bluuebunny/crossref_metadata_2025_split huggingface dataset:
Monitoring Strategies at Phreatic Wellfields: A 3D Travel Time Approach
Authors: Peter Broers Hans , Van Geer Frans C. 
Published: August 2010

AbstractGround water quality networks for monitoring phreatic drinking water wellfields are generally established for two main purposes: (1) the short‐term safeguarding of public water supply and (2) signaling and predicting future quality changes in the extracted ground water. Six monitoring configurations with different well locations and different screen depths and lengths were evaluated using a numerical model of the 3D ground water flow toward a partially penetrating pumping well in a phreatic aquifer. Travel times and breakthrough curves for observation and pumping wells were used to judge the effectiveness of different design configurations for three monitoring objectives: (1) early warning; (2) prediction of future quality changes; and (3) evaluation of protection measures inside a protection zone. Effectiveness was tested for scenarios with advective transport, first‐order degradation, and linear sorption. It is shown that the location and especially the depth of the observation wells should be carefully chosen, taking into account the residence time from the surface to the observation well, the residual transit times to the extraction well, and the transformation and retardation rates. Shallow monitoring was most functional for a variety of objectives and conditions. The larger the degradation rates or retardation, the shallower should the monitoring be for effective early warning and prediction of future ground water quality. The general approach followed in the current study is applicable for many geohydrological situations, tuning specific monitoring objectives with residence times and residual transit times obtained from a site‐specific ground water flow model.
Optimizing Remediation of an Unconfined Aquifer Using a Hybrid Algorithm
Authors: Hsiao Chin‐Tsai , Chang Liang‐Cheng 
Published: August 2010

AbstractWe present a novel hybrid algorithm, integrating a genetic algorithm (GA) and constrained differential dynamic programming (CDDP), to achieve remediation planning for an unconfined aquifer. The objective function includes both fixed and dynamic operation costs. GA determines the primary structure of the proposed algorithm, and a chromosome therein implemented by a series of binary digits represents a potential network design. The time‐varying optimal operation cost associated with the network design is computed by the CDDP, in which is embedded a numerical transport model. Several computational approaches, including a chromosome bookkeeping procedure, are implemented to alleviate computational loading. Additionally, case studies that involve fixed and time‐varying operating costs for confined and unconfined aquifers, respectively, are discussed to elucidate the effectiveness of the proposed algorithm. Simulation results indicate that the fixed costs markedly affect the optimal design, including the number and locations of the wells. Furthermore, the solution obtained using the confined approximation for an unconfined aquifer may be infeasible, as determined by an unconfined simulation.
Site Characterization in Densely Fractured Dolomite: Comparison of Methods
Authors: Muldoon Maureen , Bradbury Ken R. 
Published: August 2010

AbstractOne of the challenges in characterizing fractured‐rock aquifers is determining whether the equivalent porous medium approximation is valid at the problem scale. Detailed hydrogeologic characterization completed at a small study site in a densely fractured dolomite has yielded an extensive data set that was used to evaluate the utility of the continuum and discrete‐fracture approaches to aquifer characterization. There are two near‐vertical sets of fractures at the site; near‐horizontal bedding‐plane partings constitute a third fracture set. Eighteen boreholes, including five coreholes, were drilled to a depth of ∼10.6 m. Borehole geophysical logs revealed several laterally extensive horizontal fractures and dissolution zones. Flowmeter and short‐interval packer testing identified which of these features were hydraulically important. A monitoring system, consisting of short‐interval piezometers and multilevel samplers, was designed to monitor four horizontal fractures and two dissolution zones. The resulting network consisted of >70 sampling points and allowed detailed monitoring of head distributions in three dimensions.Comparison of distributions of hydraulic head and hydraulic conductivity determined by these two approaches suggests that even in a densely fractured‐carbonate aquifer, a characterization approach using traditional long‐interval monitoring wells is inadequate to characterize ground water movement for the purposes of regulatory monitoring or site remediation. In addition, traditional multiwell pumping tests yield an average or bulk hydraulic conductivity that is not adequate for predicting rapid ground water travel times through the fracture network, and the pumping test response does not appear to be an adequate tool for assessing whether the porous medium approximation is valid.
A Simple Method for Calculating Growth Rates of Petroleum Hydrocarbon Plumes
Authors: Bekins Barbara A. , Cozzarelli Isabelle M. , Curtis Gary P. 
Published: August 2010

AbstractConsumption of aquifer Fe(III) during biodegradation of ground water contaminants may result in expansion of a contaminant plume, changing the outlook for monitored natural attenuation. Data from two research sites contaminated with petroleum hydrocarbons show that toluene and xylenes degrade under methanogenic conditions, but the benzene and ethylbenzene plumes grow as aquifer Fe(III) supplies are depleted. By considering a one‐dimensional reaction front in a constant unidirectional flow field, it is possible to derive a simple expression for the growth rate of a benzene plume. The method balances the mass flux of benzene with the Fe(III) content of the aquifer, assuming that the biodegradation reaction is instantaneous. The resulting expression shows that the benzene front migration is retarded relative to the ground water velocity by a factor that depends on the concentrations of hydrocarbon and bioavailable Fe(III). The method provides good agreement with benzene plumes at a crude oil study site in Minnesota and a gasoline site in South Carolina. Compared to the South Carolina site, the Minnesota site has 25% higher benzene flux but eight times the Fe(III), leading to about one‐sixth the expansion rate. Although it was developed for benzene, toluene, ethylbenzene, and xylenes, the growth‐rate estimation method may have applications to contaminant plumes from other persistent contaminant sources.
An Improved Straight‐Line Fitting Method for Analyzing Pumping Test Recovery Data
Authors: Zheng Li , Guo Jian‐Qing , Lei Yuping 
Published: August 2010

Abstract Theis (1935) derived an exact solution for the residual drawdown in a well after the cessation of a pumping test by summing two drawdowns: one (s1), caused by imaginary continuation of the original pumping and the other (s2), due to an imaginary injection at the same constant rate. We approximated the Theis solution to obtain a simple linear relation for determining the transmissivity and storage coefficient from recovery data. Unlike other existing straight‐line fitting methods, in our method, we applied different approximations to the well functions in the solutions of s1 and s2. We used the well‐known Cooper‐Jacob approximation for s1, truncating the expansion of the well function in s2 to its first three terms. For the same level of truncation errors, while the Cooper‐Jacob approximation requires the argument u1≤ 0.01, the second approximation requires the argument u2≤ 0.2, thus dramatically improving the utility of short‐term recovery data. Application of our method requires only recovery data from a single observation well and no knowledge of the drawdown at the moment of pumping cessation.
An Algorithm for the Estimation of NAPL Saturation and Composition from Typical Soil Chemical Analyses
Authors: Mariner Paul E. , Jin Minquan , Jackson Richard E. 
Published: August 2010

AbstractAn algorithm is presented that allows estimation of the saturation and composition of a single of multi‐component NAPL within a core sample. These estimates are possible because, in addition to distributing the organic chemicals between aqueous, sorbed, air, and NAPL phases according to traditionalpartitioning equations, the algorithm incorporates equations for the conservation of mass and volume. A unique solution is obtained by solvihg the set of nonlinear equations implicitly. The algorithm is built into a code called NAPLANAL, which is tested and applied to actual core samples collected in the field.
In situ mesocosms: Denitrification in the Elk Valley aquifer
Authors: Korom Scott F. , Schlag Allen J. , Schuh William M. , Kammer Schlag Alison 
Published: August 2010

AbstractLarge stainless steel chambers were designed, constructed, and installed to make in situ mesocosms (ISMs) of aquifer sediments. The advantages of the ISMs over in situ microcosms, their smaller counterparts, are that ISMs may be sampled for longer times with larger sampling volumes. The former advantage makes ISMs a good tool to study the natural attenuation of contaminants with slow degradation rates. The latter advantage allows samples to be large enough that they may be analyzed for contaminants and reaction products, plus major ions normally associated with “complete” water analyses. Having such a large suite of analytes provides insights into associated mineral saturation conditions and possible reaction pathways that may not be readily apparent. As an example of their utility, a tracer test was done in a pair of ISMs to test our hypothesis that S(−I) in pyrite was a major electron donor for denitrification in the Elk Valley aquifer in eastern North Dakota. During the 9‐month experiment, sediment data, ground water saturation indices, and trends in the geochemical evolution of the bromide tracer, calcium, inorganic carbon, magnesium, nitrate, and sulfate concentrations indicate that 58% of the denitrification was caused by S(−I) as the electron donor. These data also suggest that ferrous iron and organic carbon may have served as electron donors for the denitrification. The apparent zero‐order denitrification rate was 16 mM/d (r2= 0.93) with a δ15N isotopic enrichment factor of −20.4‰ (r2= 0.998).
Passive diffusion ground water samplers at a site with heterogeneous hydrostratigraphy: Pilot study results
Authors: Divine Craig E. , Madsen Laura L. , Andrews Scott D. , Santangelo‐Dreiling Theresa 
Published: August 2010

AbstractUse of passive diffusion (PD) ground water samplers has significantly increased in recent years because significant cost savings may be realized, primarily because sampling time is reduced and minimal investigation‐derived waste (IDW) is generated. However, PD samplers measure water quality over a relatively discrete interval, while traditional purge‐and‐sample methods are most influenced by the water quality in more permeable zones across the well screen. Consequently, these two sampling methods may potentially yield distinctly differing concentration measurements for a specific well if significant contaminant stratification and geologic heterogeneity exist. A large body of purge‐and‐sample historical monitoring data exist for the study site, and results from potential future full‐scale PD sampler application must be interpretable and comparable in the context of these historical data to be useful for evaluating achievement of long‐term site remediation objectives. Therefore, a pilot study was conducted to assess potential for PD samplers for monitoring chlorinated volatile organic compounds (VOCs) in ground water. PD samplers were installed in a select group of indicator wells, and their performance was compared to results from both purge‐and‐sample and low‐flow (LF; another discrete interval–type technique) methods. At several wells, multiple PD samplers were installed across the well screen interval to evaluate potential contaminant stratification. At one well, contaminant stratification was particularly significant: concentrations of total VOCs measured by two PD samplers installed ∼0.6 m (2 feet) apart differed by an order of magnitude. PD sampler and LF data interpreted in tandem with purge‐and‐sample data provide additional information, suggesting that contamination is located primarily in the more permeable zones at the study well locations. Additionally, low concentrations of some VOCs were measured in some PD and LF samples but not in the corresponding purge‐and‐bail samples. The results of this study underscore the importance of pilot studies and careful program design and regulatory agreement before implementing PD samplers (or any alternative sampling method) in a long‐term monitoring program, especially at sites with heterogeneous hydrostratigraphy.
LNAPL in fine‐grained soils: Conceptualization of saturation, distribution, recovery, and their modeling
Authors: Adamski Mark , Kremesec Victor , Kolhatkar Ravi , Pearson Chris , Rowan Beth 
Published: August 2010

AbstractA simple conceptual model is presented that leads to a quantitative description of the behavior of light non–aqueous phase liquid (LNAPL) in fine‐grained soil (FGS). The occurrence of large (15 feet) (4.6 m) LNAPL accumulations in observation wells in FGS and of LNAPL located below the water table is explained by macropore theory and capillarity of the FGS. Using soil capillary data, fluid property data, and a simple spreadsheet model, the LNAPL saturation in a soil profile and LNAPL recovery were predicted for a field study site. The predicted LNAPL distribution, saturation, and recovery matched the field observations and actual LNAPL recovery. Measured LNAPL saturations were <2%, while model‐predicted values were <3%. The model predicted recovery of ∼530 gallons (2009 L). After 1.5 years of continuous operation, a three‐phase, high‐vacuum extraction system recovered 150 gallons (568 L) of LNAPL. Application of a model that assumes homogeneity of the soil that is heterogeneous at a small scale may seem to be a misapplication; however, conceptualizing the model domain at a sufficiently large scale (3 to 6 feet; 0.9 to 1.8 m) allows for the FGS to be viewed as a homogeneous medium with small effective porosity.
Aquifer prioritization for ambient ground water monitoring
Authors: Bedessem Marjorie E. , Casey Brenda , Frederick Kevin , Nibbelink Nathan 
Published: August 2010

AbstractAmbient ground water monitoring programs have been developed by more than half of the states in the United States in order to determine baseline ground water quality and monitor long‐term water quality trends. States have focused their resources in many cases by prioritizing certain basins (ground water or watershed), major aquifers, or sensitive areas. This study focuses on development of an aquifer prioritization approach, specifically for the state of Wyoming, that considers both the complex geology and the variety of potential contaminant sources. The focus of ground water management in Wyoming is currently on protection, with particular attention to shallow aquifers most susceptible to water quality degradation from human activities. Aquifers within the state are evaluated with respect to current water use, sensitivity based upon a modification of the DRASTIC model, and potential for surface contamination from known land uses. High‐priority aquifers are designated as those aquifers that serve as drinking water sources and are most susceptible to point and non–point source pollution. Using geographic information systems, ratings are then compiled to provide a sophisticated aquifer prioritization mapping system specifically developed for targeting ambient ground water monitoring efforts.
Strategies for Designing Ground Water Monitoring Networks at Waste Storage Facilities with Multiple Source Areas
Authors: Hudak Paul F. 
Published: August 2010

AbstractThe objective of this study was to devise and evaluate methods for configuring ground water monitoring networks at waste storage facilities with multiple contaminant source areas. These methods allocate monitoring wells to compliance boundaries lagged hydraulically downgradient of potential contaminant sources such as landfills and lagoons. Alternative design methods separately monitor or integrate potential sources and space wells uniformly in the direction (1) along the compliance boundary or (2) perpendicular to ground water flow. In an application of four design methods, a computer model simulated potential contaminant releases distributed throughout multiple sources with a combined area of ∼5000 m2, computing the detection capability of each monitoring configuration. A network without monitoring redundancy in overlapping source areas, with wells spaced uniformly perpendicular to ground water flow, outperformed alternative layouts. Perpendicular networks were also more robust to uncertain model parameters. For a base case, the most efficient network of 10 wells detected 99.4% of >5000 simulated contaminant releases, whereas alternative networks detected from 85.4% to 96.1% of releases.
Fracture Of Endodontic Root Canal Instruments
Authors: Brockhurst Peter 
Published: August 2010

ABSTRACTThe purpose of this paper is to identify the mechanisms of breakage for endodontic instruments, and to propose procedures to avoid its occurrence. The forces that can be exerted by the dentist are greater than the strength of many instruments. The manner of transfer of these forces to the canal is often uncertain, so that inadvertent excessive stresses may be applied to the weaker distal (apical) end. Instruments may also break due to fatigue or the weakening effects of defects produced during manufacturing, or during use. The behaviour of instruments made from nickel‐titanium (NiTi) alloys carries some uncertainty at the present time. Procedures to minimise fracture are proposed.
CULTURE OF WHITE SHRIMP (Penaeus setiferus, Linnaeus) IN STATIC WATER PONDS1
Authors: Elam Larry L. , Green A. W. 
Published: August 2010

ABSTRACTPond experiments with white shrimp (Penaeus setiferus. Linnaeus) were conducted at the Marine Fisheries Research Station, Palacios, Texas during 1973. Two 0.4 ha ponds were used as nursery ponds. Ten ponds (six 0.2 and four 0.1 ha) were used as grow‐out ponds where the effects of stocking rate, pond size, and feed type on growth rates were studied. Shrimp in the grow‐out ponds were sampled twice monthly and fed two different types of feed at 7.5% of the total weight of the shrimp, assuming 10% handling and stocking mortality. Feed types and pond sizes significantly affected shrimp growth while stocking density did not. Food conversion rates ranged from 1.8 to 2.3. Production ranged from 224 to 667.5 kg per ha. Temperatures ranged from 19.4 to 31.9 C., while salinities ranged from 6.0 to 17.8 ppt.
GAFFKEMIA IN CALIFORNIA SPINY LOBSTERS
Authors: Steenbergen J. F. , Schapiro H. C. 
Published: August 2010

ABSTRACTGaffkemia, a systemic infection of Atlantic lobsters (Homarus sp.) by Pediococcus homari (formerly Gaffkya homari), can be initiated by injection of virulent strains of the bacterium into the California spiny lobster (Panulirus interruptus). At 17 C, an LD50 of 103 bacteria per ml hemolymph was observed. The number of hemocytes drop and the clotting times are extended as the disease progresses. The demonstration of the disease in the California spiny lobster is particularly significant since we have isolated P. homari from California estuarine waters.
ACTIVE IMMUNITY TO GAFFKEMIA IN LOBSTERS
Authors: Schapiro H. C. , Steenbergen J. G. 
Published: August 2010

ABSTRACTThe California spiny lobster (Panulirus interruptus) may be immunized by injection with an avirulent strain of Pediococcus homari (formerly Gaffkya homari). This immunization protects the animals against a later challenge with 100 x LD50 virulent bacteria. The mechanism of this immunization is being investigated. This is the first report of acquired immunity to P. homari in a susceptible species. It is also the first use of a live attenuated strain of a pathogen to immunize a decapod crustacean.
THE EFFECTS OF FEEDING FREQUENCY AND SPACE ON THE GROWTH OF THE AMERICAN LOBSTER, Homarus americanus1
Authors: Shleser Robert A. 
Published: August 2010

ABSTRACTThe lobster is cannibalistic; animals which have been grown beyond the juvenile stages must be separated and held individually. It is essential to determine the effects of habitat configuration and spatial limitation on the growth rate of individually held lobsters.As a first step in determining optimum configuration for holding lobster, rectangular, square and circular environments are examined. Configuration has no significant effect on growth. However, significant differences in growth occur between smaller and larger habitats.Lobsters which are held individually must be individually fed. In order to obtain the optimal growth rate at the lowest cost, we have examined the effect of feeding lobsters an amount of food which slightly exceeds the daily femand at greater than one day intervals. An equal oprtion of food was given at 1,2, and 3‐day intervals. The results of these studies indicated that at least daily feeding was necessary for juvenile lobsters.
MARINE TURTLE CULTURE ‐ AN OVERVIEW
Authors: Hendrickson J. R. 
Published: August 2010

ABSTRACTThe general background and present status of this new branch of maricultural science are briefly surveyed, with a description of the only large industrial complex now in existence. Progress in turtle mariculture to the present is summarized and some outstanding scientific problems requiring solution are delineated. The new industry's interface with problems of conservation of wild stocks is discussed.
ECTOCOMMENSALS AND PARASITES OF SHRIMP FROM TEXAS REARING PONDS1
Authors: Johnson S. K. 
Published: August 2010

ABSTRACTFive species of penaeid and one palemonid shrimp from Texas coastal rearing ponds investigated during 1972–73 were found to host ectocommensals and parasites. New ectocommensal relationships and the nature of ectocommensal associations are discussed.
SOME MARINE MICROORGANISMS RELATED TO SHRIMP DISEASES
Authors: Laramore Charles R. , Hirnon Yosuke , Persyn Harvey , Barkate John A. 
Published: August 2010

ABSTRACTA filamentous bacterium pathogenic for postlarval shrimp has been observed, isolated and used in the reproduction of the disease. A marine protozoan and a fungus have also been observed in hatchery conditions and are responsible for high mortalities.
INDUCED MATURATION AND SPAWNING OF MARINE FISH AT THE SOUTHWEST FISHERIES CENTER LA JOLLA, CALIFORNIA
Authors: Lasker Reuben 
Published: August 2010

ABSTRACTTechnical details are given for spawning the following fish under controlled laboratory conditions: the northern anchovy (Engraulis mordax), Pacific mackerel (Scomber japonicus), croaker (Bairdiella icistia), and striped bass (Morone saxatilis).
DENITRIFICATION IN WATER RE‐USE SYSTEMS1
Authors: Meade T. L. , Kenworthy B. R. 
Published: August 2010

ABSTRACTHigh density fish culture in water re‐use systems results in a rapid buildup of nitrate as a result of nitrification. The LD50 of nitrate for salmonids in both fresh and seawater is relatively high, but levels considered safe are much lower. In practice safe levels of nitrate are maintained by dilution, which restricts the percent re‐use possible, or by denitrification. The later will theoretically permit 100% re‐use, or it can be used to provide an effluent stream meeting presently established standards for discharging waste water. Problems involved in the activation of a flexiring packed, denitrification column operating on a side stream from a salmonid culture system are discussed.