Acidification: Acid rain

Leon really likes carbonated water, he thinks it’s very refreshing! He imagines swimming in a lake filled with bubbly water. That would be amazing, right? Well, nature certainly wouldn’t enjoy a lake of carbonated water as much as you would, Leon. Why not?

Let’s see! When you drink carbonated water, it tastes a bit more sour than regular tap water. This is because it contains carbon dioxide, a gas which makes it bubbly. Some of the gas reacts with the water molecules, and forms carbonic acid. The hydrogen ions released in this reaction increase the ACIDITY of the water.

In fact, most of the water in nature, such as in clouds, glaciers, and lakes, is slightly acidic. It contains small amounts of carbonic acid, because it absorbs carbon dioxide from the air. But acidity higher than this normal level can be really harmful to the environment. Carbon dioxide is not the only gas that easily dissolves in water, and reacts to form an acid. - Air pollutants such as sulphur dioxide and nitrogen oxides can do that too. These gases are sometimes produced in natural processes like volcanic eruptions.

Nowadays, however, most of the air pollutants are released from the burning of coal and other fuels, used for example to generate electricity. Pollutants are also present in fumes from cars, aircraft, and other vehicles, and are often produced by industry. When released into the air, sulphur dioxide and nitrogen oxides react with water vapour and produce acidic compounds. Later, these blend with other substances and form clouds that are much more acidic than normal. When the water falls down to earth, it carries the acids with it.

We call this ACID RAIN, but it can be any form of precipitation - rain, snow, or hail. Acid rain changes the acidity of the soil, and the acidity of the fresh water in lakes and streams, which affects organisms living there. When acidic water falls on the ground, aluminium and heavy metals, such as lead, are released from the soil. These have negative effects on the environment, and are toxic to living organisms. They kill bacteria in the soil that are important for producing nutrients.

They also damage the roots, which makes it more difficult for plants to obtain nutrients and water. The plants become weaker and more susceptible to diseases. This happens to forests, causing them to die, and also to agricultural fields, negatively affecting food production. Some of the aluminium and heavy metals get washed out from the soil and end up in lakes, streams and rivers. Acids and toxic elements pollute the water and affect all the organisms living there.

Many aquatic species are very sensitive to changes in acidity; they can’t reproduce, some become sick—or even die. This also in turn, even affects animals that don’t live in water, such as fish-eating birds whose food supply diminishes, or who get poisoned by heavy metals. Acid rain disturbs natural ecosystems, but also affects man-made objects such as buildings, statues, and bridges. The acid can dissolve some materials, like marble and limestone, or corrode metals, such as copper and bronze, causing damage to objects that are exposed to acid rain. Acid rain is mainly caused by pollutants, so the only way to protect our environment from it is to reduce the amount of these pollutants in the air.

We can achieve this if we stop using coal as a source of energy, invest more in renewable energy sources such as wind and solar power, and minimize emissions from transportation and industry.