bluuebunny/crossref_metadata_2025_split huggingface dataset:
Specific Gravity
Authors: Rasmussen Todd 
Published: July 2005

Abstract
The density of water and other materials varies with temperature as well as with the amount of dissolved and suspended matter within them. The specific gravity is the observed density of a material divided by a reference density, which is usually taken to be water at its maximum density, i.e., 1 kg/L. Thus, variations in the specific gravity are a direct measure of the variation in density. The specific weight of a material equals the product of its density and the gravitational constant. The specific gravity is important because it is needed to correct for the water density in wells to determine the freshwater head. Well construction also relies on the specific gravity of drilling muds to prevent the collapse of borehole walls in unconsolidated media.
Treatment for Nitrates in Groundwater
Authors: Loo Walter W. , Wen Jason J. 
Published: July 2005

Abstract
Common sources of nitrogen in the soil are fertilizers, livestock waste, and septic systems. Excess nitrate in the soil is most often found in rural and agricultural areas. Nitrate travels easily through the soil, carried by rain or irrigation water into groundwater supplies. The distribution of nitrate contamination in the United State is widespread. It is the largest amount of pollutant released into the environment. Infants under six months of age are susceptible to nitrate poisoning. The U.S. Environ‐mental Protection Agency (EPA) has established the maximum contaminant level (MCL) for nitrate at 10 milligrams per liter (mg/L). In addition, EPA has established an MCL for nitrite at 1 mg/L.
Biodenitrification treatment will probably be a very common technology used to come into compliance with the nitrate/nitrite regulation.
Reverse osmosis (RO) systems can often reduce nitrate from well water.

The following is a list of advanced studies for in‐situ groundwater treatment containing nitrate:

Mettallic ion treatment

Wetland treatment

In‐situ iron filing curtain treatment

In‐situ electrokinetic treatment.
Well Maintenance
Authors: Smith Stuart A. 
Published: July 2005

Abstract
Well maintenance consists of two overall problem‐preventing scopes of work: predictive and preventive maintenance (together comprising PM). Predictive maintenance involves tasks such as monitoring water quality, power, and other indicator data to detect evidence of deterioration prior to a fault and making necessary repairs. Preventive maintenance includes tasks such as maintaining lubrication, replacing components, and preventive well treatments conducted prior to deterioration of performance. By contrast, reactive maintenance repairs deteriorated components and performance conditions.
Well Screens
Authors: Williams Dennis E. 
Published: July 2005

AbstractThe well screen is the component of a well which provides an opening through which water enters the well casing from the aquifer, as well as stabilizing the material in the “near‐well zone” and preventing it from entering the well. Screens may be constructed with a variety of different materials and designs, as appropriate to the design of the well and its aquifers. Typical types of screen are:Horizontal louver screens, a pipe‐based well screen with punch‐formed downward facing louver‐shaped openings.Continuous wire wrap screens, manufactured by wrapping shaped wire around an internal array of rods.Bridge slot screens, produced by rolling and welding perforated steel plates or sheets.Machine‐slotted (milled) screens, manufactured by milling casing with axially oriented precision cutters.Well casing perforated in place with a mills knife or a hydraulic perforator lowered down the cased borehole.Different screens may by evaluated for a particular well design based on the material, size of perforations, percent of open area, cost, susceptibility to corrosion, and collapse strength. A properly designed screen allows sand‐free water to flow into the well with a minimum drawdown.
Radial Wells
Authors: Williams Dennis E. 
Published: July 2005

Abstract
Radial wells are wells whose screens have a radial or horizontal component. Types of radial wells include collector wells, horizontally directionally drilled wells, and slant or horizontal wells. Collector wells are the most common type of radial wells. The basic components of collector well design are a vertical shaft with horizontal screen laterals. These laterals typically extend up to tens of hundreds of meters and vary in number based on aquifer characteristics.
Radial wells take advantage of natural filtration through aquifer materials, which reduces treatment costs. Maintenance is reduced as the longer horizontal screens reduce water velocity, thereby reducing well head losses and clogging. Furthermore, lateral well screens are able to exploit the maximum saturated thickness of shallow aquifers. For example, up to 500 m of horizontal well screen can be developed in formations that would accommodate only 20 m of vertical well screen. Horizontal directionally drilled (HDD) wells, which are widely used in the oil and gas industry, are now being developed for groundwater applications.
Radial wells are used in applications such as municipal production wells, dewatering operations, desalination plant intake systems, and inducing surface water infiltration for groundwater recharge.
Horizontal Wells in Groundwater Remediation
Authors: Jacobs James A. , Vance David B. 
Published: July 2005

Abstract
Horizontal wells have been used in an increasing number of remediation projects. In addition to chemical and biological reactive barriers, horizontal borings can be used for groundwater extraction and control, air sparging, bioremediation, groundwater injection, for vadose zone soil vapor extraction or bioventing systems, and free product recovery. Although, in areas where there is a great deal of fluctuation in the groundwater table, use for free product recovery can be problematic.
Horizontal well technology was first used in the late 1920s by the petroleum industry to increase oil reservoir thickness per well and greatly increase oil production. In the 1970s, the technology was applied by utility companies to cross rivers and other natural or manmade barriers such as highways. The use of horizontal drilling technology for environmental applications began in the late 1980s and has escalated ever since.
The Environmental Impact of Iron in Groundwater
Authors: Vance David B. , Jacobs James A. 
Published: July 2005

Abstract

Iron is a common constituent in soils and groundwater. It readily participates in subsurface redox reactions and under some conditions can cause taste, odor, and flow problems with drinking water wells and can precipitate and plug up
in situ
groundwater remediation systems. In other geochemical conditions, iron can aid in the remediation of certain chemicals undergoing chemical transformations associated with Redox reactions. Ferrous iron is used as a terminal electron acceptor for anaerobic bioremediation processes that play a dominant role in the natural attenuation process.
Dating Groundwaters with Tritium
Authors: Testa Stephen M. 
Published: July 2005

Abstract

Tritium (
3
H) is one of the most common radioisotopes used to identify the presence of modern groundwater recharge and estimate apparent groundwater ages (1). Tritium, a short‐lived radioactive isotope of the element hydrogen, has one proton and two neutrons. Tritium emits only a very weak beta particle and has a half‐life of 12.43 years. Although tritium can occur as a gas, its most common form is in water because, like nonradioactive hydrogen, radioactive tritium readily reacts with oxygen to form water, which allows groundwater to be dated. As tritium replaces one of the stable hydrogens in the water molecule, (H
2
), it is referred to as the molecule HTO, or tritiated water (T
2
0). Similarly to water, tritium is colorless and odorless.

Tritium is produced naturally in both the atmosphere and hydrosphere of the earth when cosmic rays strike air molecules, notably by the interaction of
14
N with cosmic ray neutrons.
Groundwater and Mercury: Chemical Behavior and Treatment
Authors: Jacobs James A. , Johnson Silvia 
Published: July 2005

Abstract
Mercury is a naturally occurring element named after the planet Mercury. It cycles in the environment as a result of both natural and anthropogenic activities. Mercury appears as elemental vapor mercury in the atmosphere and as inorganic mercury salts and organic mercury in water, plants, and land. Mercury enters the environment from natural sources such as volcanoes and the weathering of rocks. Mercury is also a by‐product of gold and zinc mining. The environment is impacted by the use of mercury in mining operations and other industries and from the burning of fossil fuels at coal‐fired power plants and smelting metals.
Groundwater and Uranium: Chemical Behavior and Treatment
Authors: Jacobs James A. , Smalling Ricardo 
Published: July 2005

Abstract
The element uranium, symbol U, is a chemically reactive radioactive metallic element. It is the main fuel used in nuclear reactors. Uranium has atomic number 92, which places it in the actinide series of the periodic table. The German chemist Martin Heinrich Klaproth discovered uranium in 1789 in pitchblende. He named it after the planet Uranus. Uranium was first isolated in the metallic state in 1841and the radioactive properties were first demonstrated in 1896 by the French physicist Antoine Henri Becquerel (1).
High
p
H
Groundwater— The Effect of The Dissolution of Hardened Cement Pastes
Authors: Shi Caijun , Spence Roger 
Published: July 2005

Abstract
The pH value of the hardened portland cement and concrete ranges from over 12.5 to values as high as 13.5, due to the presence of alkalis in cement. Partial replacement of portland cement with supplementary cementing materials such as coal fly ash, blast furnace slag, silica fume, and natural pozzolan can decrease the pH value depending on the characteristics and dosage of the material used.
The dissolution and leaching of hydration products of cement can affect the pH value of groundwater. Increased pH of groundwater can be expected around the surface of concrete but is not expected to penetrate far into the groundwater matrix, because the transport rate from the concrete is low. The width of the affected zone is mainly controlled by the rate of flow of the groundwater around the surface of the concrete.
Water/Rocks Interaction
Authors: Teng Henry 
Published: July 2005

AbstractWater–rock interactions encompass primarily three types of reactions, namely adsorption, dissolution, and precipitation, that take place at the mineral‐fluid interfaces. Adsorption reactions occur because of the formation of surface complexes and can be described by a chemical and an electrostatic interaction between adsorbates and surface species on minerals. Although the chemical (intrinsic) reaction of adsorption can be evaluated by equilibrium thermodynamics, theories of electrochemistry, such as the diffuse double layer model, have to be invoked to encounter the coulombic interactions. Dissolution and precipitation are solution saturation‐driven reactions. The direction of dissolution‐precipitation reactions can be accessed by the relative level of solute chemical potential in solid and liquid phases. Whereas a higher potential in solid phase leads to dissolution, a reversed situation results in precipitation. Precipitation cannot be regarded as a mirror reaction of dissolution because the former is a two‐step process, nucleation and growth, and each step has its unique thermodynamic and kinetic characteristics. Kinetics of dissolution/precipitation may be controlled by the rate of the actual interfacial chemical reactions or the transport process that moves reactants and products. It is general agreed that most mineral‐water interactions are surface reaction controlled processes.
Process Limitations of
In Situ
Bioremediation of Groundwater
Authors: Vance David B. , Jacobs James A. 
Published: July 2005

Abstract

The history of groundwater remediation of hydrocarbon‐related compounds illustrates a variety of technologies and methods used over time. Starting in the late 1970s, and continuing to the present,
in situ
bioremediation has been a cost effective adaptation to the process for both petroleum hydrocarbons and synthetically produced chlorinated solvents and other xenobiotic compounds such as MTBE.
Modeling ofDNAPLMigration in Saturated Porous Media
Authors: Mohan Kumar M. S. , Mathew Mini 
Published: July 2005

AbstractNonaqueous phase liquids (NAPLs) such as the homogenate hydrocarbons used in dry cleaning and industrial degreasing (DNAPLs), hydrocarbon fuels and aromatic solvents (LNAPLs), and neutrally buoyant coal tars and creosotes are widespread in our environment. Because of their low solubility, NAPL sources can emit toxic contaminants to groundwater for many decades if not managed properly. The migration of dense nonaqueous phase liquids (DNAPLs), which are immiscible with water, through the saturated porous media is an important part of contaminant hydrology and in petroleum engineering. Protection and remediation of groundwater resources require an understanding of processes that affect the fate and transport of such contaminants in the subsurface environment. To implement appropriate remedial schemes in the contaminated area, it is necessary to evaluate the extent of the contaminated area. This information can be obtained by extensive field investigation, which generally is expensive and time consuming. Field investigation can be reduced or made more cost effective, if the migration pattern of the DNAPLs can be evaluated by using numerical models accurately.
Groundwater Vulnerability to Pesticides: Statistical Approaches
Authors: Gurdak Jason J. , McCray John E. 
Published: July 2005

AbstractGroundwater vulnerability to pesticides is the potential for contamination of groundwater by pesticides from a nonpoint source or aerially distributed point sources. Due to widespread pesticide use and detection in groundwater, assessments that evaluate and estimate pesticide vulnerability have increasingly proven valuable during decisions regarding groundwater management, conservation, and remediation because of the significant costs of such actions. To predict groundwater vulnerability and understand factors that affect the transport of pesticides to groundwater resources, a variety of approaches have been developed that are broadly classified into three general categories: (1) overlay and index, (2) statistically based, and (3) process based. Often the selection of an appropriate approach for assessing groundwater vulnerability to pesticides is determined by the type and scale of the problem and by the available resources. This article provides an overview of the approaches and methods of evaluation for assessing groundwater vulnerability to pesticides.
Pharmaceuticals, Hormones, and Other Organic Wastewater Contaminants in
U
.
S
. Streams
Authors: Buxton Herbert T. , Kolpin Dana W. 
Published: July 2005

Abstract
A recent study by the Toxic Substances Hydrology Program of the U.S. Geological Survey (USGS) shows that a broad range of chemicals found in residential, industrial, and agricultural wastewaters commonly occurs in mixtures at low concentrations downstream from areas of intense urbanization and animal production. The chemicals include human and veterinary drugs (including antibiotics), natural and synthetic hormones, detergent metabolites, plasticizers, insecticides, and fire retardants. One or more of these chemicals were found in 80 percent of the streams sampled. Half of the streams contained 7 or more of these chemicals, and about one‐third of the streams contained 10 or more of these chemicals. This study is the first national‐scale examination of these organic wastewater contaminants in streams and supports the USGS mission to assess the quantity and quality of the Nation's water resources. A more complete analysis of these and other emerging water‐quality issues is ongoing.
Phytoremediation of MethylTertiary‐Butyl Ether
Authors: Winnike‐McMillan S.K. , Zhang Q. , Davis L. C. , Erickson L. E. , Schnoor J. L. 
Published: July 2005

AbstractThe capability of plants to remediate methyltertiary‐butyl ether (MTBE) at contaminated sites is promising to the point that at least one field test is underway and others anticipated. Both hybrid poplar (Populus deltoides × Populus nigra‘DN34’ ‘Imperial Carolina’) cuttings and alfalfa (Medicago sativa) facilitate the removal of MTBE from saturated soil in the laboratory. The primary removal of MTBE is by soil volatilization facilitated by plant transpiration. Very little of the contaminant is metabolized or accumulated in laboratory studies. The MTBE that volatilizes and the small amount that diffuses from stems or transpires through leaves do not represent a risk in the atmosphere due to the rapid dispersion and degradation. Despite the different behavior of MTBE in groundwater, plants, and the atmosphere, concurrent phytoremediation of gasoline spills containing MTBE and other contaminants is expected to be very useful in the future.
Genetics of Metal Tolerance and Accumulation in Higher Plants
Authors: Datta Rupali , Sarkar Dibyendu 
Published: July 2005

AbstractPhytoremediation of metals is rapidly developing as a cost‐effective and environmentally friendly solution for cleaning up heavy‐metal‐contaminated sites. The most important requirements for effective phytoremediation are fast‐growing, high biomass plants that uptake and accumulate large amounts of toxic metals in their aboveground harvestable parts. A relatively small group of hyperaccumulator plants sequesters metals in their shoot tissues at high concentrations. In recent years, major scientific progress has been made in understanding the physiological mechanisms of metal uptake and transport in these plants. The majority of metal hyperaccumulators are slow growing and typically have low biomass, so bioengineering of nonaccumulators that have high biomass is essential for more effective phytoremediation. Biotechnology offers the opportunity to transfer hyperaccumulator phenotypes into fast‐growing, high biomass plants that could be highly effective in phytoremediation. However, comprehensive knowledge of the genetics of metal tolerance and accumulation is essential to design transgenic plants capable of phytoremediation. After an initial focus on plants with an immediate promise of application, research is now being directed at understanding the underlying mechanisms involved in heavy metal hyperaccumulation in plants. Once the rate‐limiting steps for uptake, translocation, and detoxification of metals in hyperaccumulator plants are identified, more informed construction of transgenic plants could become rather routine, which will help tremendously in more effective use of phytoremediation technology for cleaning up heavy‐metal‐contaminated sites.
Geochemical Modeling‐Computer Codes
Authors: Gonçalves Mário Abel 
Published: July 2005

AbstractGeochemical modeling practices are increasingly using a wealth of available computer codes specifically designed for such purposes. Although obtaining the codes is fairly easy nowadays, the uncritical use of these codes should be avoided at all cost. Each of the computer codes presented has their own limitations. Users must also critically evaluate the thermodynamic databases available for each program. Among the codes described, one puts more emphasis on the hydrogeochemical codes developed by the United States Geological Survey (USGS) and US Environmental Protection Agency (USEPA) mostly because these institutions provide a wide range of codes, an important number of which are regularly updated. Besides, codes available from other institutions are also referred to, a few of them being commercial programs. A final note is given about a new class of object‐oriented platform‐independent programs, whose main objective is to provide a framework for building specialized geochemical models.
Geochemical Modeling—Computer Code Concepts
Authors: Thyne Geoffrey 
Published: July 2005

AbstractThe formalism that allows us to relate mass actions equations (balanced chemical reactions) to actual solutions is called chemical thermodynamics or, more precisely, equilibrium thermodynamics. The basic idea is that elements, molecules, and compounds all contain some internal energy and that all systems try to reach a state where that energy is minimized (equilibrium). Natural systems, particularly low‐temperature systems, do not always reach equilibrium, but they do move in that direction. The internal energy of an element, molecule, or compound is expressed as its enthalpy or internal heat. The free energy of an element is an element, molecule or compound is the sum of its internal heat and its internal tendency toward disorder (entropy).
Geochemical Models
Authors: Gonçalves Mário Abel 
Published: July 2005

Abstract
Geochemical models are considered as an abstract representation of natural processes of a system, represented by a set of master variables and described by mathematical equations. The output data of these models is a quantitative representation of an outcome that can be either observable in the natural system or subject to experimental validation. From this definition, the importance of defining proper boundary conditions, and using reliable experimental data on models is discussed. Geochemical models may have as components, chemical reactions (inorganic and/or biological), transport of chemical elements by advection and dispersion, fluid flow, and heat transport. These are the building blocks of geochemical models, which can be divided as: speciation‐solubility, reaction‐path, inverse mass balance, and coupled reaction‐transport models. Finally, model validation and usefulness is shortly discussed.
Resistivity Methods
Authors: Jahani Hamid R. 
Published: July 2005

Abstract
In nature, groundwater is stored in geologically formed pore spaces. When these pores are interconnected, the groundwater moves from a high potential to a low potential zone. The rock layers at different depths have different “porosities” and consequently different water content. The more water in a formation, the lower the electrical resistivity, provided there is no other conducting layer such as clay or shale. If the contained water is brackish or saline, the resistivity of that layer drops even further (1).
The conductivity of an underground formation also varies as its homogeneity varies. The variation in conductivity affects the flow density, which in turn affects the distribution of the potential difference under the ground. The size of this effect depends on the size, shape, position and resistivity of the heterogeneity.
Thus, by measuring or determining the resistivities of earth layers at different depths, it is possible to infer indirectly the hydrogeologic character of a particular subsurface layer and also the quality of water it contains. The most applicable geoelectrical methods are resistivity methods in which an electrical current is passed into the ground so that the current distributes itself according to the conductivities of the geologic materials coming under the influence of the current.
Groundwater Flow in Heterogenetic Sediments and Fractured Rock Systems
Authors: Jacobs James A. , Vance David B. 
Published: July 2005

AbstractGroundwater flow in heterogenetic sediments and fractured rock systems is highly complex. Contaminants within these types of subsurface conditions are relatively common. Similarities and differences exist in flow characteristics of heterogenetic sediments and fractured rock systems, which influence contaminant fate and transport and subsequent remediation efforts at environmentally impacted properties.