bluuebunny/crossref_metadata_2025_split huggingface dataset:
Groundwater Remediation byIn SituAeration and Volatilization
Authors: Vance David B. , Jacobs James A. 
Published: July 2005

AbstractSoil venting is a term used for anin situaeration process that is a powerful remediation technology for the treatment of soils exposed to a variety of hydrocarbons. The practice of soil venting includes the following variations in application:Soil vapor extraction (SVE) systems are designed to exploit hydrocarbons potential for volatilization.Air sparging is an aeration process in which volatilizing air is injected into the saturated zone beneath the water table. Soil venting is used to recover the vapor laden air as it exits the water table.Bioventing is an aeration process designed to deliver oxygen to the subsurface for use by indigenous bacteria to degrade hydrocarbons; the focus is on minimizing hydrocarbon volatilization.Biosparging is a variant of air sparging in which oxygen stimulated biodegradation is the aim rather than volatilization. As with air sparging, soil venting is used to recover gas discharged through the water table.
Groundwater Flow Properties
Authors: Babel Mukand Singh 
Published: July 2005

Abstract
Groundwater constitutes a large component of the freshwater cycle. It moves more or less continuously from areas of recharge to areas of discharge through interconnected void spaces in porous media, fractured media, and large passages. Groundwater flow results mainly from precipitation that infiltrates into the soil; it also originates from influent streams, seepage from reservoirs, artificial recharge, seepage from oceans, etc. It often augments streamflow, eventually moving through the soil to the stream channel, also referred to as baseflow, or dry‐weather flow.
The driving force for groundwater movement is measured in terms of hydraulic head, which represents the fluid pressure potential and elevation potential. It is also referred to as the piezometric or potentiometric head. Contour maps of hydraulic head (piezometric or potentiometric maps), which can be constructed from water‐table elevations, can be used to infer directions of groundwater flow.
Groundwater Modeling
Authors: Holzbecher Ekkehard 
Published: July 2005

AbstractIn the first part the basics of groundwater flow and transport modeling are outlined. Starting from the fundamental differential equations for water flow and heat and mass transport, a groundwater problem is stated in the form of an initial boundary‐value problem. Next, the problem is discretized in order to carry out the analysis on a computer. Major discretization methods—finite differences, finite elements, and finite volumes—are explained briefly. A brief outline follows of the different steps in the task of modeling: preprocessing, processing, and postprocessing. Finally, inverse modeling is tackled briefly. References to standard textbooks are given for the different topics. Graphical input and output are illustrated in two examples. Special features are explained for some software products.
Horizontal Wells
Authors: Beljin Milovan 
Published: July 2005

Abstract
Horizontal wells are a new technology for solving problems in the environmental industry. Due to interest in horizontal wells for oil production, a large number of technical papers have been published regarding the reservoir engineering aspects of horizontal drilling and reservoir simulation. In the groundwater supply industry, the first theoretical analysis of groundwater flow to horizontal drains (collector wells) can be traced back to the early 1960s. In recent years, however, there has been renewed interest in horizontal wells for subsurface remediation. Horizontal wells offer significant advantages over vertical wells in environmental remediation and protection in many hydrogeologic scenarios. Horizontal well‐screen orientation complements common site logistics, typical aquifer geometry, and groundwater flow patterns. A single horizontal well can replace many closely spaced vertical wells.
What Is a Hydrochemical Model?
Authors: Lee Kung‐Yao , Fisher Thomas R. 
Published: July 2005

AbstractA hydrochemical model is a set of mathematical algorithms that calculate water, sediment, and nutrient fluxes from a defined watershed. A hydrochemical model is usually developed from a “hydro” submodel that calculates water balance, followed by erosion and nutrient submodels that simulate export of sediments and nutrients (e.g., nitrogen and phosphorus). Hydrochemical models can be categorized into lumped parameter models and distributed parameter models. Lumped parameter models simplify the watershed properties and ignore the spatial heterogeneity, whereas distributed models can explicitly represent the spatial effects of topography or the spatial variations of properties. Before conducting hydrochemical modeling, a hydrochemical model has to be calibrated by selecting values of parameters that represent the current conditions in the watershed using observed flow and water chemistry. In addition, a model should be validated with independent observed data to investigate the model's ability to simulate natural conditions and to estimate model errors at several time scales. Numerous models are available, each with its limitations and assumption, and it is important to evaluate several hydrochemical models to choose the best for each situation.
Treatment of Arsenic, Chromium, and Biofouling in Water Supply Wells
Authors: Loo Walter W. , Wen Jason J. 
Published: July 2005

Abstract
Arsenic is naturally occurring and also is a component of pesticides and may enter streams or groundwater through waste disposal or agricultural drainage. An EPA MCL level of 50 ug/l established in 1976 by US EPA and now lowered down to 10 ug/l. Five arsenic treatment methods are recommended for small systems users ‐ ion exchange, activated alumina, and the membrane technologies (reverse osmosis, nanofiltration, and electrodialysis reversal).
Chromium can contaminate drinking water sources through discharges from industries, leaching from hazardous waste sites, or it may occur naturally from the erosion of natural deposits. The U.S. EPA classified chromium 6 as a human carcinogen by inhalation. Ion exchange and the membrane technologies (reverse osmosis, nanofiltration, and electrodialysis reversal) are effective chromium treatment method but may be very costly.
Iron and manganese biofouling (usually associated with “iron bacteria”) is common in water supply wells. Biofouling sometimes cause clogging, corrosion, and water quality degradation. Combinations of disinfectants, selected acids and dispersants (wetting agents) have become a part of the arsenal of weapons being used to rehabilitate problems in a well.
In‐situ electrokinetic treatment of chromium, arsenic and biofouling may provide cost effective solution.
Artificial Recharge of Unconfined Aquifer
Authors: Rai S.N. , Singh V.P. 
Published: July 2005

AbstractGroundwater plays a major role in augmenting water supply to meet the ever‐increasing demands for domestic, agricultural, and industrial usages. Increasing dependence of water supply on groundwater resources leads to more use of aquifers as a source of fresh water supply and subsurface reservoir for storing excess surface water. The advantage of unconfined aquifers over confined aquifers to serve as subsurface reservoir is that the storage of groundwater in large quantity is possible only in unconfined aquifer, which is because the storativity of the unconfined aquifer is linked to the porosity and not to the elastic properties of the water and solid matrix, as in case of the confined aquifer. Also, the vast surface area of the unconfined aquifer above the water table is available to receive the surface applied recharge, whereas in case of the confined aquifer, only a small open area exposed near to the ground surface or leaky portion of the aquifer boundary is available to receive the recharge. This article deals with artificial recharging of the unconfined aquifer and related problems.
Mass Transport in Saturated Media
Authors: Hudak Paul F. 
Published: July 2005

Abstract
Advection and hydrodynamic dispersion affect the movement of solutes in groundwater. Advection is the movement of solutes with flowing groundwater. Hydrodynamic dispersion is the spreading of groundwater and its dissolved constituents by mechanical mixing and chemical diffusion. The aquifer matrix induces mechanical mixing, which causes water to move faster at some locations than at others and forces water to move through different passages. Chemical concentration gradients induce diffusion, which causes solutes to move from areas of high to low concentration. Diffusion may take place in groundwater that is not flowing. Hydrodynamic dispersion takes place in all directions in three‐dimensional space, but to a greater degree parallel to groundwater flow. The longitudinal component of hydrodynamic dispersion parallels the direction of groundwater flow. Transverse components occur in all directions in a plane perpendicular to groundwater flow. Beyond the pore scale, bodies of rock or sediment with different hydraulic conductivity may induce mechanical dispersion within an aquifer. Reactive solutes, which have a tendency to intermittently sorb to the aquifer matrix, move at a slower rate than does groundwater.
Megawatersheds
Authors: Bisson Robert A. 
Published: July 2005

AbstractThe term “megawatershed” describes deep‐seated subsurface aquifer systems that may consist of gravel, fracture‐hosted bedrock, and/or sedimentary structures, which are integrated in terms of recharge, storage, transmissivity, and containment. They may not coincide with surface topographic divides and may receive recharge from parts of several surface watersheds including amounts of mountain block recharge. “Megawatershed” is a conceptual model, or paradigm, that describes this new class of groundwater domain. Megawatersheds are formed over geologic time by a combination of factors, including tectonically induced brittle fracturing and displacement of rock facies and strata and solutioning of parent rock facies and regolith by chemically aggressive meteoric and hydrothermal waters. The history and nature of regional tectonic stress fields and principal bounding faults, interacting with lithology and climate, play a major role in determining the geometry and extent of megawatershed boundaries.
Bacteria Role in the Phytoremediation of Heavy Metals
Authors: Johnson Anthea , Singhal Naresh , Takis Elefsiniotis P. 
Published: July 2005

AbstractHeavy metals are of particular concern in the environment as they cannot be degraded by natural processes and instead tend to accumulate in ecosystems. At many sites the metals exist in toxic concentrations within the soil, posing a threat to most forms of life, including humans, therefore necessitating their removal. Phytoremediation aims to use plants and bacteria to mediate the removal of heavy metal contaminants from soils. Metals can be mobilized for uptake by plant roots via a number of plant and bacterial processes such as soil acidification, biosurfactant solubilization, chelation, or redox transformation. In addition, other processes immobilize the metals through conversion to insoluble forms. Examples of immobilization processes induced by bacteria and plants are sorption, precipitation, sequestration, and volatilization. Bacteria not only have an influence on the mobility of metals in soils but also have a significant role in the rhizosphere due to their interactions with plants. Bacteria and plants can form synergistic or antagonistic relationships, supplying each other with nutrients or energy sources, or producing toxins to reduce growth and competition for limiting nutritional elements. By utilizing natural biological remedial processes, phytoremediation may present a more sustainable approach for the restoration of contaminated soils.
Fossil Aquifers
Authors: Phoenix Laurel 
Published: July 2005

Abstract
Fossil aquifers are bodies of very deep aquifers that are disconnected from our contemporary hydrologic cycle. Water in these aquifers can be hundreds to thousands of years old and thousands of feet deep. As they are not recharged by today's precipitation, using them as a water supply is not sustainable. Other deep aquifers may still be connected to surface precipitation, but recharge so slowly relative to human time scales that they can practically be considered nonreplenishable fossil aquifers as well. Not only are these supplies finite, but their depth also makes them more expensive, not only for the initial drilling but also for the increased energy required to pump water from these depths.
Why develop an unsustainable and expensive water supply? The world water deficit is straining countries in many ways. Drought, water pollution, and rising populations are making communities drill ever deeper for water. The growing international grain trade is also a trade in water. Examples of mining fossil water are given in China, the Middle East, and the United States.
Modeling Contaminant Transport and Biodegradation in Groundwater
Authors: Oswald Sascha E. 
Published: July 2005

AbstractBiodegradation is an important factor in the fate of organic contaminants and may reduce the concentration and also the total mass of a contaminant. Although several processes can contribute to the natural attenuation of contaminants, biodegradation is often the main process by which mass may be destroyed; other processes such as sorption merely retain the contaminant mass for later release. Therefore, modeling monitored as well as enhanced natural attenuation, usually has to include biodegradation modeling.The key processes to be modeled are advection, dispersion, sorption, and degradation by microbes. However, further processes could also be relevant, for example, ion exchange, precipitation and dissolution of minerals, speciation, and surface‐complexation.The basis for transport modeling is flow modeling; transport modeling is the basis for modeling contaminant itself transport and biodegradation (see Fig. 1). Often in more general terms this is called reactive transport modeling, which includes transport plus biodegradation and/or hydrogeochemical modeling. To model a field scale problem of reactive transport appropriately, one should plan this as a set of modeling tasks building up to this challenging undertaking.
Modeling Non‐Point Source Pollutants in the Vadose Zone UsingGIS
Authors: Corwin Dennis L. , Logue Keith 
Published: July 2005

AbstractNon‐point source (NPS) pollutants are characteristically diffuse in nature, tend to have a long active presence in the global ecosystem, and result in chronic health effects on humankind. Because of their nature, NPS pollutants are a global concern. Assessing the fate and transport of NPS pollutants both in real time and from model simulations is crucial to understanding cause‐and‐effect relationships and for synthesizing current knowledge into a useable form for policy decisions. However, modeling NPS pollutants is a complex multidisciplinary problem that requires a systems‐based approach within a spatial context with an awareness of scale. It is the objective of this encyclopedia article to provide a general discussion of the three components of an NPS pollutant model: data, geographic information system (GIS), and model. Each component is discussed from a systems‐based perspective to provide an understanding of their interaction and interdependence. Because temporal and spatial scale determines the structure of an NPS pollution model, the theory of hierarchical scales is presented. It is concluded that the future success of landscape‐scale environmental modeling rests not on enhancing the detail of model structure, but rather on characterizing the spatiotemporal variability of model inputs and parameters.
Biofouling in Water Wells
Authors: Smith Stuart A. 
Published: July 2005

AbstractBiofouling as a term has its origins in pre‐World War II studies of marine fouling and generally refers to coating, encrustation, and corrosion associated with the attachment of organisms to surfaces, including human‐engineered structures. The phenomenon arises from the tendency of life across all known kingdoms to cling to and use surfaces. Biofouling takes many forms, ranging from bacterial‐viral films plaguing urinary tracts to fouling of water intakes and other maritime structures (and even baleen whales) by films that also include macroorganisms such as barnacles and zebra mussels.Biofouling of water wells and associated downstream systems tends to result from the formation of biofilms by bacteria. It is now widely recognized that biofouling is the first or second most costly deteriorating factor for groundwater systems in North America.
Industrial Mine Use: Mine Waste
Authors: Von Der Heyden Constantin 
Published: July 2005

AbstractThe extraction of minerals and the mining and processing of ores produces a variety of effluents, which, if left untreated and discharged into the environment, can impact the natural and social environment. Various types of mine effluent and the conditions giving rise to their generation are described, with some focus on acid mine drainage (AMD) in particular, both in terms of the chemistry of generation and common methods of AMD remediation. Both active treatment (for example, high density sludge process) and passive remediation (for example, wetlands) treatment of mine effluents are explored and the common processes of remediation are discussed in detail.
Electric Generating Plants—Effects of Contaminants
Authors: Reash Robin J. 
Published: July 2005

Abstract
Coal is an abundant, relatively low‐cost energy source whose extraction and use fostered the rapid industrialization of many countries during the twentieth century. Prior to the enactment of major environmental statutes by the U.S. Congress during the period 1960–1980, the extraction and combustion of coal resulted in pervasive, significant instances of environmental damage in the air, water, and soil. Coal contains a variety of organic and inorganic constituents, and the mobilization of these compounds (typically found in trace levels in geological strata) into concentrated air or water discharges often posed risks to human health and the environment. An enormous amount of coal ash, produced during the combustion process, is disposed onto landfills or in treatment reservoirs. Trace metals that are leached from ash particles can be discharged at levels that may exceed toxic thresholds. Significant improvements in the overall environmental impact of power generating facilities were realized in the United States during the past 30 years, as a result of implementation of more stringent environmental regulations. The development of “clean coal” technologies has allowed continued use of an energy source whose reserves are expected to last at least 200 years.
Observations of Climate and Global Change from Real‐Time Measurements
Authors: Easterling David R. , Karl Thomas R. 
Published: July 2005

Abstract
Is the planet getting warmer?
Is the hydrologic cycle changing?
Is the atmospheric/oceanic circulation changing?
Is the weather and climate becoming more extreme or variable?
Is the radiative forcing of the climate changing?
These are the fundamental questions that must be answered to determine if climate change is occurring. However, providing answers is difficult due to an inadequate or nonexistent worldwide climate observing system. Each of these apparently simple questions are quite complex because of the multivariate aspects of each question and because the spatial and temporally sampling required to address adequately each question must be considered on a global scale. A brief review of our ability to answer these questions reveals many successes, but points to some glaring inadequacies that must be addressed in any attempt to understand, predict, or assess issues related to climate and global change.
Overview of Weather Systems
Authors: Nielsen‐Gammon John W. 
Published: July 2005

Abstract
The attempt to understand the weather is driven largely by the desire to be able to forecast the weather. However, the atmosphere is a complicated dynamical system, and an understanding of even the basic physical principles came only recently. Before that, scientists either attempted to understand the physical causes of weather events or recorded “weather signs,” rules for weather forecasting. Because the physical understanding was incorrect, and most weather signs had no physical basis, neither approach was very successful. True progress in the study of the atmosphere that would lead to success in weather forecasting required a complete understanding of physical principles and a comprehensive set of observations of the atmosphere.
Basic Research for Military Applications
Authors: Bach W. D. 
Published: July 2005

Abstract
The military must understand the atmosphere in which it operates. That understanding will ultimately depend on scientific understanding of the atmospheric processes, an ability to use all of the information available, and an ability to synthesize and display that information in a quickly understandable fashion.
The military's needs for understanding the atmosphere's behavior has changed as a result of geopolitics and advancing technology. On the battlefield, future enemies are more apt to resort to chemical or biological attacks as a preferred method of mass destruction. The atmospheric boundary layer is the pathway of the attack. Increased reliance on “smart” weapons means that turbulent and turbid atmospheric effects will influence electromagnetic and acoustic signals propagating through the boundary layer. Intelligence preparation of the battlespace, a key to successful strategies, depends on full knowledge of the enemy, weather, and terrain. It requires an ability to estimate atmospheric details at specific locations and future times to maximize strategic advantages that weather presents a commander. It also avoids hazards and strategic disadvantages.
Rain and Rocks: The Recipe for River Water Chemistry
Authors: Islam Mohammed Riajul 
Published: July 2005

AbstractAerosols are the primary source of chemical elements transported by rainwater, which are removed from the atmosphere by rainout or by washout. Atmospheric aerosols (sea salt, crustal dust, and biogenic aerosols) have been found as the major sources of dissolved species in river water. Dissolved components from rainwater come from those originating from sea salt aerosols; from those originating from terrestrial aerosols (soil dust, biological emissions); and from those originating from anthropogenic sources (industry, agriculture, burning of fossil fuels, etc.).Along with the geological characterization of the watershed, meteorological parameters are critically important in evaluating rainfall effects.
Uncertainties in Rainfall–Runoff Modeling
Authors: Willems Patrick 
Published: July 2005

AbstractErrors and uncertainties in the prediction of rainfall–runoff are often substantial. Consideration of these errors is therefore crucially important. When water decision‐making is based on the rainfall–runoff prediction, for instance, by means of rainfall–runoff, uncertainties affect model outcomes and, consequently, the decisions. Hence, good modeling practice provides not only the results of model predictions but also the accuracy of these results. It supplies decision makers with important additional information on the uncertainty in the data and information that they use as a basis for their decisions. After quantification of the runoff prediction errors, water policies can be set up for which the efficiency can be guaranteed up to specified acceptable risk levels. Combined with the uncertainty analysis, a sensitivity analysis provides the modeler and decision maker with information about the importance of various types of model limitations and sources of uncertainty.