Case Study on Smoke

Case Study on Smoke

1. Constituents

   • Carbon particles
   • Sulfur dioxide
   • Nitrogen dioxide
   • Water vapour
   • Ground-level ozone
   • Carbon monoxide

2. Causes

   • Incomplete combustion of fuels
   • Coal
   • Diesel
   • General waste
   • Crop waste
   • Wood fuel
   • Grassland
   • Forests

3. Human impacts

   • Respiratory issues and disease (eg. coughing, wheezing and shortness of breath and bronchitis, asthma and lung cancer)
   • Ischaemic heart disease (by promoting plaque growth)
   • Stroke (by hardening arteries in the brain, thickening blood and increasing blood pressure)
   • Development problems in children, particularly of the lungs (due to oxidative stress, inflammation and endocrine disruption)
   • Low birth weight
   • Increased risk of dementia amongst the elderly

4. Environmental impacts

   • Smog
     • Atmospheric dimming
     • Increased risk of temperature inversion
       • Due to increased albedo
     • Smoke + fog = smog
     • Case study: the London smog of 1952
       • Located in a valley
       • About 12,000 deaths
   • Carbon monoxide poisoning
   • Coating plants and other surfaces
     • Reducing the appearance of buildings
     • Inhibiting photosynthesis
   • Acid rain
     • Causing acidification of aquifers and aquatic habitats
       • Increasing the toxicity of heavy metal pollution
     • Damaging external membranes
     • Damaging human structures (eg. marble statues)

5. Controls

   • Legislation
     • The Clean Air Act (1956) which restricted the use of fuels that produce smoke in large urban areas of the UK.
   • Domestic sources
     • Increased use of fuels that do not produce smoke (eg. natural gas or electricity)
   • Transport sources
     • Diesel Particulate Filters (DPF) fitted to exhaust pipes of diesel engines trap up to 80% of smoke particles
   • Industrial sources
     • Electrostatic precipitators
       • In which effluent gases are passed through a chamber with many electrically charged wires/plates. The smoke particles within the gases are attracted to the charged wires/plates and collect together. As particles accumulate they fall to the floor as 'fly ash'.
       • Often used in coal-fired power stations.
     • Cyclone separators
       • Effluent gases are drawn in and forced to rotate in a cylindrical chamber, which throws the suspended particles to the outside surfaces of the chamber where they fall and collect. Thus cleaning the gases so that they can then be discharged through a pipe from the centre of the cylinder.
     • Scrubber
       • Uses fine water spray to wash out suspended solid particulate matter and dissolve soluble gaseous pollutants.
     • Coal treatment
       • Heating coal allows the tar that causes smoke pollution to be drained off, producing smokeless coal.
     • Bag filters
       • Remove smoke particles from effluent gases by trapping them on a fabric filter.
   • More efficient combustion technology
     • A lot of smoke particles are made of unburnt organic matter. If more oxygen is supplied and efficiently mixed, the smoke particles can be completely burnt to gases.
     • Diesel engines produce the most smoke when accelerating too quickly, causing too much fuel to enter the engine for the amount of oxygen available to burn it. Turbo chargers enable more air and therefore more oxygen to be delivered to the combustion chamber which increases the efficiency of the combustion.

6. Critical groups

   • Elderly
   • Pregnant women
   • Children
   • People with cardiovascular disease and/or respiratory disease
   • Communities with poorer air quality

7. Air Quality Index (AQI)

   • On a scale of 0 to 500.
   • The higher the value, the greater the health risk.
   • Over 300 represents hazardous air quality.
   • Over 100 represents unhealthy air quality.