Answer:
  Many people, including this questioner, are worried about acid rain. So in this article, we include a brief summary of what acid rain is, its main components, its effects, and what we can do about them.

What is acid rain?
  “Acid rain” is “substances acidified by pollutants in the air precipitating from the sky” Actually there are two kinds of acid rain, wet deposition and dry deposition.

Wet deposition
  Wet deposition means acidic rain, mist, snow and so on. Acidic water sprinkles down from the sky and sinks into the soil. During this process, it exerts many influences on animals and plants.

Dry deposition
  Dry deposition means acidic air or particles. Approximately half of the acidic substances in the air return to the ground as dry deposition. Acidic particles adsorbed on walls of buildings or on trees form acidic water when they are rinsed away by rain. Acidic particles can travel over more than several hundred kilometers in the wind. For example, it is reported that polluted air from the continent of Asia might reach Japan and create acidic water there.

Main sources of acid rain
  It is thought that sulfur dioxide (SO₂) and nitrogen oxides (NOx) are the main agents causing acid rain. Acidic substances (sulfuric acid, nitric acid) are generated when these substances react with water, oxygen, etc in the air. This reaction is promoted by sunlight.

  Sulfur dioxide and nitrogen oxides are mainly generated when fossil fuels, such as petroleum, coal, or natural gas, are burned. Thus, they are generated from human activity, such as automobiles, factories, and power plants.

Effects of acid rain
Acidification and damage to lakes
  The number of fish in an acidified lake decreases drastically at below pH 5, because plankton and water plants, which are pH sensitive, are affected. At below pH 4, eggs are not hatched and the gills of adult fish are harmed. It is reported that around 4000 lakes in Ontario in Canada, near the US border, are acidified, and around 1300 lakes in Quebec, next to Ontario, are affected also.

Damage to forests
  Acid rain directly destroys the wax layer or cuticle (which protects the surface of leaves), harms stoma, and inhibits photosynthesis and respiration. Acid rain indirectly causes an alteration of the soil. Clay in soil has a property of ion exchange. Under acidic conditions, H⁺ is adsorbed on the surface of clay and Ca²⁺ etc. are eluted instead. Al³⁺ is also eluted at a lower pH. Trees lack nutrition if Ca²⁺ and Mg²⁺ are washed away. In addition, Al³⁺ is toxic. At above 0.1 ppm of Al³⁺, the ends of the roots are damaged, and cell division and growth there is prevented.

What we can do?
  What we can do individually is so small that it appears meaningless; however, remember that acid rain is the accumulation of what every single person generates in his/her daily life. Therefore, it is very important that each of us try to do something.

  First of all, let’s begin to understand the issue of acid rain and the solutions to this problem.

  Energy consumption is closely related to the issue of acid rain. Thus, reducing personal energy consumption is one of the best ways in which an individual can act.

  For example, how about trying to do the following things? 

• Turn off the power to electric appliances when they are not in use.
   

• Set room temperature at 20 Cº in winter and at 25 Cº in summer. As you leave, set the room temperature lower in winter and higher in summer.
   

• Use public transportation, bicycle, or your feet as much as possible.
   

• Purchase a low-pollution car and use it for a long time.
    

Acknowledgement
Dr. Toru Ozeki
  He is studying acid rain. He kindly allowed us to copy the section of “Effects of acid rain” from his website for this article. We would like to thank him for his kindness.
 
EPA
  There is detailed information about acid rain on this website. We referred to this website when we wrote the section of “What is acid rain?” “Main sources of acid rain“ and “What can we do?”
 
 
This article is translated by Chemistryquestion.com from the original article in Chemistryquestion.jp.  Please let us know if you find any errors.