Waste Management (AQA GCSE Biology): Revision Note

Human population

• Human population growth globally has been increasing exponentially for the last 150 years

 Graph of human population over time

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• There are many reasons for this exponential growth, including:

  • Improved technology leading to an abundance of food = rapid increase in birth rate

  • Improved medicine, hygiene and health care = decrease in death rate

• Rapid growth in the human population and an increase in the standard of living have led to increasingly negative effects on the environment

• As increasingly more resources are used to sustain the growing human population, more waste is produced and more pollution is created

• Unless waste and chemical materials are properly handled, pollution will continue to be created

Pollution

Water pollution 

Sources of water pollution and their effects:

1. Toxic chemicals (pesticides and herbicides)

• Source/cause:

  • Sprayed on crops to prevent damage by insects and growth of weeds

  • Runoff occurs from agricultural land if these toxic chemicals are applied in too high a concentration, causing them to enter watercourses.

• How pollutant affects biodiversity:

  • These chemicals cannot be broken down by organisms

  • They can be absorbed by aquatic plants or invertebrates and can build up in the tissues of these organisms over time

  • This is called bioaccumulation

  • At each stage of the food chain, increasing levels of the chemicals build up in organisms, which can eventually build up to dangerously toxic levels in top predators, leading to death or failure to breed.

  • This is called biomagnification

2. Untreated sewage

• Source/cause:

  • Lack of sewage treatment plants in inhabited areas (due to poor infrastructure or lack of money) meaning sewage runs or is pumped into watercourses

• How pollutant affects biodiversity:

  • Sewage provides a good source of food for bacteria which increase rapidly, depleting the oxygen dissolved in the water (as they respire aerobically)

  • This lack of oxygen eventually results in the death of aquatic organisms such as fish and aquatic invertebrates

  • This is known as eutrophication

3. Fertilisers

• Source/cause:

  • Runoff occurs from agricultural land if fertilisers are applied in too high a concentration, causing fertilisers to enter watercourses

• How pollutant affects biodiversity:

  • Fertiliser causes increased growth of algae and water plants

  • The resulting ‘algal bloom’ blocks sunlight so water plants on the bottom start to die, as does the algae when competition for nutrients becomes too intense

  • Dead plants and algae are a good source of food for bacteria

  • This eventually leads to eutrophication and the death of many aquatic organisms.

Biomagnification and bioaccumulation diagram

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Diagram of eutrophication

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Land pollution 

Sources of land pollution and their effects

1.Toxic chemicals (pesticides and herbicides)

• Source/cause:

  • When sprayed onto crops, these toxic chemicals also get into the soil

• How pollutant affects biodiversity:

  • These chemicals cannot be broken down by organisms

  • They can be absorbed by plants or taken in by other organisms living in the soil and can build up in the tissues of these organisms over time

  • This is called bioaccumulation

  • At each stage of the food chain, increasing levels of the chemicals build up in organisms, which can eventually build up to dangerously toxic levels in top predators, leading to death or failure to breed

  • This is called biomagnification

2. Discarded rubbish

• Source/cause:

  • Household waste that cannot be recycled is buried in landfill sites

• How pollutant affects biodiversity:

  • Landfill sites take up a lot of room and their creation often results in the destruction of natural habitats

  • Toxic chemicals can spread from the waste into the soil

  • Much rubbish, such as that made from plastic, is non-biodegradable and remains in the environment for hundreds of years

Air pollution 

Sources of air pollution and their effects

1. Sulphur dioxide and nitrogen oxides

• Source/cause:

  • Combustion of fossil fuels that contain sulphur impurities creates sulphur dioxide

  • Nitrogen oxides are also produced during fossil fuel combustion

  • These gases react with oxygen and dissolve in rainwater to produce dilute sulphuric acid and nitric acid, which leads to acid rain

• How pollutant affects biodiversity:

  • Acid rain can damage the leaves, buds, flowers and roots of trees and other plants. It can make rivers and lakes too acidic, resulting in the death of certain aquatic organisms

  • It can also cause the leaching of minerals that are toxic to fish, such as aluminium, into lakes

Diagram of air pollution and acid rain

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