Acid rain causes and consequences briefly. Important facts about acid rain

The term “acid rain” was introduced by the English chemist R.E. Smith more than 100 years ago.

In 1911, cases of fish death as a result of acidification were recorded in Norway natural water. However, it was only in the late 60s, when similar cases in Sweden, Canada, and the United States attracted public attention, that the suspicion arose that the cause was rain with a high content of sulfuric acid.

Acid rain is precipitation(rain, snow) with a pH less than 5.6 (high acidity).

Acid rain is formed due to industrial emissions of sulfur dioxide and nitrogen oxides into the atmosphere, which, when combined with atmospheric moisture, form sulfur and nitric acid. As a result, rain and snow become acidified (pH number below 5.6). In Bavaria (Germany), in August 1981, rain fell with an acidity pH = 3.5. Maximum recorded precipitation acidity in Western Europe- pH = 2.3.

The total global anthropogenic emissions of sulfur and nitrogen oxides annually amount to more than 255 million tons (1994). Acid-forming gases remain in the atmosphere for a long time and can travel over distances of hundreds and even thousands of kilometers. Thus, a significant portion of UK emissions ends up in Nordic countries(Sweden, Norway, etc.), i.e. with cross-border transport, and harms their economies.

To solve the problem of acid rain, it is necessary to reduce emissions of sulfur dioxide and nitrogen oxide into the atmosphere. This can be achieved by several methods, including by reducing the energy received by humans by burning fossil fuels and increasing the number of power plants that use alternative energy sources (sunlight, wind, tidal energy). Other opportunities to reduce emissions of pollutants into the atmosphere are:

• 1. Reducing sulfur content in various types of fuel. The most acceptable solution would be to use only those fuels that contain minimum quantities sulfur compounds. However, there are very few such types of fuel. Only 20% of the world's oil reserves have a sulfur content of less than 0.5%. And in the future, unfortunately, the sulfur content in the fuel used will increase, since oil with low sulfur content is produced at an accelerated pace. The same is true with fossil coals. Removing sulfur from fuel turned out to be a very expensive process in financial terms; moreover, it is possible to remove no more than 50% of sulfur compounds from the fuel, which is an insufficient amount.
• 2. Application of tall pipes. This method does not reduce the environmental impact, but increases the efficiency of mixing pollutants in higher layers of the atmosphere, which leads to deposition acid precipitation in more remote areas from the source of pollution. This method reduces the impact of pollution on local ecosystems, but increases the risk of acid rain in more remote regions.
• 3. Technological changes. The amount of nitrogen oxides NO that is formed during combustion depends on the combustion temperature. In the course of the experiments, it was possible to establish that what lower temperature combustion, the less nitrogen oxide is produced, and the amount of NO depends on the time the fuel is in the combustion zone with excess air.

Reductions in sulfur dioxide emissions can be obtained by cleaning the end gases from sulfur. The most common method is the wet process, where the resulting gases are bubbled through a limestone solution, resulting in the formation of sulfite and calcium sulfate. In this way it is possible to remove from the final gases greatest number sulfur.

4. Liming. To reduce acidification of lakes and soils, alkaline substances (CaCO 3) are added to them. This operation is very often used in Scandinavian countries, where lime is sprayed from helicopters onto the soil or onto the catchment area. The Scandinavian countries suffer the most in terms of acid rain, since most Scandinavian lakes have granite or limestone-poor beds. Such lakes have a much lower ability to neutralize acids than lakes located in areas rich in limestone. But along with the advantages, liming also has its own number of disadvantages:

In flowing and rapidly mixing lake water, neutralization does not occur effectively;

There is a gross violation of the chemical and biological balance of water and soil;

It is not possible to eliminate all the harmful effects of acidification;

Liming cannot remove heavy metals. During a decrease in acidity, these metals pass into poorly soluble compounds and precipitate, but when a new portion of acid is added, they dissolve again, thus representing a constant potential danger for lakes.

It should be noted that a method has not yet been developed that, when burning fossil fuels, will reduce emissions of sulfur dioxide and nitrogen to a minimum, and in some cases completely prevent it.

Atmospheric pollution with compounds of sulfuric and nitric acids followed by precipitation is called acidicrains. Acid rain is formed as a result of the release of sulfur and nitrogen oxides into the atmosphere by enterprises of the fuel and energy complex, motor vehicles, as well as chemical and metallurgical plants. When analyzing the composition of acid rain, the main attention is paid to the content of hydrogen cations, which determine its acidity (pH). For clean water pH = 7, which corresponds to a neutral reaction. Solutions with a pH below 7 are acidic, above - alkaline. The entire acidity-alkalinity range is covered by pH values ​​from 0 to 14.

About two-thirds of acid rain is caused by sulfur dioxide. The remaining third is caused mainly by nitrogen oxides, which also serve as one of the causes of the greenhouse effect and are part of urban smog.

Industry in different countries annually emits more than 120 million tons of sulfur dioxide into the atmosphere, which, reacting with atmospheric moisture, turns into sulfuric acid. Once released into the atmosphere, these pollutants can be carried by the wind thousands of kilometers from their source and return to the ground in rain, snow or fog. They turn lakes, rivers and ponds into “dead” bodies of water, destroying almost all living things in them - from fish to microorganisms and vegetation, destroying forests, destroying buildings and architectural monuments. Many animals and plants cannot survive in highly acidic conditions. Acid rain not only causes acidification of surface waters and upper soil horizons, but also spreads with downward flows of water throughout the entire soil profile and causes significant acidification of groundwater.

Sulfur is found in minerals such as coal, oil, copper and iron ores, while some of them are used as fuel, while others are processed in the chemical and metallurgical industries. During processing, sulfur is converted into various chemical compounds, among which sulfur dioxide and sulfates predominate. The resulting compounds are partially captured by treatment devices, and the rest is released into the atmosphere.

Sulfates are formed during the combustion of liquid fuels and during industrial processes such as oil refining, the production of cement and gypsum, and sulfuric acid. When burning liquid fuels, about 16% of the total amount of sulfates is formed.

Although acid rain does not create such global problems as global warming climate change and ozone depletion, their impact extends far beyond the country producing the pollution.

Acid rain and ponds. As a rule, the pH of most rivers and lakes is 6...8, but with a high content of mineral and organic acids in their waters, the pH is much lower. The process of acid rain entering water bodies (rivers, ponds, lakes and reservoirs) includes many stages, at each of which their pH can decrease or increase. For example, changes in the pH of sediments are possible when they move along the forest floor, interacting with minerals and products of microorganisms.

All living things are sensitive to changes in pH, so increasing the acidity of water bodies causes irreparable harm to fish stocks. In Canada, for example, due to frequent acid rain, more than 4 thousand lakes have been declared dead, and another 12 thousand are on the verge of death. The biological balance of 18 thousand lakes in Sweden has been disrupted. Fish have disappeared from half the lakes in southern Norway.

Due to the death of phytoplankton sunlight penetrates to a greater depth than usual. Therefore, all the lakes that died from acid rain are strikingly transparent and unusually blue.

Acid rain and forests. Acid rain causes enormous damage to forests, gardens, and parks. Leaves fall, young shoots become as fragile as glass and die. Trees become more susceptible to diseases and pests, and up to 50% of their root system dies, mainly the small roots that feed the tree. In Germany, acid rain has already destroyed almost a third of all spruce trees. In forested areas such as Bavaria and Baden, up to half of the forest land was damaged. Acid rain causes damage not only to forests located on the plains; a number of damages have been recorded in the high-mountain forests of Switzerland, Austria, and Italy.

Acid rain and agricultural yieldstour. It has been established that the consequences of exposure to acid rain on agricultural crops are determined not only by their acidity and cationic composition, but also by duration and air temperature. In general, it has been established that the dependence of the growth and maturation of agricultural crops on the acidity of precipitation indicates the relationship between plant physiology, the development of microorganisms and a number of other factors. It is therefore obvious that a quantitative accounting of all components of acid rain that affect the yield and quality of products, as well as the complex processes of the functioning of soil biota for each specific region, is necessary.

Acid rain and materials. The impact of acid rain on a wide range of structural materials is becoming more and more obvious from year to year. Thus, accelerated corrosion of metals under the influence of acid precipitation, as noted by the American press, leads to the destruction of aircraft and bridges in the United States. As is known, the preservation of ancient monuments in Greece and Italy has become a serious problem. The main damaging ingredients are hydrogen cation, sulfur dioxide, nitrogen oxides, as well as ozone, formaldehyde and hydrogen peroxide.

The intensity of destruction of materials depends on: their porosity, since the higher the specific surface area, the greater its sorption capacity; from design features, since in the presence of various recesses they are collectors of acid precipitation; on operating conditions: wind speed, temperature, air humidity, etc.

In practice, the greatest attention is paid to three groups of materials: metals - stainless steel and galvanized iron; from building materials - materials for external structures of buildings; from protective - paints, varnishes and polymers for surface coatings. When exposed to precipitation and gases, their damaging effect is determined by the intensity of catalytic reactions involving metals, as well as synergism (synergy is the ability of one substance to enhance the effect of another), with uniform corrosion most often observed.

According to the European Parliament, the economic damage from acid rain amounts to 4% of the gross national product. This must be taken into account when choosing a strategy to combat acid rain in the long term.

Specific measures to reduce sulfur emissions into the atmosphere are being implemented in two directions:

use of coal with low sulfur content at thermal power plants;

emissions cleaning.

Low-sulfur coals are considered to have a sulfur content of less than 1%, and high-sulfur coals are those with a sulfur content of more than 3%. To reduce the likelihood of acid rain, high-sulfur coals are pre-treated. Coal usually contains pyrite and organic sulfur. Modern multi-stage methods of coal purification make it possible to extract up to 90% of all pyrite sulfur from it, i.e. up to 65% of its total quantity. To remove organic sulfur, chemical and microbiological treatment methods are currently being developed.

Similar methods must be applied to high-sulfur oil. World reserves of oil with low sulfur content (up to 1%) are small and amount to no more than 15%.

When burning fuel oil with a high sulfur content, special chemical additives are used to reduce the content of sulfur dioxide in emissions.

One of the simplest ways to reduce the amount of nitrogen oxides during fuel combustion is to carry out the process in conditions of a lack of oxygen, which is ensured by the speed of air supply to the combustion zone. Japan has developed a technology for “afterburning” primary combustion products. In this case, first the fuel (oil, gas) is burned in an optimal mode to form nitrogen oxides, and then the unreacted fuel is destroyed in the afterburning zone. At the same time, reactions leading to the reduction of oxides and their release are reduced by 80%.

The next direction in solving this problem is to abandon the practice of dispersing gaseous emissions. They should not be scattered, relying on the enormous scale of the atmosphere, but, on the contrary, captured and concentrated.

The most effective way to remove sulfur dioxide from emissions is based on its reaction with crushed lime. As a result of the reaction, 90% of the sulfur dioxide binds to the lime, forming gypsum, which can be used in construction. Thus, a thermal power plant with a capacity of 500 MW, equipped with an installation for purifying emissions, produces 600 thousand m 3 of gypsum per year.

A promising measure to reduce harmful impacts is to set limits on emissions. Thus, the US Environmental Protection Agency has set a limit on the total emission of sulfur dioxide in the country, providing for its annual reduction. This event had a certain positive effect.

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Their causes and consequences - actual problems ecology, causing serious concerns for any sane person. Find out why they fall out, as well as what danger they pose.

What is acid rain

Considering the most pressing global environmental problems, many scientists note the formation of acid rain. And in order to assess the consequences of their impact, it is worth first understanding the essence of the phenomenon. Normally, the acidity of any precipitation should be in the range of 5.6-5.8 pH. In this case, the water is a slightly acidic solution that does not cause any consequences and does not affect the environment.

If the acidity of precipitation increases for some reason, it becomes acidic. This term was coined by the Scottish-born chemist Robert Angus Smith in the second half of the 19th century. The problem of acid rain emerged in that distant time, but today it is the most relevant and acute.

Normally, precipitation that falls periodically should have a slightly acidic environment. This is due to the fact that the natural elements that make up the atmosphere (for example, carbon dioxide) react with water, resulting in the formation of a small amount of carbonic acid. The mechanism by which acid rain forms is due to pollutants that penetrate and become trapped in the lower atmospheric layers.

The main component of precipitation with high acidity, as studies have shown, is sulfur oxide. In the atmosphere as a result of photochemical oxidative reaction a certain part of it is transformed into sulfuric anhydride, and it, in turn, in contact with water vapor, turns into sulfuric acid. From the remaining amount of sulfur oxide we get sulfurous acid, which, oxidizing at high humidity, gradually becomes sulfuric.

Another commonly found constituent is nitric oxide, which also reacts with water to form acids.

Fun fact: If you want to figure out what acid rain looks like, you probably won't be able to tell it apart from normal rain. Increased acidity doesn't show up and doesn't change appearance precipitation.

Why does acid precipitation occur?

The causes of acid rain are numerous and the following are the main ones:

• The main reason is emissions from gasoline-powered vehicles. As a result of fuel combustion, vapors rush into the atmosphere and, reacting with water, significantly increase the acidity of precipitation.
• Activities of thermal power plants. Upon combustion various types fuel used to generate heat, there are constant emissions of harmful substances into the atmosphere.
• Acid rain is associated with active mining, processing and use of minerals such as coal, ore, gas and others. They have been used by humanity for quite a long time, and few people think about the dangers of fuel combustion, which causes the release of large quantity carbon dioxide and various pollutants.
• Among the causes of acid rain formation, one can note natural ones, that is, those that do not depend on humans, but are associated with natural phenomena and processes. Thus, during volcanic eruptions, many compounds are released and released into the atmosphere, for example, sulfur oxides, sulfates, hydrogen sulfide. Emissions are also caused by lightning discharges and the activity of microorganisms living in the soil.
• Another reason for the appearance of precipitation with high acidity is the rotting of animal and plant corpses. During these processes, nitrogen- and sulfur-containing compounds arise, which, entering the atmospheric layers and reacting with moisture, turn into acids.
• Among the causes of acid rain, the activities of various industrial and processing enterprises involved in metal processing, production of metal parts, and mechanical engineering should be highlighted. Many factories and factories do not use treatment and filtering facilities, so harmful emissions enter the environment and greatly pollute it.
• Another reason why acid rain is formed is the active use by people of various aerosols and sprays, which contain hydrogen chloride and other equally harmful compounds.
• Acid rain is also caused by leakage of freon from refrigeration equipment and air conditioners.
• Precipitation with increased acidity is caused by the production of certain building materials.
• Fertilizing the soil, especially with toxic compounds, for example, nitrogen-containing ones.

Real threats

What are negative consequences acid rain, what harm does it cause? This is real ecological problem, which represents real threat for the entire ecosystem, environment and people.

Let's look at the main consequences of acid rain:

• Acid rain causes great damage flora. Firstly, such precipitation damages foliage and stems. Secondly, penetrating into the soil, they change its composition, making the soil poor, infertile or even toxic.
• The negative impact of acid rain on the environment extends to water bodies: sedimentary water enters them and accumulates, changing the natural composition. As a result, the environment changes and becomes unsuitable for life of various aquatic inhabitants, including fish.
• Another area of ​​harm from acid rain is the destruction of buildings, monuments, and architectural structures. Acids, when they get on materials, gradually destroy and literally corrode them.
• Acid rain is also very dangerous for humans. Although the concentration of acids, as a rule, does not reach such a level as to corrode the skin, negative effects still occur. Thus, such precipitation can cause heavy allergic reactions which are caused by harmful compounds entering the body. And some scientists believe that with prolonged exposure to precipitation with high acidity, cancer can occur.
• The negative effects of acid rain affect the animal world. The acids contained in the composition can affect the coat, as well as penetrate into the plants consumed by some animals. Often such exposure leads to death, but mutations are possible.

How to solve a problem

The highly acidic rain that appears from time to time is primarily the result of human activity. Therefore, humanity must solve the problem. To reduce the amount of precipitation with high acidity, you should reconsider your attitude towards environment and life on the planet.

Such measures as the introduction of cleaning systems and the installation of filtering equipment in factories and factories, reducing the volume of fuel used and developing alternative energy sources, and the abandonment of toxic fertilizers will help change the situation for the better.

Helpful tip: to protect yourself from negative consequences precipitation follows rainy weather use an umbrella or raincoat and avoid getting drops on exposed skin. In this case, the rain will not harm you.

The problem of precipitation with high acidity is very urgent and requires a comprehensive solution. We need to act together and in several directions.

History of the term

The term “acid rain” was first coined this year by the English researcher Robert Smith. The Victorian smog in Manchester caught his attention. And although scientists of that time rejected the theory of the existence of acid rain, today no one doubts that acid rain is one of the causes of the death of life in water bodies, forests, crops, and vegetation. In addition, acid rain destroys buildings and cultural monuments, pipelines, renders cars unusable, reduces soil fertility and can lead to toxic metals seeping into aquifers. The water of ordinary rain is also a slightly acidic solution. This happens due to the fact that natural substances atmospheres such as carbon dioxide (CO2) react with rainwater. This produces weak carbonic acid (CO2 + H2O -> H2CO3). . While ideally the pH of rainwater is 5.6-5.7, real life The pH value of rainwater in one area may be different from that of rainwater in another area. This, first of all, depends on the composition of gases contained in the atmosphere of a particular area, such as sulfur oxide and nitrogen oxides. In 2009, the Swedish scientist Svante Arrhenius coined two terms - acid and base. He called acids substances that, when dissolved in water, form free positively charged hydrogen ions (H+). He called bases substances that, when dissolved in water, form free negatively charged hydroxide ions (OH-). The term pH is used as an indicator of the acidity of water. The term pH means, translated from English, an indicator of the degree of concentration of hydrogen ions.

Chemical reactions

It should be noted that even normal rainwater has a slightly acidic (pH about 6) reaction due to the presence of carbon dioxide in the air. Acid rain is formed by a reaction between water and pollutants such as sulfur oxide (SO2) and various nitrogen oxides (NOx). These substances are released into the atmosphere by car, as a result of the activities of metallurgical enterprises and power plants. Sulfur compounds (sulfides, native sulfur and others) are contained in coals and ores (especially a lot of sulfides in brown coals), when burned or roasted, volatile compounds are formed - sulfur oxide (IV) - SO 2 - sulfur dioxide, sulfur oxide (VI) - SO 3 - sulfuric anhydride, hydrogen sulfide - H 2 S (in small quantities, with insufficient firing or incomplete combustion, at low temperature). Various nitrogen compounds are found in coals, and especially in peat (since nitrogen, like sulfur, is part of the biological structures from which these minerals were formed). When such fossils are burned, nitrogen oxides (acid oxides, anhydrides) are formed - for example, nitrogen oxide (IV) NO 2. Reacting with atmospheric water (often under the influence solar radiation, so-called “photochemical reactions”), they are converted into solutions of acids - sulfuric, sulfurous, nitrous and nitric. Then, along with snow or rain, they fall to the ground.

Environmental and economic consequences

The consequences of acid rain are observed in the USA, Germany, the Czech Republic, Slovakia, the Netherlands, Switzerland, Australia, and republics former Yugoslavia and in many more countries globe. Acid rain has a negative impact on bodies of water - lakes, rivers, bays, ponds - increasing their acidity to such a level that flora and fauna die in them. There are three stages of the impact of acid rain on water bodies. The first stage is the initial stage. With an increase in water acidity (pH values ​​less than 7), aquatic plants begin to die, depriving other animals of the reservoir of food, the amount of oxygen in the water decreases, and algae (brown-green) begin to rapidly develop. The first stage of eutrophication (swamping) of a reservoir. At pH6 acidity, freshwater shrimp die. The second stage - acidity rises to pH5.5, bottom bacteria die, which decompose organic matter and leaves, and organic debris begins to accumulate at the bottom. Then plankton, the tiny animal that forms the basis, dies the food chain reservoir and feeds on substances formed during decomposition by bacteria organic matter. The third stage - acidity reaches pH 4.5, all fish, most frogs and insects die. The first and second stages are reversible when the impact of acid rain on the reservoir ceases. As organic matter accumulates at the bottom of water bodies, toxic metals begin to leach out. Increased water acidity promotes higher solubility of hazardous metals such as aluminum, cadmium, and lead from sediments and soils. These toxic metals pose a risk to human health. People, drinking water with high levels of lead or who eat fish with high levels of mercury can become seriously ill. Acid rain not only harms aquatic flora and fauna. It also destroys vegetation on land. Scientists believe that although the mechanism is not yet fully understood to this day, “a complex mixture of pollutants, including acid precipitation, ozone, and heavy metals together lead to forest degradation. Economic losses from acid rain in the United States, according to one study, are estimated at east coast 13 million dollars and by the end of the century losses will reach 1.750 billion dollars from forest loss; $8.300 billion in crop losses (in the Ohio River Basin alone) and $40 million in medical expenses in Minnesota alone. The only way to change the situation for the better, according to many experts, is to reduce the amount of harmful emissions into the atmosphere.

Literature

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