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A
abatement: Reducing the degree or
intensity of, or eliminating, pollution.
absorption: the penetration of
atoms, ions, or molecules into the bulk mass
of a substance.
acceptable daily Intake (ADI):
Estimate of the largest amount of chemical
to which a person can be exposed on a daily
basisthat is not anticipated to result in
adverse effects (usually expressed in
mg/kg/day). Same as RfD.
acid deposition: A complex
chemical and atmospheric phenomenon that
occurs when emissions of sulfur and nitrogen
compounds and other substances are
transformed by chemical processes in the
atmosphere, often far from the original
sources, and then deposited on earth in
either wet or dry form. The wet forms,
popularly called "acid rain," can
fall as rain, snow, or fog. The dry forms
are acidic gases or particulates.
acid mine drainage: Drainage of
water from areas that have been mined for
coal of other mineral ores; the water has
low pH, sometimes less than 2.0 (is acid),
because of its contact with sulfur-bearing
material; acid drainage is harmful because
it often kills aquatic organisms.
acid rain: Precipitation which has
been rendered (made) acidic by airborne
pollutants.
acidic: The condition of water or
soil that contains a sufficient amount of
acid substances to lower the pH below 7.0
action levels: 1. Regulatory
levels recommended by EPA for enforcement by
FDA and USDA when pesticide residues occur
in food or feed commodities for reasons
other than the direct application of the
pesticide. As opposed to
"tolerances" which are established
for residues occurring as a direct result of
proper usage, action levels are set for
inadvertent residues resulting from previous
legal use or accidental contamination. 2. In
the Superfund program, the existence of a
contaminant concentration in the environment
high enough to warrant action or trigger a
response under SARA and the National Oil and
Hazardous Substances Contingency Plan. The
term is also used in other regulatory
programs.
activated sludge process: A sewage
treatment process by which bacteria that
feed on organic wastes are continuously
circulated and put in contact with organic
waste in the presence of oxygen to increase
the rate of decomposition.
active ingredient: In any
pesticide product, the component that kills,
or otherwise controls, target pests.
Pesticides are regulated primarily on the
basis of active ingredients.
acute effect: An adverse effect on
any living organism in which severe symptoms
develop rapidly and often subside after the
exposure stops.
adaptation: Changes in an
organism's structure or habits that help it
adjust to its surroundings.
additive effect: Combined effect
of two or more chemicals equal to the sum of
their individual effects.
advanced wastewater treatment: Any
treatment of sewage that goes beyond the
secondary or biological water treatment
stage and includes the removal of nutrients
such as phosphorus and nitrogen and a high
percentage of suspended solids. (See
primary, secondary treatment.)
aeration: A process which promotes
biological degradation of organic matter in
water. The process may be passive (as when
waste is exposed to air), or active (as when
a mixing or bubbling device introduces the
air).
aerobic treatment: Process by
which microbes decompose complex organic
compounds in the presence of oxygen and use
the liberated energy for reproduction and
growth. (Such processes include extended
aeration, trickling filtration, and rotating
biological contactors.)
aerosol: A suspension of liquid or
solid particles in a gas.
aggregate: A mass or cluster of
soil particles, often having a
characteristic shape.
agricultural waste: Poultry and
livestock manure, and residual materials in
liquid or solid form generated from the
production and marketing of poultry,
livestock, furbearing animals, and their
products. Also includes gra in, vegetable,
and fruit harvest residue.
agrochemical: Synthetic chemicals
(pesticide and fertilizers) used in
agricultural production.
air emissions: Gas emitted into
the air from industrial and chemical
processes, such as ozone, carbon monoxide,
nitrogen oxide, nitrogen dioxide, sulfur
dioxide and others.
air mass: A large volume of air
with certain meteorological or polluted
characteristics, e,g, a heat inversion or
smogginess-while in one location. The
characteristics can change as the air mass
moves away.
air pollutant: Any substance in
air that could, in high enough
concentration, harm man, other animals,
vegetation, or material. Pollutants may
include almost any natural or artificial
composition of airborne matter capable of
being airborne. They may be in the form of
solid particles, liquid droplets, gases, or
in combination thereof. Generally, they fall
into two main groups: (1) those emitted
directly from identifiable sources and (2)
those produced in the air by interaction
between two or more primary pollutants, or
by reaction with normal atmospheric
constituents, with or without
photoactivation. Exclusive of pollen, fog,
and dust, which are of natural origin, about
100 contaminants have been identified and
fall into the following categories: solids,
sulfur compounds, volatile organic
chemicals, nitrogen compounds, oxygen
compounds, halogen compounds, radioactive
compounds, and odors.
air quality criteria: The levels
of pollution and lengths of exposure above
which adverse health and welfare effects may
occur.
air quality standards: The level
of pollutants prescribed by regulations that
may not be exceeded during a given time in a
defined area.
air stripping: A treatment system
that removes volatile organic compounds
(VOCs) from contaminated ground water or
surface water by forcing an airstream
through the water and causing the compounds
to evaporate.
airborne particulates: Total
suspended particulate matter found in the
atmosphere as solid particles or liquid
droplets. Chemical composition of
particulates varies widely, depending on
location and time of year. Airborne
particulates include: windblown dust,
emissions from industrial processes, smoke
from the burning of wood and coal, and motor
vehicle or non-road engine exhausts. exhaust
of motor vehicles.
algae: Chiefly aquatic, eucaryotic
one-celled or multicellular plants without
true stems, roots and leaves, that are
typically autotrophic, photosynthetic, and
contain chlorophyll. Algae are not typically
found in groundwater. They also may be
attached to structures, rocks or other
submerged surfaces. They are food for fish
and small aquatic animals. Excess algal
growths can impart tastes and odors to
potable water. Algae produce oxygen during
sunlight hours and use oxygen during the
night hours. Their biological activities
appreciably affect the pH and dissolved
oxygen of the water.
algal bloom: Sudden, massive
growths of microscopic and macroscopic plant
life, such as green or bluegreen algae,
which develop in lakes and reservoirs, which
can affect water quality adversely and
indicate potentially hazardous changes in
local water chemistry.
alkali: Various soluble salts,
principally of sodium, potassium, magnesium,
and calcium, that have the property of
combining with acids to form neutral salts
and may be used in chemical water treatment
processes.
alluvial: Relating to mud and/or
sand deposited by flowing water. Alluvial
deposits may occur after a heavy rain storm.
alternative fuels: Substitutes for
traditional liquid, oil-derived motor
vehicle fuels like gasoline and diesel.
Includesmethanol, ethanol, compressed
natural gas, and others.
ambient air: Any unconfined
portion of the atmosphere: open air,
surrounding air.
anaerobic: A biological process
which occurs in the absence of oxygen.
aqueous solubility: The extent to
which a compound will dissolve in water. The
log of solubility is generally inversely
related to molecular weight.
aquifer: An underground geological
formation, or group of formations,
containing usable amounts of groundwater
that can supply wells and springs.
aromatic: A type of hydrocarbon,
such as benzene or toluene, added to
gasoline in order to increase octane. Some
aromatics are toxic.
artesian: Water held under
pressure in porous rock or soil confined by
impermeable geologic formations. An artesian
well is free flowing.
asbestos abatement: Procedures to
control fiber release from
asbestos-containing materials in a building
or to remove them entirely, including
removal, encapsulation, repair, enclosure,
encasement, and operations and maintenance
programs.
asbestos: A mineral fiber that can
pollute air or water and cause cancer or
asbestosis when inhaled. EPA has banned or
severely restricted its use in manufacturing
and construction.
attainment area: An area
considered to have air quality as good as or
better than the national ambient air quality
standards as defined in the Clean Air Act.
An area may be an attainment area for one
pollutant and a non-attainment area for
others.
B
backflow: A reverse flow
condition, created by a difference in water
pressures, which causes water to flow back
into the distribution pipes of a potable
water supply from any source or sources
other than an intended source. Also see
backsiphonage and cross-connection.
background level: In air pollution
control, the concentration of air pollutants
in a definite area during a fixed period of
time prior to the starting up or on the
stoppage of a source of emission under
control. In toxic substances monitoring, the
average presence in the environment,
originally referring to naturally occurring
phenomena.
bacteria: (Singular 'bacterium')
Microscopic living organisms that can aid in
pollution control by metabolizing organic
matter in sewage, oil spills or other
pollutants. However, bacteria in soil, water
or air can also cause human, animal and
plant health problems.
baffle: A flat board or plate,
deflector, guide or similar device
constructed or placed in flowing water or
slurry systems to cause more uniform flow
velocities, to absorb energy, and to divert,
guide, or agitate liquids (water, chemical
solutions, slurry).
berm: A sloped wall or embankment
(typically constructed of earth, hay bales,
or timber framing) used to prevent inflow or
outflow of material into/from an area.
best available technology (BAT):
The best technology treatment techniques, or
other means which the Administrator finds,
after examination for efficacy under field
conditions and not solely under laboratory
conditions, are available (taking cost into
consideration). For the purposes of setting
MCLs for synthetic organic chemicals, any
BAT must be at least as effective as
granular activated carbon.
best management practices (BMPs):
Structural, nonstructural and managerial
techniques that are recognized to be the
most effective and practical means to
control nonpoint source pollutants yet are
compatible with the productive use of the
resource to which they are applied. BMPs are
used in both urban and agricultural areas.
bioaccumulants: Substances that
increase in concentration in living
organisms as they take in contaminated air,
water, or food because the substances are
very slowly metabolized or excreted.
bioassay: A method used to
determine the toxicity of specific chemical
contaminants. A number of individuals of a
sensitive species are placed in water
containing specific concentrations of the
contaminant for a specified period of time.
bioaugmentation: The introduction
of cultured microorganisms into the
subsurface environment for the purpose of
enhancing bioremediation of organic
contaminants. Generally the microorganisms
are selected for their ability to degrade
the organic compounds present at the
remediation site. The culture can be either
an isolated genus or a mix of more than one
genera. Nutrients are usually also blended
with the aqueous solution containing the
microbes to serve as a carrier and
dispersant. The liquid is introduced into
the subsurface under natural conditions
(gravity fed) or injected under pressure.
biochemicals: Chemicals that are
either naturally occurring or identical to
naturally occurring substances. Examples
include hormones, pheromones, and enzymes.
Biochemicals function as pesticides through
non-toxic, non-lethal modes of action, such
as disrupting the mating pattern of insects,
regulating growth, or acting as repellants.
Biochemicals tend to be environmentally
compatible and are thus important to
Integrated Pest Management programs.
biodegradable: The ability of a
substance to be broken down physically
and/or chemically by microorganisms. For
example, many chemicals, food scraps,
cotton, wool, and paper are bio-degradable;
plastics and polyester generally are not.
biodiversity: The number and
variety of different organisms in the
ecological complexes in which they naturally
occur. Organisms are organized at many
levels, ranging from complete ecosystems to
the biochemical structures that are the
molecular basis of heredity. Thus, the term
encompasses different ecosystems, species,
and genes that must be present for a healthy
environment. A large number of species must
characterize the food chain, representing
multiple predator-prey relationships.
biologicals: Vaccines, cultures
and other preparations made from living
organisms and their products, intended for
use in diagnosing, immunizing, or treating
humans or animals, or in related research.
biomass: All of the living
material in a given area; often refers to
vegetation.
biome: Entire community of living
organisms in a single major ecological area.
bioremediation: The use of living
organisms (e.g., bacteria) to clean up oil
spills or remove other pollutants from soil,
water, and wastewater, use of organisms such
as non-harmful insects to remove
agricultural pests or counteract diseases of
trees, plants, and garden soil.
biosphere: The portion of Earth
and its atmosphere that can support life.
biotechnology: Techniques that use
living organisms or parts of organisms to
produce a variety of products (from
medicines to industrial enzymes) to improve
plants or animals or to develop
microorganisms to remove toxics from bodies
of water, or act as pesticides.
black water: Water that contains
animal, human, or food waste.
bloom (algal): A proliferation of
algae and/or higher aquatic plants in a body
of water; often related to pollution,
especially when pollutants accelerate
growth.
bog: A type of wetland that
accumulates appreciable peat deposits. Bogs
depend primarily on precipitation for their
water source, and are usually acidic and
rich in plant residue with a conspicuous mat
of living green moss.
bottom ash: The non-airborne
combustion residue from burning pulverized
coal in a boiler; the material which falls
to the bottom of the boiler and is removed
mechanically; a concentration of the
non-combustible materials, which may include
toxics.
brackish: Mixed fresh and salt
waters.
brine mud: Waste material, often
associated with well-drilling or mining,
composed of mineral salts or other inorganic
compounds.
buffer strips: Strips of grass or
other close-growing vegetation that separate
a waterway (ditch, stream, creek) from an
intensive land use area (subdivision, farm);
also referred to as filter strips, vegetated
filter strips, and grassed buffers.
by-product: Material, other than
the principal product, generated as a
consequence of an industrial process.
C
cancer: A disease characterized by
the rapid and uncontrolled growth of
aberrant cells into malignant tumors.
cap: A fairly impermeable seal,
usually composed of clay-type soil or a
combination of clay soil and synthetic
liner, which is placed over a landfill
during closure. The cap serves to minimize
leachate volume during biodegradation of the
waste by keeping precipitation from
percolating through the landfill. The cap
also keeps odors down and animal scavengers
from gathering.
carbon dioxide: A colorless,
odorless, gas produced by burning fossil
fuels, sometimes referred to as a green
house gas because it contibutes to earth
warming.
carbon monoxide: A colorless,
odorless, poisonous gas produced by
incomplete fossil fuel combustion.
carcinogen: Any substance that can
cause or aggravate cancer.
cask: A thick-walled container
(usually lead) used to transport radioactive
material. Also called a coffin.
catalyst: A substance that changes
the speed or yield of a chemical reaction
without being consumed or chemically changed
by the chemical reaction.
catalytic converter: An air
pollution abatement device that removes
pollutants from motor vehicle exhaust,
either by oxidizing them into carbon dioxide
and water or reducing them to nitrogen and
oxygen.
catalytic incinerator: A control
device that oxidizes volatile organic
compounds (VOCs) by using a catalyst to
promote the combustion process. Catalytic
incinerators require lower temperatures than
conventional thermal incinerators, thus
saving fuel and other costs.
chelation: A chemical complexing
(forming or joining together) of metallic
cations (such as copper) with certain
organic compounds, such as EDTA (ethylene
diamine tetracetic acid). Chelation is used
to prevent the precipitation of metals
(copper).
chisel plowing: Preparing
croplands by using a special implement that
avoids complete inversion of the soil as in
with conventional plowing. Chisel plowing
can leave a protective cover or crop
residues on the soil surface to help prevent
erosion and improve filtration.
chlorinated hydrocarbons: These
include a class of persistent,
broad-spectrum insecticides that linger in
the environment and accumulate in the food
chain. Among them are DDT, aldrin, dieldrin,
heptachlor, chlordane, lindane, endrin,
mirex, hexachloride, and toxaphene. Other
examples include TCE, used as an industrial
solvent.
chlorination: Adding chlorine to
water or wastewater, generally for the
purpose of disinfection, but frequently for
accomplishing other biological or chemical
results. Chlorine also is used almost
universally in manufacturing processes,
particularly for the plastics industry.
chlorofluorocarbons (CFCs): A
family of inert, nontoxic, and easily
liquified chemicals used in refrigeration,
air conditioning, packaging, insulation, or
as solvents and aerosol propellants. Because
CFCs are not destroyed in the lower
atmosphere they drift into the upper
atmosphere where their chlorine components
destroy ozone.
chlorophenoxy: A class of
herbicides that may be found in domestic
water supplies and cause adverse health
effects. Two widely used chlorophenoxy
herbicides are 2,4-D (2,4-Dichlorophenoxy
acetic acid) and 2,4,5-TP
(2,4,5-Trichlorophenoxy propionic acid
(silvex)).
chlorophyll: A chemical mixture or
compound found in the chloroplasts of plant
cells and gives plants their green color.
Plants use chlorophyll to convert the energy
of sunlight to food in the process known as
photosynthesis.
chlorosis: Discoloration of
normally green plant parts caused by
disease, lack of nutrients, or various air
pollutants.
cholinesterase: An enzyme found in
animals that regulates nerve impulses.
Cholinesterase inhibition is associated with
a variety of acute symptoms such as nausea,
vomiting, blurred vision, stomach cramps,
and rapid heart rate.
chronic effect: An adverse effect
on a human or animal in which symptoms recur
frequently or develop slowly over a long
period of time.
cistern: A small tank (usually
covered) or a storage facility used to store
water for a home or farm. Often used to
store rain water.
clarifer: A large circular or
rectangular tank or basin in which water is
held for a period of time, during which the
heavier suspended solids settle to the
bottom. Clarifiers are also called settling
basins and sedimentation basins.
class I area: Under the Clean Air
Act, a Class I area is one in which
visibility is protected more stringently
than under the national ambient air quality
standards; includes national parks,
wilderness area, monuments and other areas
of special national and cultural
significance.
clean coal technology: Any
technology not in widespread use prior to
the Clean Air Act amendments of 1990. This
Act will achieve significant reductions in
pollutants associated with the burning of
coal.
clean fuels: Blends or substitutes
for gasoline fuels, including compressed
natural gas, methanol, ethanol, liquified
petroleum gas, and others.
clear cut: Harvesting all the
trees in one area at one time, a practice
that can encourage fast rainfall or snowmelt
runoff, erosion, sedimentation of streams
and lakes, flooding, and destroys vital
habitat.
clear well: A reservoir for
storing filtered water of sufficient
quantity to prevent the need to vary the
filtration rate with variations in demand.
Also used to provide chlorine contact time
for disinfection.
climate change: This term is
commonly used interchangeably with
"global warming" and "the
greenhouse effect," but is a more
descriptive term. Climate change refers to
the buildup of man-made gases in the
atmosphere that trap the suns heat, causing
changes in weather patterns on a global
scale. The effects include changes in
rainfall patterns, sea level rise, potential
droughts, habitat loss, and heat stress. The
greenhouse gases of most concern are carbon
dioxide, methane, and nitrous oxides. If
these gases in our atmosphere double, the
earth could warm up by 1.5 to 4.5 degrees by
the year 2050, with changes in global
precipitation having the greatest
consequences.
cloning: In biotechnology,
obtaining a group of genetically identical
cells from a single cell; making identical
copies of a gene.
closed-loop recycling: Reclaiming
or reusing wastewater for non-potable
purposes in an enclosed process.
closure: The procedure a landfill
operator must follow when a landfill reaches
its legal capacity for solid waste: ceasing
acceptance of solid waste and placing a cap
on the landfill site. No more waste can be
accepted and a cap usually is placed over
the site. The cap is then planted with
grasses and other ground covers.
Post-closure care includes monitoring ground
water, landfill gases, and leachate
collection systems, sometimes for as long as
30 years.
coagulants: Chemicals that cause
very fine particles to clump together into
larger particles. This makes it easier to
separate the solids from the water by
settling, skimming, draining or filtering.
coastal zone: Lands and waters
adjacent to the coast that exert an
influence on the uses of the sea and its
ecology, or whose uses and ecology are
affected by the sea.
cohesion: Molecular attraction
which holds two particles together.
coliform organism: Microorganisms
found in the intestinal tract of humans and
animals. Their presence in water indicates
fecal pollution and potentially dangerous
bacterial contamination by disease-causing
microorganisms.
colloids: Very small, finely
divided solids (particles that do not
dissolve) that remain dispersed in a liquid
for a long time due to their small size and
electrical charge. When most of the
particles in water have a negative
electrical charge, they tend to repel each
other. This repulsion prevents the particles
from clumping together, becoming heavier,
and settling out.
combustion: 1. Burning, or rapid
oxidation, accompanied by release of energy
in the form of heat and light. A basic cause
of air pollution. 2. Refers to controlled
burning of waste, in which heat chemically
alters organic compounds, converting into
stable inorganics such as carbon dioxide and
water.
commercial waste: All solid waste
from businesses. This category includes, but
is not limited to, solid waste originating
in stores, markets, office buildings,
restaurants, shopping centers, and theaters.
comminution: Mechanical shredding
or pulverizing of waste. Used in both solid
waste management and wastewater treatment.
community water system (CWS): A
public water system which serves at least 15
service connections used by yearround
residents or regularly serves at least 25
year-round residents. Also see non-community
water system, transient water system and
non-transient non-community water system.
compost: Decomposed organic
material that is produced when bacteria in
soil break down garbage and biodegradable
trash, making organic fertilizer. Making
compost requires turning and mixing and
exposing the materials to air. Gardeners and
farmers use compost for soil enrichment. The
relatively stable humus material that is
produced from a composting process in which
bacteria in soil mixed with garbage and
degradable trash break down the mixture into
organic fertilizer.
compressed natural gas (CNG): An
alternative fuel for motor vehicles;
considered one of cleanest because of low
hydrocarbon emissions and its vapors are
relatively non-ozone producing. However, it
does emit a significant quantity of nitrogen
oxides.
condensation: The process by which
a liquid is removed from a vapor. In the
water cycle, water vapor rises, cools, and
condenses, sometimes clinging to tiny
particles of dust in the atmosphere.
Condensed water vapor either remains a
liquid or turns directly into a solid (ice,
hail or snow). Clouds are formed by
condensed water particles.
conductance: A rapid method of
estimating the dissolvedsolids content of a
water supply. The measurement indicates the
capacity of a sample of water to carry an
electrical current, which is related to the
concentration of ionized substances in the
water.
cone of depression: The area
around a discharging well where the
hydraulic head (potentiometric surface) in
the aquifer has been lowered by pumping. In
an unconfined aquifer, the cone of
depression is a cone-shaped depression in
the water table where the media has actually
been dewatered.
confined aquifer: An aquifer in
which ground water is confined under
pressure which is significantly greater than
atmospheric pressure. See artesian aquifer.
consent decree: A legal document,
approved by a judge, that formalizes an
agreement reached between EPA and
potentially responsible parties (PRPs)
through which PRPs will conduct all or part
of a cleanup action at a Superfund site;
cease or correct actions or processes that
are polluting the environment; or otherwise
comply with EPA initiated regulatory
enforcement actions to resolve the
contamination at the Superfund site
involved. The consent decree describes the
actions PRPs will take and may be subject to
a public comment period.
conservation: Preserving and
renewing natural resources to assure their
highest economic or social benefit over the
longest period of time. Clean rivers and
lakes, wilderness areas, a diverse wildlife
population, healthy soil, and clean air are
natural resources worth conserving for
future generations.
construction and demolition waste:
Waste building materials, dredging
materials, tree stumps, and rubble resulting
from construction, remodeling, repair, and
demolition of homes, commercial buildings
and other structures and pavements. May
contain lead, asbestos, or other hazardous
substances.
consumptive use: Water removed
from available supplies without direct
return to a water resource system for uses
such as manufacturing, agriculture, and food
preparation.
contact pesticide: A chemical that
kills pests when it touches them, instead of
by ingestion. Also, soil that contains the
minute skeletons of certain algae that
scratch and dehydrate waxy-coated insects.
contaminant: Any physical,
chemical, biological, or radiological
substance or matter that has an adverse
affect on air, water, or soil.
continuous discharge: A permitted
release of pollutants into the environment
that occurs without interruption, except for
infrequent shutdowns for maintenance,
process changes, etc.
contour farming: A
conservation-based method of farming in
which all farming operations (for example,
tillage and planting) are performed across
(rather than up and down) the slope.
Ideally, each crop row is planted at right
angles to the ground slope.
contour strip farming: A kind of
contour farming in which row crops are
planted in strips, between alternating
strips of close-growing, erosionresistant
forage crops.
conventional filtration: A method
of treating water to remove particulates.
The method consists of the addition of
coagulant chemicals, flash mixing,
coagulation flocculation, sedimentation and
filtration.
conventional tillage: The
traditional method of farming in which soil
is prepared for planting by completely
inverting it with a moldboard plow.
Subsequent working of the soil with other
implements is usually performed to smooth
the soil surface. Bare soil is exposed to
the weather for some varying length of time
depending on soil and climatic conditions.
conveyance loss: Water lost in
conveyance (pipe, channel, conduit, ditch)
by leakage or evaporation.
core: The uranium-containing heart
of a nuclear reactor, where energy is
released.
cover crop: A crop that provides
temporary protection for delicate seedlings
and/or provides a canopy for seasonal soil
protection and improvement between normal
crop production periods. Except in orchards
where permanent vegetative cover is
maintained, cover crops usually are grown
for one year of less. When plowed under and
incorporated into the soil, cover crops are
also referred to as gren manure crops.
cradle-to-grave or manifest system:
A procedure in which hazardous materials are
identified and followed as they are
produced, treated, transported, and disposed
of by a series of permanent, linkable,
descriptive documents (e.g., manifests).
Commonly referred to as the cradle-to-grave
system.
criteria pollutants: The 1970
amendments to the Clean Air Act required EPA
to set National Ambient Air Quality
Standards for certain pollutants known to be
hazardous to human health. EPA has
identified and set standards to protect
human health and welfare for six pollutants:
ozone, carbon monoxide, total suspended
particulates, sulfur dioxide, lead, and
nitrogen oxide. The term, "criteria
pollutants" derives from the
requirement that EPA must describe the
characteristics and potential health and
welfare effects of these pollutants. It is
on the basis of these criteria that
standards are set or revised.
crop rotation: A system of farming
in which a regular succession of different
crops are planted on the same land area, as
opposed to growing the same crop time after
time (monoculture).
cryptosporidium: A protozoan
associated with the disease
cryptosporidiosis in humans. The disease can
be transmitted through ingestion of drinking
water, person-to-person contact, or other
exposure routes. Cryptosporidiosis may cause
acute diarrhea, abdominal pain, vomiting,
and fever that last 1-2 weeks in healthy
adults, but may be chronic or fatal in
immuno-compromised people.
cumulative exposure: The summation
of exposures of an organism to a chemical
over a period of time.
curie: A measure of radioactivity.
One Curie of radioactivity is equivalent to
3.7 x 1010 or 37,000,000,000 nuclear
disintegrations per second.
D
DDT: The first chlorinated
hydrocarboninsecticide chemical name:
Dichloro-Diphenyl-Trichloroethane. It has a
half-life of 15 years and can collect in
fatty tissues of certain animals. EPA banned
registration and interstate sale of DDT for
virtually all but emergency uses in the
United States in 1972 because of its
persistence in the environment and
accumulation in the food chain.
decant: To draw off the upper
layer of liquid (water) after the heavier
material (a solid or another liquid) has
settled.
decay products: Degraded
radioactive materials, often referred to as
"daughters" or
"progeny"; radon decay products of
most concern from a public health standpoint
are polonium-214 and polonium-218.
decomposition: The conversion of
chemically unstable materials to more stable
forms by chemical or biological action. If
organic matter decays when there is no
oxygen present (anaerobic conditions or
putrefaction), undesirable tastes and odors
are produced. Decay of organic matter when
oxygen is present (aerobic conditions) tends
to produce much less objectionable tastes
and odors.
decontamination: Removal of
harmful substances such as noxious
chemicals, harmful bacteria or other
organisms, or radioactive material from
exposed individuals, rooms and furnishings
in buildings, or the exterior environment.
deep well injection: A process by
which waste fluids are injected deep below
the surface of the earth.
defoliant: An herbicide that
removes leaves from trees and growing
plants.
degasification: A water treatment
process which removes dissolved gases from
the water. The gases may be removed by
either mechanical or chemical treatment
methods or a combination of both.
degradation: Chemical or
biological breakdown of a complex compound
into simpler compounds.
denitrification: Bacterial
reduction of nitrite to gaseous nitrogen
under anaerobic conditions.
density: A measure of how heavy a
solid, liquid, or gas is for its size.
Density is expressed in terms of weight per
unit volume, that is, grams per cubic
centimeter or pounds per cubic foot. The
density of water is 1.0 gram per cubic
centimeter or about 62.4 pounds per cubic
foot.
dermal toxicity: The ability of a
pesticide or toxic chemical to poison people
or animals by contact with the skin.
desalination: 1) Removing salts
from ocean or brackish water by using
various technologies. 2) Removal of salts
from soil by artificial means, usually
leaching.
desiccant: A chemical agent that
absorbs moisture; some desiccants are
capable of drying out plants or insects,
causing death.
designer bugs: Popular term for
microbes developed through biotechnology
that can degrade specific toxic chemicals at
their source in toxic waste dumps or in
ground water.
destratification: The development
of vertical mixing within a lake or
reservoir to eliminate (either totally or
partially) separate layers of temperature,
plant, or animal life. This vertical mixing
can be caused by mechanical means (pumps) or
through the use of forced air diffusers
which release air into the lower layers of
the reservoir.
detritus: Loose fragments,
particles, or grains formed by the
disintegration of rocks.
diatomaceous earth (diatomite): A
chalk-like material (fossilized diatoms)
used to filter out solid waste in wastewater
treatment plants, also used as an active
ingredient in some powdered pesticides.
diffusion: The movement of
suspended or dissolved particles from a more
concentrated to a less concentrated area.
The process tends to distribute the
particles more uniformly.
digestion: The biochemical
decomposition of organic matter, resulting
in partial gasification, liquefaction, and
mineralization of pollutants.
dimictic: Lakes and reservoirs
which freeze over and normally go through
two stratification and two mixing cycles
within a year.
dioxin: Any of a family of
compounds known chemically as
dibenzo-p-dioxins. Concern about them arises
from their potential toxicity and
contaminants in commercial products. Tests
on laboratory animals indicate that it is
one of the more toxic man-made compounds.
direct runoff: Water that flows
over the ground surface or through the
ground directly into streams, rivers, or
lakes.
discharge: Flow of surface water
in a stream or canal or the outflow of
ground water from a flowing artesian well,
ditch, or spring. Can also apply to
discharge of liquid effluent from a facility
or of chemical emissions into the air
through designated venting mechanisms.
disinfectant: Any oxidant,
including but not limited to chlorine,
chlorine dioxide, chloramines, and ozone,
that is added to water in any part of the
treatment or distribution process and is
intended to kill or inactivate pathogenic
microorganisms.
dispersant: A chemical agent used
to break up concentrations of organic
material such as spilled oil.
disposal: Final placement or
destruction of toxic, radioactive, or other
wastes; surplus or banned pesticides or
other chemicals; polluted soils; and drums
containing hazardous materials from removal
actions or accidental releases. Disposal may
be accomplished through use of approved
secure landfills, surface impoundments, land
farming, deep-well injection, ocean dumping,
or incineration.
dissolved oxygen: The oxygen
freely available in water, vital to fish and
other aquatic life and for the prevention of
odors. DO levels are considered a most
important indicator of a water body's
ability to support desirable aquatic life.
Secondary and advanced waste treatment are
generally designed to ensure adequate DO in
waste-receiving waters.
dissolved solids: Disintegrated
organic and inorganic material in water.
Excessive amounts make water unfit to drink
or use in industrial processes.
distillation: The act of purifying
liquids through boiling, so that the steam
condenses to a pure liquid and the
pollutants remain in a concentrated residue.
drainage: A technique to improve
the productivity of some agricultural land
by removing excess water from the soil;
surface drainage is accomplished with open
ditches; subsurface drainage uses porous
conduits (drain tile) buried beneath the
soil surface.
drawdown: 1) The drop in the water
table or level of water in the ground when
water is being pumped from a well. 2) The
amount of water used from a tank or
reservoir. 3) The drop in the water level of
a tank or reservoir.
dredging: Removal of mud from the
bottom of water bodies. This can disturb the
ecosystem and causes silting that kills
aquatic life. Dredging of contaminated muds
can expose biota to heavy metals and other
toxics. Dredging activities may be subject
to regulation under Section 404 of the Clean
Water Act.
dump: A land site where wastes are
discarded in a disorderly or haphazard
fashion without regard to protecting the
environment. Uncontrolled dumping is an
indiscriminate and illegal form of waste
disposal. Problems associated with dumps
include multiplication of disease-carrying
organisms and pests, fires, air and water
pollution, unsightliness, loss of habitat,
and personal injury.
dystrophic lakes: Acidic, shallow
bodies of water that contain much humus
and/or other organic matter; contain many
plants but few fish.
E
ecological impact: The effect that
a man-made or natural activity has on living
organisms and their non-living (abiotic)
environment.
ecological indicator: A
characteristic of the environment that, when
measured, quantifies magnitude of stress,
habitat characteristics, degree of exposure
to a stressor, or ecological response to
exposure. The term is a collective term for
response, exposure. The term is a collective
term for response, exposure, habitat, and
stressor indicators.
ecological risk assessment: The
application of a formal framework,
analytical process, or model to estimate the
effects of human actions(s) on a natural
resource and to interpret the significance
of those effects in light of the
uncertainties identified in each component
of the assessment process. Such analysis
includes initial hazard identification,
exposure and doseresponse assessments, and
risk characterization.
ecology: The study of the
relationships between all living organisms
and the environment, especially the totality
or pattern of interactions; a view that
includes all plant and animal species and
their unique contributions to a particular
habitat.
ecosystem: The interacting
synergism of all living organisms in a
particular environment; every plant, insect,
aquatic animal, bird, or land species that
forms a complex web of interdependency. An
action taken at any level in the food chain,
use of a pesticide for example, has a
potential domino effect on every other
occupant of that system.
effluent: Water or some other
liquid-raw, partially or completely
treated-flowing from a reservoir, basin,
treatment process or treatment plant.
electrodialysis: A process that
uses electrical current applied to permeable
membranes to remove minerals from water.
Often used to desalinize salty or brackish
water.
electrolyte: A substance which
dissociates (separates) into two or more
ions when it is dissolved in water.
electrostatic precipitator (ESP):
A device that removes particles from a gas
stream (smoke) after combustion occurs. The
ESP imparts an electrical charge to the
particles, causing them to adhere to metal
plates inside the precipitator. Rapping on
the plates causes the particles to fall into
a hopper for disposal.
emission: Pollution discharged
into the atmosphere from smokestacks, other
vents, and surface areas of commercial or
industrial facilities; from residential
chimneys; and from motor vehicle,
locomotive, or aircraft exhausts.
emission cap: A limit designed to
prevent projected growth in emissions from
existing and future stationary sources from
eroding any mandated reduction. Generally,
such provisions require any emission growth
from facilities under the restrictions be
offset by equivalent reductions at other
facilities under the same cap.
emissions trading: The creation of
surplus emission reductions at certain
stacks, vents, or similar emissions sources
and the use of this surplus to meet or
redefine pollution requirements applicable
to other emission sources. This allows one
source to increase emissions when another
sources reduces them, maintaining an overall
constant emission level. Facilities that
reduce emissions substantially may
"bank" their "credits"
or sell them to other industries.
encapsulation: The treatment of
asbestos-containing material with a liquid
that covers the surface with a protective
coating or embeds fibers in an adhesive
matrix to prevent their release into the
air.
endangered species: Animals,
birds, fish, plants, or other living
organisms threatened with extinction by
man-made or natural changes in their
environment. Requirements for declaring a
species endangered are contained in the
Endangered Species Act.
endangerment assessment: A
site-specific risk assessment of the actual
or potential danger to human health or
welfare and the environment from the release
of hazardous substances or waste. The
endangerment assessment document is prepared
in support of enforcement actions under
CERCLA or RCRA.
endemic: Something peculiar to a
particular people or locality, such as a
disease which is always present in the
population.
Endrin: a pesticide toxic to
freshwater and marine aquatic life that
produces adverse health effects in domestic
water supplies.
energy recovery: To capture energy
from waste through any of a variety of
processes (e.g., burning). Many new
technology incinerators are waste-to-energy
recovery units.
enrichment: The addition of
nutrients (e.g., nitrogen, phosphorus,
carbon compounds) from sewage effluent or
agricultural runoff to surface water,
greatly increases the growth potential for
algae and other aquatic plants.
enteric: Of intestinal origin,
especially applied to wastes or bacteria.
environment: The sum of all
external conditions affecting the life,
development and survival of an organism.
environmental assessment (EA): An
environmental analysis prepared pursuant to
the National Environmental Policy Act to
determine whether a federal action would
significantly affect the environment and
thus require a more detailed environmental
impact statement.
environmental audit: An
independent assessment (not conducted by
EPA) of a facility's compliance policies,
practices, and controls. Many pollution
prevention initiatives require an audit to
determine where wastes may be reduced or
eliminated or energy conserved. Many
supplemental environmental projects that
offset a penalty use audits to identify ways
to reduce the harmful effects of a
violation.
environmental equity: Equal
protection from environmental hazards for
individuals, groups, or communities
regardless of race, ethnicity, or economic
status.
environmental exposure: Human
exposure to pollutants originating from
facility emissions. Threshold levels are not
necessarily surpassed, but low level chronic
pollutant exposure is one of the most common
forms of environmental exposure.
environmental impact statement (EIS):
A document prepared by or for EPA which
identifies and analyzes, in detail,
environmental impacts of a proposed action.
As a tool for decision-making, the EIS
describes positive and negative effects and
lists alternatives for an undertaking, such
as development of a wilderness area.
(Required by NEPA : see Federal Law
Section).
environmental technology: An
all-inclusive term used to describe
pollution control devices and systems, waste
treatment processes and storage facilities,
and site remediation technologies and their
components that may be utilized to remove
pollutants or contaminants from, or to
prevent them from entering, the environment.
Examples include wet scrubbers (air), soil
washing (soil), granulated activated carbon
unit (water), and filtration (air, water).
Usually, this term applies to hardware-based
systems; however, it can also apply to
methods or techniques used for pollution
prevention, pollutant reduction, or
containment of contamination to prevent
further movement of the contaminants, such
as capping, solidification or vitrification,
and biological treatment.
enzyme: (a) any of numerous
proteins or conjugated proteins produced by
living organisms and functioning as
biochemical catalysts. (b) a protein that a
living organism uses in the process of
degrading a specific compound. The protein
serves as a catalyst in the compound's
biochemical transformation.
epidemic: Widespread outbreak of a
disease, or a large number of cases of a
disease in a single community or relatively
small area. Disease may spread from person
to person, and/or by the exposure of many
persons to a single source, such as a water
supply.
epidemiology: The study of the
occurrence and causes of health effects in
human populations. An epidemiological study
often compares two groups of people who are
alike except for one factor, such as
exposure to a chemical or the presence of a
health effect. The investigators try to
determine if any factor is associated with
thehealth effect.
erosion: The wearing away of land
surface by wind or water, intensified by
land-clearing practices related to farming,
residential or industrial development, road
building, or logging.
estuary: A complex ecosystem
between a river and near-shore ocean waters
where fresh and salt water mix. These
brackish areas include bays, mouths of
rivers, salt marshes, wetlands, and lagoons
and are influenced by tides and currents.
Estuaries provide valuable habitat for
marine animals, birds, and other wildlife.
ethanol: An alternative automotive
fuel derived from grain and corn; usually
blended with gasoline to form gasohol.
eutrophic lakes: Shallow, murky
bodies of water with concentrations of plant
nutrients causing excessive production of
algae.
eutrophication: The slow aging
process during which a lake, estuary, or bay
evolves into a bog or marsh and eventually
disappears. During the later stages of
eutrophication the water body is choked by
abundant plant life due to higher levels of
nutritive compounds such as nitrogen and
phosphorus. Human activities can accelerate
the process.
evaporation: The process by which
water or other liquid becomes a gas (water
vapor or ammonia vapor). Water from land
areas, bodies of water, and all other moist
surfaces is absorbed into the atmosphere as
a vapor.
evaporation ponds: Areas where
sewage sludge is dumped and dried.
evapotranspiration: The combined
processes of evaporation and transpiration.
It can be defined as the sum of water used
by vegetation and water lost by evaporation.
ex situ: Moved from its original
place; excavated; removed or recovered from
the subsurface.
exotic species: A species that is
not indigenous to a region.
explosive limits: The amounts of
vapor in the air that form explosive
mixtures; limits are expressed as lower and
upper limits and give the range of vapor
concentrations in air that will explode if
an ignition source is present.
exposure: Radiation or pollutants
that come into contact with the body and
present a potential health threat. The most
common routes of exposure are through the
skin, mouth, or by inhalation.
exposure assessment: The
determination or estimation (qualitative or
quantitative) of the magnitude, frequency,
duration, route, and extent (number of
people) of exposure to a chemical.
exposure level (chemical): The
amount (concentration) of a chemical at the
absorptive surfaces of an organism.
extremely hazardous substances (EHS):
Any of 366 (+ or:) chemicals or hazardous
substances identified by EPA on the basis of
hazard or toxicity and listed under EPCRA.
The list is periodically revised.
F
facilities plans: Plans and
studies related to the construction of
treatment works necessary to comply with the
Clean Water Act or RCRA. A facilities plan
investigates needs and provides information
on the cost effectiveness of alternatives, a
recommended plan, an environmental
assessment of the recommendations, and
descriptions of the treatment works, costs,
and a completion schedule.
facultative: Used to describe
organisms that are able to grow in either
the presence or absence of a specific
environmental factor (e.g., oxygen). See
also facultative anaerobe.
feasibility study: 1. Analysis of
the practicability of a proposal; e.g., a
description and analysis of potential
cleanup alternatives for a site such as one
on the National Priorities List. The
feasibility study usually recommends
selection of a cost-effective alternative.
It usually starts as soon as the remedial
investigation is underway; together, they
are commonly referred to as the
"RI/FS". 2. A small-scale
investigation of a problem to ascertain
whether a proposed research approach is
likely to provide useful data.
fecal coliform bacteria: Bacteria
found in the intestinal tracts of animals.
Their presence in water or sludge is an
indicator of pollution and possible
contamination by pathogens.
feedlot: A confined area for the
controlled feeding of animals. Tends to
concentrate large amounts of animal waste
that cannot be absorbed by the soil and,
hence, may be carried to nearby streams or
lakes by rainfall runoff.
feedstock: Raw material supplied
to a machine or processing plant from which
other products can be made. For example,
polyvinyl chloride and polyethylene are raw
chemicals used to produce plastic tiles,
mats, fenders, cushions, and traffic cones.
field capacity: The maximum amount
of water that a soil can retain after excess
water from saturated conditions has been
drained by the force of gravity.
filling: Depositing dirt, mud or
other materials into aquatic areas to create
more dry land, usually for agricultural or
commercial development purposes, often with
ruinous ecological consequences.
filter strip: Strip or area of
vegetation used for removing sediment,
organic matter, and other pollutants from
runoff and waste water.
filtration: A treatment process,
under the control of qualified operators,
for removing solid (particulate) matter from
water by means of porous media such as sand
or a man-made filter; often used to remove
particles that containing pathogens.
finished water: Water that has
passed through a water treatment plant; all
the treatment processes are completed or
"finished". This water is ready to
be delivered to consumers. Also called
product water.
first draw: The water that comes
out when a faucet in the kitchen or bathroom
is first opened, which is likely to have the
highest level of lead contamination from old
plumbing solder and pipes.
fish kill: When aquatic life
within a river, lake, or stream dies in a
mass extinction.
flare: A device that burns gaseous
materials to prevent them from being
released into the environment. Flares may
operate continuously or intermittently and
are usually found on top of a stack. Flares
also burn off methane gas in a landfill.
flash point: The lowest
temperature at which evaporation of a
substance produces enough vapor to form an
ignitable mixture with air.
flocculation: The gathering
together of fine particles in water by
gentle mixing after the addition of
coagulant chemicals to form larger
particles.
floodplain: Mostly level land
along rivers and streams that may be
submerged by floodwater. A 100-year
floodplain is an area which can be expected
to flood once in every 100 years.
flow rate: The rate, expressed in
gallons-or liters-per-hour, at which a fluid
escapes from a hole or fissure in a tank.
Such measurements are also made of liquid
waste, effluent, and surface water movement.
flue gas: The air coming out of a
chimney after combustion in the burner it is
venting. It can include nitrogen oxides,
carbon oxides, water vapor, sulfur oxides,
particles and many chemical pollutants.
flue gas desulfurization: A
technology that employs a sorbent, usually
lime or limestone, to remove sulfur dioxide
from the gases produced by burning fossil
fuels. Flue gas desulfurization is current
state-of-the art technology for major SO2
emitters, like power plants.
fluidized: A mass of solid
particles that is made to flow like a liquid
by injection of water or gas is said to have
been fluidized. In water treatment, a bed of
filter media is fluidized by backwashing
water through the filter.
flume: A natural or man-made
channel that diverts water.
fluoridation: The addition of a
chemical to increase the concentration of
fluoride ions in drinking water to a
predetermined optimum limit to reduce the
incidence (number) of dental caries (tooth
decay) in children. Defluoridation is the
removal of excess fluoride in drinking water
to prevent the mottling (brown stains) of
teeth.
fluorides: Gaseous, solid, or
dissolved compounds containing fluorine that
result from industrial processes. Excessive
amounts in food can lead to fluorosis.
fluorocarbons (FCs): Any of a
number of organic compounds analogous to
hydrocarbons in which one or more hydrogen
atoms are replaced by fluorine. Once used in
the United States as a propellant for
domestic aerosols, they are now found mainly
in coolants and some industrial processes.
FCs containing chlorine are called
chlorofluorocarbons (CFCs). They are
believed to be modifying the ozone layer in
the stratosphere, thereby allowing more
harmful solar radiation to reach the Earth's
surface.
fogging: Applying a pesticide by
rapidly heating the liquid chemical so that
it forms very fine droplets that resemble
smoke or fog. Used to destroy mosquitoes,
black flies, and similar pests.
food chain: A sequence of
organisms, each of which uses the next,
lower member of the sequence as a food
source.
formaldehyde: A colorless,
pungent, and irritating gas, CH20, used
chiefly as a disinfectant and preservative
and in synthesizing other compounds like
resins.
fossil fuel: Fuel derived from
ancient organic remains, e.g., peat, coal,
crude oil, and natural gas.
fresh water: Water that generally
contains less than 1,000
milligrams-per-liter of dissolved solids
friable: Capable of being
crumbled, pulverized, or reduced to powder
by hand pressure.
fuel economy standard: The
Corporate Average Fuel Economy Standard
(CAFE) effective in 1978. It enhanced the
national fuel conservation effort imposing a
miles-per-gallon floor for motor vehicles.
fuel efficiency: The proportion of
the energy released on combustion of a fuel
that is converted into useful energy.
fugitive emissions: Air pollutants
released to the air other than those from
stacks or vents; typically small releases
from leaks in plant equipment such as
valves, pump seals, flanges, sampling
connections, etc.
fume: Tiny particles trapped in
vapor in a gas stream.
fumigant: A pesticide vaporized to
kill pests. Used in buildings and
greenhouses.
fungi: Aerobic, multicellular,
nonphotosynthetic, heterotrophic
microorganisms. The fungi include mushrooms,
yeast, molds, and smuts. Most fungi are
saprophytes, obtaining their nourishment
from dead organic matter. Along with
bacteria, fungi are the principal organisms
responsible for the decomposition of carbon
in the biosphere. Fungi have two ecological
advantages over bacteria: (1) they can grow
in low moisture areas, and (2) they can grow
in low pH environments. gate valve: a valve
regulated by the position of a circular
plate.
fungicide: A pesticide used to
control or destroy fungi on food or grain
crops.
fungistat: A chemical that keeps
fungi from growing.
furrow irrigation: Irrigation
method in which water travels through the
field by means of small channels between
each row or groups of rows.
G
galvanize: To coat a metal
(especially iron or steel) with zinc.
Galvanization is the process of coating a
metal with zinc.
game fish: Species like trout,
salmon, or bass, caught for sport. Many of
them show more sensitivity to environmental
change than "rough" fish.
garbage: Animal and vegetable
waste resulting from the handling, storage,
sale, preparation, cooking, and serving of
foods.
gas chromatograph/mass spectrometer:
Highly sophisticated instrument that
identifies the molecular composition and
concentrations of various chemicals in water
and soil samples.
gasification: Conversion of solid
material such as coal into a gas for use as
a fuel.
gasohol: Mixture of gasoline and
ethanol derived from fermented agricultural
products containing at least nine percent
ethanol. Gasohol emissions contain less
carbon monoxide than those from gasoline.
gastroenteritis: An inflammation
of the stomach and intestine resulting in
diarrhea, with vomiting and cramps when
irritation is excessive. When caused by an
infectious agent, it is often associated
with fever.
genetic engineering: A process of
inserting new genetic information into
existing cells in order to modify an
organism for the purpose of changing
particular characteristics.
geographic information system (GIS):
A computer system designed for storing,
manipulating, analyzing, and displaying data
in a geographic context.
geological log: A detailed
description of all underground features
discovered during the drilling of a well
(depth, thickness and type of formations).
germicide: A substance formulated
to kill germs or microorganisms. The
germicidal properties of chlorine make it an
effective disinfectant.
giardia lamblia: Flagellate
protozoan which is shed during its cyst
stage into the feces of man and animals.
When water containing these cysts is
ingested, the protozoan causes a severe
gastrointestinal disease called giardiasis.
grain loading: The rate at which
particles are emitted from a pollution
source. Measurement is made by the number of
grains per cubic foot of gas emitted.
gram: A unit of mass equivalent to
one milliliter of water at 4 degrees
Celsius. 1/454 of a pound.
grassed waterway: Natural or
constructed watercourse or outlet that is
shaped or graded and established in suitable
vegetation for the disposal of runoff water
without erosion.
gray water: Domestic wastewater
composed of wash water from kitchen,
bathroom, and laundry sinks, tubs, and
washers.
greenhouse effect: The warming of
Earth's atmosphere attributed to a build-up
of carbon dioxide or other gases;some
scientists think that this build-up allows
the sun's rays to heat Earth, while
infra-red radiation makes the atmosphere
opaque to a counterbalancing loss of heat.
ground water: The supply of fresh
water found beneath the Earth's surface,
usually in aquifers, which supply wells and
springs. Because ground water is a major
source of drinking water, there is growing
concern over contamination from leaching
agricultural or industrial pollutants or
leaking underground storage tanks.
ground-water discharge: Ground
water entering near coastal waters which has
been contaminated by landfill leachate, deep
well injection of hazardous wastes, septic
tanks, etc.
gully erosion: Severe erosion in
which trenches are cut to a depth greater
than 30 centimeters (a foot). Generally,
ditches deep enough to cross with farm
equipment are considered gullies.
H
habitat: The place where a
population (e.g., human, animal, plant,
microorganism) lives and its surroundings,
both living and non-living.
half-life: 1. The time required
for a pollutant to lose half its affect on
the environment. For example, the
biochemical half-life of DDT in the
environment is 15 years of Radium. 1,580
years. 2. The time required for half of the
atoms of a radioactive element to undergo
self-transmutation or decay. 3. The time
required for the elimination of one half a
total dose from the body.
halogen: One of the chemical
elements chlorine, bromine, or iodine.
hard water: Alkaline water
containing dissolved salts that interfere
with some industrial processes and prevent
soap from lathering. Water may be considered
hard if it has a hardness greater than the
typical hardness of water from the region.
Some textbooks define hard water as water
with a hardness of more than 100 mgAL as
calcium carbonate.
hazard evaluation: A component of
risk assessment that involves gathering and
evaluating data on the types of health
injury or disease (e.g., cancer) that may be
produced by a chemical and on the conditions
of exposure under which injury or disease is
produced.
hazardous air pollutants: Air
pollutants which are not covered by ambient
air quality standards but which, as defined
in the Clean Air Act, may reasonably be
expected to cause or contribute to
irreversible illness or death. Such
pollutants include asbestos, beryllium,
mercury, benzene, coke oven emissions,
radionuclides, and vinyl chloride.
hazardous chemical: An EPA
designation for any hazardous material
requiring an MSDS under OSHA's Hazard
Communication Standard. Such substances are
capable of producing fires and explosions or
adverse health effects like cancer and
dermatitis. Hazardous chemicals are distinct
from hazardous waste.
hazardous substance: 1. Any
material that poses a threat to human health
and- /or the environment. Typical hazardous
substances are toxic, corrosive, ignitable,
explosive, or chemically reactive. 2. Any
substancedesignated by EPA to be reported if
a designated quantity of the substance is
spilled in the waters of the United States
or if otherwise released into the
environment.
hazardous waste: A subset of solid
wastes that pose substantial or potential
threats to public health or the environment
and meet any of the following criteria: it
is specifically listed as a hazardous waste
by EPA; exhibits one or more of the
characteristics of hazardous wastes
(ignitability, corrosiveness, reactivity,
and/or toxicity); o is generated by the
treatment of hazardous waste; or is
contained in a hazardous waste.
health advisory level: A
non-regulatory health-based reference level
of chemical traces (usually in ppm) in
drinking water at which there are no adverse
health risks when ingested over various
periods of time. Such levels are established
for one day, 10 days, long term and
life-time exposure periods. They contain a
large margin of safety.
heat island effect: A
"dome" of elevated temperatures
over an urban area caused by structural and
pavement heat fluxes, and pollutant
emissions.
heavy metal: Metallic elements
with high atomic weights, e.g., mercury,
chromium, cadmium, arsenic, and lead; can
damage living things at low concentrations
and tend to accumulate in the food chain.
herbaceous: Any of various types
of non-woody plants with green stems.
Herbaceous plants die down to ground level
in the winter.
herbicide: A pesticide designed to
control or kill plants, weeds, or grasses.
Almost 70% of all pesticide used by farmers
and ranchers are herbicides. These chemicals
have wide-ranging effects on non-target
species (other than those the pesticide is
meant to control).
herbivore: An animal that feeds on
plants.
heterotrophic microorganisms:
Bacteria and other microorganisms that use
organic matter synthesized by other
organisms for energy and growth.
high-density polyethylene: A
material used to make plastic bottles and
other products that produces toxic fumes
when burned.
high-level radioactive waste (HLW):
Waste generated in core fuel of a nuclear
reactor, found at nuclear reactors or by
nuclear fuel reprocessing; is a serious
threat to anyone who comes near the waste
without shielding.
histology: The study of the
structure of cells and tissues; usually
involves microscopic examination of tissue
slices.
host: 1. In genetics, the
organism, typically a bacterium, into which
a gene from another organism is
transplanted. 2. In medicine, an animal
infected or parasitized by another organism.
hot spot: Localized elliptical
areas with concentrations in excess of the
cleanup standard, either a volume defined by
the projection of the surface area through
the soil zone that will be sampled or a
discrete horizon within the soil zone that
will be sampled.
household waste (domestic waste):
Solid waste, composed of garbage and
rubbish, which normally originated in a
private home or apartment house. Domestic
waste may contain a significant amount of
toxic or hazardous waste.
humus: Organic portion of the soil
remaining after prolonged microbial
decomposition.
hydrocarbon: Chemicals that
consist entirely of hydrogen and carbon.
Hydrocarbons contribute to air pollution
problems like smog.
hydrochlorination: The application
of hypochlorite compounds to water for the
purpose of disinfection.
hydrogen peroxide: Hydrogen
peroxide is used to increase the dissolved
oxygen content of groundwater to stimulate
aerobic biodegradation of organic
contaminants. Hydrogen peroxide is
infinitely soluble in water, but rapidly
dissociates to form a molecule of water
[H(2)O] and one-half molecule of oxygen [O].
Dissolved oxygen concentrations of greater
than 1,000 mg/L are possible using hydrogen
peroxide, but high levels of D.O. can be
toxic to microorganisms.
hydrogen sulfide: Gas emitted
during organic decomposition. Also a
byproduct of oil refining and burning.
Smells like rotten eggs and, in heavy
concentration, can kill or cause illness.
hydrogeology: The geology of
ground water, with particular emphasis on
the chemistry and movement of water.
hypoxic: A condition of low oxygen
concentration, below that considered
aerobic. in situ: in its original place;
unmoved; unexcavated; remaining in the
subsurface.
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