5.7 Urban Air Pollution

5.7.1: State the source and outline the effect of tropospheric ozone.

  • Transport
  • Cooking
  • Dust from construction sites and roads
  • Heating
  • Power generation

All these will mean the burning of fossil fuels and release of nitrogen monoxide which then through some process from ozone
  1. NO2 + Sunlight --> NO + O
  2. O + O2 --> O3
  3. O3 + NO --> O2 + NO2
"When fossil fuels are burned, two of the pollutants emitted are hydrocarbons (from unburned fuel) and nitrogen monoxide (nitric oxide, NO). Nitrogen monoxide reacts with oxygen to form nitrogen dioxide (NO2), a brown gas that contributes to urban haze. Nitrogen dioxide can also absorb sunlight and break up to release oxygen atoms that combine with oxygen in the air to form ozone.

Ozone is a toxic gas and an oxidizing agent. It damages crops and forests, irritates eyes, can cause breathing difficulties in humans and may increase susceptibility to infection. It is highly reactive and can attack fabrics and rubber materials."

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5.7.1: Outline the formation of photochemical smog.

Photochemical Smog:
  • Mixture of about one hundred primary and secondary pollutants formed under the influence of sunlight.

The frequency and severity of photochemical smog in an area depend on local topography, climate, population density and fossil fuel use.
  • Precipitation cleans the air and winds disperse the smog
  • Thermal inversions trap the smog in valleys
  • Concentrations of air pollutants can build to harmful and even lethal levels

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5.7.3: Describe and evaluate pollution management strategies for urban air pollution.

Manage strategies
Cars, buses and taxis
Reduce Demand for private cars through public transport
Promote cycle and bus lanes
Restrictions and tolls for car entry to urban areas
Promote cleaner fuels and hybrid or electrical models
Reduce consumption of electricity through building design
Small scale green power on city buildings e.g. solar, wind
Locale power stations away from urban areas
Release and transfer
Cars, buses and taxis
Monitor and regulate exhaust emissions
Electricity and industry
Use cleaner fuels
Clean up emission
Smog prevention
Design and plan city building to promote natural cooling and circulation
Promote opening up and cleaning up of covered water courses to allow evaporative cooling
Raise awareness of conditions and effects of breathing polluted air
Promote pollution related health checks ups
Activated charcoal masks
Provide public access to pollution monitoring

Things to consider in evaluation:

  • Most urban pollution comes from transport , particularly private cars
  • 80% of the car pollution comes from 30% of the cars
  • Diesel engines in trucks and buses produce more particulates
  • Restriction and tools can make car use expensive
  • There may be cultural resistance to public transport
  • Monitoring and regulating is complicated and expansive
  • Groups like WHO set international standards but national standards vary

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