bluuebunny/crossref_metadata_2025 huggingface dataset:
The Arsenic Drinking Water Crisis in
B
angladesh
Authors: Bryce Charlie , Philp Jim
Published: July 2005

Although the incidence of arsenic poisoning in groundwater is worldwide and includes Bangladesh and India, Taiwan, Vietnam, Chile, China, North America, and Finland, the area of the highest demand for a resolution of the problem is Bangladesh. The source seems to be geological, for arsenic has been found in tube well water used for drinking and irrigation, although the geochemistry is not completely understood. As many thousands of boreholes have been produced to support modern irrigation systems, the underground aquifers are aerated, which causes transformation of anaerobic conditions to aerobic conditions. The presence of oxygen in this way decomposes arsenopyrite‐releasing arsenic acid. At low pH, this arsenic dissolves in water and hence leads to water contamination. The arsenic content of sediments is high relative to crustal concentrations. The biogeochemical cycling of arsenic and iron are coupled in deltaic systems; iron oxyhydroxides act as a carrier for the deposition of arsenic in sediments. From there, it can be mobilized by bicarbonate, which can extract arsenic from sediments under both aerobic and anaerobic conditions.

Arsenic also becomes a pollutant as a result of various industrial uses and activities. Arsenic is a metalloid, and its primary usage has been in agriculture, in formulating herbicides, especially for controlling weeds in cotton fields. Sodium arsenite has been used as an insecticidal ingredient in sheep‐dips. In industry, arsenic has found use in glass manufacture and a new role in the semiconductor industry. Copper smelting releases significant amounts into soils.
Applications of Soil Vapor Data to Groundwater Investigations
Authors: Hartman Blayne , Jacobs James A.
Published: July 2005

This article describes the uses and interpretation of soil vapor data for a variety of common applications related primarily to groundwater. It begins with an overview of the applications of soil vapor surveys, a brief discussion of the various soil vapor methods, and then focuses on a number of specific issues relating to soil vapor surveys for groundwater investigations. The intent of this article is to guide professionals on when, why, and how soil vapor data can be useful for groundwater‐related investigations and how to interpret the results.
Connate Water
Authors: Brody Richard C.
Published: July 2005

Connate water is water trapped in the interstices of sedimentary rock (subsequently buried by younger sediments) or igneous rock when it was deposited. Connate water occurs as a film of water around each grain of sand in the rocks, is chemically or physically bound to the lithosphere (soil and rocks), and has existed since the rocks formed (also see Fossil Water). Although connate water resides in the rocks (interstitial or interstratal), it is not part of the groundwater system and does not play a role in the hydrologic cycle.
Sub‐Surface Redox Chemistry: A Comparison of Equilibrium and Reaction‐Based Approaches
Authors: Singhal Naresh , Islam Jahangir
Published: July 2005

Redox reactions, which involve the transfer of electrons from one chemical species to another, play an important role in the subsurface environment. The knowledge of redox chemistry is essential to understanding the relationships among chemical speciation, mobilization, and toxicity. Redox reactions can be abiotic or biotic, and they may be described using the equilibrium or kinetic approaches. The equilibrium approach assumes that thermodynamic equilibrium has been established in the system and that the prevailing redox conditions can be described with equilibrium relationships for the various reactions. Although the equilibrium approach has been commonly used, many reactions in the subsurface environment, mostly heterogeneous reactions, progress slowly and do not conform to the equilibrium assumption. Such reactions are best described with the kinetic approach, which describes the reactions using kinetic expressions. However, our current understanding of kinetic processes is primitive. This article presents a summary of the various equilibrium and kinetic approaches that have been used in the literature to describe subsurface redox conditions.
Tidal Efficiency
Authors: Rasmussen Todd
Published: July 2005

Ocean tides often cause water levels in coastal aquifers to fluctuate. These fluctuations result from two different causes. In confined aquifers, the additional weight of the water on the surface increases the pressure on the water at depth, which causes an increase in water levels in observation wells located near the coast. In this case, no movement of water between the ocean and the aquifer may have occurred. In unconfined aquifers, however, the loading effect does not occur. Instead, water that has moved directly through the pores within the aquifer has caused the water level response. Regardless of the mechanism, both processes can be described with the phase lag, or delay, between the tidal peak and the aquifer response peak, as well as the amplitude ratio between the magnitudes of the response and the tides.
Transport of Reactive Solute in Soil and Groundwater
Authors: Capiro Natalie L. , Bedient Philip B.
Published: July 2005

The extensive impacts to soil and groundwater by contaminants such as chlorinated solvents and petroleum hydrocarbons can be attributed to their widespread use in the United States and to their persistence in the environment. Understanding the fate and transport of these pollutants and other solutes is essential for the protection of water supplies and successful field site remediation. Subsurface solute fate and transport is dictated by processes that fall into the general categories of hydrodynamic, abiotic, and biotic. Hydrodynamic processes that include advection and dispersion influence flow patterns through the vadose zone and in groundwater. Those processes that impact solute interactions with the surrounding aquifer matrix, such as sorption or the composition of the contaminant itself, are known as abiotic. The biotic category is variable based on available substrates and nutrients, but under certain favorable conditions, these microbial processes can have a profound impact on contaminant structures and their longevity in the environment. Transport processes are extremely difficult to quantify because of the vast heterogeneities encountered in the field; however, improving our comprehension continues to be an area of extensive research for many science and engineering fields.
Unconfined Groundwater
Authors: El‐kadi Aly I.
Published: July 2005

An unconfined aquifer is a geologic formation with subterranean water that is not confined by relatively impermeable layers. Part of the precipitation and irrigation water as well as water from recharge basins, reservoirs, and ponds moving downward from the soil layer will reach the saturated groundwater zone. The top of this zone is the water table, which separates the fully saturated zone from a partially saturated zone. The latter zone is simply referred to as the unsaturated zone, but it is also known as the zone of aeration or vadose zone. Generally, the water in the unsaturated zone is under less than atmospheric pressure. The unsaturated zone includes the capillary fringe, directly above the water table, which is near saturation but still under negative pressure relative to the atmospheric pressure.
Vadose Zone Monitoring Techniques
Authors: Rykwalder Philip R. , Blanford William J.
Published: July 2005

Monitoring fluids of the vadose zone has multiple motives, including detecting contaminants, measuring soil properties and water conditions for construction or monitoring geologic hazards, and determinations of water saturation that may be used for optimizing irrigation. Because fluids must move through the vadose zone to reach the water table, monitoring of the vadose zone allows predicting possible sources and processes of groundwater contamination. Geologic hazards such as landslides, rising water tables, or land subsidence can be partially predetermined by monitoring the vadose zone. And in agriculture, monitoring soil water content to irrigate most efficiently has a long history.
Water in the Unsaturated Zone
Authors: Babel Mukand Singh
Published: July 2005

The soil profile immediately below the land surface and above the water table is called the unsaturated zone, where the pores contain both water and air. This zone differs from the saturated zone, where the pores are saturated with water. The unsaturated zone is sometimes called the vadose zone.

The thickness of an unsaturated zone can range from zero (e.g., when a lake or marsh is at the surface) to hundreds of meters, as is common in arid regions. It is a zone of natural and human‐induced activity. It experiences physical phenomena such as thermodynamic interactions, transport processes of various kinds, and chemical reactions involving both natural and artificial substances. Several biological activities involving plant roots, rodents, worms, microbiota, and other organisms also take place in this zone. The zone is used for cultivating plants, constructing structures, and disposal of waste.

To a large degree, the unsaturated zone controls the transmission of water to aquifers (water bearing strata), as well as to the land surface, to water on the surface, and to the atmosphere. It also acts as a filter as it removes undesirable substances before they reach and affect aquifers.
Well Test
Authors: Williams Dennis E.
Published: July 2005

Well tests are conducted in completed wells after development in order to collect information on the hydraulic parameters of the well and surrounding aquifers. Groundwater level data from the well tests are collected, compiled, and graphically plotted, and the data are evaluated using various methods to determine hydraulic parameters of the aquifer and well.

Step‐drawdown tests are generally the first type of test performed. This test involves pumping the well at several rates and measuring the change in water level as time progresses. Following the step‐drawdown test, a constant rate pumping test is usually performed. The well is pumped continuously at the design discharge rate over a longer period of time, usually more than 24 h, in order to estimate longer‐term drawdown effects. Recovery tests, carried out after pumping tests, involve measuring the rate at which the water level recovers to its initial level after pumping has stopped.

A slug test is a popular and inexpensive method of estimating the hydraulic properties of aquifers in small diameter wells when the hydraulic conductivity of the aquifer materials is too low to conduct a pumping test. This test involves rapidly adding or removing a “slug of water” from a well and measuring the rate at which the water level recovers.
Low Flow Groundwater Purging and Surging
Authors: Vance David B. , Jacobs James A.
Published: July 2005

Groundwater monitor wells are installed primarily as tools to measure the dissolved concentrations of contaminants in groundwater in and around facilities where the release of contaminants has occurred or where the potential exists for such a release to occur (i.e., adjacent to landfills). These wells are installed with the intention of obtaining an accurate assessment of the conditions in the formation adjacent to the well. A significant body of literature and guidance documentation exists concerning the location, drilling, installation, and development of those wells to that end. However, it has become evident that the quality of the data yielded from monitor wells is dependent on screen length and location (addressed during design and installation), purging method, and purge volume.

The use of screened hydraulic probes is recognized as an accurate sampling method and as the yardstick for comparison with various monitor well sampling techniques. Their practical use is of value for initial plume delineation and assessment in aid of the design of a monitor well network; however, they are impractical as a long‐term monitoring system. The groundwater monitor well is essential for that role.
Particulate Transport in Groundwater—Bacteria and Colloids
Authors: Vance David B. , Jacobs James A.
Published: July 2005

Evaluation of mass transport of entrained material in groundwater flow systems is typically focused on two primary areas, dissolved organic or inorganic species, and flowing free phase liquids. However, although generally not as dominant overall, the movement of small particles in groundwater can cause problems at the low concentrations required by regulatory limits. In addition, the proponents of
in situ
bioaugmentation, through injection of bacteria, must rely on successful particulate mass transport through the saturated soil matrix.
Groundwater and Cadmium: Chemical Behavior and Treatment
Authors: Jacobs James A. , Foreman Craig
Published: July 2005

Cadmium occurs naturally in ores containing other elements such as oxygen (cadmium oxide), sulfur (cadmium sulfate, cadmium sulfide), and chlorine (cadmium chloride) or compounds (cadmium carbonate). Cadmium is usually extracted during the production of other metals such as zinc, lead, and copper. A primary use for cadmium is in rechargeable nickel–cadmium and solar batteries, which are sold worldwide. Cadmium does not corrode easily and is also used in metal plating and coating operations including transportation equipment and various industrial machinery as well as plastics manufacturing. It is used in numerous pigments, in baking enamels, and in photographic processes as well as in television and monitor screen phosphors. Cadmium is released into the environment through industrial waste streams and landfills. Cadmium is relatively mobile in surface and groundwater and has a United States Environmental Protection Agency (U.S. EPA) Maximum Contaminant Level Goal (MCLG) of 5 parts per billion (ppb) in drinking water (1). The World Health Organization has set the provisional tolerable daily intake of cadmium at 60–70 µg/day (2).
Groundwater and Cobalt: Chemical Behavior and Treatment
Authors: Jacobs James A. , Walter Lise
Published: July 2005

Cobalt has been used for about 5000 years. Cobalt metal is produced as a by‐product of copper, nickel, and lead production. It is not economically feasible to isolate cobalt. Cobalt is important for use in the commercial, industrial, and military sectors. Most cobalt remediation projects occur near mines. All of the main aqueous species of the metal contain cobalt in the +2 oxidation state. Cobalt is most hazardous to the human respiratory system. Conventional remedial methods include soil excavation and groundwater extraction and treatment. Newer methods of remediation include phytoaccumulation and geochemical fixation with pH adjustment.
Groundwater and Lead: Chemical Behavior and Treatment
Authors: Jacobs James A. , Kirkland Lisa
Published: July 2005

Lead (Pb) occurs naturally in the earth's crust and is reported as being the most abundant among the heavy metals, with the average Pb content of the crust ranging from 13 to 16 parts per million (1). Lead has a crustal abundance of 1.4 × 101 mg/kg, with an estimated oceanic abundance of 3 × 10−5 mg/L (2). Lead makes up 0.013% of the earth's crust. There are more than 200 minerals of Pb. Natural mobilization of Pb into the environment occurs mainly from the erosion of Pb‐containing rocks and via gaseous emissions during volcanic activity. Lead is mined and refined easily. On a worldwide basis, most lead is concentrated by roasting galena, also called lead sulfide (PbS), in hot air. Nearly one‐third of the consumption in the United States is obtained by recycling efforts (2).
Groundwater and Nitrate: Chemical Behavior and Treatment
Authors: Jacobs James A. , Geddes‐McDonald Lorraine
Published: July 2005

Nitrate is a naturally occurring substance, which is an essential ingredient for the growth of plants. Human activities can contribute to higher levels of nitrate in the ground and surface waters. The major source of excess nitrogen is nitrate fertilizers for agricultural, lawn, and other garden uses. Nitrates are sourced from nitrates in nitrate fertilizers, the storage or use of animal manure, leaky septic systems, leaky sanitary sewer pipelines, and improper disposal of treated wastewater containing high nitrate levels. Through storm runoff and leaching processes, nitrates have become dissolved in stormwater runoff or infiltration waters. These sources of dissolved nitrates have created significant impacts on worldwide surface water and groundwater resources.
Groundwater and Perchlorate: Chemical Behavior and Treatment
Authors: Jacobs James A. , Dwyer Shonel
Published: July 2005

Large‐scale perchlorate production began in the 1940s. Perchlorate leakage has been ongoing in some cases for decades. The majority of perchlorate spills are related to the use of explosive propellant as a solid rocket fuel for missiles and for the NASA space shuttle. It has only been since the late 1990s, when laboratory methods improved detection of perchlorate in the groundwater, that the full impact of the groundwater contamination became evident. A variety of point of use treatments for perchlorate are available, at varying efficiencies and costs. Of the various
in situ
technologies, anaerobic bioremediation is the most promising for widespread subsurface perchlorate treatment.
Groundwater Balance
Authors: Kumar C. P.
Published: July 2005

Water balance techniques have been extensively used to make quantitative estimates of water resources and the impact of man's activities on the hydrologic cycle. On the basis of the water balance approach, it is possible to make a quantitative evaluation of water resources and its dynamic behavior under the influence of man's activities. In this article, an attempt has been made to describe the methodologies to understand and evaluate the various recharge and discharge components of groundwater balance equation and to establish the recharge coefficient with a view to work out the groundwater potential of an area.
Phytoremediation Enhancement of Natural Attenuation Processes
Authors: Vance David B. , Jacobs James A.
Published: July 2005

Phytoremediation is a remediation method that uses what is in essence enhanced natural attenuation for cleanup. There are a variety of phytoremediation methods, some having multiple names: phytostabilization, rhizodegradation (phytostimulation, rhizosphere bioremediation, or plant‐assisted bioremediation), rhizofiltration (contaminant uptake), phytodegradation (phytotransformation), phytovolatilization, and Phytoaccumulation (phytoextraction or hyperaccumulation). Various types of plants can be used in phytoremediation, including poplar trees, alfalfa, black locust, Indian mustard, fescue grass, crested wheatgrass, and Canada wild rye.
River‐Connected Aquifers: Geophysics, Stratigraphy, Hydrogeology, and Geochemistry
Authors: Al Tom A. , Macquarrie Kerry T. , Butler Karl E. , Nadeau Jean‐Christophe , Dawe Melissa R. , Amskold Larry
Published: July 2005

Pumping of water from wells constructed in aquifers adjacent to a river commonly causes infiltration of river water toward the wells, thereby increasing the total available water yield. This type of water production has been used extensively in many European countries and, to a lesser extent, in North America. The flow of river water through permeable riverbed and aquifer sediments, commonly referred to as riverbank filtration, can provide filtration and general purification benefits. Some of the most important considerations in managing aquifer systems of this type include the stratigraphic controls on the flow path and infiltration flux for river water entering the aquifer, the travel time between the river and the pumping wells, and the spatial and temporal variations in geochemical reactions that occur as river water infiltrates the aquifer, leading to changes in water quality.

In this contribution, the Fredericton Aquifer, which is considered typical of many alluvial‐valley water‐supply aquifers, is used as a case study to illustrate possible approaches to the characterization of river‐recharged aquifer systems, and to describe some of the important stratigraphic, hydrogeologic, and geochemical features of these systems. The combined use of geophysical, hydrogeological, and geochemical methods of investigation has led to a more complete understanding of river water infiltration toward municipal wells and the resulting water quality implications.
Groundwater— Nature's Hidden Treasure
Authors:   Environment Canada
Published: July 2005

It is sometimes thought that water flows through underground rivers or that it collects in underground lakes. Groundwater is not confined to only a few channels or depressions in the same way that surface water is concentrated in streams and lakes. Rather, it exists almost everywhere underground. It is found underground in the spaces between particles of rock and soil, or in crevices and cracks in rock. The water filling these openings is usually within 100 metres of the surface. Much of the earth's fresh water is found in these spaces. At greater depths, because of the weight of overlying rock, these openings are much smaller, and therefore hold considerably smaller quantities of water.

Groundwater flows slowly through water‐bearing formations (aquifers) at different rates. In some places, where groundwater has dissolved limestone to form caverns and large openings, its rate of flow can be relatively fast but this is exceptional.

Many terms are used to describe the nature and extent of the groundwater resource. The level below which all the spaces are filled with water is called the
water table
. Above the water table lies the
unsaturated zone
. Here the spaces in the rock and soil contain both air and water. Water in this zone is called
soil moisture
. The entire region below the water table is called the
saturated zone
, and water in this saturated zone is called
groundwater
.
Hydrologic Feasibility Assessment and Design in Phytoremediation
Authors: Weaver J. W. , Mccutcheon S. C. , Hutchinson S. L.
Published: July 2005

Several design considerations for phytoremediation are based on the capability of trees to remove contaminated water from aquifers. These capabilities depend upon the amount of water that can be withdrawn, the vertical distribution of contaminants, and flow patterns in the aquifer. For each of these, an example field site is given where methods were applied to quantify the characteristics. These include a model of forest evaporation for estimating the balance between precipitation and evapotranspiration, a simple model of recharge‐driven plume diving, and the use of groundwater flow modeling for assessing various features of the groundwater flow.
Finite Element Modeling of Coupled Free and Porous Flow
Authors: Hanspal Navraj S. , Waghode Atul N. , Das Diganta Bhusan
Published: July 2005

In this article, the finite element method will be discussed in the context of solving coupled free and porous flow governed by Navier–Stokes and Darcy equations, respectively. Boundary conditions that may be used for simulating coupled flow problems are also discussed very briefly.
Geophysics and Remote Sensing
Authors: Jansen John R.
Published: July 2005

When data cannot be gathered by direct observation, such as observing an outcrop or taking a physical sample, information can often be obtained by using remote sensing techniques. Remote sensing methods measure physical properties of materials by measuring changes in the flux of various forms of energy using natural or transmitted fields. The science of applying these methods to earth materials is called geophysics

Geophysics is commonly used to obtain subsurface information for a variety of resource development and engineering applications. A partial list of applications for which geophysical methods can be used includes mapping aquifers, mapping water quality, mapping geologic structure, measuring flowing fluids, finding buried objects for engineering and archeological purposes, and measuring
in situ
soil and rock properties. The major energy fields used include magnetic fields (magnetometry), electrical fields (electrical resistivity and spontaneous potential), electromagnetic fields (electromagnetic induction and ground‐penetrating radar), propagation of seismic waves (seismic reflection, seismic refraction, passive acoustic emission monitoring, and spectral analysis of surface waves), the gravitational field (gravimetry), gamma‐ray radiation (gamma‐ray spectroscopy), and heat transfer (geothermal). Other physical properties can be measured by bombarding the material with gamma rays (electron density) or high‐energy neutrons (hydrogen content). Less commonly, properties such as thermal conductivity, electrical chargeability, or magnetic resonance are also measured.
Groundwater Velocities
Authors: Babel Mukand Singh
Published: July 2005

Groundwater flows through interconnected pore spaces in subsurface soil in response to differences in fluid pressure and elevation. Groundwater flow rates are extremely slow, compared to surface water, and they are also highly variable. For example, in clayey soils, groundwater moves as slowly as a fraction of a millimeter per day; however, in sandy soils, it moves faster, even up to more than a meter per day. Hydrology is concerned with both the speed and the direction of groundwater movement. Groundwater velocity is very important in dealing with contaminant migration and arrival time, mass flux, site characterization, reactive barrier design, and calibration of transport processes.
Groundwater Flow and Transport Process
Authors: Almasri Mohammad N. , Kaluarachchi Jagath J.
Published: July 2005

Groundwater is the primary source of drinking water in many parts of the world and the sole supply of potable water in many rural communities. Due to population growth over time, there is an increasing stress on groundwater resources to meet the growing demand for freshwater, especially in arid and semiarid regions where drought conditions may prevail. In addition, protection of the quality of groundwater resources is very important considering the diversity of potential pollution sources. As such, it is essential for efficient use, effective management, and protection of groundwater resources to understand and comprehend basic groundwater flow concepts and fundamental transport processes of contaminants. This study present a general outline of the main concepts of groundwater flow and transport processes. This includes the vertical distribution of subsurface water; Darcy's law; aquifer types; sources and types of groundwater contamination; contaminant transport via dispersion, advection, and diffusion; physical governing equations; and mathematical modeling.
Groundwater and Arsenic: Chemical Behavior and Treatment
Authors: Vance David B. , Jacobs James A.
Published: July 2005

Arsenic is not an abundant element in the earth's crust; the average crustal concentration of arsenic is 1.8 mg/Kg (1) to 5 mg/Kg (2). Arsenic ranks as the 52nd element in abundance, between tin and molybdenum (1). However, through geogenic processing of crustal materials, arsenic can be concentrated in soils to a typical range of 2 to 20 mg/Kg (3) to 1 to 50 mg/Kg (2), with concentrations as high as 70 mg/Kg being unremarkable (3). Human activity generates anthropogenic arsenic, which makes it the third most common regulated inorganic contaminant found at U.S. Superfund sites.

Arsenical copper was in use by 4000BC, and the toxic effects of arsenic were documented by early Greek writers. More recently, arsenic has been linked to skin, bladder, and other cancers (4). The U.S. Environmental Protection Agency (USEPA) lowered the arsenic standard in drinking water from 50 µg/L to 10 µg/L, effective January 23, 2006.

Modern usage of arsenic includes formulation of pesticides and herbicides, decolorization of glass, paint manufacturing, the production of semiconductors, and the treatment/preservation of wood. Pressure treated lumber was commonly treated for decades using copper‐chromium‐arsenate (CCA). This product, also called “green wood,” has been used for foundation lumber and more recently as wood for outdoor children's play structures and picnic tables. The CCA wood is being phased out for toxicity concerns and environmental reasons. Many of the pressure treatment lumber facilities have significant soil and groundwater contaminated with arsenic as well as chromium.
Groundwater Vulnerability to Pesticides: An Overview of Approaches and Methods of Evaluation
Authors: Loague Keith , Corwin Dennis L.
Published: July 2005

The word pesticide is a general term used to refer to the chemicals that are employed to control pests. In many areas of the world, successful agriculture depends on both pesticides and irrigation. The combination of repeated pesticide applications and irrigation over large nonpoint source areas often leads to leaching through the vadose zone and, subsequently, to groundwater contamination. For effective regulation and/or remediation, it is important to assess the vulnerability of valuable groundwater resources to contamination from widespread pesticide applications. The use of mathematical models for assessing groundwater vulnerability fills information gaps, identifies critical areas and pesticides for future monitoring, and provides the “what if” capability needed for both regulation and remediation. The uncertainty in chemical, climatic, and soil databases must be considered in assessing the vulnerability of groundwater to contamination from pesticides. Results from the Fresno case study, for the DBCP groundwater contamination problem in California's San Joaquin Valley, are discussed. The objective of the Fresno case study was to determine, from a simulation perspective, if label recommended nonpoint source applications were likely to be the principal source of the DBCP groundwater contamination in Fresno County. The relatively unique characteristic of the Fresno case study is that both the unsaturated near surface and the saturated subsurface were considered.
Head
Authors: Rasmussen Todd
Published: July 2005

The forces that cause water movement can be combined into a single measure, called the head, so that water moves from higher to lower head. This concept unites all forces (such as gravity, pressure, momentum, osmotic) so that predictions about the direction and magnitude of fluid movement can be obtained. Observations of head within aquifers are routinely used by scientists to develop a water table map in unconfined aquifers and potentiometric maps in confined aquifers. In many cases, the observed water levels in observation wells become a direct measure of head. Problems may develop, however, when the water density in the observation is not fresh. In these cases, a conversion to freshwater head is needed. Another difficulty develops when water levels change over time, such as when barometric pressure and precipitation cause short‐term fluctuations.
Laminar Flow
Authors: Hanspal Navraj S. , Sharma Raj
Published: July 2005

The prime objective of this text is to describe the elementary concepts involved in laminar fluid flows. In general, any flow is characterized by the continuous deformation of fluid particles and a corresponding internal state of stress. It has been experimentally established that, under laminar situations, the rate of deformation is directly proportional to local viscous stress. Laminar flows thus fall under the category of viscous flows. The principle laws that govern the motion of fluids are also discussed.
Leaching
Authors: Kelley David W.
Published: July 2005

Leaching is the phenomenon whereby a liquid (usually water) moves through a matrix (usually soil) from one location to another (usually downward with gravity), dissolving or suspending materials along the way. The liquid that migrates is referred to as leachate, and contains a mix of dissolved and/or suspended ions or compounds. These materials are either natural or anthropic and include dissolved salts, fertilizers, soluble minerals, organic materials, plant nutrients, or natural or synthetic chemicals. Leaching is affected by the amount, rate, direction, and quality of the leachate. Leachate movement is influenced by the hydraulic conductivity of the matrix, presence of impeding layers (aquitards or aquicludes), antecedent soil water content (saturated vs. unsaturated flow), osmotic or matric potentials, water holding capacity of the soil, and macropore flow. Leaching is governed by the processes of mass flow, diffusion, dispersion, sorption, and degradation. Leaching rates are highest in humid regions or on land under irrigation, and lowest in arid or permanently frozen regions. Most non‐industrial leaching occurs on agricultural land or under antiquated or modern landfills. Leaching accounts for the bulk of non‐point source pollution to groundwater, and subsequently to any surface water to which it is hydrologically‐connected.
Metal Organic Interactions in SubtitleDLandfill Leachates and Associated Ground Waters
Authors: Gonçalves Mário Abel
Published: July 2005

Landfills are important facilities for proper waste disposal in modern societies, but have some environmental problems. These are mostly due to leachate spilling and releasing through surface and groundwaters. Because organic compounds are the most important constituents of these leachates and have a wealth of reactive functional groups, their interaction with metals is of utmost importance to understand the mobility and bioavailability of these metals in the environment. Metal‐organic interaction is mostly characterized by complex formation and stability. Predicting metal‐organic complex stability is however, a difficult task, but the electronic configuration of metal cations may provide some insight on that problem based on the classification into hard‐ and soft‐sphere cations. On the other hand, landfill leachates are complex solutions where these interactions are likely to occur with a wide range of organic compounds, rendering individual interactions almost irrelevant. Besides, the number of cations studied in this particular environment is limited to Cu, Ni, Zn, Cd, Pb, and Cr. What has been shown is that, depending on the cation, they may be predominantly associated with colloidal and/or dissolved organic matter, in particular forming chelates with the organic compounds, or forming inorganic complexes as well as insoluble solid phases.
Mobility of Humic Substances in Groundwater
Authors: Buckau Gunnar
Published: July 2005

Humic substances are a relatively stable part of the global carbon inventory, originating mainly from decomposition of plant material but also marine organisms. In groundwater, the hydrophilic part of the total geochemical inventory is found. They originate from recharge or
in situ
generation by partial oxidation of hydrophobic sedimentary carbon sources, especially lignite sand. Because of their hydrophilic character and negative charge, they remain stable over long time periods and long transport times. This is especially true for the fulvic acid fraction with its smaller average molecular mass and higher oxygen functional group content than the complementary humic acid. Investigations in several types of aquifer systems show transport times up to 15,000 years and transport distances of more than 20 km. One exception is the salting out of the
in situ
generated fulvic acid inventory in brines in the vicinity of a salt dome. Variations in concentration, composition, and
14
C content of the aquatic humic substance inventory can give information over different recharge conditions, including climatic changes. Where no direct evidence can be given for the retention of aquatic humic substances, an ideal tracer behavior needs to be assumed. Consequently, they may play a key role in the transport of pollutants, including heavy metals and radionuclides.
Modeling Techniques for Solute Transport in Groundwater
Authors: Das Diganta Bhusan , Hanspal Navraj S.
Published: July 2005

Groundwater constitutes an important component of water supply systems for domestic use, industry, and agriculture. Due to increased use regularly above sustainable levels, groundwater quality often deteriorates. Contaminants in groundwater systems are introduced by hazardous industrial wastes, leachate from landfills, oil spills, agricultural activities, sites of radioactive waste repositories, and other sources. In most cases, the source of contamination is aboveground, and the contaminants pass through the unsaturated zone on their way to the saturated region.

The fundamental processes that govern solute mobility in groundwater have been studied and reasonably well understood for some time. Solute migration results from a variety of coupled physical, chemical, and biological processes. Owing to the complexities of natural soils and solute–soil–fluid interactions and frequently changing field conditions, modeling solute transport involves some degree of approximation. However, the modeling framework must retain the important aspects of real phenomena. It is also necessary for a reliable/realistic model to answer several relevant questions, such as, what is the purpose of the predictive calculations, what types of environments can be modeled, what level of precision is expected, and what are the advantages and disadvantages of the developed approach. To answer these questions while developing a model for solute movement in the subsurface, many issues must be considered.
Brine Deposits
Authors: Testa Stephen M.
Published: July 2005

Brines are warm to hot, saturated to nearly saturated, highly saline, ocean and lake waters, containing Ca, Na, K, and Cl and minor amounts of other elements, typical of pore fluids in restricted basins. From an oceanographic perspective, brine is seawater that, due to high evaporation rates or freezing, contains more than the usual amount of dissolved salts, typically about 35%. A brine lake is essentially a salt lake. Brine lakes, like the Dead Sea, the Great Salt Lake in Utah, the Mono Lake region in northern California, and the Salton Sea region in southern California, develop as a result of high evaporation rates in an arid desert that lacks an outlet to the ocean (Fig.1). The salt is derived from either minerals washed out of the surrounding watershed or from a geological deposit or area previously connected to the ocean.
Deep Soil‐Water Movement
Authors: Rasmussen Todd
Published: July 2005

Water movement above the water table, yet below the root zone, is predominantly downward because of gravitational forces. This vertical movement is frequently affected by lower permeability geologic units that divert water horizontally. Also, vapor‐driven transport of water can be important in very dry climates. Shallow soil‐water is affected by plant uptake of water, and also by evaporation from the soil surface. These processes are characteristic of unsaturated media, i.e., zones where the soil materials are not saturated with water. In these cases, the surface tension of water causes adherance to soil surface, and soil‐water pressures are generally negative. Each soil material has a distinctive relationship between the negative fluid pressure (or tension) and water content. The unsaturated hydraulic conductivity is lower than the hydraulic conductivity under saturated conditions because not all available pore space contributes to fluid flow. Deep soil‐water movement is also affected by macropores (large pores) that can provide preferential flow paths under very wet conditions, but may not significantly contribute to flow otherwise.
Phytoextraction and Phytostabilization: Technical, Economic and Regulatory Considerations of the Soil‐Lead Issue
Authors: Johnston Tracey , Datta Rupali , Sarkar Dibyendu
Published: July 2005

Lead is a common environmental contaminant, produced from multiple anthropogenic sources. The cost of traditional remediation techniques for lead‐contaminated soils is prohibitive. As a result, new technologies such as phytoextraction, the removal of contaminants from soil and water sources by plants, and phytostabilization, the immobilization of contaminants in the soil, are being examined as remediation alternatives for lead‐contaminated soils. Only a few plant species have been identified so far that can tolerate and accumulate lead partly because lead is relatively immobile in soils and has low phytoavailability. However, lowering the pH or the use of soil amendments or chelating agents such as EDTA can enhance the uptake of lead by plants. Lead is already relatively immobile in most soils, so phytostabilization is a promising remediation strategy. However, phytostabilization leaves the contaminant in the soil (albeit in an insoluble form), so long‐term monitoring is required to verify that the contaminant does not become soluble again. Although only limited studies on the economic viability of phytoextraction and phytostabilization have been done, the estimated costs are significantly lower than those of traditional methods.
Regional Flow Systems
Authors: Uliana Matthew M.
Published: July 2005

A
groundwater flow system
is a three‐dimensional entity that has the following components:

—a recharge area where water enters the flow system

—a discharge area where water exits the system

—boundary conditions and physical dimensions

When dealing with flow systems, we often differentiate between
local, intermediate,
and
regional
flow systems. The distinction is primarily a matter of scale; local flow systems cover a much smaller area than intermediate systems, which in turn are smaller than regional systems.
Regional groundwater flow systems
generally involve a large area (10
1
–10
2
 km), and usually contain several local flow systems, resulting in areas of local recharge as well as springs or other discharge features within the larger system. Often several different aquifers and geologic formations will be connected by a larger regional groundwater system.
Magnetic Water Conditioning
Authors: Ritchie Ingrid
Published: July 2005

Hard scale is a significant problem costing billions of dollars annually throughout the world in industrial, commercial, and residential equipment that utilizes heat transfer surfaces. The development and use of technologies that can help reduce hard scale and the use of vital energy, water, and other resources is critically important as society grapples with increasingly more common resource shortages and environmental pollution. One important green technology that can reduce scale that results from hard water in a wide variety of applications (including boilers, hot water heaters, cooling towers, and steamers) is permanent magnetic water conditioning. Magnetic water conditioning is a nonchemical treatment option that can be used as a replacement for most water‐softening equipment. It can also be used as a preconditioner to allow other water treatment technology to work more efficiently and last longer. Whether it is used as a primary treatment device or as a preconditioner for other technologies, magnetic water conditioning can reduce the use of hazardous chemicals, maintenance downtimes, and labor costs and can result in overall cost savings compared to other strategies for scale reduction or removal.
Bonding of Toxic Metal Ions
Authors: Peleka E. N. , Matis Kostas A. , Erwe T. , Mavrov V.
Published: July 2005

Worldwide environmental problems are becoming more and more acute. It is known that many specific industrial wastewater streams with large flows contain toxic metals in concentrations up to 500 mg/L, which have to be removed prior to water recycling, indirect discharge into a sewage system, or direct discharge into surface waters. Some examples are (1) rinse water in metal working enterprises, containing Cu, Ni, Zn, Sn, Cd, Pd, Ag, Al, Au, Cr, Mo, etc.; (2) rinse water in the semiconductor industry, containing Cu, Sn, Pb, Sb; (3) wastewater from the copper industry, containing As, Se; (4) other types of water in which the presence of toxic metals causes problems; (5) drinking water from ground water contaminated with As; and (6) mine water contaminated with different toxic metals (e.g., U, Ra, As).
Application of Microfiltration to Industrial Wastewaters
Authors: Erwe T. , Blöcher C. , Mavrov V. , Matis Kostas A.
Published: July 2005

The examination of membrane processes started mostly as a search for effective product separation that is crucial to economical operation in process industries. Certain types of materials are inherently difficult to separate, and their processing has become of increased importance in recent years, especially due to the growth of the biotechnological industry (1) This new technology using synthetic membranes for process separations has developed rapidly. Industrial membrane processes are classified according to the size range of materials, which they are to separate, and the driving force used in separation. The most common pressure‐driven process is microfiltration (often denoted as MF) (2). This technique separates a size range of 10–0.1 µm; typical examples of materials separated are small particles, large colloids, and microbial cells.
Evaluation of Toxic Properties of Industrial Effluents by On‐Line Respirometry
Authors: Samaras Petros
Published: July 2005

Industrial effluents often contain chemical compounds that have potential toxic properties which upon co‐treatment with municipal wastewaters may affect the operation of a wastewater treatment plant. Respiration measurements, corresponding to the estimation of oxygen uptake rate (OUR) of living microorganisms, may be used to evaluate the toxic properties of industrial wastewaters, estimate their biological treatability, and predict the impact on the performance of a wastewatewater treatment plant. Several commercial on‐line respirometric biosensors have been developed for monitoring various parameters such as carbon/nitrogen biological removal, anaerobic digestion, and activated sludge settling; these systems have common characteristics such as a simple measurement principle, low amount of chemicals required during their use, and the absence of a sample pretreatment step. On‐line biosensors may be used as early warning tools in treatment plants, to protect plant operation and to increase efficiency, contributing to the development of toxicity management plans, especially in plants treating industrial wastes.
Transpiration
Authors: Miyashita Koichi
Published: July 2005

Transpiration is the evaporation of water from the plant to the atmosphere. In case of open stomata, transpiration from a leaf is schematically outlined. Relationships among meteorological factors such as the wind speed and the solar radiation, physiological activities, and the transpiration are described. Some effects of transpiration on plants are also pointed out. One is to increase the absorption of minerals from the soil, and another is to decrease the leaf temperature to prevent a high‐temperature stress. For the plant canopy, the total of transpiration from plants and evaporation from the wetted surfaces of plants and soils is described as evapotranspiration. Transpiration and evapotranspiration from plant canopy has the different seasonal and diurnal patterns, depending on various climatological and meteorologicaly conditions. These quantitative data about transpiration and evapotranspiration from plant vegetations are very important for forestry and landscape management, irrigation management, and prediction of climatic change. Finally, some measurement methods of transpiration from the single leaf, the individual plant, and the canopy level are presented shortly.
Heat of Vaporization
Authors: Persaud Naraine
Published: July 2005

The thermodynamic basis for the Clausius–Claypeyron equation for liquid to vapor transition is developed and discussed with specific reference to the heat of vaporization (Lv) for water. Examples using the Clausius–Clapeyron, Antoine, and Richards equations for calculating Lv are presented.
Humidity—Absolute
Authors: Persaud Naraine
Published: July 2005

Using ideal gas assumptions, relationships for atmospheric humidity as a function of temperature are developed and discussed. The Clausius–Clapeyron, Richards, and Magnus–Teten equations for estimating the saturation vapor pressure (e*) for water as a function of temperature needed for practical application of these relationships are presented. Example calculations using these equations are included.