|
Читайте также: |
Medvedsky V.A.
Medvedskaya T.V.
Kartunova A.I
Bechara M.
Ecological Aspects of the Atmospheric Air Protection
Beirut 2005
UDK619:613.31
Authors: Medvedsky V.A., Doctor Agri.sci., professor
(Vitebsk State Academy of Veterinary Medicine)
Medvedskaya T.V., PhDVet. Sci., associate professor
(Vitebsk State Academy of Veterinary Medicine)
Kartunova A.I., senior lecturer
(Vitebsk State Academy of Veterinary Medicine)
Bechara M., (Beirut, Lebanese Republic)
Reviewer: Habib Nabil F., PhD Agri.Sci., Lebanese University, Lebanese Republic
Scientific- practical issue
Ecological Aspects of the Atmospheric Air Protection
A current view on the problem of air pollution is considered in the work. Acid rain formation and its impact on wildlife is featured. A special attention is given to laws regulating the atmospheric air protection. The work is intended for scientific workers, students of biological and agricultural faculties, ecologists, zoohygienists and all interested.
The work is considered and recommended for publication by Lebanese University, Beirut, January 10, 2005, protocol №1.
© Beirut, 2005
Contents
| 1. | INTRODUCTION…………………………………… | |
| 2. | Sources of the Atmospheric Air Pollution……………….. | |
| 3. | What is Asid Rain, What causes it, its harmful impacts | |
| 4. | Asid Rains as the Cause of Forest Degradation and Worsening of Ecological Status of Water Sources… | |
| 5. | Wildlife Impact of Acid Rain……… | |
| 6. | Doing a bit for prevention of acid rain ………… | |
| 7. | Acid rains in Europe …………………………….. | |
| 8. | Acid Depositions in Canada and British Columbia…… | |
| 9. | Industrial Emission Control…………………………… | |
| 10. | Primary Sources for Acid Depositions …………… | |
| 11. | Transboundary Pollution …………………………… | |
| 12. | Vehicle Emissions Control | |
| 13. | Measures for Prevention and Reduction of the Air Pollution... | |
| 14. | Monitoring of the Environment ………………………. | |
| 15. | Legislation Security of the Atmospheric Air……………. | |
| 16. | Ecological Law ……………………………………. | |
| 17. | Ecological Expertise ……………………………… | |
| 18. | State Surveillance of the Environment …………… | |
| 19. | Rights and Duties of Citizens and State Bodies in the Sprere of Environmental Protection. | |
| 20. | Legislation…………………………………. | |
| 21. | Arbitration………………………………………………… | |
| 22. | International Cooperation ………………………………... | |
| 23. | Acid Rain. Experiments……………………………….. | |
| 24. | References ……………………………………… | |
Introduction
There is no life existing on the Earth without the atmospheric air. Organism can not perform long its living functions in the absence of air.
Air environment is important not only for breathing of humans, animals and plants but it also serves as a reservoir perceiving gaseous products of their metabolism. Air environment allows humans and animals to perform their orientation, to perceive various signals by organs of sense perception to respond to environmental changes.
Air environment has its impact on multiple energetic, geological and hydrological processes, taking place all over the face of the Earth.The state of air depends to a great extent upon the quantity and quality of the solar radiation at the Earth’s surface.
The atmosphere is a place where precipitation is formed and along with winds contributes to mechanic destruction of rocks. Besides, the atmosphere is a climate forming factor. Through the air body performs its thermal exchange with the environment. The atmosphere also makes a source for some raw materials a stock of which is practically limitless: nitrogen, oxygen, argon and helium are extracted from air. Abrupt changes in chemical and physical properties of the air environment, its pollution with toxic agents and pathogenic microorganisms can bring about unfavourable processes developing in the body, threatening its health and well being. That’s why before agricultural specialists there set a task of developing measures for sanitation of the air environment in order to protect organisms from unfavourable changes related to environmental conditions.
The globe is surrounded by a gaseous envelope (the atmosphere) the omposition of which varies depending on the distance from the Earth’s surface.
The atmosphere includes the following layers: the troposphere, the stratosphere, the mesosphere, the ionosphere, the exosphere and the magnetosphere. The thickest air layers located closely to the Earth’s surface are called the troposphere. Thickness of the troposphere varies over different latitudes of the globe and in different seasons: over medium latitudes it makes 10-12 km above the sea level, on the poles it makes 7-10 km and over the equator - 16-18 km.
The troposphere is separated from the cold stratosphere by a thin layer – the tropopause - which at altitudes some 40 km turns into the mesosphere.
The mesosphere contains nearly 5% of the whole atmosphere.
Above the mesosphere there located the ionosphere, boundaries of which change depending on the time of the day and the season.. The upper border of the ionosphere varies from 500 to 1000 km. In the ionosphere air is highly ionized,
the ionization degree of the air masses and temperature being higher with higher altitude.
The atmospheric layer located above the ionosphere is called the exosphere. Its lover border changes depending on the time of the day, a season and a latitude and is located within 500-1000 km from the Earth’s surface. Actually in the exosphere moving gaseous particles do not collide.
Rarefaction in the magnetosphere is greater, there is a high degree of gas ionization here.
Physical status of the atmosphere at the given site for a short period of time is called the weather. The weather is characterized by a certain complex of meteorological factors: the intensity of solar insolation, the electrical status of the atmosphere, temperature, moisture, air pressure, velocity and direction of the wind, presence of the atmospheric precipitation.
It should be noticed that in the process of human activity the atmospheric air is a subject to everyday pollution. Acid rains are especially dangerous for living things.
Sources of the Atmospheric Air Pollution.
Under unfavourable metereological conditions a concentration of flue gases in the atmosphere increases and results in formation of a thick toxic midst. The disastrous cases are known when the accumulation of toxic substances was followed by severe diseases and the lethal outcome.
For example, in Los Angeles, on the south of California, in Great Britain, Germany and other countries the thickest fog with a high concentration of harmful mixture containing dust and gases – a smog, was noticed several times. In January 1956 such kind of a smog hanging over London during 96 hours took away lives of about a thousand of citizens.
Dust- gaseous industrial emissions comprise some 140 harmful substances. Many of them posessing no colour or smell sometimes can be invisible, insensible, showing no immediate effect upon organism. All possible organic dissolvents, aldehydes, other substances can be mentioned here.
Air pollutants can cause general fatigue, lowering of working capacity, coughing, giddiness, spasm of vocal cords, various pulmonar and eye disorders, general intoxication of the organism, lowering of body resistance to diseases.
Industrial emissions, combustion gases, soot, smoke, dust in the air of large cities form a kind of a cowl and less ultraviolet rays are possible to get in.
For example in Paris suburbs where there are no industrial enterprises ultraviolet rays constitute about 3% of radiation, and in the regions with plants and factories – 0.3%.
Lack of the ultraviolet radiation results in the development of rickets and avitaminosis in children.
The mutagenic, carcenogenic, allergic, aterosclerotic, embriotoxic effect of chemicals upon human organism has been marked including sexual mutations.
It has been stated that in regions where the intensity of pesticide application is 3-4, 9 times higher, the level of heart diseases increases 1.2 and 2.2 times. There is a direct correlation between the amount of plant protecting chemicals applied and a number of cases of the liver and bile tract disorders. In the future a significant increase of diseases resulting from the pesticide application, particularly the increase of spontaneous abortions as well as bronchitis, bronchial asthma, avitaminosis etc. is predicted. Cases of bronchitis, bronchial asthma, cardiovascular diseases to a great extent are connected with the atmospheric air pollution.
During recent years acute respiratory diseases of the upper air passages resulting in the development of bronchitis have increased.
Harmful mixtures in the atmosphere hold up the ultraviolet rays. Direct solar radiation is weakened in large cities. Pollution of the atmospheric air leads to changes in its electric characteristics, its ion composition. Observations made in some American states show that in all cities under consideration children suffered from primary and secondary pulmonar diseases more often than children living in areas with more clean air. This can be explained by the effect of sulfur dioxide upon human organism.
In all countries a number of people with emphysema of lungs is increasing, the same is true of allergic cases, all this being related mainly to industrial emissions. About 10 % of all human population is considered to be affected by allergens.
Cancer is spreading. This also to a great extent can be related to the fact that the atmospheric air contains carcinogenic, mutagenic and teratogenic reagents.
Polycyclic aromatic hydrocarbons are highly dangerous. There is a direct connection between air pollution with carcinogenic hydrocarbons and the degree of industrial development, transport intensity and the size of urban agglomerations.
In rural areas where the air is more clean cases of cancer are fewer than in large cities. Probability to acquire pulmonar cancer for a smoking city inhabitant is tenfold compared to a non-smoker living in the countryside. Air pollutants in urban areas poison the blood with hydrogen oxides and bring the same harm for a non-smoker as does a packet of cigarettes smoked up daily.
The atmospheric air pollution is toxic and can result in poisoning and the loss of animals, birds and insects. In a number of countries industrial emissions of fluorides were followed by mass losses of bees, sheep, cattle and poultry. A higher concentration of fluorine is responsible for early aging of teeth in animals and consequently, for gastrointestinal diseases and bone malformations. The autopsy of animals often reveals diseases of air passages and emphysema of lungs. The atmospheric pollution badly influences the fertility and productivity of animals, decreases the number of living insects, including bees, causes losses of fish in water bodies.
The air of industrial animal farms poorly equipped with cleaning facilities is intensively polluted. Such farm complexes with high concentration of animal stock in them are subject to heavy increase of ammonia, hydrogen sulfide and other compounds in the air inside and around livestock houses.
Zones of influence of industrial livestock complexes upon the atmospheric air environment have been defined as follows: for hog raising farms with 216 thousand heads – 4 km, with 54 thousand heads - 2.15 km, with 27 thousand heads - 1.5 km; for farms rising and finishing calves, keeping heifers up to 5 thousand heads –500 m, dairy farms with 800 or 1200 heads – 300 m; for beef producing farms with 1200 and 2000 heads - 500m.
Gross emission of air pollutants from organized sources only (ventilation system) on a large cattle breeding farm (10 thousand heads) calculated in terms of ammonia makes 57 kg daily, the total emission calculated in terms of organic matter makes more than 2000 kg daily. A hog breeding farm of industrial type with 108 thousand heads gives out daily 28 billion microbial bodies, some 50 kg of hydrogen sulfide, more than 600 kg of dust resulting from feeding staff and other compounds harmful for humans and animals. An industrial livestock production farm with 35 thousand heads of cattle or 108 thousand of hogs results in the air and water pollution equal to the same caused by a city with 400-500 thousand population.
In veterinary there are known cases of poisoning sheep and cattle by emissions of plants producing aluminium and containing a lot of fluorides.
Originating from the air these substances reach the grass concequently resulting in fluoriccachexia in grazing cattle. In Switzerland in areas close to such a plant one third of local cattle wasted away within 9 years.
Fluorides and arsenides contained in industrial emissions cause a high rate of bees losses. Arsenic intoxication provokes ulcers on a body surface in cattle.
In different countries worldwide losses of wild animals and fowls resulting from contamination of the atmosphere by sulfur dioxide, arsenic, antimony were noticed including the losses of deer, hares, roes, pheasants etc.
Contamination of the air by ammonia and high concentration of carbon dioxide inside animal houses renders negative effect on personnel and animals.
Such air pollutants as sulfur compounds, fluorine compounds, carbon oxide, chlorine and hydrocarbons are harmful for plants. They bring about significant damage to agricultural lands, forests, gardens and parks, interfering the process of photosynthesis, slowing down growth and development of plants, which then gradually weaken and waste away. It has been stated that even negligible doses of anhydride sulfide bear their negative influence upon plants. Of all cereals barley and oats are the most sensitive to this gas. Spinach, cabbage, lettuce, radish can be mentioned among vegetables. As the result of pollution of the atmosphere there is a significant decline marked in the yield of such crops as potato, sugar beet, tomato, beans, tobacco, peanuts, Soya, alfalfa, grapes, orange etc. In a number of horticultural plants under the influence of severe gas-pollution of the air leaves shrink, fall down early, which in combination with metabolic disorders is followed by the retardation of vegetative growth of stems, malformation of fruit and worsening of their quality.
According to data of research institutions in the area of active non –ferrous metal plants the yield of wheat decreases to 40-45%. The content of protein in a grain decreases to 25-35%, and the amount of starch grows. Within the radius of 25-50 km around such enterprises the content of vitamin C in potato and other vegetables dramatically drops.
Around industrial enterprises emitting sulfur, fluoride and arsenic compounds forest are markedly depressed, and a part of trees get dried out even if situated at a far distance from the source of pollution. Coniferous trees are species most suffering from the effect of industrial gases. The photosynthesis runs more effectively in those plants where dust and soot were cleaned and wached out from leaves (4.155-4.372 g/m2). In trees where leaves were not preliminary cleaned and washed with water the productivity of photosynthesis made only 3.022-3.245 g/m2, i.e. it reduced to about 25%.
It has been stated that every square meter of foliage surface daily holds on 95-129 mg of dust and soot resulting from industrial source of wastes located within a distance of 350 m. Afterwards this dust and soot are washed out by raining.
In many urban industrial territories and areas along highways the concentration of sulfuric gas, nitrogen dioxide, hydrogen oxide and dust overcomes the maximal permissible level (calculated per person) and becomes threatening for human health.
Such amount of gases, especially SО2 and dust is even more harmful for vegetation: the maximal one-time permissible dose of the air pollution for sulfur dioxide is less than 0.02 mg/m3, for nitrogen oxides- 0.05, for ammonia- 0.1mg/m3. Hence, the SО2 toxicity is 25 times higher compared to norms (for humans 0.5 mg/m3 of air).
As a rule, the effect of most air-born pollutants is limited by regions adjacent to sources of their origin. The usual distance where the effect of the air polluting source is felt makes 30-50 km. However, there are air pollutants capable to spread their influence to even further distances. For example, chimneys and stacks of power stations burning fossil fuel and furnaces often disperse sulphur oxides onto long distances, without any consideration to boundaries. Finally reaching the Earth’s surface in the form of particles or acid rains such pollutants play their damaging role acidifying natural water sources, promoting the depression of forests.
Another pollutant - carbon dioxide is a normal component of the Earth atmosphere, it knows no national boundaries also. Carbon dioxide is formed in the process of burning fossil fuel and woods. As the result, the content of carbon dioxide in the atmosphere is constantly gradually growing at the global scale. Being of no direct harm to plants and animals even today when its content in the atmosphere is high, however, carbon dioxide acts as a barrier for dispersion of a thermal radiation from the Earth’s surface in the cosmic space. That is why the future generations will probably face the global warming of climate on the Earth.
What is Acid Rain, What Causes it, its Harmful Impacts?
A complex range of impacts on wildlife and humans of technogenic pollution is meant under a widely used term acid rain. Its main consequences being as follows: a growth of allergic problems for respiratory system in man and animals, a loss of yields in agriculture, wasting away of forests, getting free from fish in lakes.and rivers.
The acid rain problem appeared in Western Europe and North America in the late 50th. During recent decade it acquired its global significance mainly in connection with an increased level of sulphur and nitrogen oxides emission as well as ammonia and volatile organic compounds. According to data of EEC, sulphur dioxide (trioxide) comes from thermal electric power stations and other stationary sources burning fossil fuels (88%), processing sulphide ores (5%), oil refinery and production of sulfuric acid etc. are responcible for (7%).
Energy production and fossil fuels burning makes 85% of pollutant emission; the manufacturing of cement, lime, glass, metallurgic processes, wastes burning etc. are responsible for 12%. Nitrogen pollutants come from non standard sources, ammonia comes from livestock enterprises and fertilizers. The majour sources of volatile organic compounds are chemical industrial enterprises, industrial and home dissolvents, oil refinery enterprises, gas stations etc.
Apart from these primary pollutants, the atmospheric air contains a number of secondary ones - ozone and other photochemical oxidants, nitric acid, sulphuric acid etc.Ozone, the content of which in the atmosphere close to the Earth grew twice within last decades makes the principal part of the photochemical smog in urban areas where the air is polluted with exhaust gases. Ozone destroys the lung tissue and brings about tumour processes, though at the same time it protects against UV rays compensating lessening of the ozone layer in the stratosphere.
Primary and secondary oxidants together define a “pollutant” climate, which depends on a common climate changing it at the same time. It should be emphasized that an effect of each pollutant on natural ecosystems and humans is dependent on the “pollutant “ climate as a system.
The state of such system depends upon constantly lasting reactions between pollutants of different origin and hydroxide radicals, and between themselves at a gas phase, on aerosols, on leaves surfaces. At that, their effects can either be neutralized or mutually strengthened, as in the case when sulfur dioxide and ammonia fall out together.
Oxidants are absorbed by soil and biota from the atmospheric air, acid rains and fog droplets containing two, three times more sulphur and nitrogen than rains.
The first economically felt consequence of acid rains was a loss of fish sources: hundreds of lakes in Scandinavia and British Isles became fishless. Among factors influencing fish populations in connection with acidifying we can mention a lack of calciun, aluminium precipitation on gills and, mainly, disorders in reproduction. Also sensitive to acidifying are amphibians, crustaceans, mayfly larvae etc., whose reduction in biomass influences the population of water fowl.
Acidifying of water pools takes place due to the washing out anions of sulphuric and nitric acids from the soil – the main accumulator of acidic pollutants. Soil acidifying leads to changes of Al/Ca and Al/Mg ratio, which grew nearly twice within recent twenty years. However, soil capacity related to acid pollutants is based on their mineral composition, their cation exchange, soil respiration and other factors depending in their turn on a geological substrate, climate and vegetation.
There are several estimating models for soil acidity and its cartographic analysis, in a number of cases revealing a very high correlation degree with a geological substrate.
Soils of Northern Europe formed relatively recently, in the period when glaciers had moved away, posses less pollutant capacity compared to old soils, enriched with iron and aluminum.
Soil acidifying is considered to be one of the main causes of drying off the forests of moderate zone in northern hemisphere. In a threatening scale forest
depression manifested itself in the early 70s. Most suffering appeared to be spruce-fir and oak forest. In European countries defoliation some 25% is marked in 15% of trees older than 60 years. The damage caused to old trees dominates. Acidifying effects can be subdivided into a chemical and a biological ones. The first one involves mainly changes in the cation exchange of a plant, as the result trees experience the Mg deficiency (especially in soils naturally poor in Mg) and an excess of aluminum which is seen as a principal reason for needles turning yellow. Another effect is rather diversified and is in most parts bears indirect character: pollutants act as a starting mechanisms of both biological and chemical processes, depressing a plant, reducing its resistance to pests and climatic influence. In particular, acid medium depresses the development of mycorisaand root growth. At the same time, the increased amount of nitrogen and free nucleic acids stimulates the development of forest vermin. Indirect effect is manifested in prolongation of the summer growth and consequently, the increased sensitivity to first frosts. Genetic changes can be also attributed here as the result of natural selection for resistance to acidic pollution.
Soil effects are accompanied by the direct influence of ozone and other gases on the assimilative apparatus in leaves. It is shown, for example, that ozone changes the microstructure of a wax covering in a fir needle which obstructs up to 80% of stomata. This effect inflicts a great damage on agricultural crops, less depending on acidifying of soils and being under control of agrochemicals. One of the yield- reducing factor is a chemical change in the medium where the biochemical reactions between secretion of a stigma and pollen take place, the efficiency of pollination is dependent on this medium.
It has been estimated that a 25% reduction of ozone concentration would give an increase of cereals yield in the USA in the sum of 2-3 billiard dollars, which makes 2-3 % of all agricultural production costs.
For forests, however, soil pollution appears to be more essential and long lasting factor manifesting itself many years later after the emission was reduced (soil becoming a source of acid gases). A damage caused by acid rains to European forests is estimated as 118 million cubic meters of timber per year (from which about 35 million cubic meters are damaged on the European part of Russia).
Though the effect of pollution has been localized both relating to their sources and to the sensitivity of ecosystems the drying off of forests still occurs at the same time in different countries worldwide revealing the climatic component of the phenomenon. In spite of some disagreements existing among specialists concerning the leading role of a climatic or “pollution” factor, most of them, however, agree that in dry years the damage from acidic pollution increases.
As a positive feedback soils give off nitrogen dioxide – a hot house gas- and absorb less methane. In this case a natural climate and “pollution” one are so closely
connected that, actually, they can hardly be separated. For confined lakes a neutralizing potential of ground waters is of a decisive role. Climatically conditioned fluctuations of the ground water level bring about the appropriate changes of pH, the level of pollution remaining constant.
Before high chimneys and stacks were considered as a means against air pollution. But when a long distance transfer of gaseous pollutants became obvious, it also became clear that a “high chimney” policy aggravates the global effect of gaseous emissions. The problem of a long distance transfer found its reflection in a Memorandum of USA/Canada and the European Convention on a long distance transboundary air pollution. These international agreements initiated a number of research programmes in order to determine the minimal “critical loads” for sulfur and nitrogen in ecosystems.
Planned for the EC countries reduction of sulphur emission to 60% by 1998 according to a preliminary model estimation is not enough for the return to a pre-industrial level of acidity, however, a partial restoration of lakes and forests ecosystems is being marked nowadays. Unfortunately, today this problem is paid less attention to, as a struggle against the “hotbed “effect becomes of primary importance.
Acid rain is a broad term used to describe all forms of acid precipitation (rain, snow, hail, fog etc.). Although we associate the acid threat with rainy days, acid deposition occurs at any weather, even on sunny days. When atmospheric pollutants such as sulfur dioxide and nitrogen oxides mix with water vapor in the air, they are converted to sulfuric and nitric acids. These acids make the rain acidic. Rain returns the sulfur and nitrogen acids to the Earth, and in high concentrations it can cause a damage to natural environments including forests and freshwater lakes. This form of acid deposition is known as wet deposition. Another method of acid deposition is known as dry deposition. Gases present in acid deposition are found to occur naturally in the environment. Sulfur dioxide, for example, is deposited as a gas or as a salt.
Acid deposition can form as a result of two processes.
More than 90 % of the sulfur in the atmosphere is of human origin. The main sources of sulfur and nitrogen include:
Coal burning. Coal typically contains 2-3 % sulfur, so when it is burned sulfur dioxide is liberated.
The smelting of metal sulfide ores to obtain the pure metals. Metals such as zinc, nickel and copper are commonly obtained in this manner.
Volcanic eruption. Although this is not a wide spread problem, a volcanic eruption can add a lot of sulfur to the atmosphere in the region.
Organic decay.
SO2+ H2O >>> H2SO3
SO2 +1/2O2>>>SO3+ H2SO4
Acids of nitrogen form as a result of the following atmospheric chemical reactions:
NO + 1/2O2>>> NO2
2NO2+H2O>>> HNO2+ HNO3
NO2 + OH>>>HNO3
Acid rains (rain, fog, snow) are deposition with acidity above a normal level. The pH scale is used to measure the acidity of acid rain which is determined by the hydrogen ion content (H+). The pH scale ranges from 0, which is strongly acid, to 14 which is strongly alkaline, the scale 7 being neutral (pure water).
Rain water in a clean air has pH 5.6. the lower pH - the higher acidity. If the water pH lower 5.5 then deposition is considered acidic.
On vast territories of industrially developed countries worldwide deposition falls out with the acidity 10-1000 times exceeding the normal one (pH 5-2.5).
A major release of sulfur ur into the atmosphere is caused by burning fossil fuel. It has been estimated that 42 million tons of sulfur released into the atmosphere worldwide are originated by burning of solid fuels and 18 million tons – by liquid and gaseous. Besides, production and processing of ferrous and nonferrous metals release 10 million tons of sulfur more. All this serves as a sources for 70 million tons of sulfur released into the atmosphere annually. The worldwide production and use of sulfur containing raw materials of all kinds constitute nowadays 52 million tons.
It should be mentioned that out of 42 million tons of sulfur released by burning solid fuels, mainly coals, all over the world 11-15 million tons come from CIS countries where brown coals rich in sulfur are mainly burned. Its content in coals of Podmoskovny and Kizelovsky region (Russia) makes 6%, in Irkutsk- 8-10%. The total sourses of coal in CIS countries estimated as 1450 billion tons, brown coals make 846 billion tons or 58%.Coal burning is the largest source of technogenic emissions of sulfurous compounds into the atmosphere in Russia and all over the world.
Burning of gaseous and liquid fuels release essentially less sulfur into the atmosphere.
Though the development of gaseous industry is sustained, gaseous fuel burning causes comparatively low release of sulfur, because a preliminary purification from harmful hydrogen sulfide became a must, significant volumes of a high quality regenerated sulphur being produced as a result.
In 80s the production of regenerated sulfur took the first place in the world and still has the tendency to further growing. Significantly less less but also important amount of sulfur comes from a liquid hydrocarbon fuel. Oils containing more than 2 and 0.5-2% sulfur correspondingly should be also mentioned as a substantial part of
its total sources and production.
In a number of countries (USA, Japan) oil purification accompanied by the production of regenerated sulfur has reached a signifucant scale. However, in many countries the extraction of sulfur from oil is at a low level. Russia belongs here. The major volume of oils produced here is low in sulfur but there are also oils with a high and medium sulfur content. A major part of such oils comes into use without sulfur purification and tnen a significant amount of sulfur is released into the atmosphere.
A total amount of sulfur originating from fuel gases and oil increases in the world. At present it makes more than a half of the whole world sulfur production from all kinds of sulfur containing raw materials. Production of nonferrous metals from sulfide ores and concentrates develops rapidly, significant amount of sulfurous gases being released. With a certain SO2 concentration in them (more 3-5%) they are oxidized to SO3 and sulfuric acid is produced. Unfortunately it is not a common practice everywhere.
The problem of sulfur utilization is rather complicated and is partially solved some in countries of the Western Europe. In Germany, for example, one third of sulfuric acid is produced from gases originating in production of nonferrous metals.
In ferrous metallurgy ores are agglomerated, sulfur is oxidized and releases as SO2, but with a low sulfur concentration (0.5-1.5%), which does not allow it to be completely utilized and increases the release of sulfur into the atmosphere. Total amount of sulfurous compounds released into the atmosphere is signifiant, in Russia also. Thus, in Norilsk, for example, annual emission of SO2 overcomes 1 million tons.
The greatest amount of sulfur is emitted into the atmosphere as a result of fossil fuels burning at power producing stations. Concentrations of sulfurous anhydride in released gases are very low (0.5-1v.%) which makes them difficult to be “captured”. To reduce the amount of sulfur emitted investigations are carried out and new technologies are being developed world wide including the pre-combustion sulfur control. Coal and oil burning power stations are equipped with special treatment equipment, new technologies are developed for ecologically clean burning of fossil fuels, it is very important to remove sulfur from fossil fuels before burning. For this, at the International Coal Preparation Congress a lot of methods were suggested e.g.: flotation of coal and hydrophobic pyrites with subsequent separation.
The method of electronic treatment of coal with the purpose to increase the magnetic sensitivity of pyrites with consequent removal by magnetic separation was suggested. In the USA investigations are carried out on the use of perchlorethylene at high temperatures, which allows nearly full removal of pyrites and about 70% of organic sulfur.
Researches and practical measures for purification of fuel gases from sulfurous compounds are also carried out in Russia. A liming method has been developed by which the releasing sulphur is converted in the form of potassium sulfite into slurry. But this method can not be applicable if SO2 concentration is more than 0.12%. A big stock of slurry accumulating on a large power station makes then a real problem for its removal.
Promising is the method when SO2 is bound with magnesit milk, and crystalline magnesium sulfite is formed, then dried off and burned in furnaces KS. Releasing 12-15% sulfurous gas comes to sulfuric acid plants and magnesium oxide is returned to production process.
Dry methods for smoke gases cleaning are developed and come into use in several places. Here activated carbon, aluminium alkaline oxide, catalysts are used, but these methods are not economic.
Released into the atmosphere sulfurous and other pollutants are able to travel long distances carried by air currents. E.g. emissions produced in Germany or Great Britain travel to Scandinavian countries. The UN Organization expertise has found that many dozen tons of sulfur emitted in the USA and Canada get entry into the atmosphere of Europe. It’s remarkable that West – East directed air currents transfer 4 times more sulfur than in the opposite direction. Emission of technogenic sulfur is steadily growing: during the second half of a century they doubled and are still growing quickly.
All said above proves exclusively negative ecological effect of sulfur emission especially in fluegases. However, we can be sure that collaborative researhes of scientists world wide will solve the problem of clean air. Industrials involved in sulfur emission are ready to pay for sulfur utilization, the amount of sulfur contained in flue gases is great and its utilization will make a powerful source of useful raw materials.
Sulfur from natural sources of mainly of volcanic origin enters the atmosphere also. Total emission in the form of ashes, volatile compounds is estimated as 29.3 million tons per year. From this only a small quantity is absorbed by oceans (1.3 million tons), and there are no perspectives to reduce this amount.
Natural and man-made sulfur released into the atmosphere contacts with the atmospheric moisture and forms though a weak but chemically very active acid which with acid deposition is returned on the ground surface. In industrial areas acid rains are 5-30 times more aggressive. Acid depositions affect most materials to some degree. Materials most vulnerable for acid rains include: nickel, steel, copper, metallic roofs etc. They cause structural damage for undeground pipes, cables and foundations submerged in acid waters. They effect limestone, marble causing severe damage to buildings, historic monuments. Acid rains acidify fresh waters, leading to losses of fish population and other aquatic species. They reduce human resistance to respiratory and other disorders.
Acid deposition acidifies soils, significantly lowering their fertility and yields; they are damaging soil biomass. Trees are suffering from acid depositions, especially susceptible are spruce, pine, and they are killing for roses.
It is well known that soils with a high level of acidity are low productive, such soils are plentiful in Russia. To cope with this liming is a common practice here. Annually up to 100 million tons of lime powder are applied but soil acidity even growing. The explanation is that the effect of acid rain prevails liming. This caused doubled agricultural losses on acid soils in late 90s.
All said above proves the necessity to take wide measures promoting a signficant decrease of emission of the technogenous sulfur into the atmosphere both on the territory of Belarus and all over the world.
We do hope that by common efforts the increase of the atmospheric air pollution by sulfur compounds will be stopped and possibilities will be found to eliminate this rather serious ecological problem.
According to data of the European programme of monitoring and assesment for long distances transboundary air pollution, by the beginning of 1998 oxidized sulfur fall outs are estimated as 1695 000 tons per year, oxidized nitrogen –666 000 tons per year, recovered nitrogen- 891 000 ton per year. In 1997 compared to 1991 the transboundary loads of oxidized sulfhur made a 6 % decrease, the same of oxidized nitrogen – 5%, and for recovered nitrogen there is an increase of 23 %. 5%.
In 1997 a part of acidifying fall outs from own sources for Russia in their common fall outs on ETP made for sulpfur oxides 32%, for nitrogen oxides –31%, for recovered nitrogen – 52%. At these fall outs from internal sources in 1997 as compared with 1991 were reduced for sulfur oxides to 33%, for nitrogen oxides to 17%, for recovered nitrogen - to 16%. This decrease took place, mainly, due to the reduction of produced volumes and the reduction of emission.
The most important contribution to the transboundary air pollution was made by Belarus, Germany, Poland, Ukraine, Finland, Estonia (1997, thousand of tons on ETP.) (Table 1)
Table 1
Contries most contributing to the air pollution on ЕТР (thousand tons.).
| pollutant | Oxidized Sulfur | Oxidized Nitrogen | Recovered Nitrogen |
| Belarus | |||
| Germany | |||
| Poland | |||
| Ukraine | |||
| Finland | - | - | |
| Estonia | - | - |
In the exchange with other countries participating in the Convention EEK UN on long distances transboundary air pollution the “ positive” balance of fall outs for acidifying pollutants in Russia in 1997 belonged only to oxidized sulfur and only for three Northern countries – Norway, Finland, Sweden.
Comparing to 1991 the absolute meanings of oxidized sulfur loads from the Russian sources on the territory of Norway decreased to 23 %,in Finland- 33%, Sweden- 19%. With all other counties Russia had a “negative” balance in exchange of oxidized sulfur, oxidized nitrogen and recovered nitrogen loads.
“ Acid rain” is a broad term used to describe several ways that acids fall out of the atmosphere. Acid rain is a serious environmental problem that affects large part of globe.
In the US, About 2/3 of all SO2 and 1/4 of all NO2 comes from electric power generation that relies on burning fossil fuels like coal.
The term acid rain was first used by Robert Angus Smith, a scientist working in Manchester in the 1870s. Thus, the problem of acid rain is not a new one, but the nature of the problem has changed from being a local problem for towns and cities it turned into to an international problem.. In Smith’s time acid rain fell out in towns and cities, whilst today pollutants can be transported thousands of kilometers due to the introduction of tall chimneys dispersing pollutants very high into the atmosphere.
In the 1970s and 1980s, Scandinavian countries began to notice the effects of acid deposition on trees and freshwaters. Much of the pollution causing this damage was identified as being transported from other more polluting countries. Acid rain became an international concern.
Rainfall with pH 4 is 100 times more acidic than pH 6 and rainfall with pH 3 is 1000 times more acidic than pH 6.
Acid rain became particularly prominent as a media issue during the 1980s. However, during the 1970s many countries started to notice changes in fish populations in lakes and damage to certain trees. By the late 1970s concern led to international efforts to identify the causes and effects of long-range (transboundary) transport of air pollutants, and thus during the 1980s much research was conducted in Europe and North America.
International legislation adopted during the 1980s and 1990s has led to reduction in sulfur dioxide emission in many countries, but reduction in emission for nitrogen oxides was significantly lower.
Acid Rains as the Cause of Forest Degradation and Worsening of Ecological Status of Water Sources.
The term forest degradation has two meanings. It can mean just the retardation of growth in trees, which is manifested in the reduction of the width of a tree annual rings. Formally it sounds as “ the reduction of forest productivity”. If a non specialist looks at such a forest he would hardly be able to recognize what happened. A biologist would notice the signes of decrease in productivity.
Another meaning of the term forest degradation - is a real damage of trees or even their death. Such symptoms could hardly be neglected.
Artur Jackson from the Pensilvania University investigated the thickness of annual rings in a red spruce, a fragile pine (north-east of the country, south of New Jersey) in order to define if the forest productivity really decreases. From 30 up to 40 % of cuts investigated revealed an unpleasant picture. Starting from 1960th, the width of annual rings, in other words- annual growth rate, significantly reduced, and in many trees the former growth rate did not renew. The same was revealed true for leaves falling trees – gicory and a yellow birch.
In Schwarzwald (Germany) damage was marked not only in coniferous trees but also in oaks, birches, rowan trees, beeches and platans. The scale of damage affecting trees of so multiple species both leaves falling and evergreen- turned to be unprecedented. No one could explain what happened to such a big amount of trees. The majority of scientists explained this as the impact of acid rains and the air pollution but this explanation did not prove sufficient. It is agreed that acid rains and air pollution have played their role, but other factors such as a drought, in particular, could also interfere.
If observed factors only influenced forest productivity, people would hardly pay much attention to this problem. But forests started dying away. In Schwarzwald every fifth tree was moderately damaged: there appeared more serious signs of damaging in every two trees out of every three, and ill trees were met on the territory covering two thirds of all forest area. According to the assessment of 1984, three quarters of trees in Germany have already injures of various degrees. In Germany this phenomenon was called «Waldsterben» (literally – dying forests). This has been noticed on 50% of all forest area, which made 2.5 million hectares Forests in Bavaria are also seriously damaged. For instance, in a red spruce - as the most resistant to damage – the yellowing and early fall of needles have been noticed. Needles falling starts from the top of the tree and then gradually spreads downwards. Besides, the process of falling needles starts from the tips of branches, and the process is directed towards the trunk. Fungi and insects settle downd under the cork of trees. In cells of cambium toxic metals accumulate in high concentrations, including aluminium, cadmium, copper and manganese.
Numerous reports from Chech Republic, where the brown coal with a high content of sulfur is intensively burnt, confirm a loss of the whole forest tracts. According to the obtained information trees on 200 000 hectares of forests are seriously damaged. One fifth of this territoty is covered by dead trees only.
In Poland, where the brown cooal is also used, tree damage is of greater range: damaged trees are found on 500 000 hectares of forest lands. Forest degradation has also been marked in Austria, Switherland, Sweden, the former Eastern Germany, Holland, Romania, Great Britain and the former Yugoslavia.On the south-west of Sweden every tenth tree is damaged or dying. In coniferous trees of Scania (a region in Sweden) needles are kept on a tree within a year only, and in healty young trees they change once every three years. Birches in Scania, as well as trees in the western part of Germany loose leafage in August when still green. The bark of birches bulges and crackles, cracklings reaching a palm size.
Similar damages of trees are marked in the USA also: in mountains Adirondack (New York), Green Mountains (Vermont), White Mountains (New Hampshire) and Great Mountains (in the east of Northern Carolina). A quick loss of red spruceis noticed in these forests, but the area of the perished forests yet has not been estimated quantitatively as it is made in Germany and other countries of Europe.
All described instances are characterized by certain features repeating once and again.
Firstly, acid rains cover all regions. Sulfur and nitrogen oxides are carried for long distances by winds and other atmospheric processes and then fall out in the form of acid rains or in the form of dry particles of metal sulfates.
Secondly, in most cases the damaged forests are located on highlands, relatively high above the sea level, and within rather a long period during a year they are wrapped up by clouds. This is unconditionally true for Shcwartzwald in Germany and Green Mountains in Vervont, USA where trees are surrounded by clouds for a quarter of a year. Water, forming clouds may have pH up to 3.5 and even lower, i.e. to be more acid than rain. This is a reason to say that it is the influence of a strongly acidic medium that ensures tree damage.
Thirdly, as a rule, drougths preceeded the periods of growth retardation in a tree yearly rings. If only droughts were responsible for depression of trees, then after improvements of weather conditions we could expect remissiom of normal growth. However, according to some researches the yearly rings renewal has been marked only in 20 % of trees and the rings growth never renewed in 40 % of trees.
Fourthly, common features are characteristic for soils. In forests located in high mountains there is a tendency to significant increase of soil acidity, because the thickness of the soil layer is very little, and it contains a negligible amount of organic matter. Such substanes which are very important for soil as calcium and magnesium carbonates are easily removed from the soil due to the abundance of hydrogen ions in the environment and losses resulting from washing out. These substances become unavailable for growing trees. At the same time acid rains can bring aluminium – toxic for plants and normally bound in various chemical compounds -“to mobilize” and acquire chemical activity. Active aluminium is capable of penetrating into rhizome and roots of trees interfering with their normal functioning.
Fifthly, a chemical analysis of leaves both from deciduous and coniferous trees shows that in comparison to healthy trees the sulfhur content in them is 10 % higher (at least in the USA).
Sixthly, analysis of mountain forests, especially in the south of USA and Europe shows a high content of ozone in the air. This content is higher than it was marked in lower locations, and even higher than the level fixed in some cities.
It has been known long ago that ozone damages evergreen plants, but the discovery of ozone in high concentrations on mountains slopes turned to be unexpected. We can not exclude that this can be explained by the presence of nitrogen oxides.
As we have already known, in the presence of sunlight nitrogen dioxide enters into the complicated chain of reactions with hydrocarbons forming ozone. But how do hydrocarbons appear in the mountain forests? Trees themselves can make the source of it. Gray Smoky Mountains are named so because a thin column of smoke excreted by coniferous trees.
Hydrocarbons are highly active substances. In the sunlight terpens may react with nitrogen dioxide producing ozone.
Thus, we face the number of factors: acid rains, high level above the sea and clouds coating trees; droughts preceeding the tree damage, the increase of soil acidity and changes of its mineral composition; sulfur in foliage, ozone in the atmosphere.
All these factors collectively produce the vision of the ecological catastrophe in the Northern hemisphere. First in Scandinavian countries, then in the north-east of the USA and in the south-east of Canada, later in northern Europe, Taiwan and Japan the rain water considered the purest water in nature was found to contain acid.
As we have already mentioned, sulfur dioxides produce more and more acid. Among all types of the used fuel, coal comes first to deliver sulfur oxides,oil is the second and natural gas takes the third place which is rather far from the first two.
Fossil fuels also result in formation of nitrogen oxides. But air itself is suspected as the source of their origin, because fossil fuels, as a rule, do not contain nitrogen in large quantities. Maximum emissions of nitrogen oxides into the atmosphere are the result of combustion process of all three types of fuels at high temperatures. Coal-fired power stations and steel industry mainly contribute to the production of sulfur dioxides. Nitrogen dioxides are also produced by power stations and industry but another major contributor for nitrogen dioxides is the vehicle emission.
The dispersal of flue gases from conventional power stations (together with pollutants) in the atmosphere by means of high chimneys and stacks allows sulfur and nitrogen oxides of such origin to be spread over long distances.
Whilst emission of these pollutants at a ground level is hardly possible to be spread by the winds blowing at high altitudes and to be transported at considerable distances, which is characteristic of acid rains.
Sulfur dioxide and nitrogen oxide in the atmosphere react quickly. Sulfur dioxide is transformed into sulfur trioxide which then dissolves in water drops producing sulfuric acid. Nitrogen oxide turns into nitrogen dioxide and dissolves in the water drops accompanied by the nitric acid formation. These two acids as well as their salts cause fallouts of acid rains. The higher is the content of these acids in the air the more often acid rain falls out.
Sulfuric and nitric acids unevenly contribute to formation of acid rains.
Nitrates (nitric acid) is responsible for about 15-30 % of acid rains in the north-east of USA, the remaining part being caused by sulphates.
In California, on the contrary, nitrates are the more abundant component of acid rains.
Data on measuring the acidity of rains in Pasadena showed that 57% of it are due to nutric acid and 43% are due to sulfuric acid.. The fact that rain acidity is brought about by nitric acid is explained by a heavy vehicle emission of nitrogen oxides in southern regions of California. Dry acid depositions from the air also fall down on plants and ground.. As a rule, these are sulfates of calcium and magnesium. Researches more and more apt to think that fall out of such dry depositions turn to be an important mechanism, by means of which acids from the air get down on the ground.
Rain water can not be called clear as it comes in contact with carbon dioxide – natural component of the atmosphere – and dissolves it. As the result of this dissolution a weak carbonic acid is formed. A concentration of hydrogen ions related to water molecules in clear rain water containing carbon dioxide will make about one millionths (10 –6) or 1 ion of hydrogen per 1 million of water molecules.
Thus, a concentration of hydrogen ions in rain water containing dissolved carbon dioxide from the air increases 10 times. Exactly this amount of hydrogen ions should be characteristic of pure rain water in natural conditions.
The most prominent is the impact of acid rains on fish population in lakes with waters becoming acidified. Acidification causes either a decline or loss in fish population.. In Sweden, Norway and the Eastern part of Nothern America industrial and sportive fishing has been badly influenced by water acidification.
In multiple lakes of AdirondaсkMountains (610 m.above the sea level and higher) acid water has become common. In 1975, 51% of lakes had pH < 5 and in
90 % of lakes there was no fish at all. On the whole, 45% of high mountain lakes contained no fish. In the 30s fishless lakes made only 4% of total amount. It has also been found out that one third of more than 2000 lakes in Nothern Norway are fish free. This change has occured since late 40s.
It is clear that acid water has a certain impact on a decline in fish population. However one should not think that adult fish simply dies in large quantities because of increased acidification of water in these lakes. More realistic looks an opinion that strongly acidified waters do not allow fish to reproduce normally.
Females might be not able to produce eggs in acid water, even if eggs happen to come into water they either die or produce juveniles which then die. As the result only adult individuals are met in lakes with acidified waters.
In many regions where fish population declined due to acid rains very cold winters with heavy snowfalls have been registered.
With snowmelts acidified water gets entry into nearest lakes which leads to a sharp increase of their acidity. Snow melting and a growth of acidity coincide in time with the beginning of spawning. Thus, fish eggs get entry into maximally acid water. We can presume, that with a decrease in fish population a decrease of fish eating animals will also take place, for example: white – headed sea eagle, loons, osprey as well as mink and otters.
Scientists predict that acid depositions will also cause a decline in population of frogs, toads and tritons.
Many of these species use for their reproduction temporary ponds arising in the period of spring rainfalls. Water in them may be even more acid than in lakes, as such temporary ponds are formed only by rain waters with higher acidity.
It should be noticed that population of such species declines not as the result of heavy losses in adult fish, but because young individuals do not fill the population.
Acid rains negatively influence not only animals but plants also. A change in variety of plant species is difficult to be noticed in sites of acid rainfalls, it takes rather a long period to reveal changes in a character of forest growing. To overcome these difficulties some experiments were carried out under laboratory conditions where water with pH corresponding to rain water pH in the north-east of the USA was used. The water was sprayed over pines and tomatoes in such a manner that allowed to imitate the entrance of natural water to the plants. In these experiments pine needles were just a half of normal length and the yield of tomatoes was significantly lower.
Scientists have not revealed a direct influence of acid rains on human health, but such a possibility exists, no doubt. This is connected with the higher ability of acidified water to dissolve or to influence various minerals in any other way.
Mercury contained in natural water sources may turn into poisonous monomethylmercury. Fish will accumulate this mercury compound in their tissues. High concentrations of mercury in fish tissues was noticed in the regions of acid rain- falls. It is well known that mercury is strongly poisonous for a human being. Human poisoning by fish contaminated with mercury has already taken place under other circumstances. If sources of drinking water become more acidified, then toxic metals from tubes, plugs etc. can be dissolved in it and get entry into water used by by human consumption. Besides, acidified drinking water is able to dissolve lead of water delivering systems. Such a precedent took place in the state of New-York.
Strongly acidified water from the Khinkly watersourse, next to Amsterdame (state of New-York) dissolved lead from watering tubes and the content of lead in drinking water exceeded the permissible level. This water was kept in tubes during the night and when let out, the concentration of lead dropped to customary low level.
Not all lakes become acidified. Such lakes or their basins are likely to be capable of neutralizing acid additives. Other lakes, judging by their present state, are really sensitive to acid rains. Water collecting basins of lakes, effected by acid rains, are embedded either on igneous rocks (e.g.granite) or methamorphic (e.g.gneiss) rocks. These rocks are resistent to dissolution, that’s why waters based on them contain a negligible amount of salts. Such water is called “soft”. At the same time mineral substances of sedimentary beds are dissolved in water more readily. Thus, lakes with watercollecting basins based on sedimentary rocks usually have “hard” water, i.e. enriched by salts dissolved in it. If bedding rocks contain lime (a sedimentary rock consisting of calcium carbonat), then water of the lake is expected to be hard.. Such lakes better resist acidification, with carbonates neutralizing acids.
Watercollecting basins of lakes in Adirondack Mountains are mainly based on granites. Water of these lakes is soft and, as a rule, poor in dissolved mineral compounds. Such lakes are strongly affected by acid rains.
Sensitivity of lakes to acid rains is determined not only by bedding rocks but also by a certain role played by local soils. Soils on watersheds and shores, rich in soluble mineral salts, such as calcium and magnesium carbonates contribute to conservation of lake as these salts neutralize acids.
For example, watersheds on the territory of state Maine have granite as a bedrocks, however, lakes here do not become acid. Apparently, it is the result of the acid rainfalls neutralization by the lime- rich soil. And rains falling out in this district have the average рН 4.3. However, some lakes in Florida, fed by rivers and streams running over sedimentary rocks, nevertheless, appear acidic. Probably, the inflow of ground waters in these lakes is insignificant, and superficial waters run over soils, containing not enough calcium carbonate.
Both lakes and inhabiting them animals and plants are responsive to acid rains; soil and land ecosystems also suffer from their effect. As well as lakes, soils react to acid rains in different manner. A pattern here is similar: the soils which have arisen on sedimentary base (for example, carbonaceous minerals), or soils rich in organic matter, are capable to neutralize acid rains. Soils, formed on granites and gneisses, which are little or not at all water-insoluble, easily become acidified. Approximately 70-80 % of lands in the eastern part of the USA have soils, responsive to acidification. Acid rains easily leach from such soils a small amount of mineral nutrients, reducing their fertility. Actually, the effect of acid rains on soil fertility can be easily demonstrated only in laboratory conditions. However, this possibility combined with other already known effects is capable to result in a real effect.
Дата добавления: 2015-10-26; просмотров: 169 | Нарушение авторских прав
| <== предыдущая страница | | | следующая страница ==> |
| c) девять лет; | | | Кислотные дожди – причина деградации лесов и ухудшения экологического состояния водоемов |