The substances that pollute the air are called air pollutions.They come from both natural sources and from human activities.Volcanoes,forest fires and biological processes(eg. digestion in animals and decay of dead matter) are examples of natural sources of air pollutants.Pollution from human activities is mainly due to the burning of fuels in motor vehicles,factorises and power stations.
The most common source of air pollution is the combustion of fossil fuels. This usually happens in vehicle engines and power stations. The table below shows some of the common air pollutants formed.
|smoke||Deposits soot on buildings and trees, causing them damage. Permeates the air, making it difficult for living creatures to breathe.|
|carbon monoxide||poisonous gas|
|carbon dioxide||greenhouse gas that contributes to global warming|
|sulfur dioxide||contributes to acid rain|
Factories can cause air pollution
Indicators of air pollution
Lichens are plants that grow in exposed places such as rocks or tree bark. They need to be very good at absorbing water and nutrients to grow there, and rainwater contains just enough nutrients to keep them alive. Air pollutants dissolved in rainwater, especially sulfur dioxide, can damage lichens, and prevent them from growing. This
makes lichens natural indicators of air pollution. For example:
- Bushy lichens need really clean air.
- Leafy lichens can survive a small amount of air pollution.
- Crusty lichens can survive in more polluted air.
In places where no lichens are growing, it's often a sign that the air is heavily polluted with sulfur dioxide.
Harmful Affects of Sulphur Dioxide
Sulfur dioxide in the atmosphere is absorbe d by soils and plants, thus adversely effecting their growths. It is also captured within and below clouds and in certain circumstances may raise the acidity of the resultant rain which is known as acid rain.
In the atmosphere, sulphur dioxide mixes with water vapour producing sulphuric acid.
Exposure of the eyes to liquid sulfur dioxide, can cause severe burns, resulting in the loss of vision. Other health effects include headache, general discomfort and anxiety. Those with impaired heart or lung function and asthmatics are at increased risk. Repeated or prolonged exposure to moderate concentrations may cause inflammation of the respiratory tract , wheezing and lung damage which eventually cause breathing problems.
Sulphur dioxide (SO2) enters the atmosphere as a result of both natural phenomena and anthropogenic activities, such as coal and oil burning, and SO2 is therefore one of the atmospheric species related to air pollution. These emissions may have an impact on air quality and therefore it is useful to monitor these compounds.
For the Air Quality SO2 Service, a set of geographic regions covering industrialised has been defined and each of these regions is monitored. Concentrations of SO2 are derived from UV measurements by satellite based instruments.
Sulphur Dioxide As An Air Pollutant.
Ways of reducing Sulphur Dioxide
Alternative use of cleaner fuels
Cars and vehicles are needed to install a specail fuel tanks that can contain cleaner fuels such as compresses natural gas (CNG) or natural gas vehicles (NGV) which contain no sulp hur. These fuels are used instead of diesel as they are environment-friendly.
Reducing Sulphur Dioxide emissions from power stations
Powered limestone (calcium carbonate) is added to the hot gases produced from the burning of fuels at a coal or oil burning power station. The heat decomposes the limestone to give calcium oxide.
CaCO3 (s) -> CaO (s) + CO2 (g)
The calcium oxide then removes the sulphur dioxide as calcium sulphate.
CaO (s) + So2 (s) -> CaSO3 (s)
95% of the sulphur dioxide is removed by these reactions. The calcium sulphite,CaSO3, is reacted with air to convert it into unreactive calcium sulphate, CaSO4, and then it is dumped.
Sulphur forms two main oxides; the gas sulphur dioxide (SO2) and the liquid sulphur trioxide (SO3). Sulphur dioxide is a dense colourless gas, which is soluble in water, and has a suffocating and unpleasant smell of burnt matches. It has a melting point of -72.7°C, and a boiling point of -10°C.
Sulfur dioxide can be prepared by burning sulphur:
S8(s) + O2(g) → SO2(g)
- On-line product information
- Overview of the regions of the Air Quality SO2 Service
- Highlights of SO2 emissions related to anthropogenic activities:
- [to come]
- Document Sulphur dioxide monitoring within TEMIS corresponding to version 0.9 of this Data Service, and delivered on 29 November 2006.
Nitrogen Oxides As An Air Pollutant.
Sources of Nitrogen Oxides
The main air pollutants are nitrogen monoxide and nitrogen dioxide, which we call both of them NOx
The nitrogen monoxide combines with more oxygen to become nitrogen dioxide, a brown gas.
2NO(g) + O2(g) -> 2NO2(g)
These oxides are produced during combustion, and are of interest as air pollution. If nitric oxide (NO) is in the presence of excess oxygen (O2) then it will be converted to nitrogen dioxide (NO2) depending on the concentration of air as shown below:
and some sources are from koravee :)