Waste Management (AQA GCSE Combined Science: Trilogy: 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

• Water pollution can be caused by:

  • toxic chemicals

    • E.g. pesticides and herbicides that are sprayed on crops can be washed into watercourses

    • Toxic chemicals can harm cells directly or accumulate along food chains

  • sewage:

    • Poor sewage management can result in sewage running off land or being pumped into watercourses

    • Sewage can deplete oxygen levels in the water as follows:

      1. sewage provides nutrients to bacteria in the water

      2. bacteria multiple rapidly

      3. oxygen in the water is used up during aerobic respiration of bacteria

      4. the dissolved oxygen concentration decreases, killing some aquatic species

  • fertilisers:

    • Fertilisers that are not absorbed by plants can be washed into watercourses when it rains

    • Fertilisers in waterways can cause eutrophication as follows:

      1. fertilisers increase nutrient availability and algae on the surface of the water grow rapidly

      2. algae block light from reaching aquatic plants deeper in the water

      3. aquatic plants die due to lack of photosynthesis

      4. bacteria in the water decompose dead plant matter

      5. bacteria use up oxygen in the water

      6. aquatic organisms die due to lack of oxygen

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Land pollution

• Land pollution can be caused by:

  • landfill

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

    • Negative impacts of landfill include:

      • habitat loss

      • animals becoming entangled in, or eating, non biodegradable plastic waste

      • release of methane (a greenhouse gas) by anaerobic decay of organic waste

      • leaching of toxic chemicals into the soil

  • toxic chemicals

    • Pesticides and insecticides are sprayed on crops to kill pests, causing problems such as:

      • killing non-target animals

      • accumulating along food chains and reaching harmful levels in top predators

    • Herbicides (weedkillers) are sprayed in crops to kill competing weeds

      • These chemicals can reduce plant diversity, reducing the number of food sources for other species

Air pollution

• Air pollution can be caused by:

  • smoke

    • Soot particles settle on leaves, covering them and blocking light, which reduces the rate of photosynthesis

    • Inhaled soot particles can irritate the airways and damage lungs

  • acidic gases

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

    • Acid rain damages leaves directly and alters soil pH

    • Minerals can dissolve in acid rain and be washed into waterways; this can result in mineral deficiency in plants, and can cause eutrophication in water (see above)

    • When acid rain falls over water it can lower the pH of lakes and rivers, causing damage to fish gills

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