Acid rain has been cited as an environmental problem since the 1970s. Acid rain is caused by nitrogen oxides and sulfur oxides contained in exhaust gas from factories, power plants, and automobiles. The emitted nitrogen oxides and sulfur oxides spread into the atmosphere, dissolve in rain, and become nitric acid and sulfuric acid, making the rain acidic. When the maximum amount of carbon dioxide in the air dissolves, the pH of rain drops to 5.6. Therefore, if the pH of rain is lower than 5.6, it is considered acid rain. Currently, acid rain is falling in almost all areas of Japan. In the case of the United States, acid rain occurs from the east coast to the central region. In Europe, acid rain occurs in many countries, including Germany. In the 1970s, trees in Germany's Black Forest died. At that time, it was concluded that acid rain was the cause of the trees dying.
Countries other than Germany, on the other hand, were skeptical about the effects of acid rain. For example, in Japan, there was a theory that ``the death of trees is caused not by acid rain, but by photochemical oxidants.'' At the time, Japanese researchers denied the effects of acid rain on the basis that there was no effect even if acidic water was poured on plants. The main component of photochemical oxidants is ozone. Ozone can irritate the eyes and throat, causing symptoms such as stinging eyes and a sore throat. On the other hand, it is said to have an effect on plants, such as by inhibiting photosynthesis. Subsequent research has revealed that ozone has a large effect on agricultural crops such as spinach, but has little effect on trees. The video provides a detailed explanation of the known effects of acid rain.
Acid rain only shows its effects after a long period of time.
When acid rain falls on the ground, the pH of the soil decreases. However, the soil's pH, which begins to drop, returns to its original level due to the buffering power of the soil. Thanks to this buffering power, the effects of acid rain will not occur immediately. However, if acid rain continues to fall, the soil's buffering capacity will be lost. As a result, it takes a long time for the soil to become acidic. When soil becomes acidic, aluminum ions are leached from soil minerals. The harmful effects of aluminum ions on living things can be said to be the damage caused by acid rain. Unlike environmental destruction that immediately affects ecosystems, the effects of acid rain only appear after years or decades. Acid rain is caused by exhaust gases closely related to industry and daily life. It is unlikely that the pH of rain will increase and acid rain will be eliminated.
Negative effects of aluminum ions
Many studies have been conducted on the negative effects of aluminum ions. In plants, aluminum ions have been found to inhibit root elongation. When roots stop elongating, they can no longer absorb water and nutrients, and the plant dies. In addition, phosphoric acid, which is necessary for plant growth, is bound to aluminum ions and becomes unavailable.
The toxicity of aluminum ions is not only shown to plants. When aluminum ions dissolve from the soil and flow into ponds and lakes, they have a negative impact on living creatures. Aluminum ions in particular have a deadly effect on fish. The mass death of fish in ponds and lakes, which is sometimes reported, is thought to be caused by aluminum ions.
Acid rain will suppress plant growth globally
Acid rain has a very wide range of effects. Therefore, it affects many forests, grasslands, and cultivated lands. Trees and other plants absorb carbon dioxide, a greenhouse gas, and are necessary to prevent global warming. If total plant biomass were to decrease, the amount of carbon dioxide absorbed would decrease, accelerating global warming. Furthermore, acid rain not only causes global warming, but also causes crop failures around the world, potentially increasing food problems. The causes of each environmental problem are different, but each of them can interfere with each other and amplify the problem. Acid rain may become a major problem in the future.
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