Pollution is the introduction of harmful or poisonous substances into an environment.

The growing human population has contributed to an improvement in living standards. However, the demand for resources to support this larger population has also led to an increase in waste and pollution. There are not many environments left that are not polluted.

The three different types of pollution we will look at are:

  • Land pollution
  • Air pollution
  • Water pollution

Land Pollution

The rubbish that cannot be recycled is buried in landfill sites. These are large holes in the ground where we dump disposable waste. Toxic chemicals from the waste can get into the soil (e.g. pesticides or batteries). If organisms eat the plants that are covered in these toxic chemicals, they can accumulate further up the food chain. This can poison predators in the process.

Air Pollution

Burning fossil fuels and other materials releases smoke into the air, which contains tiny solid particulates that can remain suspended in the atmosphere and contribute to smog. When inhaled, these particulates can cause damage to the lungs and respiratory system in humans and animals.

The combustion of fossil fuels also releases carbon dioxide, a greenhouse gas that contributes to global warming, and acidic gases such as sulfur dioxide and nitrogen oxides. These gases dissolve in rainwater to form acid rain, which can have negative impacts on ecosystems and infrastructure.

Air pollution can be blown from one location to another by the wind. So, pollution in one area can produce acid rain in another area or even a different country.

Water Pollution

Farmers use pesticides and herbicides to protect their crops from pests and diseases. However, if runoff occurs, these toxic chemicals can wash into rivers and lakes, where they can be absorbed by aquatic plants.

Over time, these chemicals can build up in the tissues of organisms through a process called bioaccumulation. As they cannot be broken down by these organisms, they can accumulate to potentially harmful levels. This poses a threat to the health of the affected organisms and the ecosystem as a whole.

The amount of toxic chemicals will increase at each stage of the food chain. Therefore, the top predators will have very toxic levels, which can lead to death.

Nitrate fertilisers are soluble in water. So, when the rain washes it off fields, it can reach rivers and lakes, which can lead to eutrophication.

As there are a lot of nitrates and phosphates. the algae will grow rapidly and die. Microorganisms will break down the algae, using a lot of oxygen for respiration. This will reduce oxygen levels for the aquatic organisms nearby.

  • The algae also block off sunlight, so underwater plants die and rot.

Indicator Species

The presence or absence of certain plant or animal species can serve as indicators of pollution in an ecosystem. For example, the absence of certain species that are sensitive to pollution may suggest that there are pollutants in the environment.

We can use indicator species to determine the level of:

  • Water pollution
  • Air pollution

Water quality

Certain aquatic species, such as fish or amphibians, can be used as indicators of water pollution. The presence or absence of these species, or changes in their populations, can provide information about the health of a water body and the presence of pollutants. For example:

  • Polluted water is often seen in the presence of bloodworms or sludge worms.
  • Water that contains freshwater shrimps and stoneflies indicates that the water in the area is clean and unpolluted.

Air quality

Air quality can be assessed using certain species of lichen as indicators. These organisms are often sensitive to pollutants, such as sulphur dioxide, and their presence or absence can provide information about the level of pollution in an area. In areas with clean air, a diverse range of lichen species can be found.

Heavily polluted areas tend to have fewer lichen species present. By studying the presence or absence of lichen species, we can get a sense of the overall air quality in a given location.