Revision notes · Chemistry of the atmosphere
Common atmospheric pollutants and their sources
Atmospheric pollutants from fuels4.9.3.1
Definition: Incomplete combustion is the burning of a fuel in a limited supply of oxygen, producing carbon monoxide, unburnt fuel, and solid carbon particles.
Combustion of fossil fuels is the primary human source of atmospheric pollution.
- •Most fuels contain carbon and hydrogen, and may also contain sulfur impurities.
- •Complete combustion produces carbon dioxide and water vapour when fuel burns in plenty of oxygen.
- •Incomplete combustion occurs when oxygen is limited, releasing carbon monoxide and solid carbon particulates (soot).
- •Sulfur dioxide is produced when sulfur impurities in the fuel react with oxygen during combustion.
- •Oxides of nitrogen are formed at high temperatures in car engines, causing nitrogen and oxygen from the air to react together.
⚠️ Common mistake: Thinking that nitrogen oxides come from nitrogen inside the fuel, rather than from nitrogen in the air reacting at high temperatures inside engines.
🧠 Remember: High oxygen gives CO₂; low oxygen gives CO and soot.
Properties and effects of atmospheric pollutants4.9.3.2
Definition: Carbon monoxide is a toxic, colourless, and odourless gas produced by incomplete combustion that reduces the oxygen-carrying capacity of blood.
Atmospheric pollutants cause severe damage to human health and the environment.
| Pollutant | Effect |
|---|---|
| Carbon monoxide | Colourless and odourless; binds to haemoglobin, blocking oxygen transport |
| Sulfur dioxide & nitrogen oxides | Respiratory problems; react with water in clouds to form acid rain |
| Particulates | Global dimming (reflect sunlight back to space); lung damage |
- •Acid rain damages limestone buildings, corrodes metal structures, and harms aquatic life and plant species.
⚠️ Common mistake: Confusing global dimming (caused by solid particulates reflecting sunlight) with global warming (caused by greenhouse gases trapping heat).
🧠 Remember: CO starves oxygen, SO₂/NOx cause acid rain, particulates dim the sun.
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