Learning outcomes:
understand the biological consequences of pollution of air by sulfur dioxide and by carbon monoxide
understand that water vapour, carbon dioxide, nitrous oxide, methane and CFCs are greenhouse gases
understand how human activities contribute to greenhouse gases
understand how an increase in greenhouse gases results in an enhanced greenhouse effect and that this may lead to global warming and its consequences
understand the biological consequences of pollution of water by sewage, including increases in the number of micro-organisms causing depletion of oxygen
understand that eutrophication can result from leached minerals from fertiliser
understand the effects of deforestation, including leaching, soil erosion, disturbance of the water cycle and of the balance in atmospheric oxygen and carbon dioxide.
You need to know about the following environmental problems;

- Acid rain
- Greenhouse effect
- Eutrophication
- Deforestation

Acid rain:
SO2, CO2 and NOx (oxides of nitrogen) dissolve in rain to form Sulphuric Acid, Carbonic Acid and Nitric Acid. This falls as acid rain, which destroys soil, pollutes waterways and causes erosion.

Greenhouse Effect:

Incoming radiation passes through the atmosphere and hits the Earth, where it is absorbed. The Earth re-emits the radiation as longer-wavelength Infra-Red radiation. This is the problem. IR radiation is absorbed by greenhouse gases on its way out of the atmosphere. This traps the heat in the atmosphere.

The greenhouse gases are: water vapour, CO2, NOX, methane and CFCs

The theory goes that the greenhouse effect is causing global warming, which is bad. Global warming might cause;

- Polar ice cap melting
- Sea levels rising
- Extinction of species living in cold climates
- Changes in rainfall (both droughts and flooding)
- Changes in species distribution (i.e. tropical species spreading, like mosquitoes)

Greenhouse - Gas Source

Water Vapour - Humans haven’t had much effect on this – it’s a naturally occurring greenhouse gas
CO2 - Released from burning fossil fuels
NOX - Released from burning fossil fuels
Methane - Produced by cows (yes, cow farts) and rice paddy fields. As agriculture becomes more and more intensive methane emissions rise
CFCs - Used to be used as coolant in fridges and propellant in aerosols. Now banned, but there are still lots of old fridges in scrap yards leaking CFCs

1. Nitrate enters a waterway (sewage or fertilizer run-off)
2. Nitrate causes algal bloom
3. Algae block out light for plants living on the waterway bed
4. These plants respire as they can't photosynthesize
5. O2 levels fall
6. Fish die
7. Dead fish are decomposed by bacteria, which themselves respire, using up more O2
8. pH levels fall as decomposition produces acids
9. Everything dies. Waterway is incapable of supporting life


Cutting down trees and not replacing them is bad. It causes;

- Leaching of soil minerals
- Soil erosion (no roots holding soil together)
- Desertion (new deserts forming)
- Disturbance of the water cycle (less transpiration can lead to flooding and / or drought)
- Increase in CO2 levels
- Decrease in O2 production

Over-fishing and over-grazing can cause food chains to collapse.