bluuebunny/crossref_metadata_2025 huggingface dataset:
Mitomycin C: An effective adjunct in the treatment of Ocular Surface Squamous Neoplasia
Authors: Verma Neha , Jawaid Qamar
Published: December 2019

A 40 year old female patient presented with a mass in the right eye, foreign body sensation and redness in the right eye for 6 months. Examination revealed a mass in the interpalpebral area, located in the superonasal quadrant, involving the bulbar conjunctiva and cornea. The mass was papillomatous, having a strawberry appearance, with multiple feeder vessels and was sharply demarcated. Visual acuity in the right eye was 6/6p, with full range of ocular movements. The left eye with a visual acuity of 6/6p was normal. AS-OCT performed revealed hyper-reflectivity and a thickened epithelium in the right eye. Histopathological examination confirmed it to be an infiltrating squamous cell carcinoma with moderate differentiation. The lesion was subjected to a wide excision together with intra-operative Mitomycin C (MMC) used in a concentration of 0.04%. Two 1 week courses of topical MMC 0.04% were given post-operatively. The patient was examined at 6 monthly intervals and no recurrence has been observed till third follow-up.

Conclusion: Mitomycin –C is an effective adjuvant in the management of OSSN.
Synthesis and Reactivity of Bora‐ and Borata‐Benzenes
Authors: Krummenacher Ivo , Schuster Julia K. , Braunschweig Holger
Published: December 2019

Since their discovery almost 50 years ago, boratabenzenes have become widely studied systems at the interface of organic, inorganic, and materials chemistry, mainly due to their use as stabilizing ligands for organometallic complexes. Together with their neutral analogues, the borabenzenes, this chapter provides a comprehensive and structured overview of the various synthetic methods for their construction. In addition, the conceptually different approaches to their corresponding metal complexes receive detailed review. The second part addresses the multifaceted reactivity of these aromatic boron heterocycles by outlining differences between the metal‐free and ‐bound forms.
Discourse Analysis for the Second Language Writing Classroom
Authors: Paltridge Brian
Published: December 2019

This entry discusses discourse features of texts that students need an awareness of in order to produce writing that meets the requirements and expectations of the particular audience at which it is aimed. Key notions discussed include genre, discourse community, information flow, and patterns of cohesion. Suggestions are made for how these notions can be addressed in second language writing classrooms.
Task Planning and Task‐Readiness
Authors: Bui Gavin , Teng (Mark) Feng
Published: December 2019

This entry introduces readers to the well‐researched construct of task planning and its more recent extension—task‐readiness—in task‐based language teaching. It starts with a rationale for various kinds of task planning conditions (e.g., extra planning time) and task characteristics (e.g., task structures) as task pedagogy. These task conditions and characteristics could be interpreted as implicit and explicit task‐preparedness, which form the two broad dimensions of task‐readiness. Then, the six types of task‐readiness conditions are delineated with a brief introduction to relevant research findings. It concludes with a discussion of pedagogical considerations in implementing task‐readiness, such as its objectives, its relevance to task sequencing in curriculum, and its implications for test fairness.
Mistreatment of Teachers
Authors: Blase Jo , Blase Joseph J.
Published: December 2019

This entry focuses on the problem of mistreatment of teachers by school principals. A brief conceptual overview of workplace mistreatment is presented. This is followed by a review of published studies of school principal mistreatment/abuse of public school teachers and a description of principals' abusive behaviors and their effects on teachers. A discussion of the implications of the problem of mistreatment/abuse for teachers, principals, and leadership education is also included. The entry concludes with a description of the benefits of transformational and instructional school leadership.
Willingness to Communicate
Authors: Ducker Nathan
Published: December 2019

The act of communicating in a second language has become an important methodological consideration and educational objective in many classrooms around the world. To increase the likelihood that communication will take place, both inside and outside of the classroom, teachers are encouraged to promote students' propensity to engage in communication – known as their “willingness to communicate” (WTC). This entry explains the arguments for developing students' WTC, various factors that play a role in enhancing or restricting a learner's WTC, and practical suggestions that educators can incorporate into their curricula, lesson plans, and classroom management.
Structure and Properties of Water in its Various States
Authors: Chaplin Martin F.
Published: December 2019

Water is a unique substance with properties that are not predictable from those of other materials. It has a complex phase space where all of its physical and structural forms possess unexpected properties. Mostly, these are consequences of the ability of the water molecule to form strongly hydrogen‐bonded intricate structures. The extensive hydrogen bonding provides water with the ability to transfer protons and electrons rapidly between the water molecules and to produce positively charged hydrogen ions and negatively charged hydroxide ions. In the many solid phases, each water molecule forms exactly four hydrogen bonds in a tetrahedral arrangement with two hydrogen atoms near each oxygen atom. This arrangement is also present, if much more loosely, in liquid water, where the overall structuring is far more complex. Such liquid water behaves as though it is a mixture of two liquids that change relative composition with variations in temperature and pressure. The properties of liquid water are particularly affected at low temperature when supercooled and at very low temperatures when water glasses are formed. Even gaseous water is affected by this hydrogen bonding.
Hydrogen Production from Wastewater by Biochemical Methods
Authors: Ramprakash Balasubramani , Karuppan Muthukumar
Published: December 2019

The environmental impacts associated with fossil fuels and depletion of their resources motivated the development of alternate fuels. Hydrogen is an attractive alternate fuel with high heating value and no environmental impact. Although hydrogen is majorly produced by steam reforming, biochemical production especially from carbohydrate rich wastes is of great interest. Hydrogen production from these wastes is carried out by indirect/direct biophotolysis, dark fermentation, two‐stage fermentation and photofermentation. The major constraints of these processes are low hydrogen evolution rate and less yield at large scale. However, effective pretreatment of substrates and inoculum maximize the yield of hydrogen. The factors influence the hydrogen production include nature of microorganism, biochemical process/reactor, temperature, pH, ionic strength, hydraulic retention time, hydrogen and carbon dioxide partial pressure, organic acid concentration, and C/N ratio. The commercial exploitation of biohydrogen production is hindered by lack of high potential microorganism and bioreactor. Hence, it demands multidisciplinary research to understand the fundamental underlying principles besides the development of microbial strains for industrial applications.
Advanced Reduction and Oxidation–Reduction Processes for Water Treatment
Authors: Batchelor Bill
Published: December 2019

Oxidation–reduction reactions are important processes for water treatment because they chemically change contaminants, rather than only transfer them from the water phase. However, the rates of many oxidation–reduction reactions limit their use as treatment processes. This limitation can be overcome by using highly reactive free radicals as the chemical reductant, and treatment processes that do this can be called advanced reduction processes (ARPs). Treatment processes that rely on both oxidizing and reducing radicals can be called advanced oxidation–reduction processes, and both are similar to advanced oxidation processes that apply oxidizing radicals to water treatment. This article reviews a number of applications of ARPs and summarizes the characteristics of some AORPs. ARPs have been applied to a wide range of contaminants including halogenated organics and oxidized inorganic compounds. The effects of important process variables such as incident photon flux, reagent concentration, target compound concentration, and solution pH are reviewed for ARPs, and a simple kinetic model is presented that describes much of their behavior that has been observed. The basic aspects of two important AORPs (electron beam irradiation and photocatalysis) are discussed, and a kinetic model describing the dose coefficient for electron beam treatment is presented.
Sensor Networks for Dynamic Control of Combined Sewer Systems
Authors: Montestruque Luis
Published: December 2019

Combined sewer overflows (CSO) are discharges of raw untreated sewage into rivers, lakes, and oceans near cities where sanitary sewage and stormwater are transported in the same pipe network. There are more than 700 cities in the USA releasing more than 800 billion gallons of raw sewage per year. Recent advances in sensor networks, data analytics, and control systems now enable utilities to dynamically manage their sewer systems to maximize conveyance, storage, and treatment and subsequently reduce overflows. This article describes the design and implementation of a sensor network used to mitigate combined sewer overflows in South Bend, Indiana, USA. The sensor network consists of 150 sensors covering a sewer‐shed area of 40 square miles. The system, called CSOnet, dynamically controls eight throttle valves and three stormwater basins to maximize treatment, storage, and conveyance of the water collection system. The control system uses a highly distributed agent‐based control that has been able to significantly reduce CSO volumes.
Polymer–Nanocomposite Membranes for Water Separations
Authors: de Lannoy Charles‐François
Published: December 2019

The use of nanoparticles to make nanocomposite membranes for water treatment spans a range of development with the majority of materials existing at lab scale, some having been piloted, and a select few at commercial scale. As such, the use of nanomaterials in this field is still in the early stages. There is a large parameter space to explore, which includes the many types of polymers used in membranes, the wide range of membrane types used in water separations, the great variety of nanomaterials and their properties, and the multitudinous ways in which nanomaterials can be added to polymers. Determining which polymer nanoparticle combination will deliver substantially improvement over the bare polymer is challenging, but attempting to predict how nanomaterials will impact the desired membrane and flux characteristics when incorporated into a polymer and formed into a membrane is even more difficult due to the complex thermodynamics and kinetics that occur between polymers and nanoparticles during membrane synthesis. Further, optimizing the interactions of nanoparticles with polymer systems is not trivial, but is critical to translating the nanomaterial properties to the polymer matrices in order to produce enhanced membranes. These challenges are opportunities to produce nanocomposite membranes with enhanced practical applications.
Hollow Fiber Nanofiltration Membranes for Water Treatment
Authors: Sengur‐Tasdemir Reyhan , Turken Turker , Urper‐Bayram Gulsum Melike , Ates‐Genceli Esra , Tarabara Volodymyr V. , Koyuncu Ismail
Published: December 2019

Global drinking water crisis is a major driver behind the continued progress in the field of water treatment and water quality control. Separation by synthetic membranes is now well established as one of staple water treatment technologies capable of delivering high quality water. Nanofiltration (NF), in particular, occupies an important niche in the family of membrane separations as a key drinking water treatment method. Owing to its lower energy consumption, NF replaces reverse osmosis in applications such as water softening and removal of natural organic matter. This article describes hollow fiber nanofiltration (HF NF) membranes as applied to drinking water treatment. A brief introduction to the hollow fiber technology is followed by an overview of HF NF fabrication methods and examples of HF NF applications in water treatment. We conclude by discussing future prospects of this increasingly important type of membranes.
Mine Waste Effects on Water and Soil in Native American Land in WesternUSA
Authors: Cerrato José M. , DeVore Cherie L. , Velasco Carmen A.
Published: December 2019

The legacy of mining activities on Native American land has resulted in an extensive number of sites with elevated metal concentrations in water and soil; many of these sites have received limited or no remedial action. The reclamation and cleanup of these sites represents a major burden for communities, and authorities at the tribal, state, and federal levels. The limited knowledge of the characteristics of these sites limits the ability to adequately assess the risk to metal exposures among communities living near these sites and develop feasible remediation alternatives. This article attempts to critically synthesize the state of the problem and provide an overview of the existing knowledge related to the occurrence, transport, and remediation of metals in these abandoned mine waste sites. The physical and biogeochemical aspects reviewed in this article have relevant implications for Native American communities, decision‐makers, stakeholders, and environmental scientists.
Hydrological Modeling of Climate Change Impacts
Authors: Hakala Kirsti , Addor Nans , Teutschbein Claudia , Vis Marc , Dakhlaoui Hamouda , Seibert Jan
Published: December 2019

Hydrological climate change impact modeling is a commonly used approach to quantify potential future changes in streamflow. In this article, we present an introduction to the main steps involved in the production of such streamflow projections. We review commonly used modeling approaches to quantify climate change impacts on water resources, describe the main sources of uncertainty in hydrological projections and how to characterize them, and discuss best practices. The supplementary material includes a guide to perform typical data processing tasks involved in the production of hydrological projections. We also provide material to support teaching activities related to hydrological climate change impact modeling. The goal of this article is to support studies on climate change impacts on hydrological systems by providing guidance on working with the climate‐hydrology modeling chain.
Water Discharge Permitting in the United States and the European Union
Authors: Russell David L.
Published: December 2019

The US and the EU have very different permitting systems for aquatic discharges. While they operate on different philosophies, there are a number of similarities in their approach to regulation. Both approaches establish water quality goals, but the EU and the US apply different approaches to regulation. In particular, the EU and US employ substantially different enforcement strategies. This article explains the differences in philosophies and policies for regulation of water discharges.
Ship‐Mounted Acoustic Doppler Current Profiler (ADCP): Characteristics and Field Applications to Measure Coastal Hydrodynamics
Authors: Ribotti Alberto , Borghini Mireno , Satta Andrea , Magni Paolo
Published: December 2019

The Acoustic Doppler Current Profiler (ADCP) is an oceanographic instrument used to measure water currents in different aquatic environments. In this article, we provide the main characteristics of the ADCP and describe, for the first time in the Gulf of Oristano (W‐Sardinia, Italy), a field application to characterize the 3D circulation of shallow waters. Current data were acquiredin situalong several transects from the water's surface to the sea bottom during calm weather and good sea conditions and compared to numerical studies. This article reveals a predominantly clockwise circulation with water entering the Gulf from one Cape and exiting from the other, and a small anticlockwise eddy in the inner northeast sector of the gulf. Outside the gulf, the current was directed toward the southeast at the surface, directly forced by the wind, and toward the northeast below the surface. The collection of such hydrodynamic data allows us to verify operational numerical forecasting ocean systems implemented at larger spatial scales. Furthermore, the ease of use of the ADCP and the high quality of the data acquired demonstrate the feasibility of this system on any vessel of opportunity, since environmental monitoring assessment and Blue Economy implementation require high‐resolution data especially in coastal areas.
Hot Hand Fallacy: A Contagious Misinterpretation in Water Resources Sectors
Authors: Zolghadr‐Asli Babak , Bozorg‐Haddad Omid , Chu Xuefeng
Published: December 2019

Water development is one of the key factors required to achieve sustainable development, poverty reduction, and even equity. This laborious, yet time‐consuming task may require in‐depth investment by public sectors. There is a fallacious school of thought better known to scholars as the hot hand fallacy, however, that could consequently jeopardize water resources sectors. The core concept of this fallacy is the misjudgment of the fluctuation of a random sequence, by assuming that a system would more likely perform desirably due to its previous streak of successful performances. This article intends to shed light on this phenomenon and its potential threat to water‐related sectors, and finally, demonstrate a few ostensible remediation actions, which could potentially minimize the risk of such misinterpretation of random‐based events.
Hydropower in Climate Change
Authors: Zolghadr‐Asli Babak , Bozorg‐Haddad Omid , Chu Xuefeng
Published: December 2019

While many would turn to renewable resources to mitigate the adverse impacts of over‐exploitation of fossil fuels, the fact of the matter is that if the design, operation, and management of such renewable resources are not executed with great care and consideration, they may do more harm than good. In this article, hydropower, as one of the most important known renewable resources, was investigated under the potential influence of climate change. Through a thought‐provoking discussion, it is demonstrated that while a proper and logical use of this resource could mitigate the adverse impact of climate change; a false design and/or management technique would even cause additional economic and ecological harm.
Climate Change and Extreme Events
Authors: Ramis Climent , Cardell Maria F. , Amengual Arnau , Romero Romualdo , Homar Victor , Alonso Sergio , Jansa Agusti
Published: December 2019

Observations reveal increases in the average temperature of the Earth since the early twentieth century. The global distribution of this warming is discussed in this article. The variation observed in the spatial distribution of precipitation is also shown, indicating a decrease in specific equatorial zones as well as in the Mediterranean. Variations in the spatial distribution of temperature and precipitation extremes are described. Results of atmospheric and oceanic global circulation models, considering multiple green‐house gas concentration scenarios of the IPCC AR5 are shown. Results report a general increase in temperature, especially in the Arctic. Regarding precipitation, an increase is detected in the tropics and in the mid‐latitude land areas, and a substantial decrease in the Mediterranean. Regional climate model results for Europe derived from the EURO‐CORDEX project are discussed in detail. They show how average and extreme precipitations and temperatures at the end of the twenty‐first century suffer important increases, with notable differences between the northern and the southern countries.
Deep Soil Water Movement
Authors: Rasmussen Todd C.
Published: December 2019

Water movement between the root zone and the water table is predominantly downward due to gravity. This vertical movement can be redirected laterally by low‐permeability layers (e.g. clays, indurated media) that divert water horizontally. Also, vapor‐driven transport of water can be important in dry soils. 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, surface tension causes water to adhere to soil surfaces, 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 provide preferential flowpaths when saturated and promote evaporation when drained.
Hydraulic Head
Authors: Rasmussen Todd C.
Published: December 2019

The hydraulic head (or total head) is an indicator of fluid energy expressed in units of length, such as meters or feet. Hydraulic head combines all forces (e.g. gravity, pressure, inertia, surface tension, solute concentration, fluid density) that cause water movement in many hydrologic systems, including surface water, soil water, and groundwater. The
hydraulic gradient
(i.e. the slope or spatial change in hydraulic head) is used to find the magnitude and direction of fluid flow, where water flows from high‐to‐low head. The temporal change in the hydraulic head is used to estimate changes in water storage. While the water surface elevation in streams and wells can be used to approximate the hydraulic head, water levels must be corrected for water velocity, dissolved‐ and suspended‐solid concentrations, barometric pressure, and other factors.
Specific Gravity
Authors: Rasmussen Todd C.
Published: December 2019

The
specific gravity
is the observed density of a material divided by a reference value, usually water at its maximum density, i.e. 1 kg L
–1
. The specific gravity varies with fluid composition and temperature, as well as the amount of dissolved and suspended matter within them. Well construction relies on the large specific gravity of drilling muds to prevent the collapse of borehole walls in unconsolidated media. The
specific weight
is a related measure that is the product of the fluid density and the gravitational constant. These measures are used to find the
freshwater head
in the water column when using pressure measurements.
Wetland Value and Protection Strategies
Authors: Kramer Elizabeth
Published: December 2019

Wetlands are essential in providing water‐related ecosystem services, such as clean water for drinking, water for agriculture, flood control, and cooling water for energy. In conjunction with erosion control and sediment transport, they contribute to land formation and resiliency to storms. Yet, global wetlands continue to be degraded or lost due to agricultural production, urban development, and pollution. In many cases, policies and decision do not account for the economic value that wetlands provide through their interconnectedness with other terrestrial and aquatic ecosystems. Regulation of wetland protection is often limited to developing countries and, in some cases, lacks the enforcement needed to restore and protect wetland systems. Valuing of wetlands first requires an understanding of the benefits and the risk to loss of wetlands. Understanding the benefits first requires measuring the status and trends of wetland ecosystems as well as identifying and measuring the goods and services provided by wetland ecosystems. This information is used to link values and benefits with policies and decision‐making.

This article provides an overview of the status and trends of global wetland, describes the connection to wetland ecosystem goods and services, and valuation techniques for these goods and services, and discusses tools for protecting wetlands and their associated benefits.
Thermodynamics of Freshwater Chemistry
Authors: Maurice Patricia A.
Published: December 2019

This article introduces some of the fundamentals of thermodynamics as applied to water chemistry, specifically focusing on freshwater systems. Chemical thermodynamics is an important approach for describing systems at equilibrium, and it has been used extensively in many areas of environmental science and engineering. Even though many complex natural systems are not at equilibrium, this approach allows one to predict reactions that should occur spontaneously, such as which minerals are potentially dissolving and which precipitating within a given environmental setting.
Background Concentration of Pollutants
Authors: Gonçalves Mário A.
Published: December 2019

Determining background concentration of pollutants in surface and groundwaters is a particularly difficult task, but a most important one because of the definition of water quality standards. A major difficulty resides in the dynamic, transient, nature of water systems and in pollutant dispersion and persistence, making it difficult to define the range of background and baseline concentrations based in a limited number of samples. The factors that determine the water chemistry are briefly discussed with some relevant examples, because it is essential to understand global water chemistry. A distinction between background concentration of inorganic and organic pollutants is made, which is because the former can have both natural and anthropogenic derived sources, whereas the latter are exclusively because of anthropogenic activities. Current practice determines background (as well as baseline) concentrations using a representative set of water samples and applying statistical techniques jointly with historical data, down‐gradient profiles, extrapolation, and geochemical modelling.
The Geochemistry of Acid Mine Drainage
Authors: Viadero Roger
Published: December 2019

Acid mine drainage (AMD) is created when iron–sulfur compounds come into contact with atmospheric oxygen and water. Through a series of chemical and biochemical reactions, a solution with low pH, high mineral acidity, and elevated dissolved metal (e.g. iron, aluminum, magnesium) concentrations is produced. Consequently, an understanding of coordination chemistry as well as the nonideal behavior of ions in high ionic strength solutions becomes necessary to predict conditions that favor the formation of AMD. Beyond the consideration of chemical reactions and rates, the real‐world description of AMD is further complicated by the heterogeneity of the overburden that is disturbed during mineral extraction, the high variability in the extent and rate at which overburden is in contact with oxygen and water, and many other site‐specific factors that are too numerous to address in any one paper. Each of these topics is covered in sufficient detail to provide readers with a basic understanding of their mechanisms of action and their relevance to AMD production. Additional sources are also provided for those who need to delve deeper into any of these topics.
Colloids and Nanoparticles in Aquatic Systems
Authors: Santschi Peter H.
Published: December 2019

Colloids in the ocean are mainly composed of natural organic matter (NOM), with trace amounts of metals, nutrients, radionuclides, pollutants, and variable amounts of anthropogenically produced engineered nanoparticles and nanoplastics. Thus, state‐of‐the‐art instrumental techniques are required to unravel the chemical composition of colloids.

Such studies revealed that colloidal macromolecular organic matter (COM) contain aquagenic substances (composed of microbially produced exopolymeric substances, EPS, gels, transparent exopolymer particles, TEP, and TEP precursors) and pedogenic substances (humic and fulvic matter). COM can act as glue or as soap; can be bioavailable and biodegradable or refractory; and contain different moieties that act as metal chelators, antioxidants, or absorber of hydrophobic pollutants. EPS in aquatic systems, mostly composed of polysaccharides and proteins, can form not only biofilms but also marine snow (MS) or marine oil snow (MOS), and are important in initiating and maintaining aggregation and sedimentation processes. These processes can also be traced by natural radionuclides that have colloidal fractions.

These aggregation processes lead to “colloidal pumping” (aggregation to form larger particles) of trace substances bound to EPS and other macromolecular NOM compounds that counteract the prevailing pathway of degradation of macromolecular NOM to low‐molecular‐weight molecules.
Water and Gender Relations
Authors: Schneiderman Jill S.
Published: December 2019

Water is a critical need for health and well‐being. However, not all people enjoy equal access to clean and reliable sources of water for domestic and other purposes. This reality rings true particularly for women in developing countries. The causes of such inequity come from structural inequalities across different cultures and societies. Women, particularly in developing countries, disproportionately bear the burden of water provision for families. This creates negative consequences for the health and well‐being of women and their children such as limited access to educational opportunities, increased stress, and physical illness. Solutions to these problems exist in the form of potential opportunities for women to engage collectively in water projects and participate in decision‐making in the arena of water development projects. The involvement of women in such activities also holds the promise of increasing efficacy and success of water projects as well as breaking down gender hierarchies.
Low‐Level Ice Clouds–Ice Fog
Authors: Gultepe Ismail
Published: December 2019

Ice clouds play an important role in the hydrological cycle and climate change, and their impact on water and heat cycle is crucial depending on their macro‐ and microphysical properties. As ice fog, it also affects weather conditions such as visibility.

Ice clouds and ice fog usually form at cold temperatures (
T
< 0 °C), and their nucleation processes usually take place at
T
< −5 °C. They occur extensively at colder
T
. They are usually composed of only ice crystals although mixed‐phase particle can be found down to −40 °C, and below that
T
, droplets can freeze up spontaneously. The development of ice clouds needs some level of dynamical activity, e.g. updrafts and thermal instabilities in a lifting moist air layer. Ice fog is composed of many small particles and has less water content compared to ice clouds. Its impact on economy and on Earth's heat budget is still not understood properly.
In situ
observation of ice cloud and their monitoring using remote‐sensing platforms such as radar, LiDAR, and satellites can improve their predictions and help develop algorithms to retrieve their physical properties.

In this article, the physical properties of ice cloud and ice fog are summarized using
in situ
and remote‐sensing observations, also focusing on the prediction issues related to forecast and climate models.
Groundwater Modeling
Authors: Holzbecher Ekkehard
Published: December 2019

Computer models nowadays have become part of the common toolbox used in groundwater studies, concerning subsurface flow and transport processes. Analytical and numerical models are developed as solutions of differential equations, which are derived from basic principles and conservation laws. There are different finite discretization techniques to implement approximate solutions for differential equations and boundary conditions on a computer. Current modeling software, used by modelers for their work, not only includes solvers for equations but also various tools for pre‐ and postprocessing. The connections with other software, for surface water, for multispecies, for multiphysics, geo‐information systems, optimization, or parameter estimation are the current frontier of further development.
Water‐Jetting Drilling Technologies
Authors: Jacobs James A.
Published: December 2019

Water‐jet drilling or jetting has been used as a drilling method in both the developing world for water supply projects and in the United States for
in situ
remediation of hydrocarbons, chlorinated solvents, and metals. For the developing world, low‐cost, large diameter jetting is used for digging water supply wells. The technology only requires hand tools, such as wrenches, a water pump (electric, solar‐powered, fuel powered), flexible hoses with swivels, water source (in plastic‐lined pit or drums, for example), and a drill bit with pipe. Gravel pack for the well filter and polyvinyl chloride (PVC) pipe (screen and blank) are needed to complete the jetted well. For remediation, small diameter, high‐pressure (700 kPa or about 100 psi) 1–2 cm diameter drill wands are sued to pierce into the subsurface and deliver remediation chemicals into the soil and groundwater to treat a variety of contaminants.
Construction Sites: Stormwater Impacts from Runoff Water
Authors: Jacobs James A.
Published: December 2019

Construction sites can use industry best management practices (BMPs) to reduce turbidity in the stormwater runoff water which, if left untreated, can affect surface water. Groundwater can also be impacted from contaminated runoff water which infiltrates into the subsurface reaching shallow aquifers. Besides total suspended solids (TSS), runoff water from construction sites can solubilize petroleum hydrocarbons, chlorinated solvents, agricultural chemicals (such as pesticides, herbicides, and insecticides), nitrates, metals, as well as other contaminants. Fortunately, erosion control designs, employee training, and stormwater runoff prevention by BMPs can reduce the environmental impacts from water derived from construction sites. Snow and ice melting can create stormwater impacts by transporting sand, grit, and other traction compounds. Commonly used deicing compounds and the ubiquitous road salt are toxic to most freshwater aquatic life, and the impacts for shallow groundwater resources can be large. The rate of snow and ice melt can increase greatly on a warm day well above freezing, creating surface flooding and rapid subsurface infiltration. This article is an updated version of an earlier article from 2005.
Eutrophication and Nutrient Fluxes in Mediterranean Coastal Lagoons
Authors: Padedda Bachisio M. , Pulina Silvia , Satta Cecilia T. , Lugliè Antonella , Magni Paolo
Published: December 2019

In this article, we provide a general overview of eutrophication in aquatic ecosystems, with a focus on the Mediterranean Sea and two Sardinian lagoons (western Mediterranean Sea, Italy), as case studies. In the Cabras Lagoon, we assessed the nutrient budget and fluxes using the biogeochemical Land–Ocean Interaction Coastal Zone model. High nutrient and chlorophyll‐aconcentrations indicated eutrophic conditions, summer being the most critical season as related to the decrease in riverine water supply, the increase in water evaporation and a concurrent isolation of the lagoon from the adjacent sea. In the Calich Lagoon, the eutrophic conditions, assessed during 2008–2015, seemed to be attenuated by a good water exchange with the sea, yet potential harmful phytoplankton species were found. Overall, the present study shows how Mediterranean coastal lagoons are strongly influenced by both terrestrial and marine ecosystems. Eutrophication is one of the main forms of environmental degradation of aquatic ecosystems, and in coastal lagoons, this is the consequence of multiple pressures, which have led to significant losses of major ecosystem goods and services, such as aquaculture, fishery, and tourism. Good practices and landscape management are urgently needed to prevent further deterioration of these sensible ecosystems.
The Oceans: Ocean Circulation, Upwelling, and ENSO
Authors: Maurice Patricia A.
Published: December 2019

Water covers about 71% of the Earth's surface, and the oceans represent by far and away the largest reservoir of water. The oceans produce more than half of the oxygen in the atmosphere. They also take up carbon from the atmosphere, playing a huge role in the carbon cycle. The oceans strongly affect climate and weather patterns. This article is meant to serve as a brief introduction to the oceans, focusing primarily on ocean chemistry, ocean circulation, and the El Niño Southern Oscillation (ENSO). Other articles in the Encyclopedia cover many topics related to the oceans in much greater detail.
Chemical Kinetics in Environmental Systems
Authors: Maurice Patricia A.
Published: December 2019

The surface of the Earth is highly dynamic due to the influx of energy from the Sun coupled with radiogenic heat flow from the Earth's interior. This energy flux drives chemical reactions and helps to keep many environments and processes from attaining equilibrium. While many investigations of aqueous (geo)chemistry have focused on describing equilibrium conditions, it is also important to understand the rates of reactions, which is the realm of kinetics. This article provides a brief introduction to chemical kinetics in environmental systems as a backdrop for many of the other articles in the Encyclopedia dealing with topics such as microbial reactions, water treatment, acid mine drainage, etc. The focus here is on fundamental kinetic theory with some applications to topics such as mineral dissolution and adsorption. This article is drawn heavily from P. Maurice's 2009 book onEnvironmental Surfaces and Interfaces from the Nanoscale to the Global Scale, but substantially updated and expanded.
Pipe Failure Prediction with Consideration of Climate Change
Authors: Demissie Gizachew , Tesfamariam Solomon , Dibike Yonas , Sadiq Rehan
Published: December 2019

Rapidly changing climate combined with aging and deterioration of water supply system pipes present a significant challenge to most water utilities. Water transmission and distribution pipes are most often susceptible to the risk of failure because of their spatial diversity and inaccessibility with limited information available to understand their deterioration process. This article provides a modeling approach, Bayesian Model Averaging (BMA), for using climate projections in conjunction with other operational, physical, and environmental factors to predict/forecast cast iron (CI) pipe failure rates in the city of Calgary. The data from the city of Calgary, which constitutes operational factors, pipe physical attributes, and soil properties, and a statistically downscaled climate data from the Coupled Model Intercomparison Project phase 5 (CMIP5) are used for the demonstration of the developed BMA model. The result of parameter identification shows that the climatic parameters are found to be less sensitive; however, a significant change in sensitivity over time was exhibited during 1956–2014. The model results showed that there is a decrease in the failure rate for all CI pipes. However, the highest failure rate is expected for smaller‐diameter pipes compared to medium‐ and larger‐diameter pipes.
Use of
XAS
for Studies of Aqueous and Surface Geochemistry
Authors: Werellapatha Kalpani
Published: December 2019

X‐ray absorption spectroscopy (XAS) uses synchrotron X‐rays to provide local electronic, magnetic, and structural information about an element by exciting its core‐electrons either to the empty/nearly empty bound orbitals above the Fermi energy or to the continuum. Being element specific and sensitive to near neighbors, it provides a good contrast between different elements. Not requiring long‐range order makes it applicable to many disordered and dilute systems. Further, samples can be measured in environmental conditions and
in situ
, supporting investigations in aqueous and surface geochemistry. This article gives brief insights into basic theory of XAS spectroscopy, measurement methods, data analysis techniques and some instances of use of XAS in surface and aqueous geochemistry for beginner‐level students in various disciplines.
Crop Evapotranspiration
Authors: Todorović Mladen
Published: December 2019

Evapotranspiration is a process referring to water transfer from the land to the atmosphere by evaporation, from the soil surface, and by transpiration, through the vegetation. It is a complex process of great relevance for the hydrological balance at different scales. Nevertheless, it is difficult to measure and estimate; hence, almost all evapotranspiration data contains errors. The main biophysical principles of evapotranspiration are described together with the most relevant methods for measurement and estimation. Particular attention is given to crop evapotranspiration used in irrigation scheduling and agricultural water management. The estimation of crop evapotranspiration is presented following the two‐step approach based on crop coefficient and reference evapotranspiration. The concept of reference evapotranspiration is expounded by means of the Penman–Monteith approach that combines surface energy balance and aerodynamic principles of the process. The indicative data of crop coefficient and length of crop growing stages are reported in tables for most relevant agricultural crops and the world growing regions. A detailed description of calculation procedures for the estimation of reference and crop evapotranspiration is presented together with the methods to improve crop coefficient estimate under specific growing conditions. Finally, numerical examples of reference and crop evapotranspiration are given in Appendix 1.
Chemical Signaling in Aquatic Ecosystems
Authors: Lunsford Elias T. , Jenkins Karin , Ferrer Ryan P.
Published: December 2019

Chemical information mediates many of the biotic relationships that shape aquatic communities. Mate attractants and courtship pheromones determine successful reproductive encounters. Conspecific and environmental chemical cues influence the distribution of settling larvae and the ability of organisms to navigate across great distances to suitable habitat. Allelopathic agents can determine winners and losers in competition over resources, while signals transmitted between mutualists facilitate cooperation. Substances emitted from predators and prey provide early warnings of imminent threats to prey, while guiding predators to their next meal. Each of these individual interactions contributes to the dynamic nature of populations and communities in aquatic ecosystems. In this article, we provide an overview of the roles of chemistry and fluid dynamics in chemical ecology, and highlight several ecological interactions and life history events that are significantly affected by chemical cues, signals, and defenses. We offer examples from the literature that emphasize a multidisciplinary approach, when possible, and include promising future directions for research in large‐scale aquatic chemical ecology.
Unregulated Disinfection By‐Products: Spatiotemporal Variation in Water Distribution Networks
Authors: Chhipi‐Shrestha Gyan , Pokhrel Sarin R. , Kaur Manjot , Proulx Francois , Rodriguez Manuel J.
Published: December 2019

Residual disinfectants react with various natural organic matter in distribution networks (DNs) to form disinfection by‐products (DBPs), which are a public health concern. The regulated DBPs in various jurisdictions are trihalomethanes, haloacetic acids, bromate, and chlorate, which are mostly associated with chlorine. Owing to this, several alternative disinfectants, such as chloramines, ozone, and chlorine dioxide are also used. Although the use of alternate disinfectants has reduced the formation of regulated DBPs, these disinfectants have gathered much attention by introducing another cluster of DBPs known as unregulated DBPs (U‐DBPs). Many U‐DBPs are potentially toxic, mutagenic, and/or carcinogenic. This study reviews the models for predicting the spatiotemporal variation of U‐DBPs and analyzes their variability in DNs in the provinces of Quebec, and Newfoundland and Labrador, Canada. The findings show that limited predictive models are available for U‐DBPs compared to regulated DBPs. The concentrations of haloacetonitriles, chloropicrin, and haloketones significantly differed along the DNs based on the distance traveled and/or residence time. Similarly, temporal variability was significant in different seasons and in various weeks in summer but not significant by days from Monday to Friday. The formation of U‐DBPs can be controlled by source water protection, use of advanced treatment, alternative disinfectants, etc.
Groundwater Governance
Authors: Molle François , Closas Alvar
Published: December 2019

Groundwater resources are being increasingly exploited around the world and patterns of overexploitation are widely observed. Long seen as the remit of hydrologists, groundwater is now understood as a key and politically disputed resource that supports domestic use, livelihoods, and high‐value commercial farming, as well as many wetlands and other groundwater‐dependant ecosystems. The governance of groundwater is complex due to its invisible and elusive nature, its fluctuating exchanges with surface water bodies, the diffuse nature of abstraction points, and the lack of state control over the individual initiatives that often arise in response to water shortages. Governance based on community‐, state‐, or market‐centered arrangements has tended to perform poorly. Comanagement shows some potential but is so far limited to specific physical‐cum‐political environments.
Vinyl Chloride in Groundwater: Chemical Behavior and Treatment
Authors: Jacobs James A.
Published: December 2019

Vinyl chloride (VC) is manufactured chlorinated solvent and is a chemical intermediate used in manufacturing of other items. VC is not a final product but is used to make polyvinyl chloride (PVC) plastic and vinyl products, including PVC pipes, packaging products, and wire and cable coatings as well as plastic furniture, vehicle upholstery and parts, house products, and wall coverings. VC has historically been used as a refrigerant but is no longer used for that purpose. Besides being a highly volatile and flammable liquid, human health exposure to VC is primarily through inhalation of VC‐contaminated air or ingestion of VC‐containing water or food. VC‐production workers may have dermal exposure through working with the chlorinated solvent. Liver toxicity and cancerous tumors are associated with VC which is a known human carcinogen. The U.S. Environmental Protection Agency (U.S. EPA) maximum contaminant level (MCL) for vinyl chloride is 2 μg L−1or 2 parts per billion (ppb), which is lower than the associated tetrachloroethylene (PCE) and trichloroethylene (TCE) MCL of 5 μg L−1or 5 ppb.
Life Cycle for Groundwater Remediation Projects
Authors: Jacobs James A.
Published: December 2019

During the past few decades, the groundwater remediation project life cycle has been used in many countries to characterize the status of an environmental remediation project. If groundwater or soil contamination is suspected, a general process from assessment to closure occurs. Although the timing and specific activities may vary from site to site, a general phased process occurs. Environmental evaluations of potential leakage or spillage of hazardous substances into the subsurface generally consist of four phases (Phase I through Phase IV), which are described in this article.
In Situ
Bioremediation of Groundwater: Process Limitations
Authors: Vance David B. , Jacobs James A.
Published: December 2019

This article deals with bioremediation of hydrocarbon contaminants in groundwater. Two types of hydrocarbons are addressed: petroleum hydrocarbons and complex chlorinated hydrocarbons. Factors that must be optimized for successful bioremediation are discussed in detail.