The cycle of chemical elements on earth. Chemical elements in nature – cycle and migration. Living indicators of environmental pollution

Biogeochemical cycles of the main chemical elements

Introduction

The emergence of living matter on Earth made possible the continuous circulation of chemical elements in the biosphere, their transition from the external environment to organisms and back. This circulation of chemical elements is called biogeochemical cycles. Biogeochemical cycle is part of the biotic cycle, including exchange cycles of chemical elements of abiotic origin, without which living matter cannot exist (carbon, oxygen, hydrogen, nitrogen, phosphorus, sulfur and many others). Typically, there are three main types of biogeochemical cycles: the water cycle, cycles of gaseous substances with a reserve fund in the atmosphere or hydrosphere (ocean), sedimentary cycles of chemical elements with a reserve fund in the earth's crust.

The water cycle

Water is the basic element necessary for life. Quantitatively, it is the most common inorganic component of living matter.

The oceans contain 97% of the total mass of water in the biosphere. It is assumed that evapotranspiration is balanced by precipitation. More water evaporates from the ocean than enters it with precipitation; on land it is the other way around. “Extra” precipitation that falls on land falls into ice caps and glaciers, replenishes groundwater (from where plants draw water for transpiration), and finally ends up in lakes and rivers, gradually returning with runoff to the ocean. Most of the water cycle occurs between the atmosphere and the ocean.

The presence in the atmosphere of a significant reserve fund favors the fact that the cycles of some gaseous substances are capable of fairly rapid self-regulation in the event of various local imbalances. Thus, excess carbon dioxide accumulated somewhere as a result of increased oxidation or combustion is quickly dissipated by the wind; in addition, the intensive formation of carbon dioxide is compensated by its greater consumption by plants or its conversion into carbonates. Ultimately, as a result of self-regulation of the negative type feedback The cycles of gaseous substances on a global scale are relatively perfect. The main such cycles are the cycles of carbon (in the composition of carbon dioxide), nitrogen, oxygen, phosphorus, sulfur and other biogenic elements.

Carbon cycle

On land, it begins with the fixation of carbon dioxide by plants during photosynthesis, producing organic matter and the by-product release of oxygen. Part of the fixed carbon is released during plant respiration as CO2

Soil fungi, depending on the growth rate, emit from 200 to 2000 cm3 of CO2 per 1 g of dry mass. A lot of carbon dioxide is produced by bacteria, which, based on living weight, breathe 200 times more intensely than a person. Carbon dioxide is also released by plant roots and numerous living organisms. Microorganisms decompose dead plants and dead animals, resulting in the carbon of dead organic matter being oxidized to carbon dioxide and released back into the atmosphere.

Between the land and the World Ocean there are constant processes of carbon migration, in which it is predominantly carried out in the form of carbonate and organic compounds from land to the ocean. Carbon comes from the World Ocean to land in small quantities in the form of CO2 released into the atmosphere. Carbon dioxide in the atmosphere and hydrosphere is exchanged and renewed by living organisms over 395 years.

Nitrogen cycle

Just like the carbon cycle and other cycles, it covers all areas of the biosphere. Microorganisms play a key role in the cycle of nitrogen compounds: nitrogen fixers, nitrifiers and denitrifiers. Other organisms influence the nitrogen cycle only after it enters their cells. As is known, legumes and representatives of some genera of other vascular plants (for example, alder, araucaria, oleaster) fix nitrogen with the help of symbiont bacteria. The same is observed in some lichens that fix nitrogen with the help of symbiotic blue-green algae. It is obvious that the biological fixation of molecular nitrogen by free-living and symbiotic organisms occurs in both the autotrophic and heterotrophic parts of ecosystems.

Of the huge reserves of nitrogen in the atmosphere and sedimentary shell of the lithosphere, only fixed nitrogen, assimilated by living organisms of land and ocean, participates in its cycle. The category of the exchange fund of this element includes: nitrogen from annual biomass production, nitrogen from biological fixation by bacteria and other organisms, juvenile (volcanogenic) nitrogen, atmospheric (fixed during thunderstorms) and technogenic

It is easy to notice that, with the exception of tundra vegetation, where the content of nitrogen and ash elements is approximately the same, in almost all other types of vegetation the mass of nitrogen is 2 ... 3 times less than the mass of ash elements. The number of elements circulating during the year (i.e., the capacity of the biological cycle) is greatest in tropical forests, then in black soil steppes and deciduous forests of the temperate zone (oak forests).

Oxygen cycle

The active geochemical activity of living matter and its primary role in this process are clearly expressed in the oxygen cycle. The biogeochemical oxygen cycle is a planetary process that connects the atmosphere and hydrosphere with the earth's crust. The key links in this cycle are: the formation of free oxygen during photosynthesis in green plants, its consumption for the implementation of respiratory functions by all living organisms, for the oxidation reaction of organic residues and inorganic substances (for example, combustion of fuel) and other chemical transformations leading to the formation of such oxidized compounds, like carbon dioxide and water, and their subsequent involvement in a new cycle of photosynthetic transformations.

The use of oxygen for combustion and other anthropogenic activities should also be considered. It is assumed that in the foreseeable future the annual total consumption of oxygen will reach 210...230 billion tons. Meanwhile, the annual production of this gas by the entire phytosphere is 240 billion tons.

Phosphorus cycle

The Clarke of this element in the earth's crust is 0.093 %, which is several tens of times greater than the clarke of nitrogen. However V Unlike the latter, phosphorus does not play the role of one of the main elements of the Earth's shells. However, the geochemical cycle of phosphorus includes a variety of migration paths in the earth's crust, intensive biological cycling and migration in the hydrosphere. Phosphorus is one of the main organogenic elements. Its organic compounds play an important role in the life processes of all plants and animals, are part of nucleic acids, complex proteins, membrane phospholipids, and are the basis of bioenergetic processes. Phosphorus is concentrated in living matter, where its content is almost 10 times higher than in the earth's crust. On land there is an intense phosphorus cycle in the soil-plants-animals-soil system.

Sulfur cycle

A fairly developed process of cyclic transformations of sulfur and its compounds has formed in the biosphere. Reserve funds of this element are identified in soil and sediments (quite extensive), as well as in the atmosphere (small). In the sulfur exchange pool, the main role belongs to specialized microorganisms, some types of which perform oxidation reactions, others - reduction reactions. Nitrogen and sulfur cycles are increasingly affected by industrial air pollution. The combustion of fossil fuels significantly increases the release into the atmosphere (and, of course, the content in it) of volatile oxides of nitrogen (NO and NO2) and sulfur (SO2), especially in cities. The current concentration of these ingredients is already becoming dangerous for the biotic components of ecosystems.

Potassium cycle

Potassium, as is known, takes part in the processes of photosynthesis, affects carbohydrate, nitrogen and phosphorus metabolism, and significantly affects the osmotic properties of cells. It is concentrated in fruits and seeds, in intensively growing plant tissues and organs.

So far, the potassium cycle in the aquatic environment remains poorly understood. Every year, about 90 million tons of this element enter the World Ocean with water runoff. Some part is absorbed by aquatic organisms, but a significant amount is not recorded anywhere, and its subsequent movement is unknown.

Important integral part The cycles are ionic and solid sinks. The circulation of chemical elements, as a rule, takes place simultaneously in several adjacent shells of the Earth (atmosphere and hydrosphere, hydrosphere and pedosphere) or in all three geospheres simultaneously. The reliability and constancy of the circulation is ensured by the regular exchange of substances and energy between geospheres. This kind of directed connection is clearly demonstrated by the example of ionic runoff, which is the process of rivers carrying chemical elements from land in an ionic dissolved state into the World Ocean. Chemical elements arriving in ionic form, as on land, are exposed to living organisms in the aquatic environment, continuing the cycle. The migration of chemical elements in a dissolved state is a gigantic planetary process.

The solid matter of the Earth's surface does not remain motionless. It also participates in migration, moving by surface waters of land. Surface water, along with elements migrating in a dissolved state or with colloidal particles, transports huge masses of rock fragments and minerals, called solid runoff (by analogy with water runoff). A significant part of the solid runoff moves within the land, but the volumes entering the seas are quite large. Every year, 22.13 billion tons of detrital and clayey material enter the World Ocean from the continents, which is approximately 7 times the amount of dissolved substances carried out.

Biotechnosphere and noosphere

The uniqueness of biogeochemical migration cycles. The biosphere is not only an ideally organized system, but a kind of “mechanism” in which the connection and relationship between living and inert matter are subject to strict laws, as immutable as the laws of movement of the celestial bodies. Geochemically, these functions of life are carried out through the reproduction of organisms. Living matter overcomes the resistance of the environment and strives to spread to free territory.

The rate of reproduction is the rate of transmission of geochemical energy in the biosphere. It depends not only on astronomical parameters, but also on the speed of propagation of the solar ray in the environment, on the size of organisms, and on the geochemical energy contained in them.

An essential feature of living matter is its difference from the “inert” environment in spatial and temporal characteristics. Living matter corresponds to special, unique space and time.

The time of individual existence of living organisms is associated with the steadily progressing process of aging and death, which have a positive significance for the evolutionary process, since the fragility of living beings ensures not only a long and continuous circulation of biogenic material, but also significant variability in morphological forms.

Human impact on the biosphere

With increasing use natural resources, caused by the industrial revolution, the anthropogenic impact on the biosphere and its components is objectively increasing. The natural and multilateral process of growth of productive forces has significantly expanded the range of human impacts on nature (including negative ones). Vernadsky noted that production activity human destruction is acquiring a scale comparable to geological transformations. Thus, in addition to deforestation, plowing of virgin lands, soil erosion and salinization, and reduction in biodiversity, new permanent mechanical and physicochemical factors have been added that aggravate environmental risk.

Man already exploits more than 55% of the land, using about 13 % river waters, the rate of deforestation reaches 18 million hectares per year.

The impact on the biosphere comes down to four main forms:

Change of structure earth's surface(plowing of steppes, deforestation, land reclamation, creation of artificial lakes and seas, other changes in the surface water regime, etc.):

Changes in the composition of the biosphere, the circulation and balance of its constituent substances (removal of minerals, formation of waste dumps, release of various substances into the atmosphere and water bodies, changes in moisture circulation);

Changes in the energy, in particular heat, balance of individual areas globe, dangerous for the entire planet;

Changes made to the biota (the totality of living organisms) as a result of the extermination of certain species, the creation of new breeds of animals and plant varieties, and their movement to new habitats.

Considering the role of man in the evolution of the biosphere, they characterize the violation by man of the basic principles of the natural structure of the biosphere.

1. By accumulating energy in the form of complex organic compounds and dissipating it in the form of heat, nature has created an evolutionarily developed thermal balance, which humans disturb. When extracting energy resources, people destroy soils, vegetation dies or degrades, water bodies and the atmosphere are polluted, rock dumps are formed, which leads, in particular, to a rise in the level of groundwater and the appearance of a contour ring of lakes, swamps, etc. in the surrounding area.

2. Biogeochemical cycles of biogenic elements participating in natural cycles are worked out evolutionarily and do not lead to the accumulation of waste. Man uses the planet's substance extremely inefficiently; this generates a huge amount of waste, many of which are transferred from passive form, in which they were in the natural environment, into an active, toxic form. As a result, the biosphere is “enriched” with compounds unusual for it, i.e. the natural balance of chemical elements and substances is disrupted.

3. With a huge diversity of species, competitive and predatory relationships between them contribute to the establishment of biological balance. The path of humanity, unfortunately, is marked by the death of many representatives of flora and fauna. According to some reports, one biological species disappears every day on Earth.

4. Human activities have led to a disruption in population stability. The number of species accompanying humans (rats, cockroaches, etc.) is growing, and the number of many other populations, on the contrary, is declining, sometimes to a catastrophic extent, which puts the species in danger of complete extinction.

5. Expanding economic activity, people change parameters in a short time environmental factors; many species do not have time to adapt to such rapid changes.

Complex anthropogenic factors, affecting the state of the biosphere and the health of the population, is extremely diverse.

Biotechnosphere

Biotechnosphere- this is the area of ​​​​our planet in which living matter and human-created urban-technical objects exist and where their interaction and influence on the external environment are manifested. The biotechnosphere is a complex conglomerate of many subsystems controlled by humans. These subsystems do not accumulate, but consume energy, biomass and oxygen of the biosphere.

The biotechnosphere and its constituent technogenic subsystems are located in the biosphere, but they do not possess most of the properties and functions that are inherent in natural ecosystems.

As long as humanity exists, the biotechnosphere will develop. But the technosphere must be in a state of ecological self-sufficiency, consistent with the laws of nature and meeting the needs human society. At the same time, society must purposefully and intelligently influence the forces of nature.

Noosphere

Noosphere- the highest stage of development of the biosphere, characterized by the preservation of all natural patterns inherent in the biosphere (with high level development of productive forces, scientific organization of society’s influence on nature), the maximum capabilities of society to satisfy the material and cultural needs of man.

The noosphere is a new state of the biosphere, based on the universal connection between nature and society, when the further evolution of planet Earth becomes guided by reason.

He considers the need to transfer the biosphere to the noosphere as a guarantor of survival modern man.

The transition to the noosphere is a difficult and slow process of developing principles of coordinated action, new behavior of people, a change in standards, and a restructuring of all existence. Humanity must begin to rationally regulate its numbers and significantly reduce the negative pressure on nature, and subsequently develop deeply substantiated technologies for building the noosphere on the basis of preserving the biosphere as a mandatory condition of life.

There is a constant exchange of chemical elements between the lithosphere, hydrosphere, atmosphere and living organisms of the Earth. This process is cyclical: having moved from one sphere to another, the elements return to their original state. The cycle of elements has taken place throughout the history of the Earth, which spans 4.5 billion years.

Gigantic masses chemical substances transported by the waters of the World Ocean. This primarily applies to dissolved gases - carbon dioxide, oxygen, nitrogen. Cold water at high latitudes dissolves atmospheric gases. Coming with ocean currents into the tropical zone, it releases them, since the solubility of gases decreases when heated. The absorption and release of gases also occurs during the change of warm and cold seasons of the year.

The emergence of life on the planet had a huge impact on the natural cycles of some elements. This, first of all, refers to the circulation of the main elements of organic matter - carbon, hydrogen and oxygen, as well as such vital elements as nitrogen, sulfur and phosphorus. Living organisms also influence the cycle of many metal elements. Despite the fact that the total mass of living organisms on Earth is millions of times less than the mass of the earth's crust, plants and animals play a vital role in the movement of chemical elements.

Human activities also influence the cycle of elements. It has become especially noticeable in the last century. When considering chemical aspects global changes Chemical cycles must take into account not only changes in natural cycles due to the addition or removal of chemicals present in them as a result of normal cyclic or human-induced influences, but also the entry into the environment of chemicals that did not previously exist in nature. Let's consider one of the most important examples of the cyclic movement and migration of chemical elements.

Carbon, the basic element of life, is found in the atmosphere in the form of carbon dioxide. In the ocean and fresh waters of the Earth, carbon is found in two main forms: as part of organic matter and as part of interconnected inorganic particles: bicarbonate ion, carbonate ion and dissolved carbon dioxide. A large amount of carbon is concentrated in the form of organic compounds in animals and plants. There is a lot of "non-living" organic matter in the soil. Lithosphere carbon is also contained in carbonate minerals (limestone, dolomite, chalk, marble). Some carbon is found in oil, coal and natural gas.

The connecting link in the natural carbon cycle is carbon dioxide (Fig. 1).

Simplified diagram of the global carbon cycle. The numbers in the boxes represent reservoir sizes in billions of tons—gigatons (Gt). The arrows show flows and the associated numbers are expressed in Gt/year.

The largest reservoirs of carbon are marine sediments and sedimentary rocks on land. However, most of this material does not interact with the atmosphere but cycles through the solid Earth on geological time scales. Therefore, these reservoirs play only a minor role in the relatively rapid carbon cycle that occurs with the participation of the atmosphere. The next largest reservoir is seawater. But even here, the deep part of the oceans, where the bulk of carbon is contained, does not interact with the atmosphere as quickly as their surface. The smallest reservoirs are the terrestrial biosphere and the atmosphere. It is the small size of the latter reservoir that makes it sensitive to even small changes in the percentage of carbon in other (larger) reservoirs, such as when burning fossil fuels.

The modern global carbon cycle consists of two smaller cycles. The first of them is the binding of carbon dioxide during photosynthesis and its new formation during the life of plants and animals, as well as during the decomposition of organic residues. The second cycle is caused by the interaction of atmospheric carbon dioxide and natural waters:

Over the last century, significant changes have been made to the carbon cycle. economic activity person. The burning of fossil fuels - coal, oil and gas - has increased the release of carbon dioxide into the atmosphere. This does not greatly affect the distribution of carbon masses between the Earth’s shells, but it can have serious consequences due to the strengthening of the greenhouse effect.

Cycle in nature
The activity of living organisms is accompanied by the extraction of large quantities of minerals from the surrounding inanimate nature. After
When organisms die, their constituent chemical elements are returned to the environment. This is how the biogenic cycle of substances arises in nature, i.e.
circulation of substances between the atmosphere, hydrosphere, lithosphere and living organisms.
Let's give some examples.
The water cycle.
Under the influence of solar energy, water evaporates from the surface of reservoirs and is transported over long distances by air currents. Falling on
the surface of the land in the form of precipitation, it contributes to the destruction of rocks and makes their constituent minerals available to plants,
microorganisms and animals. It erodes the top soil layer and leaves along with the chemical compounds dissolved in it and suspended
organic and inorganic particles into the seas and oceans. The circulation of water between the ocean and land is the most important link in maintaining life on Earth.
Plants participate in the water cycle in two ways: they extract it from the soil and evaporate it into the atmosphere; part of the water in plant cells
is broken down during photosynthesis. In this case, hydrogen is fixed in the form of organic compounds, and oxygen enters the atmosphere.
Animals consume water to maintain osmotic and salt balance in the body and release it into the external environment along with food
metabolism.
Carbon cycle.
Carbon enters the biosphere as a result of its fixation during photosynthesis. The amount of carbon sequestered by plants each year is
is estimated at 46 billion tons. Part of it enters the body of animals and is released as a result of respiration in the form of CO2, which again enters the atmosphere.
In addition, carbon reserves in the atmosphere are replenished due to volcanic activity and human combustion of fossil fuels. Although the main part
carbon dioxide entering the atmosphere is absorbed by the ocean and deposited in the form of carbonates, the CO2 content in the air slowly but steadily
rises.
Nitrogen cycle.
Nitrogen, one of the main biogenic elements, is found in enormous quantities in the atmosphere, where it makes up 80% of the total mass of its gaseous
components. However, in molecular form it cannot be used by either higher plants or animals.
Atmospheric nitrogen is converted into a usable form by electrical discharges (in which nitrogen oxides are formed, in combination with
water producing nitrous and nitric acids), nitrogen-fixing bacteria and blue-green algae. At the same time, ammonia is formed, which others
chemosynthetic bacteria successively convert into nitrites and nitrates. The latter are most digestible for plants. Biological nitrogen fixation
on land it is approximately 1 g/m2, and in fertile areas it reaches 20 g/m2.
After the organisms die, putrefactive bacteria decompose nitrogen-containing compounds into ammonia. Some of it goes into the atmosphere, some
is reduced by denitrifying bacteria to molecular nitrogen, but the bulk is oxidized to nitrites and nitrates and used again.
A certain amount of nitrogen compounds settles in deep-sea sediments and is excluded from the cycle for a long time (millions of years). These losses
compensated by the entry of nitrogen into the atmosphere with volcanic gases.
Sulfur cycle.
Sulfur is part of proteins and is also a vital element. In the form of compounds with metal sulfides, it occurs in the form of ores
on land and is part of deep-sea sediments. These compounds are converted into a soluble form accessible for absorption by chemosynthetic
bacteria capable of obtaining energy by oxidizing reduced sulfur compounds. As a result, sulfates are formed, which are used
plants. Deeply buried sulfates are involved in the cycle by another group of microorganisms that reduce sulfates to hydrogen sulfide.
Phosphorus cycle.
Phosphorus reservoirs are deposits of its compounds in rocks. Due to leaching, it ends up in river systems and is partially used
plants, and partly is carried into the sea, where it settles in deep-sea sediments. In addition, from 1 to 2 million tons of phosphorus-containing minerals are mined annually in the world.
breeds Much of this phosphorus is also washed out and removed from the cycle. Fishing returns some of the phosphorus to land in small quantities.
sizes (about 60 thousand tons of elemental phosphorus per year).
From the above examples it is clear what a significant role living organisms play in the evolution of inanimate nature. Their activities are significantly
influences the formation of the composition of the atmosphere and the earth's crust. A great contribution to the understanding of the relationships between living and inanimate nature was made by the outstanding
Soviet scientist V.I. Vernadsky. He revealed the geological role of living organisms and showed that their activity is the most important factor
transformation of the mineral shells of the planet.
Thus, living organisms, being influenced by factors of inanimate nature, change the environmental conditions through their activities.
environment, i.e. their habitat. This leads to a change in the structure of the entire biocenosis community.
It has been established that nitrogen, phosphorus and potassium can have the greatest positive effect on the yields of cultivated plants, and therefore these three
element in the largest quantities is added to the soil with fertilizers used in agriculture. Therefore, nitrogen and phosphorus turned out to be the main reason
accelerated eutrophication of lakes in countries with intensive agriculture. Eutrophication is the process of enriching water bodies with nutrients. She
is a natural occurrence in lakes as rivers bring nutrients from surrounding drainage areas. However, this process
usually goes very slowly, over thousands of years.
Unnatural eutrophication, leading to rapid increases in lake productivity, occurs as a result of runoff from agricultural
lands that can be enriched with nutrients from fertilizers.
There are also two other important sources of phosphorus, wastewater and detergents. Wastewater, both in its original form and
processed, enriched with phosphates. Household detergents contain 15% to 60% biodegradable phosphate. It can be briefly summarized that
Eutrophication ultimately leads to the depletion of oxygen resources and the death of most living organisms in lakes, and in extreme situations, in
rivers
Organisms in an ecosystem are connected by a commonality of energy and nutrients, and it is necessary to clearly distinguish between these two concepts. The entire ecosystem
can be likened to a single mechanism that consumes energy and nutrients to do work. Nutrients initially
originate from the abiotic component of the system, to which they ultimately return either as waste products or after death
and destruction of organisms. Thus, a constant cycle of nutrients occurs in the ecosystem, in which both living and nonliving things participate.
Components. Such cycles are called biogeochemical cycles.
At a depth of tens of kilometers, rocks and minerals are exposed to high pressures and temperatures. As a result, it happens
metamorphism (change) of their structure, mineral, and sometimes chemical composition, which leads to the formation of metamorphic rocks.
As metamorphic rocks descend further into the Earth, they can melt and form magma. Internal energy of the Earth (i.e. endogenous
force) lifts magma to the surface. With molten rocks, i.e. magma, chemical elements are carried to the surface of the Earth during
volcanic eruptions, solidify in the thickness of the earth's crust in the form of intrusions. Mountain building processes raise deep rocks and minerals to
ground surface. Here rocks are exposed to the sun, water, animals and plants, i.e. are destroyed, transported and deposited as
precipitation in a new location. As a result, sedimentary rocks are formed. They accumulate in moving zones of the earth's crust and when bending down again
descend to great depths (over 10 km).
The processes of metamorphism, transportation, crystallization begin again, and chemical elements return to the surface of the Earth. Such
The "route" of chemical elements is called the great geological cycle. The geological cycle is not closed, because part of chemical elements
comes out of the cycle: it is carried into space, fixed by strong bonds on the earth's surface, and part comes from the outside, from space, with meteorites.
The geological cycle is the global journey of chemical elements within the planet. They make shorter trips on Earth in
within its individual sections. The main initiator is living matter. Organisms intensively absorb chemical elements from soil, air and water. But
at the same time and return them. Chemical elements are washed out of plants by rainwater, released into the atmosphere during respiration and deposited in
soil after the death of organisms. The returned chemical elements are again and again involved in “travel” by living matter. Everything together makes up
biological, or small, cycle of chemical elements. He is also not closed.
Some of the “traveler” elements are carried away beyond its boundaries with surface and groundwater, some are “switched off” from the
cycle and lingers in trees, soil, and peat.
Another route of chemical elements runs from top to bottom from peaks and watersheds to valleys and river beds, depressions, depressions. On
watersheds, chemical elements enter only with precipitation, and are carried down both with water and under the influence of gravity. Substance consumption
predominates over the supply, as evidenced by the very name of the eluvial watershed landscapes.
On the slopes, the life of chemical elements changes. The speed of their movement increases sharply, and they “drive” the slopes like passengers,
comfortably seated in a train compartment. Slope landscapes are called transit.
Chemical elements can “take a break” from the road only in accumulative landscapes located in depressions of the relief. IN
in these places they often remain, creating for vegetation good conditions nutrition. In some cases, vegetation already has to contend with
excess of chemical elements.
Many years ago, humans intervened in the distribution of chemical elements. Since the beginning of the twentieth century, human activity has become the main way
their travels. During mining, huge amounts of substances are removed from the earth's crust. Their industrial processing is accompanied by
emissions of chemical elements from production waste into the atmosphere, water, and soil. This pollutes the habitat of living organisms. On the ground
new areas with high concentrations of chemical elements appear; man-made geochemical anomalies. They are common around mines
non-ferrous metals (copper, lead). These areas sometimes resemble lunar landscapes because they are practically devoid of life due to the high content
harmful elements in soils and waters. It is impossible to stop scientific and technological progress, but people must remember that there is a threshold in pollution
natural environment, which cannot be crossed, beyond which human illnesses and even the extinction of civilization are inevitable.
By creating biogeochemical “dumps,” nature may have wanted to warn man from ill-conceived, immoral activities, to show him
using a clear example of what a disruption in the distribution of chemical elements in the earth’s crust and on its surface leads to.

Cycle of nutrients. In addition to the basic elements considered, a number of others take part in the metabolic process of a living organism. Some of them are present in significant quantities and belong to the category of macronutrients, such as sodium, potassium, calcium, magnesium. Some elements are contained in very small concentrations (microelements), but they are also vital (iron, zinc, copper, manganese, etc.).[...]

Cycles of basic nutrients and elements. Let's consider the cycles of the most significant substances and elements for living organisms (Fig. 3-8). The water cycle is a large geological cycle; and the cycles of biogenic elements (carbon, oxygen, nitrogen, phosphorus, sulfur and other biogenic elements) - to small biogeochemical.[...]

The rate of cycles of nutrients is quite high. The turnover time of atmospheric carbon is about 8 years. Each year, approximately 12% of the carbon dioxide in the air is recycled into the cycle in terrestrial ecosystems. The total cycle time for nitrogen is estimated at more than 110 years, for oxygen at 2500 years.[...]

Biotic cycle. The cycle of nutrients caused by the synthesis and decay of organic substances in the ecosystem is called the biotic cycle of substances. In addition to biogenic elements, the biotic cycle involves mineral elements that are most important for the biota and many different compounds. Therefore, the entire cyclic process of chemical transformations caused by biota, especially when it comes to the entire biosphere, is also called the biogeachemical cycle.[...]

Biotic cycle is the circulation of nutrients and other substances involved in them in ecosystems, in the biosphere between their biotic and abiotic components. The most important feature of the biosphere biotic cycle is a high degree of isolation.[...]

On the other hand, biogenic elements as components of biomass simply change molecules, which include, for example, nitrate N-protein N-waste N. They can be used repeatedly, and their cycle characteristic. Unlike energy solar radiation reserves of nutrients are variable. The process of binding some of them into living biomass reduces the amount remaining to the community. If plants and phytophages did not eventually decompose, the supply of nutrients would be exhausted and life on Earth would cease. The activity of heterotrophic organisms is a decisive factor in maintaining the cycles of nutrients and the formation of products. In Fig. 17.24 shows that the release of these elements in the form of simple inorganic compounds occurs only from the decomposer system. In reality, a certain proportion of these simple molecules (especially CO2) is also provided by the consumer system, but in this way a very small part of the biogenic elements returns to the cycle. The decisive role here belongs to the system of decomposers.[...]

Driving forces The circulation of substances is served by the flow of solar energy and the activity of living matter, leading to the movement of huge masses of chemical elements, concentration and redistribution of energy accumulated during the process of photosynthesis. Thanks to photosynthesis and continuously operating cyclic cycles of nutrients, a stable organization of all ecosystems and the biosphere as a whole is created, and their normal functioning is carried out.[...]

In the absence of external flows of biogenic compounds, the biosphere can exist stably only if there is a closed cycle of substances, during which nutrients perform closed cycles, alternately moving from the inorganic part of the biosphere to the organic and so on. vice versa. This cycle is carried out by living organisms of the biosphere. It is believed that the biosphere contains about 1027 living organisms that are not correlated with each other. In the process of evolutionary development of the biosphere, the following three groups of organisms were formed, differing in their functional purpose and participation in the cycle of nutrients: producers, decomposers and consumers.[...]

Material processes in living nature, cycles of biogenic elements are associated with energy flows with stoichiometric coefficients that vary within the most diverse organisms only within one order of magnitude. Moreover, due to the high efficiency of catalysis, the energy consumption for the synthesis of new substances in organisms is much less than in the technical analogues of these processes.[...]

A very important conclusion for practice, arising from many intensive studies of the cycle of nutrients, is that an excess of fertilizers can be just as unprofitable for humans as their deficiency. If more substance is introduced into the system than can be used by the active substances this moment organisms, the excess is quickly bound by soil and sediments or lost by leaching, becoming unavailable precisely at the time when growth of organisms is most desirable. Many people mistakenly believe that if 1 kg of fertilizer (or pesticide) is recommended for a certain area of ​​their garden or pond, then 2 kg will bring twice as much benefit. These more-is-better proponents would do well to understand the subsidy-stress relationship illustrated in Figure 1. 3.5. Subsidies inevitably become a source of stress if not applied carefully. Excessive fertilization of ecosystems such as fish ponds is not only wasteful in terms of results achieved, but can cause unforeseen changes in the system, as well as contaminate downstream ecosystems. Since different organisms are adapted to different levels of element content, prolonged overfertilization leads to changes in the species composition of organisms, and those we need may disappear and unnecessary ones may appear.[...]

Many processes occurring in the soil are associated with the vital activity of soil microorganisms - cycles of nutrients, mineralization of animal and plant residues, enrichment of the soil with forms of nitrogen available to plants. Soil fertility is related to the activity of microorganisms. Consequently, soil microorganisms directly influence plant life, and through them, animals and humans, being one of the main parts of terrestrial ecosystems.[...]

Ponds and lakes are especially convenient for research, since over a short period of time the cycles of nutrients in them can be considered independent. Hutchinson (1957) and Pomeroy (1970) published reviews of work on the phosphorus cycle and the cycles of other vital elements.[...]

Transpiration also has its own positive sides. Evaporation cools the leaves and, among other processes, promotes the cycling of nutrients. Other processes are transport of ions through the soil to the roots, transport of ions between root cells, movement within the plant, and leaching from leaves (Kozlowski, 1964, 1968). Some of these processes require metabolic energy, which can limit the rate of transport of water and salts (Fried and Broeshart, 1967). Thus, transpiration is not simply a function of exposed physical surfaces. Forests do not necessarily lose more water than grassy vegetation. The role of transpiration as an energy subsidy in humid forest conditions was discussed in Chap. 3. If the air is too humid (relative humidity approaches 100%), as happens in some tropical cloud forests, the trees are stunted and most of the vegetation consists of epiphytes, apparently due to the lack of transpiration. traction" (N. Odum, Pigeon, 1970).[...]

Energy cannot be transferred in closed cycles and reused, but matter can. - Matter (including nutrients) can pass through a community in “loops”. - The cycle of nutrients is never perfect. - Study of the Hubbard Brook Forest. ■-The input and output of nutrients is usually low compared to the amount participating in the cycle, although sulfur is an important exception to this rule (mainly due to “acid rain”), - Deforestation opens the cycle and leads to loss of nutrients.- Terrestrial biomes differ in the distribution of nutrients between dead organic matter and living tissues, - Currents and sedimentation are important■ factors affecting the flow of nutrients in aquatic ecosystems.[...]

All people consume food, being consumers of the 1st and 2nd order in food chains. They secrete products of physiological metabolism that are utilized by decomposers participating in the cycle of nutrients. Man is one of the 3 million currently known biological species on Earth.[...]

Any ecosystem can be thought of as a series of blocks through which different materials pass and in which these materials can remain for varying periods of time (Figure 10.3). In the cycles of mineral substances in an ecosystem, as a rule, three active blocks are involved: living organisms, dead organic detritus and available inorganic substances. Two additional blocks - indirectly accessible inorganic substances and precipitating organic substances - are associated with the cycles of nutrients in some peripheral parts of the general cycle (Fig. 10.3), however, the exchange between these blocks and the rest of the ecosystem is slow compared to the exchange occurring between active blocks .[...]

Carbon, nitrogen and phosphorus are important in the life of organisms. It is their compounds that are necessary for the formation of oxygen and organic matter in the process of photosynthesis. Bottom sediments play a significant role in the cycle of nutrients. In one case they are a source, in another - an accumulator of organic and mineral resources of a reservoir. Their supply from bottom sediments depends on pH, as well as on the concentration of these elements in water. With an increase in pH and a low concentration of nutrients, the supply of phosphorus, iron and other elements from bottom sediments into the water increases.[...]

An important task of studying the structure and functioning of communities (biocenoses) is to study the stability of communities and their ability to withstand adverse impacts. When studying ecosystems, it becomes possible to quantitatively analyze the cycle of matter and changes in energy flow during the transition from one nutritional level to another. This production-energy approach at the population and biocenotic levels allows us to compare various natural and human-created ecosystems. Another task of environmental science is to study various types connections in terrestrial and aquatic ecosystems. It is especially important to study the biosphere as a whole: determining primary production and destruction throughout the globe, the global cycle of nutrients; these problems can only be solved by the combined efforts of scientists different countries.[ ...]

The periodic system in chemistry, the laws of motion of celestial bodies in astronomy, etc.) These patterns are manifested, for example, in the presence of the same species (or the same forms of growth, productivity, rates of circulation of biogenic elements, etc. ) in various places. This in turn leads to the creation of hypotheses about the reasons for such recurrence. Hypotheses can then be tested by further observations or experiments.[...]

All forms of relationships together form a mechanism of natural selection and ensure the stability of the community as a form of organization of life. Community is the minimal Form of organization of life. capable of functioning for an almost unlimited time in a certain area of ​​the territory. Only at the community level can the cycle of nutrients be carried out in a certain area of ​​the territory, without which it is impossible to ensure unlimited life expectancy with limited life resources of the territory.[...]

As a result of the life activity of organisms, two opposing and inseparable processes occur. On the one hand, living organic matter is synthesized from simple abiotic components, on the other hand, organic compounds are destroyed into simple abiotic substances. These two processes ensure the exchange of substances between the biotic and abiotic components of ecosystems and constitute the main core of the biogeochemical cycle of nutrients. [...]

Back in the seventies of the 20th century, chemist James Lovelock and microbiologist Lynn Margulis put forward a theory of complex regulation of the Earth's atmosphere by biological objects, according to which plants and microorganisms, together with the physical environment, ensure the maintenance of certain geochemical conditions on Earth that are favorable for life. This is a relatively high content of oxygen in the atmosphere and a low content of carbon dioxide, certain humidity and air temperature. A special role in this regulation belongs to microorganisms of terrestrial and aquatic ecosystems, ensuring the circulation of nutrients. The regulatory role of microorganisms in the World Ocean in maintaining a certain amount of carbon dioxide in the Earth’s atmosphere and in preventing the greenhouse effect is well known.[...]

The reproductive potential of living matter is enormous. If dying were stopped for some time and reproduction and growth were not limited in any way, then a “biological explosion” on a cosmic scale would occur: in less than two days, the biomass of microorganisms would be several times greater than the mass of the globe. This does not happen due to substance limitation; The biomass of the ecosphere is maintained at a relatively constant level for hundreds of millions of years. With constant pumping by a flow of solar energy Live nature overcomes the limitation of nutrient material by organizing the cycles of nutrients. This ensures high productivity of many ecosystems (see Table 2. 1).[...]

Anthropogenic pressure on nature is not limited to pollution. Equally important is the exploitation of natural resources and the resulting disruptions to ecological systems. Environmental management is very expensive - much more than the usual monetary value of the resources consumed. First of all, because in the economy of nature, as well as in the human economy, there are no free resources: space, energy, sunlight, water, oxygen, no matter how inexhaustible their reserves on Earth may seem, are strictly paid for by any system that consumes them, paid for completeness and speed of return, turnover of values, closedness of material cycles - nutrients, energy, food, money, health... Because in relation to all this, the law of limited resources applies.