HSRC Glossary

This glossary of environmental engineering definitions was put together by the South and Southwest HSRC at Georgia Institute of Technology.

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z


A

absorption

The process in which molecules of a gas or liquid are taken up and incorporated into the physical structure of another solid or liquid.

acid

A chemical substance with a pH less than 7 on a scale of 0-14. Acids can neutralize bases , and strong acids are corrosive.

acid rain

Any rain, sleet, fog, dew, dust, or other precipitation with a pH less than clean rain (pH 5.6). Acid rain occurs when the by-products of combustion react chemically with air and water in the presence of sunlight to form mineral acids.

adsorption

The process in which the molecules of a gas or liquid adhere to the outer surface of another solid or liquid. Adsorption may retard the diffusion of contaminants.

advection

The transfer of an atmospheric property, such as temperature, by the movement of air, especially horizontally. In environmental science, the movement of water, either internally or externally, through a sediment bed.

aerobic

Oxygen is present. Describes organisms requiring oxygen to live or environments where oxygen is present. Contrast with anaerobic .

aliphatic

Describes a group of organic compounds, including paraffins, olefins, and acetylenes

anaerobic

Oxygen is not present. Describes organisms not requiring oxygen to live or environments where oxygen is not present. Contrast with aerobic .

aquifer

An underground layer of earth that contains groundwater . Aquifers are a major source of drinking water.

aromatic

A type of hydrocarbon , typified by benzene . The name comes from its usually strong odor.

asbestosis

A lung disease caused by exposure to asbestos fibers.

assay

See bioassay .

attenuation

A reduction or weakening of strength or toxicity.

B

base

A chemical substance with a pH greater than 7. Bases can neutralize acids , and strong bases like lime are corrosive.

bench-scale

Refers to a laboratory test.

benzene

A volatile hydrocarbon liquid found in solvents and gasoline. In significant quantities, benzene is considered a hazardous air and water pollutant.

bioaccumulate

To build up a large amount of a substance by ingesting small amounts over an extended period of time.

bioassay

A test using plants, animals, or bacteria to determine the effect of a chemical substance.

bioavailability

The extent to which living organisms can extract toxic chemicals from sediments or other materials. If a substance is not bioavailable, it cannot cause toxic effects.

biodegrade

To naturally break down in the environment. Biodegradation is decay caused by light, temperature, humidity, and microorganisms.

bioremediation

The use of organisms such as bacteria to clean up contaminated areas, typically by providing nutrients to help them break down pollutants.

biotransformation

The use of natural processes to change or eliminate contamination without human intervention.

bioturbation

The natural activity of living organisms, such as worms, to move particles and porewater from inside soil or sediment beds toward the surface and circulate them in the upper layers.

borehole

A hole drilled into the earth, usually to determine the location of minerals or aquifers for wells.

brownfield

An abandoned, idled, or underused industrial and commercial facility where expansion or redevelopment is complicated by real or perceived environmental contamination.

C

capping

Placement of a covering (a cap) of one or more layers of sand, silt, rock, or geotextile fabric, over an established layer of contaminated sediment. The cap seals the sediments physically and chemically, preventing pollutants from migrating into the surrounding water.

chelate

A molecule combining a metal ion with two or more non-metal ions. Chelation may be used to remove ions from solutions and soils.

chlorinated hydrocarbon

A hydrocarbon compound containing chlorine atoms. Chlorinated hydrocarbons such as pesticides persist in the environment and can accumulate within living organisms.

chlorofluorocarbon (CFC)

A chemical compound containing chlorine, fluorine, and carbon, used in cooling systems and aerosols. CFCs absorb infrared radiation and consume ozone in the stratosphere .

chromosome

The thread-like strand of DNA that carries genetic information.

cogener

Any of two chemical substances composed of the same elements in the same proportions but which have different properties because of different structures. Dioxins and PCBs have many cogeners. Similar to isomer .

collagen

A fibrous protein found in bone, tendons, or other connective tissue.

colloid

A suspension of fine particles into a continuous medium such as a liquid.

containment

The process of keeping hazardous or radioactive wastes confined to a particular location, to prevent their accidental release into the surrounding environment.

D

dehalogenation

The reduction or removal of halogens from a chemical compound. Contrast with halogenation .

dense non-aqueous phase liquid (DNAPL)

See non-aqueous phase liquid .

desorption

The release of an absorbed or adsorbed substance, as in contaminants that are released from particles of sediment back into adjoining porewater.

diffusion

The spontaneous mixing of one substance with another, as for example, the movement of gas molecules to the nose and respiratory tract or the spread of liquid contaminants through a sediment bed.

dioxin

A class of chemical compounds containing carbon, hydrogen, oxygen and chlorine, part of a larger group called polycyclic halogenated aromatics. Dioxins are human-made by-products of industrial processes such as incineration, paper milling, pesticide manufacture, and smelting. One dioxin, TCDD , is the most toxic synthetic substance known.

distribution coefficient (Kd)

A measure of how sorbed a substance is to soil or sediment particles, expressed as the ratio of the sorbed-phase concentration to the solution-phase concentration at equilibrium.

DNA

Deoxyribonucleic acid. A major component of living cells which contains the genetic code for the cell.

DNAPL

Dense non-aqueous phase liquid. See non-aqueous phase liquid .

E

effluent

Outflow from a manufacturing or treatment process, in the form of finished products or wastes.

endpoint

The point of termination or final step, when nothing more needs to be done.

equilibrate

To be in, or bring about, equilibrium .

equilibrium

The state of being at rest, in balance, or unchanged. For example, in the process of adsorption , toxic wastes in rivers may contaminate sediments until the wastes in the water and the wastes in the sediment reach a state of equilibrium.

estuary

Place where the mouth of a river reaches the ocean.

ex situ

Removed from the site, not in place. Treatment of hazardous wastes by removing them to another location.

F

fate and transport

The final outcome of a hazardous substance and the physical, chemical, or biological means by which this result occurs.

G

gas chromotography

A method of analysis which the components of a chemical mixture can be separated, identified, or purified. Also called gas-liquid chromotography (GLC), gas-solid chromotography (GSC), or vapor-phase chromotography (VPC).

GC/MS

See gas chromotography and mass spectrometry .

greenhouse effect

The behavior of the earth's atmosphere to trap and hold heat near its surface, causing global warming.

greenhouse gas

Heat-trapping gases that cause global warming. Natural and human-made greenhouse gases include water vapor, carbon dioxide, methane , nitrous oxide, ozone, and chlorofluorocarbons (CFCs).

groundwater

Water that moves slowly underground in an aquifer . Once groundwater has been contaminated, it is nearly impossible to return it to its pure state. The main source of drinking water from wells and springs.

H

halogen

A non-metallic element, such as fluorine, chlorine, bromine, iodine, or astatine.

halogenation

Incorporation of one of the halogens , usually chlorine or bromine, into a chemical compound. Halogenated compounds are more likely to be toxic. Contrast with dehalogenation .

hazardous waste

A substance (gas, liquid, solid, or sludge) that causes, or contributes to, illness or death, or that may substantially threaten human health or the environment when not properly controlled. A waste may be hazardous because it is toxic, ignitable, corrosive, or dangerously reactive.

heavy metal

Metals having a high density, such as lead, mercury, cadmium, arsenic, beryllium, cobalt, and chromium. Many heavy metals are toxic and since they do not easily break down, they can bioaccumulate in living organisms.

hydrocarbon

A chemical compound containing hydrogen and oxygen. Hydrocarbons are found primarily in petroleum, natural gas, and coal products. See also aromatic and chlorinated hydrocarbon .

hydrophilic

Water-loving. Refers to substances that have an affinity for and can dissolve in water, such as carbohydrates, gelatins, or collagens .

hydrophobic

Water-hating. Refers to substances that cannot dissolve in water, such as fats or waxes.

I

immunoassay

An analytical technique that uses antibody molecules as binding agents in the detection and quantification of substances in a sample. Often used to detect hazardous substances in low quantities or demonstrate compliance with governmental standards.

in situ

Present at the site, in place. Treatment of hazardous wastes on site, without removing them to another location.

in vitro

Outside the body, such as a test in a laboratory.

in vivo

Inside the body. Contrast with in vitro .

industrial hygiene

The study and practice of creating a safe workplace.

influent

Materials that flow into a manufacturing or treatment system. Raw materials are often called influents. Contrast with effluent .

inorganic

Not containing hydrocarbons, or not related to living organisms. For example, metals are inorganic.

irreversible compartment

The portion of an adsorbed substance, such as a pollutant, that cannot be desorbed and made bioavailable .

isomer

Any of two chemical substances composed of the same elements in the same proportions but with different structures and different properties. Dioxins and PCBs have many isomers. Similar to cogener .

isotherm

A graphical representation of a mathmatical equation, such as the relationship of the concentration of a contaminant veruss the mass that is adsorbed by soil particles. The Freundlich Isotherm represents a common equilibrium equation.

J

K

Kd

See distribution coefficient .

kinetic

Related to motion and its energy. In physics, refers to the movement of atoms and molecules in solids, liquids, and gases. In chemistry, refers to the rates of chemical reactions.

L

LC

Liquid chromotography. See gas chromotography .

leachate

A liquid formed by passing a solvent, such as water, through another substance. For example, rainwater passing through a landfill or contaminated soil can leach out toxic wastes.

LNAPL

Light non-aqueous phase liquid. See non-aqueous phase liquid .

M

macromolecule

A large molecule that is made up of hundreds or thousands of atoms. Examples include proteins and polymers .

mass spectrometry

A method of chemical analysis in which a substance is vaporized and exposed to strong electric and magnetic fields to separate and measure its components.

membrane

Layer of tissue covering an organism, plant, or cell. See also synthetic membrane .

metaliferous

Containing metals, as in mineral deposits or ores.

methane

An odorless, colorless, combustible natural gas, often found in landfills, swamps, and marshes.

methanogenic

Creating methane. Used to describe the anaerobic bacteria who produce methane during decomposition of organic matter.

microcosm

A small system that is representative of a larger system.

morbidity

Illness, the rate of incidence of a disease. Compare with mortality .

mortality

Death, the rate of incidence of loss of life. Compare with morbidity .

mutagenic

Able to create mutations , and so potentially able to cause infertility or birth defects.

mutation

Small changes in genetic structure of a living cell.

N

nano-

A prefix meaning very small, or 10 to the minus 9th power. For example, a nanogram is 0.0000000001 gram.

NAPL

See non-aqueous phase liquid .

National Priorities List (NPL)

A list of Superfund hazardous waste sites identified by the Environmental Protection Agency for cleanup.

neurotoxin

A poison which damages or affects the nervous system of living organisms.

non-aqueous phase liquid (NAPL)

A chemical that does not dissolve well in water, typically an organic solvent. Dense non-aqueous phase liquids (DNAPLs) have a density greater than water. Light non-aqueous phase liquids (LNAPLs) have a density less than water. NAPLs, particularly DNAPLs can contaminate groundwater creating large underground plumes that persist for very long periods.

non-point source

A source that is so broad, it cannot be pinpointed. such pesticide runoff from farmland. Contrast with point source .

NPL

National Priorities List .

O

organic

Containing hydrocarbons or related to living organisms.

ozone

A chemical compound formed by the action of sunlight on oxygen or automobile emissions. At ground-level and the troposphere , ozone can harm plants and humans. In the stratosphere , it blocks the sun's harmful ultraviolet rays. In the upper troposphere and lower stratosphere it acts as a greenhouse gas.

P

PAH

See polycyclic aromatic hydrocarbon .

particulate

A minute particle. For example, the quantity of particulate in the air is a measure of air pollution.

PCB

See polychlorinated biphenal .

pesticide

Chemicals used to kill pests, such as herbicides to kill weeds and plants; insecticides to kill insects; or fungicides to kill fungi and other micro-organisms.

pH

A measure of the concentration of hydrogen atoms, or the acidity of a chemical substance. pH is measured on a scale of 0 to 14, with 0 being a strong acid, 7 neutral, and 14 a strong base. The scale is logarithmic, with each number representing ten times the strength of the previous one.

photodegradation

The process of decaying or breaking down a substance using light or other radiant energy.

photolytic

Describes chemical compounds that can be degraded by sunlight or other radiant energy.

phytoremediation

Use of plants and vegetation in the bioremediation of hazardous wastes. An example would be the use of poplar trees to clean up DDT residues.

pilot-scale

Describes a test in the field, run as a pilot project.

plume

An area of air, soil, or water containing pollutants released from a single point source . Plumes tend not to mix readily and move slowly, if at all.

point source

A source that can be identified or pinpointed, such as wastes from a pipe or leak. Contrast with non-point source .

polar

Characterized by a positive or negative electrical charge. Polar substances like benzene tend to dissolve in water, while non-polar substances such as pesticides tend to adsorb to soil particles.

polarity

The state of being either positively or negatively charged.

polychlorinated biphenal (PCB)

A class of chemical compounds containing benzine and chlorine atoms. The toxicity of PCBs varies based on the degree of chlorination and the position of chlorine atoms in the overall structure. Examples are pesticides and fire-resistant coatings.

polycyclic aromatic hydrocarbon (PAH)

A group of aromatic hydrocarbons having three or more aromatic nuclei in their structures.

polycyclic halogenated aromatic

See dioxin .

polymer

A natural or synthetic macromolecule made up of combinations of repeating chemical units. Examples include cellulose and plastics.

pore

In geology, a minute space between particles of a solid, such as soil or sediment, which permits the passage of liquids or gases.

porewater

Water present in the spaces between soil or sediment particles.

PPB

Parts per billion. A measure of the concentration of a substance.

PPM

Parts per million. A measure of the concentration of a substance.

pump and treat

A remediation method in which hazardous substances are removed from where they are, pumped off site ( ex situ ), and treated.

Q

R

receptors

Living organisms such as bacteria, algae, worms, or plants that can receive and absorb hazardous substances.

redox

Oxidation-reduction. Used to describes any reaction in which oxygen combines chemically with another substance, or in which electrons are exchanged.

rhizosphere

Area of soil or sediment in and around a plant's roots.

right to know

The right granted by the Superfund Amendments and Reauthorization Act (SARA) for a community to be notified about the risks of materials used or produced within it.

RNA

Ribonucleic acid. A major component of living cells and viruses which plays multiple roles in synthesizing proteins and transmitting genetic information.

S

sediment

Soil material that accumulates in layers beneath water.

sludge

A non-pumpable mixture of solids and liquids. Sludge is typically produced by waste treatment plants, water supply treatment plants, or air pollution control facilities.

slurry

A pumpable mixture consisting of waste particles and liquid.

slurry reactor

In a laboratory, a beaker filled with soil and liquid where chemical reactions can occur.

soil

The top layer of the earth surface not covered by water.

solid waste

Garbage, refuse, sludge, and other discarded material resulting from industrial, commercial, mining, agriculture, or community activities.

solubilize

To make substances like fats dissolve in water by the action of a detergent or surfactant.

solvent

A liquid capable of dissolving a substance and holding it in solution. For example, paint remover is a paint solvent.

sparge

To spray a liquid, or to introduce air or gas into a liquid.

stratosphere

The part of the atmosphere more than five miles from the earth's surface.

Superfund

A nickname for legislation which identified hazardous waste sites (the National Priorities List) and the funds for their clean-up.

surface water

Water at the surface of the earth, including oceans, lakes, rivers, ponds, and streams

surfactant

Surface active agent. A compound, such as a detergent, wetting agent, or emulsifier, that helps to reduce surface tension among liquids and solids.

synthetic membrane

An artificial structure that mimics a cellularmembrane, either to act as a filter or to test the bioavailability of a hazardous substance. Synthetic membranes are typically made from solutions of polymers and solvents.

T

tailing

Any waste product remaining after a substance has been processed. For example, mill tailings are wastes from milling lumber. Mine tailings are wastes from processing ores.

TCDD

Tetrachlorodibenzo-p-dioxin. The most toxic synthetic substance known.

TCE

See trichloroethylene.

thermal pollution

The release of heated waters into natural environments, a process that reduces oxygen levels, harming fish and other living organisms.

toxicity

The condition of being poisonous or harmful to life.

transport

See fate and transport.

trichloroethylene (TCE)

A volatile organic compound used as a common solvent.

troposphere

The part of the atmosphere up to five miles from the earth's surface.

TSD

Treatment, storage, and disposal facilities for hazardous wastes.

U

V

 

VOC

See volatile organic compound.
 

Volatile organic compound (VOC)

Any hydrocarbon (except methane and ethane) which is able to change quickly to a gas. Chlorofluorocarbons (CFCs) are an example.

vadose zone

Soil and rock that are below the land surface and above the water table. Pores contain both water and air. The vadose zone is also called the unsaturated zone since pores are not totally saturated with water.

W

water table

The level of groundwater below the earth's surface. The height of a water table is the depth needed to reach groundwater. The higher the water table, the easier it is to get at the water, but the harder it is to keep it unpolluted.

watershed

An area that drains into one or more river systems or bodies of water.

X

xenobiotic

Foreign to the human body or living organisms. Often used to describe hazardous substances such as pesticides.

Y

Z