What causes the destruction of the ozone layer briefly. The ozone layer of the Earth was pierced by ozone holes: is humanity facing a global catastrophe? Destruction of the ozone layer: ways to solve the problem

MINISTRY OF EDUCATION AND SCIENCE

RUSSIAN FEDERATION

Voronezh State University

Faculty of Biology and Soil

Department of Botany and Mycology

Destruction of the ozone layer

020201 - biology

Abstract work

Head of the Department Associate Professor, Doctor of Biology: Agafonov V.A.

Student: Bykovskaya T.G.

Lecturer: Negrobov V.V.

Voronezh 2010

Introduction.

Ozone, located at a height of about 25 km from the earth's surface, is in a state of dynamic equilibrium. It is a layer of increased concentration with a thickness of about 3 mm. Stratospheric ozone absorbs the harsh ultraviolet radiation of the Sun and thus protects all life on Earth. Ozone also absorbs the infrared radiation of the Earth and is one of the prerequisites for the preservation of life on our planet.

The 20th century brought to mankind many benefits associated with the rapid development of scientific and technological progress, and at the same time put life on Earth on the brink of an ecological catastrophe. Population growth, intensification of production and emissions that pollute the Earth, lead to fundamental changes in nature and are reflected in the very existence of man. Some of these changes are extremely strong and so widespread that global environmental problems arise.

As a result of many external influences, the ozone layer begins to thin out in comparison with its natural state, and under certain conditions it disappears completely over certain territories - ozone holes appear, fraught with irreversible consequences. At first they were observed closer to the south pole of the Earth, but have recently been seen over the Asian part of Russia. The weakening of the ozone layer increases the flow of solar radiation to the earth and causes an increase in the number of skin cancers and a number of other serious diseases in people. Plants and animals also suffer from increased levels of radiation.

Although mankind has taken various measures to restore the ozone layer (for example, under pressure from environmental organizations, many industrial enterprises have gone to additional costs to install various filters to reduce harmful emissions into the atmosphere), this complex process will take several decades. First of all, this is due to the huge volume of substances already accumulated in the atmosphere that contribute to its destruction. Therefore, I believe that the problem of the ozone layer remains relevant in our time.

Chapter 1.

The nature and significance of the ozone screen.

Along with visible light, the sun emits ultraviolet waves. Ultraviolet radiation is similar to light, but its wavelength is somewhat shorter than that of violet waves, the shortest wavelengths perceived by the human eye. Although ultraviolet rays are invisible, they have more energy than visible ones. Penetrating through the atmosphere and being absorbed by the tissues of living organisms, they destroy the molecules of proteins and DNA. This is what happens when you tan. If all the ultraviolet radiation that hits the upper atmosphere reached the surface of the Earth, then life would hardly have survived on it. Even a small, available to us part of this amount (less than 1%) causes sunburn and annually 200,000-600,000 cases of skin cancer in the United States.

We are protected from the aggressive effects of ultraviolet radiation, since most of it (over 99%) is absorbed by the ozone layer in the stratosphere at an altitude of about 25 kilometers from the earth's surface. This layer is commonly referred to as the ozone layer.

When ultraviolet radiation is absorbed in the atmosphere, a kind of mixture is formed in which free electrons, neutral oxygen atoms, and positive ions of oxygen molecules predominate. When they interact, ozone is formed. The interaction of ultraviolet radiation with oxygen occurs throughout the entire height of the atmosphere - there is evidence that in the mesosphere, at an altitude of 50 to 80 kilometers, the process of ozone formation is already observed, which continues in the stratosphere (from 15 to 50 km) and in the troposphere (up to 15 km ). At the same time, the upper layers of the atmosphere, in particular the mesosphere, are exposed to such a strong effect of short-wave ultraviolet radiation that the molecules of all the gases that make up the atmosphere are ionized and decay. The ozone that has just formed there cannot but decompose, especially since this requires almost the same energy as for oxygen molecules. Nevertheless, it is not completely destroyed - part of the ozone, which is 1.62 times heavier than air, descends into the lower layers of the atmosphere to a height of 20-25 kilometers, where the density of the atmosphere allows it to be, as it were, in an equilibrium state. There, ozone molecules create a layer of increased concentration, that is, the ozone layer.

The ozone layer is surprisingly thin. If this gas were concentrated near the Earth's surface, it would form a film only 2-4 mm thick (minimum - in the equator region, maximum - at the poles). However, this film also reliably protects us, almost completely absorbing dangerous ultraviolet rays. Without it, life would have survived only in the depths of water (deeper than 10 m) and in those layers of soil where solar radiation does not penetrate. Moreover, if it were not for the ozone layer, then life would not be able to get out of the oceans at all and highly developed life forms such as mammals, including humans, would not have arisen. Ozone absorbs some of the Earth's infrared radiation. Due to this, it delays about 20% of the Earth's radiation, increasing the warming effect of the atmosphere. Ozone also regulates the hardness of cosmic radiation. If this gas is at least partially destroyed, then, naturally, the hardness of the radiation increases sharply, and, consequently, real changes in the plant and animal world occur. According to doctors, every percent of ozone lost globally causes up to 150,000 additional cases of blindness due to cataracts, a 2.6 percent increase in the number of skin cancers, and a significant increase in the number of diseases caused by a weakened human immune system. Fair-skinned people in the northern hemisphere are most at risk. But it's not just people who suffer. UV-B radiation, for example, is extremely harmful to plankton, fry, shrimp, crabs, algae that live on the surface of the ocean.

Chapter 2

Formation and destruction of the ozone layer.

As already mentioned, ozone in the stratosphere is a product of the action of ultraviolet (UV) itself on oxygen molecules (O2). As a result, some of them break down into free atoms, which in turn can join other oxygen molecules to form ozone (O3). However, all oxygen does not turn into ozone, since free O atoms, reacting with ozone molecules, give two O2 molecules. Thus, the amount of ozone in the stratosphere is not static; it is the result of an equilibrium between these two reactions. Ozone depletion is the separation of ozone molecules caused by stratospheric ozone depleting substances (OSNVs), natural processes (e.g. volcanic eruptions) or emitted (released) by human activities that contain chlorine (Cl) or bromine (Br); as well as methane or nitric oxide (I) - (N2O).

The most significant stages of the destruction of the ozone layer:

1) Emissions: as a result of human activity, as well as as a result of natural processes on Earth, gases containing halogens (bromine and chlorine) are emitted (released), i.e. substances that deplete the ozone layer.

2) Accumulation (emitted gases containing halogens accumulate (accumulate) in the lower atmospheric layers, and under the influence of wind and air flows move to regions that are not in direct proximity to the sources of such gas emissions).

3) Movement (accumulated gases containing halogens move into the stratosphere with the help of air currents).

4) Transformation (most of the gases containing halogens, under the influence of ultraviolet radiation from the Sun in the stratosphere, are converted into easily reacting halogen gases, as a result of which the destruction of the ozone layer in the polar regions of the globe is relatively more active).

5) Chemical reactions (easily reacting halogen gases cause the destruction of stratospheric ozone; the factor contributing to the reactions is polar stratospheric clouds).

6) Removal (under the influence of air currents, easily reacting halogen gases return to the troposphere, where, due to the moisture and rain present in the clouds, they are separated, and thus completely removed from the atmosphere).

Chapter 3

Causes of the destruction of the ozone layer.

In the 1970s, scientists hypothesized that free chlorine atoms catalyze the separation of ozone. And people annually replenish the composition of the atmosphere with free chlorine and other harmful substances. Moreover, a relatively small number of them can cause significant damage to the ozone screen, and this influence will continue indefinitely, since chlorine atoms, for example, leave the stratosphere very slowly.

Most of the chlorine used on earth, for example for water purification, is represented by its water-soluble ions. Consequently, they are washed out of the atmosphere by precipitation long before they enter the stratosphere. Chlorofluorocarbons (CFCs) are highly volatile and insoluble in water. Consequently, they are not washed out of the atmosphere and, continuing to spread in it, reach the stratosphere. There they can decompose, releasing atomic chlorine, which actually destroys ozone. Thus, CFCs cause damage by acting as carriers of chlorine atoms into the stratosphere.

CFCs are relatively chemically inert, non-flammable, and toxic. Moreover, being gases at room temperature, they are burned at a slight pressure in the release of heat, and evaporating, they absorb it again and cool. These properties allowed them to be used for the following purposes.

1) Chlorofluorocarbons are used in almost all refrigerators, air conditioners and heat pumps as chlorine agents. Because these fixtures eventually break down and are discarded, the CFCs they contain usually end up in the atmosphere.

2) The second most important area of their application is the production of porous plastics. CFCs are mixed into liquid plastics at elevated pressure (they are soluble in organic matter). When the pressure is released, they froth the plastic like carbon dioxide froths soda water. And at the same time they escape into the atmosphere.

3) The third main area of their application is the electronics industry, namely the cleaning of computer chips, which must be very thorough. Again, CFCs are released into the atmosphere. Finally, in most countries except the US, they are still used as carriers in aerosol cans that spray them into the air.

A number of industrial countries (for example, Japan) have already announced the abandonment of the use of long-lived freons and the transition to short-lived freons, whose lifetime is significantly less than a year. However, in developing countries, such a transition (requiring the renewal of a number of areas of industry and economy) encounters understandable difficulties, therefore, in reality, one can hardly expect a complete cessation of the emission of long-lived freons in the foreseeable decades, which means that the problem of preserving the ozone layer will be very acute.

VL Syvorotkin developed an alternative hypothesis, according to which the ozone layer is decreasing due to natural causes. It is known that the cycle of ozone destruction by chlorine is not the only one. There are also nitrogen and hydrogen cycles of ozone destruction. It is hydrogen - "the main gas of the Earth." Its main reserves are concentrated in the core of the planet and enter the atmosphere through a system of deep faults (rifts). According to approximate estimates, there is tens of thousands of times more natural hydrogen than chlorine in technogenic freons. However, the decisive factor in favor of the hydrogen hypothesis is Syvorotkin V.L. believes that the centers of ozone anomalies are always located above the centers of hydrogen degassing of the Earth.

The destruction of ozone also occurs due to exposure to ultraviolet radiation, cosmic rays, nitrogen compounds, bromine. Human activities that deplete the ozone layer are of the greatest concern. Therefore, many countries have signed an international agreement to reduce the production of ozone-depleting substances. However, the ozone layer is also destroyed by jet aircraft and some launches of space rockets. There are many other reasons for the weakening of the ozone shield. Firstly, these are the launches of space rockets. Burning fuel “burns out” large holes in the ozone layer. It was once assumed that these "holes" were being closed. It turned out not. They have been around for quite some time. Secondly, aircraft flying at altitudes of 12-15 km. The steam and other substances emitted by them destroy ozone. But, at the same time, planes flying below 12 km give an increase in ozone. In cities, it is one of the components of photochemical smog. Thirdly, nitrogen oxides. They are thrown out by the same planes, but most of all they are released from the soil surface, especially during the decomposition of nitrogen fertilizers.

Steam plays a very important role in ozone depletion. This role is realized through hydroxyl molecules OH, which are born from water molecules and finally turn into them. Therefore, the rate of ozone destruction depends on the amount of steam in the stratosphere.

Thus, there are many reasons for the destruction of the ozone layer, and despite all its importance, most of them are the result of human activity.

Chapter 4

Ozone holes and their influence.

The ozone hole is a local drop in the concentration of ozone in the ozone layer of the Earth. Until recently, the state of the ozone layer did not inspire concern. The alarms started coming in 20 years ago. With the beginning of space studies of the Earth's atmosphere in the fall of 1985, a violation of the ozone layer over Antarctica was discovered. It turned out that during the Antarctic spring, the level of ozone in the atmosphere there is much lower than normal. Every year at the same time, the amount of ozone decreased - sometimes to a greater extent, sometimes to a lesser extent.

In subsequent years, scientists figured out why the ozone hole appears. When the sun hides and the long polar night begins, there is a sharp drop in temperature, and high stratospheric clouds form, containing ice crystals. The appearance of these crystals causes a series of complex chemical reactions leading to the accumulation of molecular chlorine (the chlorine molecule consists of two connected chlorine atoms). When the sun appears and the Antarctic spring begins, under the action of ultraviolet rays, intramolecular bonds are broken, and a stream of chlorine atoms rushes into the atmosphere. These atoms act as catalysts for the conversion of ozone into simple oxygen. As a result of these reactions, ozone molecules (O3) are converted into oxygen molecules (O2), while the original chlorine atoms remain in a free state and again participate in this process (each chlorine molecule destroys a million ozone molecules before they are removed from the atmosphere by the action of others). chemical reactions). As a result of this chain of transformations, ozone begins to disappear from the atmosphere over Antarctica, forming an ozone hole. However, soon, with warming, the Antarctic vortices collapse, fresh air (containing new ozone) rushes into the area, and the hole disappears.

In February 1989, scientists examined the stratosphere over the Arctic and found the presence of the same chemical factors. They came to the conclusion that here, too, the ozone content could drop sharply. It will depend only on the specific weather conditions of the next year. If an ozone hole forms over the Arctic, the consequences will be much more serious, because. there are many more organisms that can be affected. Even the periodic opening of such a hole over Antarctica is fraught with significant losses of marine phytoplankton. And this, in turn, will greatly affect almost all Antarctic animals from penguins to whales, since phytoplankton are the basis of almost all food chains in this region. If the current emissions of CFCs into the atmosphere continue, then we can only expect the expansion and "deepening" of the ozone holes above the poles. Naturally, this will entail rarefaction of the ozone layer over the entire planet, which is completely unacceptable both for the animal world and for all mankind as a whole.

However, there is another point of view. Where do ozone holes come from far from man-made regions, for example, in Yakutia, Tibet and over the deserted territories of Siberia? There is an opinion that changes in atmospheric circulation are caused by stationary planetary waves that penetrate the stratosphere in the winter-spring period, strongly affecting the distribution of ozone and its other components in middle and high latitudes. One of the sources of these waves is different temperatures over the surfaces of continents and oceans, so changes in ocean surface temperature affect wave activity. With a long-term weakening of wave activity, westerly winds increase in the stratosphere, its lower part cools, polar stratospheric clouds form and, thus, conditions for ozone destruction. The circulation in the stratosphere over the past 20 years could have changed a lot. So the main cause of the ozone "hole" in the Antarctic may well be a long-term weakening of the wave activity of the stratosphere, associated with very slow processes in the oceans.

Comparing the changes in the wave activity of the stratosphere and the ozone content in 1979-1992, the experts concluded that the weakening of activity corresponds to a decrease in the ozone concentration in the middle and high latitudes due to a smaller interlatitudinal exchange. It seems that in the summer of 1980 the circulation in the stratosphere changed dramatically and the conditions for the formation of an ozone "hole" arose.

Recently, the appearance of ozone holes has been observed periodically over the entire surface of the earth. In addition, the ozone layer of the Earth itself is thinning. For a person, this threatens to increase skin cancers. But if a person can protect himself from ultraviolet radiation, then the animal and plant world remains defenseless before him.

Scientists are looking for ways to restore the ozone layer. Initially, for this purpose, it was proposed to create factories for the production of ozone, after which it would be delivered by aircraft into the atmosphere. Another option is to build laser-powered, solar-powered balloons that use oxygen to create ozone. The most realistic way out of this situation is to reduce deforestation and increase green spaces.

Conclusion.

The problem of the ozone layer is one of the global problems of our time. As you know, life on Earth appeared only after the protective ozone layer of the planet was formed, covering it from cruel ultraviolet radiation. That is why, in order to protect the ozone screen, many different conferences and symposiums were convened, as a result of which certain agreements were reached in the field of reducing harmful industries. In particular, on March 22, 1985, the Vienna Convention for the Protection of the Ozone Layer was adopted, in which the countries participating in the convention agreed on the need to conduct systematic and fundamental research related to the ozone layer, to include in the legislation requirements to reduce and eliminate the emission of substances that destroy the ozone layer, as well as to create a special international institution to promote and coordinate the protection of the ozone layer - the Ozone Secretariat. At a meeting in Helsinki in 1989, it was planned to completely eliminate the use of chlorofluorocarbons in the production by the year 2000. However, the problem is not as simple as it might seem at first glance. The fact is that already produced refrigerators and air conditioners have accumulated too much CFC: as they normally fail, the amount of harmful gases in the atmosphere will continue to increase for many years to come, even in the event of a complete and immediate ban on production.

For continued success, the following steps are needed:
1) Continue monitoring the ozone layer to quickly track unforeseen changes; to ensure the implementation by the countries of the adopted agreements;

2) Continue work to identify the causes of changes in the ozone layer and evaluate the harmful properties of new chemicals in relation to ozone depletion and the impact on climate change in general;
3) Continue to provide information on technologies and substitute compounds that enable refrigeration, air conditioning and thermal insulation foams to be used without damaging the ozone layer.

Bibliography.

1. Nebel B., Science of the environment, V.1 (How the world works), M., 1993

2. Gvishiani D.M., Club of Rome. History of creation, selected reports and speeches, official materials, M., 1997

3. Mikael P. Todaro, Economic development, M., 1997

4. http://www.cross.ru/soc/parn.shtml

5. http://www.germany.org.ru/ger_10.html

6. http://www.meteo.lv/public/27110.html

Many inhabitants of the planet know about the ozone layer of the Earth only that a huge hole has appeared in it, and this threatens with a universal catastrophe. Every now and then articles appear in newspapers and magazines where people are frightened by potential problems. Scientists are talking about the coming climate change, which will negatively affect all life on Earth. Is it really? Is it worth worrying now, and are scientists not exaggerating the magnitude of the coming disaster? Is the destruction of the ozone layer threatening us in the near future, and how can this affect the climate? Let's try to figure everything out.

Where is located

So, for starters, let's figure out what ozone is and what role it plays in nature. Above the Earth's surface, at an altitude of seven to nineteen kilometers, the atmosphere consists of a layer of ozone. It is a special form of oxygen. Moreover, at the poles it is located lower - at an altitude of 7-8 kilometers, and at the equator - much higher, at a distance of 17-18 kilometers from the earth's surface. Thus, it is distributed very unevenly.

If we analyze ozone from the point of view of chemical reactions, we get the following picture. Due to the strong action of the ultraviolet radiation of the Sun, the oxygen molecule that makes up the air shell of the earth has attached a third oxygen atom to itself. This is how ozone came about.

important purpose

It is worth noting that a large amount of ozone in the atmosphere is a huge plus for our Earth. The more it is, the better it absorbs ultraviolet rays. Actually, this is its main purpose. However, do not think that the ozone layer of the atmosphere is a thick pillow that reliably shelters the Earth from the hot rays of the Sun.

No. The ozone layer is very, very thin. So that you can visually imagine its scale, you can give an example. We take an area of 45 square kilometers. If all the ozone available in the Earth's atmosphere is evenly distributed over it, then its thickness will be ... only 0.3 cm. This seems incredible! How has such a thin protective “cloak” protected mankind from the hot sun for many millennia? However, it is.

Given the importance of the ozone layer and its relatively small amount, every effort must be made to keep the protection intact. After all, to destroy it - a lot of mind is not needed, but it is almost impossible to restore it.

Smells like ozone

Sometimes after rain, especially summer, the air becomes especially fresh, pleasant, and people say: "It smells like ozone." This is by no means a figurative expression. Indeed, a certain amount of ozone partially penetrates into the lower layers of the atmosphere with the currents of the upper air. This is the so-called useful ozone. It also gives the atmosphere an unusual freshness. Often this phenomenon can be observed after thunderstorms.

But there is also a very harmful, extremely dangerous ozone for humans. Exhaust gases and industrial emissions, falling under the action of sunlight, enter into a photochemical reaction. As a result, the so-called ground-level ozone is formed. It is very harmful to human health. Most often, such ozone is found in metropolitan areas and large cities. It is extremely dangerous to breathe such air, since this gas adversely affects the bronchi and lungs and destroys them. If a person inhales such air, he may experience asthma attacks, chest pains, heart attacks, dizziness.

Not only people suffer from such a bad ecological situation, but also plants along the roads. But at high altitudes, the importance of the ozone layer is difficult to overestimate. If it weren't for it, humanity would have already burned out from ultraviolet radiation.

A hole the size of a mainland

The ozone layer of the earth was discovered by scientists in the 70s of the twentieth century. At the same time, physicists determined its value and described it in scientific papers. But just a decade and a half later, researchers faced the global problem of the ozone layer. British scientists in 1985 made a discovery that frightened the whole world and forced to take a different look at the development of modern industry.

Over Antarctica, researchers have discovered a huge "hole". The ozone layer over this continent was completely absent. Moreover, the hole was terrifying in size - the size of the United States.

It was experimentally found that in the atmosphere above the coldest continent of the Earth, compounds are present in large quantities, which are formed during the interaction of ozone and chlorine. Thus, the theory that chlorine destroys ozone was confirmed.

Dangerous freons

Scientists have proven that freons, which are massively used in refrigerators and air conditioners, as well as in numerous aerosol cans, adversely affect the ozone layer. It just seems to us that we sprayed our hair with varnish, and nothing terrible happened. But imagine that such micro-emissions are carried out per day by millions of consumers! Now the scale is looming as each of us destroys the ozone layer!

The reasons for the destruction are that freon molecules interact with ozone molecules. Solar radiation causes freons to release chlorine. It splits ozone, resulting in the formation of atomic and ordinary oxygen. In the place where this interaction occurs, the ozone layer completely disappears.

Of course, industrial emissions bring the greatest harm to the ozone layer. But the household use of drugs that contain freon, one way or another, also has an impact on the destruction of ozone.

Protective measures

After scientists documented that the ozone layer was being destroyed, politicians began to think about how to save it. After all, this is important not for a single country, but for all of humanity as a whole. A series of consultations and meetings on this issue took place around the world, in which representatives of all countries where industry is developed took part.

In 1985, the Convention for the Protection of the Ozone Layer was adopted. It was signed by representatives of 44 states. A year later, another important document was signed - the Montreal Protocol. According to its provisions, the production and consumption of substances that destroy ozone were significantly limited in the world.

Some tried to oppose these prohibitions. But for each country, clear quotas for hazardous industries were determined, which cannot be exceeded. After all, the fate of all mankind is at stake.

Protection of the ozone layer in Russia

In our country, this problem is also given great attention. According to the current legislation of the Russian Federation, the ozone layer is one of the important natural objects. It is subject to legal protection. The Law “On the Protection of the Environment” (Article 4) regulates protective measures aimed at protecting this natural object from damage, pollution, destruction and depletion.
Article 56 of the Law describes measures to protect the Earth's ozone layer. Among them:

organization of observation of this natural object;
constant monitoring of climate change, which occurs under the influence of the activities of economic entities or due to other processes;
strict observance of standards for the emission of harmful substances into the atmosphere;
regulating the production of chemicals that deplete the ozone layer;
application of penalties and penalties for violation of the above requirements.

There are several international organizations and inspections that carefully monitor how the measures to protect the ozone layer are carried out in different countries of the world.

Wandering hole

If we assume that the ozone hole will continue to expand constantly, and this is quite possible, then humanity is threatened with death. And this is not an exaggeration. Therefore, the preservation of the ozone layer is of great importance today in all countries.

It is worth noting that the ozone hole is unstable. As soon as the amount of harmful emissions into the atmosphere is reduced, the ozone hole begins to gradually tighten. Ozone molecules penetrate into it from those parts of the atmosphere that are located nearby. But there is another risk factor here. In neighboring areas, as a result, the amount of ozone is significantly reduced. The layer becomes thinner.

Risk factors

Meanwhile, scientists continue to conduct research and scare us with disappointing conclusions. They came to this conclusion. If the amount of ozone decreases by only one percent in the upper atmosphere, then, for example, an increase in skin cancer will occur by 3-6%. In addition, ultraviolet rays in large quantities adversely affect the human immune system. He becomes more vulnerable to infectious diseases. Perhaps this explains the fact that more and more people suffer from malignant tumors in the 21st century.

Increased ultraviolet also negatively affects nature. It destroys plant cells, they begin to mutate and produce less oxygen. And although the ozone layer is high and we do not feel it, its importance for nature can hardly be overestimated.

Affects wind, rainfall and temperature

According to scientists, the thinning of the ozone layer directly affects the climate of our planet. Have you noticed that every year the weather becomes more and more changeable?

The ozone layer is not only an "umbrella" for ultraviolet radiation, but also a kind of cover for the Earth. It traps heat that dissipates from the surface of our planet. The thinner the ozone layer, the faster the warm air at the Earth's surface cools. As the researchers note, the air temperature on the planet is gradually, year after year, decreasing. This contributes to a change in the direction of the prevailing winds. The weather becomes extremely changeable.

scary numbers

Here are some more dry statistics that hint at the coming disaster. From 1979 to the present day, there has been a decrease in the annual ozone content by about 4-5 percent. And in the middle latitudes of the planet, this figure is even higher - the ozone layer has become 7 percent smaller.

And if earlier scientists discovered the ozone hole only over Antarctica, today other places have appeared on the map where this protective layer is not observed. Experts have identified several smaller holes over the Arctic and adjacent regions of the Northern Hemisphere.

But there are also optimistic reports. After humanity became concerned about the problem of the preservation of the ozone layer and a number of protective and prohibitive measures were developed, the situation somewhat stabilized. So we can safely say that we, if we behave reasonably, can solve this problem.

Choose one correct answer from several given.

1. Global environmental problems are caused primarily by:

a) geological processes;
b) space factors;
c) high rates of progress;
d) climate change.

2. The main natural factors affecting the size of human populations are:

a) features of the terrain;
b) food resources and diseases;
c) climate features;
d) the geographical position of the country.

3. Rational nature management implies:

a) activities aimed at meeting the needs of mankind;
b) activities aimed at scientifically based use, reproduction and protection of natural resources;
c) extraction and processing of minerals;
d) measures that ensure the industrial and economic activities of a person.

4. Mineral resources of the bowels of the planet include:

a) inexhaustible natural resources;
b) renewable natural resources;
c) non-renewable natural resources;
d) replenishing resources.

5. Deforestation leads to:

a) increasing the species diversity of birds;
b) an increase in the species diversity of mammals;
c) reduction of evaporation;
d) violation of the oxygen regime.

6. The lack of drinking water is caused primarily by:

a) the greenhouse effect;
b) a decrease in the volume of groundwater;
c) pollution of water bodies;
d) soil salinization.

7. The greenhouse effect occurs as a result of the accumulation in the atmosphere of:

a) carbon monoxide;
b) carbon dioxide;
c) nitrogen dioxide;
d) sulfur oxides.

8. The important role of the atmosphere is that it protects living organisms from:

a) sharp fluctuations in temperature;
b) carcinogenic substances;
c) radioactive contamination;
d) pathogens.

9. From hard ultraviolet radiation, living organisms protect:

a) water vapor;
b) clouds;
c) the ozone layer;
d) nitrogen.

10. The destruction of the ozone layer leads to an increase in diseases:

a) gastrointestinal tract;
b) cardiovascular system;
c) skin;
d) respiratory organs.

11. When fluorescent lamps are destroyed, ions hazardous to health are released:

a) mercury;
b) lead;
c) calcium;
d) cobalt.

12. The most common diseases that occur as a result of environmental degradation are:

a) diseases of the musculoskeletal system;
b) infectious diseases;
c) cardiovascular and oncological diseases;
d) diseases of the digestive tract.

13. Substances that cause cancer are called:

a) biogenic;
b) carcinogenic;
c) pyrogenic;
e) abiogenic.

14. The largest number of substances polluting the biosphere falls on:

a) enterprises of the chemical and coal industries;
b) agriculture;
c) everyday activities of a person;
d) vehicles.

Answers: 1 - in; 2 - b; 3 - b; 4 - in; 5 - d; 6 - in; 7 - b; 8 - a; 9 - in; 10 - in; 11 - a; 12 - in; 13 - b; 14 - a.

According to materials:

Prishchepina I.A., Zakharova G.A. etc. Biology. Test tasks. - Minsk: New knowledge, 2005.

Global changes in the atmosphere. Destruction of the ozone layer. Continental problems, causes of extinction of a mass of tropical plant and animal species. Greenhouse effect and possible consequences of climate change. Threat to ecosystems and biodiversity.

Students, graduate students, young scientists who use the knowledge base in their studies and work will be very grateful to you.

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abstract, added 03/14/2007

Global problems

Sources of artificial aerosol air pollution: thermal power plants, factories, factories. Global problems: destruction of the natural environment, pollution of the atmosphere, soil, water. Actual problems of the ozone layer and acid precipitation. Solving environmental problems.

presentation, added 09/25/2011

Ozone layer- part of the stratosphere at an altitude of 12 to 50 km (in tropical latitudes 25-30 km, in temperate latitudes 20-25, in polar 15-20), in which, under the influence of ultraviolet radiation from the Sun, molecular oxygen dissociates into atoms, which then combine with other O2 molecules, forming ozone (O3). The relatively high concentration of ozone (about 8 ml/m³) absorbs dangerous ultraviolet rays and protects everything living on land from harmful radiation.

Stages of destruction of the ozone layer:

1) Emissions: as a result of human activity, as well as as a result of natural processes on Earth, gases containing halogens (bromine and chlorine), ᴛ.ᴇ, are emitted (released). substances that deplete the ozone layer.

3) Movement (accumulated gases containing halogens move into the stratosphere with the help of air currents).

4) Transformation (most of the gases containing halogens, under the influence of ultraviolet radiation from the Sun in the stratosphere, are converted into easily reacting halogen gases, due to which the destruction of the ozone layer in the polar regions of the globe is relatively more active).

5) Chemical reactions (easily reacting halogen gases cause the destruction of stratospheric ozone; the factor contributing to the reactions is polar stratospheric clouds).

Reasons for the destruction of the OS:

Firstly,- ϶ᴛᴏ launches of space rockets. Burning fuel ʼʼburnsʼʼ large holes in the ozone layer. It was once assumed that these ʼʼholesʼʼ are being tightened. It turned out not. Οʜᴎ have been around for quite some time. Secondly, aircraft flying at altitudes of 12-15 km. The steam and other substances emitted by them destroy ozone. But, at the same time, planes flying below 12 km give an increase in ozone. In cities, it is one of the components of photochemical smog. . Thirdly- nitrogen oxides. They are thrown out by the same planes, but most of them are released from the soil surface, especially during the decomposition of nitrogen fertilizers.

Consequences:

This negatively affects not only all living beings: people, animals, plants, tropical forests, but also objects. For example, if the ozone layer becomes too thin, the rubber used on the farm will last much less. Aquatic organisms living in the upper layers of the water will cease to exist. The fauna of the Amazo jungle with pythons and parrots. Fish catches and agricultural yields will decrease significantly. Undoubtedly, the destruction of the ozone layer will affect people as well. Humanity will get sick twice as much, because the immune system will be significantly weakened. Your chances of getting skin cancer and cataracts will increase.

Scientists suggest that a decrease in the ozone layer by 1% will lead to an active spread of diseases. For example, cases of skin cancer will increase by 10,000 times, and eye cataracts by 100,000. A person's propensity for respiratory and lung diseases will skyrocket.

Scientists are searching ways to restore ozone layer.

Can the ozone layer be saved from destruction?

Initially, for this purpose, it was proposed to create factories for the production of ozone, after which it would be delivered by aircraft into the atmosphere. Another option is to build laser-powered, solar-powered balloons that use oxygen to create ozone. The most realistic way out of this situation is to reduce deforestation and increase green spaces.

49) It is customary to call a nuclear weapon the damaging effect of which is due to the energy released during nuclear fission or fusion reactions. It is the most powerful type of weapon of mass destruction.

Nuclear explosions can be carried out on the surface of the earth (water), underground (water) or in the air at various heights. For this reason, the following types of nuclear explosions are distinguished: ground, underground, underwater, air and high-altitude. The most characteristic types of nuclear explosions are ground and air.

Damaging factors of a nuclear explosion : shock wave, light radiation of a nuclear explosion, penetrating radiation, radioactive contamination of the area and electromagnetic pulse.

1) Shock wave (SW)- a region of sharply compressed air propagating in all directions from the center of the explosion at supersonic speed under high pressure

The impact of HC on people should be direct and indirect. With direct exposure, the cause of injury is an instantaneous increase in air pressure, which is perceived as a sharp blow leading to fractures, damage to internal organs, and rupture of blood vessels. With indirect impact, people are amazed by flying debris of buildings and structures, stones, trees, broken glass and other objects.

The degree of damage by a shock wave to various objects depends on the power and type of explosion, the mechanical strength (stability of the object), as well as on the distance at which the explosion occurred, the terrain and the position of objects on the ground.

Read also

— Destruction of the ozone layer

In the 70s. 20th century there was a message about regional decreases in the ozone content in the stratosphere. Particularly noticeable was the seasonally pulsating ozone hole over Antarctica with an area of more than 10 million km2, where the ozone content for the 80s. decreased by almost 50%. Others, “wandering”… [read more].

— OZONE DEPLETION

Currently, there has been a deterioration in the state of the ozone layer and the formation of "ozone holes" (areas with a low ozone content) above the Earth's poles, which poses an environmental hazard. Temporary "holes" also appear over vast areas outside the poles (in ... [read more].

Ministry of Education of the Republic of Belarus

educational institution

"BELARUSIAN STATE UNIVERSITY OF INFORMATICS AND RADIOELECTRONICS"

Institute of Information Technology

Specialty ITiUTS

TEST

(supervised self-guided teacher

student work)

According to the course Fundamentals of Ecology and Energy Saving

Option number 32

Completed by a 3rd year student

Groups No. 182425

Record book number: 182425-20

Name: Grishko Ekaterina Nikolaevna

Address: 231201 Grodno region

Ostrovets, Volodarskogo St. 17/12

Tel.: +375336859213

Minsk, 2013

The main causes of climate change on the Earth, the destruction of the ozone layer, the depletion of natural resources. Possible consequences of these changes.

Scientific and technological progress has posed a number of new, very complex problems for humanity, which it has not encountered before at all, or the problems were not so large-scale. Among them, a special place is occupied by the relationship between man and the environment. In the last century, nature has been under pressure from a 4-fold increase in population and an 18-fold increase in world production.

Scientists say that from about the 60-70s of the XX century. changes in the environment under the influence of man have become global, that is, affecting all countries of the world without exception, therefore they are called global. Among them, the most relevant are:

♦ Earth's climate change;

♦ destruction of the ozone layer;

♦ transboundary transfer of harmful impurities and air pollution;

♦ depletion of fresh water reserves and pollution of the waters of the World Ocean;

♦ depletion of biological diversity;

♦ land pollution, destruction of soil cover, etc.

Global warming. As a result of studying the materials of meteorological observations in all regions of the globe, it has been established that the climate is subject to certain changes. Started at the end of the 19th century. warming especially intensified in the 20-30s of the 20th century, but then a slow cooling began, which stopped in the 60s. The study by geologists of sedimentary deposits of the earth's crust showed that much greater climate changes occurred in past epochs. Since these changes were due to natural processes, they are called natural.

Along with natural factors, human economic activity has an ever-increasing influence on global climatic conditions. This influence began to manifest itself thousands of years ago, when, in connection with the development of agriculture in arid regions, artificial irrigation began to be widely used. The spread of agriculture in the forest zone also led to some climate changes, as it required deforestation over large areas. However, climate change was mainly limited by changes in meteorological conditions in the lower air layer in those areas where significant economic activities were carried out.

In the second half of the XX century. In connection with the rapid development of industry and the growth of energy availability, the prospects for climate change have arisen throughout the planet. Modern scientific research has established that the impact of anthropogenic activity on the global climate is associated with the action of several factors, of which the most important are:

♦ an increase in the amount of atmospheric carbon dioxide, as well as some other gases entering the atmosphere in the course of economic activity, which enhances the greenhouse effect in it;

♦ increase in the mass of atmospheric aerosols;

♦ increase in the amount of thermal energy produced in the process of economic activity and released into the atmosphere.

The first of these causes of anthropogenic climate change is of the greatest importance. The increase in the concentration of carbon dioxide in the atmosphere is determined by the formation of CO2 as a result of the combustion of coal, oil and other fuels. In addition to carbon dioxide, the greenhouse effect of the atmosphere can be affected by an increase in impurities of other gases - methane, nitrogen oxide, ozone, chlorofluorocarbons.

Unlike gases that make up small impurities in the atmospheric air, the influx of carbon dioxide into the atmosphere is so great that it is technically unfeasible to stop this process in the coming decades. In addition, energy consumption in the developing world is starting to rise rapidly.

The gradual increase in the amount of CO2 in the atmosphere is already having a noticeable effect on the Earth's climate, changing it towards warming. The general upward trend in air temperature, which was observed in the 20th century, is intensifying, which has already led to an increase in the average air temperature by 0.5 oC.

As a result of a fourfold increase in the second half of the 20th century. the amount of carbon emissions, the Earth's atmosphere began to heat up at an increasing rate. According to UN forecasts, in the XXI century. the average temperature will rise even more - by 1.2-3.5 "C, which will cause the melting of glaciers and polar ice caps, raise the level of the World Ocean, pose a threat to hundreds of millions of residents of coastal areas and completely flood some islands, and cause the development of other negative processes , first of all - desertification of the lands.

As warming trends intensify, weather patterns become more volatile and climate-related natural disasters become more destructive. The damage caused by natural disasters to the world economy is increasing. In 1998 alone, it exceeded the damage caused by natural disasters throughout the 1980s, tens of thousands of people died and about 25 million "environmental refugees" were forced to leave their homes.

Destruction of the Earth's ozone layer. The main amount of ozone is formed in the upper layer of the atmosphere - the stratosphere, at altitudes from 10 to 45 km. The ozone layer protects all life on Earth from the harsh ultraviolet radiation of the sun. By absorbing this radiation, ozone significantly affects the temperature distribution in the upper atmosphere, which in turn affects the climate.

The total amount of ozone and its distribution in the atmosphere is the result of a complex and not fully understood dynamic balance of photochemical and physical processes that determine its formation, destruction and transport. From about the 70s of the XX century. there is a global decrease in the amount of stratospheric ozone. Over some areas of the Antarctic in September-October, the values of the total ozone content decrease by 60%; in the middle latitudes of both hemispheres, the decrease is 4-5% per decade. The depletion of the planet's ozone layer leads to the destruction of the existing biogenesis of the ocean due to the death of plankton in the equatorial zone, inhibition of plant growth, a sharp increase in eye and cancer diseases, as well as diseases associated with a weakening of the immune system of humans and animals, an increase in the oxidative capacity of the atmosphere, corrosion of metals, etc. .d.

F. Rowland and M. Molino (Berkeley) substantiated the point of view currently accepted by the world community that chlorofluorocarbons (CFCs) - substances that are inert under normal conditions - getting into the stratosphere and being destroyed under the action of the ultraviolet radiation of the Sun, release free chlorine, which is involved in catalytic reactions of ozone destruction. CFCs are widely used as fill gases in aerosols, in the production of soft and hard foams, as freons in refrigeration and air conditioning, as solvents in industrial production, etc. Once in the atmosphere, one molecule of such an inert gas can destroy up to 1000 ozone molecules, and some CFCs can persist in the atmosphere for more than 100 years.

Depletion of fresh water reserves. Between 1900 and 1995, global freshwater consumption increased sixfold, more than twice the rate of population growth. Already, almost one third of the world's population lives in countries where the amount of water consumed is 10% higher than the total amount of available reserves. If current trends continue, by 2025, two out of three people on Earth will live in scarcity.

The main source of humankind's supply of fresh water is, in general, actively renewable surface water, which is about 39,000 km3 per year. Back in the 70s, these huge annual renewable fresh water resources provided an average of about 11 thousand m3 per inhabitant of the globe, in the 80s the per capita supply of water resources decreased to 8.7 thousand m3 / year, and by the end of the XX century. - up to 6.5 thousand m3/year. Taking into account the forecast of the growth of the Earth's population by 2050 (up to 9 billion people), the water supply will fall to 4.3 thousand m3/year. Mankind is alarmed by a rather sharp (almost 2 times) drop in the supply of fresh water at the end of the 20th century.

However, it should be taken into account that the given average data are too generalized. The uneven distribution of the population and water resources around the globe leads to the fact that in some countries the annual provision of the population with fresh water resources decreases to 1000-2000 m3 / year (South African countries) or increases to 100 thousand m3 / year (New Zealand). In such abundant water and sparsely populated areas as Alaska, Guiana, the availability of water resources per capita even exceeds 2 million m3. Fluctuations in river flow over time also have an effect, when in some countries in dry years, fresh water resources decrease by 3-4 times; in some parts of North and East Africa there is no rain for several years, and the rivers dry up.

Groundwater provides the needs of one third of the world's population. Of particular concern to mankind is their irrational use and methods of exploitation. Groundwater extraction in many regions of the world is carried out in such volumes that significantly exceed the ability of nature to renew them. It is widespread in the Arabian Peninsula, in India, China, Mexico, the CIS countries and the USA. There is a drop in the level of groundwater by 1-3 m per year.

In some regions of the world there is intense competition between states for water resources for irrigation and electricity generation, which, in all likelihood, will intensify even more with population growth. Today, the Middle East and North Africa suffer most from water shortages, but by the middle of the 21st century. sub-Saharan Africa will join them as their population doubles or even triples over that time.

Destruction of the soil cover of the Earth. The problem of land resources has now become one of the largest global problems, not only because of the limited land fund of the planet, but also because the natural ability of the soil cover to produce biological products annually decreases both relatively (per capita of a progressively increasing world population) and and absolutely (due to increased losses and soil degradation as a result of human activities).

Mankind has irretrievably lost more fertile land in its history than is being plowed up all over the world (more than 1.5 billion hectares), turning once productive arable land into deserts, wastelands, swamps, bushes, badlands, ravines. Many lifeless deserts of the world are the result of human activity. The process of these irretrievable losses continues to this day. According to the most optimistic estimates of UN specialists, almost 2 billion hectares of land are subject to human-induced degradation, which threatens the existence of almost 1 billion.

1.1. Destruction of the ozone layer

Human. The main reasons for this are soil salinization as a result of irrigation, as well as erosion caused by overgrazing, deforestation, and land desertification.

Soil erosion has been known to man for a long time, but it has received particular development in the modern era in connection with the intensification of agriculture, with a multiple increase in the load on the soil cover.

The second most important degradation process, also widespread throughout the world, is a complex set of various adverse secondary effects of irrigated agriculture, among which secondary salinization and waterlogging of soils stand out. An increase in the arable layer of irrigated soil in the content of salts up to 1% reduces the yield by one third, and with a content of 2-3%, the crop dies completely.

The depletion of arable and pasture soils, the decline in their fertility occurs all over the world as a result of their irrational intensive use. There are other degradation processes: waterlogging of soils in areas of sufficient or excessive atmospheric moisture, soil compaction, and technogenic pollution. Globally, each year, an additional 20 million hectares of agricultural land become unsuitable for crop production due to soil degradation or urban encroachment. At the same time, food demand in developing countries is expected to double over the next 30 years. New lands can and will be developed, but this will mainly take place in the zone of risky farming, where soils are even more susceptible to degradation.

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Why is the ozone layer needed?

In 1912, French physicists Charles Fabry and Henri Buisson discovered the existence of the ozone layer. Scientists have proven that ozone molecules are concentrated in the distant layers of the atmosphere, which block short waves of the solar spectrum and practically do not transmit ultraviolet radiation to Earth.

Further study of ozone compounds in the atmosphere showed that the ozone layer also retains the heat of the sun, which allows us to maintain a habitable temperature on our planet. Moreover, ozone compounds are capable of converting some harmful chemicals (eg methane, nitrogen oxides) into environmentally friendly compounds.

The protective function of the ozone layer
comparable in strength to a metal shield

Although the amount of ozone compounds in the atmosphere is relatively small, the protective function of the so-called "ozone layer" is comparable in strength to a metal shield. If the ozone layer did not exist, the Earth would be subjected to constant solar radiation and other destructive influences from space. There is reason to believe that without the existence of the ozone layer, life would not have arisen on Earth in the form in which we observe it now.

How does the ozone layer work?

Ozone compounds in the atmosphere are mostly concentrated in the stratosphere - at a distance of 10 to 50 km from the Earth. In total, there are about three thousand tons of ozone molecules in the atmosphere. On the scale of the volume of all atmospheric air, this is quite a bit. If you collect all the ozone molecules together and evenly distribute them around the Earth, the thickness of such a layer will be only 3-5 millimeters. And if we imagine that all the ozone molecules can be concentrated in one place, then we get a gaseous ball with a diameter of only 14 km. For comparison: such a ball containing all atmospheric air would have a diameter of 2001 km.

You can get to know the ozone layer “closer” by watching a visual video “Priceless gas. How much ozone is in the atmosphere? (in Belarusian).

Even a relatively small amount of ozone in the atmosphere works wonders. In addition to protecting our planet from dangerous solar radiation, the ozone layer makes the Earth a unique planet, creating the so-called temperature inversion. The normal course of temperature is considered to be a decrease in the temperature of the atmosphere with distance from the Earth: the higher - the colder. However, the ozone layer creates a barrier that disrupts the normal course of temperature. Where the ozone layer is located, the temperature suddenly starts to rise again.

Atmospheric Ozone Layer and Temperature Inversion

The temperature inversion created by the ozone layer divides the atmosphere into two parts - the troposphere and everything above. Due to this separation, weather conditions suitable for life can form in the troposphere. Other planets are less fortunate (well, or more) - there is no ozone layer, and, consequently, no temperature inversion, which would create suitable conditions for human life.

Why is ozone destroyed?

By the 1970s, scientists around the world began to notice a decrease in the concentration of ozone molecules in the atmosphere. This fact occupied the minds of many physicists and chemists around the world, scientists put forward a variety of hypotheses about the causes of such changes. The study by chemists Frank Sherwood Rowland and Mario Molina of the effects of chlorofluorocarbons (CFCs) on the Earth's atmosphere was decisive. In 1973, chemists theorized that chlorine molecules, which appear as a result of the decay of CFCs under ultraviolet rays, could cause the destruction of large amounts of ozone in the atmosphere.

One chlorine molecule can destroy up to 200,000 ozone molecules

The conclusions of American scientists were supported by similar works by scientists Paul Joseph Crutzen and Harold Johnstone. Since then, such a hypothesis about such a phenomenon as ozone depletion, is generally accepted in the scientific world.

This is how the destruction of the ozone molecule under the influence of chlorofluorocarbon looks like. Under the influence of ultraviolet light, atomic chlorine is released, which destroys bonds within the ozone molecule.

Molina and Rowland's discovery made it possible not only to explain the process of ozone layer thinning, but also to draw an important conclusion that ozone depletion occurs under the influence of human activity. After all, the main "suppliers" of chlorofluorocarbons into the atmosphere are froenes - those substances that are used to create artificial cold in our refrigerators, air conditioners and other household and industrial appliances. Substances hazardous to ozone are also found in some aerosols, fire extinguishers, insulation boards, and solvents.

Molina, Rowland, and Crutzen were subsequently awarded the Nobel Prize in Chemistry in 1995 for their work on ozone depletion.

In order to protect the ozone layer from destruction, environmentalists are advised to follow a few simple tips in everyday life.

Do not disassemble or repair old refrigerators yourself - ozone-depleting freons can get into the environment.
Recycle old refrigerators and air conditioners.
Choose appliances (especially refrigerators and air conditioners) that do not contain ozone-depleting substances. This should be indicated on the packaging.
Choose aerosols that are safe for the ozone layer. They are usually labeled “ozone-friendly”, “ozone friendly”, “ozone free”.

Examples of “ozone-friendly” labels

Do ozone holes exist?

As Ilya Bruchkovsky, a researcher at the National Center for Ozone Monitoring at the Belarusian State University, a researcher of stratospheric ozone in Antarctica, explains, the concept of “ozone hole” does not exist in the scientific world, but there is an “ozone anomaly”.

Essentially, ozone anomalies are areas of very low ozone in the atmosphere. So, if the normal content of ozone in the atmosphere is 300 Dobson units, then about 180 units are observed inside the ozone anomaly. Indeed, one such anomaly exists and is located above Antarctica.

Dynamics of the ozone content in the atmosphere in the region of the ozone anomaly over the Antarctic from 1957 to 2001.

the new era of active space exploration, namelyspace rocket launches . The substances that make up the outflowing jet stream (due to which the rocket moves), intensively destroy ozone. Thus, at the launch site of the launch vehicle, a large “hole” appears in the ozone layer, which, as it turned out, takes a very long time to close. And every year there are more and more such “holes drilled in the atmosphere”. Which inevitably leads to the depletion of the Earth's ozone layer.

The second reason for the destruction of the Earth's ozone layer is

intensive development of high-altitude aviation(aircraft flying at an altitude of over 12 km). The combustion products of these machines also destroy ozone molecules, leading to the depletion of the Earth's ozone layer. The ozone-active components of exhaust gases are nitrogen oxides and, to a lesser extent, carbon monoxide. Scientists have analyzed ways to reduce nitric oxide in jet fuel combustion products. However, the research results to date are disappointing. Reducing stratospheric ozone-destroying nitrous oxide is not possible either by upgrading existing engines or by switching to "clean" fuels (liquefied natural gas and liquefied or compressed hydrogen). Reducing the emission of substances that destroy the Earth's ozone layer will be possible only with the creation of fundamentally new engines. But this is still a long way off...

The third reason for the destruction of the Earth's ozone layer is

application of nitrogen fertilizers in agriculture. As they decompose, they release nitrogen oxides, which rise into the stratosphere and ... destroy ozone molecules, causing the depletion of the Earth's ozone layer, of course.

The fourth reason for the destruction of the Earth's ozone layer is

widespread use of freons in human economic activity(as sprayers, in the refrigeration industry). At the surface of the earth, these gases are practically harmless, since they do not enter into any chemical reactions. But, once in the stratosphere, freons under the influence of solar radiation enter into photochemical reactions, releasing atomic chlorine. And one chlorine atom, as mentioned above, during its long life is capable of destroying up to one hundred thousand ozone molecules. Here is one warrior in the field. And the amount of freons in the atmosphere is growing year by year, increasing by about 8-9% annually.

We examined the causes of the destruction of the ozone layer of the Earth. Let's sadly summarize: human activity is destroying the planet. It's time to move on to the next paragraph of this article. What threatens us with the depletion of the Earth's ozone layer?

Consequences of the destruction and depletion of the ozone layer of the Earth.

The destruction of the ozone layer increases the flow of solar radiation to the Earth.

According to doctors, every percentage of ozone lost on a planetary scale causes:

up to 150 thousand additional cases of blindness due to cataracts,

a 2.6 percent increase in the number of skin cancers,

the number of diseases caused by the weakening of the human immune system is increasing significantly.

But it's not just people who suffer. Ultraviolet radiation is also extremely harmful to plankton, fry, shrimp, crabs, algae that live on the surface of the ocean, and other organisms in the biosphere.

The problem of ozone depletion was discovered long ago, but by the 1980s, scientists sounded the alarm. If ozone is significantly reduced in the atmosphere, the earth will lose its normal temperature regime and stop cooling. As a result, a huge number of documents and agreements were signed in various countries in order to reduce the production of freons. In addition, a replacement for freon was invented - propane-butane. According to its technical parameters, this substance has high performance, it can be used where freons are used.

Today, the problem of ozone depletion is very relevant. Despite this, the use of technologies using freons continues. At the moment, people are thinking about how to reduce the amount of freon emissions, are looking for substitutes to save and restore the ozone layer.

20. Acid rain: causes, mechanisms of occurrence, impact on flora and fauna, structures.

Acid rain is called any atmospheric precipitation (rain, snow, hail) containing any amount of acids. The presence of acids leads to a decrease in the pH level. Hydrogen index (pH) - 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 medium is.

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. The compounds that lower the pH level of sediments are sulfur oxides, nitrogen oxides, hydrogen chloride and volatile organic compounds (VOCs).

Causes of acid rain

acid rain by the nature of their origin, there are two types: natural (arise as a result of the activity of nature itself) and anthropogenic (caused by human activity).

natural acid rain

There are few natural causes of acid rain:

activity of microorganisms, volcanic activity, lightning discharges, burning of wood and other biomass.

Anthropogenic acid rain

The main cause of acid rain is air pollution. If about thirty years ago, industrial enterprises and thermal power plants were named as global causes that cause the appearance of compounds in the atmosphere that “oxidize” rain, today this list has been supplemented by road transport.

Thermal power plants and metallurgical enterprises "give" nature about 255 million tons of sulfur and nitrogen oxides.

Solid-propellant rockets have also made and are making a significant contribution: the launch of one Shuttle complex results in the release of more than 200 tons of hydrogen chloride and about 90 tons of nitrogen oxides into the atmosphere.

Anthropogenic sources of sulfur oxides are enterprises that produce sulfuric acid and refine oil.

Exhaust gases of road transport - 40% of nitrogen oxides entering the atmosphere.

The main source of VOCs in the atmosphere, of course, are chemical industries, 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 delivers more than 60% of sulfur compounds, about 40-50% of nitrogen compounds and 100% of volatile organic compounds into the atmosphere.

Oxides, getting into the atmosphere, react with water molecules, forming acids. Sulfur oxides, getting into the air, form sulfuric acid, nitrogen oxides form nitric acid. One should also take into account the fact that the atmosphere above large cities always contains 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 ground. Along with water, acid also enters.

The effects of acid rain

Oxidation of water resources. The most sensitive are rivers and lakes. Fish are dying. While some fish species can tolerate slight water acidification, they also die due to the loss of food resources. In those lakes where the pH level is less than 5.1, not a single fish was caught. This is explained not only by the fact that adult specimens of fish die - at a pH of 5.0, the majority cannot hatch fry from eggs, as a result, there is a decrease in the number and species composition of fish populations.

Harmful effect on vegetation. Acid rain affects vegetation directly and indirectly. The direct impact occurs in the highlands, where tree crowns are literally immersed in acidic clouds. Excessively acidic 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. Facades of buildings, monuments of culture and architecture, pipelines, cars - everything is exposed to acid rain. Many studies have been done, and they all point to one thing: over the past three decades, the process of exposure to acid rain has increased significantly. As a result, not only marble sculptures, stained glass windows of ancient buildings, but also leather and paper products of historical value are under threat.

Human health. By themselves, acid rain does not have a direct impact on human health - falling under such rain or swimming in a reservoir with acidified water, a person does not risk anything. Health hazards are compounds that are formed in the atmosphere due to the ingress of sulfur and nitrogen oxides into it. The resulting sulfates are carried by 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.

21. Smogi: types, formation mechanism

Smog is a mixture of smoke, fog and some pollutants.

One of the global environmental problems that require a radical solution is the destruction of the ozone layer. The term is adopted to refer to the peak of ozone concentration in the stratosphere, which serves as an effective screen that destroys ultraviolet radiation. Ozone is a type of oxygen that is formed when oxygen gas is exposed to ultraviolet light in the upper atmosphere. The ozone layer, located at an altitude of about 24 km, protects the earth's surface from the harmful ultraviolet rays of the sun.

Concerns about the health of the ozone layer were first raised in 1974 when it was found that CFCs could destroy the ozone layer that protects the Earth from ultraviolet radiation. Fluorinated and chlorinated hydrocarbons (FCH) and halogen compounds (halons) emitted into the atmosphere destroy the fragile structure of this layer. The ozone layer is depleted, which leads to the appearance of the so-called "ozone holes". The penetrating ultraviolet rays of the sun are dangerous to all life on Earth. They have a particularly negative effect on human health, its immune and gene systems, causing skin cancer and cataracts. The destruction of the ozone layer leads to an increase in ultraviolet radiation, which in turn will lead to an increase in infectious diseases.

Ultraviolet rays can destroy plankton, tiny organisms that form the basis of the food chain in the ocean. They are also dangerous to the flora on land, including crops. It is estimated that a 25% decrease in ozone results in a loss of 10% of the main substances in the lit, warm and biologically rich upper layer of the ocean and a loss of 35% near the water surface. As plankton form the basis of the marine food chain, changes in its abundance and species composition will affect fish and shellfish harvests. Losses of this kind will have a direct impact on the food supply. That is, changing levels of ultraviolet radiation as a result of the depletion of the Earth's ozone layer can have a significant impact on food production. According to the studies of the Royal Swedish Academy of Sciences, as a result of the influence of this factor, soybean yields decreased by 20-25% with a decrease in ozone by 25%. The protein and oil content of the beans is also reduced. Forests have also proved vulnerable, especially coniferous trees.

Stages of destruction of the ozone layer:

1)Issues: as a result of human activity, as well as as a result of natural processes on Earth, gases containing halogens (bromine and chlorine) are emitted (released), i.e. substances that deplete the ozone layer.

2)Storage(Emitted gases containing halogens accumulate (accumulate) in the lower atmospheric layers, and under the influence of wind and air currents move to regions that are not in direct proximity to the sources of such gas emissions).

3)moving(accumulated gases containing halogens move into the stratosphere with the help of air currents).

4)transformation(Most of the gases containing halogens, under the influence of ultraviolet radiation from the Sun in the stratosphere, are converted into easily reacting halogen gases, as a result of which the destruction of the ozone layer is relatively more active in the polar regions of the globe).

5)chemical reactions(easily reacting halogen gases cause stratospheric ozone depletion; factor contributing to the reactions is polar stratospheric clouds).

6)Removal(under the influence of air currents, easily reacting halogen gases return to the troposphere, where, due to the moisture and rain present in the clouds, they are separated, and thus completely removed from the atmosphere).

7.Water pollution

Water pollution manifests itself in a change in physical and organoleptic properties (violation of transparency, color, odors, taste), an increase in the content of sulfates, chlorides, nitrates, toxic heavy metals, a reduction in air oxygen dissolved in water, the appearance of radioactive elements, pathogenic bacteria and other pollutants.

Main water pollutants. It has been established that more than 400 types of substances can cause water pollution. If the permissible norm is exceeded by at least one of the three indicators of harmfulness: sanitary-toxicological, general sanitary or organoleptic, the water is considered contaminated.

Distinguish chemical, biological and physical pollutants (P. Bertoks, 1980). Among chemical The most common pollutants include oil and oil products, surfactants (synthetic surfactants), pesticides, heavy metals, dioxins, etc. (Table 14.1). Very hazardous water pollution biological contaminants such as viruses and other pathogens, and physical- radioactive substances, heat, etc.

The main types of water pollution. The most common are chemical and bacterial contamination. Radioactive, mechanical and thermal pollution is observed much less frequently.

chemical pollution- the most common, persistent and far-reaching. It can be organic (phenols, naphthenic acids, pesticides, etc.) and inorganic (salts, acids, alkalis), toxic (arsenic, mercury compounds, lead, cadmium, etc.) and non-toxic. When deposited on the bottom of reservoirs or during filtration in the reservoir, harmful chemicals are sorbed by rock particles, oxidized and reduced, precipitated, etc., however, as a rule, complete self-purification of polluted waters does not occur. The source of chemical contamination of groundwater in highly permeable soils can extend up to 10 km or more.

bacterial pollution is expressed in the appearance of pathogenic bacteria, viruses (up to 700 species), protozoa, fungi, etc. in the water. This type of pollution is temporary.

The content in water, even at very low concentrations, of radioactive substances that cause radioactive pollution

Mechanical pollution characterized by the ingress of various mechanical impurities into the water (sand, sludge, silt, etc.). Mechanical impurities can significantly worsen the organoleptic properties of water.

GROUNDWATER POLLUTION

human-induced deterioration in the quality of groundwater (by physical, chemical or biological indicators) compared to its natural state, which leads or may lead to the impossibility of their use for the intended purposes

The problem of groundwater pollution is exacerbated by the fact that under conditions of an anaerobic reducing environment characteristic of underground horizons, constantly low temperatures, and lack of sunlight, self-purification processes are sharply slowed down.

main types of groundwater pollution sources .Industrial sites of enterprises associated with the production or use as raw materials of substances capable of migrating with groundwater. Places of storage and transportation of industrial products and production waste.

Especially dangerous for groundwater pollution are pesticide storage, including those prohibited for use, as well as inactive wells on livestock farms.

Features of groundwater pollution are due to the fact that at low temperatures, lack of sunlight, lack or absence of oxygen, self-purification processes proceed extremely slowly, and secondary processes often develop that enhance the effect of pollution.

8.ANTHROPOGENIC EUTROPHY.

Although eutrophication of water bodies is a natural process and its development is estimated within the framework of geological time scales, however, over the past few centuries, man has significantly increased the use of nutrients, especially in agriculture as fertilizers and detergents. In many water bodies over the past few decades, an increase in trophy has been observed, accompanied by a sharp increase in the abundance of phytoplankton, overgrowth of coastal shallow waters by aquatic vegetation, and changes in water quality. This process became known as anthropogenic eutrophication.

Shilkrot G.S. (1977) defines anthropogenic eutrophication as an increase in the primary production of a reservoir and the associated change in a number of its regime characteristics as a result of an increasing addition of mineral nutrients to the reservoir. At the International Symposium on Eutrophication of Surface Waters (1976), the following wording was adopted - "anthropogenic eutrophication is an increase in the supply of plant nutrients to water due to human activities in the basins of water bodies and the resulting increase in the productivity of algae and higher aquatic plants."

Anthropogenic eutrophication of water bodies began to be considered as an independent process, fundamentally different from the natural eutrophication of water bodies.

Natural eutrophication is a very slow process in time (thousands, tens of thousands of years), it develops mainly due to the accumulation of bottom sediments and the shallowing of water bodies.

Anthropogenic eutrophication is a very fast process (years, decades), its negative consequences for water bodies often manifest themselves in a very sharp and ugly form.

CONSEQUENCES OF EUTROPHY

Among the most obvious manifestations of the consequences of eutrophication is the "bloom" of water. In fresh waters, it is due to the massive development of blue-green algae, in marine - dinoflagellates. The duration of flowering water ranges from several days to 2 months. The periodic change in the abundance maxima of individual mass species of planktonic algae in water bodies is a natural phenomenon due to seasonal fluctuations in temperature, illumination, nutrient content, as well as genetically determined intracellular processes. Among the algae that form numerous populations up to the scale of "blooming" of water, the blue-green ones from the genera Microcystis, Aphanizomenon, Anabaena, Oscillatoria play the greatest role in terms of reproduction rates, biomass, and ecological consequences. The scientific study of this phenomenon began in the 19th century, and a rational explanation and analysis of the mechanisms of mass reproduction of blue-greens were given only in the middle. 20th century in the USA by the limnological school of J. Hutchinson. Similar studies were carried out at the IBVV RAS (Borok) by Guseva K.A. and in the 60-70s by the staff of the Institute of Hydrobiology (Ukraine), in the late 70s - by the Institute of the Great Lakes (USA).

Algae that cause "blooming" of water are among the species capable of limiting saturation of their biotopes. In the reservoirs of the Dnieper, Volga and Don, Microcystis aeruginosa, M. wesenbergii, M. holsatica, Oscillatoria agardhii, Aphanizomenoen flos-aquae, species of the genus Anabaena dominate.

It has been established that the initial biofund of Microcystis is located in the surface layer of silt deposits in winter. Microcystis hibernates in the form of slimy colonies, inside which accumulations of dead cells cover the only living one. As the temperature rises, the central cell begins to divide, and in the first stage, the food source is dead cells. After the collapse of the colonies, the cells begin to utilize the organic and biogenic substances of the sludge.

Aphanizomenon and Anabaena hibernate as spores, awakening to active life when the temperature rises to +6 C ⁰. Another source of the biofund of blue-green algae is their accumulations thrown ashore and hibernating in a layer of dry crusts. In the spring, they soak and a new vegetation cycle begins.

Initially, algae feed osmotically and the biomass accumulates slowly, then they float up and begin to actively photosynthesize. In a short time, algae can capture the entire water column and form a continuous carpet. Anabaena usually dominates in May, Aphanizomenon in June, and Microcystis and Aphanizomenon from the end of June-July-August. The mechanism of the explosive nature of algal reproduction was revealed by the work of the Great Lakes Institute (USA). Given the enormous breeding potential of blue-green algae (up to 10 ²⁰ descendants of one cell per season), one can clearly imagine the scale that this process takes. Therefore, the factor of primary eutrophication of reservoirs is their provision with phosphorus due to the flooding of fertile floodplain lands and the decomposition of vegetation. The factor of secondary eutrophication is the process of siltation, since silts are an ideal substrate for algae.

After intensive multiplication under the action of constricting electrostatic forces, the formation of colonies begins, the contraction of colonies into aggregates and their merging into films. "Fields" and "blooming spots" are formed, migrating across the water area under the influence of currents and driven to the shores, where decaying accumulations with a huge biomass are formed - up to hundreds of kg / m ³.

Decomposition is accompanied by a number of dangerous phenomena: oxygen deficiency, release of toxins, bacterial contamination, formation of aromatic substances. During this period, there may be interference in the water supply due to clogging of filters at waterworks, recreation becomes impossible, and fish kills occur. Water saturated with algal metabolic products is allergenic, toxic and unsuitable for drinking purposes.

It can cause over 60 diseases, especially of the gastrointestinal tract, and is suspected, though not proven, to be oncogenic. Exposure to blue-green metabolites and toxins causes "Gaff disease" in fish and warm-blooded animals, the mechanism of action of which is reduced to the appearance of B ₁ beriberi.

With the mass die-off of blue-greens, there is a rapid disintegration and lysis of colonies, especially at night. It is assumed that the cause of mass extinction can be mass poisoning with their own toxins, and the impetus is symbiotic viruses that are not capable of destroying cells, but capable of weakening their vital activity.

Surge-on collapsing masses of blue-green algae acquire an unpleasant yellow-brown color and spread throughout the water area in the form of foul-smelling clusters, gradually deteriorating by autumn. This whole complex of phenomena was called "biological self-pollution". A small number of slimy colonies settle to the bottom and overwinter. This reserve is quite sufficient for the reproduction of new generations.

Blue-green algae are the oldest group of organisms found even in Archean deposits. Modern conditions and anthropogenic load only revealed their potential and gave them a new impetus for development.

Blue-greens alkalize water and create favorable conditions for the development of pathogenic microflora and pathogens of intestinal diseases, including Vibrio cholerae. Dying off and turning into a state of phytodetritus, algae affect the oxygen of the deep layers of water. Blue-greens during the flowering period strongly absorb the short-wavelength part of visible light, heat up and are a source of ultrashort radiation, which can affect the thermal regime of the reservoir. The value of surface tension decreases, which can cause the death of hydrobionts living in the surface film. The formation of a surface film that screens the penetration of solar radiation into the water column causes light starvation in other algae and slows down their development.

For example, the total biomass of blue - green algae, producing during the growing season in the reservoirs of the Dnieper, reaches values of the order of 10 ⁶ t (in dry weight). This corresponds to the mass of the locust cloud, which V.I. Vernadsky called "rock in motion" and compared with the mass of copper, lead and zinc mined during the 19th century around the world.

Effects of eutrophication on phytoplankton

Anthropogenic eutrophication leads to a change in the nature of the seasonal dynamics of phytoplankton. As the trophy of water bodies increases, the number of peaks in the seasonal dynamics of its biomass increases. In the structure of communities, the role of diatoms and golden algae decreases, while the role of blue-green and dinophytes increases. Dinoflagellates are characteristic of stratified deep-sea lakes. The role of chlorococcal green and euglenoid algae is also increasing.

Effects of eutrophication on zooplankton. The predominance of species with a short life cycle (cladocerans and rotifers), the predominance of small forms. High production, small share of predators. The seasonal structure of communities is simplified - a unimodal curve with a maximum in summer. Fewer dominant species.

Effects of eutrophication on phytobenthos. Increased development of filamentous algae. The disappearance of charophytes, which cannot tolerate high concentrations of nutrients, especially phosphorus. A characteristic feature is the expansion of the areas of overgrowth of common reed, broad-leaved cattail and manna, comb pondweed.

Effects of eutrophication on zoobenthos.

Violation of the oxygen regime in the bottom layers leads to a change in the composition of zoobenthos. The most important sign of eutrophication is the decrease in the larvae of hexania mayflies in the lake. Erie is an important food item for salmon in the lake. The larvae of some dipterous insects, which are less sensitive to oxygen deficiency, are becoming increasingly important. The density of populations of oligochaete worms is increasing. Benthos becomes poorer and more monotonous. The composition is dominated by organisms adapted to a low oxygen content. At the late stages of eutrophication, only a few organisms remain in the deep region of water bodies that are adapted to the conditions of anaerobic metabolism.

The consequences of eutrophication for the ichthyofauna.

Eutrophication of water bodies affects the fish population in 2 main forms:

direct effect on fish

direct influence is relatively rare. It manifests itself as a single or mass death of eggs and juvenile fish in the coastal zone and occurs when effluents containing lethal concentrations of mineral and organic compounds enter. Such a phenomenon is usually local in nature and does not cover the reservoir as a whole.

indirect influence manifested through various changes in aquatic ecosystems

indirect influence is the most common. During eutrophication, a zone with a low oxygen content and even a dead zone can occur. In this case, the habitat of fish is reduced, and the food supply available to them is reduced. Water bloom creates an unfavorable hydrochemical regime. The change of plant associations in the coastal area, often accompanied by an increase in swamping processes, leads to a reduction in the area of spawning grounds and feeding grounds for larvae and juvenile fish.

Changes in the ichthyofauna of water bodies under the influence of eutrophication manifest themselves in the following forms:

Decrease in the number, then disappearance of the most demanding fish species (stenobionts) in terms of water quality.

Changes in the fish productivity of a reservoir or its individual zones.

The transition of a reservoir from one fishery type to another according to the scheme:

salmon-whitefish → bream-perch → bream-roach → roach-perch-crucian.

This scheme is similar to the transformation of lake ichthyocenoses in the course of the historical development of aquatic ecosystems. However, under the influence of anthropogenic eutrophication, it takes place over several decades. As a result, whitefish (and in rare cases salmon) disappear first. Instead, cyprinids (bream, roach, etc.) and, to a lesser extent, perch (pike perch, perch) become the leaders. Moreover, from carp bream is gradually being replaced by roach, from perch, perch dominates. In extreme cases, water bodies pass into a state of extinction and are inhabited mainly by crucian carp.

On fish, general patterns in changes in the structure of communities are confirmed - long-cycle species are replaced by short-cycle ones. There is an increase in fish productivity. However, at the same time, valuable whitefish species are replaced by species with low commercial qualities. First, large particles - bream, pike perch, then small particles - roach, perch.

Often the consequences for the fish population are irreversible. When the trophy level returns to its original state, extinct species do not always appear. Their restoration is possible only if there are available ways of settling from neighboring water bodies. For valuable species (whitefish, vendace, pike perch), the probability of such settlement is low.

CONSEQUENCES OF WATER BODIES EUTROPHICATION FOR HUMANS

Man is the main consumer of water. As you know, with an excessive concentration of algae, water quality deteriorates.

Particular attention deserves toxic metabolites, in particular blue-green algae. Algotoxins exhibit significant biological activity in relation to various hydrobionts and warm-blooded animals. Algotoxins are highly toxic compounds. Blue - green toxin acts on the central nervous system of animals, which is manifested in the occurrence of paralysis of the hind limbs, desynchronization of the rhythm of the central nervous system. In chronic poisoning, the toxin inhibits redox enzymatic systems, cholinesterase, increases the activity of aldolase, as a result of which carbon and protein metabolism is disturbed, and incompletely oxidized products of carbohydrate metabolism accumulate in the internal environment of the body. A decrease in the number of red blood cells, inhibition of tissue respiration causes mixed type hypoxia. As a result of deep intervention in the metabolic processes and tissue respiration of warm-blooded animals, the blue-green toxin has a wide range of biological effects and can be classified as a protoplasmic poison of high biological activity. All this testifies to the inadmissibility of using water for drinking purposes from places of accumulation of algae and reservoirs subject to strong blooms, since the toxic substance of algae is not neutralized by conventional water treatment systems and can enter the water supply network both in dissolved form and together with individual cells of algae, not delayed filters.

Pollution and deterioration of water quality can affect human health through a number of trophic links. Thus, mercury contamination of water was the cause of its accumulation in fish. Eating such fish caused a very dangerous disease in Japan - Minimat disease, as a result of which numerous deaths were noted, as well as the birth of blind, deaf and paralyzed children.

A relationship has been established between the occurrence of childhood methemoglobinemia and the content of nitrates in water, resulting in a more than 2-fold increase in the mortality of little girls born in those months when the level of nitrates was high. High nitrate levels have been noted in the US Corn Belt in wells. Often groundwater is not suitable for drinking. The occurrence of meningoencephalitis in adolescents is associated after a long bath in a pond or in a river on a warm summer day. A connection between the disease aseptic meningitis, encephalitis and swimming in water bodies is assumed, which is associated with increased viral pollution of water.

Infectious diseases have become widely known due to microscopic fungi that enter wounds from water, causing severe skin damage in humans.

Contact with algae, drinking water from blooming waters, or eating fish that feed on toxic algae causes Haff disease, conjunctivitis, and allergies.

Often in recent years, outbreaks of cholera are timed to coincide with the period of "flowering".

The massive development of algae in the reservoir, along with interference with water supply and deterioration of water quality, significantly complicates the recreational use of the water source, and also causes interference in technical water supply. The development of biofouling intensifies on the walls of pipes of water conduits and cooling systems. When the medium is alkalized due to the development of algae, solid carbonate deposits are formed, and due to the settling of particles and algae, the thermal conductivity of the tubes of heat exchange devices decreases.

Thus, the excessive accumulation of algae during the period of intense "bloom" of water is the cause of biological pollution of water bodies and a significant deterioration in the quality of natural waters.