bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ground‐Water Flow in the Coastal Plain Aquifers of South Carolina
Authors: Aucott Walter R. , Speiran Gary K. 
Published: March 2006

ABSTRACTThe characteristics of the Coastal Plain aquifers of South Carolina are being studied as a part of the Regional Aquifer System Analysis program of the United States Geological Survey. Potentiometric maps were constructed for the Middendorf aquifer of Cretaceous age and for the Floridan aquifer system and its sand facies equivalent, Tertiary sand aquifer, prior to development. Also constructed was a potentiometric decline map for the period prior to development to November 1982 for the Middendorf aquifer. These maps are used to describe the ground‐water flow system.The Coastal Plain aquifers are recharged primarily by precipitation in their outcrop areas. Ground water flows from these areas of recharge, through the aquifers, and discharges to upper Coastal Plain rivers, overlying aquifers as upward leakage, and wells.Ground‐water flow in the Floridan aquifer system and the Tertiary sand aquifer prior to development is generally perpendicular to the coast. Predevelopment flow in the Cretaceous aquifers, however, turns northeastward as it approaches the coast, almost paralleling the coast. The change in flow direction is caused by less effective intervening confining units, the aquifers being closer to the land surface, and the rivers at lower altitudes farther upstream in the vicinity of the North Carolina/South Carolina State line.Water‐level declines in the Cretaceous aquifers have occurred throughout much of the eastern part of the Coastal Plain of South Carolina due to pumpage in the Myrtle Beach and Florence areas. Large areally extensive water‐level declines have also occurred in the Floridan aquifer system in South Carolina due to pumpage in the Savannah, Georgia area.
A Tube and Cartridge Method for Down‐Hole Sampling for Trace Organic Compounds in Ground Water
Authors: Pankow James F. , Isabella Lome M. , Hewetson Janet P. , Cherry John A. 
Published: March 2006

ABSTRACTA small ground‐water sampling device has been developed which extends the down‐hole use of the adsorption/thermal desorption (ATD) analysis method for nonpolar organic compounds to very narrow piezometers (I.D. > 0.64 cm). The sampler consists of a sorbent cartridge, a flow restrictor, and a tube leading to the ground surface. The device is lowered down a piezometer, and water‐column pressure forces the sample through the cartridge. In the laboratory, the water is removed from the cartridge and the sorbed compounds are thermally desorbed to a gas chromatography (GC) column for analysis. Since the analytes are sorbed on the cartridge down‐hole, volatilization losses are avoided. Samples can be obtained without being influenced by the water column above the sampler or by tubing or pumps; many uncertainties associated with well purging and contamination from well casings and samplers can be minimized. The method was tested by sampling at a landfill. The coefficients of variation were in the 10‐18% range at the low μg/1 level. The limits of detection for several compounds were all under 0.1 μg/1, some being less than 1 ng/1. Sorption efficiencies of >93% were found for a variety of compounds. The method will be attractive when sensitivity and freedom from volatilization losses and sampler‐related contamination are required.
AUTOMATED DERIVATION OF PARAMETERS IN A NONLEAKY CONFINED AQUIFER WITH TRANSIENT FLOWa
Authors: Mukhopadhyay Amitabha 
Published: March 2006

Abstract.Values of transmissivity and storage commonly are derived for a nonleaky confined aquifer by manual curve matching of pumping‐test data. Automatic matching of pumping‐test data with the Theis type curve is possible using the method of least squares, provided the Cooper‐Jacob approximation of the well function W(u) is considered. A FORTRAN program was developed to carry out this automated matching. Results derived from published data show that the method gives parameters close to the ones derived by the standard method of manual curve matching.
Migration and Attenuation of Selected Organics in a Sandy Aquifer – A Natural Gradient Experiment
Authors: Sutton P. A. , Barker J. F. 
Published: March 2006

ABSTRACTA natural gradient tracer test was conducted in an unconfined sandy aquifer at Borden, Ontario. N‐butyric acid, phenol, p‐chlorophenol, and dimethyl phthalate (DMP) were used as organic tracers at concentrations ranging from 70 to 100 ppm and chloride was used as a nonreactive tracer at a concentration of 243 ppm. Approximately 2,100 1 were injected below the water table and were monitored with a three‐dimensional network of bundle‐type, multilevel piezometers over a period of 60 days and once again after 204 days.The plume gradually split into two zones due to local heterogeneity. The centers of mass for the organic compounds migrated at essentially the same rate as chloride, but attenuated at different rates. Butyric acid and phenol attenuated the most rapidly. Chlorophenol attenuated only slightly faster than chloride and DMP attenuated at roughly the same rate as chloride. Sorption does not appear to be important in the system studied. Dispersion and biodegradation probably produced the observed attenuation of organics.
Determination of Microbial Cell Numbers in Subsurface Samples
Authors: Webster JoAnn J. , Hampton Ginger J. , Wilson John T. , Ghiorse William C. , Leach Franklin R. 
Published: March 2006

ABSTRACTGround‐water pollution by organic compounds has become a major environmental concern. Because the transport and fate of the organic pollutants may be influenced by microorganisms present in subsurface material, reliable measurements of the number of organisms in subsurface samples and their metabolic activity are needed. A special drilling rig and aseptic procedures have been developed by the Robert S. Kerr Environmental Research Laboratory of the United States Environmental Protection Agency to yield uncontaminated subsurface samples. The number of bacteria in subsurface samples has been determined by microscopic counting after acridine orange staining; the proportion of cells capable of respiration was determined by INT reduction. An independent measure of metabolic activity was obtained by measuring ATP extracted from the samples. A procedure and extradant for the extraction of ATP from subsurface material have been developed. The extractant contains reagents to reduce the loss of the extracted ATP. Subsurface samples from Oklahoma and Texas contain 106‐107 cells per g of subsurface material (depths of 2–9 m). Both methods show that usually between 1 and 10% of the cells were metabolically active. Thus, significant numbers of metabolically active bacteria exist in subsurface material with the potential to modify pollutants.
Nitrogen‐Isotope Ratios of Nitrate in Ground Water Under Fertilized Fields, Long Island, New York
Authors: Flipse William J. , Bonner Francis T. 
Published: March 2006

ABSTRACTGround‐water samples from two heavily fertilized sites in Suffolk County, New York, were collected through the 1978 growing season and analyzed for nitrate‐N concentrations and nitrogen‐isotope ratios. Six wells were at a potato farm; six were on a golf course. The purpose of this study was to determine whether the 15N/14N ratios (δ15N values) of fertilizer are increased during transit from land surface to ground water to an extent which would preclude use of this ratio to distinguish agricultural from animal sources of nitrate in ground water.Ground water at both sites contained a greater proportion of 15N than the fertilizers being applied. At the potato farm, the average δ15N value of the fertilizers was 0.2%0; the average δ15N value of the ground‐water nitrate was 6.2 %0. At the golf course, the average δ15N value of the fertilizers was ‐5.9%0, and that of ground‐water nitrate was 6.5%0. The higher δ15N values of ground‐water nitrate are probably caused by isotopic fractionation during the volatile loss of ammonia from nitrogen applied in reduced forms (NH+4 and organic‐N).The δ15N values of most ground‐water samples from both areas were less than 10%0, the upper limit of the range characteristic of agricultural sources of nitrate; these sources include both fertilizer nitrate and nitrate derived from increased mineralization of soil nitrogen through cultivation. Previous studies have shown that the S15N values of nitrate derived from human or animal waste generally exceed 10%0. The nitrogen‐isotope ratios of fertilizer‐derived nitrate were not altered to an extent that would make them indistinguishable from animal‐waste‐derived nitrates in ground water.
Comparison of Methods for Estimating Ground‐Water Pumpage for Irrigation
Authors: Frenzel Steven A. 
Published: March 2006

ABSTRACTGround‐water pumpage for irrigation was measured at 32 sites on the eastern Snake River Plain in southern Idaho during 1983. Pumpage at these sites also was estimated by three commonly used methods, and pumpage estimates were compared to measured values to determine the accuracy of each estimate.Statistical comparisons of estimated and metered pumpage using an F‐test showed that only estimates made using the instantaneous discharge method were not significantly different (α. = 0.01) from metered values.Pumpage estimates made using the power consumption method reflect variability in pumping efficiency among sites. Pumpage estimates made using the crop‐consumptive use method reflect variability in water‐management practices. Pumpage estimates made using the instantaneous discharge method reflect variability in discharges at each site during the irrigation season.
Predictive Accuracy of a Ground–Water Model — Lessons from a Postaudit
Authors: Konikow Leonard F. 
Published: March 2006

ABSTRACTHydrogeologic studies commonly include the development, calibration, and application of a deterministic simulation model. To help assess the value of using such models to make predictions, a postaudit was conducted on a previously studied area in the Salt River and lower Santa Cruz River basins in central Arizona. A deterministic, distributed‐parameter model of the ground‐water system in these alluvial basins was calibrated by Anderson (1968) using about 40 years of data (1923–64). The calibrated model was then used to predict future water‐level changes during the next 10 years (1965–74). Examination of actual water‐level changes in 77 wells from 1965–74 indicates a poor correlation between observed and predicted water‐level changes. The differences have a mean of 73 ft that is, predicted declines consistently exceeded those observed and a standard deviation of 47 ft. The bias in the predicted water‐level change can be accounted for by the large error in the assumed total pumpage during the prediction period. However, the spatial distribution of errors in predicted water‐level change does not correlate with the spatial distribution of errors in pumpage. Consequently, the lack of precision probably is not related only to errors in assumed pumpage, but may indicate the presence of other sources of error in the model, such as the two‐dimensional representation of a three‐dimensional problem or the lack of consideration of land‐subsidence processes. This type of postaudit is a valuable method of verifying a model, and an evaluation of predictive errors can provide an increased understanding of the system and aid in assessing the value of undertaking development of a revised model.
Comparative Study of Ground‐Water Mapping Techniques
Authors: Rouhani Shahrokh 
Published: March 2006

ABSTRACTMapping of ground‐water spatial data is an important part of any geohydrologic investigation. There are three main classes of interpolators used for such mappings. The first group include simple estimators which are commonly used in practice. The second group are least‐squares estimators which are basically fitting processes. The last category are Gauss‐Markov estimators, such as kriging, which beside being exact interpolators, produce measures for the accuracy of the estimated field. These estimators are compared theoretically and numerically. These studies show that kriging yields relatively robust estimates. However, its suggested statistical inference method may not always produce robust estimates of the covariance function parameters. Simple estimators produce unstable results, while least‐squares methods ignore local variations by fitting a single polynomial function over the whole field. For this study, water‐table data from northwest Kansas are used.
Chromium Migration Through Sludge‐Treated Soils
Authors: Dreiss Shirley J. 
Published: March 2006

ABSTRACTThe Environmental Protection Agency and the Tanner's Council of America jointly initiated a five‐year project in September 1980 to investigate the feasibility of using land treatment to dispose of chromium tanning sludges. These sludges contain high concentrations of Cr, in the range of 21,000 to 55,000 ppm on a dry weight basis. Chromium could migrate in soil waters at a land treatment site as either a soluble Cr (VI) species, HCrO4 or CrO42, or as Cr (III) or Cr (VI) in soluble complexes with organic or inorganic substances. Field measurements of Cr fluxes at an experimental test site near Santa Cruz, California indicate that Cr in tannery sludges exhibits a very low mobility. Less than 0.1% of the total Cr applied to a test plot was transported through the upper soil zone during a three‐month period. However, the sludge applications introduced high concentrations of nitrates and major cations. Estimates of contaminant fluxes based on measured concentrations in soil water collected with porous cup samplers contain large uncertainties. In addition to potential errors in moisture flux computations, chemical reactions in the cups can significantly alter the composition of soil‐water samples.
Contaminant Movement Under Pumpage‐Recharge Condition in Steady Ground‐Water Flow System
Authors: Gupta A. Das , Shrestha P. R. Onta 
Published: March 2006

ABSTRACTThe transient movement of contaminant under pumpage and recharge conditions in steady ground‐water flow in a vertical cross section of a confined aquifer is simulated using a finite‐element numerical model based on Galerkin technique. Various factors like time step, space increment, and boundary condition affecting the accuracy of the numerical solution are considered in validating results of the numerical model with results of an analytical solution. The solution with the application problem illustrates the effectiveness of subsequent operation of pumpage on the movement of contaminant downstream of the point of injection.
Saturated Thickness for Drought and Litigation Protection
Authors: Peralta Richard C. , Dutram Paul W. , Peralta Ann W. , Yazdanian Amin 
Published: March 2006

ABSTRACTThe legal doctrines of reasonable use and correlative rights are the recognized standards for resolving legal conflicts between interfering agricultural ground‐water users in Arkansas. Assuring that an adequate saturated thickness exists for all interfering users throughout the ground‐water withdrawal season provides water users with a degree of protection from both a successful litigious charge of “unreasonable use” and a mandated curtailment of ground‐water withdrawal in a droughty season.The feasibility of maintaining a “target” saturated thickness and water‐table elevation by implementing a district‐wide sustained ground‐water withdrawal strategy has been previously demonstrated. Several models have been reported which create the spatially distributed sustained‐yield withdrawal strategies that will maintain those target levels. The development of satisfactory strategies requires knowledge of the minimum acceptable springtime saturated thickness for critical parts of the management district. This information can be gained through the iterative use of a dynamic ground‐water simulation model. In the iterative procedure, initial (springtime) saturated thickness is assumed. The change in saturated thickness resulting from withdrawals during the irrigation season is compared with an acceptability criterion. The assumed springtime saturated thickness is varied until the criterion is satisfied. The result is the minimum springtime saturated thickness needed for ground‐water users in a particular cell to achieve: (1) a measure of year‐round protection from successful litigation charging unreasonable use, and (2) some assurance that they will not need to curtail or limit ground‐water withdrawals during a droughty season.This procedure was applied to a 3‐mile by 3‐mile (5‐km by 5‐km) cell in the Arkansas Grand Prairie, an important rice‐ and soybean‐producing area. The results indicate that a minimum of 13 feet (4 m) of saturated thickness are desirable for the center of the cell to provide for a droughty season.
Microbial Biomass, Activity, and Community Structure in Subsurface Soils
Authors: Federle Thomas W. , Dobbins Durell C. , Thornton‐Manning Janice R. , Jones Daniel D. 
Published: March 2006

ABSTRACTMicrobial biomass, community structure and activity were determined in the subsurface horizons of four contrasting soil types common to Alabama. Biomass and community structure were determined by analyzing the fatty acids of the extractable phospholipids. Activity was estimated by measuring the rate of enzymatic hydrolysis of fluorescein diacetate (FDA). In all four soils, biomass and activity declined with increasing depth; however, the magnitude and pattern of this decline varied as a function of soil type. Biomass concentrations in the lower Ap horizon ranged from 8.2 to 18.0 nmoles phospholipid/g dry wt soil. In the deepest subsoil horizons, the range was 0.0085 to 0.059 nmoles phospholipid/g dry wt soil. The rate of FDA hydrolysis was highly correlated with biomass (r=0.90). Polyenoic fatty acids, which are present only in cukaryotic microorganisms, were found in all horizons; however, their relative abundance differed as a function of soil type. Stepwise regression analysis revealed that soil characteristics could explain 89 and 82% of the variation in biomass and activity, respectively. The results indicated that the vertical distribution of microorganisms in a soil profile differs greatly as a function of soil type. Hence, soil type may be an important determinant as to whether potential ground‐water pollutants are biodegraded as they pass through the unsaturated zone of a soil profile.
Ground‐Water Problems in the Mesozoic Pax Mountain Fault Zone
Authors: Snipes David S. , Manoogian Peter R. , Davis Michael W. , Burnett Laura L. , Wylie Jerry A. , Heaton Steven B. 
Published: March 2006

ABSTRACTMore than 100 steeply dipping or vertical Mesozoic fault zones, which cut across Paleozoic igneous and metamorphic rocks, have been reported in the Piedmont and Appalachians of the Carolinas. The present investigation deals with the hydrological problems encountered in exploring for ground water in the Pax Mountain Fault zone. This is the largest known Mesozoic fault in the Carolinas, having a length of more than 75 km and attaining a width of 1 km in places. Subsurface studies of seven wells, which were drilled along the axis of Pax Mountain, South Carolina, show that the composition of the fault rocks is much more complicated than was known heretofore. These rocks consist of angular particles of quartz and feldspar fault breccia enclosed in a kaolinitic clay gouge. They vary greatly in degrees of consolidation and permeability, and these variations were the cause of some serious ground‐water problems. Two wells were dry holes because the intergranular spaces of the breccia were clogged with clay and also because most of the joints were filled with secondary minerals. Three wells, which were drilled in more permeable, but poorly consolidated fault rocks, caved in at a depth of about 80 m just when they had encountered large volumes of water. Two of the seven wells produce potable water, but chemical analyses of the ground water showed that their turbidity values were 6.0 t.u. and 2.0 t.u., which exceed the limit of 1.0 recommended by the South Carolina Department of Health and Environmental Control.
Dependence of Effective Porosity on Fracture Continuity in Fractured Media
Authors: Gordon Matthew J. 
Published: March 2006

ABSTRACTFractured geologic media are typically considered to behave as equivalent porous‐media continua for the purposes of hydrologic testing and modeling. The equivalent‐continuum effective porosity of a fractured medium is frequently measured using tracer tests performed over distances that are small relative to the scale of interest in hydrologic and transport modeling. The larger‐scale value of effective porosity can differ from the smaller‐scale measured value by several orders of magnitude, depending in part on the relative degree of fracture continuity between inflow and outflow zones at the different scales. Based on the results of a simplified numerical modeling study for fractured media with poor continuity at the location and scale of interest, flow is dominated by the intact rock matrix, resulting in a higher effective porosity. For fractured media with uninterrupted fracture continuity at the location and scale of interest, the effective porosity may be substantially lower due to the fracture‐dominated nature of the flow.
Geochemical Investigations of Three Tropical Karst Drainage Basins in Puerto Rico
Authors: Troester Joseph W. , White William B. 
Published: March 2006

ABSTRACTThe carbonate chemistry was measured at various springs and surface stations along three river basins in the northwestern karst belt of Puerto Rico. Most surface waters are supersaturated with respect to calcite, and carbon dioxide pressures are close to atmospheric value. Spring waters have higher CO2 pressures but also tend to be supersaturated. Water hardnesses are not dramatically greater than those observed in temperate climate karst.
Strata‐Movement Concepts and the Hydrogeological Impact of Underground Coal Mining
Authors: Booth Colin J. 
Published: March 2006

ABSTRACTA review of mining‐engineering concepts and studies in mine hydrology suggests a conceptual model linking the strata deformation, hydraulic property changes, and ground‐water impacts due to underground coal mining. The pressure‐arch deformation pattern about a small opening creates a local zone of increased permeabilities and dewatering in the seam and immediate roof, but should not hydraulically affect shallower aquifers. Networks of supported headings, rooms, and pillars intensely drain lower aquifers but only slightly affect higher strata except in areas of naturally high permeability. Longwall mining causes extensive, high‐reaching, well‐defined zones of stress, fracturing, and hydraulic impact, the maximum permeability increases being in the tensile zones immediately above the panel and at the sides of the subsidence trough. In shallow aquifers, permeabilities and ground‐water velocities increase, and hydraulic gradients decline independently of mine drainage.A study of a deep coal mine in the Appalachian Plateau, Pennsylvania indicated: probable hydraulic connections between the mine and shallow aquifers in a principal valley area; no obvious response of water levels in shallow aquifers to undermining by supported headings; and rapid, considerable declines in such water levels in response to nearby longwall mining. These results are consistent with the conceptual model.