The causes and harm of acid rain are briefly described, and the prevention measures are put forward.

Cause: Acid rain is caused by acid gas pollution in the atmosphere, and acid precipitation with pH less than 5.65 is called acid rain. Acid rain is mainly caused by man-made release of a large number of acidic substances into the atmosphere. Acid rain in China is mainly caused by burning a lot of coal with high sulfur content. In addition, the tail gas emitted by various motor vehicles is also an important cause of acid rain.

Hazard:?

(1) Harm to aquatic system will affect fish and other biological communities, change the circulation of nutrients and toxic substances, make toxic metals dissolve in water and enter the food chain, and reduce species and productivity.

(2) The damage to terrestrial ecosystem is mainly manifested in soil and plants. Effects on soil include inhibiting decomposition of organic matter and nitrogen fixation, filtering out nutrients such as calcium, magnesium and potassium, and making soil barren. For plants, acid rain damages new leaf buds, affects their growth and development, and leads to the degradation of forest ecosystem.

(3) Effects on human body. First, heavy metals such as mercury and lead enter the human body through the food chain, causing cancer and Alzheimer's disease; Second, acid mist invades the lungs, inducing pulmonary edema or leading to death; Third, living in an environment containing acid deposits for a long time will induce too much oxidized fat, which will increase the probability of diseases such as arteriosclerosis and myocardial infarction.

(4) Corrosion of buildings, machinery and municipal facilities.

Preventive and control measures:

1, raw coal desulfurization technology can remove about 40%-60% inorganic sulfur from coal.

2. Give priority to the use of low-sulfur fuels, such as low-sulfur coal and low-sulfur natural gas.

3. Improve coal burning technology to reduce the emission of sulfur dioxide and nitrogen oxides during coal burning. For example, liquid coal combustion technology is one of the new technologies welcomed by all countries. Limestone and dolomite are mainly used to react with sulfur dioxide, and the generated calcium sulfate is discharged with ash.

4. The flue gas formed after coal combustion is desulfurized before being discharged into the atmosphere. At present, lime method is mainly used to remove 85%-90% of sulfur dioxide gas from flue gas. However, although the desulfurization effect is good, it is very expensive. For example, the cost of installing flue gas desulfurization devices in thermal power plants is as high as 25% of the total investment of power plants. This is also one of the main difficulties in controlling acid rain.

5. Develop new energy sources, such as solar energy, wind energy, nuclear energy and combustible ice. However, the current technology is not mature enough. If it is used, it will cause new pollution and the consumption cost is high.

Extended data:

Most of the sulfur and nitrogen oxides in the atmosphere are caused by human activities, among which sulfur dioxide and nitrogen oxides produced by burning fossil fuels (coal, oil and natural gas) are the main causes of acid rain.

Natural pollution sources: Volcanic eruptions, earthquakes and other natural phenomena release a large number of acidic gases.

Man-made pollution sources: industrial and mining enterprises, vehicles and domestic stoves burn coal, oil and natural gas, and emit acid gas into the atmosphere, while non-ferrous metallurgy industries emit acid gas.

Acid rain in China is mainly sulfuric acid type, and the three major acid rain areas in China are:

1. southwest acid rain area: it is the area with serious precipitation pollution second only to central China acid rain area.

2. Central China Acid Rain Area: At present, it has become the largest acid rain pollution area with the highest central intensity in China.

3. East China coastal acid rain area: The pollution intensity is lower than that in Central China and Southwest China.

The three major acid rain areas in the world are: Western Europe, North America and Southeast Asia.

At present, the main measures to reduce sulfur dioxide emissions in the world are:

1. Raw coal desulfurization technology can remove about 40%-60% inorganic sulfur from coal.

2. Give priority to the use of low-sulfur fuels, such as low-sulfur coal and low-sulfur natural gas.

3. Improve coal burning technology to reduce the emission of sulfur dioxide and nitrogen oxides during coal burning. For example, liquid coal combustion technology is one of the new technologies welcomed by all countries. Limestone and dolomite are mainly used to react with sulfur dioxide, and the generated calcium sulfate is discharged with ash.

4. The flue gas formed after coal combustion is desulfurized before being discharged into the atmosphere. At present, lime method is mainly used to remove 85%-90% of sulfur dioxide gas from flue gas. However, although the desulfurization effect is good, it is very expensive. For example, the cost of installing flue gas desulfurization devices in thermal power plants is as high as 25% of the total investment of power plants. This is also one of the main difficulties in controlling acid rain.

5. Develop new energy sources, such as solar energy, wind energy, nuclear energy and combustible ice.

6. Biological control: 1993 At the "International Cooperation Conference on the Application of Environmental Friendly Biotechnology" held in India, experts put forward measures to prevent, stop and reverse environmental degradation by biotechnology, enhance the sustainable development and application of natural resources, and maintain environmental integrity and ecological balance.

At present, scientists have found that the microorganisms that can remove sulfur from pyrite are Thiobacillus ferrooxidans and Thiobacillus thiooxidans. A new technology recently developed by Electric Power Central Research Institute, a Japanese consortium, can remove 70% of inorganic sulfur and reduce 60% of dust.

This technology is simple in principle and cheap in equipment, especially suitable for developing countries that can't afford expensive desulfurization equipment. Biotechnology desulfurization conforms to the principles of "source treatment" and "clean production", and it is a promising treatment method, which has been paid more and more attention by countries all over the world.

Influencing factors of acidity

1. Discharge and transformation conditions of acidic pollutants. Generally speaking, the more serious SO2 pollution in a certain place, the higher the concentration of sulfate ion in precipitation, which leads to the lower ph value. ?

2. Ammonia (NH3) in the atmosphere is very important for the formation of acid rain. Ammonia is the only common gaseous alkali in the atmosphere. Because of its water solubility, it can react with acid aerosol or acid in rain to neutralize and reduce acidity. The volatilization of ammonia in soil increases with the increase of soil pH value.

The soil pH value in Beijing and Tianjin is above 7~8, while that in Chongqing and Guiyang is generally 5~6, which is one of the important reasons why the atmospheric ammonia level is high in the north and low in the south. Where the soil is acidic, the buffering capacity of sandstorm dust is low. Together, these two factors can at least explain the current distribution of acid rain in southern China.

3. Acidity of particulate matter and its buffering capacity?

In addition to acid gases SO2 and NO2, there is also an important member of air pollutants-particulate matter. The sources of particulate matter are very complicated. There are mainly coal dust and sandstorms. The latter accounts for about half in the north and about one third in the south.

Particulate matter has two effects on the formation of acid rain. Firstly, the catalytic metal contained in it promotes the oxidation of SO2 into acid; The second is to neutralize the acid. However, if the particulate matter itself is acidic, it will not play a role in neutralization and will become one of the sources of acid. At present, the concentration level of atmospheric particulate matter in China is generally high, which can not be ignored in the study of acid rain.

4. Influence of weather situation

If meteorological conditions and topography are conducive to the diffusion of pollutants, the concentration of pollutants in the atmosphere will be reduced and acid rain will be weakened, otherwise it will be enhanced (such as inversion).

References:

Baidu encyclopedia-acid rain