green'house effect" 1. an atmospheric heating phenomenon, caused by short-wave solar radiation being readily transmitted inward through the earth's atmosphere but longer-wavelength heat radiation less readily transmitted outward, owing to its absorption by atmospheric carbon dioxide, water vapor, methane, and other gases; thus, the rising level of carbon dioxide is viewed with concern. 2. such a phenomenon on another planet. Green Revolution Green Revolution, term referring mainly to dramatic increases in cereal-grain yields in many developing countries beginning in the late 1960s, due largely to use of genetically improved varieties. Beginning in the mid-1940s researchers in Mexico developed broadly adapted, short-stemmed, disease-resistant wheats that excelled at converting fertilizer and water into high yields. The improved seeds were instrumental in boosting Mexican wheat production and averting famine in India and Pakistan, earning the 1970 Nobel Peace Prize for American plant breeder Norman E. Borlaug, leader of the Mexican wheat team. Significant though less dramatic improvements followed in corn. The Mexican program inspired a similarly successful rice-research effort in the Philippines and a network of research centers dedicated to the important food crops and environments of the developing world. By 1992 the system included 18 centers, mostly in developing countries, staffed by scientists from around the world, supported by a consortium of foundations, national governments, and international agencies. Recent research responds to criticism that the Green Revolution depends on fertilizers, irrigation, and other factors that poor farmers cannot afford and that may be
Transcript
green'house effect"
1. an atmospheric heating phenomenon, caused by short-wave solar radiation being readily transmitted inward through the earth's atmosphere but longer-wavelength heat radiation less readily transmitted outward, owing to its absorption by atmospheric carbon dioxide, water vapor, methane, and other gases; thus, the rising level of carbon dioxide is viewed with concern. 2. such a phenomenon on another planet.
Green RevolutionGreen Revolution, term referring mainly to dramatic increases in cereal-grain yields in many developing countries beginning in the late 1960s, due largely to use of genetically improved varieties. Beginning in the mid-1940s researchers in Mexico developed broadly adapted, short-stemmed, disease-resistant wheats that excelled at converting fertilizer and water into high yields. The improved seeds were instrumental in boosting Mexican wheat production and averting famine in India and Pakistan, earning the 1970 Nobel Peace Prize for American plant breeder Norman E. Borlaug, leader of the Mexican wheat team. Significant though less dramatic improvements followed in corn. The Mexican program inspired a similarly successful rice-research effort in the Philippines and a network of research centers dedicated to the important food crops and environments of the developing world. By 1992 the system included 18 centers, mostly in developing countries, staffed by scientists from around the world, supported by a consortium of foundations, national governments, and international agencies. Recent research responds to criticism that the Green Revolution depends on fertilizers, irrigation, and other factors that poor farmers cannot afford and that may be ecologically harmful; and that it promotes monocultures and loss of genetic diversity.
noise pollution
Noise is generally regarded as an unwanted sound or sound, which produces unpleasant effects on the ears.
Noise is produced by household gadgets, vehicles on the road, jet planes, loud speakers etc. Noise produces severe adverse effects on the quality of mans surrounding and is, therefore, considered to be polluting the environment. It is the loudness and duration of the noise which is disturbing and causes physical discomfort and damage to hearing.
The unit of measurement of intensity of sound is called decibel (dB). Our ear is sensitive to an extremely wide range of intensity from 0 to 180 db, 0dB being the threshold of hearing, whereas 140 dB marks the threshold of pain.
Sources
Household gadgets like mixer, grinder, vacuum cleaner, washing machine, cooler, air conditioners, greatly enhance the levels of sound and are deleterious to health.
Loud speakers not only disturb the students in their studies but also the peace of the locality. Loud radios, stereos and televisions are also a major source.
Printing presses, industries, vehicles on road, aeroplanes contribute to noise pollutions in large cities.
Ecosystem Structure
As mentioned earlier, an ecosystem consists of two major components,
Abiotic and
Biotic
Abiotic componentsAbiotic components are of three kinds
Inorganic substances
These are various chemical substances found in the ecosystem like carbon, nitrogen, sulphur, phosphorous, oxygen and compounds like carbon dioxide, water etc. A vital balance among these components in the environment should be maintained and nature plays an important role in doing this
Example:
Carbon cycle, water cycle, nitrogen cycle etc.
Organic substances
These are various chemical substances found in the ecosystem but they are organic in nature. They form the greater part of the living organism and form a link between the abiotic compounds and the biotic compounds.
Example:
Proteins, carbohydrates, lipids (fats) humic substances, etc.
Climatic factors
These are of two types:
Atmosphere, which means sunlight, temperature, wind, humidity etc.
Edaphic, which means the physical and chemical properties of the soil, it's water and air content etc.
These factors affect the distribution, number, metabolism and behaviour of the organism.
Biotic componentsAn ecosystem consists of a number of organisms which co-exist and come into regular contact with each other. Some of these organisms may have a special relationship which may profoundly influence its distribution and abundance.
In a given ecosystem three types of biotic components may be found which are grouped according to their modes of nutrition.
Producers
These are autotropic organisms (mainly green plants) so called because they are capable of synthesising organic food. They contain a special pigment called chlorophyll that absorbs solar energy and converts it into chemical energy during photosynthesis. The end product of photosynthesis is glucose, which is stored in the plant in the form of starch. This group forms the source of food for many organisms.
Consumers
These are heterotropic organisms (mainly animals). They are not capable of synthesising organic food and so feed on other organisms (may be plants or animals) to meet their food requirement. They may be further classified as follows:
Animals that stalk their prey are called predators and those that line and grow on other organisms and adapt them as their habitat are known as parasites.
Decomposers
There are saprophytic organisms (mainly bacteria and fungi) that live on dead animals and plants. In terrestrial ecosystem, bacteria act on animal tissue and fungi on plants but there may be exceptions also. This group of organisms plays a vital role in releasing back the biotic components into the environment. By digesting the dead tissue through enzyme secretion, the basic elements of protoplasm are released into the environment, to be made available for reuse by the producers to be built into organic compounds again. So it can be seen that matter circulates in nature: though it constantly changes its form, there is no overall loss or gain.
Here is a diagrammatic representation showing the interdependence of producers and consumers in an ecosystem.
Interdependence of producers and consumers in an ecosystem
Functions:-In an ecosystem there are two processes proceeding simultaneously:
1 ) Energy flow and
2 ) Biogeochemical cycle
The energy flow is in a single direction and is non-cyclic where as Biogeochemical flow is cyclic (Any mineral cycle)
Biogeochemical flow
Energy flowAlthough matter circulates, energy cannot be reused indefinitely. Solar energy is converted by the photosynthetic producers (plants) into chemical energy in the form of plant carbohydrates. Herbivores consume the plant carbohydrates and so this chemical energy is transferred to them. Carnivores consume herbivores. So the energy is circulated further to the next trophic level. In these animals, this chemical energy is converted mostly into mechanical energy (work done) and heat. The heat is lost to the atmosphere at each trophic level. At the cell level, chemical energy in the food molecules is transferred into usable energy and stored as ATP (adenosine triphosphate) molecules. The body cells use the energy stored in ATP for synthesis of new chemical compounds and their transport and for mechanical work. It is estimated that 90% of the energy is used up at each trophic level and only 10% of it is transferred to the next trophic level. Finally, at the last trophic level (decomposer) no energy is left for recycling. Hence, energy flows from sun through producers to consumers in a single direction only. The decreasing energy level at each step sets the limit of trophic levels to a maximum of 4 or 5. It is the continual trapping of light energy by green plants that makes good this loss and maintains the uninterrupted flow energy in an ecosystem.
It is found that there is maximum energy at the producer (plant) level and as you go further and further the energy in food goes on decreasing. Therefore, the herbivores get more energy rich food, than carnivores.
Biogeochemical cyclesOrganic materials synthesised by the producers are eaten and assimilated by the consumers. With the help of decomposers, all the organic materials in the bodies of the consumers are eventually broken down into inorganic materials. These are then rebuilt into organic compounds by the synthetic activities of the consumers. Thus, matter circulates in nature. Though it may constantly change it's form, there is no overall loss or gain.
The cyclic flow of nutrients between non-living environment (soil, rocks, air, water) and living organisms is known as biogeochemical cycle. The major nutrient element i.e. carbon, hydrogen,
oxygen and nitrogen, which form about 95% mass of the living organism, are circulated again and again between living and non-living components of the ecosystem.
Let us study the carbon cycle and the nitrogen cycle
Carbon cycleThe atmosphere contains a pool of CO2. CO2 is removed from the pool by the photosynthetic activities of plants. It is released back into the environment by respiration which is carried out by all organisms including those micro-organisms (decomposing bacteria) responsible for the decay of dead plants and animals. Not all dead material decays. Sometimes dead plants and animals form fossil fuels such as peat, coal, petroleum and petroleum-based gases. Man uses these materials as sources of energy and when they are burned CO2 is returned to the CO2 pool.
The Carbon Cycle The amount of carbon dioxide in the atmosphere is maintained by a balance between the processes that withdraw carbon dioxide from it (photosynthesis) and those, that add carbon dioxide to it (respiration and combustion). The red arrows represent the flow of carbon dioxide.
Nitrogen cycleThe nitrogen cycle is complex as it depends on the activities of various bacteria. Nitrate in the soil is built up by plants into protein which is then passed on to animals, which eat the plants. The nitrogen from the protein is returned to the environment as ammonia (ammonification), either from excretory matter or through the action of decomposing bacteria on dead bodies. Various nitrifying bacteria convert the ammonia back to nitrate (nitrification). The nitrifying bacteria play an important role in replenishing the environment with nitrate upon which plants are dependent for their protein. Another class of bacteria called denitrifying bacteria liberate free nitrogen from nitrate which leads to the pool of nitrogen gas being built up in the atmosphere. Some of this nitrogen is constantly removed by nitrogen fixing micro-organisms, which build it up into nitrate and ultimately protein.
The Nitrogen cycleThe amber arrows represent the flow of nitrogen
The Greenhouse effect is the rise in temperature that the Earth experiences because certain gases in the atmosphere (referred to as greenhouse gases), trap energy from the Sun. Without these gases heat would escape back into space and living on Earth would be inhospitable with average temperature being about 60 F lower. Because of the way they warm our world these gases are referred to as green house gases.
Some green house gases occur naturally, while others result from human activity. The various natural greenhouse gases are: water vapor, carbon dioxide, nitrous oxide, ozone and methane. Carbon dioxide, methane and nitrous oxide, levels in the atmosphere are added by human activities of industry, transport, agriculture, organic and solid waste combustion. Very powerful green house gases that are not naturally occurring include hydroflurocarbons (HFCs) perflurocarbons (PFCs) and sulphur hexafluroide (SF6), which are generated in a variety of industrial processes.
Greenhouse effect around the Earth
Green house gases in the atmosphere behave much like the glass panes in a green house. Green houses are like small glass houses whose transparent glass roof and walls allow sunrays to pass through. It keeps the heat from escaping, thus allowing vegetables and flowers to grow even in cold weather.
An effect similar to the one in glass chamber is responsible for keeping the Earth's surface warmer than it would otherwise be. Green house gases in the atmosphere around the Earth act like a glass of the greenhouse chamber.
Earth receives a large amount of energy from the Sun, which emits U.V. radiations, visible light and infra-red (IR) radiations. Some of the solar radiation is reflected away by the atmosphere and Earth, while some of the infrared radiation is absorbed and re-emitted in all directions by the green house gas molecules. The effect of this is to warm the Earth's surface and lower the atmosphere.
A large part of the Sun's radiation pass through the Earth's atmosphere and Earth absorbs these IR radiations of short wavelength. This warms the Earth's surface and increases its temperature. It starts emitting infra-red radiations of longer wavelengths. The partially radiated infra-red radiations from the Earth are absorbed by CO2 and green house gases. This restricts the outward flow of infrared radiation and effectively stores some of the heat in the atmosphere, producing a net warming of the surface. The heating of the atmosphere due to absorption of infra-red radiations by carbon dioxide and other gases is called greenhouse effect.
As more and more infra-red radiations are trapped, the atmosphere becomes hotter and therefore, temperature rises.
Fig: 18.1 - The green house effect
Note: Each green house gas differs in its ability to absorb heat in the atmosphere. HFC's and PFC's are the maximum heat absorbent's. Methane traps over 21 times more heat per molecule than carbon dioxide. Nitrous oxide absorbs 270 times more heat per molecule than carbon dioxide.
Further only long-lived gases have the potential for affecting the global environment. This effect arises principally because the concentrations of long-lived gases are the result of many years of accumulated emissions. The mean atmospheric life time of CH4 is about 8 years. The mean lifetime of N2O in the atmosphere is about 150 years. CO2 is chemically inert and is not destroyed by photochemical or chemical processes in the atmosphere. It is either lost by transfer into the ocean or biosphere, or it builds up in the atmosphere.
Advantages of Greenhouse Effect
The presence of carbon dioxide and other gases in the atmosphere produces the greenhouse effect, which keeps the atmosphere warm. The warm atmosphere is very essential for the survival of life on Earth in the following ways:
Precipitation of water, formation of clouds, rainfall etc. life in the biosphere depend on these resources.
The warm atmosphere helps in the growth of vegetation and forest etc. These are sources of food, shelter etc.
This effect helps in rapid bio-degradation of dead plants and animals.
Global warming
Harmful results of Greenhouse Effect is global warming. While the green house gases enable life to exist, problems arise when the atmospheric concentrations of these gases increase. All climate changes up to the industrial revolution occurred naturally as very few gases were released by human activity into the atmosphere. Human activity through rapid industrialization, combustion of fossil fuel, demands of population growth and deforestation have altered the chemical composition of gases in the atmosphere.
In the last century the Earth's surface temperature has risen by over 1 F. Accelerated warming has taken place over the last two decades and the ten hottest years were recorded in the last 15 years of the century, 1998 being the hottest year. Scientists expect the temperature to rise an additional 0.6 to 2.5 C in the next 50 years and 1.4 5.8 C. (with significant regional variation) in the next 100 years. The impact of a change in the Earth's temperature on climate can be gauged by the fact that at the peak of the last ice age (18,000 years ago) the temperature was only 7 F colder than it is today.
Since the beginning of the industrial revolution atmospheric concentration of carbon dioxide has increased nearly by 30%. Methane concentration has increased by more than 100% and nitrous
oxide by about 15%. These increases have enhanced the heat trapping capability of the Earth's atmosphere.
In this industrial age, excessive burning of fossil fuels have released enormous amount of carbon dioxide in atmosphere, which cannot be removed by plants and ocean waters. Thus, concentration of carbon dioxide in atmosphere is steadily rising and increasing the greenhouse effect or global warming.
Fig: 18.2 Global Temperature Changes
Estimating future emissions is difficult, though scientists in western countries have developed several different scenarios based on differing projections of underlying factors. One projection states that in the absence of emission policies, carbon dioxide concentrations are projected to be 30-150 % higher than todays levels in the next 100 years. This in turn will have disastrous consequences. Scientists are estimating the following impacts and consequences:
Rising sea levels
Globally sea levels have risen 4-8 inches over the last century. The high temperatures have already started melting polar ice caps sea icebergs and glaciers. This has released enormous amount of water. Warmer temperatures also heat water and make it expand; thus ocean levels need more space and further rise. The level of sea is likely to rise by several inches to up to 3 feet during this century. This would lead to vast coastal flooding, huge expense by Governments and individuals to safeguard oceanfront property, submerging of low-lying coastal countries e.g., Denmark, Bangladesh. It would also cause the conversion of fresh water habitats and eco-systems into saltwater areas endangering vegetation, crops, animals and water supply along the coast.
Change in climate
Global warming has already occurred and will continue to do so. Evaporation will increase as climate warms and there will be an increase in average global precipitation. Local climate conditions are likely to change depending on the modifications of local rainfall patterns. The quality and quantity of drinking water, water availability for irrigation, industrial use, electricity generation and the health of fish may be significantly affected by changes in precipitation and increased evaporation.
Soil moisture is likely to drop affecting crops and the need for irrigation. The high temperature may reduce crop production, thereby causing famines. Intense rainfall (extremes) is also predicted. Tropical rains and hurricanes will be more frequent and stronger. Increased rainfall may cause more frequent flooding. Climate change would likely add stress to major river basins worldwide.
Human health and heat stress
Along with warmer temperatures and higher humidity, the number of very hot days is expected to rise in many areas around the globe. Heat stress occurs in such conditions and the young, old and poor people are more susceptible to it. High temperatures will reduce work efficiency of human beings.
Further air pollution, changes in food and water supplies resulting from global warming, will all affect human health. Changing patterns of precipitation and temperature may produce new breeding sites for pests, shifting the range of infectious diseases.
Alteration of habitats and ecosystems
Many of the worlds habitats and ecosystems depend on a delicate balance of rainfall, temperature and soil type. A complex food chain supply exists based on these factors. Higher temperatures and precipitation changes are likely to cause diverse changes such as increased forest susceptibility to fire, disease and insect damage also, deserts may expand into existing grass lands.
Similarly, changes in ocean temperature will adversely affect the marine life. If future changes occur as rapidly as some scientists predict, plants, animals and marine life may not be able to adapt quickly enough to survive.
Cooling of stratosphere
Increasing concentration of greenhouse gases are expected to cause cooling of stratosphere. This could happen because most of the thermal IR radiation will be trapped and absorbed at lower altitudes; little will be left to warm the stratosphere. Cooling of stratosphere would mean enhanced greenhouse effect i.e., greater global warming.
Sustainable Development
The importance of maintaining the ecological balance and conservation of the resources has been increasingly becoming clear in the last two decades. It has now become necessary for all countries in the world to recognise this fact and plan what is known as 'sustainable development'. The United Nations World Commission of Environment and Development in 1987 has defined sustainable development as "a process of change in which the exploitation of resources, the direction of investments, the orientation of technological development and the institutional change are in harmony and enhance both current and future generations to meet their needs."
This means that the requirements of the present generation in terms of economic growth and community development (to provide for basic needs like food, water, shelter, education, etc) are met without compromising on environmental protection. This will ensure that every generation will leave clean air, water and soil resources for the future generations.
Methods to Enforce the Concept of Sustainable Development
judiciously use the resources that are available in plenty and maintain them without depletion or pollution
restrict the use of the already endangered resources and protect them from unsustainable development.
to increase awareness about the concept of sustainable development and ensure that the people understand its full meaning. This concept means that there is a symbiotic relationship (mutually beneficial) between the developmental process and environment protection. If environment protection is ignored, then the very basis of developmental processes (the natural resources) will get exhausted which will spell doom for mankind. On the other hand, one cannot ignore development and only think of environmental protection. However, it is necessary to strike a balance between the two.
Towards this end, every individual has to make his actions eco-friendly. This is possible only if man stops thinking of himself as the supreme creation and enjoys only the benefits. It is high time man realises that he is an integral part of the environment. He should also realise that because he is at the pinnacle of evolution and has also more responsibility towards maintaining the environment.
ACID RAIN:-
Sulphur dioxide and nitrogen oxides react with water in the atmosphere producing sulphuric acid and nitric acid. These acids come down along with the rain. This phenomenon is called acid rain. The pH of acid rain varies from 3-6. The composition of acid rain is sulphuric acid, nitric acid and weak carbonic acid.
It has the following adverse affects on the environment:
Causes respiratory and skin disorders.
Affects productivity of plants by damaging the leaves.
Enters the soil and affects the soil pH and other conditions.
Enters the ground and river waters which causes harm to the aquatic life.
Causes damage to marble and thus damages buildings and monuments like the Taj Mahal
Soils retrogression and degradation in the French school of pedology are two regressive evolution processes associated with the loss of equilibrium of a stable soil. Retrogression is primarily due to erosion and corresponds to a phenomenon where succession reverts back to pioneer conditions (such as bare ground). Degradation is an evolution, different of natural evolution, related to the locale climate and vegetation. It is due to the replacement of the primitive vegetation (known as climax) by a secondary vegetation. This replacement modifies the humus composition and amount, and impacts the formation of the soil. It is directly related to human activity. [1]
The soil represents the surface layer of the earth's crust.
At the beginning of a soil formation, only the bare rock outcrops. It is gradually colonized by pioneer species (lichens and mosses), then herbaceous vegetation, shrubs and finally forest. In parallel a first humus-bearing horizon is formed (the A horizon), followed by some mineral horizons (B horizons). Each successive stage is characterized by a certain association of soil/vegetation and environment, which defines an ecosystem.
After a certain time of parallel evolution between the ground and the vegetation, a state of steady balance is reached; this stage of development is called climax by some ecologists and "natural potential" by others. Succession is the evolution towards climax. Regardless of its name, the equilibrium stage of primary succession is the highest natural form of development that the environmental factors are capable of producing.
The cycles of evolution of soils have very variable durations, between a thousand-year-old for soils of quick evolution (A horizon only) to more than a million of years for soils of slow development. The same soil may achieve several successive steady state conditions during its existence, as exhibited by the Pygmy forest sequence in Mendocino County, California. Soils naturally reach a state of high productivity from which they naturally degrade as mineral nutrients are removed from the soil system. Thus older soils are more vulnerable to the effects of induced retrogression and degradation.
yields impact: Recent increases in the human population have placed a great strain on the world's soil systems. More than 6 billion people are now using about 38% of the land area of the Earth to raise crops and livestock.[2] Many soils suffer from various types of degradation, that can ultimately reduce their ability to produce food resources. Slight degradation refers to land where yield potential has been reduced by 10%, moderate degradation refers to a yield decrease from 10-50 %. Severely degraded soils have lost more than 50% of their potential. Most severely degraded soils are located in developing countries such as Asia and Africa.
natural disasters : mud flows, floods ... responsible for the death of many living beings each year
deterioration of the water quality: the increase in the turbidity of water and the contribution of nitrogen and of phosphorus can result in eutrophication. Soils particles in surface waters are also accompanied by agricultural inputs and by some pollutants of industrial, urban and road origin (such as heavy metals). The ecological impact of agricultural inputs (such as weed killer) is known but difficult to evaluate because of the multiplicity of the products and their broad spectrum of action.
biological diversity: soil degradation may involve the disappearance of the climax vegetation, the decrease in animal habitat, thus leading to a biodiversity loss and animal extinction ...
Soil enhancement and rebuilding
Problems of soil erosion can be fought, and certain practices can lead to soil enhancement and rebuilding. Even though simple, methods for reducing erosion are often not chosen because these practices outweigh the short-term benefits. Rebuilding is especially possible through the improvement of soil structure, addition of organic matter and limitation of runoff. However, these techniques will never totally succeed to restore a soil (and the fauna and flora associated to it) that took more than 1000 years to build up.
Ecological factors influencing soil formation
There are two types of ecological factors influencing the evolution of a soil (through alteration and humification). These two factors are extremely significant to explain the evolution of soils of short development.
A first type of factor is the average climate of an area and the vegetation which is associated (biome). This factor allows one to define the world major areas of vegetation and soils.
A second type of factor is more local, and is related to the original rock and local drainage. This type of factor explains appearance of specialized associations (ex peat bogs).
The major problem that the atmosphere is being subjected to is pollution. In India, about 100 million tons of pollutants are being added to the atmosphere annually. This figure is likely to go up in future.
Polluted air is harmful to man and the biosphere on the whole, as well. This problem needs to be tackled urgently. Since all of us contribute to it directly or indirectly, we must study air pollution in detail and discuss the means of controlling and preventing it.
air pollution, contamination of the air by noxious gases and minute particles of solid and liquid matter (particulates) in concentrations that endanger health. The major sources of air pollution are transportation engines, power and heat generation, industrial processes, and the burning of solid waste.
Sources of Air PollutionMost of the sources of air pollution are related to man's activities as a result of the modern lifestyle. Added to this are also natural causes like the volcanoes, anaerobic decomposition of organic matter, atmospheric reactions, etc.
Burning of Fossil FuelsFossil fuels include petroleum and coal. Burning of coal produces a lot of smoke and dust whereas burning of petrol mainly produces sulphur dioxide. In addition to these, the pollutants include carbon monoxide (CO), carbon dioxide (CO2), nitrogen oxides, hydrocarbons, particulate matter and traces of metals.
AutomobilesPetrol on combustion produces carbon monoxide, hydrocarbons, nitrogen oxides, aldehydes, sulphur compounds, organic acids and ammonia and carbon particles. Incomplete combustion of petrol produces a hydrocarbon, 3,4 benzpyrene. There is more pollution during acceleration and deceleration than during constant speed.
Industries
Fertiliser Plants
They produce oxides, sulphur, nitrogen, hydrocarbons, particulate matter and fluorine.
Thermal Plants
Since they are coal based the pollutants are fly ash, soot and sulphur dioxide.
Textile Industries
They produce cotton dust, nitrogen oxides, chlorine, naphtha vapours, smoke and sulphur dioxide.
They produce carbon monoxide, carbon dioxide, sulphur dioxide, phenol, fluorine, cyanide, particulate matter, etc.
Volcanic eruptions release oxides of nitrogen that pollute the atmosphere.
Decomposition of organic matter under anaerobic conditions produces methane which on being oxidised in the atmosphere produces carbon monoxide. Decomposition of these matter also produces foul smelling gases.
Photochemical oxidation of marine organic matter and biological oxidation by marine organisms produce lot of carbon monoxide on the surface of the oceans which enters the atmosphere.
Major Pollutants
There are six main categories of air pollutants:
oxides of carbon
sulphur dioxide
oxides of nitrogen
hydrocarbon
inorganic particulate matter and aerosols
organic particulate matter
Harmful Effects of the Pollutants in Air
The various categories of air pollutants and their harmful effects are summarised in the given table:
Pollutant Source/Cause Effect
Carbon monoxide Automobile exhaust, photochemical reactions in the atmosphere, biological oxidation by marine organisms, etc.
Affects the respiratory activity as haemoglobin has more affinity for Co than for oxygen. Thus, CO combines with HB and thus reduces the oxygen-carrying capacity of blood. This results in blurred vision, headache, unconsciousness and
Pollutant Source/Cause Effect
death due to asphyxiation (lack of oxygen).
Carbon di oxide
Carbon Burning of fossil fuels,depletion of forests (that remove excess carbon dioxide and help in maintaining the oxygen-carbon dioxide ratio).
Global warming as it is one of the greenhouse gases.
Sulphur dioxide
Industries, burning of fossil fuels, forest fires, electric generation plants, smelting plants, industnal boilers, petroleum refineries and volcanic eruptions.
Respiratory problems, severe headache,reduced productivity of plants, yellowing and reduced storage time for paper, yellowing and damage to limestone and marble, damage to leather, increased rate of corrosion of iron, steel, zinc and aluminium.
Hydrocarbons Polynuclear Aromatic Compounds(PAC) and Polynuclear Aromatic Hydrocarbons(PAH)
Automobile exhaust and industries,leaking fuel tanks, leaching from toxic waste dumping sites and coal tar lining of some water supply pipes.
Carcinogenic (may cause leukemia)
Chlorofluoro carbons (CFCs)
Refngerators, air conditioners, foam shaving cream, spray cans and cleaning solvents.
Destroy ozone layer which then permits harmful UV rays to enter the atmosphere.
Nitrogen Oxides
Automobile exhausts, burning of fossil fuels, forest fires,electric generation plants, smelting plants, industnal boilers, petroleum refineries and volcanic eruptions
Forms photochemical smog, at higher concentrations causes leaf damage or affects the photosynthetic activities of plants and causes respiratory problems in mammals.
PAN - peroxylacetyl -nitrate
Photochemical reactions of hydrocarbons and nitrogen oxides.
Irritation of eye, throat and respiratory tract, damage to clothes, paint and rubber articles, damage to leaves and stomatal tissue in plants.
Pollutant Source/Cause Effect
Particulate matter Lead halides (lead pollution)
Combustion of leaded gasoline products
Toxic effect in man.
Asbestos particles Mining activitiesAsbestosis - a cancerous disease of the lungs
Silicon dioxideStone cutting, pottery, glass manufacturing and cement industries.
Silicosis, a cancerous disease.
Biological matter like the pollen grains
Flowers Allergy
Fungal spores, bacteria, virus, etc
Microbes Infectious deseases
Effects of Air Pollution
Global Warming
Most of the solar radiation entering the earth's atmosphere is reflected back into the space. However some of the heat is absorbed by the gases like the carbon dioxide. This serves to keep the earth warm much like the greenhouses. Greenhouses are glasshouses which maintain a temperature higher than the surroundings for the plants to grow and yield better. The other gases that contribute to this are water vapour, methane, chlorofluorocarbons (CFCs) and nitrous oxide. These gases are called the greenhouse gases.
While greenhouse effect is a necessary and natural phenomenon. Every year teh temperature are going up due to pollution and the levels of these greenhouse gases is also going up. This is called global warming. According to estimates, at the current rate of increase, the average global temperature will go up by 3oC to 8oC in the next 100 years.
This will have the following effects:
Climate of different regions
Distribution of plants and animals
Disturbance in agriculture and food production
Melting of snow caps and resultant increase in sea levels. This will submerge parts of coastal cities of Calcutta, New York, London and other major cities.
Formation of Photochemical SmogWhen pollutants like hydrocarbons and nitrogen oxides combine in the presence of sunlight, smog is formed. This is a mixture of gases and since it is formed by photochemical reactions, it is called the photochemical smog. The word 'smog' is derived from the two words-smoke and fog.
It forms a yellowish brown haze especially during winter and hampers visibility. It also causes many respiratory disorders and allergies as it contains polluting gases.
Formation of Acid RainSulphur dioxide and nitrogen oxides react with water in the atmosphere producing sulphuric acid and nitric acid. These acids come down along with the rain. This phenomenon is called acid rain. The pH of acid rain varies from 3-6. The composition of acid rain is sulphuric acid, nitric acid and weak carbonic acid.
It has the following adverse affects on the environment:
Causes respiratory and skin disorders.
Affects productivity of plants by damaging the leaves.
Enters the soil and affects the soil pH and other conditions.
Enters the ground and river waters which causes harm to the aquatic life.
Causes damage to marble and thus damages buildings and monuments like the Taj Mahal
Aerosol FormationAerosol is formed by the dispersion of solid or liquid matter in the atmosphere. There are natural aerosols also in the atmosphere. However, polluting aerosols are formed by the pollutant particulate matter like carbon particles.
If the aerosols form a thick layer in the troposphere, they affect the weather conditions by blocking the solar radiation. Aerosols are also deposited on the leaves and affect the photosynthesis. Aerosols disperse the organic metallic pollutants far and wide.
Depletion of OzoneThe stratosphere of the atmosphere has ozone (O3). Ozone is known to absorb the Ultraviolet (UV) rays present in the sun's radiation. The UV rays are believed to cause skin cancer and mutations. Thus, the ozone protects us from the harmful effects of the UV rays.
However, hydrocarbons such as the chlorofluorocarbons (CFCs) destroy the ozone molecules which deplete the ozone layer. Ozone holes have been detected in the atmosphere which permit the UV rays to reach the earth's surface. The harmful effects of the UV rays are visible in the countries such as Australia and New Zealand where the rate of skin cancer is higher than the other regions of the world.
Control of Air PollutionAir pollution can be controlled by different methods depending on the source and the pollutant. The different methods are:
One of the major causes of air pollution are the automobiles. The fuels being used should be lead-free as this will reduce the level of lead in the atmosphere. The carburetor should be cleaned regularly and good quality fuel should be used. This reduces the smoke emission from the exhaust pipes of the vehicles. Efforts to introduce vehicles running on alternate sources (for example solar energy) of energy should be made. These methods will go a long way in reducing the occurrence of photochemical smog.
The industrial pollution is best controlled at source. The polluting gases should be passed through filters and other devices such as cyclone collectors, scrubbers, precipitators, etc. so that the particulate matter is removed before the waste gases are released out. The toxic gases should be detoxified.
The domestic and industrial smoke producing units should have long chimneys to take the polluting gases far above and then disperse over a larger area. They should also invest in solar cookers or bio gas.
The pollution by sulphur dioxide is mainly due to coal-based industries. Alternate non-sulphur containing fuel must be used. It is also possible to remove the sulphur from the fuel before use.
There are many plant species like the neem (Azadirachta indica), bel (Aegle marmelos), gulmohur (Delonix regia), etc. that clean the atmosphere. More trees of such types should be planted.
For effective control and prevention of air pollution it is important to educate people and create public awareness about the ill-effects of air pollution.
The following are some methods that may be adopted to control pollution on a large scale:
Combustion
Pollutants in the form of organic gases or vapours can be burnt to convert them into water vapour and relatively less harmful products, such as carbon dioxide.
Absorption
The gaseous effluents may be made to pass through scrubbers or absorbers. These contain a suitable liquid absorbent, which removes or modifies one or more of the pollutants present in the gaseous effluents making it comparitively harmless.
Adsorption
The gaseous effluents are passed through porous solid adsorbents kept in suitable containers. The organic and inorganic constituents of the effluent gases are trapped at the interphase of the solid adsorbent. Adsorbents hold (molecules of a gas or liquid or solute) to its surface, causing a thin film to form.
Desertification
the rapid depletion of plant life and the loss of topsoil at desert boundaries and in semiarid regions, usually caused by a combination of drought and the overexploitation of grasses and other vegetation by people.
Landslides occur when driving forces (gravity) that tend to move soiland things in the soil down a slope overcome resisting forces that holdthe ground in place (interlocking grains, natural cementing, plant roots,strength of materials on slope). Addition of water or removal of vegetationreduces resisting forces. Some landslides are reactivations of prehistoricslides; these areas repeatedly experience landslides (see La Conchita).
(a) In mountains, create lakes by damming valleys.
pollutionPollution is defined as an 'undesirable change in the physical, chemical or biological characteristics of air, water and land brought about by man's activities that may harmfully affect living organisms and other resources'.
Man, in his quest for a better life and more conveniences, is getting more and more dependent on technology and industries. These industries and the modern lifestyle are together making life easier and convenient for man. However, the same factors are also contributing towards the pollution of environment. Based on the component of environment being polluted, we have air pollution, water pollution and soil pollution.
The substances that actually cause pollution are called the pollutants. They may be the industrial gases, industrial effluents let out into the rivers, soap water, domestic wastes, medical wastes, etc.
Pollutants may be classified into two types based on bacterial activity. They are:
Biodegradable pollutants
Non-biodegradable pollutants
Biodegradable pollutants get broken down under natural conditions due to the action of micro-organisms. Therefore they are considerably less harmful. They behave as pollutants only in very large quantities. Example: excreta, sewage, pollen grains, etc.
Non-biodegradable pollutants cannot be broken down under natural conditions by the action of micro-organisms or they take an extremely long time to be broken down.
Example: Common plastics, DDT, metal wastes such as lead, mercury, arsenic, etc.
Based on the environmental component being polluted the following types of pollution are commonly addressed:
Air pollution
Water pollution
Soil pollution
Some Action Points to Protect or Improve the Environment
Biodegradable and non-biodegradable waste material have to be disposed after separating them.
Compost heap or a compost bin can be used to recycle waste food and other biodegradable materials.
Avoid unnecessary packaging of products.
Plant more trees. They help in absorbing excess carbon dioxide.
Observe World Environment Day (5th June).
Never dispose left over chemicals, oils, or other harmful substances down the drain, or dump them under the ground, or in water bodies or burn them in the garden. This causes pollution.
Don not burn any waste, especially plastics. The smoke may contain polluting gases.
Use unleaded petrol and alternate sources of energy and keep the engine properly tuned and serviced and the tyres inflated to the right pressure, so that vehicle runs efficiently.
Avoid fast starts and sudden braking of automobiles.
Walk or cycle wherever possible. Walking and cycling can help to keep you fit.
Use public transport wherever you can, or form a car pool for everyday travel.
Send your waste oil, old batteries and used tyres to a garage for recycling or safe disposal; all these can cause serious pollution.
Environmental degradation is the deterioration of the environment through depletion of resources such as air, water and soil; the destruction of ecosystems and the extinction of wildlife.[citation needed]
Environmental degradation is one of the ten threats officially cautioned by the High Level Threat Panel of the United Nations. The World Resources Institute (WRI), UNEP (the United Nations Environment Programme), UNDP (the United Nations Development Programme) and the World Bank have made public an important report on health and the environment worldwide on May 1, 1998.
Environmental degradation is of many types. When natural habitats are destroyed or natural resources are depleted, environment is degraded.
Environmental Change and Human Health, a special section of World Resources 1998-99 in this report describes how preventable illnesses and premature deaths are still occurring in very large numbers. If vast improvements are made in human health, millions of people will be living longer, healthier lives than ever before. In these poorest regions of the world an estimated one in five children will not live to see their fifth birthday, primarily because of environment-related diseases. Eleven million children die worldwide annually, equal to the combined populations of Norway and Switzerland, and mostly due to malaria, acute respiratory infections or diarrhea — illnesses that are largely preventable.
Conservation of natural resources:-
Man has to be dependent on natural resources despite all the scientific inventions
Natural resources could be classified into geographical, hydro-geological, atmosphere, edaphic, forest, crop, wildlife, marine / aquatic, animal, human and microbial resources
Natural resources are the basis of national income
Many resources depend on each other as well as on the ecosystem in general
Important geological resources include coal, mineral ores, non-metal ores, mineral oils, while hydro geological resource include, the total precipitation, river system, surface and underground
water. These two types of resources provide the basis for large number of industries and agriculture
Generation of power is mainly done by using water resources (hydro-electric power plants) and coal (thermal power plants) or atomic power plants.
Atmospheric resources include rainfall and its characters, temperature, sunshine
Edaphic resources include alluvial, black soil, red soil, laterite soil, desert soil and problematic soil
Forest resources are useful to man in many ways
Crop resources include all types of crops - whose cultivation has provided, food, fodder, clothing, industrial products to human beings
Aquatic and marine resources respectively include fresh water and sea fishes - which are exploited as human food
Animal resources include domesticated animals like horse, cattle, buffalo, sheep, goat, fowls, pigs, dogs and cats. Dairy industry is well developed in our country. Meat and poultry industry are also being developed
Wildlife protection is most important for maintaining ecological balance
Microbial resource is of large importance for many natural activities / processes. Recently, microbial resources are used for production of enzymes, acids, hormones in biotechnology
Almost all natural resources are misused in one way or other. Such misuse may create natural imbalance. Many of resources are limited and can last only for few years.
Misuse of some resources has gone to such an extent that resources have already become rare and near extinction / damage.
It is very important that every human being in our society should release the importance of conserving natural resource and adopt necessary measures to preserve them during his daily routine.
Water Harvesting
Almost 90% of the rainwater in India is running off every monsoon and only 10% of the rainwater is utilized (collected and stored). Rainwater harvesting is the process of collection and storage of rainwater with the purpose of consuming it or using it to recharge ground water. If more of this water is collected and stored, it could alleviate the growing water shortage and stall the impending water crisis, already being faced in many areas and cities in India.
Advantages in urban areas
Rainwater harvesting in urban areas can have manifold reasons. Some of the reasons rainwater harvesting can be adopted in cities are to provide supplemental water for the city's requirements, to increase soil moisture levels for urban greenery, to increase the ground water table through artificial recharge, to mitigate urban flooding and to improve the quality of groundwater. In urban areas of the developed world, at a household level, harvested rainwater can be used for flushing toilets and washing laundry. Indeed in hard water areas it is superior to mains water for this. It can also be used for showering or bathing. It may require treatment prior to use for drinking
In New Zealand, many houses away from the larger towns and cities routinely rely on rainwater collected from roofs as the only source of water for all household activities. This is almost inevitably the case for many holiday homes.
CHANGE IN TEMPERATURE:-
Change in the composition of air due to several human activities has brought about green house effect. Green house effect has brought about following phenomenal changes. The severity of these changes will aggravate further in the next 10-20 years. By 2040, CO2 level in air is expected to reach a level of 450 ppm (0.04%).
Increase in mean air temperature during various parts of year is to the tune of 0.8oC to 1.02oC as compared to their normal temperature.
Increase in sea level is observed in some parts of world due to excess heating of air - which has caused large scale melting of ice covers.
Change in the rainfall patterns due to variations in the convectional current (both in time and direction) caused by difference in heating pattern of earth's air.
Change/shifts in seasons and seasonal characters through out the globe. These may even include shifts in classification of earth into temperate, subtropical and tropical climates.
Major changes in water resources of world due to disturbances in hydrological cycles. Heavy rainfall tracts are gradually converted into low rainfall tracts, many humid areas being transformed into arid areas, ground water depletion is high and recharging is very low etc.
Shifts in disease/pest cycles of plants and animals. Many insignificant pests / diseases are attaining major proportions because composition of microbial population is affected by shift in temperature and hydrological cycles.
Reduced agricultural productivity and food shortage.
Increase in air temperature - popularly called as global warming - refers to mean temperature of entire globe averaged over all months and all places. Hence, the change in temperature at a place, in a particular month, may or may not match closely with change in temperature of globe.
Although many scientists have predicted a rise in temperature ranging from 1.5o C to 4.5oC due to doubling of CO2 concentration compared to pre-industrial period, the current change in temperature is to the tune of 0.88oC for a period from 1890 - 1989, while it was 1.02oC for a period from 1950 - 1989 in India. Similar increase in temperature is recorded in entire northern hemisphere. Warming is predicted to be greater in higher latitudes than in tropics and will be more pronounced during winter than in summer.
An increase in air temperature of this magnitude is not substantial enough to result in any changes as per the microclimatic experience. Because, over months, variations of temperature occur from 10o to 35oC. Between places the variation of mean annual temperature or seasonal temperature vary from 11-20oC. In this background most people may conclude that a change in air temperature to the tune of 0.88 to 1.02oC is not significant.
Unfortunately, this is not true. Because at global level, increase in mean temperature over places and over months indicate that in many places the rise in temperature is much higher (even upto 6-8oC) than normal. Variation of this order over normal is of great consequences. Deviation from normal is more significant than variation between months / places, as, such variations are part of normal temperatures.
The biggest increase in air temperatures are recorded from 1980 onwards - which coincides with highest increase in CO2 levels. Increased air temperatures is the cause for several changes in hydrological cycles, vegetation and agriculture, sea level rise and many other modification.
In India temperature anomalies were recorded up to +0.41oC during 1980 - 89. The rise in winter temperature is mostly observed in India than rise in pre-monsoon temperatures.
Increase in Sea Level
Over the past 100 years, sea level has increases by 18 cm. Inter government a panel in climate change has suggested that sea level would rise upto 90cm by 2100. Large scale flooding of California in 1999 and parts of western coast in India in the last 5-8 years, are testimonies to effects of sea level rise. If the sea level rises by 80-90 cm, perhaps many of coastal cities of world will be washed away besides great changes in harbours and their facilities, in sea routes and in fishery industry. With increased sea levels these are the first causalities. If the increase is to the tune of 90 cm, the world is going to face a catastrophe.
Till today, no attempt is successful for containing the effects of sea level rise. There is no method to save the inundating cities. Attempts to construct walls across the coast have met with little success.
There are two schools of thoughts about the actual scientific reason behind rise in sea level. According to traditional school of thought, global warming has resulted in melting of polar ice sheet extending to 12 million square kilometres as well as melting of ice on many mountainous regions of world. Extra water generated by these sources was thought to be the reason for rise in sea level.
Recently, another groups of scientists headed by Dr. Duncan Wingham have enunciated a theory that rise in sea level is due to expansion of sea water. Although it may look impracticable in the light of about 1o c mean rise in atmospheric temperature, the team of scientists believe that thermal expansion of sea water must have taken place in many places where the actual rise in air temperature are more than 7 - 8oC. Higher coefficient of expansion of saline water than normal water offers credence to this theory.
Change in the Rainfall Patterns
The rainfall patterns in the world are governed by differential heating of air layers over different latitudes. Differential heating of air is the main reason for different convectional air current movement from one part of globe to other. The rainfall is associated with these convectional current, because movement of air from high pressure region (due to higher air temperature) to low pressure region (due to low air temperature) will carry large quantity of water vapour, if it is from air above sea.
Due to rise in air temperature, the pattern of convectional current and differential heating pattern have substantially changed. This has resulted in change in amount of rainfall and its distribution. The study of global rainfall pattern over last 100 years, as related to positive and negative anomalies in temperatures has indicated that in many places rainfall increased and in many other places it has decreased substantially. In many other places the rainfall pattern is not following any constant relationship with other climatic parameters.
For e.g.,
Out of 10 highest positive winter anomalies of air temperature in northern hemisphere, two heavy and one poor monsoon years are identified. Similarly out of 10 highest negative winter anomalies of air temperature, two heavy and three poor monsoon years are identified. The difference in mean rainfall for ten highest positive and negative anomalies is 7 cm.
In general, the distribution of rainfall has substantially shifted from normal. In many places the rainfall is delayed, whereas in many other places it is preponed or untimely. In some parts of globe, severe aberrations of distribution pattern of rainfall has caused substantial changes in biosphere. In some parts of world, frequency of bizarre and heavy rain falls have increased by 20% changing their hydrological cycles.
Depletion of OzoneThe distribution of ozone in ionosphere, mesosphere and stratosphere is being depleted. The concentration of ozone is gradually reducing. As the content of ozone is highest in ionosphere and the
air itself being very thin, the depletion is negligible in ionosphere. But in mesosphere and stratosphere the air is thicker and ozone content is less. The depletion of ozone is of higher order in these layers. The so called hole in ozone layers simply means that above some continents (specifically Antarctica, Asia and parts of South America) the mesosphere and stratosphere have lost their original level of ozone content.
The depletion of ozone layer is a global phenomena both in terms of cause and effect. The geographical limits of countries are not barriers to either dispersal of gases in layers of atmosphere or depletion of gases. The causes for depletion may arise in any country. The effects (in terms of depletion) may arise in any other country. The effects (in terms of ozone depletion) need not be exactly above the country causing the depletion.
Causes of Depletion
It is now established that chloroflouro carbon (CFC) chemicals evolved from various refrigerants, coolants and propellants are the primary reasons for depletion of ozone. CFC are a group of chlorine bearing gases of low specific gravity. They rise to stratosphere and mesosphere. Due to ionising solar radiation in these layers, (which is the primary reason for production of ozone) fresh chlorine gas is produced from CFCs. This nascent chlorine gas has the capacity to react with ozone and bring down the level of ozone substantially.
The concept of ozone depletion is new. But study of international ozone trendis being made since 1988, when international ozone commission was established. Extensive ozone assessment facilities were established under International Middle Atmospheric Programme (IMAP) in India to study ozone along with number of other green house gases.
Changes in Seasons and Seasonal Characters
Based on temperature and rainfall, each part of world has definite seasons in a year with many characteristic features about air temperature, hydrological changes, biological growth etc. In most parts of world, summer and winter seasons are clearly distinguished. The onset and closure of these seasons is almost predefined and recurs every year with high degree of dependability. Such repeatable characters of seasons with good degree of dependability has resulted in many biological characteristic features of a region / country.
Due to change in air temperature and rainfall patterns, seasons have preponed on post-poned. Winters have extended in many places, while summer is more severe in other places. The degree of dependability has reduced and an element of uncertainity has increased. For e.g., in India pre-monsoon showers (summer rainfall) have reduced substantially, while cyclonic rainfall during November-December have become a regular feature. Similarly, the length of winter with low temperature and summer with high temperature have increased in many places. Unduly long spell of cold temperatures and unduly long hot dry temperatures have become more frequent in the last 15 - 20 years.
This has also necessitated a rethinking of classification of global climates from present system of equatorial, tropical, sub tropical, temperature and arctic / polar climates. A shift from tropical to temperate climates or tropical to subtropical climates has been recorded at many places.
Shifts in disease / pest cycles of animals and plants
Many diseases and pests of plants / animals follow a particular rhythm because of specific response of causal organism to a set of environmental conditions. Hence, disease / pest is more likely to attack a plant/animal if the environmental situations are favourable. These are called 'pre-disposing' factors. For e.g., sap sucking insects called 'aphids' are favourably multiplied in large number if day temperature is between 15 - 20oC and humidity is 60 - 80%.
Due to change in environment, the disease/ pests may occur with greater virulence or may subside. Hence, the attack of pests and diseases in recent years has been undergoing unpredictable changes. Many new diseases such as neckblast in paddy, wiltin cotton, as well as new pests like Armigera in cotton, nematode attack in paddy have been reported recently. Similarly, some diseases like black arm in cotton, blight in paddy, canker in guava have gradually reduced.
Even in human beings, the attack of some diseases is pre-disposed by many environmental factors.
For e.g., low temperature and high humidity favour asthma, coastal climate favouring elephantiasis, heavy rainfall favouring malaria. Recent spread of mosquito borne diseases like malaria in US and dengue in India are examples of spread of tropical habitat northward favouring growth and development of mosquito population in unconventional areas.
