater flow was analyzed in terms of tritium distribution of groundwater based on the fact that the Guodishan fault, the largest one within the coalfield, is divided into permeable (southern and northern) and impermeable (middle) sections. The evolution of groundwater chemistry, the suitability of geothermometers and the feature of karst development were deduced and discussed using the speciation modeling and mass balance approach

Hydrochemical evidence for mixing of river water and groundwater during high-flow conditions, lower Suwannee River basin, Florida, USA, 1999, Crandall Ca, Katz Bg, Hirten Jj,
Karstic aquifers are highly susceptible to rapid infiltration of river water, particularly during periods of high flow. Following a period of sustained rainfall in the Suwannee River basin, Florida, USA, the stage of the Suwannee River rose from 3.0 to 5.88 m above mean sea level in April 1996 and discharge peaked at 360 m(3)/s. During these high-now conditions, water from the Suwannee River migrated directly into the karstic Upper Floridan aquifer, the main source of water supply for the area. Changes in the chemical composition of groundwater were quantified using naturally occurring geochemical tracers and mass-balance modeling techniques. Mixing of river water with groundwater was indicated by a decrease in the concentrations of calcium, silica, and Rn-222; and by an increase in dissolved organic carbon (DOC), tannic acid, and chloride, compared to low-flow conditions in water from a nearby monitoring well, Wingate Sink, and Little River Springs. The proportion (fraction) of river water in groundwater ranged from 0.13 to 0.65 at Wingate Sink and from 0.5 to 0.99 at well W-17258, based on binary mixing models using various tracers. The effectiveness of a natural tracer in quantifying mixing of river water and groundwater was related to differences in tracer concentration of the two end members and how conservatively the tracer reacted in the mixed water. Solutes with similar concentrations in the two end-member waters (Na, Mg, K, Cl, SO4, SiO2) were not as effective tracers for quantifying mixing of river water and groundwater as those with larger differences in end-member concentrations (Ca, tannic acid, DOC, Rn-222, HCO3)

The geochemistry of sulphur in a mixed allogenic-autogenic karst catchment, Castleton, Derbyshire, UK, 2000, Bottrell Sh, Webber N, Gunn J, Worthington Srh,
Analyses are presented of anion chemistry and sulphur isotopic compositions of sulphate in sinking streams and groundwaters in a mixed allogenic-autogenic karst catchment. Using the sulphur isotopic data, sources of sulphate from agriculture and the effects of sulphate reduction arising from slurry application can be distinguished from natural rock weathering sources. Within the aquifer, sulphate in known autogenic waters has isotopic compositions distinct from allogenic waters, the autogenic waters being dominated by sulphate from rainfall and rock weathering in these low agricultural intensity catchments. On this basis, water rising at low flow from Whirlpool Rising, Speedwell Cavern, has been identified as dominantly autogenic. Groundwater flow between the sinks and risings in Speedwell Cavern is believed to be along conduits following mineralized faults (rakes). During transit SO42-/Cl- in the water increases. Isotopic mass balance shows that this must be due to addition of sulphate from the oxidation of ore minerals by groundwater. Mass balance considerations show that the present rate of sulphide oxidation must be the result of enhancement by lead mining operations on the rakes. Copyright (C) 2000 John Wiley & Sons, Ltd

Estimating recharge in a tropical karst aquifer, 2000, Jones I. C. , Banner J. L. , Humphrey J. D. ,
Unique constraints on seasonal and spatial variations in recharge to the Pleistocene limestone aquifer of Barbados are obtained from the analysis of oxygen isotopic compositions of groundwater and rainwater. Conventional methods of estimating recharge are based on groundwater chloride variations, coastal groundwater discharge, and potential evapotranspiration. These methods typically yield estimates of recharge for Barbados that range from 9% to 20% of average annual rainfall, with significant uncertainties that arise from poorly constrained model input parameters. Owing to the low relief and tropical climate of Barbados, variations in rainwater and groundwater delta(18)O values are primarily influenced by the amount of rainfall, with negligible temperature or altitude effects. Composite monthly rainwater delta(18)O values are inversely related to rainfall, while groundwater delta(18)O values show little seasonal variability. Rainwater delta(18)O values are equivalent to groundwater values only at the peak of the wet season. By using mass balance, the difference between groundwater and weighted-mean rainwater delta(18)O values gives recharge values. These values are in general agreement with estimates by conventional methods (10-20%) and provide unique additional information including the following: (1) Recharge is restricted to the wettest 1-3 months of the year, and (2) there is less recharge at higher elevations. The effective shift in delta(18)O values between contemporaneous rainwater and groundwater via recharge is a useful tool for estimating temporal and spatial variability in recharge and must be considered in paleoclimatic studies where climate inferences are based on groundwater delta(18)O values preserved in the geologic record

Seasonal variations in Sr, Mg and P in modern speleothems (Grotta di Ernesto, Italy), 2001, Huang Yiming, Fairchild Ian J. , Borsato Andrea, Frisia Silvia, Cassidy Nigel J. , Mcdermott Frank, Hawkesworth Chris J. ,
Sub-annual variations in trace element chemistry and luminescence have recently been demonstrated from speleothems and offer the potential of high-resolution palaeoclimatic proxies. However, no studies have yet examined microscopic trace element variations in relation to modern cave conditions. In this study, the spatial variations in trace element (Sr, Mg and P) concentrations in speleothems (a stalagmite and a soda straw stalactite) from the alpine Ernesto cave (temperature 6.60.1[deg]C) in a forested catchment in NE Italy have been studied using secondary ion mass spectrometry (SIMS) and compared with environmental parameters and waters in the modern cave. An annual lamination exists in the stalagmite and soda straw stalactite in the form of clear calcite with narrow visible layers, which are UV-fluorescent and interpreted to contain soil-derived humic/fulvic acids washed into the cave during autumn rains. Microanalyses were undertaken of seven annual laminae, probably deposited during the 1960s in the stalagmite, and seven laminae in the 1990s for the stalactite.The analysis results show that Sr consistently has a trough and P, a peak centred on the inclusion-rich layer. Mg shows mainly a negative covariation with Sr in laminae formed in the 1990s, but a positive covariation in the stalagmite formed in 1960s. The spatial scale of the main geochemical variations is the same as that of annual laminae of inclusion-poor and inclusion-rich couplets. Mass balance arguments are used to show that the P is inorganic in form and presumably occurs as individual phosphate ions within the calcite.Most drip waters show limited chemical variations, but a summer peak in trace elements in 1995 and a decrease in Mg/Ca in the following winter are notable. More pronounced covariations in Mg/Ca and Sr/Ca are shown by a site with highly variable drip rates where ratios increase at slow drip rates. The strongest seasonal variations are found in pool waters, where ratios increase reflecting significant Ca removal from the water into the calcite during the winter in response to seasonal PCO2 variations in cave air. Thus, the cave waters' compositions tend to reflect climate conditions, such that Mg/Ca and Sr/Ca are tentatively interpreted to be higher when climate conditions are dry.Combining results from the speleothems and cave water along with the behaviour of each trace species, Mg/Ca variations in the speleothems are considered to reflect their variation in the cave waters, whereas, Sr incorporation is also dependent on precipitation rate, in this case, mainly controlled by temporal variations in PCO2 in the cave (and conceivably, also by inhibitors such as phosphate). P adsorption (a fraction of which is subsequently incorporated within calcite) depends on aqueous phosphate concentration and water flux, both of which should increase during the autumn. Therefore, multiple trace element profiles in speleothems reflect multiple aspects of environment seasonality and conditions, and hence, a calibration against weather records is desirable to establish their palaeoclimatological meaning. The strong annual variation of trace elements, and particularly P, can provide chronological markers for high-resolution studies of other climate proxies, such as stable isotopes

Nutrient processing capacity of a constructed wetland in western Ireland, 2002, Healy M. , Cawley A. M. ,
In Ireland, constructed wetland systems are increasingly being used to perform tertiary treatment on municipal waste effluent from small towns and villages located in areas whose receiving waters are deemed sensitive. The bedrock formation in the west of Ireland is primarily karst limestone and where the overburden-soil cover is very shallow, such waters are highly sensitive to pollution sources, as little or no natural attenuation and/or treatment will occur. Constructed wetland technology has been seen to offer a relatively low-cost alternative to the more conventional tertiary treatment technologies, particularly when dealing with low population numbers in small rural communities. This paper examines the waste treatment performance, in terms of nutrient (P and N) reduction, of a recently constructed surface-flow wetland system at Williamstown, County Galway, Ireland. Performance evaluation is based on more than two years of water quality and hydrological monitoring data. The N and P mass balances for the wetland indicate that the average percentage reduction over the two-year study period is 51% for total N and 13% for total P. The primary treatment process in the wetland system for suspended solids (between 84 and 90% reduction), biological oxygen demand (BOD) (on average, 49% reduction), N, and P is the physical settlement of the particulates. However, the formation of algal bloom during the growing season reduces the efficiency of the total P removal

Geochemistry of red residua underlying dolomites in karst terrains of Yunnan-Guizhou Plateau II. The mobility of rare earth elements during weathering, 2004, Ji H. B. , Wang S. J. , Ouyang Z. Y. , Zhang S. , Sun C. X. , Liu X. M. , Zhou D. Q. ,
The aim of this study is to characterize the evolution of the rare earth elements (REE) in the Pingba red residua on karst terrain of Yunnan-Guizhou Plateau. The in-situ weathering and the two-stage development of the profile had been inferred from REE criterions. The REE were significantly fractionated, and Ce was less mobilized and separated from the other REEs at the highly enriched top of the profile. This is consistent with the increase of oxidation degree in the regolith. And it is also suggested that the wet/dry climate change during chemical weathering caused Ce alternative change between enrichment and invariance in the upper regolith. Chondrite-normalized REE distribution patterns for samples from dolomites and the lower regolith are characteristic of MREE enrichment and remarkable negative Ce-anomalies patterns (similar to the convex-up REE patterns). The following processes are interpreted for the patterns in this study: (1) the accumulation of MRRE-rich minerals in dolomite dissolution, (2) water-rock interaction in the weathering front, and (3) more leaching MREE from the upper part of the profile. The latter two explanations are considered as the dominant process for the formation of the REE patterns. Samples from the soil horizon exhibit typical REE distribution patterns of the upper crust, i.e., La-N/Yb-N = 10 and Eu/Eu* = 0.65. All data indicate that the leaching process is very important for pedogenesis in this region. The experiments demonstrating that abnormal enrichment of REE at the upper regolith-bedrock interface is caused by a combination of volume change, accumulation of REE-bearing minerals, leaching of REE from the upper regolith, and water-rock interaction during rock-soil alteration processes. Our results support the conclusion that the weathering profile represents a large, continental elemental storage reservoir, whereas REE enrichment occurs under favorable conditions in terms of stable tectonics, low erosion and rapid weathering over sufficiently long time. (C) 2003 Elsevier B.V. All rights reserved

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