Environment

What is environmental protection

By the notion of environmental protection we understand all activities whose aim is to exploit, maintain and, if possible, replenish sensible resources and riches of natural environment. Apart from informal activities (ecological organizations and movements), some ecological activities became formalized and made global. Furthermore, international legislative and executive institutions take care of the protection of natural resources.

The conception of environmental protection appeared in the 19th century when the processes of industrialization sped up (the development of industry, the growth of cities, the increased exploitation of natural resources) which entailed new threats, such as pollution. At that time people became conscious of human destructive influences and the necessity of protecting their resources.

In the 20th century the development of industry progressed. This intensive expansion, which often took the form of overexploitation, caused other dangers and, accordingly, the development of activities whose aim was to protect the environment. Nowadays these problems are more often than not, regulated by law.

The main activities concerning environmental preservation, some more global than others, include the introduction of restrictions on the emission of harmful chemical compounds, a prohibition on using particularly destructive substances, protection of valuable ecosystems (national and landscape parks) and specific riches (natural features of historic importance). Environmental protection also involves less spectacular actions, such as promoting cleanliness, waste segregation, saving natural resources by more sensible use of, for example, water and energy.

Types of environmental pollution

Human activity is characterized by a huge diversity and practically in every field pollution may be generated. Pollution can be divided in terms of environment or the area of contamination: air pollution, soil pollution, water pollution and landscape pollution. We distinguish various types of pollution: dust, gases, sewage, waste, radioactive contamination and also noise and light.

Anthropogenic air pollution is mainly the result of the emission of harmful dust, gases and aerosols into the atmosphere. These harmful substances come from industrial, food-processing and transport activity.

Water pollution is the effect of water contamination by sewage and waste. Additional factors which pollute are: water transport (direct influence) and using pesticides and chemical fertilizers in agriculture; these agents penetrate through soil into ground water and then into cycle. What is more, the cycle of water in the nature is disturbed due to forest destruction, improper farming and the development of cities.

Soil is usually polluted by extensive and irresponsible waste disposal, using fertilizers and plant protection agents. It is also polluted indirectly by air, rainfall and ground water pollution.

Landscape pollution includes, first of all, omnipresent rubbish, waste stockpiles, dumps, slag heaps and damage caused by the exploitation of fossil deposits, everything that lowers the aesthetic qualities of the environment and frequently results in the destruction of nearby ecosystems.

Although light and noise pollution does not cause damage to the particular environment (air, land or water) and it might seem to be exaggeration of the problem, it becomes more and more serious threat to big cities and their surroundings. Artificial light has a negative influence on animals' and people's vital functions. The negative influence of the excess of light affects especially organisms which are active at night. Birds suffer as well - city lights made them disorientated during migrations. People are advised against sleeping in places which are lit by street lamps since it causes sleep disorders and in extreme cases it may lead to insomnia and exhaustion of organism.

There is no doubt that noise has a negative influence and, as scientists discovered, about 40% of Europeans live in conditions in which the noise generated by traffic exceeds the 55 decibels, so it exceeds the safe level (serious hearing irritation) during day whereas 30% Europeans are subject to noise which goes above 30 decibels even at night and at this level sleep is disturbed.

The effects of the environmental pollution

Environmental pollution has a destructive influence on a global scale - the problem concerns our whole planet and also local places - the existing threats are different in various countries.

On a macro scale people and by-products of their activity in the form of harmful substances polluting the air, soil and water, led to the increase in the greenhouse effect and consequently to global climate warming, the ozone hole and acidified precipitation. And thus:
The greenhouse effect caused by the emission of gases which increase temperatures on the Earth (carbon dioxide, ozone, CFCs) and forest thinning (lower intake of carbon dioxide, lower production of oxygen) result in climate change, ice melting, disturbance of vital functions of fauna and flora and even extinction of some species. Climate changes cause a wide range of atmospheric phenomena (hurricanes, rain, floods, hailstorm) on an unusual scale and make climate unpredictable.
The ozone hole is the result of the emission of CFCs into the atmosphere, it exposes us to the harmful effects of solar ultraviolet radiation; fortunately people partly handled this problem by prohibiting the production and emission of harmful substances, due to which the level of ozone in the upper layers of the atmosphere will be probably restored.
Acid rain, caused by the emission of sulfur dioxide and nitric oxides, has a destructive influence on soil and water and, accordingly, an indirect effect on living organisms.

On a macro scale each threat mentioned above influences: separate elements of the natural environment, plants, animals, whole ecosystems. They also cause diseases associated with the progress of civilization, for example allergies incidence rate has increased, more and more people suffer from diseases of blood circulation system and cancer.

The methods of environmental preservation

To protect the environment it is necessary to take action at local level as well as cooperate at international level.

On a global scale United Nations and various international committees and ecological organizations deal with the environmental protection. The aim of formalized activities is to introduce legal articles regulating the issues of environmental protection: restrictions on the emission of harmful compounds, the methods of waste recycling, prohibitions and promotion of specific activities.

The general aim of such activities is to eliminate threats; however, it should not mean ceasing all kinds of activities since it would defeat the purpose and stop the development; the point is that we ought to learn how to exploit the natural resources sensibly and let technology develop, taking into consideration our and environmental protection. And these types of actions are possible even at specific unit's level. All of us have considerable influence on the use of natural resources and clean environment. Every person is able to limit the emission of exhaust fumes, they just have to choose transport public or a bicycle instead of a car from time to time. We will be also ecological-friendly if we save water and energy, support waste recycling (by rubbish segregation) and first and foremost we will be aware of all the existing threats and the fact that it is human mindlessness that often leads to accidents with tragic consequences (ecological catastrophes).

Diseases caused by environmental pollution

Harmful effect of environmental pollution manifests itself in lowered immunity to all kinds of diseases which means that human organism becomes more liable to pathogenic influence of various factors.

This influence can be direct or indirect. All harmful chemical compounds we take in with the air or water have direct, toxic impact on people. Animals and plants which are also influenced by pollution in the process of nourishment become the source of harmful substances which we assimilate indirectly while eating.

As far as specific diseases caused by pollution are concerned, they are, above all, all kinds of diseases associated with the progress of civilizations. Their development, variety and incident rate depend closely on industrialization and changes in the quality and style of life resulting from the progress of our civilization. These diseases include cancer, allergies, asthma, sight and hearing diseases (caused by the excess of light, noise, ultraviolet radiation), neurosis, diseases of blood circulation system, skin diseases.

All kinds of emitted pollution has impact on our health and it is impossible to discuss it briefly; nevertheless, their influence is indisputable, especially as in industrialized areas incidence rate of diseases associated with the progress of civilization has increased which is contrary to the areas with less developed industry or with no industry at all; in these areas contagious diseases are more frequent.

Even a special field of medicine was distinguished - environmental medicine. Its aim is to deal with diagnosis, treatment and, above all, prevention of health problems caused by environmental pollution.

http://ourecology.org/index.html

Climate change

As a result of abnormal weather conditions caused by climate changes (such as hurricanes), about 160 000 people die every year. Within 50 years even one third of all species of plants and animals may die. We are the last generation that can put an end to it.

Earth's atmosphere is made of a gas layer. These gases, which trap heat, allow to maintain life on the Earth. This is natural greenhouse effect without which life on the Earth would be impossible. However, human activity contributes to the escalation of this effect. By burning fossil fuels necessary for the production of energy and for transport, people release milliards of tones of carbon dioxide. It is the main greenhouse gas emitted due to human activity. Changes in the land, for example caused by cutting down forests, also contribute to the increase in CO2 in the environment. For instance, trees naturally absorb CO2, so when they are cut down, all carbon dioxide they absorbed during their life is emitted into the atmosphere.

Furthermore, industry and other branches of human activity increase the number of gases which appear in the atmosphere naturally, such as methane (CH4) coming from the rice growing, animal breeding and waste fermenting on dumps, and nitrous oxide (N2O) which comes mainly from agriculture. Methane has 21 times higher potential for heating climate than carbon dioxide and it contributes to the greenhouse effect in 18%. The potential of nitrous oxide for heating is 310 times higher in comparison with carbon dioxide but it is emitted in less amount and it contributes to greenhouse effect in 6%.

These gases escalate the greenhouse effect, they thicken the natural layer of gases in the atmosphere and contribute to trapping more heat. As a result, temperature rises and upsets the balance of the atmosphere.

Whereas the presence of many greenhouse gases is natural, the pace with which people add them to the atmosphere differs a lot form the natural one. It was estimated that presently the amount of CO2 in the atmosphere is higher than before the industrial revolution during which people started to burn fossil fuels on a large scale. Owing to industrial activity, people also produce new gases such as HFC and PFC (compounds from the group of hydrofluorohydrocarbons).

Although there are doubts about the scale of climate change, there is general consensus that:
Warming by about 1.3oC is inevitable due to the concentration of carbon dioxide in the atmosphere. We have to keep warming below 2oC if we want to prevent the worst scenario of climate changes.
If the emission of gases is not stopped, climate changes will take place much faster during the next 100 years than now.

There is every likelihood that the mechanism of climate feed-back will result in even faster and irreversible climate changes. In this phenomenon thermal gases absorb rays reflected from the surface of the Earth which causes rise in temperature; secondary effects, associated with the increase in the amount of water vapour in the atmosphere, might cause changes in cloud cover, trapping even more heat, and consequently climate changes. Nobody knows how much time it will take global warming to fulfill the worst-case scenario.

http://ourecology.org/climate_change.html

Recycling

Recycling involves using waste, worn out elements (e.g. parts of machines) to make new products, e.g. waste paper to produce paper, worn out tyres to produce fuel used in cement plants. Waste includes all objects and solids as wells as liquid substances which are not sewage and which come from human economic and living activity. Types of waste include: agricultural, industrial and municipal.

Recycling is significant to environmental protection. Some car companies strive for the possibility of recycling above 90% of steel and coloured metals they use for the production of cars; they also use plastics which can be recycled.

Large amounts of paper, metal, plastic and glass waste are used again in the process of recycling (utilization). In western countries the majority of these materials are gathered in special containers at homes or in factories. However, the rest of rubbish also contains many valuable materials which can be separated in various stages of their processing before they land in dump. Dried rubbish is burnt in anaerobic conditions in order to get such useful substances as carbon oxide, methane, hydrogen, mineral oils, tar or charcoal. Ferromagnetic metals (including iron or nickel) are taken from a conveyor belt which transports rubbish by strong magnets which hang above it. Also glass, aluminum and other non-ferrous metals are separated in order to take advantage of their various physical characteristics.

The process of separating materials is often based on the difference in their density, namely specific gravity. One of the separators works in this way that powdered rubbish falls on a conveyor band which goes upwards; the material with higher density falls down and the lighter material goes up. If we burn rubbish, metals and glass melt and they fall on the bottom of a stove from where they can be easily gathered.

Later glass separated from rubbish can be sorted into coloured and white. In order to do that, ground glass goes through strong magnetic field. Pieces of white glass do not interact with the field whereas coloured glass does and it is separated. The pieces of glass go through streams of light and the changes in their colour are recorded by photosensitive elements. On the basis of the signal they send, machines sort the glass - each colour separately.

http://ourecology.org/recycling.html

Ecosystem

Ecosystem is a unit consisting of living organisms which form biocenosis with all elements of inanimate environment, namely biotope. Every natural ecosystem is an open system and functions due to the flow of energy and matter circulation. Energy flow is one-way whereas matter circles in ecosystem in closed circuit. Solar power is the most important power in ecosystems. Not all energy is accumulated in organisms. Some of it is used for basic metabolic processes and building structures of organisms; however, some of it is lost in the form of heat.

To make matter circulation possible, the presence of producers, consumers and reducers, or at least producers and reducers, is essential. Owing to producers organic matter is synthesized. Consumers eat organisms or dead organic matter. Decomposers (reducers) decompose dead organic matter and release inorganic nutrients for producers. Due to reducers and decay processes:
matter circulation in the environment is closed influencing growth and development of plants,
nutrients are included in the circulation,
food for heterotrophic organisms is produced.

Ecosystem is divided into:
autotrophic ecosystem which functions on the basis of the presence of light and organic matter called autochthonous matter which is produced in the process of photosynthesis mainly by green plants. The examples of such ecosystems are a forest, a peat bog, a meadow, a pond, a lake.
heterotrophic ecosystem which is incomplete, which is not self-sufficient, devoid of producers, where matter comes from outside and is called allochthonous matter. The example of such an ecosystem is a cave. The lack of light makes it impossible for plants to exist.

http://ourecology.org/ecosystem.html

Greenhouse effect

What is greenhouse effect

Greenhouse gases warm the atmosphere, thermal radiation is absorbed by the planet and the temperature increases. This phenomenon is called greenhouse effect as its mechanisms are similar to the processes which occur in a greenhouse. In this case the atmosphere of the planet functions as glass which enables to heat the surface from one side and from the other side it absorbs heat emitted by the surface thereby causing global increase in temperature. To be brief, the atmosphere and gases it includes allow the radiation emitted by the Sun to get inside; however, at the same time, they trap the radiation of the heated Earth and do not allow it to escape and direct it towards the surface again. We receive the same amount of energy but the accumulation of the compounds which trap the Earth radiation in the atmosphere favors the increase in temperature.

Gases and aerosols are responsible for this.

Greenhouse effect is a thoroughly natural phenomenon which was observed not only on the Earth but also on other celestial bodies in our solar system, namely on Mars, Venus and Titan (moon of Saturn).

Natural greenhouse effect

The greenhouse effect is essential to life on our planet. Due to the ability to absorb and trap part of heat, it was possible for life to be created and survive. The greenhouse effect, owing to the specific role of atmosphere on every planet, is a natural phenomenon. Only on the Earth it takes on alarming proportions due to human activity. Natural heating of the planet is the effect of heat exchange. This process looks as follows: solar radiation carries thermal energy, when it reaches the Earth, it heats the atmosphere and the surface; water, forests and whole environment are heated as well. The Earth does not absorb the whole radiation, some of it is reflected; every light surface which reflects light also reflects thermal energy. This process is increased by some compounds and formations contained in the air (clouds, some aerosols). On the other hand, clouds and some gases let in and absorb energy thereby increasing temperature. Heating is not a one-way process. Ultraviolet objects heated by radiation emit all or part of radiation in a reverse process - long-wave infrared radiation. But for the atmosphere and the presence of compounds limiting the emission outside, all radiation would be transmitted to space. Nevertheless, the returned emission is stopped, heat balance of the Earth is positive, i.e. the amount of heat which reaches the Earth exceeds the amount of heat which leaves the Earth. This process leads to increase in temperature.

The causes of the greenhouse effect

The atmosphere of our planet is the air which is the mixture of various gases and aerosols. The composition of the atmosphere depends on the height. To put it simply, this is a composite mixture of gases. The most common gases are nitrogen (over 78%) and oxygen (28%). Other gases constitute only a fraction of the whole mixture; however, we cannot ignore their importance.

The main greenhouse gas is water vapour. According to scientists, it is responsible for the greenhouse effect in 30 to 60 per cent. The amount of the vapour in the atmosphere is not fixed and it fluctuates depending on a time of the day, season or area. Clouds are made of vapour, its presence can be easily stated with our own eyes. The vapour is also significant due to the fact that, on one hand, it absorbs perfectly some solar radiation and, on the other hand, it substantially limits heat return in the form of infrared radiation. Its presence in the atmosphere is the result of evaporating water: seas, lakes, oceans and also evaporating water from ground, plants and other organisms. The atmosphere is cleaned by rainfall and the process of vapour exchange and water cycle in the nature is dependant on temperature: the higher temperature the higher water evaporation rate; as a result the content of water vapour in the air increases and so does the greenhouse effect.

Another greenhouse gas is carbon dioxide. It was discovered in the atmosphere a long time ago and it is one of the factors responsible for life-friendly temperature. However, as the result of the emission of carbon dioxide in the process of fuel burning and forest burning, its greenhouse effect increases and so does its influence on climate. Carbon dioxide is responsible for the greenhouse effect at about 9 to 26% and the ability to absorb infrared radiation is 1. Methane has a considerable influence on climate warming. This gas is produced in natural processes, mainly by bacteria which decompose organic matter (remains of plants and animals). The excess of methane in the air and thereby enhancing the greenhouse effect are caused by mining industry and stockpiles of organic waste (dumps). The ability of methane to absorb infrared radiation is thirty times higher than the ability of carbon dioxide.

Other gases which cause and enhance the greenhouse effect (as a result of emission caused by people) are nitric oxides, including nitrous oxide, ozone and CFCs. The ability of nitrous oxide to absorb thermal radiation is 150 higher than the ability of carbon dioxide; this gas is produced in the emission of exhaust fumes and while using nitric fertilizers in farming.

Ozone, which is the protective ozone sphere in upper layers, in lower layers prevents heat produced on the Earth from escaping and its absorbency is 200 times higher than the same abilities of carbon dioxide. The content of greenhouse ozone increases due to chemical reactions of carbon monoxide, hydrocarbons and nitric oxides emitted in industrial burning processes.

And finally CFCs which are not natural as they were produced by people. Although there are not many CFCs in the air, their ability to trap radiation is from ten to twenty thousand higher than the ability of carbon dioxide.

Greenhouse effect and global warming

The issue of the greenhouse effect on climate change is debatable even in a scientific environment. Nevertheless, it is widely assumed that the greenhouse effect or its intensification resulting from human activity, has impact on global warming. The facts are clear: within the space of one century, i.e. from the beginning of the 20th century to the beginning of the 21st century, average temperature increased by 0.7%. What is more, there was a rise in the emission of carbon dioxide and other greenhouse gases. The estimated probability that it was caused by human activity and not by natural reasons is 90% (data from IV Report of the Intergovernmental Panel on Climate Change). Scientists who are skeptical about this theory claim that this change was caused by change in the activeness of the Sun which always influenced our planet, even before the intensification of human industrial activity.

There are other examples of climate change, such as a rise in average temperature on poles (the Arctic - average yearly temperature increased by 3oC and by 7oC in winter), changes in a moderate climate - which can be observed in hot summers and relatively warm winters. Furthermore, climatic zones are shifting to the Equator and, as a result, areas on which droughts occur are extending.

If this process continues, in the next century the consequences will be much more worrying: permafrost melting will cause the creation of bogs which consequently will increase the emission of methane and carbon dioxide. Due to the increase in the amount of carbon dioxide and methane in the air, the temperature of the Earth will rise by about 2oC which will influence ice melting and cause level of water to rise, as a result vast areas of the Earth will be threatened with flooding. From 1880 to 1990 the level of seas and oceans increased by about 11 cm.

Air circulation may be disturbed, climatic zones will shift, we will lose huge areas of farming lands and forest areas. Paradoxically global warming may lead to another Ice Age (ice melting will prevent warm sea currents).

To sum up, scientists agree that the greenhouse effect enhanced by people will speed up the process of global warming and global climate changes which may lead to unpredictable consequence in the future - even extermination of humankind and life on the Earth.

Forests and greenhouse effect

One of the main greenhouse gases responsible for the greenhouse effect, i.e. gases which absorb heat and trap it in the Earth atmosphere, is carbon dioxide. It is widely known that this gas is converted into oxygen by plants (photosynthesis). It means that the presence of carbon dioxide in the air is closely associated with the condition of plants on the Earth. Being a treasure trove of plants and lungs of our planet, forests are of great importance.

Most of forest areas have been destroyed and some of them are still being destroyed due to territorial expansion. They are cut down and burnt down. As a result of both processes we lose vast areas of forests which regulate gas and thermal economy of our planet. By burning forests we contribute to increase in the emission and concentration of carbon dioxide in the atmosphere.

Forests also absorb humidity thereby protecting the air from the excess of carbon dioxide. High humidity facilitates storing carbon dioxide in lower layers of the atmosphere owing to which it is kept in forests and does not escape to higher layers where it could cumulate heat. According to scientists' opinion, about 15% of the emission of carbon dioxide to the atmosphere is the effect of the destruction of forest areas.

Another problem connected with the greenhouse effect is destruction of rain forests. Not only are these huge green areas the treasure trove of nature and a place where oxygen is produced, they also regulate the amount of heat and light absorbed and reflected by the Earth. The ration of light reflection is called albedo. The colors of forests are dark so they absorb light radiation. If forests are destroyed, the light is reflected. Significant changes in the albedo ration influence winds, sea currents and rainfall, in other words, they cause climatic changes.

http://ourecology.org/greenhouse_effect.html

Environ Sci - Lecture 17

Environmental Issues

1. What is pollution?
Pollution is the contamination of an ecosystem by factors that are harmful for the equilibrium of its biotic or abiotic constituents.

 2. Is pollution always caused by humans?

In most cases pollution is caused by human activity. Other species and some abiotic factors however can also pollute an ecosystem. For example, the red tide is created by proliferation of some algae and volcanic dust is a consequence of the internal activity of the planet.

3. Why is waste considered one of the major environmental issues?

The environmental problem concerning waste worsens with industrial development and the global growth of consumption societies in the 20th and 21st centuries, factors that cause the immense volume of residuals produced by mankind in the last decades. The increased waste generation raises the issue about what to do with waste since nature is not able to degrade and resorb with adequate speed and efficiency most of the residuals. Therefore the various kinds of waste accumulate, polluting the environment and creating danger to humans and nature. (The present destination of waste has been public waste depositories where the waste volume is compressed and buried underground, an environmentally risky method. Another method has been incineration, with the grave consequence of causing air pollution.)

4. What are the main types of waste?

The waste can be classified into many types, each of them carrying its own different environmental problem: organic waste, recyclable waste, non recyclable waste, toxic waste, nuclear toxic waste and space waste.

The organic waste is more easily resorbed by nature, but the speed and the geographical concentration of its production due to urbanization generate pollution of rivers, lakes, proliferation of disease vectors and environmental degradation of towns. The recyclable waste is composed of residuals that can be reprocessed, used again by humans, like plastics and metals; the problem regarding recyclable waste is that the separation of such material is not culturally diffused and there is not enough social organization to use them; so the recyclable waste is mixed to other wastes increasing the volume of waste depositories even more. The non recyclable waste is formed of residuals that technology cannot yet recycle, like ceramics, photographic paper, mirrors, cigarettes, plasticized papers, etc; this kind of waste in the future may become recyclable waste and should be separated. The toxic waste includes industrial chemical residuals that are harmful for life and the environment, like contaminated medical waste and the domestic waste containing insecticides and medicines; the toxic waste is one of the major environmental problems since it puts the life of humans and other living beings in danger. The nuclear toxic waste is made of materials that release invisible dangerous radiation for many years; nuclear toxic waste is produced in the extraction of nuclear minerals (like uranium), by nuclear reactors and nuclear plants, in hospitals where Nuclear Medicine is performed and in research centers; although the nuclear waste is often put into armored receptacles the risk of accidents is permanent. Space waste is the waste produced by the activity of humans in space from the second half of the 20th century; it consists of non operating satellites, rocket piece and other equipments that remain orbiting the earth or other celestial bodies or even travelling across space.

 5. What is selective waste collection?

Recyclable waste is waste that can be reprocessed and used again. Waste recycling depends on the separation of the recyclable residuals from non recyclable ones and on the classification of the recyclable into plastics, metals, papers, etc. The function of the selective waste collection is to simplify that separation for the waste to be sorted at the point of origin. Selective collection also helps the creation of an environmental conscience in the people that produce the waste.
 
6. What is the cost-benefit relationship regarding sewage treatment as a strategy to fight water pollution?

To treat sewage is much cheaper for society. The non treated sewage pollutes rivers, lakes and the sea, being a cause of diseases transmitted through water. For the society the costs of these diseases are much higher than the cost of the sewage treatment.

One of the most economical systems to treat sewage is the aerobic treatment system, reservoirs kept very oxygenated for aerobic bacteria to decompose organic material.
 
7. What is eutrophication?

Eutrophication is the process of excessive increasing of nutrients, like phosphate and nitrate, in water due to direct deposit of non treated sewage. The nutrients act as fertilizers leading to abnormal proliferation of aquatic algae. With the exaggerated growth of the alga population the number of aerobic bacteria that cause decomposition of organic material also increases. The proliferation of these bacteria depletes the dissolved oxygen killing fishes and other animals. Besides, the lack of oxygen causes the decomposition to be assumed by anaerobic bacteria. Anaerobes multiply and release hydrogen sulfide that makes water improper to other living beings and creates a putrid smell.
 
8. What is a biodigester?

A biodigester is equipment that produces carbon dioxide, hydrogen sulfide and fuel gases (biogases) like methane from organic material under decomposition (dung, food waste, sugar cane waste, etc.). The biogas is used in heating, as energy for motors and machines and it even has industrial uses. Biodigesters are widely used in public waste depositories and in rural areas. Besides producing biogas the organic waste can be turned into good quality fertilizer.

 9. What are the environmental harms caused by mercury pollution? What are the main sources of mercury pollution?

Mercury is a metal that when present in the water of rivers, lakes and seas contaminates fishes, crustaceans, molluscs and other living beings. The mercury accumulates along the food chain and in each following trophic level the amount of the metal within the individuals is higher. When humans eat contaminated animals they also become contaminated and severe nervous system injuries may emerge. The main sources of mercury pollution are gold mining and the use of derived substances in industry and agriculture.

10. Besides mercury which other heavy metals cause toxic pollution?

Examples of other heavy metals that cause toxic pollution are lead, cadmium and chromium.

11. What are persistent organic pollutants (POPs)?

POPs, or persistent organic pollutants, are toxic substances formed from organic compounds. POPs are made in several industrial processes, like the production of PVC, paper whitened by chlorine, herbicides, insecticides and fungicides, and also in the incineration of waste. Examples of POPs are dioxins, furanes, chlordane, DDT, dieldrin, heptachloride, toxaphen and hexachlorbenzene.

POPs are toxic and highly harmful since, like the heavy metals, they are bioaccumulative, i.e., they are not degraded by the body and accumulate even more in each following trophic level of the food chains. In humans POPs can cause cancer and nervous, immune and reproductive impairments.

 12. Is the upward move of warm air good or bad for the dispersion of pollutants?

The upward movement of warm air is a natural method of dispersion of pollutants. The air near the ground is hotter because the sun heats the soil and the soil heats the air nearby. Since it is less dense, the warm air tends to move towards higher and colder strata of the atmosphere. Such movement helps the dispersion of pollutants.

13. Does thermal inversion occur in the winter or in the summer?

Pollutant low altitude thermal inversion occurs in the winter. In this period of the year the sun heats the soil less and the natural upward move of warm air decreases. Therefore the pollutants form a low altitude layer between the cold air layer near the ground and another layer of warmer air above. The pollutant layer over industrial areas or big urban concentrations reduces the penetration of the sun's energy and the air bellow takes an even longer time to warm.

 
14. Why does thermal inversion increases air pollution? What harm can thermal inversion cause to humans?

Thermal inversion confines at low altitude a layer of pollutants that would have been dispersed by the natural upward move of warm air. The solid particles present in the atmosphere cause health problems, like the exacerbation of asthma and other pulmonary diseases, cough, respiratory unease and ocular discharges; later the pollution can also trigger the appearance of cardiovascular and neoplastic diseases.

15. What is the role of the ozone layer for living beings?

Ozone, O3, is a gas of the atmosphere that filters ultraviolet radiation from the sun disallowing most of that radiation from reaching the surface of the planet. Ultraviolet radiation is harmful for living beings because it is a mutagen and can cause cancer (mainly skin cancer), other DNA mutations and even burns.

16. What are the main chemical compounds that destroy the ozone layer?

The mains chemical compounds that destroy the ozone layer are the CFCs, chlorofluorocarbons, or freons, substances used in the past in refrigerators, airconditioners and spray cans.

Chlorofluorocarbons react with ozone in the high atmosphere releasing molecular oxygen and therefore the amount of ozone in the atmosphere is reduced.

Another substance that destroys the ozone layer is methyl bromide, used in agricultural insecticides.

17. What is nuclear pollution?

Nuclear pollution consists of radiations emitted from atomic nuclei, these radiations are highly injurious to living beings. They can be originated from the extraction of radioactive minerals, nuclear plant reactors, nuclear research centers, hospitals and medical centers that use radioisotopes, nuclear bomb explosions or accidents with transportation, handling or storage of nuclear material. Nuclear materials remain dangerous for many years, contaminating the environment with radiation that can cause cancer, immune impairment, congenital deficiencies, burns and even death. The damage is proportional to the intensity of the exposition to the radiation.

Its persistent feature and high aggression power make nuclear pollution one of the major environmental problems of our time.

18. What is plutonium reprocessing? Why is it a big environmental issue?

Plutonium is the highly radioactive chemical element produced from uranium by nuclear plants. Plutonium can be reprocessed to be used again in nuclear plants or in other destinations, like the making of nuclear bombs. Plutonium reprocessing nowadays, however, is done only in some countries like France, Russia and Britain. The countries that have nuclear plants, like Japan, Australia, etc., send their atomic waste by ship to those plutonium reprocessing centers. Besides the inherent risks of the storage of nuclear waste, plutonium reprocessing brings the risks of the transport of radioactive material across the oceans. The “nuclear ships” often travel near the coast of many countries posing danger to their populations.

 19. What is transgenic food?

Transgenic beings are animals, microorganisms and plants that contain recombinant DNA, i.e., genes from other plants, microorganisms or animals artificially inserted into their genetic material. Transgenic beings are made for scientific and economic purposes, in this last case with the intention of improving their commercial features. For example, bacteria that produce human insulin are transgenic beings made by biotechnology. The main targets of the transgenic technology are edible vegetables, like soy, corn, potato and tomato.

 20. Why are transgenics considered a threat to the environmental safety?

Transgenics can be dangerous to the entire biosphere since the transfer of genes between species may have immediate and long term unpredictable consequences. The creation of new species by nature is a slow process, dependent on causal mutations and natural selection, a relatively safe process for the ecological equilibrium. It is impossible to know how the fast and artificial introduction of transgenic beings in nature affects ecosystems. Pathogenic agents may be involuntarily created in laboratories, spreading unknown diseases; transgenic species may uncontrollably proliferate destroying ecological interactions that have taken thousands of years to be established; the ingestion of transgenic food also has unpredictable effects.

21. What is biological control?

Biological control is a natural method to control the size of animal, microorganism or plant populations. Biological control is based on the knowledge of inharmonious (negative) ecological interactions between species. Using such knowledge a parasite, competitor or predator species is introduced in an ecosystem in order to attain reduction of the population of another species with which it has inharmonious ecological interaction. The biological control presents the advantage of substituting the use of pesticides and other toxic chemical products in the control of plagues and diseases. It however should be employed with caution under serious previous study to avoid harmful ecological disequilibrium.

A kind of biological control of some species can be done by the introduction of previously sterilized males, that do not generate offspring.

22. What is bioremediation?

Bioremediation is the use of microorganisms, like bacteria, protists and fungi, to degrade noxious substances turning them into non toxic or less toxic substances. Bioremediation employs microorganisms whose metabolism uses contaminants as reagents.

Bioremediation is used, for example, in the decontamination of environments polluted by oil spills. In this process bacteria that use hydrocarbons as substrate for their cellular respiration are employed.

 23. What is global warming?

Global warming is the increase in the temperature of the planet due to accumulation of some gases in the atmosphere, especially gases that retain the solar energy reflected by the planet surface. The main gas that causes the global warming is carbon dioxide, CO2, but other gases act as “warming gases” too, like methane, CH4, and nitrous oxide, N2O. The exaggerated increase of carbon dioxide in the atmosphere has been caused by the burning of fossil fuels (mainly oil and coal) in industrial and urban societies and by forest fires. (It is important to note that the natural warming provided by gases of the atmosphere is fundamental for the maintenance of the planet temperature.)

Predictions of studies sponsored by the United Nations stated that the global warming may cause life-threatening transformations to the planet in the near future. Countries that are the biggest emitters of carbon dioxide, like the United States and China, however, systematically ignore the warnings and continue to largely contribute to the danger.

Global warming is one of the most polemic environmental issues today.

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