Glossary
Acid Deposition
Acidic air pollution that falls to the ground as either particles (dry deposition) or as a solution in rain (wet deposition). The latter is commonly known as "acid rain". Produced from the atmospheric build up of NOx and SO2.
Aldehydes
An organic compound containing carbon, hydrogen and oxygen.
Carbon Dioxide (CO2)
A molecule formed from one atom of carbon and two of oxygen. It is mainly emitted through the burning of fossil fuels and deforestation.
Carbon Monoxide (CO)
A colourless, odourless, poisonous gas.
Catalytic Converter
A device fitted to the exhaust system of a vehicle, which converts the majority of harmful exhaust pollutants, such as hydrocarbons, into less harmful ones.
Concentration
A measure of the atmospheric content of a gas, defined in terms of the proportion of the total volume that it accounts for. Trace gases in the atmosphere are usually measured in parts per million by volume (ppmv), parts per billion by volume (ppbv) or parts per trillion (one million million) by volume (pptv).
Deforestation
Those practices that result in a long-term change of land-use from forest to non-forest uses.
Department of Transport
The British Government agency in charge of transport issues.
European Union
A union of countries in Europe, known as Member States, which try to work together to achieve economic and social equality.
Global Climate Change
A theory that increased concentrations of greenhouse gases are causing an elevation in the temperature of the Earth's atmosphere.
Hydrocarbons (HC)
Any organic compound that contains only carbon and hydrogen.
Industrial Revolution
The rapid growth of industry which began in the late 18th Century and was made possible by the harnessing of energy from fossil fuels.
Nitrogen Oxides (NOx)
The collective term for nitric oxide (NO) and nitrogen dioxide (NO2)
Oxidation
The process by which something undergoes a chemical reaction with oxygen.
Particulate
A particle of an organic or inorganic substance present in the atmosphere that is less than 10 microns (m
m) in diameter.
Pollutants
Substances that are damaging to the environment.
Volatile Organic Compounds (VOCs)
Carbon-containing organic compounds present in the atmosphere as gases. They are an important class of air pollutants found in the atmosphere, occurring mainly at ground level in urban and industrialised centres.