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Acid rain

Normal rain has a slightly acidic value, a pH between 5 and 5.5. But if rainwater reacts with some pollutants (mainly sulfur and nitrogen oxides) from the burning of fossil fuels, it produces sulfuric acid and nitrous and nitric acids. Then the rain becomes much more acidic, reaching a pH value of 4.

SO3 + H2O → H2SO4

2NO2 + H2O → HNO3 + HNO2

Although acid precipitation is usually liquid, it can also be solid, in the form of ice or snow.
The acid rain is a regional or cross - border problem. Pollutants are generated in one region and acid precipitation can occur in an area not too far to where the pollutants have been blown by winds.

Effects of acid rain

Although acid rain does not cause direct damage to people's health, it does cause other significant damage that affects people. Acid rain damages ecosystems, since it acts:

Over the waters

When the rain falls on the waters, or by runoff, the acidity damages the most sensitive aquatic organisms, which gradually disappear.

About the vegetation

The acidity of the water damages the leaves of the plants, which turn yellow and fall, causing the death of the plant. In addition to the vegetables, the fauna of the area is also affected.

La lluvia ácida perjudica a la vegetación.

By Lovecz (Own work) [Public domain], via Wikimedia Commons

On the soils

The soils are acidified and chemical reactions that take place in it are altered. Acidity causes heavy metals to dissolve and nutrients decrease , which is why it is a risk to the life of vegetables and microorganisms.

About human constructions

Acid rain can also corrode some urban materials, such as metals or building materials, as in the case of stone disease, which causes some old buildings and monuments to be affected by this type of pollution, especially those made with limestone rocks.

Acid rain solutions

Some of the measures that can be taken to reduce the effects of acid rain are:

  • Reduce the use of fossil fuels, especially those with high sulfur content, and promote other less polluting ones.
  • Use of filters to trap pollutants at emission points.
  • Promote the use of clean, non-polluting energy.

Answer in your notebook

9.2.- What is acid rain?


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