Environmental aspects of teaching chemistry at school
Introduction
In our difficult times. When chemistry as a science became a social outcast. We have to reconsider both the content of the subject and the methods of teaching it, changing not only the emphasis, but the priorities in order to overcome chemophobia.
The main questions of the course should be determined by both the importance of acquiring knowledge for the development of students’ intelligence, and the relevance of this knowledge in a person’s real life and in his practical activities. From this point of view, progress in chemical education is necessary, since without it it is impossible to satisfy the objective needs of society for the widespread use of the achievements of chemical science and industry.
The concept of modern school chemical education is based on the principles of humanization, individualization and differentiation of education, much attention is paid to environmental aspects, the development of general culture, strengthening the health of schoolchildren, and increasing their environmental literacy.
Current topics.
Chemistry, as one of the fundamental fields of knowledge, largely determines the development of other important areas of science and technology. It is known that without chemistry, chemical processes and chemical products, not a single production, not a single branch of the modern economy and social sphere can exist.
It is necessary to ensure that students understand the practical significance of chemistry and its connection with everyday life. They must be convinced of the possibility of finding, through chemistry, answers to other “whys” from the sphere of their life and production interests. It is especially important to resolve the issue of basic “chemical” preparedness of people, because today almost every one of us comes into contact with substances that can cause harm to humans. However, not many of the consumers who use drugs, cosmetics and perfumes, dyes, plastics, fertilizers, fibers, various types of fuels, etc. are aware of the dangers associated with the use. This contradiction causes many troubles that befall people. Unfortunately, in most schools, active educational work with students related to the characterization of the basic properties of chemical compounds common in everyday life and in production, especially in terms of their impact on the environment, is carried out extremely weakly and irregularly. Basically, students receive only general theoretical ideas that are not adapted to the realities of life and especially to environmental issues.
A negative attitude towards chemistry leads to inability to adapt to civilized, modern life, environmental illiteracy, the consequence of which will not only be disadvantaged in the education of schoolchildren, but also the preparation of environmental time bombs. This will only deepen the conflict between man and nature.
In recent years, work related to chemical-ecological education has been started in a number of scientific and educational centers in different countries, but often they were of a declarative nature.
I see my task as instilling in students a desire to acquire knowledge; make sure that the learning process itself captivates them; contributed to the development of cognitive activity and interest in the subject. For this purpose, I include consideration of environmental and valeological issues in the chemistry course curriculum. This program is aimed at developing in students natural scientific ideas about the world around them and its laws, humanistic relations and environmentally literate behavior, and intellectual moral improvement of students. The content of the program prepares children for a conscious perception of the chemical picture of the world and offers the implementation of an integrated principle, i.e., it requires students to apply knowledge and skills from various subjects of the natural cycle. The relevance of the work is due to a set of problems consisting in overcoming the well-known abstractness of the subject of chemistry, bias in its assessment, and the relationship of chemical concepts with the environmental aspects of real human life.
Goals and objectives of the work:
Consideration of the basic principles of greening chemical education;
Analysis of forms and methods (techniques) of forming an ecological culture in teaching chemistry;
Characteristics of the role of man in the process of cognition, transformation and use of nature.
The practical significance of the work lies in the fact that it contains methodological studies of environmental comments to the main provisions of the chemistry course, allowing one to master the laws of chemistry using specific environmental examples; consideration of methods for developing a conscious attitude towards nature, environmentally literate behavior in unfavorable environmental conditions.
The results of the implementation of work at Lyceum No. 4 showed its effectiveness and practical value, increasing student interest in subjects of the natural and ecological cycle; made it possible to rethink various approaches to the consideration of the use of chemistry achievements in practical human activities, to the significance of the applied nature of chemical knowledge.
Approbation of work. The main results of the work were reported and discussed at the pedagogical councils of Lyceum No. 4, at meetings of the scientific and methodological council of the department of natural and ecological cycle of the lyceum. At a seminar for school directors in the Kominternovsky district, a lesson was given on “Heat engines and environmental protection” together with a physics teacher, based on the physical, chemical, and environmental aspects of the problem. Based on the materials of the work, articles were published in the collection “Education of Voronezh at the turn of the century. Educational field "Natural Science". Chemistry “On the verge of two millennia, at the turn of two centuries.”
CHAPTER 1
The state of the problem of greening the teaching of chemistry in
science and practice.
1.1. The need to introduce environmental education in secondary schools and its basic principles.
Among the modern problems facing the world community, one particularly stands out - the problem of deterioration in the quality of the human environment. It is global in nature and worries people of all countries. The first country to feel the negative impact of chemical pollution of the natural environment was Japan. In this country, over 80% of the territory is directly influenced by industrial production. The Japanese were the first to talk about the problem of "kogai", meaning the danger of harm from environmental pollution. Soon other countries also encountered this problem. The increase in environmental pollution is visible and causes emotional criticism from people. Usually the main complaints of the population are addressed to chemistry. Meanwhile, in terms of pollution, the chemical industry is noticeably inferior to the fuel and energy complex, motor transport, ferrous and non-ferrous metallurgy, and even industry. In recent years, the most unfavorable situation has been the pollution of the atmosphere of the city of Voronezh with benzopyrene contained in car exhausts and dust, the proportion of which in non-standard laboratory analyzes daily is 15-20%. An ecological and geochemical survey of the soil cover showed that the situation with regard to soil contamination with lead and zinc is very unfavorable. The share of unsatisfactory analyzes of soil samples in the city as a whole is 19.3 and 15.5%, respectively, and in the industrial right-bank part of the city this value increases to 40-46%. Meanwhile, these ingredients are specific indicators of an increase in the disease in children. Among childhood diseases in Voronezh, respiratory diseases predominate (65%), the level of which exceeds the similar Russian average by 1.2 times for the city as a whole. Prevention of increased control also requires neoplasms and congenital anomalies, the spatial differences in levels of which reliably correlate with the intensity of environmental pollution.
Connections have been established between concentrations of formaldehyde in the atmosphere and the disease bronchial asthma, as well as high levels of dust in the atmosphere with blood diseases. Pneumonia is more often recorded in areas with high levels of lead and carbon monoxide. As the intensity of air pollution increases, children experience pronounced changes in hematological parameters and a corresponding increase in morbidity.
In the current conditions, it is necessary to conduct an objective analysis of the reasons for the expansion of environmental pollution and the increase in disasters associated with the uncontrolled spread of chemical compounds of technical or biological origin. It is difficult to carry out such an analysis, but two main aspects of the overall problem can be identified. The first aspect relates to the fields of politics and sociology and concerns contradictions in economic development.
The second aspect is related to the preparedness of the person himself to use the achievements of natural sciences in the production and domestic spheres.
An easy, purely technocratic attitude towards nature and outright environmental ignorance have led to a number of disasters with irreversible consequences. The facts of monstrous pollution are very eloquent and are hotly condemned by the population. However, relapses that occurred were rarely analyzed and were usually assessed only from an emotional point of view. This is how chemophobia arose. Meanwhile, a strict account of the circumstances shows that the environmental breakdowns that occur are usually determined not by the peculiarities of chemistry, but only by the low qualifications and not always proper morality of workers.
The root cause of all the noted troubles, except for errors in planning and construction, are long-standing omissions in the teaching of chemistry in high school and, as a consequence of this, the population’s lack of chemical knowledge. A striking contradiction emerges; All people systematically deal with chemicals and processes, but only a few can correct their actions with understanding. However, it should be noted that it is in chemistry lessons that one can clearly and convincingly demonstrate both the negative aspects of human intervention in the natural environment, and possible ways to optimize anthropogenic influences on it.
Painstaking work is needed to change human consciousness in relation to environmental management and education, instilling an environmental culture.
The strategy of environmental management, based on the idea of the power of man and his growth over nature in the era of scientific and technological revolution, which for a long time seemed unshakable, in fact turned out to be just a strategy of the “apple tree ideology of our relationship to nature”, which involves a lot of work to rebuild the consciousness of people, to green it. Awareness of this situation contributed to the formulation of serious tasks, both in the practical field and in the field of fundamental scientific research. Representatives of a variety of sciences, not only natural sciences, but also the humanities, began to study environmental problems. This is due to the fact that, along with the need to develop a new strategy for environmental management and create fundamentally new industrial technologies, the task of ecological restructuring of people’s consciousness and widespread propaganda of environmental knowledge has become necessary.
The main thing is the implementation of the decisions made, which ultimately depends on ourselves, our knowledge, beliefs, and will. Here we need fundamentally new ecological thinking, overcoming consumer psychology in relation to nature. Society must know the basic laws of the development of nature, find ways to solve problems, learn to make decisions in situations of moral choice and forecast, that is, go through the entire chain from environmental knowledge to environmental thinking and environmentally justified behavior.
The formation of a high ecological culture is possible provided that the content of school education includes the following elements: a system of knowledge about the interaction of society and nature; value environmental orientations; a system of norms and rules for relating to nature, the ability and skills to study and protect it.
Environmental education and upbringing is one of the main tasks of the school.
1.2. Contents of environmental education in chemistry lessons.
Environmental education and environmental education are two main emphases related to the formation of attitudes towards nature. With environmental education, the teacher’s attention is focused on the process of transferring and assimilation by students of accumulated experience in environmental relations, and with environmental education - on the formation of appropriate personality qualities. The ultimate goal of environmental education and upbringing is the same - the formation of optimal relationships between a person and his environment. Implemented within the framework of a single pedagogical process. In essence, the final goal is much deeper. It consists of providing conditions for the intellectual, personal and social development of students, instilling in them a sense of personal responsibility for the state of the environment, the desire to deeply understand the essence and inconsistency of the ongoing changes in the ecological development of our planet
The system of environmental knowledge should provide a turning point in people's consciousness, their worldview, and attitudes towards natural resources. Ecology has become a sign of the modern stage of development of universal human culture. Therefore, the goal of environmental education is the formation of an environmental culture. The concept of ecological culture includes knowledge and skills, the level of moral and aesthetic development of worldview, methods and forms of communication between people
The content of environmental education is so rich and diverse that it cannot be developed within the framework of one or several subjects. Therefore, teachers talk about the interdisciplinary nature of environmental education, the wide possibilities of almost all academic subjects and the special importance of each in the formation of students’ environmental culture. An example of this is the implementation of environmental knowledge in elementary school, not only in the “Natural History” course, but also in the new curricula of school disciplines. The courses being developed are aimed at involving all students in the process of comprehensive knowledge of the world and increasing the general level of their knowledge. Priority in new programs is given to those subjects that are more significant at present and remain relevant for the next decades.
An interdisciplinary approach requires defining the function of each subject in the general system of environmental education, highlighting interdisciplinary connections, generalizing interdisciplinary approaches that form the integrity of all academic disciplines united by the goal of understanding the surrounding world. The content of academic disciplines requires interdisciplinary coordination and step-by-step integration of relevant knowledge.
Environmental education is inextricably linked with knowledge of the dialectical nature of the interaction of elements in the “man-society-nature” system. The reflection of this trinity constitutes the core, which in the content of general education makes it possible, at the level of inter-cycle connections, to reveal the world of nature and the world of people as a single whole.
The model of environmental education includes not only a content structure, but also the basic conditions for achieving the goal.
https://pandia.ru/text/78/141/images/image002_5.gif" width="612" height="372">Factors in environmental education that determine schoolchildren’s responsible attitude towards the natural environment.
It should be explained to the younger generation that the current state of the environment poses the same danger to humanity as nuclear war. The only difference is that environmental problems are more insidious... A dangerous delusion is the consolation of the hope that humanity will be able to stop destroying the world around us when it comes close to ecological destruction. It will be late! This is the whole insidiousness of the problem.
Smart, subtle environmental education and the education of new generations is the force that can still freeze and turn back the clocked arrows of the monstrous mechanism that threatens the destruction of our planet. .
Knowledge of the essence of the world around us acts as an integrating link in the subjects of the natural cycle, and an important role in the greening of education is given to the teaching of chemistry.
Along with mastering the fundamentals of basic science, including its language, the most important facts, concepts, theories and laws, accessible generalizations of the ideological nature of teaching chemistry should contribute to: the development and intellectual improvement of the individual; formation in students of environmentally appropriate behavior, a reasonable attitude towards themselves, people, and the natural environment; developing an understanding of the social need for the development of chemistry, developing students’ attitudes towards chemistry as a possible area of future practical activity.
The selection of environmental material for inclusion in chemistry curricula should be carried out taking into account the basic principles of didactics. The main criteria are scientific character, accessibility for study, logical connection with the content of the academic subject, which allows for a pedagogically sound selection of questions on the chemical aspects of ecology, development of content and methods for studying them in chemistry lessons.
What place does chemical education occupy in the overall system of environmental education?
Traditionally, the main goal of teaching chemistry is that the student had to be introduced to the world of substances (both natural and man-made), to lay the foundation for understanding the causes of its diversity, to form not only a general understanding of the methods of obtaining and areas of application of substances, but also practical skills handle them. Insufficient information about the biological role of substances, their harmful effects on the human body and the environment has raised another educational challenge in
teaching chemistry - on the basis of Fundamental chemical knowledge to form systematic knowledge about the chemical aspects of ecology and environmental problems. This system includes knowledge about the substances of living nature, about the interactions associated with the manifestation of life in the plant and animal world, about the chemical relationships of organisms with each other and the environment, about the interaction of anthropogenic factors both on the person himself and on all living things
The system of ecological and chemical-ecological concepts in chemical education includes issues of the cycle of substances in nature, changes and transformations of energy in the biosphere, consideration of the environment-forming functions of matter, and hence global problems, integrative properties of ecosystems, such as the presence of nutrients and their chemical transformation; self-healing of ecosystems, anthropogenic changes in ecosystems; implementation of patterns of interaction of organs with the environment in practical human activity, in environmental protection; laws of conservation of matter and energy, the unity of the material world; contradictions in the interaction of society and nature, the development of society at the expense of natural resources.
Ecology and chemistry complement each other. The introduction of the principles of thermodynamics into ecology gave rise to production-energy ecology, which studies the patterns of dissipation of energy flow in food chains. A look at the diversity of environmental relationships through the prism of inorganic chemistry reveals a wide range of phenomena caused by human impact on the biosphere and inanimate nature. An important component of tributary processes on the planet are the global circular and transformations undergoing such basic elements as carbon, nitrogen, hydrogen, sulfur and phosphorus…. Many inorganic compounds can and already affect
on the climate of the planet and the state of its atmosphere, on the quality of the natural environment in which people live, and, consequently, on people’s health
Within the framework of inorganic chemistry, it is of interest to pay attention not only to anthropogenic deformations of natural cycles of chemical substances and the use of environmental quality, but also to the search for solutions to socio-ecological problems: energy, raw materials, etc. For example, the prospects of hydrogen energy; the role of oxygen and ozone in ensuring life on Earth; metals in the biosphere and the human body, etc.
Processes related to the field of organic chemistry play a huge role in environmental relations. Organic compounds form the basis of that part of the biosphere, which was called “Living Matter”. The life of people as biological individuals is determined by complex transformations of organic substances in the human body and metabolism with the environment. Finally, the very survival of humanity today is impossible without the widespread use of organic things in everyday life, in medicine, industry, agriculture, etc.
Understanding the role of organic substances in the existence and development of the complex sociobiosphere complex of the Earth as a whole and its main parts is an important aspect of the chemical reading of modern economics.
Ecological achievements serve as the foundation for solving a number of pressing problems of our time. In particular, with data obtained by ecology
The logic of a healthy lifestyle: prioritizing spiritual needs over material ones, caring about maintaining one’s physical health. Such a person in the future will be able to be guided in his professional activities by the principles of environmental and moral imperatives (15, p. 3).
Let us turn to the problem of organizing the teaching of chemistry in high school. On the path of transforming subject teaching and creating a system of environmental education for schoolchildren, the teacher encounters certain difficulties. Firstly, chemophobia has arisen in society, causing children to initially disdain the subject. Secondly, the abstractness of the subject itself.
The main thing is to change (green) your own worldview, to realize your responsibility (human and professional) for preparing an environmentally educated younger generation. It is necessary to systematically inform about the achievements of chemistry in protecting the environment.
1.3. Review of literary sources on environmental education.
The chemistry course taught in modern high school does not fully solve the problems of environmental education and upbringing. Environmental issues are stated declaratively, are not studied in depth and are only outlined. However, activities to study the influence of chemical processes and chemical compounds on the environment cannot fully replace the systematic study of these issues.
Chemistry is one of the most important subjects, on the basis of which dialectics is formed - materialistic ideas about the world around us.
According to the current program, graduates of grade IX have a very incomplete, fragmentary understanding of chemistry, since issues of organic and general chemistry are studied in grades X-XI. Taking into account the differentiation of education in high school, many students may not study chemistry at all, which will lead to complete ignorance of a number of vital issues and complicate human existence in the modern world, since school graduates will not understand, for example, the causes of the harmful effects of human economic activity on flora and fauna and the biosphere as a whole and other similar issues.
Thus, it is necessary to radically change the chemistry program, and, accordingly, the chemistry course as a whole.
At the Department of Methods of Teaching Science and Mathematics Subjects at MGIUU, a new chemistry course program “Ecology and Dialectics” was developed and, on its basis, an experiment was conducted in twenty schools in Moscow and the Moscow region. Its distinctive feature is that on its basis, graduates of class IX receive a general understanding of chemical science as a whole, as well as of all its sections. At the basic level, ending with ninth grade, students become familiar with the role and place of chemistry in modern human economic activity, its impact on the environment and ways to overcome the negative impact of practical human activities on flora, fauna and the human body associated with the use of chemical production.
In this program, much attention is paid to setting up chemical experiments, the use of various most important chemical compounds in human practice, their impact on the environment and the human body. Through knowledge of chemical compounds and chemical phenomena, students develop a special attitude towards the human environment,
A basis is being created for a correct understanding of environmental problems, without which it is impossible for humanity to exist in the modern world; an idea is formed about the complexity of the inconsistency of various processes, including chemical ones, which allows, on this basis, drawing on knowledge from other courses in the natural and mathematical cycle, to form a dialectical-materialistic understanding of the surrounding activity. At the same time, this chemistry course should also solve the problems of educating professionals - chemists, as well as people who need deep knowledge of chemistry to successfully implement their professional tasks. It is designed to create a foundation of solid chemical knowledge, on the basis of which a higher level of knowledge and understanding of chemistry can be formed in grades X - XI of secondary school. This course assumes the implementation of differentiated instruction, taking into account the peculiarities of mastering chemical knowledge both by students with a reduced level of education in educational material, and by students whose initial level of understanding of chemistry is quite high.
The developed program “Ecology and Dialectics” assumes a deep relationship with biology, physics, geography and other disciplines studied at school, which will allow students to form a holistic understanding of the world around them.
However, this program is designed for in-depth study of the subject with a propaedeutic course in the 7th grade and is suitable only in specialized schools or classes. Specialists from Moscow State Pedagogical University named after. N Zvereva and a number of integrated courses were developed: “Biosphere and Man”, “Ecology and Civilization”, an ecologized chemistry course; "from topic to topic.
The program of the integrated course “Biosphere and Man” is intended for students in high school and secondary specialized institutions of the humanities. This approach is all the more relevant because in humanities education there has recently been an increasing tendency to reduce courses in natural sciences, and primarily chemistry. Integration of natural science knowledge allows us to solve the problem of forming a holistic perception of the world around us, developing interest in chemical science and developing chemical knowledge at a good level.
The purpose of this course is to green the consciousness of students and popularize teaching. Leading ideas of the course: man is the cause of environmental problems, and only man can solve them; integrity and diversity of the world. Attention is focused on the study of nature itself, the diversity of levels of organization of life, the evolution of both the organic world and the relationship between man and nature.
But the course “Biosphere and Man” is very specific and is declared as a separate specialized subject in grades X-XI. However, not every school has additional hours in its curriculum to introduce this course.
proposed an ecologized course “Ecology and Civilization”, which has a clearly interdisciplinary character, including philosophical-historical, social-moral, biological, geographical and physical-chemical aspects of environmental problems.
As part of environmental education and upbringing, propaedeutics is carried out in grades I-VII in the form of studying the course “The World Around You” (I-II Classes), “Natural Science” (I-IV Classes), students further accumulate knowledge about natural objects, some patterns development of nature, facts of anthropogenic impact on the environment; teaching schoolchildren
kov analysis and modeling of simple situations. At this stage, the most effective way is to green academic disciplines in combination with problematic elective courses, club work and local history work.
In the process of teaching chemistry in grades VIII and IX, it is important to include consideration of problems of protecting the environment from chemical pollution. The ecologized chemistry course is based on ideas about the relationship between the composition, structure, properties and biological function of substances; their dual role in living nature; biological interchangeability of chemical elements and the consequences of this process for organisms; reasons for disruption of biogeochemical cycles; the role of chemistry in solving environmental problems.
At the final stage of training (X_XI grade), the improvement of chemical knowledge continues in the process of mastering the course of organic and general chemistry. Its content allows us to develop ideas about the manifestation of chemical laws in natural processes; understand such ecological patterns as cyclicity and continuity of exchange of matter between the constituent components of the biosphere.
Ecological chemistry course X grade. is complemented by an elective course “Chemistry and Environmental Protection”, which covers the chemical aspects of environmental problems at the local, regional and global levels. An integral part of this course is a laboratory workshop, which involves organizing student research activities to study the anthropogenic impact on natural objects.
The academic discipline “Ecology and Civilization” was introduced in parallel with the study of chemistry in grades X and XI (14, p. 43).
Due to the integration of these courses, the programs are implemented within several subjects and by several teachers.
For grades VIII – XI, a program of an eco-friendly chemistry course was proposed: from topic to topic. Its main focus is on those phenomena -
Lenyas that cause serious concern for the state of the natural environment and the future of civilization: global warming, depletion of the atmospheric ozone layer, acid rain, accumulation of toxic heavy metals and pesticides in the soil, contamination of large areas with radionuclides, depletion of the planet’s natural resources.
Nature in its natural development is in dynamic equilibrium;
The immediate result of the interaction between man and nature is changes in the chemical composition of the components of the environment, leading to a shift in the natural balance;
Chemical knowledge is an integral part of knowledge about the basics of nature conservation, rational use of natural resources and reasonable transformation of the environment by man.
The role of chemistry in solving environmental problems at the present stage is significant:
A) Studying the composition, structure, properties, how this or that substance behaves in the atmosphere, soil, aquatic environment, what effects it and the products of its transformations have on biological topics;
B) By revealing the mechanisms of biogeochemical processes in the natural cycle of elements, chemistry contributes to solving the problem of the most natural and “painless” entry of industrial production into natural cycles, making it part of any ecosystem.
C) Using various methods of chemical-analytical monitoring of the state of environmental objects or the quality of finished products in a number of industries (chemical, petrochemical
, microbiological, pharmaceutical), chemistry allows you to obtain the information necessary for subsequent decision-making on preventing the entry of harmful
New substances into controlled objects, cleaning of these objects, methods of protecting them, etc.
An ecologized chemistry course makes it possible to reveal the special role of this science in the fight against environmental ignorance, manifested in the ingrained idea of the “guilt” of chemistry in the current environmental situation, to attract schoolchildren to research work to study the state of the natural environment, and to instill in them a sense of personal responsibility for its preservation .
The value of this program lies in the fact that environmental concepts resonate in every topic in chemistry, expanding, deepening and systematizing students’ knowledge of basic chemical laws and their relationship with the state of the environment. When considering any chemical issue, environmental aspects can be presented either in the form of a short message, a report in class, defending an essay, setting up an environmental experiment or solving an environmental problem that helps to master the laws of chemistry using specific environmental examples.
A (MPGU named after V.I. Lenin), (LGUU), Mu (MNPO "Sintez"), (MSU named after..) have developed programs of elective courses on environmental education for schoolchildren: “Healthy human lifestyle in a polluted biosphere”, “Fundamentals of general ecology and environmental protection”, “Ecological problems of the Leningrad region”, “Biological role of chemical elements”. These elective courses ensure the formation of students' knowledge system (level of environmental awareness) with elements of environmental culture (students' value orientation towards scientifically based environmental management). For a more complete study of the fundamentals of ecology in connection with the fundamentals of chemistry, general educational cycles containing general environmental
Completing these tasks increases the level of learning motivation and facilitates the process of acquiring knowledge.
When differentiating by interests, technology comes into contact with culturally educational technology of teaching, which contributes to the humanization of education. As a part of this technology, there is a department of environmental culture: familiarization with the problems of preserving nature, the human environment, unique human culture: nurturing a love of nature, in-depth study of geography, biology and chemistry. As specific, often methodological and local technologies, the technology of environmental education can be used, T. V. Kucher et al.
In order to green the teaching of chemistry, they also use collaboration technologies and group technologies that have a stimulating effect on the development of the child. They involve communication, interaction, exchange of information among students, and mutual understanding.
The learning process is also based on alternative technologies and technologies of developmental education, based on the principles of anthroposophy, according to which the development of the ability to learn leads a person to perfection. Anthroposophy underlies the Waldorf pedagogy of R. Steiner. The development of intellectual abilities is carried out using technology and. Developmental education takes into account and uses the pattern of development, adapts to the level and characteristics of the child (3, p. 80-83: p109: p. 119-122: p. 1516 p. 181)
The use of these technologies makes it possible to orient the student’s personality towards the perception of everything around him as an interested researcher who feels personal responsibility for the consequences of his activities for other people and for nature.
I use fragments of the above-mentioned technologies by N. P. Guzik, I. N. Zakatova, NT Suraveshnaya, TV Kucher, R. Steiner, DB Elkonin and V.V. Davydov when conducting environmental lessons and extracurricular activities on environmental topics.
2.2. Forms of conducting environmental education classes when teaching chemistry.
From a professional point of view, I am attracted to non-standard forms of conducting classes and taking into account students’ knowledge, such as test lessons, seminar lessons, conference lessons, the use of didactic, role-playing and business games, and elements of tetradition. I use the mutually enriching interaction of natural science disciplines to form a holistic attitude towards nature and motivate healthy lifestyle standards.
In order to strengthen the environmental orientation of school education, I introduce consideration of environmental issues into the educational material of each topic, I give the floor to student ecologists on duty to highlight the most important environmental problems within the framework of this topic, which allows the most complete use of environmental knowledge to form a caring attitude of students towards nature, their readiness to take active measures to protect it.
My pedagogical concept for greening the teaching of chemistry is close to an ecologized chemistry course: from topic to topic. In my lessons I use environmental experiments, tasks or questions, and practical work with an environmental focus.
When studying the structure and properties of transition metals, I conduct a seminar lesson “Structural features of d-elements and their impact on the environment and human health.” The method of this lesson is a developmental and educational type seminar.
The objectives of the lesson are to generalize students' knowledge about the periodic law, the structure of atoms, the state of electrons in atoms; strengthening the skills of drawing up electronic circuits, formulas, comparing chemical elements by chemical
mic activity; familiarizing students with certain patterns that determine the prevalence of metals in nature, their toxicity, and the share of participation in the metabolism of living organisms, based on the position of elements - metals in the periodic table; disclosure of the causes of environmental pollution by d-elements, indication of the main sources of pollution; developing the ability of schoolchildren to predict and analyze the consequences of metal pollution in the natural environment; familiarization with the main directions of pollution prevention.
I chose the words as the motto of the lesson: “Science is beneficial only when we accept it not only with our minds, but also with our hearts.”
Seminar plan
1) Position of d-elements in the periodic table.
2) Features of the structure of atoms of d-elements, their properties.
3) d - elements and living organism.
4) Biological role and toxic effect of d - elements.
5) The problem of environmental pollution with metals and ways to solve it.
6) Finding d - elements in nature. Minerals containing d-elements in the Voronezh region.
At the beginning of the lesson, I update the knowledge and conduct an individual and frontal survey.
a) Individual survey.
1. Work using cards.
2. What elements are called d-elements?
3. Characterize the position of d - elements in the periodic table.
4. Features of the structure of atoms of d-elements; filling energy sublevels with electrons, the phenomenon of “electron failure”.
b) Frontal survey.
1. Give a modern formulation of the periodic law.
2. What is the physical meaning of the element’s serial number, group number and period?
3. What quantum numbers describe the state of electrons in an atom?
4. What rules underlie the drawing up of a graphical diagram of the structure of an atom?
5. Draw up graphic diagrams and write electronic formulas for the structure of atoms of the following chemical elements: scandium, iron, niobium, (“failure” of an electron) (check through a horoscope)
At the second stage, I ask students to complete a text task using three options. They will write out their answers on filtered paper soaked in phenolphthalein, dripping an alkali solution into the desired position, in their opinion. If the answer is correct, a color signal appears on the paper.
This allows students' work to be assessed immediately.
The peculiarity of the structure of atoms of d-elements is due to the presence in them of an excess of valence orbitals and a deficiency
Today there is no need to convince anyone of the enormous importance issues related to environmental protection play for all of humanity. This problem is complex and multifaceted. It includes not only purely scientific aspects, but also economic, social, political, legal, and aesthetic.
The processes that determine the current state of the biosphere are based on chemical transformations of substances. The chemical aspects of the problem of environmental protection form a new section of modern chemistry, called chemical ecology. This direction examines the chemical processes occurring in the biosphere, chemical pollution of the environment and its impact on the ecological balance, characterizes the main chemical pollutants and methods for determining the level of pollution, develops physical and chemical methods for combating environmental pollution, and searches for new environmentally friendly sources of energy. and etc.
Understanding the essence of the problem of environmental protection, of course, requires familiarity with a number of preliminary concepts, definitions, judgments, a detailed study of which should contribute not only to a deeper understanding of the essence of the problem, but also to the development of environmental education. The geological spheres of the planet, as well as the structure of the biosphere and the chemical processes occurring in it are summarized in diagram 1.
Usually several geospheres are distinguished. The lithosphere is the outer hard shell of the Earth, consisting of two layers: the upper, formed by sedimentary rocks, including granite, and the lower, basalt. The hydrosphere is all the oceans and seas (the World Ocean), making up 71% of the Earth's surface, as well as lakes and rivers. The average depth of the ocean is 4 km, and in some depressions it is up to 11 km. The atmosphere is a layer above the surface of the lithosphere and hydrosphere, reaching 100 km. The lower layer of the atmosphere (15 km) is called the troposphere. It includes water vapor suspended in the air, moving when the planet's surface is unevenly heated. The stratosphere extends above the troposphere, at the boundaries of which the northern lights appear. In the stratosphere at an altitude of 45 km there is an ozone layer that reflects life-destructive cosmic radiation and partially ultraviolet rays. Above the stratosphere extends the ionosphere - a layer of rarefied gas made of ionized atoms.
Among all the spheres of the Earth, the biosphere occupies a special place. The biosphere is the geological shell of the Earth together with the living organisms that inhabit it: microorganisms, plants, animals. It includes the upper part of the lithosphere, the entire hydrosphere, the troposphere and the lower part of the stratosphere (including the ozone layer). The boundaries of the biosphere are determined by the upper limit of life, limited by the intense concentration of ultraviolet rays, and the lower limit, limited by the high temperatures of the earth's interior; Only lower organisms - bacteria - reach the extreme limits of the biosphere. Occupies a special place in the biosphere ozone protective layer. The atmosphere contains only vol. % ozone, but it created conditions on Earth that allowed life to arise and continue to develop on our planet.
Continuous cycles of matter and energy take place in the biosphere. Basically the same elements are constantly involved in the cycle of substances: hydrogen, carbon, nitrogen, oxygen, sulfur. From inanimate nature they pass into the composition of plants, from plants - into animals and humans. Atoms of these elements are retained in the circle of life for hundreds of millions of years, which is confirmed by isotope analysis. These five elements are called biophilic (life-loving), and not all of their isotopes, but only light ones. Thus, of the three isotopes of hydrogen, only . Of the three naturally occurring isotopes of oxygen 
biophilic only, and from carbon isotopes - only.
The role of carbon in the emergence of life on Earth is truly enormous. There is reason to believe that during the formation of the earth's crust, part of the carbon entered its deep layers in the form of minerals such as carbides, and the other part was retained by the atmosphere in the form of CO. The decrease in temperature at certain stages of the formation of the planet was accompanied by the interaction of CO with water vapor through the kcal reaction, so that by the time liquid water appeared on Earth, atmospheric carbon must have been in the form of carbon dioxide. According to the carbon cycle diagram below, atmospheric carbon dioxide is extracted by plants (1), and through food connections (2) carbon enters the body of animals:
The respiration of animals and plants and the decay of their remains constantly return enormous masses of carbon to the atmosphere and ocean waters in the form of carbon dioxide (3, 4). At the same time, there is some removal of carbon from the cycle due to partial mineralization of the remains of plants (5) and animals (6).
An additional, and more powerful, removal of carbon from the cycle is the inorganic process of weathering of rocks (7), in which the metals they contain under the influence of the atmosphere are transformed into carbon dioxide salts, which are then washed out by water and carried by rivers to the ocean, followed by partial sedimentation. According to rough estimates, up to 2 billion tons of carbon are bound annually when rocks are weathered from the atmosphere. Such an enormous consumption cannot be compensated by various freely occurring natural processes (volcanic eruptions, gas sources, the effect of thunderstorms on limestone, etc.), leading to the reverse transition of carbon from minerals to the atmosphere (8). Thus, both the inorganic and organic stages of the carbon cycle are aimed at reducing the content in the atmosphere. In this regard, it should be noted that conscious human activity significantly influences the overall carbon cycle and, affecting essentially all directions of processes occurring during the natural cycle, ultimately compensates for leakage from the atmosphere. Suffice it to say that due to the combustion of coal alone, more than 1 billion tons of carbon were returned to the atmosphere annually (in the middle of our century). Taking into account the consumption of other types of fossil fuels (peat, oil, etc.), as well as a number of industrial processes leading to the release of , we can assume that this figure is actually even higher.
Thus, the human influence on carbon transformation cycles is directly opposite in direction to the total result of the natural cycle:
The Earth's energy balance is made up of various sources, but the most important of them are solar and radioactive energy. During the evolution of the Earth, radioactive decay was intense, and 3 billion years ago there was 20 times more radioactive heat than now. Currently, the heat of the sun's rays falling on the Earth significantly exceeds the internal heat from radioactive decay, so that the main source of heat can now be considered the energy of the Sun. The sun gives us kcal of heat per year. According to the above diagram, 40% of solar energy is reflected by the Earth into space, 60% is absorbed by the atmosphere and soil. Part of this energy is spent on photosynthesis, part goes to the oxidation of organic substances, and part is conserved in coal, oil, and peat. Solar energy excites climatic, geological and biological processes on Earth on a grandiose scale. Under the influence of the biosphere, solar energy is converted into various forms of energy, causing enormous transformations, migrations, and the circulation of substances. Despite its grandeur, the biosphere is an open system, as it constantly receives a flow of solar energy.
Photosynthesis includes a complex set of reactions of different nature. In this process, the bonds in the molecules and are rearranged, so that instead of the previous carbon-oxygen and hydrogen-oxygen bonds, a new type of chemical bonds arises: carbon-hydrogen and carbon-carbon:
As a result of these transformations, a carbohydrate molecule appears, which is a concentrate of energy in the cell. Thus, in chemical terms, the essence of photosynthesis lies in the rearrangement of chemical bonds. From this point of view, photosynthesis can be called the process of synthesis of organic compounds using light energy. The overall equation of photosynthesis shows that in addition to carbohydrates, oxygen is also produced:
but this equation does not give an idea of its mechanism. Photosynthesis is a complex, multi-stage process in which, from a biochemical point of view, the central role belongs to chlorophyll, a green organic substance that absorbs a quantum of solar energy. The mechanism of photosynthesis processes can be represented by the following diagram:
As can be seen from the diagram, in the light phase of photosynthesis, the excess energy of “excited” electrons gives rise to the process: photolysis - with the formation of molecular oxygen and atomic hydrogen:
and the synthesis of adenosine triphosphoric acid (ATP) from adenosine diphosphoric acid (ADP) and phosphoric acid (P). In the dark phase, the synthesis of carbohydrates occurs, for the implementation of which the energy of ATP and hydrogen atoms, which arise in the light phase as a result of the conversion of light energy from the Sun, is consumed. The overall productivity of photosynthesis is enormous: every year the Earth's vegetation sequesters 170 billion tons of carbon. In addition, plants involve billions of tons of phosphorus, sulfur and other elements in the synthesis, as a result of which about 400 billion tons of organic substances are synthesized annually. Nevertheless, for all its grandeur, natural photosynthesis is a slow and ineffective process, since a green leaf uses only 1% of the solar energy falling on it for photosynthesis.
As noted above, as a result of the absorption of carbon dioxide and its further transformation during photosynthesis, a carbohydrate molecule is formed, which serves as a carbon skeleton for the construction of all organic compounds in the cell. Organic substances produced during photosynthesis are characterized by a high supply of internal energy. But the energy accumulated in the final products of photosynthesis is not available for direct use in chemical reactions occurring in living organisms. The conversion of this potential energy into active form is carried out in another biochemical process - respiration. The main chemical reaction of the respiration process is the absorption of oxygen and the release of carbon dioxide:
However, the breathing process is very complex. It involves the activation of hydrogen atoms of the organic substrate, the release and mobilization of energy in the form of ATP and the generation of carbon skeletons. During the process of respiration, carbohydrates, fats and proteins, in reactions of biological oxidation and gradual restructuring of the organic skeleton, give up their hydrogen atoms to form reduced forms. The latter, when oxidized in the respiratory chain, release energy, which is accumulated in active form in the coupled reactions of ATP synthesis. Thus, photosynthesis and respiration are different, but very closely related aspects of the general energy exchange. In the cells of green plants, the processes of photosynthesis and respiration are closely linked. The process of respiration in them, as in all other living cells, is constant. During the day, along with respiration, photosynthesis occurs in them: plant cells convert light energy into chemical energy, synthesizing organic matter, and releasing oxygen as a byproduct of the reaction. The amount of oxygen released by a plant cell during photosynthesis is 20-30 times greater than its absorption during the simultaneous process of respiration. Thus, during the day, when both processes occur in plants, the air is enriched with oxygen, and at night, when photosynthesis stops, only the respiration process is preserved.
The oxygen necessary for breathing enters the human body through the lungs, whose thin and moist walls have a large surface area (about 90) and are penetrated by blood vessels. Getting into them, oxygen forms with hemoglobin contained in red blood cells - erythrocytes - a fragile chemical compound - oxyhemoglobin and in this form is carried by red arterial blood to all tissues of the body. In them, oxygen is split off from hemoglobin and is included in various metabolic processes, in particular, it oxidizes organic substances that enter the body in the form of food. In tissues, carbon dioxide joins hemoglobin, forming a fragile compound - carbhemoglobin. In this form, and also partially in the form of salts of carbonic acid and in physically dissolved form, carbon dioxide enters the lungs with the flow of dark venous blood, where it is excreted from the body. Schematically, this process of gas exchange in the human body can be represented by the following reactions:
Typically, the air inhaled by a person contains 21% (by volume) and 0.03%, and the air exhaled contains 16% and 4%; per day a person exhales 0.5. Similarly to oxygen, carbon monoxide (CO) reacts with hemoglobin, and the resulting compound is Heme. CO is much more durable. Therefore, even at low concentrations of CO in the air, a significant part of the hemoglobin becomes bound to it and ceases to participate in the transfer of oxygen. When the air contains 0.1% CO (by volume), i.e. at a ratio of CO and 1:200, equal amounts of both gases are bound by hemoglobin. Because of this, when inhaling air poisoned by carbon monoxide, death from suffocation can occur, despite the presence of excess oxygen.
Fermentation, as the process of decomposition of sugary substances in the presence of a special kind of microorganisms, occurs so often in nature that alcohol, although in insignificant quantities, is a constant component of soil water, and its vapors are always contained in small quantities in the air. The simplest fermentation scheme can be represented by the equation:
Although the mechanism of fermentation processes is complex, it can still be argued that phosphoric acid derivatives (ATP), as well as a number of enzymes, play an extremely important role in it.
Rotting is a complex biochemical process, as a result of which excrement, corpses, and plant remains return to the soil the bound nitrogen previously taken from it. Under the influence of special bacteria, this bound nitrogen ultimately turns into ammonia and ammonium salts. In addition, during decay, part of the bound nitrogen turns into free nitrogen and is lost.
As follows from the above diagram, part of the solar energy absorbed by our planet is “conserved” in the form of peat, oil, and coal. Powerful shifts of the earth's crust buried huge plant masses under layers of rocks. When dead plant organisms decompose without access to air, volatile decomposition products are released, and the residue is gradually enriched in carbon. This has a corresponding effect on the chemical composition and calorific value of the decomposition product, which, depending on its characteristics, is called peat, brown and coal (anthracite). Like plant life, animal life of past eras also left us a valuable legacy - oil. Modern oceans and seas contain huge accumulations of simple organisms in the upper layers of water to a depth of about 200 m (plankton) and in the bottom region of not very deep places (benthos). The total mass of plankton and benthos is estimated at a huge figure (~ t). As the basis of nutrition for all more complex marine organisms, plankton and benthos are currently unlikely to accumulate as remains. However, in distant geological epochs, when the conditions for their development were more favorable, and there were much fewer consumers than now, the remains of plankton and benthos, as well as, possibly, more highly organized animals, which died in masses for one reason or another, could become the main building material for oil formation. Crude oil is a water-insoluble, black or brown oily liquid. It consists of 83-87% carbon, 10-14% hydrogen and small amounts of nitrogen, oxygen and sulfur. Its calorific value is higher than that of anthracite and is estimated at 11,000 kcal/kg.
Biomass is understood as the totality of all living organisms in the biosphere, i.e. the amount of organic matter and the energy contained in it of the entire population of individuals. Biomass is usually expressed in weight units in terms of dry matter per unit area or volume. The accumulation of biomass is determined by the vital activity of green plants. In biogeocenoses, they, as producers of living matter, play the role of “producers,” herbivorous and carnivorous animals, as consumers of living organic matter, play the role of “consumers,” and destroyers of organic residues (microorganisms), bringing the breakdown of organic matter to simple mineral compounds, are “decomposers.” A special energy characteristic of biomass is its ability to reproduce. According to the definition of V.I. Vernadsky, “living matter (a collection of organisms), like a mass of gas, spreads over the earth’s surface and exerts a certain pressure in the environment, bypasses obstacles that impede its progress, or takes possession of them, covering them. This movement is achieved through the reproduction of organisms.” On the land surface, biomass increases in the direction from the poles to the equator. In the same direction, the number of species participating in biogeocenoses is increasing (see below). Soil biocenoses cover the entire land surface.
Soil is a loose surface layer of the earth's crust, modified by the atmosphere and organisms and constantly replenished with organic residues. Soil thickness, along with surface biomass and under its influence, increases from the poles to the equator. The soil is densely populated by living organisms, and continuous gas exchange occurs in it. At night, as the gases cool and compress, some air enters it. Oxygen from the air is absorbed by animals and plants and is part of chemical compounds. Nitrogen introduced into the air is captured by some bacteria. During the day, when the soil heats up, ammonia, hydrogen sulfide and carbon dioxide are released from it. All processes occurring in the soil are included in the cycle of substances in the biosphere.
Hydrosphere of the Earth, or the World Ocean, occupies more than 2/3 of the planet's surface. The physical properties and chemical composition of ocean waters are very constant and create an environment favorable for life. Aquatic animals excrete it through respiration, and algae enrich the water through photosynthesis. Photosynthesis of algae occurs mainly in the upper layer of water - at a depth of up to 100 m. Ocean plankton accounts for 1/3 of the photosynthesis occurring on the entire planet. In the ocean, biomass is mostly dispersed. On average, the biomass on Earth, according to modern data, is approximately t, the mass of green land plants is 97%, animals and microorganisms are 3%. There is 1000 times less living biomass in the World Ocean than on land. The use of solar energy on the ocean area is 0.04%, on land - 0.1%. The ocean is not as rich in life as it was thought recently.
Humanity makes up only a small part of the biomass of the biosphere. However, having mastered various forms of energy - mechanical, electrical, atomic - it began to have a tremendous influence on the processes occurring in the biosphere. Human activity has become such a powerful force that this force has become comparable to the natural forces of nature. An analysis of the results of human activity and the impact of this activity on the biosphere as a whole led Academician V.I. Vernadsky to the conclusion that at present humanity has created a new shell of the Earth - “intelligent”. Vernadsky called it "noosphere". The noosphere is “the collective mind of man, concentrated both in its potential capabilities and in the kinetic influences on the biosphere. These influences, however, over the centuries were spontaneous and sometimes predatory in nature, and the consequence of such influence was threatening environmental pollution, with all the ensuing consequences."
Consideration of issues related to the problem of environmental protection requires clarification of the concept " environment"This term means our entire planet plus a thin shell of life - the biosphere, plus outer space that surrounds us and affects us. However, for simplicity, the environment often means only the biosphere and part of our planet - the earth's crust. According to V.I. Vernadsky, the biosphere is “the region of existence of living matter.” Living matter is the totality of all living organisms, including humans.
Ecology as a science about the relationships of organisms with each other, as well as between organisms and their environment, pays special attention to the study of those complex systems (ecosystems) that arise in nature on the basis of the interaction of organisms with each other and the inorganic environment. Hence, an ecosystem is a collection of living and nonliving components of nature that interact. This concept applies to units of varying extent - from an anthill (microecosystem) to the ocean (macroecosystem). The biosphere itself is a giant ecosystem of the globe.
Connections between ecosystem components arise primarily on the basis of food connections and methods of obtaining energy. According to the method of obtaining and using nutritional materials and energy, all organisms of the biosphere are divided into two sharply different groups: autotrophs and heterotrophs. Autotrophs are capable of synthesizing organic substances from inorganic compounds (, etc.). From these energy-poor compounds, cells synthesize glucose, amino acids, and then more complex organic compounds - carbohydrates, proteins, etc. The main autotrophs on Earth are the cells of green plants, as well as some microorganisms. Heterotrophs are not able to synthesize organic substances from inorganic compounds. They need the delivery of ready-made organic compounds. Heterotrophs are the cells of animals, humans, most microorganisms and some plants (for example, fungi and green plants that do not contain chlorophyll). In the process of feeding, heterotrophs ultimately decompose organic matter into carbon dioxide, water and mineral salts, i.e. substances suitable for reuse by autotrophs.
Thus, a continuous cycle of substances occurs in nature: chemical substances necessary for life are extracted by autotrophs from the environment and returned to it again through a series of heterotrophs. To carry out this process, a constant flow of energy from outside is required. Its source is the radiant energy of the Sun. The movement of matter caused by the activity of organisms occurs cyclically, and it can be used again and again, while the energy in these processes is represented by a unidirectional flow. The energy of the Sun is only transformed by organisms into other forms - chemical, mechanical, thermal. In accordance with the laws of thermodynamics, such transformations are always accompanied by the dissipation of part of the energy in the form of heat. Although the general scheme of the cycle of substances is relatively simple, in real natural conditions this process takes on very complex forms. Not a single type of heterotrophic organism is capable of immediately breaking down the organic matter of plants into final mineral products (, etc.). Each species uses only part of the energy contained in organic matter, bringing its decomposition to a certain stage. Residues unsuitable for a given species, but still rich in energy, are used by other organisms. Thus, in the process of evolution, chains of interconnected species have formed in the ecosystem, successively extracting materials and energy from the original food substance. All species that form the food chain exist on organic matter generated by green plants.
In total, only 1% of the radiant energy of the Sun falling on plants is converted into the energy of synthesized organic substances, which can be used by heterotrophic organisms. Most of the energy contained in plant foods is spent in the animal body on various vital processes and, turning into heat, is dissipated. Moreover, only 10-20% of this food energy goes directly to the construction of new substance. Large losses of useful energy predetermine that food chains consist of a small number of links (3-5). In other words, as a result of energy loss, the amount of organic matter produced at each subsequent level of food chains decreases sharply. This important pattern is called rule of the ecological pyramid and on the diagram it is represented by a pyramid, in which each subsequent level corresponds to a plane parallel to the base of the pyramid. There are different categories of ecological pyramids: the pyramid of numbers - reflecting the number of individuals at each level of the food chain, the pyramid of biomass - reflecting the corresponding amount of organic matter, the pyramid of energy - reflecting the amount of energy in food.
Any ecosystem consists of two components. One of them is organic, representing a complex of species that form a self-sustaining system in which the circulation of substances takes place, which is called biocenosis, the other is an inorganic component that gives shelter to the biocenosis and is called bioton:
Ecosystem = bioton + biocenosis.
Other ecosystems, as well as geological, climatic, and cosmic influences in relation to a given ecological system act as external forces. The sustainability of an ecosystem is always related to its development. According to modern views, an ecosystem has a tendency to develop towards its stable state - a mature ecosystem. This change is called succession. The early stages of succession are characterized by low species diversity and low biomass. An ecosystem in the initial stage of development is very sensitive to disturbances, and a strong impact on the main flow of energy can destroy it. In mature ecosystems, flora and fauna increase. In this case, damage to one component cannot have a strong impact on the entire ecosystem. Hence, a mature ecosystem has a high degree of sustainability.
As noted above, geological, climatic, hydrogeological and cosmic influences in relation to a given ecological system act as external forces. Among the external forces influencing ecosystems, human influence occupies a special place. The biological laws of the structure, functioning and development of natural ecosystems are associated only with those organisms that are their necessary components. In this regard, a person, both socially (personality) and biologically (organism), is not part of natural ecosystems. This follows at least from the fact that any natural ecosystem in its emergence and development can do without humans. Man is not a necessary element of this system. In addition, the emergence and existence of organisms is determined only by the general laws of the ecosystem, while man is generated by society and exists in society. Man as an individual and as a biological being is a component of a special system - human society, which has historically changing economic laws for the distribution of food and other conditions of its existence. At the same time, a person receives the elements necessary for life, such as air and water, from the outside, since human society is an open system into which energy and matter come from the outside. Thus, a person is an “external element” and cannot enter into permanent biological connections with elements of natural ecosystems. On the other hand, acting as an external force, humans have a great influence on ecosystems. In this regard, it is necessary to point out the possibility of the existence of two types of ecosystems: natural (natural) and artificial. Development (succession) natural ecosystems obeys the laws of evolution or the laws of cosmic influences (constancy or catastrophes). Artificial ecosystems- these are collections of living organisms and plants living in conditions that man created with his labor and his thought. The power of human influence on nature is manifested precisely in artificial ecosystems, which today cover most of the Earth’s biosphere.
Human ecological intervention has obviously always occurred. All previous human activity can be considered as a process of subordinating many or even all ecological systems, all biocenoses to human needs. Human intervention could not but affect the ecological balance. Even ancient man, by burning forests, upset the ecological balance, but he did it slowly and on a relatively small scale. Such intervention was more local in nature and did not cause global consequences. In other words, human activity of that time took place under conditions close to equilibrium. However, now the human impact on nature, due to the development of science, technology and technology, has taken on such a scale that the disruption of ecological balance has become threatening on a global scale. If the process of human influence on ecosystems were not spontaneous, and sometimes even predatory, then the issue of the environmental crisis would not be so acute. Meanwhile, human activity today has become so commensurate with the powerful forces of nature that nature itself is no longer able to cope with the loads it experiences.
Thus, the main essence of the problem of environmental protection is that humanity, thanks to its labor activity, has become such a powerful nature-forming force that its influence began to manifest itself much faster than the influence of the natural evolution of the biosphere.
Although the term “environmental protection” is very common today, it still does not strictly reflect the essence of the matter. Physiologist I.M. Sechenov once pointed out that a living organism cannot exist without interaction with the environment. From this point of view, the term "environmental management" appears to be more stringent. In general, the problem of rational use of the environment lies in the search for mechanisms that ensure the normal functioning of the biosphere.
CONTROL QUESTIONS
1. Define the concept of “environment”.
2. What is the main essence of the problem of environmental protection?
3. List the various aspects of the environmental problem.
4. Define the term “chemical ecology”.
5. List the main geospheres of our planet.
6. Indicate the factors that determine the upper and lower limits of the biosphere.
7. List the biophilic elements.
8. Comment on the impact of human activities on the natural cycle of carbon transformations.
9. What can you say about the mechanism of photosynthesis?
10. Give a diagram of the breathing process.
11. Give a diagram of fermentation processes.
12. Define the concepts “producer”, “consumer”, “decomposer”.
13. What is the difference between “autotrophs” and “heterotrophs”?
14. Define the concept of “noosphere”.
15. What is the essence of the “ecological pyramid” rule?
16. Define the concepts “biotone” and “biocenosis”.
17. Define the concept “ecosystem”.
Microelements and enzymes. Introduction to metalloenzymes. Specific and nonspecific enzymes. The role of metal ions in enzymes. Horizontal similarity in the biological action of d-elements. Synergism and antagonism of elements.
Propensity of d-element ions to hydrolysis and polymerization
In acidic environments, d-element ions are in the form of hydrated ions [M(H 2 O) m ] n+. With increasing pH, hydrated ions of many d-elements, due to their large charge and small ion size, have a high polarizing effect on water molecules, acceptor ability for hydroxide ions, undergo cationic hydrolysis, and form strong covalent bonds with OH - . The process ends either with the formation of basic salts [M(OH) m ] (m-n)+, or insoluble hydroxides M(OH) n, or hydroxo complexes [M(OH) m ] (n-m)-. The process of hydrolytic interaction can occur with the formation of multinuclear complexes as a result of the polymerization reaction.
2. 4. Biological role of d-elements (transition elements)
Elements, the content of which does not exceed 10 -3%, are part of enzymes, hormones, vitamins and other vital compounds. For protein, carbohydrate and fat metabolism, the following are needed: Fe, Co, Mn, Zn, Mo, V, B, W; the following are involved in protein synthesis: Mg, Mn, Fe, Co, Cu, Ni, Cr; in hematopoiesis – Co, Ti, Cu, Mn, Ni, Zn; in breath - Mg, Fe, Cu, Zn, Mn and Co. Therefore, microelements have found wide application in medicine, as microfertilizers for field crops, and as fertilizers in livestock, poultry and fish farming. Microelements are part of a large number of bioregulators of living systems, which are based on biocomplexes. Enzymes are special proteins that act as catalysts in biological systems. Enzymes are unique catalysts with unsurpassed efficiency and high selectivity. An example of the efficiency of the decomposition reaction of hydrogen peroxide 2H 2 O 2 ® 2H 2 O + O 2 in the presence of enzymes is given in Table 6.
Table 6. Activation energy (E o) and the relative rate of the decomposition reaction of H 2 O 2 in the absence and presence of various catalysts
Currently, more than 2000 enzymes are known, many of which catalyze a single reaction. The activity of a large group of enzymes occurs only in the presence of certain non-protein compounds called cofactors. Metal ions or organic compounds act as cofactors. About a third of enzymes are activated by transition metals.
Metal ions in enzymes perform a number of functions: they are an electrophilic group of the active center of the enzyme and facilitate interaction with negatively charged regions of substrate molecules, form a catalytically active conformation of the enzyme structure (in the formation of the helical structure of RNA, zinc and manganese ions are involved), participate in electron transport (complexes electron transfer). The ability of a metal ion to perform its role in the active site of the corresponding enzyme depends on the ability of the metal ion to form complexes, the geometry and stability of the complex formed. This provides an increase in the selectivity of the enzyme towards substrates, activation of bonds in the enzyme or substrate through coordination and change in the shape of the substrate in accordance with the steric requirements of the active site.
Biocomplexes vary in stability. Some of them are so strong that they are constantly in the body and perform a specific function. In cases where the connection between the cofactor and the enzyme protein is strong and it is difficult to separate them, it is called a “prosthetic group”. Such bonds have been found in enzymes containing a heme complex of iron with a porphin derivative. The role of metals in such complexes is highly specific: replacing it even with an element similar in properties leads to a significant or complete loss of physiological activity. These enzymes include to specific enzymes.
Examples of such compounds are chlorophyll, polyphenyl oxidase, vitamin B 12, hemoglobin and some metalloenzymes (specific enzymes). Few enzymes are involved in only one specific or single reaction.
The catalytic properties of most enzymes are determined by the active center formed by various microelements. Enzymes are synthesized for the duration of the function. The metal ion acts as an activator and can be replaced by another metal ion without loss of physiological activity of the enzyme. These are classified as nonspecific enzymes.
Below are enzymes in which different metal ions perform similar functions.
Table 7. Enzymes in which different metal ions perform similar functions
One trace element can activate different enzymes, and one enzyme can be activated by different trace elements. Enzymes with microelements in the same oxidation state +2 have the greatest similarity in biological action. As can be seen, microelements of transition elements in their biological action are characterized by more horizontal similarity than vertical similarity in the periodic system of D.I. Mendeleev (in the Ti-Zn series). When deciding on the use of a particular microelement, it is necessary to take into account not only the presence of mobile forms of this element, but also others that have the same oxidation state and can replace each other in the composition of enzymes.
Some metalloenzymes occupy an intermediate position between specific and nonspecific enzymes. Metal ions act as a cofactor. Increasing the strength of the enzyme biocomplex increases the specificity of its biological action. The efficiency of the enzymatic action of the enzyme's metal ion is influenced by its oxidation state. According to the intensity of their influence, microelements are arranged in the following row:
Ti 4+ ®Fe 3+ ®Cu 2+ ®Fe 2+ ®Mg 2+ ®Mn 2+ . The Mn 3+ ion, unlike the Mn 2+ ion, is very tightly bound to proteins, and mainly with oxygen-containing groups, together Fe 3+ is part of metalloproteins.
Microelements in complexonate form act in the body as a factor that apparently determines the high sensitivity of cells to microelements through their participation in the creation of a high concentration gradient. The values of atomic and ionic radii, ionization energies, coordination numbers, and the tendency to form bonds with the same elements in bioligand molecules determine the effects observed during mutual substitution of ions: can occur with increasing (synergy) and with inhibition of their biological activity (antagonism) element being replaced. Ions of d-elements in the +2 oxidation state (Mn, Fe, Co, Ni, Zn) have similar physicochemical characteristics of atoms (electronic structure of the outer level, similar ion radii, type of orbital hybridization, similar values of stability constants with bioligands). The similarity of the physicochemical characteristics of the complexing agent determines the similarity of their biological action and interchangeability. The above transition elements stimulate hematopoietic processes and enhance metabolic processes. The synergism of elements in the processes of hematopoiesis is possibly associated with the participation of ions of these elements in various stages of the process of synthesis of formed elements of human blood.
The s - elements of group I are characterized, in comparison with other elements of their period, by a small charge of atomic nuclei, a low ionization potential of valence electrons, a large atomic size and its increase in the group from top to bottom. All this determines the state of their ions in aqueous solutions in the form of hydrated ions. The greatest similarity between lithium and sodium determines their interchangeability and synergistic action. Destructive properties in aqueous solutions of potassium, rubidium and cesium ions ensure their better membrane permeability, interchangeability and synergism of their action. The concentration of K + inside cells is 35 times higher than outside it, and the concentration of Na + in the extracellular fluid is 15 times higher than inside the cell. These ions are antagonists in biological systems. s - Group II elements are found in the body in the form of compounds formed by phosphoric, carbonic and carboxylic acids. Calcium, contained mainly in bone tissue, is similar in properties to strontium and barium, which can replace it in bones. In this case, both cases of synergism and antagonism are observed. Calcium ions are also antagonists of sodium, potassium and magnesium ions. The similarity of the physicochemical characteristics of Be 2+ and Mg 2+ ions determines their interchangeability in compounds containing Mg–N and Mg–O bonds. This may explain the inhibition of magnesium-containing enzymes when beryllium enters the body. Beryllium is an antagonist of magnesium. Consequently, the physicochemical properties and biological effects of microelements are determined by the structure of their atoms. Most biogenic elements are members of the second, third and fourth periods of the periodic system of D.I. Mendeleev. These are relatively light atoms, with a relatively small charge on the nuclei of their atoms.
2. 4. 2. The role of transition element compounds in electron transfer in living systems.
In a living organism, many processes have a cyclical, wave-like character. The chemical processes underlying them must be reversible. The reversibility of processes is determined by the interaction of thermodynamic and kinetic factors. Reversible reactions include those with constants from 10 -3 to 10 3 and with a small value of DG 0 and DE 0 of the process. Under these conditions, the concentrations of the starting substances and reaction products can be in comparable concentrations, and by changing them in a certain range, reversibility of the process can be achieved. From a kinetic point of view, there should be low values of activation energy. Therefore, metal ions (iron, copper, manganese, cobalt, molybdenum, titanium and others) are convenient carriers of electrons in living systems. The addition and donation of an electron causes changes only in the electronic configuration of the metal ion, without significantly changing the structure of the organic component of the complex. A unique role in living systems is assigned to two redox systems: Fe 3+ /Fe 2+ and Cu 2+ /Cu + . Bioligands stabilize to a greater extent the oxidized form in the first pair, and predominantly the reduced form in the second pair. Therefore, in systems containing iron, the formal potential is always lower, and in systems containing copper, it is often higher. Redox systems containing copper and iron cover a wide range of potentials, which allows them to interact with many substrates, accompanied by moderate changes in DG 0 and DE 0, which meets the conditions of reversibility. An important step in metabolism is the abstraction of hydrogen from nutrients. Hydrogen atoms then transform into an ionic state, and the electrons separated from them enter the respiratory chain; in this chain, moving from one compound to another, they give up their energy to the formation of one of the main sources of energy, adenosine triphosphoric acid (ATP), and they themselves ultimately reach an oxygen molecule and join with it, forming water molecules. The bridge along which electrons oscillate are complex compounds of iron with a porphyrin core, similar in composition to hemoglobin.
A large group of iron-containing enzymes that catalyze the process of electron transfer in mitochondria are called cytochromes(ts.kh.), In total, about 50 cytochromes are known. Cytochromes are iron porphyrins in which all six orbitals of the iron ion are occupied by donor atoms, a bioligand. The difference between cytochromes is only in the composition of the side chains of the porphyrin ring. Variations in the structure of the bioligand are caused by differences in the magnitude of the formal potentials. All cells contain at least three proteins of similar structure, called cytochromes a, b, c. In cytochrome c, the connection with the histidine residue of the polypeptide chain occurs through the porphyrin core. The free coordination site in the iron ion is occupied by the methionine residue of the polypeptide chain:
One of the mechanisms of functioning of cytochromes, which make up one of the links in the electron transport chain, is the transfer of an electron from one substrate to another.
From a chemical point of view, cytochromes are compounds that exhibit redox duality under reversible conditions.
Electron transfer by cytochrome c is accompanied by a change in the oxidation state of iron:
c. X. Fe 3+ + e « c.xFe 2+
Oxygen ions react with hydrogen ions in the environment to form water or hydrogen peroxide. Peroxide is quickly decomposed by a special enzyme catalase into water and oxygen according to the following scheme:
2H 2 O 2 ®2H 2 O + O 2
The enzyme peroxidase accelerates the oxidation reactions of organic substances with hydrogen peroxide according to the following scheme:
These enzymes have a heme in their structure, in the center of which there is iron with an oxidation state of +3 (Section 2 7.7).
In the electron transport chain, cytochrome c transfers electrons to cytochromes called cytochrome oxidases. They contain copper ions. Cytochrome is a one-electron carrier. The presence of copper in one of the cytochromes along with iron turns it into a two-electron carrier, which makes it possible to regulate the rate of the process.
Copper is part of an important enzyme - superoxide dismutase (SOD), which utilizes the toxic superoxide ion O2- in the body through the reaction
[SOD Cu 2+ ] + ® O 2 - [SOD Cu + ] + O 2
[SOD Cu + ] + O 2 - + 2H + ® [SODCu 2+ ] + H 2 O 2
Hydrogen peroxide decomposes in the body under the action of catalase.
Currently, about 25 copper-containing enzymes are known. They form a group of oxygenases and hydroxylases. The composition and mechanism of their action are described in work (2, section 7.9.).
Transition element complexes are a source of microelements in a biologically active form with high membrane permeability and enzymatic activity. They are involved in protecting the body from “oxidative stress”. This is due to their participation in the utilization of metabolic products that determine the uncontrolled oxidation process (peroxides, free radicals and other oxygen-active species), as well as in the oxidation of substrates. The mechanism of the free radical reaction of substrate oxidation (RH) with hydrogen peroxide with the participation of an iron complex (FeL) as a catalyst can be represented by reaction schemes.
RH + . OH ® R . + H 2 O; R. + FeL ® R + + FeL
Substrate
R + + OH - ® ROH
Oxidized substrate
Further occurrence of the radical reaction leads to the formation of products with a higher degree of hydroxylation. Other radicals act similarly: HO 2. , O 2 . , . O 2 - .
2. 5. General characteristics of p-block elements
Elements in which the p-sublevel of the outer valence level is completed are called p-elements. Electronic structure of the ns 2 p 1-6 valence level. Valence electrons are the s- and p-sublevels.
Table 8. Position of p-elements in the periodic table of elements.
| Period | Group | |||||
| IIIA | IVA | V.A. | VIA | VIIA | VIIIA | |
| (C) | (N) | (O) | (F) | Ne | ||
| (P) | (S) | (Cl) | Ar | |||
| Ga | Kr | |||||
| In | Sn | Sb | Te | (I) | Xe | |
| Tl | Pb | Bi | Po | At | Rn | |
| p 1 | p 2 | p 3 | p 4 | p 5 | R 6 | |
| () - essential elements, – biogenic elements |
In periods from left to right, the charge of nuclei increases, the influence of which prevails over the increase in the forces of mutual repulsion between electrons. Therefore, the ionization potential, electron affinity, and, consequently, the acceptor capacity and non-metallic properties increase in periods. All elements lying on the Br – At diagonal and above are non-metals and form only covalent compounds and anions. All other p-elements (with the exception of indium, thallium, polonium, bismuth, which exhibit metallic properties) are amphoteric elements and form both cations and anions, both of which are highly hydrolyzed. Most non-metal p-elements are biogenic (the exceptions are the noble gases, tellurium and astatine). Of the p-elements - metals - only aluminum is classified as biogenic. Differences in the properties of neighboring elements, both inside; and by period: they are expressed much more strongly than those of s-elements. p-elements of the second period - nitrogen, oxygen, fluorine have a pronounced ability to participate in the formation of hydrogen bonds. Elements of the third and subsequent periods lose this ability. Their similarity lies only in the structure of the outer electron shells and those valence states that arise due to unpaired electrons in unexcited atoms. Boron, carbon and especially nitrogen are very different from the other elements of their groups (the presence of d- and f-sublevels).
All p-elements and especially p-elements of the second and third periods (C, N, P, O, S, Si, Cl) form numerous compounds with each other and with s-, d- and f-elements. Most of the compounds known on Earth are compounds of p-elements. The five main (macrobiogenic) p-elements of life - O, P, C, N and S - are the main building material from which the molecules of proteins, fats, carbohydrates and nucleic acids are composed. Of the low molecular weight compounds of p-elements, the oxoanions are of greatest importance: CO 3 2-, HCO 3 -, C 2 O 4 2-, CH3COO -, PO 4 3-, HPO 4 2-, H 2 PO 4 -, SO 4 2- and halide ions. p-elements have many valence electrons with different energies. Therefore, compounds exhibit different degrees of oxidation. For example, carbon exhibits various oxidation states from –4 to +4. Nitrogen – from -3 to +5, chlorine – from -1 to +7.
During the reaction, the p-element can donate and accept electrons, acting respectively as a reducing agent or an oxidizing agent, depending on the properties of the element with which it interacts. This gives rise to a wide range of compounds formed by them. The mutual transition of atoms of p-elements of various oxidation states, including due to metabolic redox processes (for example, the oxidation of an alcohol group into their aldehyde group and then into a carboxyl group, and so on) causes a wealth of their chemical transformations.
A carbon compound exhibits oxidizing properties if, as a result of the reaction, carbon atoms increase the number of its bonds with atoms of less electronegative elements (metal, hydrogen) because, by attracting common bond electrons, the carbon atom lowers its oxidation state.
CH 3 ® -CH 2 OH ® -CH = O ® -COOH ® CO 2
The redistribution of electrons between the oxidizing agent and the reducing agent in organic compounds can only be accompanied by a shift in the total electron density of the chemical bond to the atom acting as the oxidizing agent. In the case of strong polarization, this connection may be broken.
Phosphates in living organisms serve as structural components of the skeleton, cell membranes and nucleic acids. Bone tissue is built mainly from hydroxyapatite Ca 5 (PO 4) 3 OH. The basis of cell membranes is phospholipids. Nucleic acids consist of ribose or deoxyribose phosphate chains. In addition, polyphosphates are the main source of energy.
In the human body, NO is necessarily synthesized using the enzyme NO synthase from the amino acid arginine. The lifetime of NO in the cells of the body is on the order of a second, but their normal functioning is not possible without NO. This compound provides: relaxation of smooth muscles of vascular muscles, regulation of heart function, effective functioning of the immune system, transmission of nerve impulses. NO is believed to play an important role in learning and memory.
Redox reactions in which p-elements participate underlie their toxic effect on the body. The toxic effect of nitrogen oxides is associated with their high redox ability. Nitrates that enter food are reduced to nitrites in the body.
NO 3 - + 2H + + 2e ® NO 2 + H 2 O
Nitrites have highly toxic properties. They convert hemoglobin into methemoglobin, which is a product of hydrolysis and oxidation of hemoglobin.
As a result, hemoglobin loses its ability to transport oxygen to the body's cells. Hypoxia develops in the body. In addition, nitrites, as salts of a weak acid, react with hydrochloric acid in the gastric contents, forming nitrous acid, which, with secondary amines, forms carcinogenic nitrosamines:
The biological effect of high-molecular organic compounds (amino acids, polypeptides, proteins, fats, carbohydrates and nucleic acids) is determined by atoms (N, P, S, O) or formed groups of atoms (functional groups), in which they act as chemically active centers, donors electron pairs capable of forming coordination bonds with metal ions and organic molecules. Consequently, p-elements form polydentate chelating compounds (amino acids, polypeptides, proteins, carbohydrates and nucleic acids). They are characterized by complex formation reactions, amphoteric properties, and anionic hydrolysis reactions. These properties determine their participation in basic biochemical processes and in ensuring the state of isohydry. They form protein, phosphate, hydrogen carbonate buffer systems. Participate in the transport of nutrients, metabolic products, and other processes.
3. 1. The role of the habitat. Chemistry of atmospheric pollution. The role of the doctor in protecting the environment and human health.
A.P. Vinogradov showed that the surface of the earth is heterogeneous in chemical composition. Plants and animals, as well as humans, located in different zones, use nutrients of different chemical compositions and respond to this with certain physiological reactions and a certain chemical composition of the body. The effects caused by microelements depend on their intake into the body. The concentrations of biometals in the body during its normal functioning are maintained at a strictly defined level (biotic dose) with the help of appropriate proteins and hormones. The reserves of biometals in the body are systematically replenished. They are contained in sufficient quantities in the food we eat. The chemical composition of plants and animals used for food affects the body.
Intensive industrial production has led to pollution of the natural environment with “harmful” substances, including compounds of transition elements. In nature, there is an intensive redistribution of elements in biogeochemical provinces. The main route (up to 80%) of their entry into the body is our food. Taking into account anthropogenic pollution of the environment, it is necessary to take radical measures to rehabilitate the environment and the people living in it. This problem in many European countries is put ahead of the problems of economic growth and is among the priorities. In recent years, the release of various pollutants has increased. The forecast for industrial development allows us to conclude that the amount of emissions and environmental pollutants will continue to increase.
Real zones in which the cycle of elements occurs as a result of life activity are called ecosystems or, as Academician V.N. called it. Sukachev, biogeocenoses. Humans are an integral part of the ecosystems on our planet. In his life activities, a person can disrupt the course of the natural biogenic cycle. Many industries pollute the environment. According to the teachings of V.I. Vernadsky, the shell of our planet, changed by human economic activity, is called noosphere. It covers the entire biosphere and goes beyond its limits (stratosphere, deep mines, wells, etc.). The main role in the noosphere is played by technogenic migration of elements - technogenesis. Research on the geochemistry of the noosphere is the theoretical basis for the rational use of natural resources and the fight against environmental pollution. Gaseous, liquid, and solid environmental pollution form toxic aerosols (fog, smoke) in the ground layer of the atmosphere. When the atmosphere is polluted with sulfur dioxide, high humidity and no temperature, toxic smog is formed. The main damage to the environment is caused by the oxidation products SO 2, SO 3 and acids H 2 SO 3 and H 2 SO 4. As a result of emissions of sulfur oxide and nitrogen, “acid” rain is observed in industrial regions. Rainwater containing high concentrations of hydrogen ions can leach toxic metal ions:
ZnO(t) + 2H + = Zn 2+ (p) + H 2 O
When an internal combustion engine operates, nitrogen oxides are released, the conversion product of which is ozone:
N 2 + O 2 « 2NO (in the engine cylinder)
Of great concern to society are environmental problems, the chemical essence of which is to protect the biosphere from excess carbon oxides and methane, which create the “greenhouse effect”, sulfur and nitrogen oxides, leading to “acid rain”; halogen derivatives (chlorine, fluorine) of hydrocarbons that violate the “ozone shield of the Earth”; carcinogenic substances (polyaromatic hydrocarbons and products of their incomplete combustion) and other products. Nowadays, not only the problem of environmental protection, but also the protection of the internal environment is becoming relevant. The number of substances entering a living organism that are foreign, alien to life and called xenobiotics. According to the World Health Organization, there are about 4 million of them. They enter the body with food, water and air, as well as in the form of medicines (dosage forms).
This is due to the low culture of producers and consumers of chemicals who do not have professional chemical knowledge. Indeed, only ignorance of the properties of substances and the inability to foresee the consequences of their excessive use can cause irreparable losses of nature, of which man is an integral element. Indeed, to this day, some manufacturers, and even medical workers, are likened to Bulgakov’s miller, who wanted to immediately recover from malaria with an incredible (shock) dose of quinine, but did not have time - he died. The role of various chemical elements in environmental pollution and the occurrence of diseases, including occupational ones, is still insufficiently studied. It is necessary to analyze the entry of various substances into the environment as a result of human activity, the ways they enter the human body, plants, their interaction with living organisms at different levels, and develop a system of effective measures aimed at both preventing further environmental pollution and creating the necessary biological means of protecting the internal environment of the body. Medical workers are required to take part in the development and implementation of technical, preventive, sanitary, hygienic and therapeutic measures.
3.2 Biochemical provinces. Endemic diseases.
Zones within which animals and plants are characterized by a certain chemical elemental composition are called biogeochemical provinces. Biogeochemical provinces are third-order taxa of the biosphere - territories of various sizes within subregions of the biosphere with constant characteristic reactions of organisms (for example, endemic diseases). There are two types of biogeochemical provinces - natural and technogenic, resulting from the development of ore deposits, emissions from the metallurgical and chemical industries, and the use of fertilizers in agriculture. It is necessary to pay attention to the role of microorganisms in creating the geochemical characteristics of the environment. Deficiency and excess of elements can lead to the formation of biogeochemical provinces, caused by both a deficiency of elements (iodine, fluorine, calcium, copper, etc. provinces) and their excess (boron, molybdenum, fluorine, copper, etc.). The problem of bromine deficiency within continental regions, mountainous regions and bromine excess in coastal and volcanic landscapes is interesting and important. In these regions, the evolution of the central nervous system proceeded qualitatively differently. A biogeochemical province on nickel-enriched rocks has been discovered in the Southern Urals. It is characterized by ugly forms of grasses and sheep diseases associated with high nickel content in the environment.
The correlation of biogeochemical provinces with their ecological state made it possible to identify the following territories: a) with a relatively satisfactory ecological situation - (zone of relative well-being); b) with reversible, limited, and in most cases removable environmental violations - (environmental risk zone); c) with a sufficiently high degree of disadvantage observed over a long period over a large territory, the elimination of which requires significant costs and time - (zone of ecological crisis); d) with a very high degree of environmental distress, practically irreversible environmental damage that has a clear localization -( ecological disaster zone).
Based on the impact factor, its level, duration of action and area of distribution, the following natural-technogenic biogeochemical provinces are identified as risk and crisis zones:
1. polymetallic (Pb, Cd, Hjg, Cu, Zn) with dominant associations Cu–Zn, Cu–Ni, Pb–Zn, including:
· enriched with copper (Southern Urals, Bashkortostan, Norilsk, Mednogorsk);
· enriched with nickel (Norilsk, Monchegorsk, Nickel, Polyarny, Tuva, Southern Urals);
· enriched with lead (Altai, Caucasus, Transbaikalia);
· enriched with fluorine (Kirovsk, Krasnoyarsk, Bratsk);
· with a high content of uranium and radionuclides in the environment (Transbaikalia, Altai, Southern Urals).
2. biogeochemical provinces with deficiencies of microelements (Se, I, Cu, Zn, etc.).
Environmental chemistry is the science of chemical processes that determine the state and properties of the environment - the atmosphere, hydrosphere and soils.
A branch of chemistry devoted to the study of the chemical foundations of environmental phenomena and problems, as well as the processes of formation of the chemical properties and composition of environmental objects.
Environmental chemistry studies both the natural chemical processes occurring in the environment and the process of its anthropogenic pollution.
Anthropogenic environmental pollution has a significant impact on the health of plants and animals. The annual production of vegetation on the world's land before its disturbance by humans was close to 172x109 tons of dry matter. As a result of the impact, its natural production has now decreased by at least 25%. In the publications of V.V. Ermakova (1999), Yu.M. Zakharova (2003), I.M. Donnik (1997), M.S. Panin (2003) and others show the increasing aggressiveness of anthropogenic impacts on the environment (EA) taking place in the territories of developed countries.
V.A. Kovda provided data on the relationship between natural biogeochemical cycles and the anthropogenic contribution to natural processes; since then, technogenic flows have increased. According to his data, biogeochemical and technogenic flows of the biosphere are estimated by the following values:
According to the World Health Organization (WHO), out of more than 6 million known chemical compounds, up to 500 thousand are used, of which 40 thousand have properties harmful to humans, and 12 thousand are toxic. By 2009, the consumption of mineral and organic raw materials increased sharply and reached 40-50 thousand tons per inhabitant of the Earth. Accordingly, the volumes of industrial, agricultural and household waste are increasing. In the 21st century, anthropogenic pollution has brought humanity to the brink of an environmental disaster. Therefore, analysis of the ecological state of the Russian biosphere and the search for ways to ecologically rehabilitate its territory are very relevant.
Currently, enterprises in the mining, metallurgical, chemical, woodworking, energy, construction materials and other industries of the Russian Federation annually generate about 7 billion tons of waste. Only 2 billion tons are used, or 28% of the total volume. In this regard, about 80 billion tons of solid waste alone have been accumulated in the country's dumps and sludge storage facilities. About 10 thousand hectares of land suitable for agriculture are annually alienated for landfills for their storage. The largest amount of waste is generated during the extraction and enrichment of raw materials. Thus, in 2005, the volume of overburden, associated rocks and enrichment waste in various industries was 3100 and 1200 million m3, respectively. A large amount of waste is generated in the process of harvesting and processing wood raw materials. At logging sites, waste accounts for up to 46.5% of the total volume of wood removed. In our country, more than 200 million m3 of wood waste is generated annually. Slightly less waste is produced at ferrous metallurgy enterprises: in 2004, the output of fiery liquid slag amounted to 79.7 million tons, including 52.2 million tons of blast furnace, 22.3 million tons of steelmaking and 4.2 million tons. t ferroalloys. In the world, approximately 15 times less non-ferrous metals are smelted annually than ferrous metals.
However, in the production of non-ferrous metals in the process of ore enrichment, from 30 to 100 tons of crushed tailings are formed per 1 ton of concentrates, and when smelting ore per 1 ton of metal - from 1 to 8 tons of slag, sludge and other waste.
Every year, chemical, food, mineral fertilizer and other industries produce more than 22 million tons of gypsum-containing waste and about 120-140 million tons of wastewater sludge (dry), about 90% of which is obtained by neutralizing industrial wastewater. More than 70% of waste heaps in Kuzbass are classified as burning. At a distance of several kilometers from them, the concentrations of SO2, CO, and CO2 in the air are significantly increased. The concentration of heavy metals in soils and surface waters increases sharply, and in areas of uranium mines - radionuclides. Open-pit mining leads to landscape disturbances that are comparable in scale to the consequences of major natural disasters. Thus, in the area of mine workings in Kuzbass, numerous chains of deep (up to 30 m) failures were formed, stretching for more than 50 km, with a total area of up to 300 km2 and failure volumes of more than 50 million m3.
Currently, huge areas are occupied by solid waste from thermal power plants: ash, slag, similar in composition to metallurgical waste. Their annual output reaches 70 million tons. The degree of their use is within 1-2%. According to the Ministry of Natural Resources of the Russian Federation, the total area of land occupied by waste from various industries generally exceeds 2000 km2.
More than 40 billion tons of crude oil are produced annually in the world, of which about 50 million tons of oil and petroleum products are lost during production, transportation and processing. Oil is considered one of the most widespread and most dangerous pollutants in the hydrosphere, since about a third of it is produced on the continental shelf. The total mass of petroleum products entering the seas and oceans annually is approximately estimated at 5-10 million tons.
According to NPO Energostal, the degree of purification of waste gases from ferrous metallurgy dust exceeds 80%, and the degree of utilization of solid recovery products is only 66%.
At the same time, the utilization rate of iron-containing dust and slag is 72%, while for other types of dust it is 46%. Almost all enterprises of both metallurgical and thermal power plants do not resolve the issues of cleaning aggressive low-percentage sulfur-containing gases. Emissions of these gases amounted to 25 million tons. Emissions of sulfur-containing gases into the atmosphere only from the commissioning of gas treatment plants at 53 power units in the country in the period from 2005 to 2010 decreased from 1.6 to 0.9 million tons. The issues of neutralization of galvanic solutions are poorly resolved. Even slower are questions regarding the disposal of waste generated during the neutralization and processing of spent etching solutions, chemical production solutions and wastewater. In Russian cities, up to 90% of wastewater is discharged into rivers and reservoirs in an untreated form. Currently, technologies have been developed that make it possible to convert toxic substances into low-toxic and even biologically active ones, which can be used in agriculture and other industries.
Modern cities emit about 1,000 compounds into the atmosphere and water environment. Motor transport occupies one of the leading places in urban air pollution. In many cities, exhaust fumes account for 30%, and in some - 50%. In Moscow, about 96% of CO, 33% of NO2 and 64% of hydrocarbons enter the atmosphere through motor transport.
Based on the impact factors, their level, duration of action and area of distribution, the natural-technogenic biogeochemical provinces of the Urals are classified as territories with the greatest degree of environmental distress. Over the past years, the Urals has occupied a leading position in the amount of total emissions of harmful substances into the atmosphere. According to A.A. Malygina, the Urals ranks first in Russia for air and water pollution, and second for soil pollution.
The Urals are one of the country's largest producers of ferrous metals. There are 28 metallurgical enterprises in it. To provide them with raw materials, more than 10 mining and processing enterprises operate in the region. As of 2003, metallurgical enterprises in the region accumulated about 180 million tons of blast furnace slag, 40 million tons of steelmaking slag and more than 20 million tons of ferrochrome production slag, as well as a significant amount of dust and sludge. The possibility of recycling waste into various building materials for the needs of the national economy has been established.
Over 2.5 billion m3 of various rocks, 250 million tons of slag and ash from thermal power plants have been accumulated in the region's dumps. Of the total volume of overburden, only 3% is processed. At metallurgical enterprises, out of 14 million tons of annually generated slag, only 40-42% is used, of which 75% is blast furnace slag, 4% is steel smelting, 3% is ferroalloy and 17% is non-ferrous metallurgy slag, and thermal power plant ash is only about 1%.
Disruption of micro- and macroelement homeostasis in the body is determined by natural and man-made pollution of the biosphere, which leads to the formation of wide areas of man-made microelements around territorial-industrial complexes. The health of not only people directly involved in the production process suffers, but also those living in the vicinity of the enterprises. As a rule, they have a less pronounced clinical picture and can take the latent form of certain pathological conditions. It has been shown that near industrial enterprises located in the city among residential areas, lead concentrations exceed background values by 14-50 times, zinc by 30-40 times, chromium by 11-46 times, and nickel by 8-63 times.
An analysis of the ecological and chemical situation and the health status of the population of the Urals made it possible to establish that, in terms of the level of pollution, it belongs to “zones of an environmental emergency.” Life expectancy is 4-6 years less compared to similar indicators in Russia.
Residents who live for a long time in conditions of natural and man-made pollution are exposed to abnormal concentrations of chemical elements that have a noticeable effect on the body. One of the manifestations is a change in the composition of the blood, the cause of which is a violation of the supply of iron and microelements (Cu, Co) to the body, associated with both their low content in food and the high content of compounds in food that prevent the absorption of iron in the gastrointestinal tract.
When monitoring biological and chemical parameters in 56 farms in different regions of the Urals, five variants of territories were conditionally identified, differing in environmental characteristics:
- * territories polluted by emissions from large industrial enterprises;
- * territories contaminated due to the activities of enterprises with long-lived radionuclides - strontium-90 and cesium-137 (East Ural radioactive trace - EURT);
- * territories experiencing pressure from industrial enterprises and at the same time located in the EURT zone;
- * geochemical provinces with high natural content of heavy metals (Zn, Cu, Ni) in soil, water, as well as abnormal concentrations of radon-222 in ground air and water;
- * territories that are relatively favorable in environmental terms, free from industrial enterprises
Ecological aspects of the chemistry of elements
Microelements and enzymes. Introduction to metalloenzymes. Specific and nonspecific enzymes. The role of metal ions in enzymes. Horizontal similarity in the biological action of d-elements. Synergy and antagonism of elements.
Propensity of d-element ions to hydrolysis and polymerization
In acidic environments, d-element ions are in the form of hydrated ions [M(H 2 O) m ] n+. With increasing pH, hydrated ions of many d-elements, due to their large charge and small ion size, have a high polarizing effect on water molecules, acceptor ability for hydroxide ions, undergo cationic hydrolysis, and form strong covalent bonds with OH - . The process ends either with the formation of base salts [M(OH) m ] (m-n)+, or insoluble hydroxides M(OH) n, or hydroxo complexes [M(OH) m ] (n-m)-. The process of hydrolytic interaction can occur with the formation of multinuclear complexes as a result of the polymerization reaction.
2. 4. Biological role of d-elements (transition elements)
Elements, the content of which does not exceed 10 -3%, are part of enzymes, hormones, vitamins and other vital compounds. For protein, carbohydrate and fat metabolism, the following are needed: Fe, Co, Mn, Zn, Mo, V, B, W; the following are involved in protein synthesis: Mg, Mn, Fe, Co, Cu, Ni, Cr; in hematopoiesis – Co, Ti, Cu, Mn, Ni, Zn; in breath - Mg, Fe, Cu, Zn, Mn and Co. For this reason, microelements are widely used in medicine, as microfertilizers for field crops, and as fertilizers in livestock, poultry and fish farming. Microelements are part of a large number of bioregulators of living systems, which are based on biocomplexes. Enzymes are special proteins that act as catalysts in biological systems. Enzymes are unique catalysts with unsurpassed efficiency and high selectivity. An example of the efficiency of the decomposition reaction of hydrogen peroxide 2H 2 O 2 ® 2H 2 O + O 2 in the presence of enzymes is given in Table 6.
Table 6. Activation energy (E o) and the relative rate of the decomposition reaction of H 2 O 2 in the absence and presence of various catalysts
Today, more than 2,000 enzymes are known, many of which catalyze a single reaction. The activity of a large group of enzymes manifests itself only in the presence of certain non-protein compounds called cofactors. Metal ions or organic compounds act as cofactors. About a third of enzymes are activated by transition metals.
Metal ions in enzymes perform a number of functions: they are an electrophilic group of the active center of the enzyme and facilitate interaction with negatively charged regions of substrate molecules, they form a catalytically active conformation of the enzyme structure (in the formation of the helical structure of RNA, zinc and manganese ions take part), and take part in electron transport (electron transfer complexes). The ability of a metal ion to perform its role in the active site of the corresponding enzyme depends on the ability of the metal ion to form complexes, the geometry and stability of the complex formed. This ensures increased selectivity of the enzyme towards substrates, activation of bonds in the enzyme or substrate through coordination and change in the shape of the substrate in accordance with the steric requirements of the active site.
Biocomplexes vary in stability. Some of them are so strong that they are constantly in the body and perform a specific function. In cases where the connection between the cofactor and the enzyme protein is strong and it is difficult to separate them, it is called a “prosthetic group”. Such bonds were found in enzymes containing a heme-complex compound of iron with a porphin derivative. The role of metals in such complexes is highly specific: replacing it even with an element similar in properties leads to a significant or complete loss of physiological activity. These enzymes include to specific enzymes.
Examples of such compounds are chlorophyll, polyphenyl oxidase, vitamin B 12, hemoglobin and some metalloenzymes (specific enzymes). Few enzymes take part in only one specific or single reaction.
The catalytic properties of most enzymes are determined by the active center formed by various microelements. Enzymes are synthesized for the duration of the function. The metal ion acts as an activator and can be replaced by another metal ion without loss of physiological activity of the enzyme. These are classified as nonspecific enzymes.
Below are enzymes in which different metal ions perform similar functions.
Table 7. Enzymes in which different metal ions perform similar functions
One trace element can activate different enzymes, and one enzyme can be activated by different trace elements. Enzymes with microelements in the same oxidation state +2 have the greatest similarity in biological action. As can be seen, microelements of transition elements in their biological action are characterized by more horizontal similarity than vertical similarity in the periodic system of D.I. Mendeleev (in the Ti-Zn series). When deciding on the use of a particular microelement, it is extremely important to take into account not only the presence of mobile forms of this element, but also others that have the same oxidation state and can replace each other in the composition of enzymes.
Some metalloenzymes occupy an intermediate position between specific and nonspecific enzymes. Metal ions act as a cofactor. Increasing the strength of the enzyme biocomplex increases the specificity of its biological action. The efficiency of the enzymatic action of the enzyme's metal ion is influenced by its oxidation state. According to the intensity of their influence, microelements are arranged in the following row:
Ti 4+ ®Fe 3+ ®Cu 2+ ®Fe 2+ ®Mg 2+ ®Mn 2+ . The Mn 3+ ion, unlike the Mn 2+ ion, is very tightly bound to proteins, and mainly with oxygen-containing groups, together Fe 3+ is part of metalloproteins.
Microelements in complexonate form act in the body as a factor that apparently determines the high sensitivity of cells to microelements through their participation in the creation of a high concentration gradient. The values of atomic and ionic radii, ionization energies, coordination numbers, and the tendency to form bonds with the same elements in bioligand molecules determine the effects observed during mutual substitution of ions: can occur with increasing (synergy) and with inhibition of their biological activity (antagonism) element being replaced. Ions of d-elements in the +2 oxidation state (Mn, Fe, Co, Ni, Zn) have similar physicochemical characteristics of atoms (electronic structure of the outer level, similar ion radii, type of orbital hybridization, similar values of stability constants with bioligands). The similarity of the physicochemical characteristics of the complexing agent determines the similarity of their biological action and interchangeability. The above transition elements stimulate hematopoietic processes and enhance metabolic processes. The synergy of elements in the processes of hematopoiesis is possibly associated with the participation of ions of these elements in various stages of the process of synthesis of formed elements of human blood.
The s - elements of group I are characterized, in comparison with other elements of their period, by a small charge of atomic nuclei, a low ionization potential of valence electrons, a large atomic size and its increase in the group from top to bottom. All this determines the state of their ions in aqueous solutions in the form of hydrated ions. The greatest similarity between lithium and sodium determines their interchangeability and the synergy of their action. The destructive properties of potassium, rubidium and cesium ions in aqueous solutions ensure their better membrane permeability, interchangeability and synergy of their action. The concentration of K + inside cells is 35 times higher than outside it, and the concentration of Na + in the extracellular fluid is 15 times higher than inside the cell. These ions are antagonists in biological systems. s - Group II elements are found in the body in the form of compounds formed by phosphoric, carbonic and carboxylic acids. Calcium, contained mainly in bone tissue, is similar in properties to strontium and barium, which can replace it in bones. In this case, both cases of synergy and antagonism are observed. Calcium ions are also antagonists of sodium, potassium and magnesium ions. The similarity of the physicochemical characteristics of Be 2+ and Mg 2+ ions determines their interchangeability in compounds containing Mg–N and Mg–O bonds. This may explain the inhibition of magnesium-containing enzymes when beryllium enters the body. Beryllium is an antagonist of magnesium. Consequently, the physicochemical properties and biological effects of microelements are determined by the structure of their atoms. Most biogenic elements are members of the second, third and fourth periods of the periodic system of D.I. Mendeleeva. These are relatively light atoms, with a relatively small charge on the nuclei of their atoms.
2. 4. 2. The role of transition element compounds in the transfer of electrons in living systems.
In a living organism, many processes have a cyclical, wave-like character. The chemical processes underlying them must be reversible. The reversibility of processes is determined by the interaction of thermodynamic and kinetic factors. Reversible reactions include those with constants from 10 -3 to 10 3 and with a small value of DG 0 and DE 0 of the process. Under these conditions, the concentrations of the starting substances and reaction products can be in comparable concentrations, and by changing them in a certain range, reversibility of the process can be achieved. From a kinetic point of view, there should be low values of activation energy. For this reason, metal ions (iron, copper, manganese, cobalt, molybdenum, titanium and others) are convenient carriers of electrons in living systems. The addition and donation of an electron causes changes only in the electronic configuration of the metal ion, without significantly changing the structure of the organic component of the complex. A unique role in living systems is assigned to two redox systems: Fe 3+ /Fe 2+ and Cu 2+ /Cu + . Bioligands stabilize to a greater extent the oxidized form in the first pair, and predominantly the reduced form in the second pair. For this reason, in systems containing iron, the formal potential is always lower, and in systems containing copper, the formal potential is often higher. Redox systems containing copper and iron cover a wide range of potentials, which allows them interact with many substrates, accompanied by moderate changes in DG 0 and DE 0, which meets the conditions of reversibility. An important step in metabolism is the abstraction of hydrogen from nutrients. Hydrogen atoms then transform into an ionic state, and the electrons separated from them enter the respiratory chain; in this chain, moving from one compound to another, they give up their energy to form one of the basic energy sources, adenosine triphosphoric acid (ATP), and they themselves ultimately reach an oxygen molecule and join with it, forming water molecules. The bridge along which electrons oscillate are complex compounds of iron with a porphyrin core, similar in composition to hemoglobin.
A large group of iron-containing enzymes that catalyze the process of electron transfer in mitochondria are commonly called cytochromes(ts.kh.), In total, about 50 cytochromes are known. Cytochromes are iron porphyrins in which all six orbitals of the iron ion are occupied by donor atoms, a bioligand. The difference between cytochromes is only in the composition of the side chains of the porphyrin ring. Variations in the structure of the bioligand are caused by differences in the magnitude of the formal potentials. All cells contain at least three proteins of similar structure, called cytochromes a, b, c. In cytochrome c, the connection with the histidine residue of the polypeptide chain occurs through the porphyrin core. The free coordination site in the iron ion is occupied by the methionine residue of the polypeptide chain:
One of the mechanisms of functioning of cytochromes, which make up one of the links in the electron transport chain, is the transfer of an electron from one substrate to another.
From a chemical point of view, cytochromes are compounds that exhibit redox duality under reversible conditions.
Electron transfer by cytochrome c is accompanied by a change in the oxidation state of iron:
c. X. Fe 3+ + e « c.xFe 2+
Oxygen ions react with hydrogen ions in the environment to form water or hydrogen peroxide. Peroxide is quickly decomposed by a special enzyme catalase into water and oxygen according to the following scheme:
2H 2 O 2 ®2H 2 O + O 2
The enzyme peroxidase accelerates the oxidation reactions of organic substances with hydrogen peroxide according to the following scheme:
These enzymes have a heme in their structure, in the center of which there is iron with an oxidation state of +3 (Section 2 7.7).
In the electron transport chain, cytochrome c transfers electrons to cytochromes called cytochrome oxidases. They contain copper ions. Cytochrome is a one-electron carrier. The presence of copper in one of the cytochromes along with iron turns it into a two-electron carrier, which makes it possible to regulate the rate of the process.
Copper is part of an important enzyme - superoxide dismutase (SOD), which utilizes the toxic superoxide ion O2- in the body through the reaction
[SOD Cu 2+ ] + ® O 2 - [SOD Cu + ] + O 2
[SOD Cu + ] + O 2 - + 2H + ® [SODCu 2+ ] + H 2 O 2
Hydrogen peroxide decomposes in the body under the action of catalase.
Today, about 25 copper-containing enzymes are known. Οʜᴎ constitute a group of oxygenases and hydroxylases. The composition and mechanism of their action are described in work (2, section 7.9.).
Transition element complexes are a source of microelements in a biologically active form with high membrane permeability and enzymatic activity. Οʜᴎ take part in protecting the body from “oxidative stress”. This is due to their participation in the utilization of metabolic products that determine the uncontrolled oxidation process (peroxides, free radicals and other oxygen-active species), as well as in the oxidation of substrates. The mechanism of the free radical reaction of substrate oxidation (RH) with hydrogen peroxide with the participation of an iron complex (FeL) as a catalyst can be represented by reaction schemes.
RH + . OH ® R . + H 2 O; R. + FeL ® R + + FeL
Substrate
R + + OH - ® ROH
Oxidized substrate
Further occurrence of the radical reaction leads to the formation of products with a higher degree of hydroxylation. Other radicals act similarly: HO 2. , O 2 . , . O 2 - .
2. 5. General characteristics of p-block elements
Elements in which the p-sublevel of the outer valence level is completed are called p-elements. Electronic structure of the ns 2 p 1-6 valence level. Valence electrons are the s- and p-sublevels.
Table 8. Position of p-elements in the periodic table of elements.
| Period | Group | |||||
| IIIA | IVA | V.A. | VIA | VIIA | VIIIA | |
| (C) | (N) | (O) | (F) | Ne | ||
| (P) | (S) | (Cl) | Ar | |||
| Ga | Kr | |||||
| In | Sn | Sb | Te | (I) | Xe | |
| Tl | Pb | Bi | Po | At | Rn | |
| p 1 | p 2 | p 3 | p 4 | p 5 | R 6 | |
| () - essential elements, – biogenic elements |
In periods from left to right, the charge of nuclei increases, the influence of which prevails over the increase in the forces of mutual repulsion between electrons. For this reason, the ionization potential, electron affinity, and, consequently, the acceptor capacity and non-metallic properties increase in periods. All elements lying on the Br – At diagonal and above are non-metals and form only covalent compounds and anions. All other p-elements (with the exception of indium, thallium, polonium, bismuth, which exhibit metallic properties) are amphoteric elements and form both cations and anions, both of which are highly hydrolyzed. Most non-metal p-elements are biogenic (the exceptions are the noble gases, tellurium and astatine). Of the p-elements - metals - only aluminum is classified as biogenic. Differences in the properties of neighboring elements, both inside; and by period: they are expressed much more strongly than those of s-elements. p-elements of the second period - nitrogen, oxygen, fluorine have a pronounced ability to participate in the formation of hydrogen bonds. Elements of the third and subsequent periods lose this ability. Their similarity lies only in the structure of the outer electron shells and those valence states that arise due to unpaired electrons in unexcited atoms. Boron, carbon and especially nitrogen are very different from the other elements of their groups (the presence of d- and f-sublevels).
All p-elements and especially p-elements of the second and third periods (C, N, P, O, S, Si, Cl) form numerous compounds with each other and with s-, d- and f-elements. Most of the compounds known on Earth are compounds of p-elements. The five main (macrobiogenic) p-elements of life - O, P, C, N and S - are the main building material from which the molecules of proteins, fats, carbohydrates and nucleic acids are composed. Of the low molecular weight compounds of p-elements, the most important are the oxoanions: CO 3 2-, HCO 3 -, C 2 O 4 2-, CH3COO -, PO 4 3-, HPO 4 2-, H 2 PO 4 -, SO 4 2- and halide ions. p-elements have many valence electrons with different energies. Therefore, compounds exhibit different degrees of oxidation. For example, carbon exhibits various oxidation states from –4 to +4. Nitrogen – from -3 to +5, chlorine – from -1 to +7.
During the reaction, the p-element can donate and accept electrons, respectively acting as a reducing agent or an oxidizing agent, depending on the properties of the element with which it interacts. This gives rise to a wide range of compounds formed by them. The mutual transition of atoms of p-elements of various states of oxidation, including due to metabolic redox processes (for example, the oxidation of an alcohol group into their aldehyde group and then into a carboxyl group, and so on) causes a wealth of their chemical transformations.
A carbon compound exhibits oxidizing properties if, as a result of the reaction, carbon atoms increase the number of its bonds with atoms of less electronegative elements (metal, hydrogen) because, by attracting common bond electrons, the carbon atom lowers its oxidation state.
CH 3 ® -CH 2 OH ® -CH = O ® -COOH ® CO 2
The redistribution of electrons between the oxidizing agent and the reducing agent in organic compounds can only be accompanied by a shift in the total electron density of the chemical bond to the atom acting as the oxidizing agent. In the case of strong polarization, this connection may be broken.
Phosphates in living organisms serve as structural components of the skeleton of cell membranes and nucleic acids. Bone tissue is built mainly from hydroxyapatite Ca 5 (PO 4) 3 OH. The basis of cell membranes is phospholipids. Nucleic acids consist of ribose or deoxyribose phosphate chains. In addition, polyphosphates are the main source of energy.
In the human body, NO is necessarily synthesized using the enzyme NO synthase from the amino acid arginine. The lifetime of NO in the cells of the body is on the order of a second, but their normal functioning is not possible without NO. This compound ensures: relaxation of smooth muscles of vascular muscles, regulation of heart function, effective functioning of the immune system, transmission of nerve impulses. NO is believed to play an important role in learning and memory.
Redox reactions in which p-elements take part underlie their toxic effect on the body. The toxic effect of nitrogen oxides is associated with their high redox ability. Nitrates that enter food are reduced to nitrites in the body.
NO 3 - + 2H + + 2e ® NO 2 + H 2 O
Nitrites have highly toxic properties. Οʜᴎ convert hemoglobin into methemoglobin, which is a product of hydrolysis and oxidation of hemoglobin.
As a result, hemoglobin loses its ability to transport oxygen to the body's cells. Hypoxia develops in the body. At the same time, nitrites, as salts of a weak acid, react with hydrochloric acid in the gastric contents, forming nitrous acid, which, with secondary amines, forms carcinogenic nitrosamines:
The biological effect of high-molecular organic compounds (amino acids, polypeptides, proteins, fats, carbohydrates and nucleic acids) is determined by atoms (N, P, S, O) or formed groups of atoms (functional groups), in which they act as chemically active centers , donors of electron pairs capable of forming coordination bonds with metal ions and organic molecules. Consequently, p-elements form polydentate chelating compounds (amino acids, polypeptides, proteins, carbohydrates and nucleic acids). It is worth saying that they are characterized by complex formation reactions, amphoteric properties, and anionic hydrolysis reactions. These properties determine their participation in basic biochemical processes and in ensuring the state of isohydry. Οʜᴎ form protein, phosphate, hydrogen carbonate buffer systems. Participate in the transport of nutrients, metabolic products, and other processes.
3. 1. The role of the habitat. Chemistry of atmospheric pollution. The role of the doctor in protecting the environment and human health.
A.P. Vinogradov showed that the surface of the earth is heterogeneous in chemical composition. Plants and animals, as well as humans, located in different zones, use nutrients of different chemical compositions and respond to this with certain physiological reactions and a certain chemical composition of the body. The effects caused by microelements depend on their intake into the body. The concentrations of biometals in the body during its normal functioning are maintained at a strictly defined level (biotic dose) with the help of appropriate proteins and hormones. The reserves of biometals in the body are systematically replenished. Οʜᴎ are contained in sufficient quantities in the food consumed. The chemical composition of plants and animals used for food affects the body.
Intensive industrial production has led to pollution of the natural environment with “harmful” substances, including compounds of transition elements. In nature, there is an intensive redistribution of elements in biogeochemical provinces. The main route (up to 80%) of their entry into the body is our food. Taking into account anthropogenic pollution of the environment, it is extremely important to take radical measures to rehabilitate the environment and the people living in it. This problem in many European countries is put ahead of the problems of economic growth and is among the priorities. In recent years, the release of various pollutants has increased. The forecast for industrial development allows us to conclude that the amount of emissions and environmental pollutants will continue to increase.
Real zones in which the cycle of elements occurs as a result of life activity are called ecosystems or, as Academician V.N. called it. Sukachev, biogeocenoses. Humans are an integral part of the ecosystems on our planet. In his life activities, a person can disrupt the course of the natural biogenic cycle. Many industries pollute the environment. According to the teachings of V.I. Vernadsky, the shell of our planet, changed by human economic activity, is called noosphere. It covers the entire biosphere and goes beyond its limits (stratosphere, deep mines, wells, etc.). The main role in the noosphere is played by technogenic migration of elements - technogenesis. Research on the geochemistry of the noosphere is the theoretical basis for the rational use of natural resources and the fight against environmental pollution. Gaseous, liquid, and solid environmental pollution form toxic aerosols (fog, smoke) in the ground layer of the atmosphere. When the atmosphere is polluted with sulfur dioxide, high humidity and no temperature, toxic smoke is formed. The main damage to the environment is caused by the oxidation products SO 2, SO 3 and acids H 2 SO 3 and H 2 SO 4. As a result of emissions of sulfur oxide and nitrogen, “acid” rain is observed in industrial regions. Rainwater containing high concentrations of hydrogen ions can leach toxic metal ions:
ZnO(t) + 2H + = Zn 2+ (p) + H 2 O
When an internal combustion engine operates, nitrogen oxides are released, the conversion product of which is ozone:
N 2 + O 2 « 2NO (in the engine cylinder)
Of great concern to society are environmental problems, the chemical essence of which is to protect the biosphere from excess carbon oxides and methane, which create the “greenhouse effect”, sulfur and nitrogen oxides leading to “acid rain”; halogen derivatives (chlorine, fluorine) of hydrocarbons that violate the “ozone shield of the Earth”; carcinogenic substances (polyaromatic hydrocarbons and products of their incomplete combustion) and other products. Nowadays, not only the problem of environmental protection, but also the protection of the internal environment is becoming relevant. The number of substances entering a living organism that are foreign, alien to life and called xenobiotics. According to the World Health Organization, there are about 4 million of them. They enter the body with food, water and air, as well as in the form of medicines (dosage forms).
This is due to the low culture of producers and consumers of chemicals who do not have professional chemical knowledge. Indeed, only ignorance of the properties of substances and the inability to foresee the consequences of their excessive use can cause irreparable losses of nature, of which man is an integral element. Indeed, to this day, some manufacturers, and even medical workers, are likened to Bulgakov’s miller, who wanted to immediately recover from malaria with an incredible (shock) dose of quinine, but did not have time - he died. The role of various chemical elements in environmental pollution and the occurrence of diseases, including occupational ones, is still insufficiently studied. It is necessary to analyze the entry of various substances into the environment as a result of human activity, the ways they enter the human body, plants, their interaction with living organisms at different levels, and develop a system of effective measures aimed at both preventing further environmental pollution and creating the necessary biological means of protecting the internal environment of the body. Medical workers are required to take part in the development and implementation of technical, preventive, sanitary, hygienic and therapeutic measures.
3.2 Biochemical provinces. Endemic diseases.
Zones within which animals and plants are characterized by a certain chemical elemental composition are called biogeochemical provinces. Biogeochemical provinces are third-order taxa of the biosphere - territories of various sizes within subregions of the biosphere with constant characteristic reactions of organisms (for example, endemic diseases). There are two types of biogeochemical provinces - natural and technogenic, resulting from the development of ore deposits, emissions from the metallurgical and chemical industries, and the use of fertilizers in agriculture. It is necessary to pay attention to the role of microorganisms in creating the geochemical characteristics of the environment. Deficiency and excess of elements can lead to the formation of biogeochemical provinces, caused by both a deficiency of elements (iodine, fluorine, calcium, copper, etc. provinces) and their excess (boron, molybdenum, fluorine, copper, etc.). The problem of bromine deficiency within continental regions, mountainous regions and bromine excess in coastal and volcanic landscapes is interesting and important. In these regions, the evolution of the central nervous system proceeded qualitatively differently. In the Southern Urals, a biogeochemical province was discovered on rocks enriched in nickel. It is worth saying that it is characterized by ugly forms of grasses and sheep diseases associated with an increased nickel content in the environment.
The correlation of biogeochemical provinces with their ecological state made it possible to identify the following territories: a) with a relatively satisfactory ecological situation - (zone of relative well-being); b) with reversible, limited, and in most cases removable environmental violations - (environmental risk zone); c) with a sufficiently high degree of disadvantage observed over a long period over a large territory, the elimination of which requires significant costs and time - (zone of ecological crisis); d) with a very high degree of environmental distress, practically irreversible environmental damage that has a clear localization -( ecological disaster zone).
Based on the impact factor, its level, duration of action and area of distribution, the following natural-technogenic biogeochemical provinces are identified as risk and crisis zones:
1. polymetallic (Pb, Cd, Hjg, Cu, Zn) with dominant associations Cu–Zn, Cu–Ni, Pb–Zn, including:
· enriched with copper (Southern Urals, Bashkortostan, Norilsk, Mednogorsk);
· enriched with nickel (Norilsk, Monchegorsk, Nickel, Polyarny, Tuva, Southern Urals);
· enriched with lead (Altai, Caucasus, Transbaikalia);
· enriched with fluorine (Kirovsk, Krasnoyarsk, Bratsk);
· with a high content of uranium and radionuclides in the environment (Transbaikalia, Altai, Southern Urals).
2. biogeochemical provinces with deficiencies of microelements (Se, I, Cu, Zn, etc.).