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Word Definition
pollen a fine powdery substance produced by the anthers of seed-bearing plants, consisting of numerous fine grains containing the male gametes
background extinction the ongoing extinction of individual species due to environmental or ecological factors such as climate change, disease, loss of habitat, or competitive disadvantage in relation to other species. Background extinction occurs at a fairly steady rate over geological time and is the result of normal evolutionary processes, with only a limited number of species in an ecosystem being affected at any one time.
crust the outermost layer of the Earth, consisting of relatively low-density rocks
physical change a change in matter that rearranges molecules but doesn't affect their internal structures; the form of matter changes, but not its composition
chemical change A process in which a substance is transformed into a different substance by changing its chemical composition.
alpha particle a helium-4 nucleus, especially when emitted from the nucleus of a radioactive atom
beta particle an electron emitted from the nucleus of a radioactive atom
chain reaction a reaction in which the material or energy that starts the reaction is also one of the products and can cause similar reactions
landfill 1. the practice of filling in land, especially a low-lying wetland area, with garbage, ash, and dirt, as a means of waste disposal. 2. the materials used in this process
kilocalorie the amount of heat required to raise the temperature of one kilogram (or one liter) of water by one degree Celsius. This is the unit most commonly used to measure the energy content of food and human energy requirements, and the term "calories" as it appears on a food label actually refers to kilocalories
electricity 1. a fundamental form of energy, consisting of oppositely charged electrons and protons that produce light, heat, magnetic force, and chemical changes 2. the flow of this energy; electric current. 3. the general phenomenon of charges at rest and in motion.
heating oil a low viscosity, flammable liquid petroleum product used as a fuel for furnaces or boilers in buildings; heating oil and diesel fuel are closely related products called distillates.
propane a colorless, straight-chain hydrocarbon gas with with formula C3H8 that boils at a temperature of -43.67 degrees Fahrenheit; extracted from natural gas or refinery gas streams, and is commonly used as a fuel for engines, oxy-gas torches, barbecues, portable stoves, and residential central heating.
electromagnetic radiation the emission and propagation of radiation associated with a periodically varying electric and magnetic field traveling at the speed of light; types include gamma radiation, X-rays, ultraviolet, visible, and infrared radiation, and radar and radio waves.
gasoline a volatile liquid mixture of hydrocarbons that is obtained by refining petroleum and that is used as the fuel in most internal-combustion engines.
uranium a metallic element having the symbol U, the atomic number 92, an atomic weight of 238.029, a melting point of 1132ºC, and a boiling point of 3818ºC; a dense silvery solid with three naturally occurring radioactive isotopes.
heat of fusion the heat absorbed by a unit mass of a solid at its melting point in order to convert the solid into a liquid at the same temperature.
internal combustion engine an engine in which the process of combustion takes place in a cylinder or cylinders within the engine; the working fluid is a fuel and air mixture, which reacts to form combustion products and is then exhausted; e.g., a gasoline or diesel engine.
waste heat the portion of the energy input to a mechanical process that is rejected to the environment.
steam engine 1. any device that converts the heat energy of steam into mechanical energy. 2. specifically, a reciprocating engine operating by the force of steam on a piston in a closed cylinder, in which the steam expands from the initial pressure to the exhaust pressure in a single stage.
spontaneous process describing a process that occurs because of internal properties, with no external forces required to continue the process, although external forces may be required to initiate it. The term is used to refer to processes in which entropy increases; such as a smell diffusing in a room, ice melting in lukewarm water, salt dissolving in water, and iron rusting.
nonspontaneous process describing a process that requires external forces (energy) to continue the process
energy and materials balance the principle that the total mass of materials and amount of energy entering a process are equal to the amounts of mass and energy leaving the process.
power plant a general term for any facility in which some other form of energy (e.g., steam, hydropower) is converted into electrical energy.
boiler a closed, pressurized vessel in which water or other liquid is heated, either to be utilized in its liquid state or to generate steam energy; e.g., a device that utilizes the heat from a furnace to convert water into high-pressure steam.
turbine a general term for any machine capable of generating rotary mechanical power by converting the kinetic energy of a stream of fluid (e.g., water, steam, hot gas); turbines operate through the principle of impulse or reaction, or a combination of the two.
generator any machine that converts mechanical energy into electrical energy.
fly ash 1. a fine powder formed after combustion of coal, consisting of the noncombustible matter in the coal and a small amount of carbon that remains from incomplete combustion. 2. any finely divided residue, essentially noncombustible refuse, suspended in the combustion gases from a furnace.
fuel Any material that evolves energy in a chemical or nuclear reaction. 2. specifically, a material that can be used to provide power for an engine, combustor, power plant, nuclear reactor, and so on.
radiocarbon dating a precise method of dating ancient organic artifacts, an important tool in modern archaeology and other branches of science. Carbon-14 is an unstable radioactive isotope that decays at a measurable rate upon the death of an organism, allowing a determination of the time at which the organism lived, based on the amount of C-14 remaining.
natural resource any form of energy or material ocurring in nature that is extracted and used by humans
environmental services a wide range of conditions and processes through which natural ecosystems, and the species that are part of them, help sustain and fulfill human life.
waste assimilation the ability of the environment to absorb, detoxify, and disperse wastes in a way that makes them less harmful.
resource depletion the consumption of a natural resource at a faster rate than the possible rate of replacement most commonly used in reference to the farming, fishing, mining and timber industries.
overfishing to fish so as to deplete the supply of fish in certain waters.
best first principle the observation that humans generally use the highest quality sources of natural resources before lower quality sources.
environmental performance bond cash or securities deposited before permitting an activity that is likely to have an environmental impact. The money is returned to the owner if no damages occur. If damages do occur, portions of the bond are be used to rehabilitate or repair the environment and possibly to compensate injured parties.
externality an effect of a purchase or use decision by one set of parties on others who did not have a choice and whose interests were not taken into account.
subsidy a benefit given by the government to groups or individuals usually in the form of a cash payment or tax reduction.
ecological footprint a measure of how much land and water area a human population requires to produce the resource it consumes and to absorb its carbon dioxide emissions, using prevailing technology.
human development the process of enlarging the range people's choices by increasing their opportunities for education, health care, a clean environment, income, employment, and political freedom.
quintile statistical value of a data set that represents 20% of a given population. The first quartile represents the lowest fifth of the data (1-20%); the second quartile represents the second fifth (21% - 40%) etc.
greenhouse gas any of the gaseous constituents of the atmosphere, both natural and anthropogenic, that absorb and emit radiation at specific wavelengths within the spectrum of infrared radiation emitted by the earth's surface, the atmosphere, and clouds. This causes the greenhouse effect.
nitrogen oxide NOx, the generic term for a group of highly reactive gases, all of which contain nitrogen and oxygen in varying amounts; many are colorless and odorless, although one common pollutant, nitrogen dioxide (NO) can be seen along with particles in the air as a reddish-brown layer over many urban areas. Nitrogen oxides form when fuel is burned at high temperatures, in motor vehicles, electric utilities, and other industrial, commercial, and residential sources. The components of NOx are acid rain precursors and also participate in atmospheric ozone chemistry.
economic system The collection of firms and households that produce and consume the goods and services people associate with material well-being.
falsified Rejection of a hypothesis because observations or experimental results are inconsistent with expectations.
feedback loop Linkages that move through a system and ultimately connect back to itself.
flows Movements of energy or materials between storages in a system.
general systems theory The study of relationships, structures, and interdependence of storages and flows.
gradient A change in the entropy of energy or matter over a specific distance.
integrated systems approach The use of information from many disciplines that is needed to understand and solve specific environmen- tal problems and generate general policy that moves society toward sustainability.
invalidated Rejection of a hypothesis because observations or experimental results are inconsistent with expectations.
positive relationship Correlation between parts of a system such that an increase in one part of a system causes an increase in another part of the system.
reductionist approach A scientific methodology based on the premise that the best way to learn about something is to break it into its parts and study the parts separately.
resilience The ability of a system to return to its set point following a disturbance.
risk management The process of making decisions without complete information due to the presence of a stochastic element.
stability The ability of a system to return a storage or flow to a set point following a disturbance.
scenario analysis A modeling technique that involves entering different sets of data into a model and determining how changes in the input data affect the model’s output.
simulation models A modeling technique that involves entering different sets of data into a model and determining how changes in the input data affect the model’s output.
stochastic Containing uncertainty due to an element of chance.
storage A system part where energy or materials stay for an extended period.
subsystem A system that is part of a larger system.
time lag The period that lapses between a cause and its effect.
validated Confirmation of a hypothesis because observations or experimental results are consistent with expectations.
advection The horizontal transfer of mass or energy as air masses move in response to pressure differences, such as winds.
albedo The fraction of incoming solar radiation that is reflected back to space.
asthenosphere The upper part of the mantle, which has a consistency that is somewhere between a liquid and a solid and moves large quantities of heat from Earth’s center toward the surface.
condense To change from a gas to a liquid as a result of being cooled.
consolidation The process of joining particles to form sedimentary rocks.
easterlies Surface winds that move from the poles toward the polar front.
equatorial low A region of low pressure near the equator due to rapidly rising air.
erosion The process of carrying away soil particles from their parent material by wind or water.
gyre A circular motion of water with a diameter of thousands of kilometers.
sediment Fine particles created from the weathering of rocks.
solar constant The amount of solar radiation that reaches the upper layers of Earth’s atmosphere: 1.97 calories per square centimeter per minute.
subtropical high A region of high pressure about 30° north and south of the equator due to the descending portion of the Hadley cell.
temperature profile The change in temperature with depth.
thermohaline circulation Regular circulation of ocean waters between the surface and deep layers due to differences in temperature and salinity.
trade winds Ground-level winds associated with the pressure gradient that causes air to move from the subtropical high to the equatorial low.
upwellings Areas where large quantities of deep ocean water rise back to the surface.
weathering The breakup of solid rock.
westerlies Midlatitude surface winds that blow from the subtropical high toward the polar front.
winds Horizontal motion of air caused by the uneven heating of the atmosphere combined with Earth’s rotation.
igneous rocks Rock formed when molten (melted) materials harden.
lithosphere The outermost layer of crust and uppermost mantle that consists of about two dozen major plates on which the continents ride.
metamorphic rocks Rocks that have been physically altered by heat and/or pressure.
orographic precipitation Precipitation that results from or is enhanced by mechanical lifting of an air mass over mountains.
plate A large rigid slab of solid rock that makes up a portion of the lithosphere.
polar cell A weak pattern of atmospheric circulation characterized by ascending motion in the subpolar latitudes (50°–70°), descending motion over the pole, poleward motion aloft, and equatorward motion near the surface.
polar front An area of low pressure at about 60° north and south of the equator.
radiation balance The difference between incoming and outgoing radiation.
reflection The process whereby a surface turns back a portion of the radiation that strikes it.
rock cycle A series of processes through which a rock changes, over time, between igneous, sedimentary, and metamorphic forms.
scatter To disperse radiation in different directions.
sedimentary rocks Rocks created by pressure and cementation of particles in a process known as consolidation.
simulation models A modeling technique that involves entering different sets of data into a model and determining how changes in the input data affect the model’s output.
integrated systems approach The use of information from many disciplines that is needed to understand and solve specific environmental problems and generate general policy that moves society toward sustainability.
active range The span of body temperatures at which ectotherms can carry out their every-day activities.
anaerobic respiration The release of energy from glucose or another organic substrate in the absence of oxygen.
carnivores Animals that eat other animals.
decomposers Organisms that get food energy from dead parts of other organisms.
ecological efficiency The percentage of energy from one trophic level that is incorporated in the next level.
energy pyramid A diagram that compares the amount of energy available at each position, or level, in the feeding order.
maturation A growth process in which juveniles increase in size and change in form to the point at which they are capable of reproduction.
metamorphosis A dramatic change in body form that occurs as juveniles change to adults.
omnivores Heterotrophs that feed on both plants and animals.
parenting Energy allocated toward reproduc- tion in the form of caring for offspring.
primary consumers Organisms in the second trophic position that eat autotrophs (also known as grazers).
r selected An evolutionary strategy in which organisms allocate a large fraction of their energy budget toward reproduction.
secondary consumers Organisms in the third trophic position that eat organisms in the second trophic position.
secondary productivity The rate at which heterotrophs create new biomass per unit area in a given time period.
trophic position The position along the food chain or food web at which an organism obtains energy.
zooplankton Small multicellular organisms that are among the most important primary consumers in aquatic environments.
maintenance respiration The use of energy to maintain order in a living system.
carbohydrates Organic molecules that contain only carbon, hydrogen, and oxygen.
essential Molecules that an organism cannot synthesize from its constituents.
fats Organic molecules that contain only carbon, hydrogen, and oxygen and can store large amounts of energy per unit mass.
flow Movements of energy or materials between storages in a system.
kwashiorkor Severe malnutrition caused by a diet with insufficient protein that is found primarily in young children.
limiting nutrient The nutrient that is in least supply relative to the quantity required by an autotroph.
mineralization Conversion of organic forms of nutrients to inorganic forms
proteins Large complex molecules made up of one or more chains of amino acids.
tailings Material that remains after all metals considered economic have been removed from ore during milling.
unknown carbon sink An unknown mechanism that removes carbon from the atmosphere or a known mechanism that removes carbon faster than estimated by scientists.
benthic The area on or near the floor of a body of water.
epifauna Organisms that are attached to or move about the surface of the bottom of a water body.
epilimnion The upper layer of a water body where sunlight may power high rates of net primary production.
epipelagic The oceanic zone extending from the surface to about 200 meters, where enough light penetrates to allow photosynthesis.
eutrophic Water bodies that have high net primary production.
environmental gradients Changes in conditions from one region to the next.
filter feeders Organisms that obtain food by separating it from passing water.
germinate The process by which a seed starts to grow and develop.
habitat Geographical locations and environmental conditions where a plant or animal lives.
hadal The deepest layer of the ocean, below 6,000 meters.
hypolimnion The layer of water in a thermally stratified lake that lies below the thermocline, is noncirculating, remains perpetually cold, and is usually low in oxygen.
lentic Characterizing aquatic communities found in standing water.
limnetic zone The well-lit, open-surface water area far from shore.
littoral zone Shallow waters that are near the shore.
lotic Of, relating to, or living in actively moving water.
mesopelagic The middle layer of the ocean from 200 to 1,100 meters.
mudflat Large areas of mud in the intertidal zone that are exposed to the air during low tide.
oligotrophic Aquatic ecosystems with low rates of net primary production.
payback period The time it takes an energy investment to capture or save an amount of energy equivalent to the investment.
pelagic Open areas of the ocean away from the bottom.
phreatic zone The saturated soil below a stream.
potential evaporation The amount of water that would evaporate if water were available.
prairies The North American term for grasslands.
reproductive range The area where individuals have enough energy for reproduction.
rooting depth The vertical distance from the soil surface that contains 95 percent of a plant’s roots.
salinity The concentration of mineral salts dissolved in water.
salt marsh The transition area from land to sea that is farthest from the sea.
specializations Adaptations well suited for a relatively narrow range of conditions.
survival range The area where an individual can obtain enough energy and materials to survive.
allelopathy Direct or indirect harmful effects of one plant on another through the production and release of chemical compounds.
annuals Plants that live for a single growing season.
competition Simultaneous demand by two or more individuals for limited environmental resources.
disturbances A discrete, punctuated killing, displacement, or damaging of one or more individuals (or colonies) that directly or indirectly creates an opportunity for new individuals (or colonies) to become established.
ecological resistance The degree to which an ecosystem changes following a disturbance.
ecological restoration The process of reestablishing to the extent possible the structure, function, and integrity of indigenous ecosystems and sustaining the habitats they provide.
ecological stabilityf The ability of an ecosystem to return to its original state following a disturbance.
ecosystem health The degree to which ecosystems are stressed by human activities.
facilitation A mechanism for succession in which species in early and middle successional communities change their microenvironments in ways that make them less hospitable for their own needs or more hospitable to species that inhabit later successional communities.
inhibition A mechanism of succession in which one species has a direct or indirect harmful effect on another species.
light compensation point The light level at which photosynthesis generates energy equal to respiration.
light saturation point The light level at which further increases in light do not increase photosynthesis.
macroenvironment Characteristics of a large geographical area.
microenvironment Small-scale conditions at which an organism lives.
perennials Plants that live for several growing seasons.
pioneer community The first plants and animals to inhabit an area that was previously uninhabited.
predictability Variance in the average time between events.
redundancy The presence of more than one species in a functional group.
spatial scale Geographic area.
strong interaction A trophic connection between species in which the predator eats only a few types of foods, so the likelihood of consumption of one species by another is high.
succession A change in plant and animal communities that follows a disturbance.
tolerance model A mechanism for succession in which species replace one another based on their ability to withstand limiting factors.
trophic cascades Population changes transmitted via the food web from one trophic position to the next.
turnover rate The average time required to disturb an entire area.
weak interaction A trophic linkage among species such that the likelihood of consumption of one species by another is small.
age classes The number of males and females in an age group.
age–dependency ratio The number of people under the age of 15 plus the number of people over age 65 divided by the number of people between those ages.
agriculture The process by which a natural ecosystem is replaced with one that supports plants and animals of people’s choosing.
birthrate The number of new individuals produced by a population in a period.
crude birthrate The number of births per 1,000 people per year.
crude death rate The number of deaths per 1,000 people per year.
demographic transition The process of moving from high birthrates and high death rates to high birthrates and low death rates, and finally to low birthrates and low death rates.
density-dependent factors Variables that affect population growth but are not related to the size of the population.
density-independent factors Variables that affect population growth and are related to the size of the population.
doubling time The time required for a variable to double.
environmental resistance The slowdown in population growth that occurs as a population approaches its carrying capacity.
exponential population growth Continuous population growth in proportion to the size of the population.
gathering The collection of edible plants from unaltered ecosystems.
geometric population growth Growth in populations that produce a single batch of offspring in a year.
hunting Capture of wild animals from an ecosystem.
logistic equation A function describing the idealized growth of a population subject to a density-dependent limiting factor.
maximum intrinsic growth rate The largest per capita rate at which a population can grow under ideal conditions.
overshoot Population exceeding carrying capacity.
population growth An increase in population.
population histograms Diagrams that represent the number of males and females in various age groups.
population momentum Built-in potential for population growth due to a large number of individuals entering reproductive age.
replacement level fertility The total fertility rate at which a population remains constant.
strong sustainability A criterion that prohibits human actions degrading the environment or using environmental goods or services faster than they are generated by the environment.
sustainable development Economic activities that meet the needs of the present without compromising the ability of future generations to meet their own needs.
total fertility rate The average number of children a woman will bear over her lifetime.
weak sustainability The principle that actions that degrade the environment or use a natural resource or a waste-processing service faster than it is generated by the environment can be sustainable if these losses are offset by an increase in either economic capital or social institutions.
age dependency ratio The number of people under the age of 15 plus the number of people over age 65 divided by the number of people between those ages.
affluence The average material standard of living in a nation, typically measured by per capita GDP or GNP.
avoided costs The costs of providing a service (such as chemical pest control) that are avoided by maintaining a natural service (natural pest control).
biodegradable waste Waste that is capable of undergoing anaerobic or aerobic decomposition, such as food and garden waste, paper, and paperboard.
capital Any asset or stock of assets, financial or physical, capable of producing income.
common property A resource owned by the public, such as fish in public waters, trees on public land, and the atmosphere.
consumption The purchase of goods and services by consumers.
contingent valuation A valuation technique that asks people directly how much they are willing to pay or to accept for improving or deteriorating environmental quality.
crustal abundance The amount of an element in Earth’s crust, measured as percentage by weight.
depletion The movement from high-quality, low-cost resources to lower-quality, highercost resources.
direct market valuation The use of the free market to place a value (price) on environmental goods and services.
dissipative waste Waste that is not technologically or economically feasible to collect and recycle.
draft animal An animal used for pulling heavy loads.
economic growth An increase in a nation’s production of goods and services.
environmental accounting Any quantitative approach to linking financial and environmental performance.
environmental degradation Processes induced by human behavior and activities (sometimes combined with natural hazards) that damage the natural resource base or adversely alter natural processes or ecosystems.
environmental energy cost The amount of solar energy and heat from Earth’s core that are used to produce a natural resource.
exhaustion The complete depletion of a natural resource.
factors of production Inputs to the production of a good or service, such as labor, capital, technology, energy, and materials.
firms Establishments that produce goods and services for consumers.
goods Physical, tangible products used to satisfy people’s wants and needs.
green national accounts The incorporation of environmental benefits and costs into economic decision making. The phrase often refers specifically to incorporating the depreciation of natural resources and the environment into estimates of net domestic product or net national product.
gross national income The total income earned by the citizens of a country.
hedonic pricing The use of statistical techniques to determine, from the prices of goods with different measurable characteristics, the prices that are associated with those characteristics. The latter can then be used to construct what the comparable price of a good would be from its characteristics.
labor A measure of the work done by human beings, especially work done for wages.
labor productivity The rate of output of a worker or group of workers per unit of time.
market failure The result when the prices of goods and services do not reflect the true costs of producing and consuming those goods and services. In the context of environmental externalities, a market failure occurs when the price of goods and services does not reflect full societal costs, which are conventional financial costs plus environmental externalities.
material waste Any materials unused and rejected as worthless or unwanted.
natural resource accounting The process of adjusting national accounts such as GNP to reflect the environmental costs of economic production.
nondegradable wastes Wastes that are incapable of being broken down into simple, less toxic compounds.
opportunity costs The cost of using a resource based on what it could have earned if used for the next best alternative. For example, the opportunity cost of farming your own land is the amount you could have received by renting it to someone else.
ore A mineral deposit containing a metal or other valuable resource in economically viable concentrations.
persistent wastes Wastes that degrade very slowly over time.
personal consumption expenditures Money spent by households on the purchase of goods and services.
petrochemicals Chemicals obtained by refining crude oil. Petrochemicals are used as raw materials in the manufacture of most industrial chemicals, fertilizers, pesticides, plastics, synthetic fibers, paints, medicines, and many other products.
postconsumer waste Waste collected after the consumer has used and disposed of it.
private property Ownership of property (or other assets) by individuals or corporations.
production In economics, manufacturing or mining or growing something (usually in large quantities) for sale.
property rights The rights of an individual to own property and keep the income earned from it.
public property Property owned by a government.
resource quality The amount of effort (capital, labor, energy) that is required to extract a natural resource.
travel cost method A method used to estimate the economic use values associated with ecosystems or sites that are used for recreation based on the assumption that time and travel cost expenses that people incur to visit a site represent the “price” of access to the site.
utility In economics, a measure of the happiness or satisfaction gained from a good or service.
waste Any materials unused and rejected as worthless or unwanted.
natural resource or environmental accounting Any quantitative approach to linking financial and environmental performance.
anthropocentric The ethical position that the value of nonhuman species is determined by their value to people.
asymmetric information The failure of two parties to a transaction to have the same relevant information.
biocentric The ethical position that nonhuman species have value in and of themselves and have the right to exist independent of their usefulness to humans.
cap and trade system A system of pollution control in which an environmental regulator establishes a “cap” that limits emissions from a designated group of polluters; emissions allowed under the new cap are divided into individual permits (usually equal to one ton of pollution) that represent the right to emit that amount. Companies are free to buy and sell permits to continue operating in the most profitable manner available to them.
centrally planned economies An economic system in which the government determines the quantities and prices of goods and services.
command and control A method of environmental regulation characterized by the application of direct regulatory controls to industry, such as by specifying allowable levels of pollution.
ecocentric A philosophy that claims moral values and rights for both organisms and ecological systems and processes.
economic efficiency A term that refers to the optimal production and consumption of goods and services. This generally occurs when prices of products and services reflect their marginal costs.
environmental justice The fair treatment of people of all races, cultures, and incomes with respect to the development, adoption, implementation, and enforcement of environmental laws, regulations, and policies.
externalities In economics, a cost or benefit attributable to an economic activity that is not reflected in the price of the goods or services being produced. Often refers to the cost of pollution and other environmental impacts.
feedlots Confined yards where livestock eat prepared or manufactured feed.
market The world of commercial activity in which goods and services are bought and sold.
market power The ability of a firm to exercise control over industry prices or output.
market-based incentives The use of tradable permits and other economic instruments to internalize environmental costs into market decisions.
pollution taxes A tax designed to reduce pollution by making the polluter pay the estimated amount of damages.
public goods Goods and services that are supplied by the government because it is not sufficiently profitable for the private sector to do so. This term is also applied to resources that are said not to be diminished by their consumption by any single person.
range-fed meat Meat derived from animals that were raised on rangeland.
subsidies Payments to firms or households that are designed to favor a particular action.
tradable permits An economic policy instrument under which rights to discharge pollution or exploit resources can be exchanged through either a free or a controlled permit market. Examples include individual transferable quotas in fisheries, tradable depletion rights to mineral concessions, and marketable discharge permits for waterborne effluents.
waste recovery Any waste management operation that diverts a waste material from the waste stream and results in a product with a potential economic or ecological benefit.
economically efficient A term that refers to the optimal production and consumption of goods and services. This generally occurs when prices of products and services reflect their marginal costs.
alien species Species that do not naturally occur within an area and that have usually arrived in the area as a result of human intervention (whether deliberate or accidental).
biodiversity hot spot An area with an especially large number of species.
black market A market in which goods or services are sold illegally.
corruption Unlawful use of public office for private gain.
diffuse chemical coevolution Natural selection favoring individuals that accumulate compounds effective against a wide variety of enemies.
edge effects Habitat conditions created at or near the more or less well-defined boundary between ecosystems.
edges Boundaries between well-defined ecosystems.
enemy release hypothesis The notion that the population of an alien species can grow rapidly (escape) if the number of pathogens it leaves behind in its native range exceeds the new pathogens it accumulates in its naturalized range.
climate envelope Conditions under which pop- ulations of a species can persist in the face of competitors and natural enemies.
heat balance The difference between the amount of energy that enters the atmosphere and the amount of energy that leaves the atmosphere.
land use change The practice of replacing natural ecosystems with others that meet human needs and wants.
reflect The process whereby a surface turns back a portion of the radiation that strikes it.
temperature sensitivity The long-term change in temperature given a doubling in atmospheric concentration of carbon dioxide or radiative forcing.
water use efficiency The amount of water transpired per unit of new biomass produced.
water efficiency The amount of water transpired per unit of new biomass produced.
water use efficiency The amount of water transpired per unit of new biomass produced.
acid mine drainage the outflow of acidic water from (sometimes abandoned) metal mines or coal mines.
ethnobotany The study of how different groups of people, including indigenous cultures, use plants and animals.
ex situ Maintaining a species away from its natural habitat.
extremophiles Organisms that live in extreme environments.
gap species Species whose range falls outside protected areas.
governance Act of governing and exercising authority.
habitat conversion Changes in the quality of land use or land cover associated with human activity.
immigration Movement of a species into an area previously uninhabited by that species.
in situ Efforts to preserve species in functioning ecosystems.
insurance The process of spreading the potential effects of risk.
invasive Species that displace indigenous species or spread into habitats where they were not previously common.
mass extinctions Periods when the extinction rate is much greater than the background extinction rate.
naturalized range An area that was previously uninhabited by a species.
nongovernmental organizations Private organizations that pursue activities to relieve suffering, promote the interests of the poor, protect the environment, provide basic social services, or undertake community development.
passenger species Species whose loss would have little effect on ecosystem function.
poaching Illegal killing or collecting of plants and animals.
pollinators Animals that place pollen on the stigma of plants.
predator control Efforts to reduce the populations of species that compete with humans for crops or game.
random drift Accumulation of changes in the gene pool due to stochastic events.
redundant species Species whose loss has little effect on ecosystem function.
species diversity The total number of living species.
species evenness The distribution of individuals among species.
threatened species Species that are likely to become endangered in the foreseeable future throughout all or a significant portion of their ranges.
endangered A species that is in danger of extinction throughout all or a significant portion of its range.
lapse rate Change in temperature with altitude.
marginal ice zone Area along the Antarctic coast where melting ice forms a shallow layer of relatively fresh water on top of salt water that has abundant supplies of light and nutrients.
molecular nitrogen Molecules of two nitrogen atoms that make up about 78 percent of the atmosphere.
molecular oxygen Molecules of two oxygen atoms that make up about 21 percent of the atmosphere.
ozone depletion potential The ability of a chemical to destroy ozone.
polar stratospheric clouds Clouds that consist of very small droplets of water and nitric acid that are formed at very cold temperatures.
polar vortex A surface wind that blows in a circular pattern around the pole during the winter.
stratosphere A layer of the atmosphere that extends from about 20 to 50 km above the surface, in which temperature rises by about 50°C.
thermosphere The outer layer of the atmosphere that starts at about 100 km in which temperature reaches 1,200°C.
trace gases A group of about twenty gases that make up about 1 percent of the atmosphere.
tropopause The end of the troposphere, where temperature starts to rise with altitude.
troposphere The lowest layer of the atmosphere extending from Earth’s surface to an altitude of 10 to 20 kilometers, in which temperature declines with altitude at a rate of about 6.5°C per kilometer.
Ecological stability The ability of an ecosystem to return to its original state following a disturbance.
crop residues Plant parts remaining in a field after the harvest of a crop, which include stalks, stems, leaves, roots, and weeds.
disintegration Physical changes in solid material that lead to soil formation.
eluvial horizon The soil layer from which minerals are leached as water percolates through the soil.
erodibility factor The ease with which soil particles can be detached and transported.
field capacity The quantity of both capillary and hygroscopic water stored by a fully wetted soil.
gravitational water Water that moves into, through, or out of the soil by gravity within a day or two of a rainfall event.
gully erosion Water erosion in which rills are concentrated into deeper channels.
horizons Soil layers that are approximately parallel to the surface and have distinct characteristics that are related to the process of soil formation.
hygroscopic water Tightly held water that forms a thin film around individual soil particles.
illuvial horizon A soil layer that accumulates the minerals that wash out from the eluvial horizon.
loam soil Soil ideal for agriculture that consists of a roughly equal mixture of clay, sand, and silt.
macropores Relatively larges spaces within soil.
micropores Small spaces within soil.
mollisols Soils with a deep A horizon that tend to form under grasslands.
oxisols Soils that often have a thin O layer and small amounts of nutrients.
pores Spaces between particles in a soil or an oil field.
private costs Costs incurred by the individual who causes environmental degradation.
regolith Unconsolidated material that lies above bedrock.
rill erosion Water-driven soil erosion in which sheet erosion becomes concentrated in small channels.
saltation Wind-driven erosion in which particles bounce along the surface.
second best problem Implementing a suboptimal policy because real-world conditions are inconsistent with those required for the optimal policy.
sheet erosion Water-driven erosion in which a film of water moves across the soil surface.
shelterbelts Soil protection provided by rows of planted vegetation between strips.
social costs The effects of environmental degradation on society.
soil conservation techniques Techniques designed to slow soil erosion.
soil erosion The rate at which soil is moved.
spodosols Soils formed under coniferous forests that have a relatively thin O horizon and a more thoroughly leached eluvial horizon
subsoil A soil layer known as the illuvial or B horizon.
surface roughness Irregularities in the soil surface that retard soil erosion by slowing wind speed.
terraces Ridges and channels that are constructed across a slope to prevent rainfall runoff from accumulating and causing serious erosion.
topsoil The A horizon.
total saturation The maximum water capacity of a soil.
turbulent Winds that move across the surface and have an up-and-down component.
universal soil loss equation The equation that represents the amount of soil moved by water.
wind erosion equation The equation that represents the amount of soil particles that are moved by wind.
wilting point The level of soil water at which plants lose the ability to support themselves because the soil water that remains is held more strongly than the plant’s ability to absorb it.
aridisols Soil in dry environments characterized by eluvial horizons that undergo relatively little leaching.
capillary water Water that fills a soil’s micropores and is held with moderate force.
carbonation and solution A form of decomposition in which carbon dioxide combines with water to form carbonic acid, which dissolves minerals within rocks and thereby opens spaces.
cation exchange capacity A soil’s ability to hold positively charged nutrients.
cations Positively charged ions.
eluvial The soil layer from which minerals are leached as water percolates through the soil.
illuvial A soil layer that accumulates the minerals that wash out from the eluvial horizon.
Sands Soil particles that can be seen with the unaided eye.
contour plowing Sowing crops in rows that cut across the slope.
agriculturists People who obtain food by changing natural ecosystems in a way that increases the amount of edible energy generated.
agroecosystems Simplified ecosystems that are set up and operated to produce food for people.
cereals Cultivated members of the grass family whose seeds (grains) are eaten by people or domesticated animals.
coarse grains Cereals used to feed livestock.
coevolutionary hypothesis The notion that agriculture evolved via a positive feedback loop that includes the human population and the plants and animals humans eat.
crop yield potential The degree to which farmers’ yields approach a theoretical maximum.
cultivars A shortened term for cultivated varieties that refers to plants people have bred for a specific trait or characteristic.
domestication The process by which a species is modified relative to its wild ancestors by selective breeding.
economies of scale Reductions in the unit costs of production as the quantity produced increases.
fungicides Chemicals designed to kill fungal diseases.
genetically modified Cultivars with genes from other species.
grains Seeds of cultivated members of the grass family that are eaten by people or domesticated animals.
harvest index The ratio of grain to total crop biomass.
herbicides Chemicals designed to kill plants.
high-yield varieties Cultivars bred to produce more edible food per unit area.
industrial livestock production systems Feedlots that produce less than 10 percent of their own feed.
integrated pest management The coordinated use of pest and environmental information along with available pest control methods to prevent unacceptable levels of pest damage by the most economical means, with the least possible hazard to people, property, and the environment.
intensification Reducing the use of land and labor while increasing the use of energy, materials, and water.
livestock Domestic animals raised for food and fiber.
monoculture Growing a single crop over a large area.
pasture Land used to graze livestock or cultivated to produce animal feed.
pests Species, such as insects, birds, or small mammals, that eat cultivated plants.
precision agriculture A system of agriculture that seeks to provide the inputs needed for crop growth (water and nutrients) and crop protection without deficiency or excess at each point in time during the growing season.
rangelands Relatively unaltered natural ecosystems where livestock graze natural vegetation that is predominantly native grasses, glasslike plants, forbs, or shrubs.
resource depletion hypothesis The notion that agriculture is a response to population growth and the best first principle.
selective breeding The process in which only individuals with traits desired by agriculturists are allowed to reproduce.
slash and burn The process in which an agroecosystem is created by burning a patch of forest.
technical change hypothesis The notion that agriculture arose with increasing human technical capabilities.
transgenic cultivars New cultivars that are created by moving genes from other species into crop species.
vegetable Edible seeds, roots, stems, leaves, bulbs, tubers, or nonsweet fruits of herbaceous plants.
yield The amount of edible food grown per land area.
afforestation Forest regrowth after a disturbance.
ecosystem management A harvest practice that balances human needs for wood as a raw material and an energy source with the forest’s provision of environmental services.
existence value Environmental contribution to human well-being even when the environment is not used.
extensive land uses Practices that use large land areas relative to other factors of production.
high-grading The practice of harvesting only those trees that give the highest immediate economic return.
intensive land uses Practices that use small land areas relative to other factors of production.
selective harvesting The process of cutting individual trees or small groups of trees.
shelterwood method A harvest method that removes trees in a series of two or three partial cuts that are designed to simulate a natural disturbance.
siltation Accumulation of eroded soil particles at the bottom of a water body.
sustainable yield of timber Harvesting timber no faster than the rate at which trees produce new supplies.
timber concession A contract that defines the rules for harvesting trees.
transportation costs The price paid for moving capital, labor, or other inputs into an area or moving agricultural goods, timber, or minerals out of an area.
transportation infrastructure Capital used in transportation, such as roads, railroad lines, and ports.
turbidity The degree to which light can penetrate water.
debt for nature swap An agreement wherein indebted nations are stricken of some portion of their debt in exchange for the designation of a portion of its forests as a national park where timber harvesting, agriculture, and mining are not allowed.
absolute water scarcity A ratio of annual water availability to population less than 1,700 m3 per person per year.
aquifer A soil layer in which all pore spaces are filled with water.
artesian well A well in which water rises to the surface due to internal pressure.
best available technology The most effective, economically achievable, state-of-the-art technology currently in use for controlling pollution, as determined by the U.S. EPA.
best practicable control technology Sets uniform, industrywide effluent standards that approximate the average amount of control achieved from existing technology in the specific industry.
biochemical oxygen demand The amount of oxygen required for aerobic organisms to decompose organic material in wastewater over a five- to twenty-day period; the usual measure is five days.
chemical oxygen demand The amount of oxygen required to oxidize the organic material in a sample.
cone of depression A drop in the water table around a well.
confined aquifer Groundwater that accumulates between two impermeable layers.
correlative rights doctrine Rules that govern water use and force landowners to share water.
desalinization Production of freshwater by removing the salt from salt water and brackish waters.
discharge Water returned after use, frequently at or near its source.
dissolved oxygen deficit The difference between the amount of oxygen in water when it is fully saturated and the amount of oxygen actually present.
drainage basin The area from which surface waters derive surface runoff and groundwater flows.
drip irrigation Slow, localized application of water just above the soil surface.
fecal coliform count Measures the number of coliform bacteria per 100 milliliters.
fishable A water body in which fish and shellfish can thrive and can be eaten safely by people.
freshwater Water that contains less than 1,000 milligrams per liter of dissolved solids.
groundwater Water that fills the pore spaces of an aquifer.
groundwater discharge Locations where groundwater resurfaces.
hydrologic cycle The flow of water from the ocean through the atmosphere to the land and back to the ocean.
infiltration Vertical movements of water through the soil.
instream Uses of water that occur without the water being diverted or withdrawn from surface water or groundwater.
membrane separation Physical separation of salt from water by pushing seawater through thin filters that do not allow minerals to pass.
nonpoint pollutants Pollutants that are not discharged or emitted from a specific point, such as a pipe or smokestack.
offstream Water that is withdrawn or diverted from surface water or groundwater.
overdraft Removing water from an aquifer faster than it is recharged.
pathogens Microorganisms that cause disease.
primary treatment Treatment of municipal wastes that removes large solids by mechanical techniques such as screens and settling tanks.
prior appropriation doctrine A practice dictating that no one owns the water in a stream and that all people, corporations, and municipalities have the right to use water for beneficial purposes.
privatization Selling a state-owned business to private investors.
reasonable use doctrine A doctrine that allows landowners to pump water for any beneficial use and does not recognize priority among users.
recharge area The area from which an aquifer receives its water.
reservoir A natural or artificial pond or lake that is used for water storage or regulation.
riparian water rights Laws that allow a landowner to use a share of the water that flows naturally past his or her property but do not entitle a landowner to divert water for storage in a reservoir for use in the dry season or to use water on land outside the watershed.
rule of absolute ownership The principle that allows landowners to pump as much groundwater as they want.
runoff Water that flows horizontally across the land toward the nearest surface water.
salt water Water that contains more than 35,000 milligrams per liter of dissolved solids, most often salt.
secondary treatment Treatment of municipal wastes that reduces the number of pathogens and accelerates the decomposition of organic wastes by enhancing the actions of aerobic and anaerobic bacteria.
sewage Waste and wastewater produced by residential and commercial users that is discharged into sewers.
sorption A process in which soil organic carbon soaks up or attracts agricultural chemicals.
subsidence A drop in land level due to the weight of the overlying material compressing soil particles after water has been withdrawn.
surface water Water that sits or flows above land, including lakes, oceans, rivers, and streams.
swimmable A category of water quality in which recreation in and on the water will not threaten people’s health.
tertiary treatment Treatment of municipal wastes in which undecomposed organic nutrients are separated from the wastewater, which is discharged back to the environment.
thermal desalting A process in which seawater is boiled or evaporated and the steam or evaporate is drawn off as pure water.
unconfined aquifer An aquifer that sits atop an impermeable layer.
water diversion Movement of water from surface water or groundwater over some distance to its point of use.
water pollution Purposeful or accidental addition of materials that contaminate water.
water table The top portion of the aquifer.
watershed The area from which surface waters derive surface runoff and groundwater flows.
waterworks Human systems for supplying water.
withdrawals Water that is removed from its source.
xenobiotics Organic compounds that are synthesized by humans and therefore are relatively resistant to organic decay.
unconfined aquifers unconfined aquifers
adiabatic lapse rate The rate of temperature change experienced by a parcel of air when it is moved vertically in the atmosphere such that it cannot exchange heat with its environment.
air pollutant Any gas or particle in the atmosphere that has the potential to harm life or property.
carcinogens Chemicals that cause cancer.
coarse fraction Particles that are bigger than 2.5 microns but smaller than 10 microns.
dose–response function The relationship between pollution and damage.
dust Solid material generated by crushing or grinding.
fuel NOx Produced when the nitrogen in fossil fuels is oxidized.
fumes Condensed vapors.
fumigation Mixing in the downward direction that generates very high ground-level concentrations.
horizontal mixing Refers to how far a pollutant is carried from its source.
looping A pattern in which a plume rises and falls in an unstable atmosphere.
maximum mixing depth The upper bound on vertical mixing set by the altitude at which there is a positive relationship between temperature and altitude.
mist An aerosol that consists of liquids.
mobile sources Moving sources of pollution, such as cars or trucks.
NAAQS The National Ambient Air Quality Standards established by the U.S. federal government to limit air pollution.
neutrally stable Environmental conditions in which the observed environmental lapse rate is the same as the adiabatic lapse rate.
new source performance standards Regulations that govern emissions of air pollutants from new plants.
nonattainment areas Locations where concentrations remain above the NAAQS.
primary air pollutants Pollutants that enter the atmosphere in a form that harms life or property.
primary particles Particulates that are emitted directly by economic activities.
primary standards Environmental regulations designed to protect public health, including the health of sensitive populations such as asthmatics, children, and the elderly.
radiation inversions Short-lived inversions that occur daily due to radiational warming and cooling.
secondary air pollutants Pollutants that are formed when primary pollutants interact with sunlight and other gases in the atmosphere.
secondary particles Pollutants that are formed when particles emitted by human activity interact with natural components of the atmosphere.
secondary standards Regulations designed to protect public welfare, including protection against decreased visibility and damage to animals, crops, vegetation, and buildings.
smoke Particles that form during the combustion of fossil fuels.
stable atmosphere An atmosphere in which the observed lapse rate is slower than the adiabatic lapse rate.
state implementation plan Describes how states will satisfy the NAAQS.
stationary sources Places or objects from which pollutants are released and that do not move around.
subsidence inversion An increase in temperature with altitude produced by the adiabatic warming of a layer of subsiding air.
thermal NOx A process in which burning fossil fuels creates temperatures high enough to oxidize atmospheric nitrogen (N2) and oxygen (O2) to form nitrogen oxides.
thoracic particles Particles smaller than 10 microns.
ultrafine particles Particles smaller than 0.1 microns.
unstable An atmosphere in which the observed environmental lapse rate is faster than the adiabatic lapse rate.
vertical mixing The altitude to which a pollutant is mixed.
weekend effect Differences in climate variables on Saturday or Sunday relative to observations Monday through Friday.
wet deposition The process in which sulfate particles (SO4) are removed from the atmosphere by precipitation.
dose response function The relationship between pollution and damage.
stable An atmosphere in which the observed lapse rate is slower than the adiabatic lapse rate.
coal benefaction A process in which coal is cleaned by being crushed, screened, and suspended in a liquid, where the solid impurities settle out.
continuous mining techniques Recovery in which mining machines allow the roof to cave in after the machine has removed all of the coal and “backs away” from the seam.
conventional fossil fuels Coal, oil, and natural gas that supply nearly all of the energy provided by fossil fuels due to their low cost.
extraction efficiency The fraction of the resource removed from its location in the environment.
kerogen An insoluble organic material that is the main precursor of crude oil and natural gas.
mountaintop removal A coal recovery practice in which vegetation and soil are removed from a mountaintop, explosives are used to separate coal from the rocks, and the rocks are subsequently dumped into a nearby valley.
oil refinery An industrial installation that breaks and separates the long-chain carbon molecules of crude oil into groups of shorter-chain molecules known as refined petroleum products.
operable capacity The maximum rate of oil production that can be sustained during the following six months.
overburden Soil and rock above a coal seam or other mineral source.
porosity A measurement of space between soil particles that can hold water or oil.
primary recovery Oil that is pushed to the surface by the pressure gradient in the field.
proved reserves Volumes of crude oil that geological and engineering information shows, beyond reasonable doubt, to be recoverable in the future from a reservoir under existing economic and operating conditions.
refined petroleum products Carbon molecules derived from crude oil.
revisions Changes (either positive or negative) to proved reserves that are generated by new information other than an increase in acreage.
room and pillar A coal extraction technique that leaves pillars of coal to prevent the ceiling from collapsing.
seam A naturally occurring layer of coal usually thick enough to be mined for profit.
secondary recovery The injection of water into an oil field to push additional quantities of oil toward the producing well and up to the surface.
surface mining techniques Coal recovery techniques that remove the soil and rock above coal seams, thereby exposing the seams.
tertiary methods Injection of heat or materials that reduce the viscosity or surface tension of crude oil, which makes it flow more easily toward the surface.
unconventional fossil fuels Fossil fuels, such as oil shales and tar sands, that may eventually replace conventional fossil fuels.
underground mining techniques Coal recovery techniques in which shafts are drilled to the seam to give miners access.
wildcatting Drilling wells into formations not previously known to contain oil or natural gas.
yield per effort The ratio of resource obtained relative to the effort used to obtain it.
reserves Volumes of crude oil that geological and engineering information shows, beyond reasonable doubt, to be recoverable in the future from a reservoir under existing economic and operating conditions.
breeder reactor A nuclear reactor that manu- factures more fissionable isotopes than it consumes.
containment The control of a nuclear fission reaction so that harmful radiation is not released to the environment.
control rods Devices in the core of a reactor that absorb neutrons and are used to con- trol the rate of fission and to stop the chain reaction.
conversion The step in the nuclear fuel cycle in which solid uranium oxide (U3O8) is con- verted into the gas uranium hexafluoride (UF6).
decommissioning The process of closing down and removing a nuclear reactor after its useful life has come to an end.
enrichment The physical process of increasing the concentration of the uranium-235 isotope relative to the predominant uranium-238 iso- tope in natural uranium.
exploration The search for and identification of new deposits of a natural resource.
fertile An atom or a collection of atoms that can produce fissile atoms under neutron irradiation. Fertile atoms or collections of atoms generally themselves do not undergo induced fission.
fissile Any nucleus capable of undergoing fis-sion by neutrons.
fuel assemblies Bundles of hollow metal rods containing uranium oxide pellets; used to fuel a nuclear reactor.
fuel rods A long, slender tube that holds fuel (fissionable material) for nuclear reactor use.
geologic disposal The long-term storage of nuclear waste in geologic formations in Earth’s crust.
interim storage Providing safe and secure stor-age in the near term to support continu-ing operations in the interim period until long-term storage or disposition actions are implemented.
milling milling Taking uranium ore extracted from Earth’s crust and chemically processing it to prepare uranium concentrate (U3O8), sometimes called uranium octaoxide or “yellowcake.”
mining The extraction of valuable minerals or other geological materials from Earth, usually (but not always) from an ore body, vein, or (coal) seam.
moderators moderators Components of nuclear reactors that slow neutrons, thereby increasing their chances of being absorbed by fissile material. Natural water, heavy water, and nuclear-grade graphite are the most common moderators.
nuclear proliferation and diversion The spread from nation to nation of nuclear technology, including nuclear power plants but especially nuclear weapons.
permanent waste disposal The storage of nuclear waste in a form and location for a very long time.
pressurizer pressurizer A high-strength tank containing steam and water used to control the pressure of the reactor coolant in the primary loop in a nuclear power plant.
primary coolant The coolant in a nuclear power plant that first comes in contact with the core.
reactor core The core of a nuclear reactor, con-sisting of the fuel, moderator (in the case of thermal reactors), and coolant.
reactor vessel A cylindrical steel vessel in a nuclear power plant that contains the core, control rods, coolant, and structures that sup-port the core.
reprocessing The treatment of spent (irradi-ated) reactor fuel to separate plutonium from uranium and other fission products.
secondary coolant secondary coolant In a nuclear power plant, the part of the cooling system that absorbs heat from the primary coolant.
spent nuclear fuel Fuel rods that no longer contain enough fissionable uranium to be efficiently used to produce power.
turbine generator A rotary engine driven by the pressure of water, air, or steam against the curved vanes of a wheel to transform heat, chemical energy, or water pressure into mechanical energy.
vitrification A method of immobilizing nuclear waste that produces a glasslike solid that per-manently captures the radioactive materials.
fabrication The process through which fis-sionable material is configured into precisely shaped fuel or target elements and made ready for use in a nuclear reactor.
bioenergy Energy derived from biological sources.
biofuels Fuels made from cellulosic biomass resources, such as ethanol, biodiesel, and methanol.
biomass feedstocks The sources for bioenergy and biofuels, including forest and agricultural biomass, as well as the organic portions of municipal solid wastes.
biopower Electricity generated from the com-bustion of biological sources.
end use efficiency The efficiency with which energy is converted to useful work or heat at the point of end use.
energy density The amount of energy stored per unit weight, volume, or space.
energy end use A set of devices, products, and systems that use energy for the same or similar purposes. Examples include transportation, cooking, lighting, heating, and refrigeration.
ethanol A chemical formed by fermentation or synthesis used as a raw material in a wide range of industrial and chemical processes. An alternative automotive fuel that is usually blended with gasoline to form gasohol.
flash steam power plants The most common type of geothermal power plant in which steam, once it has been separated from the water, is piped to a powerhouse where it is used to drive a steam turbine, which in turn generates electricity.
forestry residues Forms of biomass (bark, branches) left over from the harvesting of timber that are potential sources of energy.
fuel cell An electrochemical engine (no moving parts) that converts the chemical energy of a fuel, such as hydrogen, and an oxidant, such as oxygen, directly to electricity.
geothermal direct use The use of geothermal energy for a variety of applications including space heating, agriculture, aquaculture, rec-reation, medical (balneology), and industrial use (process heating).
geothermal fields An accumulation of geothermal energy that can be developed for human use.
geothermal heat pump A heat pump that uses Earth as a heat source and heat sink.
ocean thermal energy conversion Electricity generation by making use of the temperature difference (as much as 20°C, or 68°F, in the tropics) between the top and bottom layers of the ocean to convert a fluid to vapor, which in turn powers a turbine generator.
photovoltaic effect The generation of an electrical current in a circuit containing a photosen-sitive device when the device is illuminated by visible or nonvisible light.
power density The rate of doing work per unit area or volume.
primary mill residues Biomass produced from the processing of timber (such as at sawmills) that is a potential source of energy.
pumped storage plant A plant that usually generates electric energy during peak load periods by using water previously pumped into an elevated storage reservoir during off-peak periods when excess generating capacity is available to do so. When additional generating capacity is needed, the water can be released from the reservoir through a conduit to turbine generators located in a power plant at a lower level.
pyrolysis Decomposition of a chemical by extreme heat.
solar thermal system A system that uses radia-tion from the sun to produce heat energy.
tidal energy Electricity generated by capture of the energy contained in moving water masses due to tides.
wind energy Energy derived from the kinetic energy of the wind.
wind farm A collection of wind turbines all in the same location, used for the generation of electricity.
agricultural residues A potential source of biomass energy consisting of plant parts remaining in a field after the harvest of a crop, including stalks, stems, leaves, roots, and weeds.
biochemicals Chemicals produced by, or derived from, living organisms.
biodiesel A less polluting fuel for most diesel internal combustion and turbine engines pro-duced from a range of biomass-derived feed-stocks including oilseeds, waste vegetable oils, cooking oil, animal fats, and trap grease.
atmospheric emissions The release of gases or particulates into the atmosphere.
black smokers A chimneylike structure on theseafloor made of metal sulfides, out of whichflow hot (~350°C) fluids that look like blacksmoke. The black color of the fluid is due tomineral particles within it.
cradle-to-grave A comprehensiveexamination of the environmentaland economic effects of a product at everystage of its existence, from production to disposaland beyond.
life cycle analysis A comprehensiveexamination of the environmentaland economic effects of a product at everystage of its existence, from production to disposaland beyond.
dematerialization A reduction in the amount ofmaterial required to produce a good or service.
dissipation The release of wastes by breakingup and scattering by dispersion.
economic energy cost The quantity of energyrequired to extract and process a unit of natural resource.
evaporites Salts deposited by evaporation ofseawater.
extractive wastes A waste generated in the processof extracting a natural resource (mineral,energy, timber) from the environment.
geochemical exploration A method of mineralexploration that is based on the physical andchemical processes that have produced theobserved distributions in Earth.
geologic exploration A method of oil and mineralexploration that employs basic data gatheringand mapping skills. Surface data areused to project features to the subsurface andinterpret the subsurface geology.
geophysical exploration A method of oilexploration that measures the physical propertiesof minerals and rocks to suggest thepresence or absence of economic oil and gasconcentrations.
hydrothermal solutions Hot water that concentrates,transports, or deposits minerals.
intensity of use The amount of energy or materialused per unit of economic activity.
mineral resource A concentration or occurrenceof natural, solid, inorganic, or fossilizedorganic material in or on Earth’s crust in suchform and quantity and of such a grade orquality that it has reasonable prospects foreconomic extraction.
municipal solid waste Solid waste originatingfrom homes, industries, businesses, demolition,land clearing, and construction.
placer deposits Naturally occurring localizedconcentrations of economically important oreminerals, formed as a result of physical processesat or near Earth’s surface.
postconsumer content A material or finishedproduct that has served its intended use andhas been diverted or recovered from wastedestined for disposal, having completed itslife as a consumer item.
recyclable products Materials capable of beingrecycled.
recycled-content products Goods that containmaterial that has been recycled.
recycling The process by which materials thatwould otherwise become solid waste are collected,separated or processed, and returnedto the economic mainstream to be reused inthe form of raw materials or finished goods.
remanufacturing The process of restoring useddurable products to “new” condition, to beused in their original function, by replacingworn or damaged parts.
reserve base That part of an identified naturalresource that meets specified minimum physicaland chemical criteria related to currentmining and production practices, includingthose for grade, quality, thickness, and depth.
reuse Using a product or component of municipalsolid waste in its original form more thanonce—such as refilling a glass bottle that hasbeen returned or using a coffee can to holdnuts and bolts.
source reduction Reducing the amount and/or toxicity of an item before it is generated(examples include buying an item with lesspackaging or using a nontoxic cleaningcompound).
stripping ratio The unit amount of overburdenthat must be removed to gain access to a similarunit amount of coal or mineral material.
variable rate pricing system A method of chargingfor waste disposal in which residents arecharged different amounts per unit of garbage.
proportional pricing system A method ofcharging for waste disposal in which residentspay the same amount of money for eachunit of waste they set out for collection (perhaps$1.50 for each 30-gallon bag). The price isbased on the number of bags, tags, or stickers(usually sold at local retail stores or municipaloffices) the resident uses.
assurance bonding Bonds put up by firms or households to cover the potential damage of their actions now or in the future.
Reformulated gasoline gasoline treated so as to be in closer compliance to air quality standards