Chemistry C1 - Air Quality

Air Quality

• The earth is surrounded by a thin layer of gases called the atmosphere which contain:
  • 78% - Nitrogen (N2)
  • 21% - oxygen (O2)
  • 1% - Argon (Ar) and other noble gases
  • 0.04% - Carbon dioxide (CO2)
  • 0-4% - water Vapour (varies from one location to another and according to the weather conditions)
• The earth's atmosphere is just 15km thick while the diameter of the earth is over 12 000km.
• The different chemicals it contains are just right for Life.
• Human activities have effected the balance of these chemicals and this can effect air quality.

Air pollutants

• Pollutants are chemicals that harm our environment and humans.
• Human activities produce a large number of gases that are released into the atmosphere.
• All of these pollutants are directly or indirectly produced by humans.
• Most of these pollutants are produced by burning fuels which also contribute to global warming.
• Pollutants that harm the environment can also harm humans indirectly. (e.g. acid rain makes the water in lakes and rivers too acidic for plants and animals to survive which has a direct impact on our food chain).
• The earth is heated by the sun but at the same time the earth also radiates heat back out as infrared energy. The earth's greenhouse gases (Methane(CH4), Carbon Dioxide(CO2), Water Vapour) absorb the heat to stop it from escaping into space. This is a greenhouse effect, it keeps the earth warmer then it would be so therefore it is not a bad thing.
• However the increase of greenhouse gases is causing an increase in global warming.
  • Sulphur dioxide (SO2) - causes acidic rain which kills plants and water creatures.
  • Carbon Monoxide (CO) - A poisonous gas which reacts with blood.
  • Nitrogen dioxide (NO2) - causes acidic rain, causes breathing problems, makes asthma conditions worse.
  • Clurofluro Carbons (CFCs) - Damages the ozone layer.
  • Particulates/soot - Microscopic particles of carbon from incomplete combustions of fuel. Makes things dirty, makes lung infections worse, makes asthma worse.
• The better the oxygen the less the particulates in the air. Different fuels produce different amounts of particulates. 

Measuring Pollutants

• The units of measurement used are PPB (parts per billion) or PPM (parts per million). (e.g. a sulphur dioxide concentration of 166ppb means that in every one billion (1 000 000 000) molecules of air there will be 16 sulfur dioxide molecules).
• When measuring the pollutants it is important that the data taken is accurate and important.
• By measuring the concentrations of pollutants in the air it is possible to asses air quality.
• Data is very important to scientists because it can be used to test a theory or explanation.
• Measurements can vary because...
  • Variables (factors that change), like volume of traffic and weather, affect concentrations.
  • all measuring equipment has a limited degree of accuracy.
  • the user's skill will effect the accuracy of the measurement.
• As the measurements vary it is not possible to get a true value however the…