The atmosphere comprises various gases, water vapour, aerosols and suspended solid material. A large proportion of the gases and chemical compounds are naturally occurring (e.g. nitrogen, water vapour, carbon dioxide) or produced by natural processes (e.g. sulphur dioxide and particles from volcanism, methane from marshes). However, a proportion of the gases and particles are produced by humans and their activities.

For example:

The process of burning or combustion is an exothermic (heat releasing) chemical reaction between oxygen (chemical symbol 'O') (a constituent of the air we breathe) and another ‘combustible’ material or substance.

The burning of fossil fuels (which are primarily composed of carbon - 'C') produces carbon dioxide (CO2), water vapour (H2O) and sulphur oxides (SOx) (as hydrogen -'H' and sulphur -'S' are also constituents of fossil fuels). Oxides of nitrogen (NOx) also form if the temperature of the reaction is high enough.

The burning of ‘biofuels’ e.g. wood, animal dung, and charcoal, which contain cellulose and lignin apart from producing aCO2 and H2O also results in the emissions of Polycyclic Aromatic Hydrocarbons (PAHs e.g. Benzo[a]pyrene), and particles.

The use of certain chemicals in industrial processes results in emissions of hydrocarbons (HCs) and volatile organic hydrocarbons (VOCs) which can lead to the formation of low level ozone or the depletion of high level (stratospheric) ozone.

Most of these chemicals and compounds undergo further reactions in the atmosphere.

At certain concentrations some of these gases, chemical compounds and particles in the atmosphere adversely affect humans and eco-systems. There is also a growing scientific consensus that increasing concentrations of carbon dioxide and methane may be contributing to the observed increase in average global temperatures (‘global warming’).

Some of the pollutants that occur in the lower atmosphere and therefore affect humans and eco-systems more directly are designated in the Air Quality Objectives (which is a transposition of EU directives) together with objectives, standards and limit values. The monitoring and ‘management’ of these is facilitated by the Local Air Quality Management (LAQM) process.

www.nottinghamcity.gov.uk/sitemap/services/environment/pollution/air_pollution/air_quality.htm

The pollutants which are transboundary or global in their potential effects are subject to international treaties, protocols and (in most cases) legislative control. Emissions from industrial and commercial activities and installations are monitored and regulated by the Integrated Pollution Prevention and Control regime administered by the Environment Agency, and by local authorities as the Local Authority Pollution Prevention and Control (LAPPC) regime.

www.nottinghamcity.gov.uk/sitemap/services/environment/pollution/cdpc_authorised_processes.htm

Reviewed 14 March 2007 RST