Unit 11: Atmospheric Pollution // Glossary

acid rain: Rainfall with a greater acidity than normal.
aerosols: Liquid or solid particles that are suspended in air or a gas. Also referred to as particulate matter.
ambient: Surrounding, encircling.
carbon monoxide: Odorless, colorless gas that interferes with the delivery of oxygen in the blood to the rest of the body. It is produced as a result of incomplete burning of carbon-containing fuels including coal, wood, charcoal, natural gas, and fuel oil. Depending on the amount inhaled, this gas can impede coordination, worsen cardiovascular conditions, and produce fatigue, headache, weakness, confusion, disorientation, nausea, and dizziness. Very high levels can cause death.
chlorofluorocarbons: Any of several organic compounds composed of carbon, fluorine, chlorine, and hydrogen. They were formerly used widely in industry, for example as refrigerants, propellants, and cleaning solvents.
hydroxyl radical: The neutral form of the hydroxide ion, often referred to as the "detergent" of the troposphere because it reacts with many pollutants, often acting as the first step to their removal.
Intergovernmental Panel on Climate Change (IPCC): Established in 1988 by two United Nations organizations to assess the risk of human-induced climate change.
Montreal Protocol on Substances That Deplete the Ozone Layer: A 1987 international agreement, subsequently amended in 1990, 1992, 1995, and 1997, that establishes in participating countries a schedule for the phaseout of chloroflourocarbons and other substances with an excessive ozone-depleting potential.
National Ambient Air Quality Standards: Standards established by the EPA and required by The Clean Air Act (last amended in 1990) for pollutants considered harmful to public health and the environment.
nitrogen oxides: A group of highly reactive gases, all of which contain nitrogen and oxygen in varying amounts. Many of the nitrogen oxides are colorless and odorless. However, one common pollutant, nitrogen dioxide (NO₂), along with particles in the air, can often be seen as a reddish-brown layer over many urban areas.
nonattainment areas: Defined by The Clean Air Act as a locality where air pollution levels persistently exceed National Ambient Air Quality Standards, or that contributes to ambient air quality in a nearby area that fails to meet standards.
ozone: A triatomic molecule consisting of three oxygen atoms. Ground-level ozone is an air pollutant with harmful effects on the respiratory systems of animals. On the other hand, ozone in the upper atmosphere protects living organisms by preventing damaging ultraviolet light from reaching the Earth's surface.
particulate matter (PM): The sum of all solid and liquid particles suspended in air, many of which are hazardous.
photolysis: A chemical process by which molecules are broken down into smaller units through the absorption of light.
primary air pollutants: Pollutants that are pumped into our atmosphere and directly pollute the air. Examples include carbon monoxide from car exhausts and sulfur dioxide from the combustion of coal as well as nitrogen oxides, hydrocarbons, and particulate matter (both solid and liquid).
radical: Atomic or molecular species with unpaired electrons on an otherwise open shell configuration. These unpaired electrons are usually highly reactive, so radicals are likely to take part in chemical reactions.
secondary air pollutants: Pollutant not directly emitted but forms when other pollutants (primary pollutants) react in the atmosphere. Examples include ozone, formed when hydrocarbons (HC) and nitrogen oxides (NO_x) combine in the presence of sunlight; NO₂, formed as NO combines with oxygen in the air; and acid rain, formed when sulfur dioxide or nitrogen oxides react with water.
smog: A kind of air pollution; the word "smog" is a combination of smoke and fog. Classic smog results from large amounts of coal burning in an area and is caused by a mixture of smoke and sulphur dioxide.
sulfur dioxide: A colorless, extremely irritating gas or liquid (SO₂), used in many industrial processes, especially the manufacture of sulfuric acid. In the atmosphere it can combine with water vapor to form sulfuric acid, a major component of acid rain.
volatile organic compounds: Organic chemical compounds that have high enough vapour pressures under normal conditions to significantly vaporize and enter the atmosphere.

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