Causes of Atmospheric Pollution (AQA GCSE Chemistry): Revision Notes
Atmospheric pollution
What is atmospheric pollution?
Atmospheric pollution happens when harmful substances get into the air around us. These substances are called pollutants.
Most pollution in the atmosphere comes from burning fuels. Coal is made mostly of carbon. Other fuels like petrol and gas contain both carbon and hydrogen. Some fuels also have sulphur in them.
When we burn these fuels, they release many different substances into the air. This makes fuel combustion a major cause of air pollution worldwide.
Main pollutants from burning fuels
When fuels burn, they produce several harmful substances:
Carbon monoxide (CO)
- Made when fuels burn without enough oxygen (incomplete combustion)
- Very dangerous gas
- You cannot see it or smell it
- This makes it hard to detect
Carbon monoxide is extremely dangerous because it's completely invisible and odourless. Many people die from carbon monoxide poisoning each year because they cannot detect its presence.
Carbon dioxide (CO)
- Produced when fuels burn completely
- Not poisonous to breathe
- A greenhouse gas that contributes to climate change
Sulphur dioxide (SO)
- Comes from fuels that contain sulphur
- Has a strong, unpleasant smell
- Causes breathing difficulties
Oxides of nitrogen (NO)
- Include nitrogen monoxide (NO) and nitrogen dioxide (NO)
- Form when fuels burn at very high temperatures
- Cause breathing problems
Particulates (soot)
- Tiny black particles of carbon
- Made during incomplete combustion
- Can be seen as black smoke
Unburnt hydrocarbons
- Fuel molecules that escape without burning
- Released when combustion is not complete
Health problems caused by pollutants
Different pollutants affect our health in various ways:
Carbon monoxide is extremely dangerous. It binds to haemoglobin in your blood instead of oxygen. This stops your blood from carrying enough oxygen around your body. This can kill you.
Sulfur dioxide and nitrogen oxides irritate your lungs and throat. They make breathing difficult and can trigger asthma attacks.
Particulates are tiny particles that get deep into your lungs. They damage lung tissue and make breathing harder.
Critical Health Warning: Carbon monoxide poisoning can be fatal because it prevents your blood from carrying oxygen. Always ensure proper ventilation when using fuel-burning appliances, and install carbon monoxide detectors in your home.
Environmental problems
Acid rain
Sulphur dioxide and nitrogen oxides dissolve in rainwater to make acids. This creates acid rain.
Acid rain:
- Damages plants and trees
- Wears away stone buildings and statues
- Harms fish and wildlife in lakes and rivers
Acid rain has a pH lower than normal rainwater (which is slightly acidic at pH 5.6). Acid rain can have a pH as low as 4.2, making it almost as acidic as vinegar.
Global dimming
Particulates in the atmosphere reflect sunlight back to space. This reduces the amount of sunlight reaching Earth's surface. Scientists call this global dimming.
Global dimming can affect:
- Plant growth
- Weather patterns
- Solar power generation
Global dimming is the opposite effect of global warming. While greenhouse gases trap heat, particulates actually cool the planet by blocking sunlight. However, particulates cause serious health and environmental problems.
Complete vs incomplete combustion
Complete combustion happens when there is plenty of oxygen. This produces mainly carbon dioxide and water vapour.
Incomplete combustion happens when there is not enough oxygen. This produces carbon monoxide, particulates, and unburnt fuel.
Real-World Example: Car Engine Performance
A car engine that is not working properly might not get enough air. This leads to incomplete combustion and more pollution.
- Well-maintained engine + sufficient air → complete combustion → mainly CO and HO
- Poorly maintained engine + insufficient air → incomplete combustion → CO, particulates, unburnt fuel
Key Points to Remember:
- Burning fuels is the main source of atmospheric pollution
- Carbon monoxide is the most dangerous pollutant - it's invisible and can kill
- Particulates and gases like SO and NO cause breathing problems
- Acid rain damages buildings and harms the environment
- Global dimming happens when particles block sunlight
- Complete combustion produces less pollution than incomplete combustion