Pollution is the introduction of harmful or poisonous substances into an environment.
With the growth of the human population, there has been an improvement in living standards in many areas. However, the demand for resources to support this larger population has also led to an increase in waste and pollution. Few environments remain unpolluted.
The three different types of pollution we will look at are:
Waste 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.
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 releases carbon dioxide, a greenhouse gas that contributes to global warming. It also emits 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.
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 and 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.
Certain plant or animal species, when present or absent, can indicate pollution levels 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 levels and types of pollution, including:
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:
Air quality can be assessed using certain species of lichen as indicators. These organisms are sensitive to pollutants, such as sulfur dioxide.
In areas with clean air, a diverse range of lichen species can be found, whereas heavily polluted areas tend to have fewer species. By studying the presence or absence of lichen, we can estimate the overall air quality in a given location.