What is acid rain. Causes and harmful effects of acid rain

Pollution of the atmosphere with compounds of sulfuric and nitric acids, followed by precipitation is called acidicrains. Acid rains are formed as a result of the emission of sulfur and nitrogen oxides into the atmosphere by enterprises of the fuel and energy complex, 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 pure water, pH = 7, which corresponds to a neutral reaction. Solutions with a pH below 7 are acidic, above - alkaline. The entire range of acidity-alkalinity is covered by pH values ​​from 0 to 14.

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

The industry of 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 in 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" reservoirs, destroying almost all life in them - from fish to microorganisms and vegetation, destroying forests, destroying buildings and architectural monuments. Many animals and plants cannot survive in conditions of high acidity. Acid rains not only cause acidification of surface waters and upper soil horizons, but also spread with descending water flows to the entire soil profile and cause significant acidification of groundwater.

Sulfur is found in such minerals 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 formed compounds are partially captured by treatment devices, the rest of them are emitted 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 global problems such as global warming and ozone depletion, its impact extends far beyond the source country.

Acid rain and reservoirs. 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 getting acid rain into water bodies (rivers, ponds, lakes and reservoirs) includes many stages, at each of which their pH can both decrease and increase. For example, a change in the pH of sediments is possible when they move along the forest floor, interact with minerals, products of the activity of microorganisms.

All living things are sensitive to changes in pH, so the increase in the acidity of water bodies causes irreparable harm to fish stocks. In Canada, for example, due to frequent acid rains, more than 4,000 lakes have been declared dead, and another 12,000 are on the verge of death. The biological balance of 18 thousand lakes in Sweden has been disturbed. Fish have disappeared from half of 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 rains are amazingly transparent and unusually blue.

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

Acid rain and crop yieldstour. It has been established that the effects of acid rain on agricultural crops are determined not only by their acidity and cationic composition, but also by the duration and air temperature. In the general case, 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. Hence, it is obvious that it is necessary to quantitatively take into account all the 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.

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

The intensity of the destruction of materials depends on: their porosity, since the higher the specific surface, the greater its sorption capacity; from structural 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: from 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 due to the intensity of catalytic reactions involving metals, as well as synergism (synergism is the ability of one substance to enhance the effect of another), while uniform corrosion is most often observed.

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

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

use of low-sulphur coals at CHPPs;

emission cleaning.

Low-sulfur coals are considered with a sulfur content of less than 1%, and high-sulfur coals with a sulfur content of more than 3%. To reduce the chance of acid rain formation, sour coals are pre-treated. The composition of coal usually includes 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. To remove organic sulfur, methods of chemical and microbiological treatment are currently being developed.

Similar methods should be applied to sour crudes. World reserves of oil with a low sulfur content (up to 1%) are small and do not exceed 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 under conditions of oxygen deficiency, which is ensured by the rate of air supply to the combustion zone. In Japan, the technology of "afterburning" of primary combustion products has been developed. In this case, first, the fuel (oil, gas) is burned in the optimal mode for the formation of 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 vast scale of the atmosphere, but, on the contrary, should be captured and concentrated.

The most effective way to clean emissions from sulfur dioxide is based on its reaction with crushed lime. As a result of the reaction, 90% of sulfur dioxide binds to 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 cleaning emissions, produces 600 thousand m 3 of gypsum per year.

A promising measure to reduce harmful impacts is the establishment of emission limits. 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.

Recently, due to the general deterioration of the ecological situation on our planet, such an unpleasant environmental phenomenon as acid rains has become more and more frequent. The occurrence of acid rain occurs due to the interaction of air and water in the upper atmosphere with various pollution.

History of acid rain

The first acid rain in history was recorded back in 1872, just in the era of the heyday of industrialization, the mass construction of factories and factories. Needless to say, by the 20th century, this phenomenon had become many times more frequent and, of course, we inherited the inhabitants of the 21st century.

Causes of acid rain

What are the causes of acid rain? Ecologists divide them into anthropogenic and natural. Anthropogenic causes of acid rain associated with human action, these include:

• Emissions from plants and factories of various oxides of nitrogen and sulfur. Once in the atmosphere, they interact with water vapor, resulting in the formation of sulfuric acid, which falls out in such acid rains.
• Exhaust gases, another source of atmospheric pollution, are also another cause of acid rain.

The natural causes of acid rain are not related to human activity, as a rule, they occur as a result of volcanic eruptions, then a large amount of nitrogen-containing substances also enter the atmosphere, when interacting with which nitric acid is formed, which precipitates with acid rain.

The effects of acid rain

What are the effects of acid rain? There are many negative consequences:

• destruction of agricultural crops
• water pollution,
• deforestation,
• diseases in people.

Contact with acid rain increases the risk of diseases such as asthma, allergies, and cancer. Acid rain pollutes rivers and lakes, making water unusable, which can kill huge populations of fish. Acid rain pollutes the soil and loses its fertility, as a result, the crop decreases. Plants also suffer from them, leaves fall off trees and the development of roots is inhibited, plants become sensitive to temperature changes.

Ways to solve the problem of acid rain

The main step towards solving the environmental problem of acid rain, as well as the problem, is to reduce the emission of harmful industrial waste into the atmosphere, the use of cleaning filters in plants and factories. And in the future, the creation of environmentally friendly industries, in general, all modern technologies should be introduced only after assessing their impact on the environment.

The gradual transition to green electric vehicles will also be a step towards overcoming the problem of acid rain. The first such Tesla cars are already slowly gaining popularity, and we really want to believe that in the future they will become ubiquitous, and gasoline cars will become history, like the old steam trains did.

Acid rain video

And finally, a small educational video about acid rain.

Acid rain - the price of progress

Scientists have long sounded the alarm: environmental pollution has reached incredible proportions. Discharge of liquid waste into water bodies, exhaust gases and volatile chemicals into the atmosphere, burial of nuclear remains underground - all this has brought mankind to the brink of ecological disaster.

We have already witnessed the beginning of shifts in the planet's ecosystem: every now and then in the news they report weather phenomena that are atypical for a particular area, Green Peace is sounding the alarm in connection with the mass disappearance of entire species of animals, acid rain has become not uncommon, but rather a regularity. regularly going over the industrial cities. A person is faced with an ambiguous situation: an increase in the standard of living is accompanied by a deterioration in the environment, which affects the state of health. This problem has long been recognized worldwide. Mankind should think: is technological progress worth the consequences that it entails? To better understand this problem, consider one of the "achievements" of the modern industry - acid rain, which in our time is told even at school. Are they really that dangerous?

Acid rain: causes and consequences

Not only rain can be acidic, but also snow, dew and even fog. On the face of it

normal precipitation, but their acid values ​​are much higher than normal, which is the reason for their negative impact on the environment. The mechanism of acid rain formation is as follows: exhaust gases and other industrial wastes containing large doses of sulfur oxide and sodium enter the atmosphere, where they bind with water droplets, forming a weakly concentrated acid solution, which falls to the ground as precipitation, causing irreparable harm to nature. Acid rain poisons the water that animals drink; falling into water bodies, they slowly destroy the local flora and fauna, kill agricultural crops, spilling over the fields, falling into the soil, poisoning it. Such precipitation causes significant damage even to engineering structures, corroding the stone walls of buildings and undermining reinforced concrete load-bearing structures. Acid precipitation is the fate of not only large cities and industrial

zones, poisonous clouds can be transported by air masses for thousands of kilometers and fall over forests and lakes.

How to deal with acid rain?

The consequences of acid rain are detrimental not only to the environment, but also to the economy, and everyone knows this. So why are decisive measures not being taken to improve the situation? In order to reduce emissions into the atmosphere, multibillion-dollar investments are required: it is necessary to modernize the production technology, as for automobile exhausts, it is necessary to switch to more modern types of fuel. The result will be tangible only when the entire world community is involved in solving this problem. Unfortunately, in the pursuit of prosperity and GDP growth, the governments of many countries do not pay due attention to the problem of protecting the environment.

Acid rain was first recorded in Western Europe, in particular Scandinavia, and North America in the 1950s. Now this problem exists throughout the industrial world and has acquired particular importance in connection with the increased technogenic emissions of sulfur and nitrogen oxides. Within a few decades, the scale of this disaster became so wide, and the negative consequences were so great, that in 1982 a special international conference on acid rain was held in Stockholm, which was attended by representatives of 20 countries and a number of international organizations. Until now, the severity of this problem remains, it is constantly in the focus of attention of national governments and international environmental organizations. On average, the acidity of precipitation, which falls mainly in the form of rain in Western Europe and North America, covers an area of ​​almost 10 million square meters. km, is 5-4.5, and fogs here often have a pH of 3-2.5. In recent years, acid rain has been observed in industrial areas of Asia, Latin America and Africa. For example, in the Eastern Transvaal (South Africa), where 4/5 of the country's electricity is generated, per 1 sq. km falls about 60 tons of sulfur per year in the form of acid precipitation. In tropical regions, where industry is practically undeveloped, acid precipitation is caused by the release of nitrogen oxides into the atmosphere due to the burning of biomass.

A specific feature of acid rain is its transboundary nature, due to the transfer of acid-forming emissions by air currents over long distances - hundreds and even thousands of kilometers. This is largely facilitated by the once adopted "policy of high pipes" as an effective means of combating surface air pollution. Almost all countries simultaneously are "exporters" of their own and "importers" of foreign emissions. The "wet" part of the emissions (aerosols) is exported, the dry part of the pollution falls in the immediate vicinity of the emission source or at a small distance from it.

Exchange acid-forming and other air pollutant emissions are typical for all countries of Western Europe and North America. Great Britain, Germany, France send more oxidized sulfur to their neighbors than they receive from them. Norway, Sweden, Finland receive more oxidized sulfur from their neighbors than they release through their own borders (up to 70% of acid rain in these countries is the result of "export" from the UK and Germany). The transboundary transport of acid rain is one of the reasons for the conflict between the US and Canada.

Acid rain and its causes

The term "acid rain" refers to all types of meteorological precipitation - rain, snow, hail, fog, sleet - whose pH is less than the average pH of rainwater (the average pH for rainwater is 5.6). Sulfur dioxide (SO2) and nitrogen oxides (NOx) released during human activity are transformed in the earth's atmosphere into acid-forming particles. These particles react with atmospheric water, turning it into acid solutions, which lower the pH of rainwater. The term "acid rain" was first introduced in 1872 by the English explorer Angus Smith. His attention was drawn to the Victorian smog in Manchester. 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 reasons for the death of life in reservoirs, forests, crops, and vegetation. In addition, acid rain destroys buildings and cultural monuments, pipelines, renders cars unusable, reduces soil fertility and can lead to seepage of toxic metals into aquifers.

Normal rain water is also a slightly acidic solution. This is due to the fact that natural substances in the atmosphere, 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, in real life the acidity of rainwater in one area may differ from the acidity of rainwater in another area. This primarily depends on the composition of gases contained in the atmosphere of a particular area, such as sulfur oxide and nitrogen oxides.

Chemical analysis of acid precipitation shows the presence of sulfuric (H2SO4) and nitric (HNO3) acids. The presence of sulfur and nitrogen in these formulas indicates that the problem is related to the release of these elements into the atmosphere. When fuel is burned, sulfur dioxide enters the air, atmospheric nitrogen also reacts with atmospheric oxygen and nitrogen oxides are formed.

As already mentioned, any rainwater has a certain level of acidity. But in the normal case, this indicator corresponds to a neutral pH level - 5.6-5.7 or slightly higher. A slight acidity is due to the content of carbon dioxide in the air, but it is considered so low that it does not cause any harm to living organisms. Thus, the causes of acid rain are associated exclusively with human activities, and cannot be explained by natural causes.

Prerequisites for increasing the acidity of atmospheric water arise when industrial enterprises emit large volumes of sulfur oxides and nitrogen oxides. The most typical sources of such pollution are vehicle exhaust gases, metallurgical production and thermal power plants (CHP). Unfortunately, the current level of development of purification technologies does not allow filtering out nitrogen and sulfur compounds that result from the combustion of coal, peat, and other types of raw materials that are used in industry. As a result, such oxides enter the atmosphere, combine with water as a result of reactions under the action of sunlight, and fall to the ground in the form of precipitation, which is called "acid rain".

Acid phrases in modern, especially urban life have become commonplace. Summer residents often complain that after such unpleasant precipitation, the plants begin to wither, and a whitish or yellowish coating appears in the puddles.

What it is

Science has a definite answer to the question of what acid rain is. These are all known whose water is below normal. pH 7 is considered the norm. If the study shows an underestimation of this figure in precipitation, they are considered acidic. In the context of an ever-increasing industrial boom, the acidity of rain, snow, fog and hail is hundreds of times higher than normal.

Causes

Acid rain falls again and again. The reasons lie in toxic emissions from industrial facilities, car exhaust gases, and to a much lesser extent - in the decay of natural elements. The atmosphere is filled with sulfur and nitric oxides, hydrogen chloride and other compounds that form acids. The result is acid rain.

There are precipitation and alkaline content. They contain calcium or ammonia ions. The concept of "acid rain" also fits them. This is explained by the fact that, getting into a reservoir or soil, such precipitation affects the change in the water-alkaline balance.

What causes acid precipitation

Of course, the oxidation of the surrounding nature does not entail anything good. Acid rain is extremely harmful. The reasons for the death of vegetation after the fall of such precipitation lie in the fact that many useful elements are leached from the earth by acids, in addition, pollution by hazardous metals is also observed: aluminum, lead and others. Polluted sediments cause mutations and death of fish in water bodies, improper development of vegetation in rivers and lakes. They also have a detrimental effect on the normal environment: they significantly contribute to the destruction of natural facing materials, and cause accelerated corrosion of metal structures.

Having become acquainted with the general characteristics of this atmospheric phenomenon, we can conclude that the problem of acid rain is one of the most urgent from the point of view of ecology.

Scientific research

It is important to dwell in more detail on the scheme of chemical pollution of nature. Acid rain is the cause of many environmental disturbances. Such a characteristic of precipitation appeared in the second half of the 19th century, when a British chemist R. Smith identified the content of hazardous substances in vapors and smoke, which greatly change the chemical picture of precipitation. In addition, acid rain is a phenomenon that spreads over vast areas, regardless of the source of pollution. The scientist also noted the destruction that the contaminated sediments entailed: plant diseases, loss of color in tissues, accelerated spread of rust, and others.

Experts are more precise in their definition of what acid rain is. Indeed, in reality it is snow, fogs, clouds and hail. Dry precipitation with a lack of atmospheric moisture falls in the form of dust and gas.

on nature

Lakes are dying, the number of fish shoals is decreasing, forests are disappearing - all these are terrible consequences of the oxidation of nature. Soils in forests are not nearly as sensitive to acidification as bodies of water, but plants perceive all changes in acidity very negatively. Like an aerosol, harmful precipitation envelops foliage and needles, impregnates trunks, and penetrates the soil. Vegetation receives chemical burns, gradually weakening and losing the ability to survive. Soils lose their fertility and saturate growing crops with toxic compounds.

biological resources

When a study of lakes in Germany was carried out, it was found that in reservoirs where the water index deviated significantly from the norm, the fish disappeared. Only in some lakes single specimens were caught.

Historical heritage

Seemingly invulnerable human creations also suffer from acid rain. The ancient Acropolis, located in Greece, is known throughout the world for the outlines of its mighty marble statues. Ages do not spare natural materials: the noble rock is destroyed by winds and rains, the formation of acid rain further activates this process. Restoring historical masterpieces, modern masters did not take measures to protect metal joints from rust. The result is that acid rain, by oxidizing the iron, causes large cracks in the statues, the marble cracks due to the pressure of rust.

cultural monuments

The United Nations has initiated studies on the effects of acid rain on cultural heritage sites. In the course of them, the negative consequences of the action of rains on the most beautiful stained-glass windows of the cities of Western Europe were proved. Thousands of colored glasses are at risk of sinking into oblivion. Until the 20th century, they delighted people with their strength and originality, but the last decades, overshadowed by acid rain, threaten to destroy the magnificent stained glass paintings. Dust saturated with sulfur destroys antique leather and paper items. Ancient products under the influence lose their ability to resist atmospheric phenomena, become brittle and may soon crumble to dust.

Ecological catastrophy

Acid rain is a serious problem for the survival of mankind. Unfortunately, the realities of modern life require an ever-increasing expansion of industrial production, which increases the volume of poisonous ones. The population of the planet is increasing, living standards are rising, there are more and more cars, energy consumption is going through the roof. At the same time, the thermal power plants of the Russian Federation alone pollute the environment every year with millions of tons of anhydride containing sulfur.

Acid rain and ozone holes

Ozone holes are no less common and cause more serious concern. Explaining the essence of this phenomenon, it must be said that this is not a real rupture of the atmospheric shell, but a violation in the thickness of the ozone layer, which is located approximately 8-15 km from the Earth and extends into the stratosphere up to 50 km. The accumulation of ozone largely absorbs harmful solar ultraviolet radiation, protecting the planet from the strongest radiation. That is why ozone holes and acid rain are threats to the normal life of the planet, requiring the closest attention.

The integrity of the ozone layer

The beginning of the 20th century added chlorofluorocarbons (CFCs) to the list of human inventions. Their feature was exceptional stability, no smell, incombustibility, no toxic effect. CFCs gradually began to be introduced everywhere into the production of various cooling units (from cars to medical complexes), fire extinguishers, and household aerosols.

Only by the end of the second half of the twentieth century, chemists Sherwood Roland and Mario Molina suggested that these miracle substances, otherwise called freons, strongly affect the ozone layer. At the same time, CFCs can “hover” in the air for decades. Gradually rising from the ground, they reach the stratosphere, where ultraviolet radiation destroys freon compounds, releasing chlorine atoms. As a result of this process, ozone is converted into oxygen much faster than in normal natural conditions.

The terrible thing is that only a few chlorine atoms are required to modify hundreds of thousands of ozone molecules. In addition, chlorofluorocarbons are considered greenhouse gases contributing to global warming. In fairness, it should be added that nature itself also contributes to the destruction of the ozone layer. Thus, volcanic gases contain up to a hundred compounds, including carbons. Natural freons contribute to the active thinning of the ozone layer above the poles of our planet.

What can be done?

Finding out what the danger of acid rain is is no longer relevant. Now on the agenda in every state, at every industrial enterprise, first of all, there should be measures to ensure the purity of the surrounding air.

In Russia, giant plants, such as RUSAL, have begun to approach this issue very responsibly in recent years. They spare no expense to install modern reliable filters and purification facilities that prevent oxides and heavy metals from entering the atmosphere.

Increasingly, alternative methods of obtaining energy are being used that do not entail dangerous consequences. Wind and solar energy (for example, in everyday life and for cars) is no longer a fantasy, but a successful practice that helps to reduce the amount of harmful emissions.

The expansion of forest plantations, the cleaning of rivers and lakes, the proper processing of garbage - all these are effective methods in the fight against environmental pollution.