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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 capacity, well is the rate at which a well will yield water [16].?

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

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KarstBase a bibliography database in karst and cave science.

Featured articles from Cave & Karst Science Journals
Chemistry and Karst, White, William B.
See all featured articles
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 nitrogen (Keyword) returned 47 results for the whole karstbase:
Showing 1 to 15 of 47
The role of groundwater in eutropication of a lake in glacial outwash terrain., 1976,
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Lee David Robert
The nutrient contribution of groundwater in glacial outwash terrain was evaluated at Lake Sallie in north-central U.S.A. (4646' N., 95 54' W.). Groundwater entering the lake was collected with seepage meters consisting of bottomless cylinders vented to a thin membrane bag. A theoretical flow net and comparison of nutrient concentrations in well and seepage water indicated that seepage meters can be used in high velocity discharge areas to obtain site-specific water samples of groundwater for nutrient analyses. Based on an average value of 0.25 mg/l PO4, groundwater inflow along an 800 km segment of shoreline transported 37 kg of phosphorus per year into the lake. Groundwater inflow was nitrate rich along shoreline adjacent so land used for agriculture and lakeside septic tanks, but there was no apparent pattern regarding land use and phosphorus content of groundwater inflow. A nearby eutrophic lake was a suspected source of phosphorus in groundwater inflow. Because surface flow has carried large quantities of nitrogen and phosphorus into this lake, its present eutrophic condition cannot be attributed to nutrient influx by groundwater. However, groundwater nutrient influx could be highly significant in other lakes where surface nutrient influx is small.

Microflora and activity of functional groups in the sediments of three caves of Central Italy., 1978,
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Fumanti B. , Pasqualini A. , Vison L.
A comparative study is presented of the microflora of sediments in three caves with different trophic characteristics. Quantitative and qualitative variations of microflora were investigated for one year by studying the total microflora and the activity of the nitrogen cycle functional groups. Data were compared with those of other works of previous authors. Results show that the quantity and kind of organic matter of sediment are most important factors regulating the abundance and activity of cavernicolous microflora. The experimental part of this paper is prefaced by a digest of investigations previously carried out on cavernicolous microflora and by a report of topographic, geomorphologic, hydrologic and trophic characteristics of the caves examined.

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Pysek P. ,
In the second part of the study on vegetation of village settlements at the territory of the Bohemian Karst, ecological and successional characteristics of communities are given. Ellenberg indicator values for temperature, moisture, nitrogen and soil reaction were used to investigate habitat conditions. Successional relations of communities are presented. Quantitative data on the composition of vegetation cover were obtained which made it possible to compare the study area with other regions

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Eichem Ac, Dodds Wk, Tate Cm, Edler C,
Dry Chinquapin oak (Quercus macrocarpa) and American elm (Ulmus americana) leaves were placed in four microcosms fed by groundwater springs to monitor changes in dry mass, ash-free dry mass, and microbial activity over a 35-day period. Oxygen microelectrodes were used to measure microbial activity and to estimate millimeter-scale heterogeneity in that activity. Oak leaves lost mass more slowly than elm leaves. Generally, there was a decrease in total dry weight over the first 14 days, after which total dry weight began to increase. However, there were consistent decreases in ash-free dry mass over the entire incubation period, suggesting that the material remaining after initial leaf decomposition trapped inorganic particles. Microbial activity was higher on elm leaves than on oak leaves, with peak activity occurring at 6 and 27 days, respectively. The level of oxygen saturation on the bottom surface of an elm leaf ranged between 0 and 75% within a 30-mm2 area. This spatial heterogeneity in O2 saturation disappeared when the water velocity increased from 0 to 6 cm s-1. Our results suggest that as leaves enter the groundwater, they decompose and provide substrate for microorganisms. The rate of decomposition depends on leaf type, small-scale variations in microbial activity, water velocity, and the length of submersion time. During the initial stages of decomposition, anoxic microzones are formed that could potentially be important to the biogeochemistry of the otherwise oxic aquifer

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Jabro J. D. , Lotse E. G. , Fritton D. D. , Baker D. E. ,
Leaching of agricultural chemicals from the root and vadose zones into groundwater is an important environmental concern. To procure a better understanding of the movement and transport of agricultural chemicals through the soil profile, a field research study was conducted to estimate bromide leaching losses under saturated conditions where preferential flow is occurring. The field data were then used to evaluate the LEACHM model. Eighteen double-ring infiltrometers were used to apply a pulse (100 mm depth) of bromide tracer on two previously saturated soils located in a karst region of southeastern Pennsylvania. Internal drainage over the next seven days resulted in nearly 51 % of the applied Br- being leached to a depth below 0.80 m. The LEACHM model was used to simulate the amount of bromide leached in each infiltrometer. The model predicted, accurately, an average of 46% of the applied Br- leached below the 0.80 m depth. Mcan values of bromide concentration in the soil profile were predicted within two standard deviations of the measured mean for all depths except for the 0.20-0.40 m depth increment where the model overpredicted the bromide concentration. The model predictions of Br- leached were tested against field measurements using several statistical tests. The LEACHM model performed adequately under preferential flow conditions, perhaps because the infiltration rate at each site was used as a model input. This, actually, is some measure of the macropore flow process and suggests that simple models such as LEACHM can be used in the field, as long as a distribution of infiltration rates is used as an input

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Iqbal M. Z. , Krothe N. C. ,
A hydrogeological study was conducted, during the 1991-1992 water year, in the clay-soil mantled portion of a limestone terrain in southern Indiana. The purpose of the study was to investigate the modes of soil-water infiltration contributing to rapid transport of nitrate to the saturated zone. The I-year-cycle profiles of nitrate concentration vs. time show a consistent increase of nitrate at various depths in the unsaturated zone during the period of investigation. The increase of nitrate in soil water is attributed to the rapid flushing of the inorganic fertilizers from the fields after the area received sufficient rainfall in late fall. The investigation also showed a major movement of nitrate in quick pulses through the unsaturated zone, rather than a slow uniform recharge, immediately after a major storm event. The asymmetric profiles of nitrate concentration vs. depth point to the existence of preferential flow through macropores in the clay-soil mantle above the bedrock. Soil-water transport between storm events is by matrix type flow. Nitrogen isotopes were analyzed for representative groundwater samples collected before and immediately after fertilization of fields in the summer, 1991. The delta(15)N values of the samples did not show any major shift in nitrate sources between the sampling periods. The summer of 1991 was extremely dry prohibiting vertical transport of nitrate from the fields to the groundwater system. Any change in nitrate concentration in groundwater during this time is attributed to the mixing through lateral flow within the aquifer

Agricultural land use effects on nitrate concentrations in a mature karst aquifer, 1996,
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Boyer Dg, Pasquarell Gc,
The impact on water quality by agricultural activity in karst terrain is an important consideration for resource management within the Appalachian Region. Karst areas comprise about 18 percent of the Region's land area. An estimated one-third of the Region's farms, cattle, and agricultural market value are on karst terrain. Nitrate concentrations were measured in cave streams draining two primary land management areas. The first area was pasture serving a beef cow-calf operation. The second area was a dairy. Nitrate-N concentrations were highest in cave streams draining the daily and a cave stream draining an area of pasture where cattle congregate for shade and water. The dairy contributed about 60 to 70 percent of the nitrogen load increase in the study section of the cave system. It was concluded that agriculture was significantly affecting nitrate concentrations in the karst aquifer. Best management practices may be one way to protect the ground water resource

Stable Isotope Analysis of Human Remains: A Tool for Cave Archaeology, 1997,
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Trimble, C. C. , Macko, S. A.
Stable isotope analysis of human remains is a research tool that can provide paleodiet information for archaeological sites, such as caves, where traditional evidence may be missing or out of context. Unlike other lines of evidence, the stable isotopes of carbon and nitrogen in human bone reflect the chemistry of the diet and therefore provide a direct measure of the foods consumed. As an example, the data from isotopic analyses of bone from the Mer site (44LE280), a cave in Lee County, Virginia, are presented. Although this site lacks faunal and floral remains to provide basic information about the availability and potential utilization of food resources, the stable isotope data from other sites throughout Virginia and North Carolina provide a basis for comparison. The d13C and d15N values for the cave burials suggest a diet composed of primarily C4 plant proteins and some terrestrial animal proteins.

The nutritional status of healthy and declining stands of Banksia integrifolia on the Yanakie Isthmus, Victoria, 1997,
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Bennett Lt, Attiwill Pm,
Banksia integrifolia L.f. has been in decline an calcareous sands of the Yanakie Isthmus, southern Victoria, since early 1980. Early studies indicated that the decline is associated with a particular soil condition possibly a nutritional imbalance involving Fe. However, in foliage samples collected from the three main soil types of the Isthmus, declining trees had similar concentrations of Fe but lower concentrations of Ca than healthy trees. Comparisons were made of seasonal variation in concentrations of macro- and micro-nutrients in foliage and litterfall from healthy trees (to minimise secondary changes associated with decline) within healthy and declining sites on the same soil type. On average, litterfall and the nutrient content of litterfall was greatest within the canopy area of B. integrifolia of the healthy stand. Banksias of the healthy stand also had greater concentrations of N, P, K and Na in fully-expanded leaves, resorbed greater proportions of phloem-mobile nutrients from senescent leaves and accumulated more Ca in senescent leaves. However, there was no evidence of nutritional imbalance in healthy trees within declining stands. It is argued that the lower foliar Ca in declining trees on three soil types and lower nutritional status of healthy trees within declining stands were due to lower productivity and lower water use and were therefore a result or an indication of decline rather than a cause

delta N-15 of nitrate derived from explosive sources in a karst aquifer beneath the Ammunition Burning Ground, Crane Naval Surface Warfare Center, Indiana, USA, 1998,
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Dignazio Fj, Krothe Nc, Baedke Sj, Spalding Rf,
Military institutions involved in the production and demolition of explosives, propellants, and pyrotechnics have the potential to degrade groundwater aquifers through the addition of numerous contaminants including nitrate. A nitrate plume has been identified in a karst aquifer beneath the Ammunition Burning Ground (ABG) at the Crane Naval Surface Warfare Center, Indiana, USA. Wells located in the vicinity of surface impoundments and bum pans used for treatment of explosive materials show the highest concentrations of nitrate ranging from 11.2 to 19.6 mg l(-1) as NO3-. Little is known about the isotopic composition of nitrates originating from these processes. Eight wells within the ABG were sampled and analyzed for nitrogen isotopic composition of nitrate. An enrichment in the delta(15)N (delta(15)N = .9, .0, .1. and .5 parts per thousand) occurred at four wells located near the primary areas of disposal activities within the ABG. Four wells located near the outer limits of the ABG had delta(15)N values significantly lower than those observed in the central area of the ABG (delta(15)N = .0, .1, .6, and .0 parts per thousand). Soil samples and burn-pan ash samples were collected and analyzed for the nitrogen isotopic composition of nitrate. Three soil nitrate samples had low delta(15)N values of -1.7, -1.8. and .2 parts per thousand. The burn-pan ash sample produced nitrate with a delta(15)N value of .9 parts per thousand. The observed enrichment in delta(15)N from samples taken from wells located near the ABG has been postulated to be a result of photodegradation or biochemical modification of RDX and TNT contaminated sludges and volatilization of NH3 in storage lagoons within the ABG. (C) 1998 Elsevier Science B.V. All rights reserved

Oxidation of organic matter in a karstic hydrologic unit supplied through stream sinks (Loiret, France), 1998,
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Alberic P, Lepiller M,
The aim of this paper is to appraise the ability of the oxidation of riverine organic matter in the control of limestone dissolution, in a karst network. Biogeochemical processes during infiltration of river water into an alluvial aquifer have already been described for an average flow velocity of 4-5 m d(-1) (Jacobs, L. A., von Gunten, H. R., Keil, R, and Kuslys, M. (1988) Geochemical changes along a river-groundwater infiltration flow path: Glattfelden, Switzerland. Geochim. Cosmochim. Acta 52, 2693-2706; Von Gunten, H. R., Karametaxas, G., Krahenbuhl, U., Kuslys, M., Giovanoli R., Hoehn E. and Keil R. (1991) Seasonal biogeochemical cycles in riverborne groundwater. Geochim. Cosmochim. Acta 55, 3597-3609; Bourg, A. C. M. and Bertin, C. (1993) Quantitative appraisal of biogeochemical chemical processes during the infiltration of river water into an alluvial aquifer. Environ. Sci. Technol. 27, 661-666). Karstic drainage networks, such as in the River Loire-Val d'Orleans hydrologic system (Fig. 1), make possible flow velocities up to 200 m h(-1 a) and provide convenient access to different water samples several tens of km apart, at both extremities of the hydrologic unit (Chery, J.-L. (1983) Etude hydrochimique d'un aquifere karstique alimente par perte de cours d'eau (la Loire): Le systeme des calcaires de Beauce sous le val d'Orleans. These, Universite d'Orleans; Livrozet, E. (1984) Influence des apports de la Loire sur la qualite bacteriologique et chimique de l'aquifere karstique du val d'Orleans. These, Universite d'Orleans). Recharge of the karstic aquifer occurs principally from influent waters from stream sinks, either through coarse alluvial deposits or directly from outcrops of the regional limestone bedrock (Calcaires de Beauce). Recharge by seepage waters From the local catchment basin is small (Zunino, C., Bonnet, M. and Lelong, F. (1980) Le Val d'Orleans: un exemple d'aquifere a alimentation laterale. C. R. somm. Soc. Geol. Fr. 5, 195-199; Gonzalez R. (1992) Etude de l'organisation et evaluation des echanges entre la Loire moyenne et l'aquifere des calcaires de Beauce. These, Universite d'Orleans) and negligible in summer. This karstic hydrologic: system is the largest in France in terms of flow (tens to hundreds of m(3)/s) and provides the main water resource of the city of Orleans. Chemical compositions of influent waters (River Loire) and effluent waters (spring of the river Loiret) were compared, in particular during floods in summer 1992 and 1993 (Figs 2-4). Variation of chloride in the River Loire during the stream rise can be used as an environmental tracer of the underground flow (Fig. 2). Short transit times of about 3 days are detectable (Fig, 2) which are consistent with earlier estimations obtained with chemical tracers (Ref. in Chery, J.-L. (1983) These, Universite d'Orleans). Depending on the hydrological regime of the river, organic carbon discharge ranges between 3-7 and 2-13 mg/l for dissolved and particulate matter respectively (Fig. 3). Eutrophic characteristics and high algal biomasses are found in the River Loire during low water (Lair, N. and Sargos, D. (1993) A 10 year study at four sites of the middle course of the River Loire. I - Patterns of change in hydrological, physical and chemical variables in relation to algal biomass. Hudroecol. Appl. 5, 1-27) together with more organic carbon rich suspended particulate matter than during floods (30-40 C-org % dry weight versus 5-10%). Amounts of total organic carbon and dissolved oxygen (Fig. 3) dramatically decrease during the underground transport, whereas conversely, dissolved calcium, alkalinity and inorganic carbon increase (Fig. 4). Anoxia of outflows map start in April. Dissolution of calcium carbonates along the influent path outweighs closed system calcite equilibrium of inflow river waters (Table 3). The impact of organic matter oxidation on calcite dissolution may be traced by variations of alkalinity and total carbonates in water. Following, Jacobs, L. A., von Gunten, H. R., Keil, R. and Kuslys, M. (1988) Geochemical changes along a river-groundwater infiltration flow path: Glattfelden, Switzerland. Geochim. Cosmochim. Acta 52, 2693-2706), results are shown graphically (Fig. 5). Extent of reactions is controlled by the consumption of dissolved O-2 and nitrate for organic matter oxidation and by the release of Ca2 for calcite dissolution (Table 2). The karstic network is considered to behave like a biological reactor not exchanging with the atmosphere, with steady inhabitant microbial communities (Mariotti A., Landreau A, and Simon B. (1988) N-15 isotope biogeochemisrry and natural denitrification process in groundwater: Application to the chalk aquifer of northern France. Geochim. Cosmochim. Acta 52, 1869-1878; Gounot, A.-M. (1991) Ecologie microbienne des eaux ei des sediments souterrains. Hydrogeologie, 239-248). Thus, energy requirements only are considered, not carbon assimilation. Moreover, there is no necessity to invoke any delay for nitrification enhancement, as observed elsewhere, after waste water discharge into the river (Chesterikoff, A., Garban, B., Billen, G. and Poulin, M. (1992) Inorganic nitrogen dynamics in the River Seine downstream from Paris (France). Biogeochem. 17, 147-164). Main microbial processes are assumed to be aerobic respiration, nitrification and denitrification. Reactions with iron and manganese, real but not quantitatively important, were neglected. Sulphate reduction and methane formation, certainly not active, were not considered. Denitrification, which is suggested by low nitrate and ammonium concentrations and anoxia in the outflow, is known to be rapid enough to be achieved in a short time (Dupain, S. (1992) Denitrification biologique heterotrophe appliquee au traitement des eaux d'alimentation: Conditions de fonclionnement et mise au point d'un procede. These, Universite Claude Bernard, Lyon). Reaction are somewhat arbitrary but conform to general acceptance (Morel, M. M. and Hering, J. G. (1993) Principles and Applications of Aquatic Chemistry. Wiley, New York). Anaerobic ammonium oxidation (Mulder A., van de Graaf, A. A., Robertson, L: A. and Kuenen, J. G. (1995) Anaerobic ammonium oxidation discovered in a denitrifying fluidized bed reactor. FEMS Microbiol. Ecol. 16, 177-184). although possible, was not considered. In fact, C/N ratio of the reactive organic matter has only mild repercussions on the results; i.e. in the same range as the analytical errors for alkalinity and total carbonates. The objective was simply to roughly confront characteristics of outflowing waters and the calculation. Respective roles of aerobes and denitrifiers, for instance, are not certain. Several periods during low water or floods were selected with various ranges for calcium dissolution or nitrate and oxygen concentrations. The result is that in most cases simulation and data are in reasonable accordance (Fig. 5). Amounts of organic matter in River Loire are generally sufficient to sustain the process (Table 3. Particulate organic matter is probably the most reactive. The balance of oxidation of organic matter indicates that about 65 mu g C-org/l.h are oxidized during the transport without much variation with the river regime or organic discharge. It is concluded that limestone dissolution is directly dependent on organic matter oxidation, but variation occurs (7-29 mg CuCO3/l) with the level of bases that can be neutralized in the River Loire water. (C) 1998 Elsevier Science Ltd. All rights reserved

Effect of automobile emissions on the Jenolan Caves , 1998,
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James Julia M. , Antil Sarah J. , Cooper A. , Stone D. J. M.

Jenolan Caves are a major tourist attraction in NSW, Australia. One of the major features of the caves is a natural archway known as the Grand Arch, through which a road passes. Carbon dioxide (CO2), sulfur oxides (SOx), nitrogen oxides (NOx), volatile organic compounds (VOCs) and particulate matter were measured in an attempt to determine the associated risk to the caves. CO2 levels were above the average atmospheric concentration but below the limestone damage threshold of 2400 ppm. The SOx, NOx and VOCs concentrations were exceptionally low. Vehicle-produced particulate matter from the Grand Arch was found up to 100 m into the tourist caves but was prevented from further penetration by a barrier of moist cave air.

Research on the soils of karst areas in Hungary (example from Bükk Mountain), 1999,
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Zseni Anikó,

The author studied the characteristics of the soil nutrient system in a Hungarian karst area, that is on 8 km2 area of the Bükk plateau. The pH, total carbonate content, total soil-nitrogen content, plant available calcium, potassium, magnesium, and phosphorus contents of 63 soil samples were measured. She was able to compare the nutrient system of the soils which occurred in different ecological conditions. There are differences between the nutrient status of the soils of the beech and pine forest and the open fields. The knowledge of the pH plus the N, P, K, Ca, Mg content of the soils can be important regarding the protection of the environment, the maintenance of the forest and the management of the meadows.

Acidic cave-wall biofilms located in the Frasassi Gorge, Italy, 2000,
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Vlasceanu L. , Sarbu S. M. , Engel A. S. , Kinkle B. K. ,
Acidic bioflms present on cave walls in the sulfidic region of the Frasassi Gorge, Italy, were investigated to determine their microbial composition and their potential role in cave formation and ecosystem functioning. All biofilm samples examined had pH values <1.0. Scanning electron microscopy of the biofilms revealed the presence of various filaments and rods associated in large clusters with mineral crystals. Qualitative energy-dispersive x-ray analysis was used to determine that the crystals present on the cave walls, associated with the microbial biofilm, were composed of calcium and barium sulfate. Ribosomal RNA-based methods to determine the microbial composition of these biofilms revealed the presence of at least two strains of potential acidophilic, sulfur-oxidizing bacteria, belonging to the genera Thiobacillus and Sulfobacillus. An acid producing strain of Thiobacillus sp. also was obtained in pure culture. Stable isotope ratio analysis of carbon and nitrogen showed that the wall biofilms are isotopically light, suggesting that in situ chemoautotrophic activity plays an important role in this subsurface ecosystem

Timescales for nitrate contamination of spring waters, northern Florida, USA, 2001,
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Katz B. G. , Bohlke J. K. , Hornsby H. D. ,
Residence times of groundwater, discharging from springs in the middle Suwannee River Basin, were estimated using chlorofluorocarbons (CFCs), tritium ((3) H), and tritium/helium-3 (H-3/He-3) age-dating methods to assess the chronology of nitrate contamination of spring waters in northern Florida. During base-flow conditions for the Suwannee River in 1997-1999, 17 water samples were collected from 12 first, second, and third magnitude springs discharging groundwater from the Upper Floridan aquifer. Extending age-dating techniques, using transient tracers to spring waters in complex karst systems, required an assessment of several models [piston-flow (PFM), exponential mixing (EMM), and binary-mixing (BMM)] to account for different distributions of groundwater age. Multi-tracer analyses of four springs yielded generally concordant PFM ages of around 20 2 years from CFC- 12, CFC- 113, H-3, and He-3. with evidence of partial CFC- 11 degradation. The EMM gave a reasonable fit to CFC- 113, CFC- 12. and H-3 data, but did not reproduce the observed He-3 concentrations or H-3/He-3 ratios, nor did a combination PFM-EMM. The BMM could reproduce most of the multi-tracer data set only if both endmembers had H-3 concentrations not much different front modern values. CFC analyses of 14 additional springs yielded apparent PFM ages from about 10 to 20 years from CFC- 113, with evidence of partial CFC- 11 degradation and variable CFC-12 contamination. While it is not conclusive, with respect to the age distribution within each spring, the data indicate that the average residence times were in the order of 10-20 years and were roughly proportional to spring magnitude. Applying similar models to recharge and discharge of nitrate based on historical nitrogen loading data yielded contrasting trends for Suwanee County and Lafayette County. In Suwance County, spring nitrate trends and nitrogen isotope data were consistent with a peak in fertilizer input in the 1970s and a relatively high overall ratio of artificial fertilizer/manure whereas in Lafayette County, spring nitrate trends and nitrogen isotope data were consistent with a more monotonic increase in fertilizer input and relatively low overall ratio of artificial fertilizer/manure. The combined results of this study indicate that the nitrate concentrations of springs in the Suwannee River basin have responded to increased nitrogen loads from various sources in the watersheds over the last few decades, however, the responses have been subdued and delayed because the average residence time of groundwater discharging from springs are in the order of decades. (C) 2001 Published by Elsevier Science B.V

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