Natural sources of acid rain. Why is acid rain dangerous?
Ecology
Acid rain, which is described as sulfuric and nitric acids deposited in the atmosphere, is a serious environmental problem. Although it is often associated with rain, the term also refers to dry acidic substances. These acids are the result of sulfur dioxide and nitrogen oxide, which react with moisture and other substances in the atmosphere. Although there are natural springs these chemicals, experts are increasingly focusing on man-made sources such as coal-fired power plants.
What are the dangers of acid rain? Firstly, acid rain contributes to the acidification of soil, rivers and lakes, which exceeds the permissible limits for plants and animals, and it also destroys man-made structures. What other effects does acid rain have?
Oxidation of waters
Water resists rapid changes in pH, a measure of the acidity of a substance, which when low indicates more acidity. However, even this resistance can be overcome by constant and prolonged exposure to acid rain. Ecosystems of rivers and lakes are especially susceptible to such changes. For example, mayflies die at an acidity of pH 5.5, while trout and perch can survive in more acidic water. However, as populations of mayflies and other insects decline, those same trout will face insufficient food to support their populations. Also, at a pH of 5, many fish cannot hatch and raise young fish from eggs, which undermines the health of the fish population.
Forests
Direct contact with acid rain weakens trees and destroys their leaves. This is especially true for forests located on high altitude, where trees are often submerged in an acid cloud. Acid rain can also damage trees in a more subtle way, reducing nutrients and increasing levels of toxic compounds in the soil.
Cars
Many people work hard to improve the appearance of their car, but acid rain can literally destroy protective coating your vehicle. To combat these effects of acid rain, many car manufacturers have begun coating their cars with special acid-resistant paints.
Buildings
Limestone and marble structures are especially susceptible to acid rain. All this occurs due to the content of the mineral calcite in these materials, which is easily dissolved. Damage is easily visible on old stone buildings and monuments where the carvings have eroded over time. Not all stones are affected by this. Granite and sandstone have a chemical composition that does not react with acid rain, although some types of sandstone contain carbonate that the acid reacts with.
Human health
Acid rain looks like regular rain, without having any distinctive taste or causing any unusual sensations. The harm caused by acid rain to humans is not direct. Walking in acid rain, or even swimming in a lake exposed to acid rain, is no more dangerous than swimming in clear water. However, the pollutants that cause acid rain do cause harm to human health. Sulfur dioxide and nitrogen oxide react with the atmosphere to form pure sulfate and nitrogen particles, which are carried long distances by wind and inhaled into people's lungs. Small particles can also find their way into your home. Many studies have found a connection between increased level fine particles and the risk of illness and premature death from heart disorders and respiratory diseases such as asthma and bronchitis.
The only way to combat acid rain is to limit emissions of the pollutants that cause it. And even if at the very best scenario succeeded in stopping acid rain, it would take many years for the harmful effects of acid rain to completely disappear.
Acid rain is commonly called any precipitation(rain, snow, hail) containing any amount of acid. The presence of acids leads to a decrease in pH levels. pH value
Acid rain is usually called any precipitation (rain, snow, hail) containing any amount of acid. The presence of acids leads to a decrease in pH levels. Hydrogen index (pH) is a value that reflects the concentration of hydrogen ions in solutions. The lower the pH level, the more hydrogen ions in the solution, the more acidic the environment.
For rainwater, the average pH value is 5.6. In the case when the pH of precipitation is less than 5.6, they speak of acid rain. Compounds that lead to a decrease in the pH level of sediments are oxides of sulfur, nitrogen, hydrogen chloride and volatile organic compounds (VOCs).
Causes of acid rain
Acid rain, by nature of its origin, is of two types: natural (arising as a result of the activities of nature itself) and anthropogenic (caused by human activity).
Natural acid rain
Causes of acid rain naturally A little:
activity of microorganisms. A number of microorganisms in the process of their vital activity cause destruction organic matter, which leads to the formation of gaseous sulfur compounds, which naturally enter the atmosphere. The amount of sulfur oxides formed in this way is estimated at about 30-40 million tons per year, which is approximately 1/3 of the total amount;
Volcanic activity supplies another 2 million tons of sulfur compounds into the atmosphere. Together with volcanic gases, sulfur dioxide, hydrogen sulfide, various sulfates and elemental sulfur enter the troposphere;
decomposition of nitrogen-containing natural compounds. Since all protein compounds are based on nitrogen, many processes lead to the formation of nitrogen oxides. For example, the breakdown of urine. It doesn't sound very pleasant, but that's life;
lightning discharges produce about 8 million tons of nitrogen compounds per year;
burning of wood and other biomass.
Anthropogenic acid rain
Since we are talking about anthropogenic impact, there is no need to have great mind to guess what we're talking about destructive influence humanity on the state of the planet. A person is used to living in comfort, providing himself with everything he needs, but he’s not used to “cleaning up” after himself. Either he hasn’t grown out of the sliders yet, or he hasn’t matured enough in his mind.
The main cause of acid rain is air pollution. If thirty years ago as global causes, causing the appearance in the atmosphere, compounds that “oxidize” rain were called industrial enterprises and thermal power plants, today this list has been supplemented by road transport.
Thermal power plants and metallurgical enterprises “donate” about 255 million tons of sulfur and nitrogen oxides to nature.
Solid fuel rockets have also made and continue to make a significant contribution: the launch of one Shuttle complex results in the release of more than 200 tons into the atmosphere hydrogen chloride, about 90 tons of nitrogen oxides.
Anthropogenic sources of sulfur oxides are enterprises producing sulfuric acid and refining oil.
Exhaust gases road transport– 40% of nitrogen oxides entering the atmosphere.
The main source of VOCs in the atmosphere is, of course, chemical production, oil storage facilities, gas stations and gas stations, as well as various solvents used both in industry and in everyday life.
The final result is as follows: human activity supplies the atmosphere with more than 60% of sulfur compounds, about 40-50% of nitrogen compounds and 100% of volatile organic compounds.
From a chemical point of view, there is nothing complicated or incomprehensible about the formation of acid rain. Oxides entering the atmosphere react with water molecules, forming acids. Sulfur oxides, when released into the air, form sulfuric acid, and nitrogen oxides form nitric acid. One should also take into account the fact that in the atmosphere above major cities always contain particles of iron and manganese, which act as catalysts for reactions. Since there is a water cycle in nature, water in the form of precipitation sooner or later falls on the earth. Acid also gets in with the water.
Consequences of acid rain
The term "acid rain" first appeared in the second half of the 19th century and was coined by British chemists working on the pollution of Manchester. They noticed that significant changes in rainwater are caused by vapors and smoke released into the atmosphere as a result of the activities of enterprises. As a result of the research, it was discovered that acid rain causes discoloration of fabrics, metal corrosion, destruction of building materials and leads to the death of vegetation.
It took about a hundred years before scientists around the world sounded the alarm about harmful effects acid rain. This problem was first raised in 1972 at the UN conference on the environment.
Oxidation water resources. Rivers and lakes are the most sensitive. Fish die. Despite the fact that some species of fish can withstand slight acidification of water, they also die due to the loss of food resources. In those lakes where the pH level was less than 5.1, not a single fish was caught. This is explained not only by the fact that adult fish die - at a pH of 5.0, most cannot hatch fry from the eggs, as a result of which there is a reduction in the numerical and species composition of fish populations.
Harmful effects on vegetation. Acid rain affects vegetation cover directly and indirectly. Direct impact occurs in high mountain areas where tree crowns are literally immersed in acidic clouds. Unnecessarily sour water destroys leaves and weakens plants. Indirect impact occurs due to a decrease in the level of nutrients in the soil and, as a result, an increase in the proportion of toxic substances.
Destruction of human creations. Building facades, cultural and architectural monuments, pipelines, cars - everything is exposed to acid rain. Many studies have been conducted, and they all say one thing: acid rain exposure has increased significantly over the past three decades. As a result, not only marble sculptures and stained glass windows of ancient buildings are under threat, but also leather and paper products of historical value.
Human health. Acid rain itself does not have a direct impact on human health - if you get caught in such rain or swim in a reservoir with acidified water, you do not risk anything. Compounds that form in the atmosphere due to the ingress of sulfur and nitrogen oxides into the atmosphere pose a threat to health. The resulting sulfates are transported air currents over considerable distances, are inhaled by many people, and, as studies show, provoke the development of bronchitis and asthma. Another point is that a person eats the gifts of nature; not all suppliers can guarantee the normal composition of food products.
Solving the problem
Because this problem wears global character, then it can only be solved together. The real solution will be to reduce emissions from enterprises, both into the atmosphere and into water. There are only two possible solutions: stopping the activities of enterprises or installing expensive filters. There is a third solution, but it is only in the future - the creation of environmentally friendly industries.
The words that every person should be aware of the consequences of their actions have long been set on edge. But you can’t argue with the fact that the behavior of society is made up of the behavior of individual individuals. The difficulty is that people are accustomed to separating themselves from humanity in environmental matters: the air is polluted by enterprises, toxic waste fall into the water due to unscrupulous firms and companies. They are them, and I am me.
Household aspects and individual paths problem solving
Strictly follow the rules for disposing of solvents and other substances containing toxic and harmful chemical compounds.
Give up cars. Maybe? – hardly.
Not everyone can influence the installation of filters or the introduction of alternative production methods, but observing environmental culture and raising the younger generation to be environmentally literate and cultural is not only possible, it should become the norm of behavior for every person.
No one is surprised by the many books and films devoted to the results of man’s technogenic impact on nature. The films depict the dead surface of the planet, the struggle for survival and various mutant life forms in a colorful and frighteningly realistic manner. Fairy tale, fiction? - quite real perspective. Think about it, not so long ago space flights seemed like a fiction, engineer Garin’s hyperboloid (modern laser systems) - fantasy.
When thinking about the future of planet Earth, it is worth thinking not about what awaits humanity, but about the kind of world in which children, grandchildren and great-grandchildren will live. Only personal interest can motivate a person to take real steps.
Everyone knows what water is. Her on Earth huge amount- one and a half billion cubic kilometers.
If you imagine Leningrad region the bottom of a giant glass and try to contain all the water of the Earth in it, then its height should be greater than the distance from the Earth to the Moon. It would seem that there is so much water that there should always be enough of it. But the trouble is that all oceans have salty water. We, and almost all living things, need fresh water. But there isn't much of it. That's why we desalinate water.
IN fresh water rivers and lakes contain many soluble substances, including toxic ones, which may contain pathogenic microbes, so you can’t use it, much less drink it, without additional cleaning. When it's raining, drops of water (or snowflakes, when it's snowing) capture harmful impurities from the air that have entered it from the pipes of some factory.
As a result, harmful, so-called acid rain falls in some places on Earth. Neither plants nor animals like it.
The beneficial drops of rain have always brought joy to people, but now in many areas of the planet, rain has turned into a serious danger.
Acid precipitation (rain, fog, snow) is precipitation whose acidity is higher than normal. A measure of acidity is the pH value (hydrogen value). The pH scale goes from 02 (extremely acidic), through 7 (neutral) to 14 (alkaline), with the neutral point ( clean water) has pH=7. Rain water in clean air has pH=5.6. The lower the pH value, the higher the acidity. If the acidity of the water is below 5.5, then the precipitation is considered acidic. In vast areas industrially developed countries Around the world there is precipitation, the acidity of which exceeds normal by 10 - 1000 times (pH = 5-2.5).
Chemical analysis acid precipitation indicates the presence of sulfuric (H 2 SO 4) and nitric (HNO 3) 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 is released into the air, and atmospheric nitrogen also reacts with atmospheric oxygen to form nitrogen oxides.
These gaseous products (sulfur dioxide and nitrogen oxide) react with atmospheric water with the formation of acids (nitric and sulfuric).
In aquatic ecosystems, acid precipitation causes the death of fish and other aquatic life. Acidification of water in rivers and lakes seriously affects land animals, since many animals and birds are part of food chains, starting in aquatic ecosystems.
Along with the death of lakes, forest degradation also becomes apparent. Acids destroy the protective waxy coating of leaves, making plants more vulnerable to insects, fungi and other pathogens. During drought, more moisture evaporates through damaged leaves.
The leaching of nutrients from the soil and the release of toxic elements contribute to the slowdown of tree growth and death. One can imagine what happens to wild animal species when forests die.
If the forest ecosystem is destroyed, soil erosion begins, clogging of water bodies, flooding and deterioration of water supplies become catastrophic.
As a result of acidification in the soil, nutrients vital to plants are dissolved; These substances are carried by rain into groundwater. At the same time, heavy metals are leached from the soil, which are then absorbed by plants, causing serious damage to them. Using such plants for food, a person also receives an increased dose of heavy metals with them.
When it degrades soil fauna, yields are declining, the quality of agricultural products is deteriorating, and this, as we know, entails a deterioration in the health of the population.
Under the influence of acids from rocks and minerals, aluminum is released, as well as mercury and lead. which then end up in surface and groundwater. Aluminum can cause Alzheimer's disease, a type of premature aging. Heavy metals found in natural waters, negatively affect the kidneys, liver, central nervous system, causing various oncological diseases. Genetic consequences heavy metal poisoning can take 20 years or more to appear not only in those who consume dirty water, but also among their descendants.
Acid rain corrodes metals, paints, synthetic compounds, and destroys architectural monuments.
Acid rain is most common in industrialized countries with highly developed energy systems. Over the course of a year, thermal power plants in Russia emit about 18 million tons of sulfur dioxide into the atmosphere, and in addition, thanks to western air transport, sulfur compounds come from Ukraine and Western Europe.
To combat acid rain, efforts must be directed toward reducing emissions of acid-forming substances from coal-fired power plants. And for this you need:
using low-sulfur coal or removing sulfur from it
installation of filters for purification of gaseous products
use of alternative energy sources
Most people remain indifferent to the problem of acid rain. Are you going to wait indifferently for the destruction of the biosphere or are you going to take action?
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 from burning fossil fuels and increasing the number of power plants using alternative energy sources (energy sunlight, wind, tidal energy). Other opportunities to reduce emissions of pollutants into the atmosphere are:
- 1. Reduction of sulfur content in various types 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 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 low content sulfur is extracted at an accelerated pace. The same is true with fossil coals. Removing sulfur from fuels has proven to be a very expensive process in financially 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 impact on environment, but increases the efficiency of mixing pollutants in higher layers of the atmosphere, which leads to acid precipitation in more distant 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 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;
Happening gross violation chemical and biological balance waters and soils;
It is not possible to eliminate all the harmful effects of acidification;
Liming cannot remove heavy metals. During a decrease in acidity, these metals turn into poorly soluble compounds and precipitate, but when a new portion of acid is added, they dissolve again, thus representing a constant potential danger to 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.
Acid rain was first noted in Western Europe, particularly Scandinavia, and North America in the 1950s. This problem now exists throughout the industrial world and has become special meaning due to increased technogenic emissions of sulfur and nitrogen oxides. Over the course of several decades, the scope of this disaster has become so wide and negative consequences so great that in 1982 a special international conference on acid rain, which was attended by representatives of 20 countries and a number of international organizations. To this day, the severity of this problem remains, it is constantly in the spotlight 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 over 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 began to occur 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, about 60 tons of sulfur fall per year in the form of acid precipitation. In tropical areas, 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 air currents over long distances - hundreds and even thousands of kilometers. This is greatly facilitated by the once adopted “high pipe policy” as effective remedy against ground air pollution. Almost all countries are simultaneously “exporters” of their own and “importers” of others’ 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 slight distance from it.
Exchange acid-forming and other air polluting emissions are typical for all countries of Western Europe and North America. Great Britain, Germany, and France send more oxidized sulfur to their neighbors than they receive from them. Norway, Sweden, and 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 Great Britain and Germany). Transboundary transport of acid precipitation is one of the reasons for the conflictual relationship between the United States 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 into acid-forming particles in the earth's atmosphere. These particles react with atmospheric water, turning it into acid solutions, which lower the pH of rainwater. The term “acid rain” was first coined in 1872 by English explorer Angus 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 leaking into aquifers.
Water regular rain is also a weakly acidic solution. This occurs because natural atmospheric substances 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 acidity of rainwater in one area may be different from the acidity 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.
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 is released into the air, and atmospheric nitrogen also reacts with atmospheric oxygen to form nitrogen oxides.
As already mentioned, any acidity level has a certain level rainwater. But in the normal case, this indicator corresponds to a neutral pH level - 5.6-5.7 or slightly higher. The slight acidity is due to the content in the air carbon dioxide, but is considered so low that it does not cause any harm to living organisms. Thus, the causes of acid rain are solely due to 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, modern level The development of purification technologies does not allow filtering out nitrogen and sulfur compounds that arise as a result of 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 influence of sunlight, and fall to the ground in the form of precipitation, which is called “acid rain.”