What was the composition of the atmosphere originally like, and why?
- There was a lot of volcanic activity
- They released a lot of water vapour and carbon dioxide
- There were small amounts of other gases like ammonia and methane, but little to no oxygen
How did the atmosphere become mainly composed of carbon dioxide?
- The water vapour condensed to form oceans
How did the atmosphere become full of oxygen?
- Plants and algae photosynthesised, which reduced the amount of carbon dioxide and increased oxygen
- At first this oxygen oxidised metals
- As most of the metals became oxidised, free oxygen accumulated in the atmosphere
What is the atmosphere’s composition like today?
- 78% nitrogen
- 21% oxygen
- Other gases such as water vapour, carbon dioxide and argon
What is the greenhouse effect?
- Electromagnetic radiation at most wavelengths passes through the Earth’s atmosphere
- The Earth absorbs most of the radiation and warms up
- It then radiates the energy as infrared radiation
- Some of the (longer wavelength) radiation goes into space
- Some is absorbed by greenhouse gases in the atmosphere
- They emit infrared radiation in all directions, which warms up the Earth’s atmosphere and surface
Give 2 examples of greenhouse gases.
- Carbon dioxide
- Methane
Why is the concentration of carbon dioxide in the atmosphere increasing?
- The combustion of fossil fuels
What is the definition of anthropogenic?
- Caused by human activity
Why are increasing levels of carbon dioxide and methane in the atmosphere a problem?
- They have the potential to cause an enhanced greenhouse effect
- It leads to global warming, which leads to melting ice caps, rising sea levels and climate change
- Climate change causes floods and problems with farming and disease
How can greenhouse gas emissions be reduced?
- Using fewer fossil fuels, by using renewable sources of energy such as biofuels instead
- Using carbon capture technology to stop carbon dioxide from escaping when fuels are burnt
How can the effects of climate change be reduced?
- Building flood defences
- Planting different crops
What are some pollutants released by the combustion of fossil fuels?
- Carbon monoxide
- Sulfur dioxide
- Oxides of nitrogen
- Particulates
In what situation are carbon monoxide and particulates produced by fossil fuels?
- Incomplete combustion
- They are also sometimes produced by vehicle engines
- Particulates are also produced by industrial processes
What problems does carbon monoxide cause?
- It’s toxic
- It’s also colourless, tasteless and odourless
- It binds to haemoglobin in the blood, and therefore reduces its capability to carry oxygen
- It causes drowsiness, breathing difficulties and even death
What problems do particulates cause?
- They’re small particles
- They can therefore settle in the lungs if breathed in, and cause breathing difficulties
How is sulfur dioxide produced?
- Hydrocarbons contain sulfur impurities
- The sulfur is oxidised so it forms sulfur dioxide gas
How are oxides of nitrogen produced?
- Nitrogen and oxygen do not normally react together
- Temperatures in vehicle engines are high enough for them to react together to form nitrogen monoxide
- Nitrogen monoxide is then oxidised in the air to form nitrogen dioxide
- Together these 2 oxides of nitrogen are called NOx
Why are acidic oxides bad for the environment?
- Nitrogen dioxide and sulfur dioxide dissolve in water in clouds
- They causes acid rain
Why is acid rain a problem?
- It kills trees
- It kills living things in rivers and lakes
- It damages stonework and corrodes metal
What issue do atmospheric pollutants cause together?
- They react together in sunlight to form a harmful photochemical smog
How is fresh water made potable?
- It is passed through a screen to remove large objects such as branches and leaves
- A coarse filter bed made of sand and gravel removes large insoluble particles
- Aluminium sulfate is added which causes fine particles to clump together and settle at the bottom in a sedimentation tank
- A fine filter bed removes very small insoluble particles
- Chlorine gas is added to kill harmful microorganisms
How is seawater made potable, and why is this an issue?
- It is distilled
- This requires a lot of energy, so is not suitable for large amounts of water
- It is therefore only used in countries where other options are unavailable, or energy resources aren’t expensive
How is sewage water treated?
- Screening and grit removal to remove large particles
- Sedimentation; tiny particles settle out from the water and form sewage sludge
- The sewage sludge is digested anaerobically by bacteria
- The effluent (the liquid that was on top of the sewage sludge) is treated with aerobic bacteria
