bluuebunny/crossref_metadata_2025 huggingface dataset:
Low Total Vitamin C Plasma Level Is a Risk Factor for Cardiovascular Morbidity and Mortality in Hemodialysis Patients
Authors: Deicher Robert , Ziai Farzad , Bieglmayer Christian , Schillinger Martin , Hörl Walter H.
Published: April 2005

Hemodialysis patients are prone to deficiency of vitamin C, which constitutes the most abundant nonenzymatic antioxidant in blood. Because antioxidants are involved in the pathogenesis of atherosclerosis, the authors examined the association of total vitamin C plasma level with cardiovascular outcomes in such patients. One hundred thirty-eight consecutive maintenance hemodialysis patients (median age 61 yr, 90 males) were enrolled in a single-center study. At baseline, routine laboratory parameters were recorded, and predialysis total vitamin C plasma levels were measured by high-pressure liquid chromatography. Patients were prospectively followed-up for the occurrence of a primary composite endpoint consisting of fatal and nonfatal major adverse cardiovascular events (MACE) and for all-cause and cardiovascular mortality. MACE occurred in 35 patients (25%) over a period of median 30 mo, and 42 patients (30%) died [29 cardiovascular deaths (21% of total)]. Using Cox proportional hazards modeling, adjusted hazard ratios for the occurrence of MACE were 3.90 (95% confidence interval [CI]: 1.42 to 10.67;

P

= 0.008) and 3.03 (95% CI: 1.03 to 8.92;

P

= 0.044) for patients in the lower (<32 μmol/L) and middle (32 to 60 μmol/L) tertile of total vitamin C levels, compared with patients in the upper tertile (>60 μmol/L). Hazard ratios for cardiovascular death were 3.79 (95% CI: 1.23 to 11.66;

P

= 0.020) and 2.89 (95% CI: 0.89 to 9.37;

P

= 0.076). Total vitamin C levels were not independently associated with all-cause mortality. This study concludes that low total vitamin C plasma levels predict adverse cardiovascular outcomes among maintenance hemodialysis patients. Future studies should address the potential protective effect of an adequate vitamin C supplementation.
Proliferation of Bone Marrow-Derived Cells Contributes to Regeneration after Folic Acid-Induced Acute Tubular Injury
Authors: Fang Te-Chao , Alison Malcolm R. , Cook Terence H. , Jeffery Rosemary , Wright Nicholas A. , Poulsom Richard
Published: April 2005

Studies of tissue from recipients of bone marrow transplantation or organ allograft suggest that bone marrow-derived cells (BMDC) may differentiate into a variety of nonhematologic tissues, including renal tubular epithelium. The aims of this study were to examine whether BMDC contribute to recovery after acute renal injury and to assess the effects of cytokine mobilization on regeneration. Female mice (6 wk old) were lethally irradiated and transplanted with male bone marrow (BM) cells and later assigned into control, folic acid-treatment, and folic acid-treatment with granulocyte-colony stimulating factor (G-CSF), and control with G-CSF. Tritiated thymidine was given 1 h before death. Kidney sections were stained for a tubular epithelial marker, Y chromosome (

in situ

hybridization), periodic acid-Schiff staining, and subjected to autoradiography. Renal tubular epithelial cells in S-phase were scored as female (indigenous) or male (BM-derived). This is the first report to show that BMDC can respond by engrafting the renal tubules and undergo DNA synthesis after acute renal injury. BMDC contributed to the renal tubular epithelial cell population, although most (90%) renal tubular regeneration came from female indigenous cells. Some evidence was found for cell fusion between indigenous renal tubular cells and BMDC, but this was infrequent and the significance and consequences of cell fusion in the kidney are unresolved. G-CSF treatment nearly doubled the frequency of thymidine-labeled BM-derived tubular cells and might facilitate the recovery of renal tubular epithelium.
Molecular Identification of Canine Podocalyxin-Like Protein 1 as a Renal Tubulogenic Regulator
Authors: Cheng Hsin-Yuan , Lin Yu-Yu , Yu Chun-Ying , Chen Jen-Yau , Shen Kuo-Fang , Lin Wei-Ling , Liao Hsin-Kai , Chen Yu-Ju , Liu Chen-Hsuan , Pang Victor Fei , Jou Tzuu-Shuh
Published: April 2005

GP135 is an apical membrane protein expressed in polarized MDCK epithelial cells. When cultured in three-dimensional collagen gel, MDCK cells form branching tubules in response to hepatocyte growth factor stimulation in a manner that simulates the embryonic renal development. During this process, GP135 displays transient loss of membranous localization but reappears at the cell surface when nascent lumen emerges from the developing tubules. Despite being used for decades as the canonical hallmark of apical surface, the molecular identity and the significance of the dynamic expression of GP135 during the tubulogenic process remain elusive. For exploring the function of GP135, the full-length cDNA encoding GP135 was obtained. Sequence alignments and features analysis confirm GP135 as a canine homolog of podocalyxin, confirming the finding of an earlier independent study. Immunohistochemical assays on canine kidney sections identified both glomerular and tubular distribution of GP135 along the nephron. Mutant MDCK cells expressing siRNA targeted at two regions of GP135 show defects in hepatocyte growth factor-induced tubulogenesis. Re-expression of full-length and an O-linked glycosylation abbreviated construct of GP135 could recapitulate the tubulogenesis process lacking in siRNA knockdown cells; however, a deletion construct devoid of the cytoplasmic domain failed to rescue the phenotype. In summary, the data identify the MDCK apical domain marker GP135 as a tubular form of podocalyxin and provide evidence for its importance in renal tubulogenesis.
Structure and Mechanism of Monoamine Oxidase
Authors: Edmondson D. E. , Mattevi A. , Binda C. , Li M. , Hubálek F.
Published: April 2005

Monoamine oxidases A and B (MAO A and MAO B) are mitochondrial outer membrane‐bound flavoproteins that catalyze the oxidative deamination of neurotransmitters and biogenic amines. A number of mechanism‐based inhibitors (MAOIs) have been developed for clinical use as antidepressants and as neuroprotective drugs. To facilitate the development of more effective and specific inhibitors, a detailed understanding of the structures and catalytic mechanisms of these enzymes is required. The recent development of high level expression systems for producing recombinant human liver MAO A and MAO B in
Pichia pastoris
has facilitated the determination of the three‐dimensional crystal structures of MAO B (up to 1.7 Å resolution) in complex with different reversible (isatin, 1,4‐diphenyl‐2‐butene) and irreversible inhibitors (pargyline,
N
‐(2‐aminoethyl)‐
p
‐chlorobenzamide, and
trans
‐2‐phenylcyclopropylamine). The binding of substrates or inhibitors to MAO B involves an initial negotiation of a protein loop occurring near the surface of the membrane and two hydrophobic cavities; an “entrance” cavity and an “active site” cavity. These two cavities can either be separate or in a fused state depending on the conformation of the Ile199 side chain, which appears to function as a gate. The amine function of the bound substrate approaches the
re
face of the bent and “puckered” covalent FAD through an “aromatic cage” formed by two tyrosine residues that are perpendicular to the plane of the flavin ring. No amino acid residues that could function as acids or bases are found near the catalytic site. The existing structural data on MAO B support previous QSAR results and are also supportive of a proposed polar nucleophilic mechanism for MAO A and B catalysis rather than the alternatively proposed single electron transfer (SET) mechanism.
Irrigation in the
U
nited
S
tates
Authors: Lasserre Frederic
Published: April 2005

The total amount of farmland, comprising both cropland and pastureland, is slowly decreasing in the United States at 71.2 million hectares (M ha) (176 million acres) in 1998, but irrigated lands kept increasing from 16.7 Mha in 1974, 19.8 Mha in 1982, 19.9 Mha in 1992, and 25 Mha in 2000. The geography of the increase in irrigated lands is contrasted. The national yearly increase for the period 1974–2000 is 1.57%, but east central and Atlantic states witnessed much stronger growth, well above 4%, on average, whereas Arizona, Montana, Nevada, Texas, Oklahoma, and Wyoming saw their irrigated lands shrink overall.
Landscape Water‐Conservation Techniques
Authors: Fender Douglas H.
Published: April 2005

When given information and technology, people will make the effort to conserve. Plant selection will have less impact on water use than either irrigation or soil preparation. Water budgets give consumers more options and personal choice, while providing an effective way to conserve water.
Microbial Quality of Reclaimed Irrigation: International Perspective
Authors: Alum Absar
Published: April 2005

Wastewater reuse has been practiced in different forms throughout the history of human civilization. Previously, sewage had been dumped in rivers and lakes or used locally to irrigate crops. Explosive population growth and diminishing fresh water resources around the globe have now made wastewater a valuable resource, especially in arid and semiarid areas of the world. The introduction of modern wastewater treatment processes has given new dimensions to water reuse. Reclaimed waters are commonly used for landscape or recreational irrigation (parks, golf courses, athletic fields, school yards, highway medians, and public and private lands) and agricultural crop irrigation (field crops, vegetables, orchids, and tree plantations).

Human feces, which may have microbial constituents as high as 10–30%, are one of the major sources of infectious and noninfectious agents found in municipal wastewater. Thus, wastewater can contain high concentrations of excreta‐related microorganisms. The principal microorganisms (infectious agents) that may be present in raw sewage can be classified into three broad groups: bacteria, parasites (protozoa and helminths), and viruses. During an outbreak, pathogen numbers in local sewage go up. More than 30 excreta‐related diseases of public health importance have been documented, and many of these are of specific importance in wastewater reuse schemes. Table 1 summarizes the major infectious agents potentially present in raw domestic wastewater and their respective diseases.
Microirrigation: An Approach to Efficient Irrigation
Authors: Chauhan Harenda Singh
Published: April 2005

Microirrigation, earlier known as Drip or Trickle irrigation is a highly efficient method of water application. It developed and expanded globally at a fast rate in the last two decades in more than 35 countries with maximum coverage in the United States. This is most appropriately applicable to widely spaced crops such as fruits, vegetables and field crops. Its different variations consist of surface trickle, bubbler, microsprinkler, spray, mechanical move, pulse, subsurface drip, all of which are covered under a single term microirrigation. In the present article, its advantages, components, system design, fertigation, automation and other aspects has been described. Also the extent of application to different crops, and in different countries, limitations, scope, research trends and strategies of promotion has been discussed.
Remediation of Pesticide‐Contaminated Soil at Agrichemical Facilities
Authors: Roy William R.
Published: April 2005

The remediation of contaminated soil also requires establishing some type of cleanup goals or objectives. Such objectives are used to determine whether the soil is “contaminated” in a regulatory context. Depending on the specific type, agrichemicals are subject to various physicochemical and biological processes that can reduce their concentrations in soil and groundwater. Unlike other common contaminants such as chlorinated hydrocarbons, agrichemicals areintentionallyreleased into the environment to promote plant growth and to limit the spread of weeds. A mixture of application‐rate equivalents and risk‐based processes to derive soil cleanup objectives have been promulgated in the Midwest. For example, the Illinois Department of Agriculture provides a default soil‐cleanup objective (SCO) for surface soil (0 to 12 inches) and subsurface soil (12 to 60 inches) for each major pesticide used in Illinois. A facility also has the option of developing site‐specific SCOs. These SCOs were derived from the application of soil screening levels (SSLs) developed by the U.S. Environmental Protection Agency. The resulting SCOs take into account the movement and chemical fate of a given chemical in soil–water systems. In the application of the SSL concepts, three physicochemical‐fate mechanisms are considered: dilution in groundwater, adsorption by soil organic matter, and volatilization. Degradation by biotic or abiotic mechanisms is not considered.
Salt Tolerance
Authors: Gupta Suresh K.
Published: April 2005

Salinity has adversely affected irrigated agriculture for thousands of years. The salt tolerance of a plant defined as the plant's capacity to endure the effects of excess salts in the m,edium of plant growth has a major role in managing salt affected lands found both under irrigated and non‐irrigated agriculture. Plants show both inter and intragenic differences in tolerance to salts. Absolute tolerance to salinity cannot be expressed explicitly because many edaphic and environmental factors influence salt tolerance in plants. Even the growth stage at which salt stress is experienced has a profound effect on salt tolerance. Although data are not sufficient to conclude but one would tend to agree to a statement that many crops and plants show increased tolerance with age. Amongst many criteria evolved to date to characterize relative salt tolerance of plants such as survival of the plants, vegetative growth, absolute yield and relative yield, the last one seems to be the most promising. A piecewise linear model proposed by Maas and Hoffman has been extensively used to prepare relative salt tolerance tables for most kind of crops such as herbaceous crops, vegetable and fruit crops, woody crops, ornamental shrubs, trees and ground cover crops. Salt tolerance characteristic of plants have played and would continue to play a role in the management of poor quality land and water resources for the benefit of mankind. It has been illustrated with the help of an example of sequential concentration model to manage poor quality water resource. Although attempts to make a headway in developing salt tolerant crops have been made but still many teething troubles are being experienced. The complexity of these problems rule out any major breakthrough on this front in a near future yet efforts in this direction seems to be well focused.

The literal meaning of tolerance is to endure, sustain, or put up with. Thus, the salt tolerance of a plant could be defined as the plant's capacity to endure the effects of excess salt in the medium of root growth. That plants can withstand a fair amount of salts without adverse effects is implicit in this definition. In fact, a fair proportion of salts in the growing medium is needed for good growth. There are instances where plant growth is stimulated at low concentrations of salts, and only thereafter, the yield starts declining. Apparently, the problem of soil salinity develops only when the salts accumulate in the root zone to an extent that it becomes harmful to the plants. The salt tolerance of a plant is also expressed in terms of the yield decrease expected for a given level of salinity compared to the yield under nonsaline conditions. Many times, salt tolerance and salt resistance have been used synonymously although, the two do not convey the same meaning. Salt resistance is a plant's ability to decrease or prevent the stress from penetrating into its tissues, but tolerance is the ability of the plant to eliminate, reduce, or repair the stress once it has already penetrated.
Soil Moisture Measurement‐Neutron
Authors: Babel Mukand Singh
Published: April 2005

The neutron probe is based on the principle of neutron thermalization. Hydrogen nuclei are nearly the same size and mass as neutrons and therefore, can scatter and slow neutrons. High‐energy (0.1–10 Mev.), fast (1600 km/s) neutrons emitted from a radioactive source, such as americium–beryllium or radium–beryllium are slowed and changed in direction by elastic collisions with atomic nuclei of hydrogen atoms in soil. This process is called “thermalization,” and the low‐energy (about 0.03 eV) neutrons, after collision, are called “thermal/thermalized neutrons.” The density of the thermal neutrons (thermal cloud of neutrons) depends on the soil–water content; the vast majority of hydrogen in soil is associated with water. Higher water content in soil leads to increased thermalization and, thus, a denser thermal cloud. A “slow neutron” detector is installed adjacent to the source (emitter) to measure the cloud density. The measurement is usually in the form of a “count ratio,” a higher count ratio denotes higher water content and vice versa. Thus, the density of thermal neutrons can be calibrated against the water content volumetrically basis (2).
Stomates
Authors: Ferreyra R. Andrés
Published: April 2005

Stomates or stomata (singular: stomate or stoma) are structures on the surfaces of plant leaves that allow gas exchange (transpiration, i.e., loss of water vapor, uptake of CO2, and emission or uptake of O2) between the interior of a leaf and the atmosphere.

Plant leaves are covered by a waxy layer, the cuticle, that prevents water loss from the cells on the leaf surface, or epidermis. The cuticle does not completely cover the leaves, however; it is interrupted by microscopic pores, surrounded by pairs of specialized guard cells. A stoma is a unit composed of a pore and its guard cells. Guard cells, unlike regular epidermal cells, usually contain chloroplasts (photosynthesizing organelles containing chlorophyll). In some plants, there are also additional, specialized subsidiary cells that differ in shape from regular epidermal cells and participate in the osmotic changes that drive guard cell movement.

Stomata can be found in all aboveground parts of plants but are more frequent in leaves. They usually appear on one (the lower) side of leaves but may appear on both. When stomata occur on the lower (abaxial) leaf surface, the plant is said to be hypostomatous; hyperstomatous plants have stomata only on the upper (adaxial) leaf surface, and plants with stomata on both surfaces are called amphistomatous. In this latter case, abaxial stomata are generally more numerous. The number of stomata per unit area is called the stomatal density. This figure may vary when plants are grown under different environmental conditions such as atmospheric CO2concentration.
Animal Farming Operations: Groundwater Quality Issues
Authors: Harter Thomas
Published: April 2005

Animal farming operations (AFOs) include feedlots, dairies, cattle farms, hog farms, chicken farms, and other facilities that raise or maintain a significant number of animals either seasonally or year‐round. With respect to groundwater quality, the fate, reuse, and disposal of animal manure produced at AFOs is of critical concern.

Groundwater benefits a wide variety of uses including production as drinking water for domestic/municipal use, production as irrigation water for agricultural/municipal uses, ecosystem support, and providing base flow in rivers and streams that is vital to the ecological health of these surface waters. AFO related groundwater quality issues result from potentially detrimental impacts during the collection, transport, storage, and land application of animal manure and animal wastes.

Potential groundwater pollutants originating from AFOs are (1) salts and nutrients, (2) bacteria that indicate the presence of pathogens, and (3) organic or inorganic chemicals specifically associated with the management of AFOs.
Weed Control Strategies
Authors: Newman J. R.
Published: April 2005

The control of nuisance vegetation in watercourses is often necessary to ensure adequate flood defense for surrounding land, to provide facilities for recreational sporting activity, to provide better angling environments, to aid navigation, on public health grounds, for industrial uses, and to maintain adequate water supply and quality. In recent years, weed control for conservation has also become necessary to protect native habitats from invasion by alien, introduced, or nonnative species.

Aquatic weeds are different from terrestrial weeds in that they are usually a normal constituent of the aquatic ecosystem. Aquatic plants become weeds when they grow to excess and become a nuisance by blocking channels, reducing flow, or preventing other normal uses of the waterbody. Increased urbanization has resulted in an increase in the number of nonnative species now considered aquatic weeds, due primarily to escape of plants from domestic situations. The increased recreational pressure on enclosed inland waterways has also resulted in greater demands for aquatic plant management.

During the last 50 years, there has been a dramatic change in the type of aquatic weed problem. Emergent weeds, such as reeds and rushes, and floating leaved weeds, such as waterlilies, were the major problem, but eutrophication since the Second World War, as a result of intensification of agriculture, increased urbanization, and consequent sewage treatment requirements, has resulted in a shift to problems caused by filamentous and blue‐green (cyanobacterial) algal blooms.
Economics of Residential Water Demands
Authors: Renzetti Steven J.
Published: April 2005

This entry examines what is known regarding the economic characteristics of residential water use and how this type of information can be applied in managing water resources. Understanding the economic dimension of household water use is important for several reasons. First and most importantly, all households on the planet share the need for access to potable water supplies. On the other hand, households have very different degrees of access to safe water. For most of North America and Europe, access to clean water is almost taken for granted by many households. In contrast, a great number of households in low‐income countries do not have access to reliable supplies of potable water. As the World Bank contends, “The challenge is enormous: one billion people still lack access to safe water, two billion lack safe sanitation. Slow progress is not acceptable, as more than three million children still die every year from avoidable water‐related disease” (World Bank Water Supply and Sanitation web‐site, September 1, 2001
http://www.worldbank.org/html/fpd/water/
). Second, the agricultural sector dominates global water use, but residential and industrial demands have grown much more rapidly during the twentieth century. Third, empirical evidence indicates that the amount of water used by a household is a complex function of a number of influences, including the price of water (both in monetary terms and in time costs), household income, and household characteristics (for example, the number of residents and water‐using appliances).
Nitrate Health Effects
Authors: Adelana Segun Michael Ade
Published: April 2005

Nitrate is a stable nitrogen (N) species under certain natural conditions and forms highly soluble compounds. These are peculiar features that allow nitrate ion to be transported in some groundwater systems to environments where it can be converted into other nitrogen species that either promote surface water eutrophication or are hazardous to humans, livestock, and the environment. Nitrate test results are usually expressed in milligrams per liter as either nitrogen (NO3‐N, sometimes written as plain N) or as nitrate (NO3).

The occurrence of high nitrate concentrations in groundwater is widespread, particularly from agricultural usage of fertilizers and animal manure or land disposal of domestic waste and wastewaters. Much research has been conducted to determine the amounts of nitrates in drinking water wells as well as in foods. Exposure to high doses of nitrate is generally perceived to be associated with adverse health effects in humans and other species. These range from infant methemoglobinemia, cancers, the ‘hot dog headache,’ and hypertension, to other adverse effects such as birth defects (congenital malformations) and spontaneous abortions. Most reported cases of infantile methemoglobinemia have been associated with the use of water containing more than 10 mg/L NO3‐N.
Gray Water Reuse in Households
Authors: Memon Fayyaz A. , Butler D.
Published: April 2005

Owing to growing population and uneven distribution and consumption of resources, existing water resources in many parts of the world are experiencing stress. Providing of potable water to meet this ever‐increasing demand may become even harder to achieve due to anticipated and emerging climatic change. One way of managing water demand is to reuse gray water.

Reusing gray water reduces the need to use potable water for non potable applications, and the water is effectively used twice before discharge to the sewer. The major reuse potential is for toilet flushing and garden watering that bring the benefits of conservation of water resources and relief of demand on both public water supplies and sewage collection and treatment facilities (1).

Gray water is a loosely defined term representing discharges from wash basins, baths, showers, dishwashers, and washing machines. This generally excludes wastewater from kitchen sinks and toilets, commonly known as black water. Gray water accounts for about 50% of total household water consumption.
Septic Tank Systems
Authors: Moore John E.
Published: April 2005

According to Wilson and Moore, a septic tank is an “underground vessel for treating wastewater from a single dwelling or building by a combination of settling and anaerobic digestion. Effluent is usually disposed of by leaching. Settled solids are pumped out periodically and hauled to a treatment facility for disposal.” When properly sited, constructed, and maintained, septic systems can provide a low‐cost environmentally responsible method of waste disposal. Improperly sited, constructed, operated, or maintained septic systems can, however, lead to water quality degradation and threats to public health.
Methods of Reducing Radon in Drinking Water
Authors: Robillard Paul D. , Sharpe William E. , Swistock Bryan R.
Published: April 2005

Since the late 1980s, radon has become a highly publicized health threat. This naturally occurring radioactive gas is seeping out of the earth's crust and into the basements of thousands of homes across the nation. Until recently, radon concerns have focused primarily on airborne radon; radon in drinking water was not considered a problem. Now, water tests reveal its presence, and many homeowners are asking water treatment dealers, “How can I reduce radon in my water supply?”
Virus Transport in the Subsurface
Authors: Azadpour‐Keeley Ann , Keeley Jack W.
Published: April 2005

In the United States alone, the estimated annual number of reported illnesses resulting from contact with waterborne pathogens was as low as one million and as high as seven million between 1971 and 1982, and 51% of all waterborne disease outbreaks due to the consumption of contaminated groundwater. It is estimated that approximately 20–25% of U.S. groundwater sources are contaminated with microbial pathogens, including more than 100 types of viruses. A literature review by Craun indicated that approximately one‐half of the surface water and groundwater sources tested contained enteric viruses. Even 9% of conventionally treated drinking water (coagulation, sedimentation, filtration, postfiltration disinfection using chlorine/ozone) tested positive for enteric viruses.

Although water‐transmitted human pathogens include various bacteria, protozoa, helminths, and viruses, agents of major threat to human health are pathogenic protozoa (CryptosporidiumandGiardia) and enteroviruses. Despite ample information regarding the fate of viruses in the subsurface, research on the persistency of pathogenic protozoa through passage in soil and groundwater is just now emerging. In the past, it was generally believed that pathogenic protozoa are confined to surface water. Contrary to that expectation, recent monitoring results from 463 groundwater samples collected at 199 sites in 23 of the 48 contiguous states suggested that up to 50% of the groundwater sites were positive forCryptosporidium, Giardia, or both, depending on the parasite and the type of groundwater source (vertical wells, springs, infiltration galleries, and horizontal wells).
Water and Human Health
Authors: Adelana S. M. A
Published: April 2005

Water is essential for life and health and has both cultural and religious significance. Water plays a vital role in transmitting infectious diseases, and 80% of diseases reported are directly or indirectly water‐related. Scarce and unclean water supplies are critical public health problems in many parts of the world. These have been identified as leading factors that will limit economic development in the near future. Based on projected population growth, the amount of water available for use per person per year is expected to drop annually.

Apart from the pressure of population growth on water resources, the supply of freshwater available to humanity is shrinking, in effect, because of increasing pollution. On the whole both water scarcity and water pollution pose serious health problems. Unclean water is by far the largest environmental killer around the world. Water shortages, polluted water, and unsanitary living conditions claim millions of lives annually via various water‐related diseases. About 60% of all infant mortality is linked to infectious and parasitic diseases most are waterrelated, and a large percentage of these diseases is attributable to inadequate water supply and sanitation.
Windmills
Authors: Holst Arthur M.
Published: April 2005

Windmills are machines that convert the force of the wind into energy that is applicable to various tasks, like pumping water. Windmills that are used to pump water use the energy generated by these mills to turn the gears that propel the pump. These types of windmills, sometimes referred to as wind pumps, have been used for centuries and continue in use around the world.
Combined Free and Porous Flow in the Subsurface
Authors: Das D. B. , Nassehi V.
Published: April 2005

The presence of a fluid layer adjacent to a porous medium is common in many environmental, chemical, mechanical and petroleum engineering problems. The flow behavior in the fluid layer is determined by the properties of the fluid (e.g., viscosity and density) and surface (e.g., pressure and shear) and body (e.g., gravity, and electric field) forces. However, flow in the porous medium depends additionally on the properties of the medium which include, among others, porosity and permeability.

In fluid dynamic analysis of groundwater systems, it is commonly found that water flows through combined free (nonporous) and porous pathways between surface and subsurface systems. Such coupled regimes may also be present due to construction of industrial utilities and structures in the ground. Important engineering processes that may involve combined free and porous flow domains are, for example, fluid losses/leaks from underground pipes and storage tanks in old gas works sites; dig‐and‐treat, pump‐and‐treat, and permeable reactive barrier technologies for groundwater treatment; and drilling/extraction of oil from underground reservoirs. However, in most cases, the associated transport phenomena are determined by natural hydroenvironmental conditions. These include, for example, combined surface and subsurface flow, lake–groundwater interactions, seepage through preferential flow channels and macropores, circulatory flows and rise and fall of groundwater, glaciology, and multiple karstic regions interfaced with granular porous sections. The subdomains in coupled flow systems are generally distinguished by an interfacial surface, which represents the transitional zone for contaminants/fluid mobility from free to porous sections or vice versa. To gain on understanding of the combined flow behavior, it is necessary to develop realistic methodologies for evaluating mass and momentum transfer across the free/porous flow interfaces.
Soil Pipes and Pipe Flow
Authors: Holden Joseph
Published: April 2005

Natural soil pipes are subsurface cavities of diameter greater than 1 mm that are continuous in length such that they can transmit water, sediment, and solutes through the soil and bypass the soil matrix. Soil pipes are larger versions of soil macropores. Pipes can be up to several meters in diameter, several hundred meters long, and occur in a broad range of environments. They are most common in soils that are subject to cracking in dry periods or are highly dispersible. Soils that have a significant amounts of swelling clays also commonly contain soil pipes (e.g., montmorillonite, illite, and bentonite). Piping is common in arid and semiarid areas where shrinking and desiccation cracking are common. Piping is also common in highly organic soils in humid uplands (e.g., blanket peats). However, soil pipes are found in virtually all climates, in organic and mineral soils, and on disturbed and undisturbed land.
Specific Capacity
Authors: Wilson Eric S.
Published: April 2005

The specific capacity of a well is the pumping rate of the well divided by the drawdown at that rate:

urn:x-wiley:9780471478447:media:gw1071:xm1

where

S
c

= specific capacity

Q

= constant pumping rate, and

Δh

= drawdown

Water well contractors often report specific capacity to characterize the performance of a well and use specific capacity to estimate the optimum depth for installing a pump to obtain the desired yield.

When taking measurements to compute specific capacity, the pumping rate should be constant, and the period of pumping should be sufficiently long that the rate of change in drawdown is small.
Specific Yield Storage Equation
Authors: Harter Thomas
Published: April 2005

Specific yield is part of the total porosity of a porous rock or sediment. The total porosity (total pore space) of a rock or sediment formation is much larger than the specific yield. Total porosity includes the fraction of pore space that is interconnected (called “effective porosity”) and porosity due to isolated pores. The effective porosity itself includes specific retention and specific yield. Specific retention is that volume fraction of water that is held back by adhesion and capillary forces, when an aquifer is drained. Specific yield is the amount of water that is actually available for groundwater pumping, when sediments or rocks are drained due to lowering of the water table.

Specific yield depends on the distribution of pores, their shape, and grain size. The larger the surface area of the rocks or sediment particles per unit volume (“specific surface area”), the more water adheres to these surfaces. This decreases the specific yield in favor of specific retention. Fine‐grained sediments have the largest specific surface area, the highest specific retention, and the lowest specific yield. Coarse‐grained sediments have a very small specific surface area; hence, the specific retention is small, and the specific yield is large. Specific yield typically decreases with depth due to compaction of sediments.
Steady‐State Flow Aquifer Tests
Authors: Chauhan Harendra S.
Published: April 2005

Groundwater studies are conducted to evaluate the occurrence, availability, and quality of groundwater. There are numerous practical applications like optimum development of groundwater basins, safe withdrawal, groundwater recharge, seepage from canals and reservoirs, and drainage that require knowledge of the hydraulic characteristics of aquifers. Two basic aquifer properties needed to make a quantitative assessment of such applications are transmissivity and storage coefficient which represent, in a general sense, its abilities to transmit and store water, respectively. The other hydraulic properties of an aquifer are hydraulic resistance, leakage factor, and drainage factor. Performing an aquifer test is an effective way of determining these hydraulic properties of aquifers. Steady‐state flow aquifer tests are conducted to determine transmissivity, hydraulic conductivity, and hydraulic resistance; more detailed unsteady‐state tests are conducted if other hydraulic properties are also to be evaluated. The objective of this article is to discuss steady‐state methods of determining aquifer characteristics.
Consolidated Water Bearing Rocks
Authors: Priyadarshi Nitish
Published: April 2005

Consolidated rocks (otherwise known as bedrock) consist of rock and mineral particles of different sizes and shapes that have been welded together by heat and pressure or chemical reaction into a rock mass. Aquifers of this type are commonly composed of one or more of the following rocks: sandstone, limestone, granite, or lava. Water flows through these rocks through fractures, gas pores, and other openings in the rock.

Consolidated rocks are usually classified according to their origin. There are three types: sedimentary, igneous, and metamorphic.

Sedimentary rock is formed by the deposition of material suspended in water; the material may have been material weathered from older rocks, plant or animal remains, or precipitated chemicals. Important types of sedimentary rock aquifers include sandstone, carbonate rock, and conglomerate.
Subsurface Drainage
Authors: Chauhan Harendra S.
Published: April 2005

The basic reason for agricultural lands to be affected by waterlogging and salinity is the inadequacy of the natural drainage system to handle the water that reaches the land either by natural or artificial means. Under such situations, an artificial drainage system has to be provided. The meaning of land drainage varies in different regions and contexts. A geographer or a surface hydrologist may use it to mean the pattern of natural watercourses in a hilly area. A pedologist may think in terms of the permeability of a poorly drained or well‐drained soil. In Peru, engineers interpret drainage as reconstruction of natural waterways rather than removal of water. In Canada, it may mean reclamation of marshland for agricultural or urban development. In Holland, a Dutch farmer may use it for the installation of drainpipe in the soil. Thus, in different areas, this term implies different meanings and objectives. If the land use is primarily agricultural then land drainage could be defined as the establishment and operation of a system by which the flow of water from the soil is enhanced, so that agriculture can benefit from the subsequently reduced or controlled water level in the soil. Agricultural land drainage aims at reclaiming and conserving land for agriculture, to increase crop yields, to permit cultivating more than one crop in an area, and to reduce the cost of production.
Viscous Flow
Authors: Hanspal Navraj S. , Nassehi Vahid , Das Diganta Bhusan
Published: April 2005

This text describes the elementary concepts of viscous fluid flow. The principal laws that govern the motion of fluids are also discussed. From our common experience, we know that fluids deform under the action of external forces. The deforming forces and rate of deformation are related to each other through a proportionality constant known as the coefficient of viscosity. The value of this constant depends upon the chemical identity, material properties, and thermodynamic state of a given fluid. To develop a theory that shows how viscosity affects fluid dynamics, one must understand the relationships between stress and the rate of strain. The outlines given in this article provide basic concepts of viscous flow. For more detailed analysis, the reader should consult specialized texts on this topic. Some of these texts are listed in the references at the end of this article.
Water Dowsing (Witching)
Authors: Commander David P.
Published: April 2005

‘Water dowsing’ is the supposed ability to locate underground water using a simple hand‐held device such as a forked stick, bent wires, or a plumb bob. ‘Dowsing’ is the general term applied to ‘divining’ for objects or materials concealed beneath the ground. Divining, or divination, implies a supernatural intervention and has been practiced for at least 2000 years for a variety of purposes. Water dowsing is also known as water witching.
Water Well Drilling Techniques
Authors: Jacobs James A.
Published: April 2005

Water well installation, for groundwater monitoring projects or for water supply wells for irrigation or human consumption involves a variety of drilling techniques. Rig selection is related to accessibility, time and cost of project, sediment type (consolidated rock or unconsolidated soils), sample type (undisturbed vs. disturbed), and sample integrity. For environmental projects, designing wells and evaluating groundwater also involves assessing the soil, sediments, or rocks above and below the water table.
Darcy's Law
Authors: Holden Joseph
Published: April 2005

Darcy's law is a mathematical relationship originally determined by Henry Darcy in 1856 that permits quantification of fluid flow through porous media. Many sophisticated theoretical and practical derivations have been based on Darcy's law, and it has become the foundation for quantitative groundwater flow science and soil physics. In its most useful form, the formula can be used to calculate the amount of water (or other fluid) flowing through a given cross‐sectional area of a porous substance and equates volumetric discharge per unit time (q) to the product of area (A), hydraulic gradient (I = change in head per unit length) and a coefficient (K = saturated hydraulic conductivity). In its simplest terms, the relationship may be expressed asq = KIA.
Drawdown
Authors: Moore John E.
Published: April 2005

According to Wilson and Moore, drawdown is the lowering of the water level in a well as a result of withdrawal. Drawdown data are collected to evaluate the performance of the well and to determine the aquifer's hydraulic character (transmissivity). Drawdown measurements also provide information on the well efficiency and performance. For example, measurements can be used with well discharge data to detect deterioration of the well screen.

The drawdown in a pumping well is the sum of head loss factors. Some of the factors are natural processes, head loss in the aquifer, loss in the damage zone (well drilling), well development, and turbulent loss in the filter zone. The damage zone consists of drilling debris, filter cake, and drilling fluid.
Environmental Isotopes in Hydrogeology
Authors: Adelana S. M. A.
Published: April 2005

In the last three to four decades, environmental isotopes have contributed immensely to studies and investigations in hydrogeology, complementing physical and chemical hydrogeology. Many hydrogeologic studies use stable isotopes of the water molecule to determine groundwater quality, origin, recharge mechanism, and rock–water interaction. A goodly number of the applications of environmental isotopes in hydrogeology have been in the arid and semiarid areas of the world, where water scarcity is most acute and poses constraints on economic development. A substantial amount of basic data and results of applied field investigations have already been published on applications of different isotopes for hydrologic purposes.

Environmental isotopes provide indications of groundwater age and serve as natural traces for groundwater provenance. Stable isotopes of carbon, boron, nitrogen, and sulphur (i.e.,
13
C/
12
C,
11
B/
10
B,
15
N/
14
N, and
34
S/
32
S) can give valuable information about reactions involving these elements and can also serve as pollution tracers. On the other hand, radioactive isotopes of some of these elements decay, providing us with a measure of the circulation time and, invariably, groundwater renewability. The most common of the radioisotopes, carbon‐14, is used to estimate groundwater residence time. Isotopes of the uranium series (
234
U,
238
U,
226
Ra, and
222
Rn) are also useful tracers in isotope hydrogeology but are often not precise enough to establish the age of groundwater due to mineral–water interactions.
Field Capacity
Authors: Skopp Joseph
Published: April 2005

Storage of soil water is important to soil flora and fauna, to hydrologic processes, and to a variety of soil physical properties. One element of soil water storage is an upper limit on water that is available for plant use, referred to as “field capacity.” This entry provides a history of the concept, its relation to soil water holding properties, predictive techniques for field capacity, applications, and failures of the field capacity concept.

Early researchers of plant water relations quickly realized that in water limited regions, the ultimate crop yield depended not only on the amount of rainfall received but on what portion of that rainfall was usable. Three key factors could reduce the usefulness of rainfall: runoff, drainage below the root zone, and evaporation. The net effect of rainfall, runoff, and drainage results in retention of water in the root zone. Evaporation and transpiration reduce this retained water. This retention was studied by Veihmeyer and Hendrickson. The concepts developed by Veihmeyer and Hendrickson provide a means to evaluate whether a soil retains sufficient water to support a particular crop.
Fluoride Contamination in Ground Water
Authors: Jain Chakresh K.
Published: April 2005

Fluoride occurrence in ground water is a natural phenomenon, influenced by the local and regional geological setting and hydrogeological conditions of the region. Fluoride content much higher than the maximum permissible limit has been found in many regions throughout the world. The problem assumes more significance in India and other developing countries because a major portion of the population that lives in rural as well as urban areas have to depend on available groundwater resources for their day‐to‐day requirements. An estimated 62 million people in 17 out of 32 states are affected with dental, skeletal, and/or nonskeletal fluorosis in India. The extent of fluoride contamination varies from 1.0 to 48.0 mg/L.
Geological Occurrence of Groundwater
Authors: Moore John E.
Published: April 2005

The occurrence, movement, and storage of groundwater are controlled by geology. The geologic factors that control groundwater are petrography, stratigraphy, structure, geomorphology, lithology, and thickness. The petrography of a given rock type controls the porosity and permeability. Porosity defines the storage capacity of an aquifer. There are two types of porosity: primary and secondary. Primary porosity, such as pores between sand grains, is created when rocks are formed. The shape, sorting, and packing of grains determine primary porosity. Sedimentary rocks are poorly sorted when the grains are not the same size creating spaces between the larger grains that are filled by smaller grains. Secondary porosity such as joints, fractures, and solution opening, is formed after the rock has been deposited. The number and arrangement of fracture openings and the degree to which they are filled with fine‐grained material control secondary porosity.