On the problem of acid rain

Precipitation with pH less than 5.65 polluted by acidic gases in the atmosphere is called acid rain. What is acid? Pure water is neutral and tasteless; Lemonade and orange juice are sour, and vinegar is sour. They are all weak acids. Baking soda water's alkalinity is slightly astringent, while caustic soda water has astringent taste and strong alkalinity. Soda is alkali, baking soda is alkali but belongs to salt. Scientists have found that acidity is related to the concentration of hydrogen ions in aqueous solution; The alkaline taste is related to the concentration of hydroxyl ions in aqueous solution; Then an index is established: the negative value of the logarithm of hydrogen ion concentration is called pH value. So the pH value of pure water (distilled water) is 7; The greater the acidity, the lower the pH value. The greater the alkalinity, the higher the pH value. (The PH value is generally between 0- 14) The unpolluted rain and snow are neutral, and the pH value is close to 7; When it is saturated with carbon dioxide in the atmosphere, it is slightly acidic (water and carbon dioxide combine to form carbonic acid) and its pH value is 5.65. Rain with pH less than 5.65 is called acid rain; Snow with pH less than 5.65 is called sour snow; Fog that spreads at high altitude or high mountains (such as Mount Emei) is called acid fog when its pH value is less than 5.65.

Generally, several tools can be used to detect the PH value of water: litmus test solution \ phenolphthalein test solution \PH test paper (with high accuracy, which can measure PH value) \ PH meter (which can measure more accurate pH value).

What is the acid rain rate?

It can rain several times a year, some are acid rain, some are not acid rain, so generally speaking, the acid rain rate in a certain area is the number of acid rains divided by the total number of rains in the area. Its lowest value is 0%; The highest value is 100%. If there is snow, it should be regarded as rain.

Sometimes, a rainfall process may last for several days, so the acid rain rate should be based on a complete precipitation process, that is, the acid rain rate is the number of precipitation processes with acid rain in a year divided by the total number of precipitation processes in the whole year.

In addition to the annual precipitation pH value, the acid rain rate is another important indicator to judge whether an area is an acid rain area.

What is an acid rain area?

An acid rain sample collected in a certain place cannot be regarded as an acid rain area, because there may be dozens of rains a year, some of which may be acid rain, and some of which may not be acid rain, so it depends on the annual average. At present, the scientific standard of defining acid rain area in China is still under discussion, but it is generally considered that the annual average precipitation pH value is higher than 5.65 and the acid rain rate is 0-20%, which is a non-acid rain area; The pH value is between 5.30 and 5.60, and the acid rain rate is 10-40%, which is a mild acid rain area; The pH value is between 5.00 and 5.30, and the acid rain rate is 30-60%, which is a moderate acid rain area; The pH value is between 4.70 and 5.00, and the acid rain rate is 50-80%, which is a severe acid rain area; The pH value is less than 4.70, and the acid rain rate is 70- 100%, which is a severe acid rain area. This is the so-called five-level standard. In fact, there have been several acid rains in Beijing, Xining, Lanzhou, Urumqi and other places, but the average annual pH value and acid rain rate are within the standards of non-acid rain areas, belonging to non-acid rain areas.

The three major acid rain areas in China include (China acid rain is mainly sulfuric acid).

1。 Southwest acid rain area: it is a serious precipitation pollution area 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.

[Edit this paragraph] The discovery of acid rain

The modern industrial revolution, starting with the steam engine, the boiler burns coal, produces steam and drives the machine; As a result, the coal consumption of thermal power plants has increased rapidly. Unfortunately, coal contains impurity sulfur, about 1%, which will release acid gas SO2 when burning. The high temperature produced by combustion can also promote some chemical changes in the combustion-supporting air. Oxygen combines with nitrogen and releases acid gas nitrogen oxides. They were washed and dissolved by rain and snow in the sky, and the rain turned into acid rain; These acidic gases become impurities such as sulfate, nitrate and ammonium ions in rainwater. From 65438 to 0872, the British scientist Smith analyzed the composition of rainwater in Renton and found that it was acidic. The rainwater in rural areas contained ammonium carbonate, not acidic. The rainwater in the suburbs contains ammonium sulfate, which is slightly acidic; Urban rainwater contains sulfuric acid or acidic sulfate, which is acidic. So Smith put forward the proper term "acid rain" for the first time in the book Air and Rainfall: The Beginning of Chemical Climatology.

[Edit this paragraph] The causes of acid rain

The cause of acid rain is a complex atmospheric chemical and physical phenomenon. Acid rain contains many inorganic and organic acids, most of which are sulfuric acid and nitric acid. Sulfur dioxide emitted by coal combustion in industrial production and civil life, and nitrogen oxides emitted by burning oil and automobile exhaust go through the process of "rain in the clouds", that is, water vapor condenses on condensation nuclei such as sulfate and nitrate, and undergoes liquid-phase oxidation reaction to form sulfuric acid raindrops and nitric acid raindrops; It also goes through the "under-cloud scouring process", that is, the droplets containing acid rain continue to merge, adsorb and scour other droplets containing acid rain and acid gas during the falling process, forming larger raindrops and finally falling to the ground, forming acid rain. The acid rain in China is sulfuric acid rain.

Acid rain is mostly caused by the burning of fossil fuels;

(1) s → H2SO4 4s+O2 (ignition) →SO2

SO2+H2O → H2SO4 3 (sulfurous acid)

2H2SO4+O2 → 2H2SO4 (sulfuric acid)

General chemical reaction equation:

S+O2 (on fire) = SO2, 2SO2+2H2O+O2 = 2H2SO4.

(2) Nitrogen oxides are dissolved in water to form acid;

A.NO→HNO3 (nitric acid)

2NO+O2=2NO2，3NO2+H2O=2HNO3+NO

General chemical reaction equation:

4NO+2H2O+3O2=4HNO3

B.NO2→ nitric acid

General chemical reaction equation:

4NO2+2H2O+O2→4HNO3

(* Note: Numbers after elements are footnotes, and numbers before chemical formula are stoichiometry. )

[Edit this paragraph] Influencing factors of acid rain formation

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 in the atmosphere

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 sources of ammonia in the atmosphere are mainly the decomposition of organic matter and the volatilization of nitrogen fertilizer applied in farmland. 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. These two factors together, at least at present, can explain the 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 particles in China is generally high, which is several times to ten times that of foreign countries, so it 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).

[Edit this paragraph] The harm of acid rain

Sulfur and nitrogen are nutrient elements. Weakly acidic precipitation can dissolve underground minerals for plants to absorb. If the acidity is too high and the pH value drops below 5.6, it will cause serious harm. It can directly kill large areas of forests and make crops wither; It will also inhibit the decomposition of organic matter and the fixation of nitrogen in the soil, leach nutrients such as calcium, magnesium and potassium combined with soil ions, and make the soil barren; It can also acidify lakes and rivers, dissolve heavy metals in soil and water sediments into water, and poison fish; Accelerate the corrosion and weathering process of buildings and cultural relics; May endanger human health.

The impact of acid rain is most obvious in Europe and the northeastern United States, and it is widely known, but the threatened areas also include Canada, and perhaps the California Mountains, Loki Mountains and China. In some places, it is occasionally observed that the falling rain is as sour as vinegar. The influence of acid rain is a controversial topic. The harm to aquatic organisms in lakes and rivers was initially the focus of attention, but now people have realized that the harm to buildings, bridges and equipment is another costly consequence of acid rain. The impact of polluted air on human health is the most difficult to determine quantitatively.

Lakes with poor buffering capacity suffer the most. When there is a natural alkaline buffer, the acidic compounds (mainly sulfuric acid, nitric acid and a small amount of organic acids) in acid rain will be neutralized. However, lakes on granite (acidic) strata are vulnerable to direct harm, because the acid in rainwater can dissolve metal ions such as aluminum and manganese. This will reduce the growth of plants and algae, and in some lakes, it will also lead to the decrease or disappearance of fish populations. The damage caused by this form of pollution to plants ranges from harmful effects on leaves to damage to fine roots.

In the northeastern United States, the main consideration for reducing pollutants is those coal-fired power plants that burn high sulfur content. One possible remedy is chemical scrubber, which can prevent pollutants from being discharged. Chemical scrubber is a kind of equipment used to treat waste gas, or dissolve, or precipitate, or eliminate pollutants. Catalysts can reduce nitrogen oxide emissions from stationary and mobile sources, which is another example that chemistry can play a role in improving air quality.

Acid rain profit and loss statement

Analytical calculation formula

D=DH+DA+DF+DB+DC+DT

Among them,

D—— Total loss caused by air pollution

DH- Human health loss caused by air pollution.

Da- agricultural losses caused by air pollution

DF—— Forestry loss caused by air pollution.

DB—— Loss of building materials caused by air pollution

DC-air pollution increases the cleaning cost.

DT—— Traffic loss caused by acid fog that affects visibility.

1. Estimation of personnel losses caused by air pollution

DH=DHM+DMT+DHD

Among them,

DHM ---- Loss of medical expenses for respiratory diseases

DMT—— Loss of working time caused by respiratory diseases

DHD—— Loss of production caused by premature death of lung cancer patients

2. Estimation of forestry losses caused by air pollution

DA=DAV+DAG

Among them,

Loss of vegetable production caused by air pollution.

DAG—— Loss of grain production caused by air pollution

3. Estimation of forestry losses caused by air pollution

DF=DFW+DFE

In ...

DFW-Economic Loss of Wood Caused by Forest Reduction

DFE—— Economic loss of forest ecological benefits (non-forest products)

4. Estimation of loss of building materials caused by air pollution

DB=DBS+DBP

In ...

DBS—— Economic Loss of Galvanized Steel Damage

DBP- Economic Loss of Paint Damage

5. Due to the increase of air pollution, estimate the cleaning cost.

DC=DCH+DCR

In ...

DCH- Household cleaning expenses

DCR- cost of external cleaning of urban houses

6. Estimation of transportation loss caused by reduced visibility

DT=DTH+DTW

In ...

DTH-the economic loss caused by acid rain to land traffic.

DTW-the economic loss brought by acid fog to water transportation.

[Edit this paragraph] Acid rain control measures

The fundamental measure to control acid rain is to reduce the emission of sulfur dioxide and nitrogen oxides.

Governance measures

Many countries in Europe and North America, where acid rain is the most serious in the world, finally realize that the atmosphere has no national boundaries and the prevention and control of acid rain is an international environmental problem. It cannot be solved by one country alone, and countermeasures must be taken to reduce the emissions of sulfur oxides and nitrogen oxides. After many consultations, the Convention on the Control of Long-distance Transboundary Air Pollution was adopted at the meeting of environment ministers of the United Nations Economic Commission for Europe held in Geneva in June19791and came into force in June 1983. According to the convention, by the end of 1993, the contracting parties must reduce the sulfur dioxide emissions to 70% of the emissions of 1980. Thirty-two countries, including Europe and North America (including the United States and Canada), signed the Convention. In order to realize the promise, most countries have taken active measures and formulated laws and regulations to reduce the emission of acid-causing substances. For example, the acid rain law of the United States stipulates that in the area east of the Mississippi River, the emission of sulfur dioxide will be reduced from 20 million tons/year in 1983 to100000 tons/year later; The emission of sulfur dioxide in Canada decreased from 4.7 million tons/year in 1983 to 2.3 million tons/year in 1994, and so on. 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. However, the current technology is not mature enough. If it is used, it will cause new pollution and the consumption cost is high.

Acid rain is a manifestation of air pollution. Because the first thing that attracts attention is acid rain, it is customarily called acid rain.

When pure rain and snow fall, carbon dioxide in the air will dissolve into it to form carbonic acid, so it has a certain weak acidity. The concentration of carbon dioxide in the air is generally around 3 16ppm, and the pH value of precipitation can reach 5.6. This is a normal phenomenon, not what we usually call acid rain.

The acid rain we are talking about refers to the acidic precipitation whose pH value drops below 5.6 due to the influence of human activities. With the development of modern industrialization, such precipitation began to appear and increased year by year. It has begun to affect the environment on which human beings depend and human beings themselves.

The acidity of ancient rain and snow is not recorded. The measurement of Greenland ice accumulation about 180 years ago showed that the pH value of snowfall was between 6 and 7.6.

Before 1950s, the pH value of global precipitation was generally higher than 5, and acid rain appeared in a few industrial areas. Since the 1960s, with the development of industry and the increase of fossil fuel consumption, the pH value of precipitation in some industrialized areas in the world (such as southern northern Europe and eastern North America) has dropped below 5, and the scope has been continuously expanded, and the ecosystem has been obviously damaged.

1872, the English chemist Smith used the word "acid rain" for the first time in his book "Air and Rainfall: The Beginning of Chemical Climatology", pointing out that the chemical properties of precipitation are affected by factors such as coal burning and decomposition of organic matter, and acid rain is harmful to plants and substances.

In the mid-1950s, Gorham, an American aquatic ecologist, conducted a series of research work, which revealed the relationship between the acidity of precipitation and the acidity of lake water and soil, and pointed out that the acidity of precipitation was caused by sulfur dioxide emitted from fossil fuel combustion and metal smelting. However, their work has not attracted people's attention.

In 1960s, Swedish soil scientist Auden first made a comprehensive study on the relevant records of limnology, agronomy and atmospheric chemistry, and found that acidic precipitation is a large-scale phenomenon in Europe. The acidity of precipitation and surface water keeps rising, and pollutants containing sulfur and nitrogen can migrate thousands of kilometers in Europe.

1972, the Swedish government submitted a report to the United Nations Conference on the Human Environment: Cross-border Air Pollution: Impact of Atmospheric and Precipitation on the Environment. Since then, more and more countries have begun to pay attention to the problem of acid rain, and the research scale has been expanding.

1975 In May, the first international symposium on acid rain and forest ecosystem was held in Ohio State University. The International Conference on Environmental Acidification was held in Stockholm, Sweden in June 1982. Acid rain has become one of the main problems of global environmental pollution.

The formation of acid rain is a complex atmospheric chemical and physical phenomenon. Acid rain contains a variety of inorganic and organic acids, most of which are sulfuric acid and nitric acid, and sulfuric acid is the main one. Sulfuric acid and nitric acid are converted from sulfur dioxide and nitrogen oxides emitted by people, which can be discharged locally or migrated from far away places.

Industrial activities such as coal and oil combustion and metal smelting will release sulfur dioxide into the air and generate sulfuric acid through gas phase or liquid phase oxidation reaction. At the same time, high-temperature combustion will make nitrogen and oxygen in the air generate nitric oxide, which will continue to react with oxygen in the atmosphere, most of which will be converted into nitrogen dioxide, and will generate nitric acid and nitrous acid when it meets water or steam.

Due to human activities and natural processes, many gaseous or solid substances still enter the atmosphere, which also has an impact on the formation of acid rain. Iron, copper and magnesium in atmospheric particles are catalysts for acid formation. Ozone and hydrogen peroxide produced by atmospheric photochemical reaction are oxidants of sulfur dioxide; Calcium oxide in fly ash, calcium carbonate in soil, ammonia from natural and man-made sources, and other alkaline substances will react with acids to neutralize them.

The acidity of precipitation is actually the dry balance of main anions and cations in precipitation. When the concentration of sulfur dioxide and nitric oxide in the atmosphere is high, the precipitation will be acidic; If the concentration of several main cation carriers representing alkaline substances in precipitation is also high, precipitation will not be very acidic, and may even be alkaline. This usually happens in alkaline soil areas or when the concentration of particulate matter in the atmosphere is high. On the contrary, even if the concentrations of sulfur dioxide and nitric oxide in the atmosphere are not high and there are relatively few alkaline substances, the precipitation will still have a high acidity. The tall chimneys in industrial areas can spread sulfur dioxide far away, so acid rain also falls in many mountainous and wilderness areas.

Sulfur and nitrogen are indispensable nutrients for plant growth, and weakly acidic precipitation can dissolve minerals in the earth's crust for absorption by animals and plants. But if the acidity is too high, for example, the pH value drops below 5, it may destroy the ecosystem.

In areas with low saturation of soil foundation or rock areas with thin soil layer, acidic rainwater will not be neutralized after falling to the ground, which will acidify soil, lakes and rivers.

When the pH value of lake water or river water drops below 5, metals (such as aluminum) in soil and water sediments in the basin will dissolve into the water, poisoning fish and seriously affecting their reproduction and development. Acidification of water will also lead to changes in the composition and structure of aquatic organisms, with an increase in acid-tolerant algae and fungi, while a decrease in rooted plants, bacteria and invertebrates, and a decrease in the decomposition rate of organic matter. As a result, there are fewer fish in acidified lakes and rivers. Many lakes in Sweden, southern Norway and the northeastern United States have become dead lakes without fish.

For example, in the Adirondack Mountains in the eastern United States, more than half of the lakes above 700 meters above sea level have pH below 5, and 90% have no fish. During the period of 1929 ~ 1937, only 4% of the lakes had a pH below 5 or no fish. At present, more than 18000 large and medium-sized lakes in Sweden have been acidified, of which about 4000 are seriously acidified, which has caused great harm to aquatic organisms.

Acid rain can also inhibit the decomposition and nitrogen fixation of organic matter in soil, leach nutrients such as calcium, magnesium and potassium combined with soil particles, and make the soil barren.

Acid rain will harm the new buds and leaves of plants, thus affecting their development and growth; Acid rain corrodes building materials, metal structures, paints, etc. And ancient buildings and sculptures will also be destroyed; After acidification of lakes and groundwater as water sources, the dissolution of metals will have harmful effects on the health of drinkers.

The fundamental measure to control acid rain is to reduce the artificial emission of sulfur dioxide and nitric oxide. In addition, Sweden and other countries have tried to apply alkaline lime in acidified soil and water, and achieved good results in a short time.

How to reduce acid rain?

Acid rain is one of the most obvious air quality problems we are facing today. When fossil fuels are burned to generate electricity and provide transportation, acidic substances and compounds that lead to the formation of acidic substances are produced. These substances are mainly acids derived from sulfur oxides and nitrogen oxides. These compounds also have some natural sources, such as lightning, volcanoes, biomass burning and microbial activities, but these natural sources are quite small compared with the exhaust gas of automobiles, power plants and smelters except for rare volcanic eruptions.

Various strategic measures to reduce acid rain may require billions of dollars of investment every year. Because the cost is so huge, it is very important to understand the atmospheric processes involving pollutant migration, chemical transformation and destination.

Acid deposition consists of two parts, namely "wet" deposition (such as rain and snow) and dry deposition (aerosol or gaseous acid compounds deposited on the surfaces of soil particles and plant leaves). The substances that eventually settle down usually enter the atmosphere in a very different chemical form. For example, sulfur in coal is oxidized to sulfur dioxide, which is a gaseous form discharged from a chimney. As it moves in the atmosphere, it will slowly oxidize and react with water to produce sulfuric acid-a form that may be deposited hundreds of miles downwind.

The formation, reaction and final removal of nitrogen oxides from the atmosphere are also very complicated. When nitrogen and oxygen are heated at high temperature in power plants, civil stoves and automobile engines, they will produce nitric oxide (NO), which will react with oxidants to produce nitrogen dioxide (NO2) and finally nitric acid (HNO3). The global statistics of nitrogen oxides-the quantitative estimation of where they come from and where they go is still quite uncertain.

It is easy to see that it is difficult to choose air pollution control strategies with confidence until we thoroughly understand the biogeochemical cycles of different chemical forms of nitrogen, sulfur and carbon and the global sources and destinations of these chemical species. Atmospheric chemistry and environmental chemistry are the core to realize a cleaner and healthier environment. Developing reliable methods for determining trace chemical species in the air, important atmospheric reaction kinetics, and finding new and more effective chemical processes that can be used to reduce pollutant emissions are the goals that the country must promise in the next 10 year.

[Edit this paragraph] Biological control of acid rain

In the report "Life Characteristics of 1994" published by Worldwatch Research not long ago, it is said: Generally speaking, the situation of the earth is not very good. Of all the indicators to measure the health of the earth, we have only succeeded in reversing the deterioration of one indicator-the reduction of freon that makes the ozone layer empty. Carbon emissions have not decreased, and air pollution has become increasingly serious. According to statistics, human beings discharge SO2 1. 15 tons into the atmosphere every year, and NO2 is about 50 1.2 million tons. About half of the world's urban population lives in the atmospheric environment where SO2 exceeds the standard, and 654.38 billion people live in the environment where particulate matter exceeds the standard. Air pollution has become a hidden killer. Sulfur dioxide is the culprit. Recently, 26 European countries and Canada signed a new agreement proposed by the United Nations Economic Commission for Europe, and the United States also promised to reduce SO2 emissions by 87% by 20 10. European countries and Canada praised the new agreement as a milestone in preventing and controlling air pollution. SO2 not only pollutes the air and harms human health, but also is the main substance that forms acid rain. SO2 and NO2 in the atmosphere are dissolved in rainwater under the action of oxidants. When the pH value of rain, freezing rain, snow, hail and other precipitation is less than 5.6, it is acid rain. According to the determination of relevant departments in the United States, sulfuric acid accounts for 60%, nitric acid accounts for 33%, hydrochloric acid accounts for 6%, and the rest is carbonic acid and a small amount of organic acids.

Acid rain has brought serious influence and destruction to the earth's ecological environment and human social economy. Acid rain acidifies soil and reduces soil fertility. Many toxic substances are absorbed by the root system, poisoning the root system, killing root hairs, making plants unable to absorb water and nutrients from the soil and inhibiting the growth and development of plants. Acid rain acidifies rivers and lakes, inhibits the growth and reproduction of aquatic organisms, and even causes the fry to suffocate and die; Acid rain also kills plankton in the water, reduces the food source of fish, and makes the aquatic ecosystem disorder; Acid rain pollutes rivers, lakes and groundwater, directly or indirectly endangering human health. Acid rain directly damages plant surfaces (leaves and stems) or indirectly damages soil, leading to forest decline. Acid rain can also cause pests and diseases, leading to large-scale forest death. Europe emits 22 million tons of sulfur every year, destroying large areas of forests. More than 654.38 million hectares of forests in Sichuan, Guangxi and other provinces are on the verge of death. Acid rain has a strong corrosive effect on metal, stone, wood, cement and other building materials. Many ancient buildings and stone carvings in the world have been destroyed by acid rain, such as the Canadian Parliament Building and the Leshan Giant Buddha in China. Acid rain also directly harms electric wires, rails, bridges and houses.

At present, there are three major acid rain areas in the world. One is the Nordic acid rain area centered on Germany, France, Britain and other countries, involving more than half of Europe. Second, acid rain areas in North America, including the United States and Canada, were formed in the late 1950s. The total area of these two acid rain areas is more than 654.38+million square kilometers, and the pH value of precipitation is less than 5.0, and some are even less than 4.0. The acid rain area formed in China in the mid-1970s covering Sichuan, Guizhou, Guangdong, Guangxi, Hunan, Hubei, Jiangxi, Zhejiang, Jiangsu and Qingdao is the third largest acid rain area in the world. Although the area of acid rain area in China is small, its rapid development and expansion and high acidification rate of precipitation are rare in the world. Because air pollution has no national boundaries, acid rain is a global disaster.

The harm of acid rain has attracted worldwide attention. The United Nations has held many international conferences to discuss the problem of acid rain. Many countries list acid rain control as a major scientific research project. More than 40 countries in the world have restricted automobile emissions through pollution. At the "International Cooperation Conference on the Application of Environment-friendly Biotechnology" held in India from 65438 to 0993, 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. Experts believe that there is great potential to harness the environment by biotechnology. Coal is one of the most important energy sources at present, but it contains sulfur and emits harmful gases such as SO2 when burning. There are two kinds of sulfur in coal: inorganic sulfur and organic sulfur. Most inorganic sulfur exists in mineral form, and pyrite (FeS2) is the main one. Biologists use microbial desulfurization to change ferrous iron into trivalent iron, and monomer sulfur into sulfuric acid, which has achieved good results. For example, Japan's Central Electric Power Research Institute isolated a thiobacillus from soil, which is an iron-oxidizing bacterium that can effectively remove inorganic sulfur from coal. A new microbial strain has been screened by the American Natural Gas Research Institute, which can separate organic sulfur from coal without reducing the quality of coal. An acid-hot sulfur bacterium was screened from Czech Republic, which can remove 75% sulfur from pyrite. According to the statistics of 199 1 year, the Czech Republic removed 78.5% of inorganic sulfur and 23.4% of organic sulfur from coal by biotechnology. At present, scientists have found that Thiobacillus ferrooxidans and Thiobacillus thiooxidans can remove sulfur from pyrite. 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.

[Edit this paragraph] The black humor of acid rain

pickled vegetables

After acid rain acidified the soil, it further acidified the groundwater. A housewife in the Black Triangle area where Germany, Poland and the former Czech Republic meet (the area is famous for its forests first, and then for its destruction by acid rain) said, "There are only a few wells in our area to drink. We ourselves often joke that as long as we soak the vegetables in the well, we can make good kimchi (ester axillary vegetables). "