Friday, 11 December 2015

Lecture 2 – Air Pollutants

Pollutant: Contamination in the air

All gases found in the air other than the naturally occurring ones (N2, O2, CO2, Ar and H2O), are amphoteric pollutants. They have become a part of the atmosphere, largely because of urbanization. Some of the common atmospheric pollutants are:
  1. Carbon monoxide; CO
  2. Methane; CH4
  3. Oxides of Nitrogen; NO and NO2
  4. Ozone; O3
  5. Sulphur dioxide; SO2
  6. Unburned hydrocarbons
  7. Chlorofluorocarbon; CFCs
  8. Lead; Pb

Table 1:
Pollutant
Source(s)
Effect(s)
Carbon Monoxide 
CO is formed due to the incomplete combustion of:
  1. Carbon containing compounds
  2. fossil fuel in combustion engines 
CO is poisonous in nature and long exposures to this lead to dizziness, nausea and even death
Methane
Methane enters the atmosphere by:
  1. Bacterial decomposition of vegetable waste
  2. Leakages in gas supply pipelines to homes and industries
Methane is a greenhouse gas and causes global warming
Oxides of Nitrogen
Oxides of Nitrogen are formed by:

  1. Reaction between Nitrogen and Oxygen at high temperatures in internal combustion engines
  2. Natural lightening, which causes Nitrogen to react with atmospheric Oxygen
Oxides of Nitrogen cause:
  1. Acid rain
  2. Respiratory diseases by irritating the respiratory system
Ozone
Ozone is formed by the photochemical reaction of Oxygen.

  
Ozone causes:
  1. Global warming as it is a greenhouse gas
  2. Respiratory diseases by irritating the respiratory system
  3. Eye irritations
  4. decrease in crop yields by retarding plant growth
Sulphur Dioxide
Sulphur dioxide is released in to the atmosphere by:
  1. volcanic eruptions
  2. Combustion of fossil fuel (containing traces of Sulphur) in internal combustion engines
Sulphur dioxide reacts with rain water to form a dilute form of Sulphur Acid, which falls to the ground as acid rain
Unburnt Hydrocarbons
Unburnt hydrocarbons are formed due to the incomplete combustion of fossil fuel in:
  1. homes and industries
  2. internal combustion engines
Unburnt hydrocarbons are carcinogenic in nature
Lead
Lead was added to petrol to make it harder to burn and hence improving the fuel, economically.
Combustion of Leaded fuel from vehicles’ exhausts allowed, lead to enter the atmosphere in microscopic form.
Lead particles in human brain can lead to a decrease in learning abilities and permanent disability in young children