What's the pH level of natural rain compared to acid rain?

Natural rain has a pH level of approximately 5.6, while acid rain generally has a pH level below 5.0.

Natural rain is slightly acidic due to the presence of carbon dioxide in the atmosphere. When carbon dioxide dissolves in rainwater, it forms a weak carbonic acid, resulting in a pH level of around 5.6. This is considered normal and does not pose any significant environmental threats. However, it's important to note that pH levels can vary slightly depending on the concentration of carbon dioxide and other naturally occurring substances in the atmosphere.

Acid rain, on the other hand, is a more severe form of acidic precipitation. It is primarily caused by human activities, particularly the burning of fossil fuels. This process releases sulphur dioxide and nitrogen oxides into the atmosphere, which react with water, oxygen, and other chemicals to form sulphuric and nitric acids. These acids are much stronger than carbonic acid, leading to a lower pH level, typically below 5.0.

The pH scale is logarithmic, meaning that each unit represents a tenfold difference. Therefore, rain with a pH of 4.0 is ten times more acidic than natural rain with a pH of 5.0. This increased acidity can have harmful effects on the environment, including damage to forests and aquatic ecosystems.

Acid rain can also affect human health indirectly by contaminating drinking water and damaging crops. Moreover, it can cause the deterioration of buildings and monuments, particularly those made of limestone and marble, which react with the acids.

In conclusion, while natural rain is slightly acidic due to the presence of carbon dioxide, acid rain is significantly more acidic due to the release of sulphur dioxide and nitrogen oxides from human activities. This increased acidity can have harmful effects on both the environment and human health.