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  • Glossary
| Last Updated:04/02/2015



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Air Pollutant


Any solid, liquid or gaseous substance (including noise) present in the atmosphere in such concentration as may be or tend to be injurious to human beings or other living creatures or plants or property or environment.

Air Pollution

Presence of air pollutant in the atmosphere.



Absorption: The process of taking in, as when a sponge takes up water. Chemicals can be absorbed into the bloodstream after breathing or swallowing. Chemicals can also be absorbed through the skin into the bloodstream and then transported to other organs. Not all of the chemical breathed, swallowed, or touched is always absorbed.



Algae: Simple rootless plants that grow in sunlit waters in proportion to the amount of available nutrients. They can affect water quality adversely by lowering the dissolved oxygen in the water. They are food for fish and small aquatic animals. (Source: US EPA)

Algal Blooms

 Algal Blooms: Sudden spurts of algal growth, which can affect water quality adversely and indicate potentially hazardous changes in local water chemistry. (Source: US EPA)

Alternative energy:

 Alternative energy: Energy that is not popularly used and is usually environmentally sound, such as solar or wind energy.

Acid rain

Acid rain : The precipitation of dilute solutions of strong mineral acids, formed by the mixing in the atmosphere of various industrial pollutants -- primarily sulfur dioxide and nitrogen oxides -- with naturally occurring oxygen and water vapor.


Alpine Area

The part of a mountain above the tree line, but below the permanent snow.


Process by which a compound is reduced in concentration over time, through adsorption, degradation, dilution or some other transformation.


Ability of natural systems to safely absorb waste and residuals. See also absorption.


Disease associated with chronic exposure to asbestos fibres. The disease makes breathing progressively more difficult and can lead to death.


Mineral fibre that can pollute air or water and cause cancer or asbestosis when inhaled.

Artificial Watercourse

Artificially constructed watercourse that serves instream uses (transportation, among others), purposes of water management, irrigation and so forth.

Artificial Water Impoundment

Body of water impounded by a dam, used for the supply of drinking water, electricity generation, irrigation or animal husbandry. Watercourses serving as part of a reservoir system are included.

Anadromous Species

Fish that spend their adult life in the sea but swim upriver to freshwater spawning grounds in order to reproduce.


Soil degradation caused by the accumulation of alkaline water-soluble salts.


Capacity of aqueous media to react with hydroxyl ions. Alkalinity is the factor representing the acid-neutralizing capacity of an aqueous system.


Simple rootless plants that grow in sunlit waters. The decomposition or breakdown of dead algae generally affects water quality adversely by reducing levels of dissolved oxygen. Algae serve as food for fish and small aquatic animals.


Artificial establishment of forests by planting or seeding in an area of non-forest land.

Aerobic Biological Oxidation

Waste treatment using aerobic organisms in the presence of air or oxygen as agents for reducing the pollution load.


Process in which a special solid surface is able to collect gases or vapours. In adsorption, the molecules of gas or liquid adsorbed contract and adhere to the surface of the solid in an extremely thin layer.

Active Ingredient (in pesticides)

Specific chemical that kills or controls target pests. Pesticides are regulated primarily on the basis of active ingredients.

Activated Sludge

 Activated Sludge: sludge containing a high degree of active bacterial mass that is mixed with primary effluent or raw waste water and kept in suspension by aeration and/or agitation to eliminate organic material from the waste water. After decantation, the sludge is recycled into the aeration tank. 


Increase of hydrogen ions, usually expressed as the pH value of environmental media.


 Made by people or resulting from human activities. Usually used in the context of emissions that are produced as a result of human activities.


Annex I Countries/Parties

Group of countries included in Annex I (as amended in 1998) to the United Nations Framework Convention on Climate Change, including all the developed countries in the Organization of Economic Co-operation and Development, and economies in transition. By default, the other countries are referred to as Non-Annex I countries. Under Articles 4.2 (a) and 4.2 (b) of the Convention, Annex I countries commit themselves specifically to the aim of returning individually or jointly to their 1990 levels of greenhouse gas emissions by the year 2000. 

Alternative Energy

 Energy derived from nontraditional sources (e.g., compressed natural gas, solar, hydroelectric, wind).


 The amount of solar radiation reflected from an object or surface, often expressed as a percentage.


 Planting of new forests on lands that historically have not contained forests.


 Small particles or liquid droplets in the atmosphere that can absorb or reflect sunlight depending on their composition.

Adaptive Capacity

 The ability of a system to adjust to climate change (including climate variability and extremes) to moderate potential damages, to take advantage of opportunities, or to cope with the consequences.


Adjustment or preparation of natural or human systems to a new or changing environment which moderates harm or exploits beneficial opportunities.

Abrupt Climate Change

Sudden (on the order of decades), large changes in some major component of the climate system, with rapid, widespread effects.

Atmospheric Lifetime

Atmospheric lifetime is the average time that a molecule resides in the atmosphere before it is removed by chemical reaction or deposition. This can also be thought of as the time that it takes after the human-caused emission of a gas for the concentrations of that gas in the atmosphere to return to natural levels. Greenhouse gas lifetimes can range from a few years to a few thousand years.






: An underground rock formation composed of such materials as sand, soil, or gravel, that  can store groundwater and supply it to wells and springs. In aquifers, groundwater. 

Air Stripping


: A treatment system that removes or “strips” VOCs from contaminated groundwater or surface water as air is forced through the water, causing the compounds to evaporate. Often the compounds are then captured using air filters.

Air Sparging


: An in-situ treatment technology that uses injected air to help remove harmful vapors  from polluted soil and groundwater below the water table by injecting air directly into the saturated  subsurface to encourage the solvents and gasoline to evaporate faster, which makes them easier to  remove with a vacuum.

Air Gap



: An open vertical drop, or vertical empty space, that separates a drinking (potable) water  supply to be protected from another water system in a water treatment plant or other location. This  open gap prevents the contamination of drinking water by backsiphonage or backflow because there  is no way raw water or any other water can reach the drinking water.

Air Binding


: A situation where air enters the filter media. Air is harmful to both the filtration and backwash processes. Air can prevent the passage of water during the filtration process and can cause the loss of filter media during the backwash process.

Activated Carbon


: Adsorptive particles or granules of carbon usually obtained by heating carbon  (such as wood). These particles or granules have a high capacity to selectively remove certain trace  and soluble materials from water.