Overview of Air Pollution, The Chemistry Behind Pollution - page 1
Keywords: Environmental Studies
By Vickiduduu on 10/11/2007
Level: Foundation Degree
Page Number: 1 of 5 pages: 1 2 3 4 5
Since the industrial revolution worldwide pollution has been rising and during the last 30 years pollution has risen significantly. Due to this, control of pollution and care for the environment are now at the forefront of debate between politicians and environmental activists. But what exactly is Air Pollution? Air pollution is made up of many different elements, which have both anthropogenic and biogenic sources. As defined by Encarta, [1]
“Air Pollution is the addition of harmful substances to the atmosphere resulting in damage to the environment, human health, and quality of life.”
So, what does this really mean? Where do these pollutants come from? How do chemical, physical and biological agents reshape the atmosphere? What effect do these harmful substances have on our daily lives? And how can we control the effects of air pollution on our environment?
Pollutants can be classified as primary or secondary. Primary pollutants are released directly into the atmosphere either naturally or from human activity, for example sulphur dioxide from domestic fuel combustion or ash particulates caused by volcanic activity. The major primary pollutants can be split into five main categories: Oxides of Sulphur (SOx), Oxides of Nitrogen (NOx), Hydrocarbons or VOC’s,, Particulates or Aerosols (PM10) and Carbon Monoxide (CO.) Secondary pollutants are caused by chemical reactions combining those above once they are in the earths troposphere, for example acid precipitation caused by Sulphur dioxide converting to sulphurous acid in the presence of water.
Most Oxides of sulphur found in the atmosphere are released as bi-products of industrial processes. These processes include electricity generation, smelting of mineral ores, incineration of waste and conversion of wood pulp to paper. During many of these industrial processes sulphur containing fuels such as diesel or coal are burned to produce heat or energy. This gives rise to SO2 and SO3 being produced and released because the Sulphur in the fuel is oxidised during combustion.
Another industrial process that releases SOx is the contact process, used to manufacture sulphuric acid.
Step 1: Sulphur is burned to produce SO2:
S + O2 SO2
Step 2: The SO2 is then oxidised further to produce SO3:
2SO2 + 0.5O2 2SO3
NB: This step can only take place in the presence of a Vanadium Oxide catalyst.
Step 3: Then the SO3 is treated with water to produce sulphuric acid.
SO3 + H2O H2SO4
It is easy to see how SOx are released into the atmosphere through this manufacturing process. All of the above causes
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