How do nitrates contribute to water pollution?

Nitrates contribute to water pollution by causing excessive growth of algae, known as algal blooms, in water bodies.

Nitrates are a type of nutrient that plants need to grow. They are often found in fertilisers and can enter water bodies through agricultural runoff, sewage discharge, and industrial waste. When the concentration of nitrates in water bodies increases, it can lead to a condition known as eutrophication. This is characterised by the excessive growth of algae and other aquatic plants, known as algal blooms.

Algal blooms can have a detrimental effect on the water quality and the overall health of the aquatic ecosystem. As the algae grow rapidly, they block sunlight from reaching other aquatic plants. When these plants die due to lack of sunlight, bacteria break them down in a process that consumes oxygen. This leads to a decrease in the oxygen levels in the water, creating a condition known as hypoxia or 'dead zones', where most marine life cannot survive.

Moreover, some types of algae produce toxins that can be harmful to other aquatic life, as well as humans and animals that drink or come into contact with the contaminated water. These toxins can cause a variety of health problems, including skin irritation, stomach cramps, vomiting, nausea, diarrhoea, fever, sore throat, headache, muscle and joint pain, and even liver damage.

In addition, high levels of nitrates in drinking water can be harmful to humans, especially infants. This condition, known as methemoglobinemia or 'blue baby syndrome', can interfere with the oxygen-carrying capacity of the child's blood, leading to serious health problems.

Therefore, it is crucial to manage and control the use of nitrates, especially in agricultural practices, to prevent their excessive accumulation in water bodies and the consequent water pollution.