A surrounding medium, such as water or air. Used in contrast to a specific source.

Antidegradation policy
Program or policy to prevent further environmental damage or deterioration.

Growing in, living in, or dependent upon water.

Area of Concern (AOC)
An area recognized by the International Joint Commission, where objectives of the Great Lakes Water Quality Agreement are not being achieved.

Atmospheric deposition
Pollution from the atmosphere associated with dry deposition in the form of dust, wet deposition in the form of rain and snow, or as a result of vapor exchanges.

Atmospheric transport
The movement of chemical substances through the atmosphere to a remote location often over a number of days or weeks.


Barrier wall
A wall constructed underground in a hazardous waste site or landfill to stop the flow of contaminated groundwater.

The land that drains into a waterbody.

Bedrock groundwater
Water flowing through a rock layer underground, under a top layer of mixed soil and loose rock called the overburden.

A PAH that is formed by the incomplete combustion of fossil fuels, wood, and tobacco; the incineration of garbage; and in steel production.

The process by which chemical substances accumulate in the tissues of an organism that drinks contaminated water or eats contaminated food.

The process by which chemical substances become more concentrated in tissues of organisms that eat other contaminated organisms, increasing at higher levels of a food web.

The use of organisms (such as fish or mussels) to evaluate environmental conditions.

Material, other than the principal product, that is generated as a consequence of an industrial process.


A cover over hazardous waste sites or landfills, usually made of clean soils or clay, that prevents rainwater from seeping through soil and causing the contaminants in the soil to flow into the groundwater.

Capture Zone
Area in which groundwater is flowing towards a pumping well;used as remediation technique for hazardous waste sites, to "capture" contaminated groundwater and treat it.

Certificates of Approval
A legal document that permits and controls the manner in which activities are carried out (e.g.,effluent quality limits). They are binding on the recipient and are directly enforceable by prosecution under provincial legislation.

Chemicals of Concern (COCs)
Under the NRTMP, the Four Parties identified 18 priority toxic chemicals as contributing to problems in the Niagara River or Lake Ontario. A commitment was made to reduce by 50% the 10 "chemicals of concern" (out of the 18 priority toxics) with significant Niagara River sources. The GO cobs are benz(a)anthracene, benzo(a)-pyrene, benzo(b)fluoranthene, benzo(k)fluoranthene, hexachlorobenzene, mercury, mirex, PCBs, dioxin, and tetrachloroethylene.

A persistent toxic chemical that was used to control ants, grasshoppers, and other insects on certain crops.

Collection drain
System of pipes around a hazardous waste site or landfill that collects surface or groundwater and directs it toward a treatment plant.

Combined sewer overflow (CSO)
Water discharged into a waterbody from a sewer system that carries both sewage and stormwater runoff. Normally, all of the sewer system's flow goes to a treatment plant, but during a heavy storm, there may be so much stormwater as to cause overflows. When this happens, mixtures of stormwater and sewage may flow into a waterbody untreated.

Consent decree
A legal document, approved by a judge, which puts into effect a remedy (i.e., actions to correct an environmental problem).

A substance that is not naturally present in the environment or is present in amounts that can adversely affect the environment.

Coring/Core sample
To take a sample of sediment by pushing a long hollow tube into the bottom of a river and withdrawing it full of sediment. Coring produces a core sample.

Numerical limits for pollutants in water, air, or sediment, established to protect human health and/or the environment.

Moving across media, such as from air to water, or from water to sediment.


A collection of data arranged for ease and speed of retrieval.

Dichloro-diphynyl-trichloroethane. A persistent toxic chemical that was used as a pesticide, particularly for mosquito control. DDT is banned in U.S. and Canada. DDE and DDD are metabolites of DDT.

A persistent toxic chemical that was used mainly as a soil insecticide.

Dioxin: A family of persistent toxic chemicals known as dibenzo-p-dioxins. Dioxins can enter the environment as the by-products of industrial processes or as a result of combustion processes in incinerators and motor vehicles using leaded fuel. The compound called "2,3,7,8-TCDD" is the most toxic member of the dioxin family.
Furan: A class of chemicals similar to dioxins, which are created at high temperatures, such as incineration of PCBs and other organic wastes containing chlorine.

DNAPL(Dense Non-Aqueous Phase Liquid)
An oily, sludge-like mixture of chemicals that is denser than water. DNAPL flows with gravity or along geological formations, not always in the same direction as groundwater.

In the direction with the flow of a stream or river; downriver. For Niagara River, downstream is towards Niagara-on-the-Lake and Lake Ontario.

Drainage basin
A body of water and the land draining into it.

Removal of sediment from the bottom of a waterbody.


A living system made up of interacting plants, animals, and bacteria, together with their physical and chemical environment.

Ecosystem approach
A way of looking at environmental problems or solutions based on the boundaries of ecosystems, rather than based on political (e.g., country or city) boundaries.

Waste water discharged from sewage treatment plants.

A bay. A part of a waterbody (such as a river or lake) that makes an indentation into the adjacent land.

Discharges into the atmosphere from sources such as smokestacks, motor vehicles, aircraft, and so on.


Food web
The pattern of food consumption in an ecosystem. A food web consists of interacting food chains that are sequences of organisms, each of which eats the next member of the sequence.

A pipe that carries contaminated groundwater drawn out of hazardous waste sites by pumping wells to a treatment plant.

Four Parties
The four agencies who implement the Niagara River Toxics Management Plan: U.S. Environmental Protection Agency, Environment Canada, New York state Department of Environmental Protection, and Ontario Ministry of the Environment and Energy.

See dioxins/furans.


Geographic Information Systems (GIS)
A computer system that is used to compile, analyze, and display geographic data. The system can be used to produce maps relating various environmental features and information to each other.

Great Lakes Water Quality Agreement (GLWQA)
Agreement between U.S. and Canada to restore and maintain the chemical, physical, and biological integrity of the Great Lakes. The GLWQA was first signed in 1978, and was amended in 1983 and 1987.

The fresh or saline waters found beneath the Earth's surface that often supply wells and srings. Contrast to"Surface water".


The place where a particular type of plant or animal lives. An organism's habitat must provide all of the basic requirements for its life.

Hazardous waste
Any substance that is a by-product of society and is classified under U.S. or Canadian law as potentially harmful to human health or the environment. Hazardous wastes are subject to special handling, shipping, storage, and disposal requirements under the law.

Hazardous waste site
Land disposal site for hazardous wastes.

Heavy metals
Metallic elements with high atomic weights that tend to be toxic and bioaccumulate. Examples are mercury, arsenic, lead, etc.

A chemical pesticide designed to control or destroy plants, weeds, or grasses.

Hexachlorobenzene (HCB)
A persistent toxic chemical that was originally manufactured as a fungicide for cereal crops. It is also generated as a byproduct in the manufacture of pesticides and can be formed during the combustion of substances containing chlorine.


Indicator species
A species that can provide a measure of environmental conditions or changes, that can reflect contaminant levels in their environment, or that can give early warnings of environmental problems.

Inorganic substance
A chemical compound that does not contain carbon. Inorganic substances are often derived from minerals.

A chemical used to kill or control the growth of insects.

International Joint Commission (IJC)
A U.S. and Canadian commission, established by the 1909 Boundary Waters Treaty, which makes decisions relating to U.S./Canadian boundary waters, such as the Great Lakes. The IJC monitors implementation of the Great Lakes Water Quality Agreement.


Land disposal site for hazardous (or nonhazardous) wastes.

Load or Loading
The amount of a material entering a system over a given time interval.

Lake Ontario Toxics Management Plan (LOTMP)
A plan for reducing toxic substances in Lake Ontario, implemented by the Four Parties to fulfill a commitment in the NRTMP. The LOTMP is being expanded into a Lake Ontario Lakewide Management Plan to fulfill commitments under the Great Lakes Water Quality Agreement.

Lake Ontario Lakewide Management Plan (LO LaMP)
A plan for the open waters of Lake Ontario that is designed to reduce loadings of Critical Pollutants in order to restore beneficial uses. The Lo LaMP is being developed by the Four Parties in partnership with other natural resources agencies.


Mass balance
A way of evaluating the transport and fate of contaminants in a system by balancing their inputs and outputs.

Medium (plural: Media)
A surrounding substance in the environment: water, air, or sediment.

A substance that is the product of biological changes to a chemical.

A persistent toxic substance that was used as an insecticide and a fire retardant.

Mixing zone
The volume where water from a source of a pollutant mixes with the ambient water body (receiving water).

Involving multiple media, such as water and air, or air and sediment, or all three.


National Pollutant Discharge Elimination System (NPDES)
A U.S. program for controling discharges of pollutants from point sources into waterbodies. The program consists of permits limiting municipal and industrial discharges (see also "state Pollutant Discharge Elimination System").

National Priorities List (NPL)
An EPA list of the most serious uncontrolled or abandoned U.S. hazardous waste sites identified for long-term remedial action under Superfund.

Non-point source
Pollution entering the environment over a widespread area, where the sources cannot be traced to a single, identifiable point. Contrast to "Point source".


Octachlorostyrene (OCS)
A persistent toxic chemical that was released as a by-product when chlorine was manufactured using certain processes that are no longer used.

Organic substance
A chemical compound that contains carbon.

Overburden groundwater
Water flowing through a layer of mixed soil and loose rock that lies over the rock layer called bedrock.


Polycyclic or polynuclear aromatic hydrocarbons. A class of persistent toxic compounds that are formed from the combustion of organic material, such as forest fires or gasoline in cars.

Polychlorinated biphenyls. A group of persistent toxic chemicals used in electrical and hydraulic equipment for insulating or lubricating purposes.

Persistent toxic chemical
Any toxic chemical that is difficult to destroy or that breaks down slowly in the environment (i.e., with a half-life in water greater than eight weeks).

A chemical used for preventing, destroying, or repeling any pest.

Passive In-Site Chemical Extraction Samplers. Sampling devices that can detect toxic chemicals at very low concentrations in water. PISCES consist of a short hollow pipe filled with thick liquid that accumulates toxic chemicals over time, much as a fish does.

Point source
Source of pollution that is distinct and identifiable, such as a pipe from a sewage treatment plant.

Pollution prevention
Any action that reduces or eliminates pollutants before they are created.

Potentially Responsible Party (PRP)
Any individual or company potentially responsible for, or contributing to, the contamination problems at U.S. hazardous waste sites.

Processes used to reduce, eliminate, or alter pollutants from industrial sources before they are discharged into publicly-owned sewage treatment systems.

Priority toxic chemicals
Under the NRTMP, 18 toxic chemicals that exceeded water quality or fish tissue standards in the Niagara River or Lake Ontario. See also "chemicals of concern".


Resource Conservation and Recovery Act. A U.S. program to remediate active hazardous waste sites. sites are remediated by potentially responsible parties whenever this can be arranged.

Record of Decision (ROD)
A public document that explains what actions will be taken to remediate a U.S. hazardous waste site.

Remedial Action Plan (RAP)
Environmental plans aimed at restoring beneficial uses to Great Lakes Areas of Concern.

Water that flows over the land surface into a waterbody.


State Pollutant Discharge Elimination System (SPDES)
A permit system limiting municipal and industrial discharges, administered by states (see also NPDES).


A smaller drainage area within a large drainage basin, such as the Buffalo River sub-basin in the Niagara River basin.

A U.S. program to remediate inactive or abandoned hazardous waste sites in an emergency or for the long-term. sites are remediated by potentially responsible parties whenever this can be arranged.

Surface water
All water open to the atmosphere (e.g., rivers, lakes, reservoirs, seas, etc.).Contrast to "Groundwater".


A persistent toxic chemical that was used as an insecticide.

Toxic substance
Any substance that adversely affects the health or well-being of a living organism. OR A substance that can cause death, disease, birth defects, behavioral abnormalities, cancer, genetic mutations, physiological/reproductive malfunctions, or physical deformities in any organism.

A stream or river that flows into a larger stream, river, or lake.


In the direction against the flow of a stream or river; upriver. For Niagara River, upstream is towards Fort Erie and Lake Erie.


Volatile substance
A substance that evaporates readily.


A body of water and the land that drains into it.

An area that is saturated with water or has a water level at or near the surface. A wetland has organic soils and plant/animal species that are adapted to a wet environment.