bluuebunny/crossref_metadata_2025 huggingface dataset:
Structure of amyloid β fragments in aqueous environments
Authors: Takano Kazufumi , Endo Shuji , Mukaiyama Atsushi , Chon Hyongi , Matsumura Hiroyoshi , Koga Yuichi , Kanaya Shigenori
Published: December 2005

Conformational studies on amyloid β peptide (Aβ) in aqueous solution are complicated by its tendency to aggregate. In this study, we determined the atomic‐level structure of Aβ28−42 in an aqueous environment. We fused fragments of Aβ, residues 10–24 (Aβ10−24) or 28–42 (Aβ28−42), to three positions in the C‐terminal region of ribonuclease HII from a hyperthermophile, Thermococcus kodakaraensis (Tk‐RNase HII). We then examined the structural properties in an aqueous environment. The host protein, Tk‐RNase HII, is highly stable and the C‐terminal region has relatively little interaction with other parts. CD spectroscopy and thermal denaturation experiments demonstrated that the guest amyloidogenic sequences did not affect the overall structure of the Tk‐RNase HII. Crystal structure analysis of Tk‐RNase HII1−197–Aβ28−42 revealed that Aβ28−42 forms a β conformation, whereas the original structure in Tk‐RNase HII1−213 was α helix, suggesting β‐structure formation of Aβ28−42 within full‐length Aβ in aqueous solution. Aβ28−42 enhanced aggregation of the host protein more strongly than Aβ10−24. These results and other reports suggest that after proteolytic cleavage, the C‐terminal region of Aβ adopts a β conformation in an aqueous environment and induces aggregation, and that the central region of Aβ plays a critical role in fibril formation. This study also indicates that this fusion technique is useful for obtaining structural information with atomic resolution for amyloidogenic peptides in aqueous environments.
Induction of PPARβ and prostacyclin (PGI2) synthesis by Raf signaling: failure of PGI2 to activate PPARβ
Authors: Fauti Tanja , Müller‐Brüsselbach Sabine , Kreutzer Mihaela , Rieck Markus , Meissner Wolfgang , Rapp Ulf , Schweer Horst , Kömhoff Martin , Müller Rolf
Published: December 2005

A role for the nuclear receptor peroxisome proliferator‐activated receptor‐β (PPARβ) in oncogenesis has been suggested by a number of observations but its precise role remains elusive. Prostaglandin I2 (PGI2, prostacyclin), a major arachidonic acid (AA) derived cyclooxygenase (Cox) product, has been proposed as a PPARβ agonist. Here, we show that the 4‐hydroxytamoxifen (4‐OHT) mediated activation of a C‐Raf‐estrogen receptor fusion protein leads to the induction of both the PPARβ and Cox‐2 genes, concomitant with a dramatic increase in PGI2 synthesis. Surprisingly, however, 4‐OHT failed to activate PPARβ transcriptional activity, indicating that PGI2 is insufficient for PPARβ activation. In agreement with this conclusion, the overexpression of ectopic Cox‐2 and PGI2 synthase (PGIS) resulted in massive PGI2 synthesis but did not activate the transcriptional activity of PPARβ. Conversely, inhibition of PGIS blocked PGI2 synthesis but did not affect the AA mediated activation of PPARβ. Our data obtained with four different cell types and different experimental strategies do not support the prevailing opinion that PGI2 plays a significant role in the regulation of PPARβ.
Reactivity of the heme–dioxygen complex of the inducible nitric oxide synthase in the presence of alternative substrates
Authors: Lefèvre‐Groboillot David , Boucher Jean‐Luc , Mansuy Daniel , Stuehr Dennis J.
Published: December 2005

Single turnover reactions of the inducible nitric oxide synthase oxygenase domain (iNOSoxy) in the presence of several non α‐amino acid N‐hydroxyguanidines and guanidines were studied by stopped‐flow visible spectroscopy, and compared with reactions using the native substrates l‐arginine (l‐arg) or Nω‐hydroxy‐l‐arginine (NOHA). In experiments containing dihydrobiopterin, a catalytically incompetent pterin, and each of the studied substrates, l‐arg, butylguanidine (BuGua), para‐fluorophenylguanidine (FPhGua), NOHA, N‐butyl‐ and N‐(para‐fluorophenyl)‐N′‐hydroxyguanidines (BuNOHG and FPhNOHG), the formation of a iron(II) heme–dioxygen intermediate (FeIIO2) was always observed. The FeIIO2 species then decayed to iron(III) iNOSoxy at rates that were dependent on the nature of the substrate. Identical reactions containing the catalytically competent cofactor tetrahydrobiopterin (BH4), iNOSoxy and the three N‐hydroxyguanidines, all exhibited an initial formation of an FeIIO2 species that was successively converted to an FeIIINO complex and eventually to high‐spin iron(III) iNOSoxy. The formation and decay kinetics of the FeIIINO complex did not vary greatly as a function of the N‐hydroxyguanidine structure, but the formation of FeIIINO was substoichiometric in the cases of BuNOHG and FPhNOHG. Reactions between BH4‐containing iNOSoxy and BuGua exhibited kinetics similar to those of the corresponding reaction with l‐arginine, with formation of an FeIIO2 intermediate that was directly converted to high‐spin iron(III) iNOSoxy. In contrast, no FeIIO2 intermediate was observed in the reaction of BH4‐containing iNOSoxy and FPhGua. Multi‐turnover reaction of iNOS with FPhGua did not lead to formation of NO or to hydroxylation of the substrate, contrary to reactions with BuGua or l‐arg. Our results reveal how different structural and chemical properties of NOS substrate analogues can impact on the kinetics and reactivity of the FeIIO2 intermediate, and support an important role for substrate pKa during NOS oxygen activation.
Identification of yeast aspartyl aminopeptidase gene by purifying and characterizing its product from yeast cells
Authors: Yokoyama Ryo , Kawasaki Hiroshi , Hirano Hisashi
Published: December 2005

Aspartyl aminopeptidase (EC 3.4.11.21) cleaves only unblocked N‐terminal acidic amino‐acid residues. To date, it has been found only in mammals. We report here that aspartyl aminopeptidase activity is present in yeast. Yeast aminopeptidase is encoded by an uncharacterized gene in chromosome VIII (YHR113W, Saccharomyces Genome Database). Yeast aspartyl aminopeptidase preferentially cleaved the unblocked N‐terminal acidic amino‐acid residue of peptides; the optimum pH for this activity was within the neutral range. The metalloproteases inhibitors EDTA and 1.10‐phenanthroline both inhibited the activity of the enzyme, whereas bestatin, an inhibitor of most aminopeptidases, did not affect enzyme activity. Gel filtration chromatography revealed that the molecular mass of the native form of yeast aspartyl aminopeptidase is ≈ 680 000. SDS/PAGE of purified yeast aspartyl aminopeptidase produced a single 56‐kDa band, indicating that this enzyme comprises 12 identical subunits.
Peroxisome proliferator‐activated receptor α plays a vital role in inducing a detoxification system against plant compounds with crosstalk with other xenobiotic nuclear receptors
Authors: Motojima Kiyoto , Hirai Toshitake
Published: December 2005

Peroxisome proliferator‐activated receptor α (PPARα) is thought to play an important role in lipid metabolism in the liver. To clarify the extra‐hepatic and/or unknown function of PPARα, we previously performed a proteome analysis of the intestinal proteins and identified 17β‐hydroxysteroid dehydrogenase type 11 as a mostly induced protein by a PPARα ligand [Motojima, K. (2004) Eur. J. Biochem. 271, 4141–4146]. Because of its supposed wide substrate specificity, we examined the possibility that PPARα plays an important role in inducing detoxification systems for some natural foods by feeding mice with various plant seeds and grains. Feeding with sesame but not others often killed PPARα knockout mice but not wild‐type mice. A microarray analysis of the sesame‐induced mRNAs in the intestine revealed that PPARα plays a vital role in inducing various xenobiotic metabolizing enzymes in the mouse intestine and liver. A PPARα ligand alone could not induce most of these enzymes, suggesting that there is an essential crosstalk among PPARα and other xenobiotic nuclear receptors to induce a detoxification system for plant compounds.
Long‐Term Performance of In Situ Reactive Barriers for Nitrate Remediation
Authors: Robertson W.D. , Blowes D.W. , Ptacek C.J. , Cherry J.A.
Published: December 2005

Nitrate is now recognized as a widespread ground water contaminant, which has led to increased efforts to control and mitigate its impacts. This study reports on the long‐term performance of four pilot‐scale field trials in which reactive porous barriers were used to provide passive in situ treatment of nitrate in ground water. At two of the sites (Killarney and Borden), the reactive barriers were installed as horizontal layers underneath septic system infiltration beds; at a third site (Long Point), a barrier was installed as a vertical wall intercepting a horizontally migrating septic system plume; and at the fourth site (North Campus), a barrier was installed as a containerized subsurface reactor treating farm field drainage water. The reactive media consisted of 15% to 100% by volume of waste cellulose solids (wood mulch, sawdust, leaf compost), which provided a carbon source for heterotrophic denitrification. The field trials have been in semicontinuous operation for six to seven years at hydraulic loading rates ranging from six to 2000 L/day. Trials have been successful in attenuating influent NO3‐ (or NO3‐+ NH4+ at Borden) concentrations averaging from 4.8 mg/L N at North Campus to 57 mg/L N at Killarney, by amounts averaging 80% at Killarney, 74% at Borden, 91 % at Long Point, and 58% at North Campus. Nitrate consumption rates were temperature dependent and ranged from 0.7 to 32 mg L N/day, but did not deteriorate over the monitoring period. Furthermore, mass‐balance calculations indicate that carbon consumption by heterotrophic denitrification has so far used only about 2% to 3% of the initial carbon mass in each case. Results suggest that such barriers should be capable of providing NO3‐ treatment for at least a decade or longer without carbon replenishment.

Reactive barriers have now been used to treat nitrate contamination from a variety of sources including septic systems, agricultural runoff, landfill leachate, and industrial operations. This demonstration of successful long‐term operation should allow this technology to become more widely considered for nitrate remediation, particularly at sites where passive treatment requiring a minimum of maintenance is desired.
LNAPL Thickness Interpretation Based on Bail‐Down Tests
Authors: Aral Mustafa M. , Liao Boshu
Published: December 2005

In this paper we describe governing equations for fluid recovery processes in a monitoring well. The proposed formulation is based on volumetric equilibrium and multiphase Darcy flow assumptions and may be used in the analysis of bail‐down tests. Through the numerical solution of the mathematical model, we demonstrate that the measurements made at the inflection point of the recovery curve, at which the water/LNAPL interface in the monitoring well changes from a rising level to a falling level, may depend on several parameters. Thus, present methods that use only the LNAPL thickness in the monitoring well at the inflection point to estimate the LNAPL thickness in the aquifer may not yield adequate estimates. Based on our analysis, we propose a new approach to estimate the LNAPL thickness in the aquifer, which relies on information on the LNAPL recovery rate in a monitoring well. In addition to the measurement of the rate of fluid recovery in a monitoring well, the proposed approach also requires information on monitoring well parameters.
Integrating Borehole Logs and Aquifer Tests in Aquifer Characterization
Authors: Paillet Frederick L. , Reese Ronald S.
Published: December 2005

Integration of lithologic logs, geophysical logs, and hydraulic tests is critical in characterizing heterogeneous aquifers. Typically only a limited number of aquifer tests can be performed, and these need to be designed to provide hydraulic properties for the principle aquifers in the system. This study describes the integration of logs and aquifer tests in the development of a hydrostratigraphic model for the surficial aquifer system in and around Big Cypress National Preserve in eastern Collier County, Florida. Borehole flowmeter tests provide qualitative permeability profiles in most of 26 boreholes drilled in the study area. Flow logs indicate the depth of transmissive units, which are correlated across the study area. Comparison to published studies in adjacent areas indicates that the main limestone aquifer of the Tamiami Formation in the study area corresponds with the gray limestone aquifer in western Dade County and the water table and lower Tamiami Aquifer in western Collier County. Four strategically located, multiwell aquifer tests are used to quantify the qualitative permeability profiles provided by the flowmeter log analysis. The hydrostratigraphic model based on these results defines the main aquifer in the central part of the study area as unconfined to semiconfined with a transmissivity as high as 30,000 m2/day. The aquifer decreases in transmissivity to less than 10,000 m2/day in some parts of western Collier County, and becomes confined to the east and northeast of the study area, where transmissivity decreases to below 5000 m2/day.
Assessing an Open‐Well Aquifer Test in Fractured Crystalline Rock
Authors: Tiedeman Claire R. , Hsieh Paul A.
Published: December 2005

Use of open wells to conduct aquifer tests in fractured crystalline rock aquifers is potentially problematic, because open wells can hydraulically connect highly permeable fracture zones at different depths within the rock. Because of this effect, it is questionable whether estimates of the hydraulic properties of the rock obtained from analysis of an open‐well aquifer test in fractured crystalline rock are representative of the true rock properties. To address this issue, rock properties estimated from such a test are compared with rock properties estimated from an aquifer test at the same location in which packers were installed in wells to restrict vertical fluid movement along the wellbores. Results indicate that when the open‐hole test is analyzed with a numerical model that accurately represents the three‐dimensional heterogeneity structure in the wellfield, the open‐hole test estimates of the rock hydraulic properties are similar to the packer‐isolated test estimates. When the open‐well test is analyzed using a model having an oversimplified representation of the rock heterogeneity, the estimates of rock transmissivity are similar to the transmissivity estimates from the packer‐isolated test, but the storativity estimates are larger than the storativity estimates from the packer‐isolated test. These results indicate the importance of accurately representing the rock heterogeneity structure when analyzing an open‐hole aquifer test in fractured crystalline rock.
An Analytical Solution for Stream Depletion by Cyclic Pumping of Wells Near Streams with Semipervious Beds
Authors: Darama Yakup
Published: December 2005

A study was made of the rate of stream depletion produced by cyclic pumping of wells located in a semi‐infinite phreatic aquifer bounded by a partially penetrating stream with semipervious bed. Analytical solutions were developed by applying superposition principles to the solutions for a continuous pumping well near a stream whose bed is semipervious and partially penetrates the aquifer (i.e., Hantush's 1965 solution). A relationship developed by Spalding and Khaleel (1991) was incorporated into the solutions in order to include the effects of the effective pumping distance and stream‐bed clogging layer, which represent the degree of stream penetration and stream‐bed resistance, respectively. A dimensionless plot based on these equations has been developed for the dimensionless volume of stream depletion over a pumping cycle. Analysis of this figure showed that effective resistance of the semipermeable stream bed is the dominant parameter for the determination of equilibrium time. Also a dimensionless plot has been developed to determine the magnitudes of error in the maximum rate of stream depletion at the time at which a practical state of dynamic equilibrium is achieved, when partial penetration of the stream and stream‐bed clogging layer is neglected. Analysis of this figure also showed that neglecting the effects of both the partial penetration of the stream and the resistance of the semipermeable layer of the stream bed produces a substantial amount of error in the maximum stream depletion rates com‐ puted by the methods developed by Wallace et al. (1990) and Darama (1991).
A Strategy For Modeling Ground Water Rebound In Abandoned Deep Mine Systems
Authors: Adams R. , Younger P.L.
Published: December 2005

Discharges of polluted water from abandoned mines are a major cause of degradation of water resources worldwide. Pollution arises after abandoned workings flood up to surface level, by the process termed ground water rebound. As flow in large, open mine voids is often turbulent, standard techniques for modeling ground water flow (which assume laminar flow) are inappropriate for predicting ground water rebound. More physically realistic models are therefore desirable, yet these are often expensive to apply to all but the smallest of systems. An overall strategy for ground water rebound modeling is proposed, with models of decreasing complexity applied as the temporal and spatial scales of the systems under analysis increase. For relatively modest systems (area < 200 km2), a physically based modeling approach has been developed, in which 3‐D pipe networks (representing major mine roadways, etc.) are routed through a variably saturated, 3‐D porous medium (representing the country rock). For systems extending more than 100 to 3000 km2, a semidistributed model (GRAM) has been developed, which conceptualizes extensively interconnected volumes of workings as ponds, which are connected to other ponds only at discrete overflow points, such as major inter‐mine roadways, through which flow can be efficiently modeled using the Prandtl‐Nikuradse pipe‐flow formulation. At the very largest scales, simple water‐balance calculations are probably as useful as any other approach, and a variety of proprietary codes may be used for the purpose.
Assessing Herbicide Concentrations In the Saturated and Unsaturated Zone of a Chalk Aquifer in Southern England
Authors: Gooddy D.C. , Bloomfield J.P. , Chilton P.J. , Johnson A.C. , Williams R.J.
Published: December 2005

The behavior of the herbicides isoproturon (IPU) and chlortoluron (CTU) in ground water and shallow unsaturated zone sediments were evaluated at a site situated on the Chalk in southern England. Concentrations of IPU in ground water samples varied from <0.05 to 0.23 μg/L over a five‐year period of monitoring, and were found to correlate with application of the pesticide. Concentrations of pesticides in ground water samples collected during periods of rising water table were significantly higher than pumped samples and suggest that rapidly infiltrating recharge water contains higher herbicide concentrations than the native ground water. Significant variations in herbicide concentrations were observed over a three‐month period in ground water samples collected by an automated system, with concentrations of IPU ranging from 0.1 to 0.5 μg/L, and concentrations of a recent application of CTU ranging from 0.2 to 0.8 μg/L. Different extraction methods were used to assess pore water concentrations of herbicides in the unsaturated zone, and samples were analyzed by standard HPLC analysis and immunoassay (ELISA) methods. These data indicated highly variable concentrations of herbicide ranging from 4 to 200 g/ha for HPLC and 0.01 to 0.04 g/ha for ELISA, but indicate a general pattern of decreasing concentrations with depth. The results of this study indicate that transport of IPU and CTU through the unsaturated zone to shallow ground water occurs and that this transport Increases immediately following herbicide application. Measured concentrations of herbicides are generally lower than specified by the European Union Drinking Water Directive, but are observed to spike above this limit. These results imply that, while delivery of pesticides to ground water can occur as a result of normal agricultural practices, the Impact on potable supplies Is likely to be negligible due to the potential for degradation during the relatively long travel time through the unsaturated zone and high degree of dilution that occurs within the aquifer. As a result of the wide variation in concentrations detected by different techniques, it is suggested that for future site Investigations more than one sampling strategy be employed to characterize the occurrence of pesticide residues and elucidate the transport mechanisms.
A Comparison of Solute‐Transport Solution Techniques and Their Effect on Sensitivity Analysis and Inverse Modeling Results
Authors: Mehl Steffen , Hill Mary C.
Published: December 2005

Five common numerical techniques for solving the advection‐dispersion equation (finite difference, predictor corrector, total variation diminishing, method of characteristics, and modified method of characteristics) were tested using simulations of a controlled conservative tracer‐test experiment through a heterogeneous, two‐dimensional sand tank. The experimental facility was constructed using discrete, randomly distributed, homogeneous blocks of five sand types. This experimental model provides an opportunity to compare the solution techniques: the heterogeneous hydraulic‐conductivity distribution of known structure can be accurately represented by a numerical model, and detailed measurements can be compared with simulated concentrations and total flow through the tank. The present work uses this opportunity to investigate how three common types of results—simulated breakthrough curves, sensitivity analysis, and calibrated parameter values—change in this heterogeneous situation given the different methods of simulating solute transport. The breakthrough curves show that simulated peak concentrations, even at very fine grid spacings, varied between the techniques because of different amounts of numerical dispersion. Sensitivity‐analysis results revealed: (1) a high correlation between hydraulic conductivity and porosity given the concentration and flow observations used, so that both could not be estimated; and (2) that the breakthrough curve data did not provide enough information to estimate individual values of dispersivity for the five sands. This study demonstrates that the choice of assigned dispersivity and the amount of numerical dispersion present in the solution technique influence estimated hydraulic conductivity values to a surprising degree.
A Modification to the Bouwer and Rice Method of Slug‐Test Analysis for Large‐Diameter, Hand‐Dug Wells
Authors: Rupp David E. , Selker John S. , Šimunek Jirka
Published: December 2005

The Bouwer and Rice method of estimating the saturated hydraulic conductivity (Ks) from slug‐test data was evaluated for geometries typical of hand‐dug wells. A two‐dimensional, radially symmetric and variably saturated, ground water transport model was used to simulate well recovery given a range of well and aquifer geometries and unsaturated soil properties, the latter in terms of the van Genuchten parameters. The standard Bouwer and Rice method, when applied to the modeled recharge rates, underestimated Ks by factors ranging from 1.3 to 5.6, depending on the well geometry and the soil type. The Bouwer and Rice analytical solution was modified to better explain the recovery rates as predicted by the numerical model, which revealed a significant dependence on the unsaturated soil for the shallow and wide geometries that are typical of traditional wells. The modification introduces a new parameter to the Bouwer and Rice analysis that is a measure of soil capillarity which improves the accuracy of Ks estimates by tenfold for the geometries tested.
An Assessment of a Mesocosm Approach to the Study of Microbial Respiration in a Sandy Unsaturated Zone
Authors: Hendry M.J. , Mendoza C.A. , Kirkland R. , Lawrence J.R.
Published: December 2005

Microbial respiration rates were determined through a 3.2 m thick, sandy unsaturated zone in a 2.4 m diameter X 4.6 m high mesocosm. The mesocosm was maintained under near constant temperature (18° to 23°C) and reached steady moisture content conditions after several hundred days. Soil‐gas CO2 concentrations in the mesocosm ranged from 0.09% to 3.31% and increased with depth. Respiration rates within the mesocosm were quantified over a 342–day period using measured CO2 concentrations and a transient, one‐dimensional finite‐element model. Microbial respiration rates were 2 × 10–1μg C·g−1·d−1 throughout most of the system, but decreased to 10–4 to 10–3μg C·g−1·d−1 within the capillary fringe. Microbial respiration rates were also determined in minicosms (500 g sample mass) over a range in temperatures (4° to 30°C) and volumetric moisture contents (0.044 to 0.37). The functional dependence of CO2 production on temperature and soil‐moisture content was similar for the two scales of laboratory observation. Respiration rates in the minicosms, for temperatures and moisture contents in the mesocosm, were up to an order of magnitude greater than those determined for the mesocosm. The higher respiration rates in the minicosms, compared to the mesocosm, were attributed to greater disturbance of the samples and to shorter acclimation time in the minicosms. Extrapolating the laboratory respiration rates to field conditions yielded rates that were two to three orders of magnitude greater than rates previously determined in situ for C‐horizon material. Results show that in situ microbial reaction rates determined using disturbed samples in minicosms and mesocosms yielded respiration rates that greatly exceeded field conditions. Mesocosms can, however, provide a useful environment for conducting process‐related research in unsaturated environments.
Arsenic in Glacial Drift Aquifers and the Implication for Drinking Water—Lower Illinois River Basin
Authors: Warner Kelly L.
Published: December 2005

The lower Illinois River Basin (LIRB) covers 47,000 km2 of central and western Illinois. In the LIRB, 90% of the ground water supplies are from the deep and shallow glacial drift aquifers. The deep glacial drift aquifer (DGDA) is below 152 m altitude, a sand and gravel deposit that fills the Mahomet Buried Bedrock Valley, and overlain by more than 30.5 m of clayey till. The LIRB is part of the USGS National Water Quality Assessment program, which has an objective to describe the status and trends of surface and ground water quality.

In the DGDA, 55% of the wells used for public drinking‐water supply and 43% of the wells used for domestic drinking water supply have arsenic concentrations above 10 μg/L (a new U.S. EPA drinking water standard). Arsenic concentrations greater than 25 μg/L in ground water are mostly in the form of arsenite (AsIII). The proportion of arsenate (AsV) to arsenite does not change along the flowpath of the DGDA. Because of the limited number of arsenic species analyses, no clear relations between species and other trace elements, major ions, or physical parameters could be established. Arsenic and barium concentrations increase from east to west in the DGDA and are positively correlated. Chloride and arsenic are positively correlated and provide evidence that arsenic may be derived locally from underlying bedrock.

Solid phase geochemical analysis of the till, sand and gravel, and bedrock show the highest presence of arsenic in the underlying organic‐rich carbonate bedrock. The black shale or coal within the organic‐rich carbonate bedrock is a potential source of arsenic. Most high arsenic concentrations found in the DGDA are west and downgradient of the bedrock structural features. Geologic structures in the bedrock are potential pathways for recharge to the DGDA from surrounding bedrock.
Trace Metal Concentrations in Shallow Ground Water
Authors: Zelewski Linda M. , Krabbenhoft David P. , Armstrong David E.
Published: December 2005

Trace metal clean sampling and analysis techniques were used to examine the temporal patterns of Hg, Cu, and Zn concentrations in shallow ground water, and the relationships between metal concentrations in ground water and in a hydrologically connected river. Hg, Cu, and Zn concentrations in ground water ranged from 0.07 to 4.6 ng L−1, 0.07 to 3.10 μg L−1, and 0.17 to 2.18 μg L−1, respectively. There was no apparent seasonal pattern in any of the metal concentrations. Filtrable Hg, Cu, and Zn concentrations in the North Branch of the Milwaukee River ranged from below the detection limit to 2.65 ng Hg L−1,0.51 to 4.30 μg Cu L−1, and 0.34 to 2.33 μg Zn L−1. Thus, metal concentrations in ground water were sufficiently high to account for a substantial fraction of the filtrable trace metal concentration in the river. Metal concentrations in the soil ranged from 8 to 86 ng Hg g−1, 10 to 39 μg Cu g−1, and 15 to 84 μg Zn g−1. Distribution coefficients, KD, in the aquifer were 7900,22,000, and 23,000 L kg−1 for Hg, Cu, and Zn, respectively. These values were three to 40 times smaller than KD values observed in the Milwaukee River for suspended particulate matter.
The Steady‐State Dipole‐Flow Test for Characterization of Hydraulic Conductivity Statistics in a Highly Permeable Aquifer: Horkheimer Insel Site, Germany
Authors: Zlotnik Vitaly A. , Zurbuchen Brian R. , Ptak Thomas
Published: December 2005

Over the last decade the dipole‐flow test (DFT) evolved from the general idea of using recirculatory flow to evaluate aquifer properties, to the development of prototype instrumentation and feasibility studies, to a reliable tool for characterization of aquifer heterogeneity. The DFT involves the interpretation of head in recirculatory flow between injection and extraction sections (chambers) in a single well isolated from each other by a multipacker system. In this study, the steady‐state dipole flow test (DFT) has been used to characterize the statistics of horizontal hydraulic conductivity (Kr) of the highly permeable, heterogeneous, and thin aquifer at the Horkheimer Insel site, Germany. In previous studies, Kr estimates were based on the steady‐state head difference between chambers. A new by‐chamber interpretation is proposed that is based on drawdown within each individual chamber. This interpretation yields more detailed information on structure of heterogeneity of the aquifer without introducing complexity into the analysis. The DFT results indicate that Kr ranges from 49 to 6000 m/day (mean In Kr [(m/s)]∼—4, and variance of In Kr [(m/s)] ∼ 1–2). Descriptive statistics from the DFT compare well with those from previous field and laboratory tests (pumping, borehole flowmeter, and permeameter tests and grain‐size analysis) at this site. It is shown that the role of confining boundaries in the DFT interpretation is negligible even in this case of a thin (< 4 m thick) aquifer. This study demonstrates the flexibility of the DFT and expands the potential application of this method to a wide range of hydrogeologic settings.
Effect of Natural Gas Exsolution on Specific Storage in a Confined Aquifer Undergoing Water Level Decline
Authors: Yager Richard M. , Fountain John C.
Published: December 2005

The specific storage of a porous medium, a function of the compressibility of the aquifer material and the fluid within it, is essentially constant under normal hydrologic conditions. Gases dissolved in ground water can increase the effective specific storage of a confined aquifer, however, during water level declines. This causes a reduction in pore pressure that lowers the gas solubility and results in exsolution. The exsolved gas then displaces water from storage, and the specific storage increases because gas compressibility is typically much greater than that of water or aquifer material.

This work describes the effective specific storage of a confined aquifer exsolving dissolved gas as a function of hydraulic head and the dimensionless Henry's law constant for the gas. This relation is applied in a transient simulation of ground water discharge from a confined aquifer system to a collapsed salt mine in the Genesee Valley in western New York. Results indicate that exsolution of gas significantly increased the effective specific storage in the aquifer system, thereby decreasing the water level drawdown.
Ground Water/Surface Water Interactions in Lake Naivasha, Kenya, Using δ18O, δD, and 3H/3He Age‐Dating
Authors: Ojiambo Bwire S. , Poreda Robert J. , Lyons W. Berry
Published: December 2005

We have analyzed a series of ground water samples from the Lake Naivasha region, Kenya, for their helium isotopic composition. Lake Naivasha is unique among the East Africa Rift Valley lakes in that it is fresh. It has long been thought that the low salinity of this lake is due, in part, to rapid water loss from the lake into the local ground water system. Our results show that the Olkaria geothermal waters, south of the lake, are devoid of tritium and, thus, are more than 50 years old. An important implication of these results is that even if Olkaria geothermal reservoir water originated from Lake Naivasha, it has been underground for a long time, (>50 years) and is not derived from present‐day Lake Naivasha water. This flow time is of the same order of magnitude as conservative major solutes, such as chloride, as determined through residence time calculations. On the north side of Lake Naivasha, deep wells (91 m) have water ∼ 20 years old. Water from these wells has stable isotopic values resembling those of nearby rivers, and high‐elevation eastern Rift water. This indicates that this water recharges from rains from high eastern Rift Valley escarpments. Many of the shallow wells on the south side of the lake have 3H/3He ages between four and 17 years. The young ages and the δ18 O‐enriched signature of the water from these wells indicate that they are recharged by a mixture of water from the lake, Rift flanks, and water from deep pumping wells that is recharged during irrigation. Water mixing ratio calculations using δ18O and δD isotopes show that about 50% to 70% of the southern ground water system is derived from the lake, while the Olkaria geothermal reservoir water shows that 40% to 50% of this water is originally lake water. Calculated mean recharge rates range from 0.10 to 1.59 m/yr with a mean of 0.52±0.40 m/yr. Estimated horizontal velocity from 3H/3He age dating between Lake Naivasha and a well about 3 km to the south is 75 m/yr, giving average horizontal hydraulic conductivity of 6 m/day.
Introduction of Wavelet Analyses to Rainfall/Runoffs Relationship for a Karstic Basin: The Case of Licq‐Atherey Karstic System (France)
Authors: Labat David , Ababou Rachid , Mangin Alain
Published: December 2005

Karstic systems are highly heterogeneous geological formations characterized by a multiscale temporal and spatial hydrologic behavior with more or less localized temporal and spatial structures. Classical correlation and spectral analyses cannot take into account these properties. Therefore, it is proposed to introduce a new kind of transformation: the wavelet transform. Here we focus particularly on the use of wavelets to study temporal behavior of local precipitation and watershed runoffs from a part of the karstic system. In the first part of the paper, a brief mathematical overview of the continuous Morlet wavelet transform and of the multiresolution analysis is presented. An analogy with spectral analyses allows the introduction of concepts such as wavelet spectrum and cross‐spectrum. In the second part, classical methods (spectral and correlation analyses) and wavelet transforms are applied and compared for daily rainfall rates and runoffs measured on a French karstic watershed (Pyrenees) over a period of 30 years.

Different characteristic time scales of the rainfall and runoff processes are determined. These time scales are typically on the order of a few days for floods, but they also include significant half‐year and one‐year components and multi‐annual components. The multiresolution cross‐analysis also provides a new interpretation of the impulse response of the system. To conclude, wavelet transforms provide a valuable amount of information, which may be now taken into account in both temporal and spatially distributed karst modeling of precipitation and runoff.
Evaluation of Recharge in a Small Temperate Catchment Using Natural and Applied δ18O Profiles in the Unsaturated Zone
Authors: McConville C. , Kalin R.M. , Johnston H. , McNeill G.W.
Published: December 2005

A water balance study was used for determining recharge rate and mechanisms in the Enler Catchment, Northern Ireland. Here spatially limited data for the water balance resulted in varied calculation of the annual and monthly net infiltration rate. This paper outlines a method whereby high‐resolution soil profiles (1 to 2 cm) were obtained from field cores in the upper 2 m of the unsaturated zone using δ18O of water. These profiles show changes in isotopic composition that range from individual rainfall events to annually integrated cycles of rainfall. Recharge rates were calculated from stable isotope profiles for each of the four main soil types in the study catchment and summed over each area resulting in an average recharge in the range 55 to 70 mm/a, which is comparable with previous findings. Applied isotopic tracer tests were also conducted to evaluate the extent of preferential flow through the two main soil types in the catchment. Rates of water movement found from these experiments show good agreement with natural isotopic profiles; however, evidence suggests that preferential flow is not the dominant process controlling water movement in this catchment. This type of data provides valuable information about recharge rates and mechanisms and may facilitate better prediction of contaminant transport pathways in the vadose zone.
Delineating a Recharge Area for a Spring Using Numerical Modeling, Monte Carlo Techniques, and Geochemical Investigation
Authors: Hunt Randall J. , Steuer Jeffery J. , Mansor M. Teresa C. , Bullen Thomas D.
Published: December 2005

Recharge areas of spring systems can be hard to identify, but they can be critically important for protection of a spring resource. A recharge area for a spring complex in southern Wisconsin was delineated using a variety of complementary techniques. A telescopic mesh refinement (TMR) model was constructed from an existing regional‐scale ground water flow model. This TMR model was formally optimized using parameter estimation techniques; the optimized “best fit” to measured heads and fluxes was obtained by using a horizontal hydraulic conductivity 200% larger than the original regional model for the upper bedrock aquifer and 80% smaller for the lower bedrock aquifer. The uncertainty in hydraulic conductivity was formally considered using a stochastic Monte Carlo approach. Two‐hundred model runs used uniformly distributed, randomly sampled, horizontal hydraulic conductivity values within the range given by the TMR optimized values and the previously constructed regional model. A probability distribution of particles captured by the spring, or a “probabilistic capture zone,” was calculated from the realistic Monte Carlo results (136 runs of 200). In addition to portions of the local surface watershed, the capture zone encompassed areas outside of the watershed—demonstrating that the ground watershed and surface watershed do not coincide. Analysis of water collected from the site identified relatively large contrasts in chemistry, even for springs within 15 m of one another. The differences showed a distinct gradation from Ordovician‐carbonate‐dominated water in western spring vents to Cambrian‐sandstone‐influenced water in eastern spring vents. The difference in chemistry was attributed to distinctive bedrock geology as demonstrated by overlaying the capture zone derived from numerical modeling over a bedrock geology map for the area. This finding gives additional confidence to the capture zone calculated by modeling.
Migration of Induced‐Infiltrated Stream Water into Nearby Aquifers Due to Seasonal Ground Water Withdrawal
Authors: Chen Xunhong
Published: December 2005

Analysis of stream‐aquifer interaction due to ground water extraction has traditionally focused on the determination of the amount of water depleted in the stream. Less attention has been paid to the movement of infiltrated stream water inside aquifer, particularly for agricultural areas. This paper presents a method of using particle‐tracking techniques to evaluate the transport of the leaked stream water in the nearby aquifers. Simple stream‐aquifer conditions are used to demonstrate the usefulness of the analysis. Travel times, pathlines, and influence zones of stream water were determined between a stream and nearby pumping wells for seasonal ground water extraction areas. When water quantity is a concern, the analyses provide additional information about stream depletion; when water quality is an issue, they offer information for wellhead protection. Analyses were conducted for transient conditions, and both pumping and nonpumping periods were considered. According to the results from the simulation examples, migration of infiltrated stream water into the nearby aquifers is generally slow and most infiltrated stream water does not arrive at the pumping well at the end of a 90‐day irrigation season. Infiltrated stream water may remain in the aquifer for several years before arriving at the pumping well. For aquifers with a regional hydraulic gradient toward streams, part of the infiltrated stream water may discharge back to streams during a recovery period.
Application of a Nonlinear Slug Test Model
Authors: McElwee CD.
Published: December 2005

Knowledge of the hydraulic conductivity distribution is of utmost importance in understanding the dynamics of an aquifer and in planning the consequences of any action taken upon that aquifer. Slug tests have been used extensively to measure hydraulic conductivity in the last 50 years since Hvorslev's (1951) work. A general nonlinear model based on the Navier‐Stokes equation, nonlinear frictional loss, non‐Darcian flow, acceleration effects, radius changes in the wellbore, and a Hvorslev model for the aquifer has been implemented in this work. The nonlinear model has three parameters: β, which is related primarily to radius changes in the water column; A, which is related to the nonlinear head losses; and K, the hydraulic conductivity. An additional parameter has been added representing the initial velocity of the water column at slug initiation and is incorporated into an analytical solution to generate the first time step before a sequential numerical solution generates the remainder of the time solution. Corrections are made to the model output for acceleration before it is compared to the experimental data. Sensitivity analysis and least squares fitting are used to estimate the aquifer parameters and produce some diagnostic results, which indicate the accuracy of the fit. Finally, an example of field data has been presented to illustrate the application of the model to data sets that exhibit nonlinear behavior. Multiple slug tests should be taken at a given location to test for nonlinear effects and to determine repeatability.
Subsurface Transfer of Chloride After a Lake Retreat in the Central Andes
Authors: Coudrain Anne , Talbi Amal , Ledoux Emmanuel , Loubet Michel , Vacher Jean , Ramirez Edson
Published: December 2005

The area under study covers 3500 km2 in the upstream part of the closed catchment basin of the salt crust of Uyuni. This crust is a remnant of the saline Lake Tauca, which covered the area about 15,000 years ago. In the downstream part of the aquifer, the Cl concentration of ground water and Cl content in the unsaturated zone exceed 20 meq/L and 18 kg/m2, respectively. With the present hydrological conditions under semiarid conditions, the ground water residence time in the study area exceeds 3000 years. Transient simulations over 11,000 years were made using initial conditions as the retreat of Lake Tauca and taking into account a low recharge during the arid mid‐Holocene period. The modeling simulates ground water flow, Cl transport, and ground water residence time. It includes the evaporation from the aquifer that leads to the accumulation of chloride in the unsaturated zone. Results of the modeling are consistent with the observations if it is assumed that the Cl previously accumulated in the unsaturated zone was flushed back into the aquifer around 2000 years B.P., contemporaneously with the end of the arid period.
Characterization and Origin of Dissolved Organic Carbon in Yegua Ground Water in Brazos County, Texas
Authors: Routh Joyanto , Grossman Ethan L. , Murphy Ellyn M. , Benner Ronald
Published: December 2005

Dissolved organic carbon (DOC) concentrations in five shallow (< 20 m) and three deeper wells (27 to 30 m) in the Eocene Yegua Formation (Brazos County in east‐central Texas) ranged from 92 to 500 μm. Characterization of high, intermediate, and low molecular weight DOC fractions (HMW > 3000 amu, IMW 1000 to 3000 amu, and LMW 500 to 1000 amu) and combined neutral sugar analyses provide information on organic matter sources in the Yegua aquifers. Combined neutral sugars ranged in concentration from 0.6 to 2.7 μmol/L and comprised 0.8% to 6.7% of DOC in ground water. Glucose was the most abundant neutral sugar, followed by xylose and galactose, arabinose, mannose, rhamnose, and fucose. These combined neutral sugars were more diagenetically altered in shallow, oxic ground water as indicated by high mole % fucose + rhamnose and low neutral sugar yield. The precursors for neutral sugars are most probably angiosperm leaves, which show a similar distribution pattern of neutral sugars. Ground water DOC was depleted in 13C relative to soil‐zone organic matter (OM) (−16‰ to −19‰). The δ13C values of bulk DOC and HMW DOC ranged from −24‰ to –32‰, whereas LMW and IMW DOC ranged from −32‰ to −34‰ and ‰16‰ to ‰28‰, respectively. This variability in δ13C values is probably related to microbial processes and selective preservation of OM. Carbon isotope analyses in bulk and different molecular weight DOC fractions imply a predominantly C3 OM source and a low contribution of soil‐zone OM to DOC.
Estimating Recharge Distribution by Incorporating Runoff from Mountainous Areas in an Alluvial Basin in the Great Basin Region of the Southwestern United States
Authors: Stone Dan B. , Moomaw Cynthia L. , Davis Andy
Published: December 2005

A method is described to estimate the distribution of ground water recharge within hydrographic basins in the Great Basin region of the southwestern United States on the basis of estimated runoff from high mountainous areas and subsequent infiltration in alluvial fans surrounding the intermontane basins. The procedure involves a combination of Geographic Information System (GIS) analysis, empirical surface‐runoff modeling, and water‐balance calculations. The method addresses the need to develop and incorporate constraints on the distribution of recharge in regional‐scale ground water flow modeling of arid and semiarid environments. The conceptual approach and methodology were developed for Crescent Valley, Nevada. However, the concept and method are generally applicable to any region where excess precipitation in upland areas is conveyed to lower elevations before it infiltrates to recharge the ground water system. Application of the procedure to a ground water flow model of Crescent Valley appears both qualitatively and quantitatively to result in a more accurate representation of actual recharge conditions than might otherwise have been prescribed.