Common
Enwonmenta
Terms
A Glossary
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Common Environmental
Terms
A Glossary
Compiled by
GLORIA J. STUDDARD
EPA Region IV
Atlanta, Ga.
U.S. Environmental Protection Agency
Washington, D.C.
1973
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The word-, and terms ridi'i <,\: n 'his fjlo^if. ;>v U'-ed in d.sai->srii; and
v-ntine about the en\iiopir."Ht We haw exier^.d !i-,' • tn-M v.;*rds generally
understood and defined :-K,'\vli,:rc Midi as v, \,i; •./ air, but have included
certain common woids v.hi<'v nh;lc not poviiia! to ''v environment, occur
frequently in environment ur rvdentickle. The
glossary ako explains ttn. nc.'inini! of woids such as dnst and abatement as
fiey apply to the environment r\er> thou»h definitions of such words are
found in ordinary dictionary's.
In sum, we have endeavored in a single listing to compile and define the
most common words and terms essential to the study, understanding and
solution of environmental problems. Where so many words and terms are
concerned, it is sometimes difficult to settle upon definitions acceptable to
users who represent a great vaiiety of pursuits and interests. This is particu-
larly true of the newer words generated by science and technology. It may be
recalled that Dr. Samuel Johnson once described a compiler of dictionaries
as a "harmless drudge" and observed: "Dictionaries are like watches; the
worst is better than none, and the best cannot be expected to go quite true."
We do not expect this glossary to be used extensively by technicians and
professionals in environmental control. It was not designed for that purpose.
Rather, it is our hope that it will stimulate and improve a student's under-
standing of man's environment and the interrelationship of the forces and
elements that comprise it.
Acknowledgements
So many good people helped compile this glossary it would be impossible
to list them all, but sincere thanks go to each. Employees of EPA's Region
IV deserve special mention for contributing words for inclusion.
Specific credit should be given to my major sources: Paul Sarnoff's
delightful The New York Times Encyclopedic Dictionary of the Environ-
ment, Herbert Hanson's Dictionary oj Ecology, the American Society of Civil
Engineers' Glossary—Water and Sewage Control Engineering, Veatch and
Humphrys' Water ami Water Use Terminology and a myriad of other equally
good, but untraceable sources.
My especial thanks go to Charles Pou for his patience and moral support,
to Dr. Walter Bishop, my mentor, and to Daisy Sawicki for her beautiful
typing and for uncomplainingly correcting my misspelling of "eutrophication"
all the way through.
G. J. S.
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air curtain
abatement: The method of reducing the
degree or intensity of pollution, also
the use of such a method.
absorption: The penetration of a sub-
stance into or through another. For
example, in air pollution control, ab-
sorption is the dissolving of a soluble
gas, present in an emission, in a liquid
which can be extracted.
accelerator: In radiology, a device for
imparting high velocity to charged
particles such as electrons or protons.
These fast particles can penetrate
matter and are known as radiation.
acclimation: The physiological and be-
havioral adjustments of an organism
to changes in its immediate environ-
ment.
acclimatization: The acclimation or adap-
tation of a particular species over
several generations to a marked
change in the environment.
activated carbon: A highly adsorbent
form of carbon, used to remove odors
and toxic substances from gaseous
emissions. In advanced waste treat-
ment, activated carbon is used to
remove dissolved organic matter
from waste water.
activated sludge: Sludge that has been
aerated and subjected to bacterial
action, used to remove organic matter
from sewage.
activated sludge process: The process of
using biologically active sewage sludge
to hasten breakdown of organic mat-
ter in raw sewage during secondary
waste treatment.
acute toxicity: Any poisonous effect pro-
duced within a short period of time,
usually up to 24-96 hours, resulting
in severe biological harm and often
death.
adaptation: A change in structure or
habit of an organism that produces
better adjustment to the environment.
adsorption: The adhesion of a substance
to the surface of a solid or liquid.
Adsorption is often used to extract
pollutants by causing them to be at-
tached to such adsorbents as activated
carbon or silica gel. Hydrophobic, or
water-repulsing adsorbents, are used
to extract oil from waterways in oil
spills.
adulterants: Chemicals or substances that
by law do not belong in a food, plant,
animal or pesticide formulation. Adul-
terated products are subject to seizure
by the Food and Drug Administration.
advanced waste treatment: Waste water
treatment beyond the secondary or
biological stage that includes removal
of nutrients such as phosphorus and
nitrogen and a high percentage of sus-
pended solids. Advanced waste treat-
ment, known as tertiary treatment, is
the "polishing stage" of waste water
treatment and produces a high quality
effluent.
aeration: The process of being supplied
or impregnated with air. Aeration is
used in waste water treatment to
foster biological and chemical puri-
fication.
aerobic: This refers to life or processes
that can occur only in the presence
of oxygen.
aerosol: A suspension of liquid or solid
particles in the air.
afterburner: An air pollution abatement
device that removes undesirable or-
ganic gases through incineration.
agricultural pollution: The liquid and
solid wastes from all types of farm-
ing, including runoff from pesticides,
fertilizers and feedlots; erosion and
dust from plowing, animal manure
and carcasses and crop residues and
debris. It has been estimated that
agricultural pollution in the U.S. has
amounted to more than 2Vz billion
tons per year.
air curtain: A method for mechanical
containment of oil spills. Air is
bubbled through a perforated pipe
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air mass
causing an upward water flow that
retards the spreading of oil. Air cur-
tains are also used as barriers to pre-
vent fish from entering a polluted
body of water.
air mass: A widespread body of air with
properties that were established while
the air was situated over a particular
region of the earth's surface and that
undergoes specific modifications while
in transit away from that region.
air monitoring: See monitoring.
air pollution: The presence of contami-
nants in the air in concentrations that
prevent the normal dispersive ability
of the air and that interfere directly
or indirectly with man's health, safety
or comfort or with the full use and
enjoyment of his property.
air pollution episode: The occurrence of
abnormally high concentrations of air
pollutants usually due to low winds
and temperature inversion and accom-
panied by an increase in illness and
death. See inversion.
air quality control region: An area desig-
nated by the Federal government
where two or more communities—
either in the same or different states
—share a common air pollution prob-
lem.
air quality criteria: The levels of pollu-
tion and lengths of exposure at which
adverse effects on health and welfare
occur.
air quality standards: The prescribed
level of pollutants in the outside air
that cannot be exceeded legally dur-
ing a specified time in a specified
geographical area.
algal bloom: A proliferation of living
algae on the surface of lakes, streams
or ponds. Algal blooms are stimulated
by phosphate enrichment.
alpha particle: A positively charged par-
ticle emitted by certain radioactive
materials. It is the least penetrating
of the three common types of radi-
ation (alpha, beta and gamma) and
usually not dangerous to plants, ani-
mals or man.
ambient air: Any unconfined portion of
the atmosphere; the outside air.
anadromous: Type of fish that ascend
rivers from the sea to spawn.
anaerobic: Refers to life or processes
that occur in the absence of oxygen.
anticoagulant: A chemical that interferes
with blood clotting, often used as a
rodenticide.
anti-degradation clause: A provision in
air quality and water quality laws
that prohibits deterioration of air or
water quality in areas where the pol-
lution levels are presently below
those allowed.
aquifer: An underground bed or stratum
of earth, gravel or porous stone that
contains water.
aquatic plants: Plants that grow in water
either floating on the surface, growing
up from the bottom of the body of
water or growing under the surface
of the water.
area source: In air pollution, any small
individual fuel combustion source, in-
cluding any transportation sources.
This is a general definition; area
source is legally and precisely defined
in Federal regulations. See point
source.
asbestos: A mineral fiber with countless
industrial uses; a hazardous air pollu-
tant when inhaled.
A-Scale sound level: The measurement of
sound approximating the auditory
sensitivity of the human ear. The
A-Scale sound level is used to meas-
ure the relative noisiness or annoy-
ance of common sounds.
assimilation: Conversion or incorpora-
tion of absorbed nutrients into proto-
plasm. Also refers to the ability of a
body of water to purify itself of or-
ganic pollution.
atmosphere: The layer of air surrounding
the earth.
atomic pile: A nuclear reactor.
attractant: A chemical or agent that lures
insects or other pests by olfactory
stimulation.
attrition: Wearing or grinding down by
friction. One of the three basic con-
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biological control
tributing processes of air pollution,
the others are vaporization and com-
bustion.
audiometer: An instrument for measur-
ing hearing sensitivity.
autotrophic: Self-nourishing; denoting
those organisms capable of construct-
ing organic matter from inorganic
substances.
backfill: The material used to refill a
ditch or other excavation, or the
process of doing so.
background level: With respect to air
pollution, amounts of pollutants pres-
ent in the ambient air due to natural
sources.
background radiation: Normal radiation
present in the lower atmosphere from
cosmic rays and from earth sources.
bacteria: Single-celled microorganisms
that lack chlorophyll. Some bacteria
are capable of causing human, animal
or plant diseases, others are essential
in pollution control because they
break down organic matter in the air
and in the water.
baffle: Any deflector device used to
change the direction of flow or the
velocity of water, sewage or products
of combustion such as fly ash or
coarse paniculate matter. Also used
in deadening sound.
baghouse: An air pollution abatement
device used to trap particulates by
filtering gas streams through large
fabric bags, usually made of glass
fibers.
baling: A means of reducing the volume
of solid waste by compaction.
ballistic separator: A machine that sep-
arates inorganic from organic matter
in a composting process.
band application: With respect to pesti-
cides, the application of the chemical
over or next to each row of plants
in a field.
bar screen: In waste water treatment, a
screen that removes large floating and
suspended solids.
basal application: With respect to pesti-
cides, the application of the pesticide
formulation on stems or trunks of
plants just above the soil line.
basin: See river basin.
benthic region: The bottom of a body
of water. This region supports the
benthos, a type of life that not only
lives upon, but contributes to the
character of the bottom.
benthos: The plant and animal life whose
habitat is the bottom of a sea, lake
or river.
beryllium: A metal that when airborne
has adverse effects on human health;
it has been declared a hazardous air
pollutant. It is primarily discharged
by operations such as machine shops,
ceramic and propellant plants and
foundries.
beta particle: An elementary particle
emitted by radioactive decay that may
cause skin burns. It is easily stopped
by a thin sheet of metal.
bioassay: The employment of living or-
ganisms to determine the biological
effect of some substance, factor or
condition.
biochemical oxygen demand (BOD): A
measure of the amount of oxygen
consumed in the biological processes
that break down organic matter in
water. Large amounts of organic
waste use up large amounts of dis-
solved oxygen, thus the greater the
degree of pollution, the greater the
BOD.
biodegradable: The process of decompos-
ing quickly as a result of the action
of microorganisms.
biological control: A method of con-
trolling pests by means 'of introduced
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biological oxidation
or naturally occurring predatory orga-
nisms, sterilization or the use of in-
hibiting hormones, etc., rather than
by mechanical or chemical means.
biological oxidation: The process by
which bacterial and other microorga-
nisms feed on complex organic mate-
rials and decompose them. Self-
purification of waterways and acti-
vated sludge and trickling filter waste
water treatment processes depend on
this principle. The process is also
called biochemical oxidation.
biomonitoring: The use of living orga-
nisms to test the suitability of effluent
for discharge into receiving waters
and to test the quality of such waters
downstream from a discharge.
biospbere: The portion of the earth and
its atmosphere capable of supporting
life.
biostabiiizer: A machine used to convert
solid waste into compost by grinding
and aeration.
biota: All the species of plants and ani-
mals occurring within a certain area.
bloom: A proliferation of living algae
and/or other aquatic plants on the
surface of lakes or ponds. Blooms
are frequently stimulated by phos-
phate enrichment.
BOD: See biochemical oxygen demand.
BOD5: The amount of dissolved oxygen
consumed in five days by biological
processes breaking down organic mat-
ter in an effluent. See biochemical
oxygen demand.
bog: Wet, spongy land usually poorly
drained, highly acid and rich in plant
residue.
boom: A floating device that is used to
contain oil on a body of water.
botanical pesticide: A plant-produced
chemical used to control pests; for ex-
ample, nicotine, strychnine or orpyre-
thrun.
brackish water: A mixture of fresh and
salt water.
breeder: A nuclear reactor that produces
more fuel than it consumes.
broadcast application: With respect to
pesticides, the application of a chem-
ical over an entire field, lawn or
other area.
burial ground (graveyard): A place for
burying unwanted radioactive mate-
rials to prevent radiation escape, the
earth or water acting as a shield.
Such materials must be placed in
water-tight, noncorrodible containers
so the radioactive material cannot
leach out and invade underground
water supplies.
cadmium: See heavy metals.
carbon dioxide (CO2): A colorless, odor-
less, nonpoisonous gas that is a nor-
mal part of the ambient air. CO2 is a
product of fossil fuel combustion, and
some researchers have theorized that
excess CO2 raises atmospheric tem-
peratures.
carbon monoxide (CO): A colorless,
odorless, highly toxic gas that is a
normal byproduct of incomplete fossil
fuel combustion. CO, one of the
major air pollutants, can be harmful
in small amounts if breathed over a
certain period of time.
carcinogenic: Cancer producing.
catalytic converter: An air pollution
abatement device that removes organ-
ic contaminants by oxidizing them
into carbon dioxide and water through
chemical reaction. Can be used to
reduce nitrogen oxide emissions from
motor vehicles.
caustic soda: Sodium hydroxide (NaOH),
a strongly alkaline, caustic substance
used as the cleaning agent in some
detergents.
cells: With respect to solid waste dis-
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coliform organism
posal, earthen compartments in which
solid wastes are dumped, compacted
and covered over daily with layers
of earth.
centrifugal collector: Any of several
mechanical systems using centrifugal
force to remove aerosols from a gas
stream.
cfs: Cubic feet per second, a measure of
the amount of water passing a given
point.
channelization: The straightening and
deepening of streams to permit water
to move faster, to reduce flooding or
to drain marshy acreage for farming.
However, channelization reduces the
organic waste assimilation capacity of
the stream and may disturb fish
breeding and destroy the stream's
natural beauty.
chemical oxygen demand (COD): A
measure of the amount of oxygen
required to oxidize organic and oxi-
dizable inorganic compounds in
water. The COD test, like the BOD
test, is used to determine the degree
of pollution in an effluent.
chemosterilant: A pesticide chemical
that controls pests by destroying
their ability to reproduce.
chilling effect: The lowering of the earth's
temperature due to the increase of
atmospheric particulates that inhibit
penetration of the sun's energy.
chlorinated hydrocarbons: A class of
generally long-lasting, broad-spectrum
insecticides of which the best known
is DDT, first used for insect control
during World War II. Other similar
compounds include aldrin, dieldrin,
heptachlor, chlordane, lindane, endrin,
mirex, benzene hexachloride (BHC),
and toxaphene. The qualities of per-
sistence and effectiveness against a
wide variety of insect pests were long
regarded as highly desirable in agri-
culture, public health and home uses.
But later research has revealed that
these same qualities may represent a
potential hazard through accumulation
in the food chain and persistence in
the environment.
chlorination: The application of chlorine
to drinking water, sewage or indus-
trial waste for disinfection or oxida-
tion of undesirable compounds.
chlorinator: A device for adding a
chlorine-containing gas or liquid to
drinking or waste water.
chlorine-contact chamber: In a waste
treatment plant, a chamber in which
effluent is disinfected by chlorine be-
fore it is discharged to the receiving
waters.
chlorosis: Yellowing or whitening of nor-
mally green plant parts. It can be
caused by disease organisms, lack of
oxygen or nutrients in the soil or by
various air pollutants.
chromium: See heavy metals.
chronic: Marked by long duration or
frequent recurrence, as a disease.
clarification: In waste water treatment,
the removal of turbidity and sus-
pended solids by settling, often aided
by centrifugal action and chemically
induced coagulation.
clariner: In waste water treatment, a
settling tank which mechanically re-
moves settleable solids from wastes.
coagulation: The clumping of particles in
order to settle out impurities; often
induced by chemicals such as lime or
alum.
coastal zone: Coastal waters and adja-
cent lands that exert a measurable
influence on the uses of the sea and
its ecology.
COD: See chemical oxygen demand.
coefficient of haze (COH): A measure-
ment of visibility interference in the
atmosphere.
coffin: A thick-walled container (usually
lead) used for transporting radioactive
materials.
COH: See coefficient of haze.
coliform index: An index of the purity
of water based on a count of its coli-
form bacteria.
coliform organism: Any of a number of
organisms common to the intestinal
tract of man and animals whose
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combined sewers
presence in waste water is an indi-
cator of pollution and of potentially
dangerous bacterial contamination.
combined sewers: A sewerage system
that carries both sanitary sewage and
storm water runoff. During dry
weather, combined sewers carry all
waste water to the treatment plant.
During a storm, only part of the flow
is intercepted because of plant over-
loading; the remainder goes untreated
to the receiving stream.
combustion: Burning. Technically, a rapid
oxidation accompanied by the release
of energy in the form of heat and
light. It is one of the three basic con-
tributing factors causing air pollution,
the others are attrition and vaporiza-
tion.
comminution: Mechanical shredding or
pulverizing of waste, a process that
converts it into a homogeneous and
more manageable material. Used in
solid waste management and in the
primary stage of waste water treat-
ment.
comminutor: A device that grinds solids
to make them easier to treat.
compaction: Reducing the bulk of solid
waste by rolling and tamping.
compost: Relatively stable decomposed
organic material.
composting: A controlled process of de-
grading organic matter by microorga-
nisms. (1) mechanical—a method in
which the compost is continuously
and mechanically mixed and aerated.
(2) ventilated cell—compost is mixed
and aerated by being dropped through
a vertical series of ventilated cells.
(3) windrow—an open-air method in
which compostable material is placed
in windrows, piles or ventilated bins
or pits and occasionally turned or
mixed. The process may be anaerobic
or aerobic.
contact pesticide: A chemical that kills
pests on contact with the body, rather
than by ingestion (stomach poison).
contrails: Long narrow clouds caused by
the disturbance of the atmosphere
during passage of high-flying jets.
Proliferation of contrails may cause
changes in the weather.
coolant: A substance, usually liquid or
gas, used for cooling any part of a
reactor in which heat is generated,
including the core, the reflector, shield
and other elements that may be
heated by absorption of radiation.
cooling tower: A device to remove excess
heat from water used in industrial
operations, notably in electric power
generation.
core: The heart of a nuclear reactor
where energy is released.
cover material: Soil that is used to cover
compacted solid waste in a sanitary
landfill.
cultural eutrophication: Acceleration by
man of the natural aging process of
bodies of water.
curie: A measure of radioactivity.
cutie-pie: A portable instrument equipped
with a direct reading meter used to
determine the level of radiation in
an area.
cyclone collector: A device used to col-
lect large-size particulates from pol-
luted air by centrifugal force.
DDT: The first of the modern chlori-
nated hydrocarbon insecticides whose
chemical name is l,l,l-tricholoro-2,2-
bis (p-chioriphenyl)-ethane. It has a
half-life of 15 years, and its residues
can become concentrated in the fatty
tissues of certain organisms, especially
fish. Because of its persistence in the
environment and its ability to accu-
mulate and magnify in the food
chain, EPA has banned the registra-
tion and interstate sale of DDT for
nearly all uses in the United States
effective December 31, 1972.
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dry limestone process
decibel (dB): A unit of sound measure-
ment.
decomposition: Reduction of the net
energy level and change in chemical
composition of organic matter be-
cause of the actions of aerobic or
anaerobic microorganisms.
dermal toxiciry: The ability of a pesti-
cide chemical to poison an animal or
human by skin absorption.
desalinization: Salt removal from sea or
brackish water.
desiccant: A chemical agent that may be
used to remove moisture from plants
or insects causing them to wither and
die.
detergent: Synthetic washing agent that,
like soap, lowers the surface tension
of water, emulsifies oils and holds
dirt in suspension. Environmentalists
have criticized detergents because
most contain large amounts of phos-
phorus-containing compounds that
contribute to the eutrophication of
waterways.
diatomaceous earth (diatomite): A fine
siliceous material resembling chalk
used in waste water treatment plants
to filter sewage effluent to remove
solids. May also be used as inactive
ingredients in pesticide formulations
applied as dust or powder.
diffused air: A type of sewage aeration.
Air is pumped into the sewage through
a perforated pipe.
digester: In a waste water treatment
plant, a closed tank that decreases
the volume of solids and stabilizes
raw sludge by bacterial action.
digestion: The biochemical decomposition
of organic matter. Digestion of sew-
age sludge takes place in tanks where
the sludge decomposes, resulting in
partial gasification, liquefaction and
mineralization of pollutants.
dilution ratio: The ratio of the volume
of water of a stream to the volume
of incoming waste. The capacity of a
stream to assimilate waste is partial-
ly dependent upon the dilution ratio.
disinfection: Effective killing by chemical
or physical processes of all organisms
capable of causing infectious disease.
Chlorination is the disinfection meth-
od commonly employed in sewage
treatment processes.
dispersant: A chemical agent used to
break up concentrations of organic
material. In cleaning oil spills, dis-
persants are used to disperse oil from
the water surface.
dissolved oxygen (DO): The oxygen dis-
solved in water or sewage. Adequate-
ly dissolved oxygen is necessary for
the life of fish and other aquatic
organisms and for the prevention of
offensive odors. Low dissolved oxy-
gen concentrations generally are due
to discharge of excessive organic
solids having high BOD, the result of
inadequate waste treatment.
dissolved solids: The total amount of
dissolved material, organic and inor-
ganic, contained in water or wastes.
Excessive dissolved solids make water
unpalatable for drinking and unsuit-
able for industrial uses.
distillation: The removal of impurities
from liquids by boiling. The steam,
condensed back into liquid, is almost
pure water; the pollutants remain in
the concentrated residue.
dose: In radiology, the quantity of en-
ergy or radiation absorbed.
dosimeter (dosemeter): An instrument
used to measure the amount of radi-
ation a person has received.
dredging: A method for deepening
streams, swamps or coastal waters by
scraping and removing solids from the
bottom. The resulting mud is usually
deposited in marshes in a process
called filling. Dredging and filling can
disturb natural ecological cycles. For
example, dredging can destroy oyster
beds and other aquatic life: filling can
destroy the feeding and breeding
grounds for many fish species.
dry limestone process: A method of con-
trolling air pollution caused by sulfur
oxides. The polluted gases are exposed
to limestone which combines with
oxides of sulfur to form manageable
residues.
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dump
dump: A land site where solid waste is
disposed of in a manner that does
not protect the environment.
dust: Fine-grain paniculate matter that
is capable of being suspended in air.
dustfall jar: An open-mouthed container
used to collect large particles that fall
out of the air. The particles are mea-
sured and analyzed.
dystrophic lakes: Lakes between eutro-
phic and swamp stages of aging. Such
lakes are shallow and have high hu-
mus content, high organic matter con-
tent, low nutrient availability and
high BOD.
ecological impact: The total effect of an
environmental change, either natural
or man-made, on the ecology of the
area.
ecology: The interrelationships of living
things to one another and to their en-
vironment or the study of such inter-
relationships.
economic poisons: Those chemicals used
to control insects, rodents, plant dis-
eases, weeds and other pests, and also
to defoliate economic crops such as
cotton.
ecosphere: See biosphere.
ecosystem: The interacting system of a
biological community and its non-
living environment.
effluent: A discharge of pollutants into
the environment, partially or com-
pletely treated or in its natural state.
Generally used in regard to discharges
into waters.
electrodialysis: A process that uses
electrical current and an arrangement
of permeable membranes to separate
soluble minerals from water. Often
used to desalinize salt or brackish
water.
electrostatic precipitator: An air pollution
control device that removes participate
matter by imparting an electrical
charge to particles in a gas stream for
mechanical collection on an electrode.
emergency episode: See air pollution
episode.
emission: See effluent. (Generally used
in regard to discharges into air.)
emission factor: The average amount of
a pollutant emitted from each type of
polluting source in relation to a
specific amount of material processed.
For example, an emission factor for
a blast furnace (used to make iron)
would be a number of pounds of par-
ticulates per ton of raw materials.
emission inventory: A list of air pollu-
tants emitted into a community's at-
mosphere, in amounts (usually tons)
per day, by type of source. The emis-
sion inventory is basic to the establish-
ment of emission standards.
emission standard: The maximum amount
of a pollutant legally permitted to be
discharged from a single source, either
mobile or stationary.
enrichment: The addition of nitrogen,
phosphorus and carbon compounds or
other nutrients into a lake or other
waterway that greatly increases the
growth potential for algae and other
aquatic plants. Most frequently, en-
richment results from the inflow of
sewage effluent or from agricultural
runoff.
environment: The sum of all external
conditions and influences affecting the
life, development and, ultimately, the
survival of an organism.
environmental impact statement: A docu-
ment prepared by a Federal agency
on the environmental impact of its
proposals for legislation and other
major actions significantly affecting
the quality of the human environment.
Environmental impact statements are
used as tools for decision making and
are required by the National Environ-
mental Policy Act.
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flue gas
epidemiology: The study of diseases as
they affect populations.
erosion: The wearing away of the land
surface by wind or water. Erosion
occurs naturally from weather or run-
off but is often intensified by man's
land-clearing practices.
estuaries: Areas where the fresh water
meets salt water. For example, bays,
mouths of rivers, salt marshes and
lagoons. Estuaries are delicate eco-
systems; they serve as nurseries,
spawning and feeding grounds for a
large group of marine life and provide
shelter and food for birds and wildlife.
eutrophication: The normally slow aging
process by which a lake evolves into
a bog or marsh and ultimately as-
sumes a completely terrestrial state
and disappears. During eutrophication
the lake becomes so rich in nutritive
compounds, especially nitrogen and
phosphorus, that algae and other
microscopic plant life become super-
abundant, thereby "choking" the lake,
and causing it eventually to dry up.
Eutrophication may be accelerated by
many human activities.
eutrophic lakes: Shallow lakes, weed-
choked at the edges and very rich in
nutrients. The water is characterized
by large amounts of algae, low water
transparency, low dissolved oxygen
and high BOD.
evaporation ponds: Shallow, artificial
ponds where sewage sludge is pumped,
permitted to dry and either removed
or buried by more sludge.
fabric filters: A device for removing dust
and particulate matter from industrial
emissions much like a home vacuum
cleaner bag. The most common use
of fabric filters is the baghouse.
fecal coliform bacteria: A group of orga-
nisms common to the intestinal tracts
of man and of animals. The presence
of fecal coliform bacteria in water is
an indicator of pollution and of po-
tentially dangerous bacterial contami-
nation.
feedlot: A relatively small, confined land
area for raising cattle. Although an
economical method of fattening beef,
feedlots concentrate a large amount
of animal wastes in a small area. This
excrement cannot be handled by the
soil as it could be if the cattle were
scattered on open range. In addition,
runoff from feedlots contributes ex-
cessive quantities of nitrogen, phos-
phorus and potassium to nearby
waterways, thus contributing to eutro-
phication.
fen: A low-lying land area partly covered
by water.
filling: The process of depositing dirt and
mud in marshy areas to create more
land for real estate development. Fill-
ing can disturb natural ecological
cycles. See dredging.
film badge: A piece of masked photo-
graphic film worn like a badge by
nuclear workers to monitor an expo-
sure to radiation. Nuclear radiation
darkens the film.
filtration: In waste water treatment, the
mechanical process that removes par-
ticulate matter by separating water
from solid material usually by passing
it through sand.
floe: A clump of solids formed in sewage
by biological or chemical action.
flocculation: In waste water treatment,
the process of separating suspended
solids by chemical creation of clumps
or floes.
flowmeter: In waste water treatment, a
meter that indicates the rate at which
waste water flows through the plant.
flue gas: A mixture of gases resulting
from combustion and emerging from
a chimney. Flue gas includes nitrogen
-------
fluorides
oxides, carbon oxides, water vapor
and often sulfur oxides or particu-
lates.
fluorides: Gaseous, solid or dissolved
compounds containing fluorine,
emitted into the air or water from a
number of industrial processes. Fluo-
rides in the air are a cause of vege-
tation damage and, indirectly, of
livestock damage.
flume: A channel, either natural or man-
made, which carries water.
fly ash: All solids, including ash, charred
paper, cinders, dust, soot or other
partially incinerated matter, that are
carried in a gas stream.
fog: Liquid particles formed by conden-
sation of vaporized liquids.
fogging: The application of a pesticide
by rapidly heating the liquid chemi-
cal, thus forming very fine droplets
with the appearance of smoke. Fog-
ging is often used to destroy mos-
quitoes and blackflies.
food waste: Animal and vegetable waste
resulting from the handling, storage,
sale, preparation, cooking and serving
of foods; commonly called garbage.
fossil fuels: Coal, oil and natural gas;
so-called because they are derived
from the remains of ancient plant
and animal life.
fume: Tiny solid particles commonly
formed by the condensation of vapors
of solid matter.
fumigant: A pesticide that is burned or
evaporated to form a gas or vapor
that destroys pests. Fumigants are
often used in buildings or green-
houses.
fungi: Small, often microscopic plants
without chlorophyll. Some fungi in-
fect and cause disease in plants or
animals; other fungi are useful in
stabilizing sewage or in breaking
down wastes for compost.
fungicide: A pesticide chemical that kills
fungi or prevents them from causing
diseases, usually on plants of econom-
ic importance. See pesticide.
game fish: Those species of fish sought
by sports fishermen; for example,
salmon, trout, black bass, striped bass,
etc. Game fish are usually more sen-
sitive to environmental changes and
water quality degradation than
"rough" fish.
gamma ray: Waves of radiant nuclear
energy. Gamma rays are the most
penetrating of the three types of radi-
ation and are best stopped by dense
materials such as lead.
garbage: See food waste.
garbage grinding: A method of grinding
food waste by a household disposal,
for example, and washing it into the
sewer system. Ground garbage then
must be disposed of as sewage sludge.
Geiger counter: An electrical device that
detects the presence of radioactivity.
generator: A device that converts me-
chanical energy into electrical energy.
germicide: A chemical or agent that kills
microorganisms such as bacteria and
prevents them from causing disease.
Such compounds must be registered
as pesticides with EPA.
grain: A unit of weight equivalent to 65
milligrams or 2/1,000 of an ounce.
grain loading: The rate of emission of
particulate matter from a polluting
source. Measurement is made in
grains of particulate matter per cubic
foot of gas emitted.
green belts: Certain areas restricted from
being used for buildings and houses;
they often serve as separating buffers
between pollution sources and con-
centrations of population.
greenhouse effect: The heating effect of
the atmosphere upon the earth. Light
waves from the sun pass through the
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humus
air and are absorbed by the earth.
The earth then reradiates this energy
as heat waves that are absorbed by
the air, specifically by carbon dioxide.
The air thus behaves like glass in a
greenhouse, allowing the passage of
light but not of heat. Thus many
scientists theorize that an increase in
the atmospheric concentration of CO2
can eventually cause an increase in
the earth's surface temperature.
ground cover: Grasses or other plants
grown to keep soil from being blown
or washed away.
groundwater: The supply of freshwater
under the earth's surface in an aqui-
fer or soil that forms the natural
reservoir for man's use.
groundwater runoff: Groundwater that is
discharged into a stream channel as
spring or seepage water.
habitat: The sum total of environmental
conditions of a specific place that is
occupied by an organism, a popula-
tion or a community.
half-life: The time it takes certain mate-
rials, such as persistent pesticides or
radioactive isotopes, to lose half their
strength. For example, the half-life
of DDT is 15 years; the half-life of
radium is 1,580 years.
hammermill: A broad category of high-
speed equipment that uses pivoted or
fixed hammers or cutters to crush,
grind, chip or shred solid wastes.
hard water: Water containing dissolved
minerals such as calcium, iron and
magnesium. The most notable char-
acteristic of hard water is its inability
to lather soap. Some pesticide chem-
icals will curdle or settle out when
added to hard water.
hazardous air pollutant: According to
law, a pollutant to which no ambient
air quality standard is applicable and
that may cause or contribute to an
increase in mortality or in serious
illness. For example, asbestos, beryl-
lium and mercury have been declared
hazardous air pollutants.
heat island effect. An air circulation
problem peculiar to cities. Tall build-
ings, heat from pavements and con-
centrations of pollutants create a haze
dome that prevents rising hot air
from being cooled at its normal rate.
A self-contained circulation system is
put in motion that can be broken by
relatively strong winds. If such winds
are absent, the heat island can trap
high concentrations of pollutants and
present a serious health problem.
heating season: The coldest months of
the year when pollution emissions are
higher in some areas because of in-
creased fossil-fuel consumption.
heavy metals: Metallic elements with
high molecular weights, generally
toxic in low concentrations to plant
and animal life. Such metals are often
residual in the environment and ex-
hibit biological accumulation. Ex-
amples include mercury, chromium,
cadmium, arsenic and lead.
herbicide: A pesticide chemical used to
destroy or control the growth of
weeds, bush and other undesirable
plants. See pesticide.
herbivore: An organism that feeds on
vegetation.
heterotrophic organism: Organisms de-
pendent on organic matter for food.
high density polyethylene: A material
often used in the manufacture of plas-
tic bottles that produces toxic fumes
if incinerated.
hi-volume sampler: A device used in the
measurement and analysis of sus-
pended particulate pollution. Also
called a Hi-Vol.
hot: A colloquial term meaning highly
radioactive.
humus: Decomposed organic material.
11
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hydrocarbons
hydrocarbons: A vast family of com-
pounds containing carbon and hydro-
gen in various combinations, found
especially in fossil fuels. Some hydro-
carbons are major air pollutants,
some may be carcinogenic and others
contribute to photochemical smog.
hydrogen sulflde (FLS): A malodorous
gas made up of hydrogen and sulfur
with the characteristic odor of rotten
eggs. It is emitted in the natural de-
composition of organic matter and is
also the natural accompaniment of
advanced stages of eutrophication.
H2S is also a byproduct of refinery
activity and the combustion of oil
during power plant operations. In
heavy concentrations, it can cause
illness.
hydrology: The science dealing with the
properties, distribution and circulation
of water and snow.
impedance: The rate at which a sub-
stance can absorb and transmit sound.
implementation plan: A document of the
steps to be taken to ensure attainment
of environmental quality standards
within a specified time period. Imple-
mentation plans are required by vari-
ous laws.
impoundment: A body of water, such as
a pond, confined by a dam, dike,
floodgate or other barrier.
incineration: The controlled process by
which solid, liquid or gaseous com-
bustible wastes are burned and
changed into gases; the residue pro-
duced contains little or no combus-
tible material.
incinerator: An engineered apparatus
used to burn waste substances and in
which all the combustion factors—
temperature, retention time, turbu-
lence and combustion air—can be
controlled.
inert gas: A gas that does not react with
other substances under ordinary con-
ditions.
inertia) separator: An air pollution con-
trol device that uses the principle of
inertia to remove particulate matter
from a stream of air or gas.
infiltration: The flow of a fluid into a
substance through pores or small
openings. Commonly used in hydrol-
ogy to denote the flow of water into
soil material.
inoculum: Material such as bacteria
placed in compost or other medium
to initiate biological action.
integrated pest control: A system of man-
aging pests by using biological, cul-
tural and chemical means.
interceptor sewers: Sewers used to collect
the flows from main and trunk sewers
and carry them to a central point for
treatment and discharge. In a com-
bined sewer system, where street run-
off from rains is allowed to enter the
system along with sewage, interceptor
sewers allow some of the sewage to
flow untreated directly into the receiv-
ing stream, to prevent the plant from
being overloaded.
interstate carrier water supply: A water
supply whose water may be used for
drinking or cooking purposes aboard
common carriers (planes, trains, buses
and ships) operating interstate. Inter-
state carrier water supplies are regu-
lated by the Federal government.
interstate waters: According to law,
waters defined as: (1) rivers, lakes and
other waters that flow across or
form a part of State or international
boundaries; (2) waters of the Great
Lakes; (3) coastal waters — whose
scope has been defined to include
ocean waters seaward to the territorial
limits and waters along the coast-
line (including inland streams) in-
fluenced by the tide.
inversion: An atmospheric condition
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methane
where a layer of cool air is trapped
by a layer of warm air so that it
cannot rise. Inversions spread pol-
luted air horizontally rather than ver-
tically so that contaminating sub-
stances cannot be widely dispersed.
An inversion of several days can
cause an air pollution episode.
ionization chamber: A device roughly
similar to a Geiger counter that re-
veals the presence of ionizing radia-
tion.
isotope: A variation of an element having
the same atomic number as the ele-
ment itself, but having a different
atomic weight bcause of a different
number of neutrons. Different iso-
topes of the same element have dif-
ferent radioactive behavior.
lagoon: In waste water treatment, a shal-
low pond usually man-made where
sunlight, bacterial action and oxygen
interact to restore waste water to a
reasonable state of purity.
lateral sewers: Pipes running underneath
city streets that collect sewage from
homes or businesses.
LC50: Median lethal concentration, a
standard measure of toxicity. LC50
indicates the concentration of a sub-
stance that will kill 50 percent of a
group of experimental insects or ani-
mals.
leachate: Liquid that has percolated
through solid waste or other mediums
and has extracted dissolved or sus-
pended materials from it.
leaching: The process by which soluble
materials in the soil, such as nutrients,
pesticide chemicals or contaminants,
are washed into a lower layer of soil
or are dissolved and carried away by
water.
lead: A heavy metal that may be haz-
ardous to human health if breathed
or ingested.
life cycle: The phases, changes or stages
an organism passes through during
its lifetime.
lift: In a sanitary landfill, a compacted
layer of solid waste and the top layer
of cover material.
limnology: The study of the physical,
chemical, meteorological and biologi-
cal aspects of fresh waters.
marsh: A low-lying tract of soft, wet
land that provides an important eco-
system for a variety of plant and
animal life but often is destroyed by
dredging and filling.
masking: Covering over of one sound or
element by another. Quantitatively,
masking is the amount the audibility
threshold of one sound is raised by
the presence of a second masking
sound. Also used in regard to odors.
mechanical turbulence: The erratic move-
ment of air caused by local obstruc-
tions such as buildings.
mercury: A heavy metal, highly toxic if
breathed or ingested. Mercury is re-
sidual in the environment, showing
biological accumulation in all aquatic
organisms, especially fish and shell
fish. Chronic exposure to airborne
mercury can have serious effects on
the central nervous system.
methane: Colorless, nonpoisonous and
flammable gaseous hydrocarbon. Meth-
ane, (CA.i), is emitted by marshes and
by dumps undergoing anaerobic de-
composition.
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mgd
mgd: Millions of gallons per day. Mgd
is commonly used to express rate of
flow.
microbes: Minute plant or animal life.
Some disease-causing microbes exist
in sewage.
mist: Liquid particles in air formed by
condensation of vaporized liquids.
Mist particles vary from 500 to 40
microns in size. By comparison, fog
particles are smaller than 40 microns
in size.
mixed liquor: A mixture of activated
sludge and water containing organic
matter undergoing activated sludge
treatment in the aeration tank.
mobile source: A moving source of air
pollution such as an automobile.
monitoring: Periodic or continuous deter-
mination of the amount of pollutants
or radioactive contamination present
in the environment.
muck soils: Soils made from decaying
plant materials.
mulch: A layer of wood chips, dry
leaves, straw, hay, plastic strips or
other material placed on the soil
around plants to retain moisture, to
prevent weeds from growing and to
enrich soil.
K
in a discolored, sunken area or death
of the entire plant.
nitric oxide (NO): A gas formed in great
part from atmospheric nitrogen and
oxygen when combustion takes place
under h igh temperature and high pres-
sure, as in internal combustion en-
gines. NO is not itself a pollutant;
however, in the ambient air, it con-
verts to nitrogen dioxide, a major
contributor to photochemical smog.
nitrogen dioxide (NO2): A compound
produced by the oxidation of nitric
oxide in the atmosphere; a major
contributor to photochemical smog.
nitrogenous wastes: Wastes of animal or
plant origin that contain a significant
concentration of nitrogen.
NO: A notation meaning oxides of nitro-
gen. See nitric oxide.
noise: Any undesired audible signal.
Thus, in acoustics, noise is any un-
desired sound.
NTA: Nitrilotriacetic acid, a compound
once used to replace phosphates in
detergents.
nuclear power plant: Any device, ma-
chine or assembly that converts nu-
clear energy into some form of useful
power, such as mechanical or elec-
trical power. In a nuclear electric
power plant, heat produced by a
reactor is generally used to make
steam to drive a turbine that in turn
drives an electric generator.
nutrients: Elements or compounds essen-
tial as raw materials for organism
growth and development; for example,
carbon, oxygen, nitrogen and phos-
phorus.
natural gas: A fuel gas occurring nat-
urally in certain geologic formation.
Natural gas is usually a combustible
mixture of methane and hydro-
carbons.
natural selection: The natural process by
which the organisms best adapted to
their environment survive and those
less well adapted are eliminated.
necrosis: Death of plant cells resulting
oil spill: The accidental discharge of oil
into oceans, bays or inland water-
14
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PCB's
ways. Methods of oil spill control
include chemical dispersion, combus-
tion, mechanical containment and
absorption.
oligotrophic lakes: Deep lakes that have
a low supply of nutrients and thus
contain little organic matter. Such
lakes are characterized by high water
transparency and high dissolved
oxygen.
opacity: Degree of obscuration of light.
For example, a window has zero
opacity; a wall is 100 percent opaque.
The Ringelmann system of evaluating
smoke density is based on opacity.
open burning: Uncontrolled burning of
wastes in an open dump.
open dump: See dump.
organic: Referring to or derived from
living organisms. In chemistry, any
compound containing carbon.
organism: Any living human, plant or
animal.
organophosphates: A group of pesticide
chemicals containing phosphorus, such
as malathion and parathion, intended
to control insects. These compounds
are short-lived and, therefore, do not
normally contaminate the environ-
ment. However, some organophos-
phates, such as parathion, are ex-
tremely toxic when initially applied
and exposure to them can interfere
with the normal processes of the ner-
vous system, causing convulsions and
eventually death. Malathion, on the
other hand, is low in toxicity and
relatively safe for humans and ani-
mals; it is a common ingredient in
household insecticide products.
outfall: The mouth of a sewer, drain or
conduit where an effluent is dis-
charged into the receiving waters.
overfire air: Air forced into the top of
an incinerator to fan the flame.
oxidant: Any oxygen containing substance
that reacts chemically in the air to
produce new substances. Oxidants are
the primary contributors to photo-
chemical smog.
oxidation: A chemical reaction in which
oxygen unites or combines with other
elements. Organic matter is oxidized
by the action of aerobic bacteria; thus
oxidation is used in waste water treat-
ment to break down organic wastes.
oxidation pond: A man-made lake or
pond in which organic wastes are
reduced by bacterial action. Often
oxygen is bubbled through the pond
to speed the process.
ozone (O3): A pungent, colorless, toxic
gas. Ozone is one component of
photochemical smog and is consid-
ered a major air pollutant.
package plant: A prefabricated or pre-
built waste water treatment plant.
packed tower: An air pollution control
device in which polluted air is forced
upward through a tower packed with
crushed rock or wood chips while a
liquid is sprayed downward on the
packing material. The pollutants in
the air stream either dissolve or chem-
ically react with the liquid.
PAN: Peroxyacetyl nitrate, a pollutant
created by the action of sunlight on
hydrocarbons and nitrogen oxides in
the air. PANS are an integral part of
photochemical smog.
particulates: Finely divided solid or
liquid particles in the air or in an
emission. Particulates include dust,
smoke, fumes, mist, spray and fog.
particulate loading: The introduction
of particulates into the ambient air.
pathogenic: Causing or capable of caus-
ing disease.
PCBs: Polychlorinated biphenyls, a group
of organic compounds used in the
manufacture of plastics. In the en-
15
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peat
vironment, PCBs exhibit many of the
same characteristics as DDT and may,
therefore, be confused with that pesti-
cide. PCBs are highly toxic to aquatic
life, they persist in the environment
for long periods of time, and they are
biologically accumulative.
peat: Partially decomposed organic mate-
rial.
percolation: Downward flow or infiltra-
tion of water through the pores or
spaces of a rock or soil.
persistent pesticides: Pesticides that will
be present in the environment for
longer than one growing season or
one year after application.
pesticide: An agent used to control pests.
This includes insecticides for use
against harmful insects; herbicides for
weed control; fungicides for control
of plant diseases; rodenticides for
killing rats, mice, etc.; and germicides
used in disinfectant products, algae-
cides, slimicides, etc. Some pesticides
can contaminate water, air or soil and
accumulate in man, animals and the
environment, particularly if they are
misused. Certain of these chemicals
have been shown to interfere with
the reproductive processes of preda-
tory birds and possibly other animals.
pesticide tolerance: A scientifically and
legally established limit for the
amount of chemical residue that can
be permitted to remain in or on a
harvested food or feed crop as a
result of the application of a chemi-
cal for pest-control purposes. Such
tolerances or safety levels, established
federally by EPA, are set well below
the point at which residues might be
harmful to consumers.
pH: A measure of the acidity or alka-
linity of a material, liquid or solid.
pH is represented on a scale of 0 to
14 with 7 representing a neutral
state, 0 representing the most acid
and 14, the most alkaline.
phenols: A group of organic compounds
that in very low concentrations pro-
duce a taste and odor problem in
water. In higher concentrations, they
are toxic to aquatic life. Phenols are
byproducts of petroleum refining,
tanning and textile, dye and resin
manufacture.
phosphorus: An element that while essen-
tial to life, contributes to the eutro-
phication of lakes and other bodies
of water.
photochemical oxidants: Secondary pol-
lutants formed by the action of sun-
light on the oxides of nitrogen and
hydrocarbons in the air; they are the
primary contributors to photochemi-
cal smog.
photochemical smog: Air pollution as-
sociated with oxidants rather than
with sulfur oxides, particulates, etc.
Produces necrosis, chlorosis and
growth alterations in plants and is
an eye and respiratory irritant in
humans.
phytoplankton: The plant portion of
plankton.
phytotoxic: Injurious to plants.
pig: A container usually made of lead
used to ship or store radioactive
materials.
pile: A nuclear reactor.
plankton: The floating or weakly swim-
ming plant and animal life in a body
of water, often microscopic in size.
plume: The visible emission from a flue
or chimney.
point source: In air pollution, a stationary
source of a large individual emission,
generally of an industrial nature. This
is a general definition; point source is
legally and precisely denned in Fed-
eral regulations. See area source.
pollen: A fine dust produced by plants;
a natural or background air pollutant.
pollutant: Any introduced gas, liquid or
solid that makes a resource unfit for
a specific purpose.
pollution: The presence of matter or
or energy whose nature, location or
quantity produces undesired environ-
mental effects.
polyelectrolytes: Synthetic chemicals used
to speed flocculation of solids in
sewage.
16
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raw sewage
potable water: Water suitable for drink-
ing or cooking purposes from both
health and aesthetic considerations.
ppm: Parts per million. The unit com-
monly used to represent the degree of
pollutant concentration where the
concentrations are small. Larger con-
centrations are given in percentages.
Thus BOD is represented in ppm
while suspended solids in water are
expressed in percentages. In air, ppm
is usually a volume/volume ratio; in
water, a weight/volume ratio.
precipitate—A solid that separates from
a solution because of some chemical
or physical change or the formation
of such a solid.
precipitators: In pollution control work,
any of a number of air pollution con-
trol devices usually using mechanical/
electrical means to collect particulates
from an emission.
pretreatment: In waste water treatment,
any process used to reduce pollution
load before the waste water is intro-
duced into a main sewer system or
delivered to a treatment plant for
substantial reduction of the pollution
load.
primary treatment: The first stage in
waste water treatment in which sub-
stantially all floating or settleable
solids are mechanically removed by
screening and sedimentation.
process weight: The total weight of all
materials, including fuels, introduced
into a manufacturing process. The
process weight is used to calculate
the allowable rate of emission of
pollutant matter from the process.
pulverization: The crushing or grinding
of material into small pieces.
pumping station: A station at which
sewage is pumped to a higher level.
In most sewer systems pumping is
unnecessary; waste water flows by
gravity to the treatment plant.
putrescible: Capable of being decom-
posed by microorganisms with suffi-
cient rapidity to cause nuisances from
odors, gases, etc. For example, kitchen
wastes or dead animals.
quench tank: A water-filled tank used
to cool incinerator residues.
rad: A unit of measurement of any kind
of radiation absorbed by man.
radiation: The emission of fast atomic
particles or rays by the nucleus of
an atom. Some elements are naturally
radioactive while others become radio-
active after bombardment with neu-
trons or other particles. The three
major forms of radiation are alpha,
beta and gamma.
radiation standards: Regulations that in-
clude exposure standards, permissible
concentrations and regulations for
transportation.
radiobiology: The study of the principles,
mechanisms and effects of radiation
on living matter.
radioecology: The study of the effects of
radiation on species of plants and
animals in natural communities.
radioisotopes: Radioactive isotopes. Ra-
dioisotopes such as cobalt-60 are used
in the treatment of disease.
rasp: A device used to grate solid waste
into a more manageable material,
ridding it of much of its odor.
raw sewage: Untreated domestic or com-
mercial waste water.
17
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receiving waters
receiving waters: Rivers, lakes, oceans or
other bodies that receive treated or
untreated waste waters.
recycling: The process by which waste
materials are transformed into new
products in such a manner that the
original products may lose their
identity.
red tide: A proliferation or bloom of a
certain type of plankton with red-to-
orange coloration, that often causes
massive fish kills. Though they are a
natural phenomenon, blooms are be-
lieved to be stimulated by phosphorus
and other nutrients discharged into
waterways by man.
refuse: See solid waste.
refuse reclamation: The process of con-
verting solid waste to saleable prod-
ucts. For example, the composting of
organic solid waste yields a saleable
soil conditioner.
rem: A measurement of radiation dose
to the internal tissues of man.
rep: A unit of measurement of any kind
of radiation absorbed by man.
reservoir: A pond, lake, tank or basin,
natural or man-made, used for the
storage, regulation and control of
water.
resource recovery: The process of obtain-
ing materials or energy, particularly
from solid waste.
reverberation: The persistence of sound
in an enclosed space after the sound
source has stopped.
Ringelmann chart: A series of illustra-
tions ranging from light grey to black
used to measure the opacity of smoke
emitted from stacks and other sources.
The shades of grey simulate various
smoke densities and are assigned num-
bers ranging from one to five. Ringel-
mann No. 1 is equivalent to 20 per-
cent dense; No. 5 is 100 percent
dense. Ringelmann charts are used in
the setting and enforcement of emis-
sion standards.
riparian rights: Rights of a land owner
to the water on or bordering his prop-
erty, including the right to prevent
diversion or misuse of upstream water.
river basin: The total area drained by
a river and its tributaries.
rodenticide: A chemical or agent used to
destroy or prevent damage by rats or
other rodent pests. See pesticide.
rough fish: Those fish species considered
to be of poor fighting quality when
taken on tackle or of poor eating
quality; for example, gar, suckers,
etc. Most rough fish are more tolerant
of widely changing environmental
conditions than are game fish.
rubbish: A general term for solid waste
—excluding food waste and ashes—
taken from residences, commercial es-
tablishments and institutions.
runoff: The portion of rainfall, melted
snow or irrigation water that flows
across ground surface and eventually
is returned to streams. Runoff can
pick up pollutants from the air or
the land and carry them to the re-
ceiving waters.
salinity: The degree of salt in water.
salt water intrusion: The invasion of salt
water into a body of fresh water, oc-
curring in either surface or ground-
water bodies. When this invasion is
caused by oceanic waters, it is called
sea water intrusion.
salvage: The utilization of waste mate-
rials.
sanitation: The control of all the factors
in man's physical environment that
exercise or can exercise a deleterious
effect on his physical development,
health and survival.
sanitary landfill: A site for solid waste
disposal using sanitary landfilling
techniques.
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sewerage
sanitary landfilling: An engineered meth-
od of solid waste disposal on land in
a manner that protects the environ-
ment; waste is spread in thin layers,
compacted to the smallest practical
volume and covered with soil at the
end of each working day.
sanitary sewers: Sewers that carry only
domestic or commercial sewage.
Storm water runoff is carried in a
separate system. See sewer.
scrap: Discarded or rejected materials
that result from manufacturing or
fabricating operations and are suit-
able for reprocessing.
screening: The removal of relatively
coarse floating and suspended solids
by straining through racks or screens.
scrubber: An air pollution control device
that uses a liquid spray to remove
pollutants from a gas stream by ab-
sorption or chemical reaction. Scrub-
bers also reduce the temperature of
the emission.
secondary treatment: Waste water treat-
ment, beyond the primary stage, in
which bacteria consume the organic
parts of the wastes. This biochemical
action is accomplished by use of
trickling filters or the activated sludge
process. Effective secondary treatment
removes virtually all floating and set-
tleable solids and approximately 90
percent of both BOD3 and suspended
solids. Customarily, disinfection by
chlorination is the final stage of the
secondary treatment process.
sedimentation: In waste water treatment,
the settling out of solids by gravity.
sedimentation tanks: In waste water treat-
ment, tanks where the solids are al-
lowed to settle or to float as scum.
Scum is skimmed off; settled solids
are pumped to incinerators, digesters,
filters or other means of disposal.
seepage: Water that flows through the
soil.
selective herbicide: A pesticide intended
to kill only certain types of plants,
especially broad-leafed weeds, and not
harm other plants such as farm crops
or lawn grasses. The leading herbicide
in the United States is 2,4-D. A re-
lated but stronger chemical used most-
ly for brush control on range, pas-
ture, and forest lands and on utility
or highway rights-of-way is 2,4,5-T.
Uses of the latter chemical have been
somewhat restricted because Of labora-
tory evidence that it or a dioxin con-
taminant in 2,4,5-T can cause birth
defects in test animals.
senescence: The process of growing old.
Sometimes used to refer to lakes near-
ing extinction.
septic tank: An underground tank used
for the deposition of domestic wastes.
Bacteria in the wastes decompose the
organic matter, and the sludge settles
to the bottom. The effluent flows
through drains into the ground. Sludge
is pumped out at regular intervals.
settleable solids: Bits of debris and fine
matter heavy enough to settle out of
waste water.
settling chamber: In air pollution control,
a low-cost device used to reduce the
velocity of flue gases usually by means
of baffles, promoting the settling of
fly ash.
settling tank: In waste water treatment, a
tank or basin in which settleable
solids are removed by gravity.
sewage: The total of organic waste and
waste water generated by residential
and commercial establishments.
sewage lagoon: See lagoon.
sewer: Any pipe or conduit used to col-
lect and carry away sewage or storm-
water runoff from the generating
source to treatment plants or receiv-
ing streams. A sewer that conveys
household and commercial sewage is
called a sanitary sewer. If it trans-
ports runoff from rain or snow, it is
called a storm sewer. Often storm
water runoff and sewage are trans-
ported in the same system or com-
bined sewers.
sewerage: The entire system of sewage
collection, treatment and disposal.
Also applies to all effluent carried by
sewers whether it is sanitary sewage,
industrial wastes or storm water run-
off.
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shield
shield: A wall that protects workers from
harmful radiation released by radio-
active materials.
silt: Finely divided particles of soil or
rock. Often carried in cloudy suspen-
sion in water and eventually deposited
as sediment.
sinking: A method of controlling oil spills
that employs an agent to entrap oil
droplets and sink them to the bottom
of the body of water. The oil and
sinking agent are eventually biologi-
cally degraded.
skimming: The mechanical removal of
oil or scum from the surface of
water.
sludge: The construction of solids re-
moved from sewage during waste
water treatment. Sludge disposal is
then handled by incineration, dump-
ing or burial.
smog: Generally used as an equivalent of
air pollution, particularly associated
with oxidants.
smoke: Solid particles generated as a re-
sult of the incomplete combustion of
materials containing carbon.
SOX: A symbol meaning oxides of sulfur.
soft detergents: Biodegradable detergents.
soil conditioner: A biologically stable or-
ganic material such as humus or com-
post that makes soil more amenable
to the passage of water and to the
distribution of fertilizing material, pro-
viding a better medium for necessary
soil bacteria growth.
solid waste: Useless, unwanted or dis-
carded material with insufficient liquid
content to be free flowing. Also see
waste. (1) agricultural—solid waste
that results from the raising and
slaughtering of animals, and the
processing of animal products and or-
chard and field crops. (2) commercial
—waste generated by stores, offices
and other activities that do not ac-
tually turn out a product. (3) indus-
trial—waste that results from indus-
trial processes and manufacturing.
(4) institutional — waste originating
from educational, health care and re-
search facilities. (5) municipal—resi-
dential and commercial solid waste
generated within a community. (6)
pesticide—the residue from the manu-
facturing, handling or use of chemi-
cals intended for killing plant and
animal pests. (7) residential—-waste
that normally originates in a residen-
tial environment. Sometimes called do-
mestic solid waste.
solid waste disposal: The ultimate dispo-
sition of refuse that cannot be sal-
vaged or recycled.
solid waste management: The purposeful,
systematic control of the generation,
storage, collection, transport, separa-
tion, processing, recycling, recovery
and disposal of solid wastes.
sonic boom: The tremendous booming
sound produced as a vehicle, usually a
supersonic jet airplane, exceeds the
speed of sound, and the shock wave
reaches the ground.
soot: Agglomerations of tar-impregnated
carbon particles that form when
carbonaceous-material does not under-
go complete combustion.
sorption: A term including both adsorb-
tion and absorption. Sorption is basic
to many processes used to remove
gaseous and particulate pollutants
from an emission and to clean up oil
spills.
spoil: Dirt or rock that has been removed
from its original location, specifically
materials that have been dredged from
the bottoms of waterways.
stabilization: The process of converting
active organic matter in sewage
sludge or solid wastes into inert,
harmless material.
stabilization ponds: See lagoon, oxidation
pond.
stable air: An air mass that remains in
the same position rather than moving
in its normal horizontal and vertical
directions. Stable air does not disperse
pollutants and can lead to high build-
ups of air pollution.
stack: A smokestack; a vertical pipe or
flue designed to exhaust gases and
suspended particulate matter.
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tolerance
stack effect: The upward movement of
hot gases in a stack due to the tem-
perature difference between the gases
and the atmosphere.
stagnation: Lack of wind in an air mass
or lack of motion in water. Both
cases tend to entrap and concentrate
pollutants.
stationary source: A pollution emitter
that is fixed rather than moving as
an automobile.
storm sewer: A conduit that collects and
transports rain and snow runoff back
to the ground water. In a separate
sewerage system, storm sewers are
entirely separate from those carrying
domestic and commercial waste water.
stratification: Separating into layers.
strip mining: A process in which rock and
top soil strata overlying ore or fuel
deposits are scraped away by me-
chanical shovels. Also known as sur-
face mining.
sulfur dioxide (SO2) A heavy, pungent,
colorless gas formed primarily by the
combustion of fossil fuels. SO2 dam-
ages the respiratory tract as well as
vegetation and materials and is con-
sidered a major air pollutant.
sump: A depression or tank that serves
as a drain or receptacle for liquids for
salvage or disposal.
surfactant: An agent used in detergents
to cause lathering. Composed of sev-
eral phosphate compounds, surfactants
are a source of external enrichment
thought to speed the eutrophication
of our lakes.
surveillance system: A monitoring system
to determine environmental quality.
Surveillance systems should be estab-
lished to monitor all aspects of prog-
ress toward attainment of environ-
mental standards and to identify po-
tential episodes of high pollutant
concentrations in time to take pre-
ventive action.
suspended solids (SS): Small particles of
solid pollutants in sewage that con-
tribute to turbidity and that resist
separation by conventional means.
The examination of suspended solids
and the BOD test constitute the two
main determinations for water qual-
ity performed at waste water treat-
ment facilities.
synergism: The cooperative action of sep-
arate substances so that the total
effect is greater than the sum of the
effects of the substances acting inde-
pendently.
systemic pesticide: A pesticide chemical
that is carried to other parts of a
plant or animal after it is injected or
taken up from the soil or body sur-
face.
T
tailings: Second grade or waste material
derived when raw material is screened
or processed.
tertiary treatment: Waste water treatment
beyond the secondary, or biological
stage that includes removal of nutri-
ents such as phosphorus and nitrogen,
and a high percentage of suspended
solids. Tertiary treatment, also known
as advanced waste treatment, pro-
duces a high quality effluent.
thermal pollution: Degradation of water
quality by the introduction of a
heated effluent. Primarily a result of
the discharge of cooling waters from
industrial processes, particularly from
electrical power generation. Even
small deviations from normal water
temperatures can affect aquatic life.
Thermal pollution usually can be
controlled by cooling towers.
threshold dose: The minimum dose of a
given substance necessary to produce
a measurable physiological or psy-
chological effect.
tolerance: The relative capability of an
organism to endure an unfavorable
environmental factor. The amount of
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topography
a chemical considered safe on any
food to be eaten by man or animals.
Also see pesticide tolerance.
topography: The configuration of a sur-
face area including its relief, or rela-
tive elevations, and the position of its
natural and man-made features.
toxicant: A substance that kills or injures
an organism through its chemical or
physical action or by altering its en-
vironment; for example, cyanides,
phenols, pesticides or heavy metals.
Especially used for insect control.
toxicity: The quality or degree of being
poisonous or harmful to plant or
animal life.
trickling filter: A device for the biologi-
cal or secondary treatment of waste
water consisting of a bed of rocks or
stones that support bacterial growth.
Sewage is trickled over the bed en-
abling the bacteria to break down
organic wastes.
troposphere: The layer of the atmosphere
extending seven to ten miles above
the earth. Vital to life on earth, it
contains clouds and moisture that
reach earth as rain or snow.
turbidimeter: A device used to measure
the amount of suspended solids in a
liquid.
turbidity: A thick, hazy condition of air
due to the presence of particulates or
other pollutants, or the similar cloudy
condition in water due to the suspen-
sion of silt or finely divided organic
matter.
vapor: The gaseous phase of substances
that normally are either liquids or
solids at atmospheric temperature and
pressure; for example, steam and phe-
nolic compounds.
vapor plume: The stack effluent consist-
ing of flue gas made visible by con-
densed water droplets or mist.
vaporization: The change of a substance
from the liquid to the gaseous state.
One of three basic contributing fac-
tors to air pollution, the others are
attrition and combustion.
variance: Sanction granted by a govern-
ing body for delay or exception in
the application of a given law, ordi-
nance or regulation.
vector: Disease vector—a carrier, usually
an arthropod, that is capable of trans-
mitting a pathogen from one orga-
nism to another.
volatile: Evaporating readily at a rela-
tively low temperature.
urban runoff: Storm water from city
streets and gutters that usually con-
tains a great deal of litter and organic
and bacterial wastes.
waste: Also see solid waste. (1) bulky
waste—items whose large size pre-
cludes or complicates their handling
by normal collection, processing or
disposal methods. (2) construction
and demolition waste—building ma-
terials and rubble resulting from con-
struction, remodeling, repair and
demolition operations. (3) hazardous
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1
waste — wastes that require special
handling to avoid illness or injury to
persons or damage to property.
(4) special waste—those wastes that
require extraordinary management.
(5) wood pulp waste — wood or
paper fiber residue resulting from a
manufacturing process. (6) yard
waste—plant clippings, prunings and
other discarded material from yards
and gardens. Also known as yard
rubbish.
waste water: Water carrying wastes from
homes, businesses and industries that
is a mixture of water and dissolved
or suspended solids.
water pollution: The addition of sewage,
industrial wastes or other harmful or
objectionable material to water in
concentrations or in sufficient quan-
tities to result in measurable degrada-
tion of water quality.
water quality criteria: The levels of pol-
lutants that affect the suitability of
water for a given use. Generally,
water use classification includes: pub-
lic water supply; recreation; propaga-
tion of fish and other aquatic life;
agricultural use and industrial use.
water quality standard: A plan for water
quality management containing four
major elements: the use (recreation,
zooplanton
drinking water, fish and wildlife prop-
agation, industrial or agricultural) to
be made of the water; criteria to
protect those uses; implementation
plans (for needed industrial-municipal
waste treatment improvements) and
enforcement plans, and an anti-degra-
dation statement to protect existing
high quality waters.
watershed: The area drained by a given
stream.
water supply system: The system for the
collection, treatment, storage and dis-
tribution of potable water from the
sources of supply to the consumer.
water table: The upper level of ground
water.
zooplankton: Planktonic animals that
supply food for fish.
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