Acid rain

The general concept of "acid rain":

The term "acid rain" was first introduced in 1872 by the English explorer Angus Smith, whose attention was drawn to the smog in Manchester. And although scientists of that time rejected the theory of the existence of acid rain, today it is an obvious fact that acid rain is one of the causes of the death of living organisms, forests, crops, and other types of vegetation. In addition, acid rain destroys buildings and architectural monuments, renders metal structures unusable, reduces soil fertility, and can lead to seepage of toxic metals into aquifers.

The term "acid rain" refers to all types of meteorological precipitation - rain, snow, hail, fog, sleet - whose pH is less than the average pH value of rainwater, which is approximately equal to 5.6. "Clean" rain is usually always slightly acidic because the carbon dioxide (CO 2 ) in the air reacts chemically with rainwater to form weak carbonic acid. Theoretically, such a "clean", slightly acidic rain should have a pH = 5.6, which corresponds to the equilibrium between CO 2 of water and CO 2 of the atmosphere. However, due to the constant presence of various substances in the atmosphere, rain is never completely "pure", and its pH varies from 4.9 to 6.5, with an average value of about 5.0 for the temperate forest zone. In addition to CO 2, various sulfur and nitrogen compounds also naturally enter the Earth's atmosphere, which impart an acidic reaction to rainfall. Thus, "acid rain" can also occur for natural reasons. However, in addition to the natural entry into the Earth's atmosphere of various oxides with an acidic reaction, there are also anthropogenic sources, the emission from which is many times higher than the natural one. Pollution of the atmosphere with a large amount of sulfur and nitrogen oxides can increase the acidity of precipitation to pH = 4.0, which is beyond the values ​​tolerated by most living organisms.

Causes of acid rain:

The main cause of acid rain is the presence of sulfur dioxide SO 2 and nitrogen dioxide NO 2 in the Earth's atmosphere, which, as a result of chemical reactions occurring in the atmosphere, turn into sulfuric and nitric acids, respectively, the precipitation of which on the earth's surface affects living organisms and the ecotope in in general.

Types of sulfur compounds:

The most important sulfur compounds found in the Earth's atmosphere include:

1. Sulfur dioxide - SO 2

2. Carbon oxysulfide - COS

3. Carbon disulfide - CS 2

4. Hydrogen sulfide - H 2 S

5. Dimethyl sulfide - (CH 3) 2 S

6. Sulfate ion - SO 4 2-

Sources of sulfur compounds:

Natural sources of sulfur emission into the atmosphere:

I. Biological isolation. Almost without exception, traditional models of the sulfur cycle showed that about 50% of sulfur appears in the atmosphere due to its biological transformations in soil and water ecosystems. It is assumed that as a result of ongoing microbiological processes, in these natural ecosystems, sulfur volatilizes in the form of hydrogen sulfide (H 2 S). Numerous scientific data indicate that microorganisms produce hydrogen sulfide mainly in two ways:

1. recovery of sulfates.

2. decomposition of organic matter.

Desulfovibrio as well as related bacteria, sulphate reducers, inhabit swamps, marshes and poorly drained soils in abundance. These microorganisms use sulfates as the final electron acceptor. Also, an extremely large and diverse group of microorganisms, including aerobes, thermophiles, psychrophiles, bacteria, actinomycetes and fungi, decomposes sulfur-containing organic compounds and releases hydrogen sulfide. The surface of the sea and its deep layers can also contain significant amounts of hydrogen sulfide. At present, the sources of the formation of dimethyl sulfide are not entirely known, but it is assumed that seaweeds are involved in their occurrence. Biological sulfur emissions do not exceed 30-40 million tons per year, which is approximately 1/3 of the total amount of sulfur released.

II. Volcanic activity. When a volcano erupts, hydrogen sulfide, sulfates and elemental sulfur enter the Earth's atmosphere along with a large amount of sulfur dioxide. These compounds enter mainly into the lower layer - the troposphere, and with separate, large eruptions, an increase in the concentration of sulfur compounds is observed in higher layers - in the stratosphere. With the eruption of volcanoes, about 2 million tons of sulfur-containing compounds enter the atmosphere annually on average. For the troposphere, this amount of sulfur is insignificant compared to biological release, while for the stratosphere, volcanic eruptions are the most important sources of sulfur.

III. The surface of the oceans. After the evaporation of water droplets entering the atmosphere from the surface of the oceans, sea salt remains, containing, along with sodium and chlorine ions, sulfur compounds - sulfates.

Together with particles of sea salt, from 50 to 200 million tons of sulfur annually enter the Earth's atmosphere, which is much more than the emission of sulfur into the atmosphere in a natural way. At the same time, due to their large size, salt particles quickly fall out of the atmosphere and, thus, only an insignificant part of sulfur enters the upper layers and is sprayed over land. However, one should take into account the fact that sulfates of marine origin cannot form sulfuric acid, therefore, from the point of view of the formation of acid rain, they are not significant. Their influence affects only the regulation of the formation of clouds and precipitation.

Anthropogenic sources of sulfur emission into the atmosphere:

Types of nitrogen compounds:

The composition of the atmosphere includes a number of nitrogen-containing compounds, of which nitrous oxide (N 2 O) is the most common. This gas in the lower layers of the air is neutral and does not participate in the formation of acid rain. Also in the composition of the Earth's atmosphere are acidic nitrogen oxides, such as: nitric oxide NO, and nitrogen dioxide NO 2. In addition, the composition of the atmosphere includes the only alkaline nitrogen compound - ammonia.

The most important nitrogen compounds found in the Earth's atmosphere are:

1. Nitrous oxide - NO 2

2. Nitric oxide - NO

3. Nitrous anhydride - N 2 O 3

4. Nitrogen dioxide - NO 2

5. Nitric oxide - N 2 O 5

Sources of nitrogen compounds:

Natural sources of emission of nitrogen compounds into the atmosphere:

I. Soil emission of nitrogen oxides. During the activity of denitrifying bacteria living in the soil, nitrogen oxides are released from nitrates. According to data for 1990, about 8 million tons of nitrogen oxides (in terms of nitrogen) are formed in this way every year around the world.

II. Thunderstorms. During electrical discharges in the atmosphere, due to the very high temperature and the transition to the plasma state, molecular nitrogen and oxygen in the air combine to form nitrogen oxides. The amount of nitrogen oxide formed in this way is about 8 million tons.

III. Burning biomass. This type of source can be of both artificial and natural origin. The largest amount of biomass is burned as a result of the process of burning the forest (in order to obtain production space) and fires in the savannah. During the combustion of biomass, 12 million tons of nitrogen oxides (in terms of nitrogen) enter the air during the year.

IV. Other sources. Other sources of natural emissions of nitrogen oxides are less significant and difficult to assess. These include: the oxidation of ammonia in the atmosphere, the decomposition of nitrous oxide located in the stratosphere, as a result of which a mixture of the formed oxides NO and NO 2 enters the troposphere, and, finally, photolytic and biological processes in the oceans. These sources jointly produce during the year from 2 to 12 million tons of nitrogen oxides (in terms of nitrogen).

Anthropogenic sources of emission of nitrogen compounds into the atmosphere:

Among the anthropogenic sources of nitrogen oxide formation, the combustion of fossil fuels (coal, oil, gas, etc.) ranks first. During combustion, as a result of the occurrence of high temperature, the nitrogen and oxygen in the air combine. In this case, the amount of nitric oxide NO produced is proportional to the combustion temperature. In addition, nitrogen oxides are formed as a result of the combustion of nitrogen-containing substances present in the fuel. By burning fossil fuels, humanity annually releases about 12 million tons into the Earth's air basin. nitrogen oxides. Slightly less nitrogen oxides, about 8 million tons. per year comes from the combustion of fuel (gasoline, diesel fuel, etc.) in internal combustion engines. Industry around the world emits about 1 million tons. nitrogen annually. Thus, at least 37% of the nearly 56 Mt. annual emissions of nitric oxide is formed from anthropogenic sources. This percentage, however, will be much higher if biomass combustion products are added to it.

Atmospheric ammonia:

Ammonia, which is alkaline in aqueous solution, plays a significant role in the regulation of acid rain, as it can neutralize atmospheric acidic compounds:

NH 3 + H 2 SO 4 \u003d NH 4 HSO 4

NH 3 + NH 4 HSO 4 = (NH 4) 2 SO 4

NH 3 + HNO 3 \u003d NH 4 NO 3

Thus, acid precipitation is neutralized and sulfates and ammonium nitrate are formed.

Soil is the most important source of atmospheric ammonia. Organic matter in the soil is broken down by certain bacteria, and one of the end products of this process is ammonia. The scientists were able to establish that the activity of the bacterium, which ultimately leads to the formation of ammonia, depends primarily on the temperature and moisture of the soil. At high geographic latitudes (North America and Northern Europe), especially during the winter months, soil ammonia release can be negligible. At the same time, these areas have the highest levels of sulfur dioxide and nitrogen oxide emissions, as a result of which the acids in the atmosphere are not neutralized and, thus, the risk of acid rain increases. During the breakdown of pet urine, large amounts of ammonia are released. This source of ammonia is so significant that in Europe it exceeds the capacity of the soil to release ammonia.

Chemical transformations of sulfur compounds:

As a rule, sulfur is included in emissions not in a completely oxidized form (the oxidation state of sulfur in its dioxide is 4, i.e. one sulfur atom is attached to two oxygen atoms). If sulfur compounds are in the air for a sufficiently long time, then under the action of oxidizing agents contained in the air, they turn into sulfuric acid or sulfates. In the process of oxidation of sulfur dioxide gas (SO 2) with oxygen (O 2), sulfur increases its oxidation state and passes into sulfur trioxide (SO 3), which in turn, being a very hygroscopic substance and interacting with atmospheric water, very quickly turns into H 2 SO4. It is for this reason that under normal atmospheric conditions, sulfur trioxide is not found in the air in large quantities. As a result of the reaction, sulfuric acid molecules are formed, which quickly condense in the air or on the surface of aerosol particles.

In addition to sulfur dioxide, there are also significant amounts of other naturally occurring sulfur compounds in the atmosphere, which eventually oxidize to sulfuric acid (or sulfates).

Chemical transformations of nitrogen compounds:

Nitric oxide NO is the most common nitrogen compound that is emitted, which reacts with atmospheric oxygen to form nitrogen dioxide. The latter, as a result of the reaction with the hydroxyl radical, turns into nitric acid NO 2 + OH = HNO 3. Nitric acid obtained in this way, unlike sulfuric acid, can remain in a gaseous state for a long time, since it does not condense well. This is due to the fact that nitric acid is more volatile than sulfuric acid. Vapors of nitric acid can be absorbed by cloud or precipitation droplets or aerosol particles.

Acid sedimentation (acid rain)

The final step in the pollutant cycle is sedimentation, which can occur in two ways:

1. washing out of sediments, or wet sedimentation

2. precipitation, or dry sedimentation

The combination of these two processes is called acid sedimentation.

Impact of acid rain on the environment

The result of acid sedimentation is that acidic atmospheric trace elements, sulfur and nitrogen compounds fall on the Earth's surface, which leads to strong changes in the acidity of water bodies and soils. First of all, the increase in acidity affects the state of freshwater reservoirs and forests. Acid rain has different effects. Initially, precipitation with a high nitrogen content at first contributes to the growth of trees in the forest, as the trees are supplied with nutrients. However, as a result of their constant consumption, the forest is oversaturated with them, which leads to soil acidification. As a result of changes in soil acidity, the solubility of heavy and toxic metals in them changes, which can enter the body of animals and humans by being transmitted along the trophic chain, in which their accumulation will occur. Under the action of acidity, the biochemical structure of the soil changes, which leads to the death of soil biota and some plants.

Under the influence of acid rain, inorganic compounds are washed out of plants, which include all the main micro- and macroelements. So, for example, potassium, calcium, magnesium and manganese are usually washed out in the largest quantities. Various organic compounds, such as sugars, amino acids, organic acids, hormones, vitamins, pectin and phenolic substances, etc., are also subjected to leaching from plants. As a result of these processes, the loss of biogenic elements necessary for plants increases, which results in their damage.

Hydrogen ions entering the soil with acid rain can be replaced by cations in the soil, resulting in either leaching of calcium, magnesium and potassium, or their sedimentation in a dehydrated form. The mobility of toxic heavy metals such as manganese, copper, and cadmium is increasing. The solubility of heavy metals is strongly dependent on pH. Dissolved and, as a result, easily absorbed by plants, heavy metals are poisonous for plants and can lead to their death. One of the most dangerous elements for living organisms living in the soil is aluminum dissolved in a strongly acidic environment. Many soils, such as those in the northern temperate and boreal forest zones, absorb higher concentrations of aluminum than those of alkali cations. Although many plant species are able to withstand this ratio, when significant amounts of acid rain fall, the aluminum-calcium ratio in soil water changes so much that root growth is weakened and trees are endangered.

Changes in soil composition can alter the composition of soil microorganisms, affect their activity, and thereby influence decomposition and mineralization processes, as well as nitrogen fixation and internal acidification.

Despite acid precipitation, the soil has the ability to equalize the acidity of the environment, i.e. to a certain extent, it can resist the increase in acidity. Soil resistance usually determines the presence of limestone and sandstone rocks (which include calcium carbonate CaCO 3), which, as a result of hydrolysis, have an alkaline reaction.

Acidification of fresh waters.

Acidification of fresh water is the loss of their ability to neutralize. Acidification is usually caused by strong acids such as sulfuric and nitric acid. Over a long period, sulfates play a more important role, but during episodic events (snowmelt), sulfates and nitrates act together.

The process of acidification of water bodies can be divided into 3 phases:

1. Loss of bicarbonate ions, i.e. decrease in the ability to neutralize at a constant pH value.

2. Decrease in pH with a decrease in the amount of bicarbonate ions. The pH value then falls below 5.5. The most sensitive species of living organisms begin to die already at pH = 6.5.

The death of living beings, in addition to the action of a highly toxic aluminum ion, can also be caused by the fact that cadmium, zinc, lead, manganese, and other toxic heavy metals are released under the influence of a hydrogen ion. The amount of plant nutrients begins to decrease. The aluminum ion forms insoluble aluminum phosphate with the orthophosphate ion, which precipitates in the form of a bottom sediment: Al 3+ + PO 4 3- ª AlPO 4. As a rule, a decrease in the pH of water goes in parallel with a decrease in populations and the death of fish, amphibians, phyto- and zooplankton, as well as many different other organisms.

The acidification of lakes and rivers has reached the greatest scale in Sweden, Norway, the USA, Canada, Denmark, Belgium, Holland, Germany, Scotland, Yugoslavia and in a number of European countries. A study of 5,000 lakes in southern Norway found that 1,750 of them had lost fish populations, and 900 other lakes were in serious danger. In southern and central Sweden there is a loss of fish in 2500 lakes, the same is expected in another 6500 lakes where signs of acidification have already been found. Nearly 18,000 lakes have a water pH of less than 5.5, which has a very adverse effect on fish populations.

Direct effects of acid precipitation on the environment

1. Plant death. The direct death of plants is most observed near the direct source of emissions, as well as within a radius of several tens of kilometers from this source. The main reason is the high concentration of sulfur dioxide. This compound is adsorbed on the surface of the plant, mainly on its leaves, and penetrating into the body of the plant, it takes part in various redox reactions. Under their influence, the oxidation of unsaturated fatty acids of membranes occurs, thereby changing their permeability, which further affects such vital processes as respiration and photosynthesis. First of all, the death of lichens occurs, which can exist only in a very clean state of the environment. Lichens are sensitive indicators of various types of air pollution. Recent research from the University of Nottingham has shown that cushion-forming species of the genus Cladonia can serve as sensitive indicators of acid rain.

2. direct impact on humans. Acid aerosol particles are of particular danger to human health. The degree of their danger depends primarily on their size. Large aerosol particles linger in the upper respiratory tract, while small (less than 1 micron.) droplets consisting of a mixture of sulfuric and nitric acids can penetrate into the most distant parts of the lungs and cause significant damage there. In addition, metals such as aluminum (and other heavy metals) can get into the food chain at the top of which a person stands, which can lead to his poisoning.

3. Corrosion of metals, buildings and monuments. The cause of corrosion is an increase in the concentration of hydrogen ions on the surface of metals, on which their oxidation largely depends. In suburban areas, the degree of corrosion of metal structures is several micrometers per year, while in polluted urban areas it can reach 100 microns. in year. Acid rain can cause damage not only to metals, but also to buildings, monuments and other structures. Monuments built of limestone and sandstone are destroyed very quickly when exposed to acid rain. Contained in sandstones and limestones, CaCO 3, turning into calcium sulfate, is easily washed out by rainwater.

Currently, the main fuel in Estonia is fossil oil shale, which has a rather high sulfur content. However, due to its thermal use, basic oxides are also emitted into the atmosphere, which neutralize the acidic components. Therefore, the burning of shale does not cause acid rain. On the contrary, in North-East Estonia, alkaline precipitation falls, the pH of which can reach 9 or more units.

Ways to solve problems

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 in several ways, including by reducing the energy received by humans from burning fossil fuels and increasing the number of power plants using alternative energy sources(energy of sunlight, wind, tide energy). Other opportunities to reduce emissions of pollutants into the atmosphere are:

1. Reduction of sulfur content in various types of fuel. The most acceptable solution would be to use only those fuels that contain minimal amounts of sulfur compounds. However, there are very few such fuels. Only 20% of all world oil reserves have a sulfur content of less than 0.5%. And in the future, unfortunately, the sulfur content of the fuels used will increase as oil with low sulfur content is being produced at an accelerated rate. The same is true with fossil coals. The removal of sulfur from the fuel composition 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 composition, which is an insufficient amount.

2. The use of high pipes. This method does not reduce the impact on the environment, but increases the efficiency of mixing pollutants in higher layers of the atmosphere, which leads to 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. In addition, this method is very immoral, since the country in which these emissions occur transfers part of the consequences to other countries.

3. Technological changes. The amount of nitrogen oxides NO, which is formed during combustion, depends on the combustion temperature. In the course of the experiments carried out, it was possible to establish that the lower the combustion temperature, the less nitrogen oxide appears, moreover, the amount of NO depends on the time spent by the fuel in the combustion zone with excess air. Thus, appropriate changes in technology can reduce emissions. Reductions in sulfur dioxide emissions can be obtained by desulphurizing end gases. The most common method is the wet process, where the final gases are bubbled through a solution of limestone, resulting in the formation of calcium sulfite and sulfate. In this way, the greatest amount of sulfur can be removed from the final gases.

4. Liming. To reduce the acidification of lakes and soils, alkaline substances (CaCO 3) are added to them. This operation is very common in the Scandinavian countries, where lime is sprayed from helicopters onto the soil or into a catchment area. The Scandinavian countries are the most affected by acid rain, as most of the Scandinavian lakes have a granite or limestone-poor bed. 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 a number of disadvantages:

· In the flowing and rapidly mixing water of lakes, neutralization is not effective enough;

· 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;

· Heavy metals cannot be removed by liming. During the decrease in acidity, these metals turn into sparingly soluble compounds and precipitate, but when a new portion of acid is added, they dissolve again, thus representing a constant potential hazard to lakes.

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

Acid precipitation (rain) is one of the terms that arose as a result of industrialization.

Air pollution and acid rain

To date, there is a rapid development of industry: the expenditure of the planet's resources, the combustion of fuel, as well as the development of environmentally flawed technologies. This in turn leads to water and land. One such manifestation is acid precipitation.

The concept of acid rain was first mentioned in 1872, but it only became relevant in the second half of the last century. At the moment, acid precipitation is a serious problem for many countries of the world (practically all European countries and the USA). Ecologists have developed a rain map that clearly depicts areas with a high risk of hazardous rainfall.

Rainwater is characterized by a certain level of acidity. Under normal conditions, this index should correspond to a neutral pH level (from 5.6 - 5.7 and much higher). Slight acidity is the result. However, it is so low that it is not capable of harming living organisms. It turns out that the causes of acid precipitation are associated with human activities, natural factors cannot explain this.

Occurrence of acid precipitation

Acid residue is formed as a result of emissions of large amounts of nitrogen oxides and

The sources of such pollution are thermal power plants, metallurgical production and automobiles. The purification technology has a very low level of development, which does not allow filtering out nitrogen and sulfur compounds resulting from the combustion of peat, coal and other types of raw materials used in industry. Once in the atmosphere, oxides combine with water as a result of reactions under the action of sunlight. After that, they fall as rain, they are called "acid precipitation".

Effects of acid rain

Scientists say that acid precipitation is very dangerous for plants, people and animals. Below are the most important dangers:

Such rains significantly increase the acidity of all water bodies, whether it is a river, a pond or a reservoir. As a result, extinction of natural fauna and flora is observed. The ecosystem of water bodies is changing, they are becoming clogged, waterlogged, and silt is increasing. After such changes, the water is unfit for human use. It increases the amount of heavy metal salts and various toxic mixtures that are absorbed by the microflora of the reservoir under normal conditions.

These rains are a consequence of plant extinction and forest degradation. Coniferous trees get the most. The fact is that their leaves are very slowly updated, and this does not give them the opportunity to recover on their own after acid rain. Young forests are also subject to this process and their quality is rapidly declining. Excessive sediment mass leads to the destruction of forests.

In Europe and the US, acid rain is the biggest cause of poor harvests and the death of crops in the fields. The reason for the damage lies not only in the constant impact of rain, but also in violations of soil mineralization.

Architectural monuments, various buildings and structures also suffer from acid rain. As a result of this phenomenon, the corrosion process is significantly accelerated, the mechanisms fail.

In some cases, acid rain can cause irreparable harm to humans and animals. When they are in high-risk areas, they begin to worry about diseases of the upper respiratory tract. If this continues, then soon nitrate and black acid of an excessively high concentration will fall out. In this case, the threat to human life is significantly increased.

Fighting acid rain

Of course, you can't go against nature - it's unrealistic to deal with the precipitation itself. Falling out on fields and other large areas, acid precipitation causes irreparable harm, and there is no reasonable solution to this problem. It is quite another matter when it is necessary to eliminate not their consequences, but the causes of their appearance. To avoid the formation of acid rain, you need to constantly comply with a number of rules: environmentally friendly and safe road transport, special cleaning technologies, new production technologies, alternative energy sources, and so on.

Humanity has ceased. We all use the unlimited resources of our planet, pollute it and do not want to accept the consequences. But it is human activity that has brought the Earth to such a state. This is very dangerous, because if we do not start taking care of our planet, the consequences will become catastrophic.

Acid rain scares people for good reason: while the acidity of ordinary precipitation is 5.6, a drop in this level by only one tenth entails the death of many beneficial bacteria. And if it drops to 4.5, death to amphibians, insects and fish is guaranteed, and burn marks will appear on the leaves of plants.

A walk in such rain will also not bring benefits to the human body. At the same time, even going outside in the first few hours after acid precipitation is extremely harmful: inhaling toxic gases in the atmosphere may well cause asthma, serious lung and heart diseases.

Acid rain refers to all types of meteorological precipitation during which a strongly acidic reaction is observed, caused by a decrease in acidity due to air pollution with hydrogen chloride oxides of sulfur, nitrogen and other acid-forming compounds. According to scientists who study acid rain, this expression does not fully reflect the phenomenon, since in this case the term "acid precipitation" is more suitable, since toxic substances fall out both in the form of rain and hail, snow, fog, and even dust and gas in dry season.

It is worth noting that pH, which is an indicator of the acidity of aqueous solutions, can range from 0 to 14. While the acidity level of neutral liquids is seven, an acidic environment is characterized by indicators below this value, an alkaline environment is higher. In terms of rainfall, normal precipitation has a pH of 5.6 or slightly higher, depending on the region where it rains.

A small level of acidity is found in any rainwater, which is explained by the presence of carbon dioxide in the air, which, after interacting with raindrops, forms a weak carbonic acid. When the pH decreases by one, this means a tenfold increase in the concentration of acid, so rains below 5.3 are considered acidic (in Europe, the maximum recorded acidity of precipitation was pH 2.3, in China 2.25, in the Moscow region 2.15) .

As for the acidity level of ordinary rain, it is 5.6 or slightly higher. This acidity is low, and therefore does not bring any harm to plant and animal organisms. There is no doubt that acid precipitation began to fall on the earth's surface as a result of active human activity.

Precipitation

Speaking about the sources and causes of the formation of acid rain, experts first of all mention the activities of industrial enterprises that emit large amounts of sulfur and nitrogen oxides into the atmosphere (metallurgical production is especially harmful). Exhaust gases of numerous cars, thermal power plants also have their influence.

Unfortunately, at present, purification technologies do not allow filtering out harmful acidic compounds that are formed during the combustion of gas, peat, coal, oil and other types of relevant raw materials.

Therefore, the mechanism for the occurrence of acid rain is as follows: hydrogen chloride, sulfur and nitrogen oxides, once in the air, begin to interact with drops and solar radiation, forming various acidic compounds (nitric, sulphurous, sulfuric and nitrous acids).

After that, harmful compounds do not disappear anywhere and return to the earth in the form of precipitation. If they find themselves in an area where the atmosphere is saturated with moisture, they combine with water drops in the clouds, after which the dissolved acid falls out in the form of rain, hail, snow, fog, causing considerable harm not only to vegetation, but also to fauna: they are extracted from the soil as nutritious substances, as well as toxic metals such as aluminum, lead, etc.

If acid rain enters fresh water sources or reservoirs, the solubility of aluminum in the water increases dramatically, which leads to disease and death of fish, slower development of algae and phytoplankton, and the water becomes completely unsuitable for consumption.

If the air is absolutely dry, acid compounds can fall to the earth's surface in the form of dust or smog. Once on the earth's surface, they lie in wait for some time and, having waited for showers, go into the ground with the flow of water.

The death of the living world

After acid rain falls, the composition of the soil changes significantly, which causes the death of trees, vegetation and crops, and reduces soil fertility. Once in the ground, toxic water penetrates into reservoirs, as a result of which water is polluted and oxidized, which causes the death of almost all living beings (amphibians, fish and bacteria die at pH 4.5, and many representatives of the animal and plant world disappear even at lower acidity ).

The problem is greatly exacerbated in early spring during the snowmelt period: at this time, all pollutants accumulated during the winter are released and penetrate into the ground and water bodies, and fish fry and insect larvae are most vulnerable.

It is worth noting that before falling into the ground, acid rain lowers the purity of the air, negatively affects various structures, monuments, destroys building and facing (limestone, marble) materials, pipelines, dissolves paints, spoils cars, causing corrosion of metal surfaces.

The impact of acid rain has an extremely negative impact on both animate and inanimate nature, people and objects created by them. At the same time, toxic precipitation can cause such serious environmental problems as:

• The death of the flora and fauna of water bodies as a result of changes in the ecosystem. For humans, reservoirs as water sources also become completely unsuitable due to the increased amount of salts of heavy metals and various toxic compounds, which are normally absorbed by the microflora of the reservoir.
• The death of trees (especially conifers) due to damage to the leaves, roots, because of which they become defenseless against frost and various diseases.
• As a result of various chemical reactions, the soil partially loses trace elements and becomes less nutritious, which slows down the growth and development of vegetation (at the same time, a lot of toxic substances enter the tree through the roots).
• People living in areas where acid rain is common often have serious problems with their upper respiratory tract.
• Acid rains, eroding cement and negatively affecting facing and building materials, seriously damage architectural monuments, buildings and other structures, making them less durable.

How to prevent harmful precipitation?

Currently, the regions where the most acid precipitation is recorded are Asia (primarily China, whose industrial enterprises burn coal) and the United States of America. Given that rainfall tends to fall at some distance from where clouds form, Canada and Japan are also at risk.

Moreover, with the active growth of industry, the problem of acid rain is becoming more and more intense, and therefore, in the near future, the catastrophic consequences of such precipitation will definitely make themselves felt if scientists do not develop a scheme to prevent toxic precipitation before that.

Speaking about the fight against acid rain, it must be borne in mind that it is first of all necessary to fight the sources that caused the formation of acid rain, since it is impossible to fight the precipitation itself. In order to prevent the negative effects of toxic precipitation, environmentalists and scientists are studying acid rain causes and consequences, working on the development of technologies for the production and purification of atmospheric emissions, the creation of environmentally friendly sources of energy production, environmentally friendly vehicles, etc.

Until the governments of different countries, united, take up the solution of this problem and begin to look for ways out of the approaching ecological catastrophe, the problem will not be solved.

Given that acid rain, like other types of precipitation, can cover a huge area, in the near future acid rain may well become a common occurrence throughout the planet. At the same time, acidic compounds, having entered into additional chemical reactions, will not stop transforming, as a result of which sulfuric acid may soon begin to pour on the heads of careless passers-by.

Acid rain is a serious environmental problem, and its cause can be called universal environmental pollution. Frequent acid rains cause concern not only for scientists, but also for ordinary people, since such types of precipitation have a negative impact on health.

Acid rain is characterized by a low pH. Ordinary precipitation has a level of this indicator of 5.6. It should be noted that even with small deviations from the norm, the consequences for living organisms can be serious.

With significant shifts, a reduced level of acidity can cause the death of fish, as well as many insects and even amphibians. In addition, in areas where acid rain occurs, the presence of acid burns on the foliage of trees is sometimes noticed, and some plants even die off. The negative impact after acid rain has fallen can be felt by many people. Following such a downpour, accumulation of toxic gases in the atmosphere can occur, and it is extremely undesirable to breathe such a gas-air mass. The consequences will not be long in coming, even with a short walk during such precipitation, cardiovascular, bronchopulmonary diseases, and asthma may occur.

Can acid rain alone pose a threat?

The problem of acid rain has become more global in recent decades, so all the inhabitants of the Earth would do well to think about their role - positive or negative - in this natural phenomenon. You should know that most of the harmful substances that enter the air are a product of human life and practically do not disappear anywhere. Most of them remain in the atmosphere and will one day return to earth along with precipitation. And the very impact of acid rain is so serious that in some cases it may take more than one hundred years to eliminate the consequences.

In order to become more familiar with the possible consequences of acid rain, it is desirable to understand what the concept itself carries. Most scientists unanimously believe that such a formulation can be considered too narrow in order to capture the full potential of a global problem. One should not study exclusively rains, one should also pay attention to acid hail, fog and snowfall, which also belong to carriers of harmful substances and compounds, because their formation is mostly identical in terms of process. It should not be forgotten that with stable dry weather, toxic gases or dust clouds, or both, may appear. But these formations also belong to acid precipitation.

Causes of acid rain

Causes of acid rain are by and large directly dependent on the human factor. The constant pollution of the atmosphere with the use of acid-forming compounds (such as sulfur oxide, hydrogen chloride, nitrogen, etc.) leads to an imbalance. The most important producers of such substances are, of course, large industrial enterprises, for example, metallurgical, oil refineries, thermal power plants that burn coal or fuel oil. Despite filters and purification systems, modern technology has not yet reached the level that would allow to completely eliminate not only negative impacts, but also industrial waste itself.

In addition, there has been an increase in acid rain associated with the growth of vehicles on the planet. A large amount of exhaust gases, although in small doses, still contributes to the appearance of harmful acidic compounds. And if you recalculate the total number of vehicles, then the degree of pollution, one might say, has reached a critical level. In addition to all of the above, many household items also contribute, for example, aerosols, cleaners / detergents, etc.

Another cause of acid rain, apart from the human factor, may be some natural processes. In particular, volcanic activity can lead to their occurrence, during which a large amount of sulfur is ejected. Moreover, it is involved in the formation of gaseous compounds in the process of decomposition of individual organic substances, which in turn also leads to air pollution.

Mechanism of acid rain formation

All harmful substances that have been released into the atmosphere begin to react with elements of solar energy, carbon dioxide or water, resulting in the formation of acidic compounds. Together with the evaporation of moisture, they rise into the atmosphere, after which clouds form. Thus, the formation of acid rain occurs, the formation of snowflakes or hailstones, which will return to the earth everything that they have absorbed, along with other chemicals.

In some regions of the Earth, some deviations from the norm within 2-3 units were noted. So, with an acceptable acidity level of pH 5.6, in the Moscow region and China there were cases of precipitation with a pH level of 2.15. It is impossible to predict the exact location of acid rain, as it is possible that the clouds that have formed can be blown away by the wind for long distances from where the pollution occurred.

Composition of acid rain

The main components of acid rain are sulfuric and sulphurous acids, as well as the presence of ozone produced during thunderstorms. There are also nitrogen types of precipitation, in which nitric and nitrous acids are present as the main ones. Rarely, chlorine and methane can be the causes of acid rain. And, of course, other harmful substances may fall out with precipitation, based on what was in the composition of household and industrial waste emitted into the atmosphere in specific regions.

Why is acid rain dangerous?

Acid rains, together with their consequences, are the subject of constant observations, which are carried out by scientists from all countries. However, their forecasts are extremely disappointing. Precipitation, in which the pH level is lowered, poses a danger not only to people, but also to flora and fauna.

When it hits the ground, acid rain damages plants by depriving them of the nutrients they need to grow and develop. Among other things, toxic metals are drawn to the surface. With a high concentration of acids, trees can die due to precipitation, the soil becomes unusable for further crop cultivation, and it will take decades to restore it.

The same situation is with reservoirs. The composition of acid rain leads to an imbalance in the natural environment, after which the problem of river pollution arises. This, in turn, leads to the death of fish, and also slows down the growth of algae. Consequently, entire bodies of water, lakes and rivers may cease to exist for a long time.

Before hitting the ground, acid rain, passing by air masses, leaves particles of toxic substances in the atmosphere. This is considered extremely unfavorable, because it negatively affects the health of people and animals, and also significantly damages buildings. So most paint and varnish and facing materials, metal structures begin to dissolve as soon as drops of the ill-fated rain fall on them.

Global Environmental Issues of Acid Rain

Among the global environmental problems caused by acid rainfall can be:

• Changes in the ecosystem of water bodies that led to the death of flora and fauna. It will be impossible to use such sources for drinking, because heavy metals will exceed the norm many times over;
• Damage to the roots and leaves will lead to the destruction of protection against cold and disease. This is especially true for coniferous trees in severe frosts;
• Soil contamination with toxins. The plant world, located on the contaminated areas of the soil, will certainly weaken or die. Harmful elements will come along with useful substances, which will be less and less.

Harm of acid rain to people

The death of domestic animals, commercial fish species, crops - all this will, to one degree or another, affect the quality of life and the economy of any state.

Fish or animal meat can be hazardous to health when eaten in precisely those places where acid poisoning has occurred. Such meat may contain a critical content of toxic compounds or heavy metal ions. If it enters human bodies, it can lead to severe intoxication, serious liver or kidney disease, blockage of nerve channels, and the formation of blood clots. Some of the effects of acid poisoning may take generations to appear.

Ways to deal with acid precipitation

Today, the United States, China, and, of course, Russia are leading the main risk group for acid precipitation. Actually, in these states, the coal processing and metallurgical industries are highly developed and, accordingly, there are a large number of such enterprises. However, both Canada and Japan are considered dangerous, in the direction of which acid precipitation can be driven by the wind. According to some studies, if preventive measures are not taken, the list of such states may be replenished with many more candidates, and this will not have to wait long.

Fighting acid rain at the local level is almost useless. In order for the situation to change for the better, comprehensive measures must be taken. And they are possible only with the simultaneous and coordinated actions of many countries. Academic science is trying to find new purification systems to minimize emissions of harmful substances into the atmosphere, however, the percentage component of acid precipitation is only growing.

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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.

The reasons

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.