What is in the Atmosphere?
- 78% Nitrogen
- 21% Oxygen
- 1% Argon
Human activity and volcanic eruptions have added gases and particulates to the air.
- Particulates- tiny pieces of solid.
- Many of these gases and particulates are pollutants - they affect air quality.
How was the atmosphere formed?
- Early atmosphere - mainly Carbon dioxide and Water Vapour ( from volcanoes).
- Earth cooled- Water vapour condensed into oceans.
- Carbon dioxide dissolved in oceans- made sedimetary rocks. Some ended up in fossil fuels.
- The amount of oxygen increased- photosynthesis in plants; took carbon dioxide from the atmosphere, added oxygen.
How do reactions make air pollutants?
- Coal is mainly Carbon. Petrol, Diesel and fuel oils are mainly Hydrocarbons.
- Hydrocarbons- Compounds of Hydrogen and Carbon only.
- Fossil fuels burn & react with Oxygen in the air. Products are; Carbon Dioxide and Water.
- In a chemical reaction, the total mass of the products is equal to the total mass of the reactants.
What are Oxidation and Reduction reactions?
- Oxidation- adds oxygen to a chemical.
- Burning of fossil fuels is an example of Oxidation.
- Fuels burn more quickly in pure oxygen than in air.
- Reduction- removes oxygen from a chemical.
Where do Air Pollutants come from?
- Burning fossil fuels makes Carbon Dioxide. - If there isnt enough oxygen present, incomplete burning, Carbon Monoxide and particulate Carbon is made.
- Some fossil fuels contain Sulfur. -when burnt, Sulfur reacts with Oxygen to form Sulfur Dioxide.
- At high temperatures in an engine, Nitrogen and oxygen from the air react to form Nitrogen Oxides.- Nitrogen Monoxide forms first, reacts with more Oxygen, makes Nirogen Dioxide.
What problems do air pollutants cause?
Pollutants do not just disappear. Some remain in the atmosphere and harm humans directly:
- Carbon monoxide- Reduces the amount of Oxygen the blood can carry.
Some humans harm the environment, harm humans indirectly:
- Sulfur dioxide and oxides of Nitrogen - React with Water and Oxygen to form acid rain.
- Carbon dioxide- Contributes to climate change.
- Carbon Particulates- Make surfaces dirty.
How can we improve Air Quality?
- Carbon dioxide- Burn less fossil fuels.
- Use less electricity.
- Remove sulfur impurities form fuels before burning them.
- Remove Sulfur dioxide and particulates from flue gases.
Sulfur dioxide(acidic) - Removed by reacting it with an alkali (Wet Scrubbing).
- Sea water- Flue gases are sprayed with sea water.
- Calcium oxide solution- reacts with Slfur dioxide to make Calcium Sulfate.
How can we improve Air Quality ?(continued)
- Develop efficient engines- burn less fuel.
- Use low Sulfur fuels.
- Use Catalytic coverters to:
- Add Oxygen to Carbon Monoxide.
-Remove Oxygen from Nitrogen Monoxide.
- Use public transport.
- Have legal Limits on exhaust emissions.
- Fuel vehicles with biofuels or use electric cars.
-Biofuels- made from plants like sugar cane. They are Carbon neutral. The plants grow on land that could be used for food crops.
-Electric vehicles- Powered by batteries. Do not produce waste gases. The electricity may have been generated by burning fossil fuels and the cars need to be charged often.