How Acid Rain Is Produced
What is acid rain?
Acid rain is one result of polluting gas emissions. This precipitation, which has a pH of less than 5, occurs primarily in highly industrialized areas with a high degree of pollution; however, they can also fall on land, seas, or lakes far from their place of origin.
The phenomenon of acid rain can be summarized in four steps:
- Compounds like sulfur dioxide and nitrogen oxides are produced by anthropogenic sources (mainly burning fossil fuels) or natural sources (volcanic emissions).
- These gases rise into the atmosphere, where they mix and react with water vapor, oxygen, and other chemical substances, leading to the creation of acids.
- Acids like sulfuric and nitric acids dissolve easily in small particles of water. This way, they’re carried by the wind to very distant places.
- Acid precipitation (rain, fog, snow, or sediment) falls over vast expanses, impacting the environment.
What agents are the precursors of acid rain?
The precursor compounds of acid rain are primarily sulfur oxides (SO2) and nitrogen oxides (NOx); however, substances like chlorine, ammonia, volatile organic compounds (VOCs), and others also play a role in this phenomenon.
When they rise to the atmosphere, these agents are oxidized and hydrolyzed, producing strong acids like sulfuric acid and nitric acid.
Sulfur dioxide and sulfuric acid:
Sulfuric acid is a very reactive, highly corrosive compound that can cause chemical burns on contact with skin, blindness on contact with the eyes, or breathing problems when inhaled. Sulfur dioxide is generated by burning fossil fuels such as coal. Then, it becomes sulfuric acid as it rises to the atmosphere.
Though the amounts of sulfuric acid in acid rain are minimal, frequent acid precipitation can cause serious environmental problems, such as soil demineralization, the concentration of heavy metals, and acidification of water, and it may even lead to a significant public health risk.
China is currently the world’s top emitter of sulfur dioxide since it’s the world’s leading producer and consumer of coal. As a result, more than 50% of Chinese cities show signs of acid rain.
Nitrogen oxide and nitric acid:
Nitric oxide (NO) and nitrogen dioxide (NO2) come from nitrogen in the air and are significant air pollutants. They form because of the high temperatures of combustion that break down and oxidize nitrogen.
NO has a greater presence in the emissions, but in the presence of atmospheric oxygen, it quickly transforms into NO2.
Nitrogen oxides are acidic, and they can form nitric acid, HNO3, which can dissolve in water, giving rise to acid rain.
What can be done to prevent the production of acid rain?
The main step that can be taken to prevent the production of acid rain is the worldwide implementation of regulations and recommendations on the maximum emission levels of its precursor compounds (sulfur oxides and nitrogen oxides). These maximum levels must account for the effect of oxides on flora and fauna, as well as the public health risk.