Environmental Crisis Causes and Manifestations

Environmental crisis: Causes and manifestations

“He will manage the cure best who foresees what is to happen from the present condition of the patient” Hippocrates (ca. 460-377 B.C) Environmental crisis is a dramatic, unexpected and irreversible worsening of the environment leading to significant welfare losses. The environmental change has to be "unexpected" and by this mean it is a low probability event. Dramatic changes and an element of unexpectedness distinguish crisis from what one would refer to as resource tragedies. Resource tragedies are situations where resource overuse has been long-standing with the only remaining uncertainty being exactly when the train comes off the tracks. These situations are also worthy of study, but they are not true crises. An element of irreversibility is also important. If resources or nature are quick healing then it is difficult to see how any change in the environment should be of much concern, but if recovery would take a century or more things are quite different. Finally, the change in the environment must produce a significant welfare loss; therefore the scale of the damage Examples would be major extinctions and significant degradations of an ecosystem. Warnings that the Earth faces a ‘crisis’ or is already in crisis have blossomed since the 1960s, some predicting disaster before 2000. ‘Crisis’ is a turning point, a last chance to avoid, mitigate or adapt. The cause is usually identified as one or a combination of the following: people’s cavalier use of nature; over-population; misapplication of technology; faulty development ethics. What is perceived to be a crisis is subject to changing beliefs, fashion, and technological ability and so on. The word ‘Crisis’ has become an overworked word which affects how people respond to warnings. People’s circumstances and perceptions differ, so not all agree on what constitutes a crisis – ‘crisis’ for some may just be normal to others, and an opportunity to yet others. The term is also prone to emotive, journalistic usage (Blaikie, 1988). Some, mainly on the political left, suggest that the idea of a crisis may serve as a ‘liberal cover-up’ to divert attention from doing anything about ‘real problems’ such as social injustice and poverty (Young, 1990: 142–143). Other crisis supporters feel that environmental problems are mainly due to unsound concepts of development and modernisation – a social or ethical fault lies behind environmental crises (e.g. Weston, 1986: 4; Caldwell, 1990; Merchant, 1992: 17; Castro, 1993; Lomborg, 2001). More or less The Environmental Crisis is a Crisis of Consciousness. One may recognise several categories of perceived crisis....

• Excessive Pollution • Climate Change • Global Warming • Acid Rain • Ozone Layer Depletion • Biodiversity Degradation • Land Degradation • Nuclear Fallout and Hazards • Hazardous Waste

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Excessive Pollution

With the rapid growth of human population after industrial revolution the rate of pollution has increased considerably. Pollution is contamination of Earth’s environment with materials that interfere with human health, the quality of life, or the natural functioning of ecosystems (living organisms and their physical surroundings). Although some environmental pollution is a result of natural causes such as volcanic eruptions, most is caused by human activities.

There are two main categories of polluting materials, or pollutants. Biodegradable pollutants are materials, such as sewage, that rapidly decompose by natural processes. These pollutants become a problem when added to the environment faster than they can decompose. Non degradable pollutants are materials that either do not decompose or decompose slowly in the natural environment. Once contamination occurs, it is difficult or impossible to remove these pollutants from the environment.

Non degradable compounds such as dichlorodiphenyltrichloroethane (DDT), dioxins, polychlorinated biphenyls (PCBs), and radioactive materials can reach dangerous levels of accumulation as they are passed up the food chain into the bodies of progressively larger animals. For example, molecules of toxic compounds may collect on the surface of aquatic plants without doing much damage to the plants. A small fish that grazes on these plants accumulates a high concentration of the toxin. Larger fish or other carnivores that eat the small fish will accumulate even greater, and possibly life-threatening, concentrations of the compound. This process is known as bioaccumulation.

Impact

Because humans are at the top of the food chain, they are particularly vulnerable to the effects of non degradable pollutants. This was clearly illustrated in the 1950s and 1960s when residents living near Minamata Bay, Japan, developed nervous disorders, tremors, and paralysis in a mysterious epidemic. More than 400 people died before authorities discovered that a local industry had released mercury into Minamata Bay. This highly toxic element accumulated in the bodies of local fish and eventually in the bodies of people who consumed the fish. More recently research has revealed that many chemical pollutants, such as DDT and PCBs, mimic sex hormones and interfere with the human body’s reproductive and developmental functions. These substances are known as endocrine disrupters.

Pollution also has a dramatic effect on natural resources. Ecosystems such as forests, wetlands, coral reefs, and rivers perform many important services for Earth’s environment. They enhance water and air quality, provide habitat for plants and animals, and provide food and medicines. Any or all of these ecosystem functions may be impaired or destroyed by pollution. Moreover, because of the complex relationships among the many types of organisms and ecosystems, environmental contamination may have far-reaching consequences that are not immediately obvious or that are difficult to predict. For instance, scientists can only speculate on some of the potential impacts of the depletion of the ozone layer, the protective layer in the atmosphere that shields Earth from the Sun’s harmful ultraviolet rays.


Another major effect of pollution is the tremendous cost of pollution cleanup and prevention. The global effort to control emissions of carbon dioxide, a gas produced from the combustion of fossil fuels such as coal or oil, or of other organic materials like wood, is one such example. The cost of maintaining annual national carbon dioxide emissions at 1990 levels is estimated to be 2 percent of the gross domestic product for developed countries.

In addition to its effects on the economy, health, and natural resources, pollution has social implications. Research has shown that low-income populations and minorities do not receive the same protection from environmental contamination as do higher-income communities. Toxic waste incinerators, chemical plants, and solid waste dumps are often located in low-income communities because of a lack of organized, informed community involvement in municipal decision-making processes.

Climate change and Global warming Climate is the average weather of an area. It is the general weather conditions, seasonal variations and extremes of weather in a region. Such condition which average over a long period-at least 30 years is called climate. The Inter governmental Panel on Climate Change (IPCC) in1990 and 1992 published best available evidence about past climate change, the green house effect and recent changes in global temperature. It is observed that earth’s temperature has changed considerably during the geological times. It has experienced several glacial and inter-glacial periods. However, during the past 10,000 years of the current interglacial period the mean average temperature has fluctuated by 0.5-1°C over 100 to 200 year period. We have relatively stable climate for thousands of years due to which we have practised agriculture and in-creased in population. Even small changes in climatic conditions may disturb agriculture that would lead to migration of animals including humans. Anthropogenic (man-made) activities are upsetting the delicate balance that has established between various components of the environment. Green house gases are increasing in the atmosphere resulting in increase in the average global temperature. This may upset the hydrological cycle, results in floods and droughts in different regions of the world, cause sea level rise, changes in agriculture productivity, famines and death of humans as well as live stock. The global change in temperature will not be uniform everywhere and will fluctuate in different regions. The places at higher latitudes will be warmed up more during late autumn and winter than the places in tropics. Poles may experience 2 to 3 times more warming than the global average, while warming in the tropics maybe only 50 to 100%on an average. The increased warming at poles will reduce the thermal gradient between the equator and high latitude regions decreasing the energy available to the heat engine that drives the global weather machine. This will disturb the global pattern of winds and ocean currents as well as the timing and distribution of rainfall. Shifting of ocean currents may change the climate of Iceland and Britain and may result in cooling at a time when rest of the world warms. By a temperature increase of 1.5 to 4.5°C the global hydrological cycle is expected to intensify by 5 to 10%. Disturbed rainfall will result in some areas becoming wetter and the others drier. Although rainfall may increase, higher temperatures will result in more evapotranspiration leading to annual water deficit in crop fields.


Troposphere, the lowermost layer of the atmosphere, traps heat by a natural process due to the presence of certain gases. This effect is called Green House Effect as it is similar to the warming effect observed in the horticultural greenhouses made of glass. The amount of heat trapped in the atmosphere depends mostly on the concentrations of heat trapping or green house gases and the length of time they stay in the atmosphere. The major green house gases are carbon dioxide, ozone, methane, nitrous oxide, chlorofluorocarbons (CFCs) and water vapours. The average global temperature is 15°C.In the absence of green house gases this temperature would have been –18°C.Therefore, Green House Effect contributes a temperature rise to the tune of33°C.Heat trapped by green house gases in the atmosphere keeps the planet warm enough to allow us and other species to exist. The two predominant green house gases are water vapours, which are controlled by hydrological cycle, and carbon dioxide, which is controlled mostly by the global carbon cycle. While the levels of water vapour in the troposphere have relatively remained constant, the levels of carbon dioxide have increased. Other gases whose levels have increased due to human activities are methane, nitrous oxide and chlorofluorocarbons. Deforestation has further resulted in elevated levels of carbon dioxide due to non removal of carbon dioxide by plants through photosynthesis. Warming or cooling by more than 2° C over the past few decades may prove to be disastrous for various ecosystems on the earth including humans, as it would alter the conditions faster than some species could adapt or migrate. Some areas will become inhabitable because of drought or floods following rise in average sea level.

Fig-1, Green House Effect

Greenhouse Gases

The phenomenon that worries the environmental scientists is that due to anthropogenic activities there is an increase in the concentration of the greenhouse gases in the air that absorb infra-red light containing heat and results in the re-radiation of even more of the outgoing thermal infra-red energy, thereby increasing the average surface temperature beyond 15°C. The phenomenon is referred to as the enhanced green house effect to distinguish its effect from the one that has been operating naturally for millennia.


The greenhouse gases present in the troposphere and resulting in an increase in the temperature of air and the earth are discussed here:

Carbon dioxide

It contributes about 55% to global warming from green house gases produced by human activity. Industrial countries account for about 76% of annual emissions. The main sources are fossil fuel burning (67%) and deforestation, other forms of land clearing and burning (33%). CO2 stays in the atmosphere for about 500 years. CO2 concentration in the atmosphere was 355 ppm in 1990 that is increasing at a rate of 1.5 ppm every year.

Chlorofluorocarbons (CFCs)

These are believed to be responsible for 24% of the human contribution to greenhouse gases. They also deplete ozone in the stratosphere. The main sources of CFCs include leaking air conditioners and refrigerators, evaporation of industrial solvents, production of plastic foams, aerosols, propellants etc. CFCs take 10-15 years to reach the stratosphere and generally trap1500 to 7000 times more heat per molecule than CO2 while they are in the troposphere. This heating effect in the troposphere may be partially offset by the cooling caused when CFCs deplete ozone during their 65 to 110 years stay in the stratosphere. Atmospheric concentration of CFC is 0.00225 ppm that is increasing at a rate of 0.5% annually. Methane (CH4)It accounts for 18% of the increased greenhouse gases. Methane is produced when bacteria break down dead organic matter in moist places that lack oxygen such as swamps, natural wetlands, paddy fields, landfills and digestive tracts of cattle, sheep and termites. Production and use of oil and natural gas and incomplete burning of organic material are also significant sources of methane. Methane stays in the atmosphere for 7-10 years. Each methane molecule traps about 25 times as much heat as a CO2 molecule. Atmospheric concentration of methane is 1.675ppm and it is increasing at a rate of 1% annually. Nitrous Oxide (N2O) It is responsible for 6% of the human input of green house gases. Besides trapping heat in the troposphere it also depletes ozone in the stratosphere. It is released from nylon products, from burning of biomass and nitrogen rich fuels (especially coal ) and from the breakdown of nitrogen fertilizers in soil, livestock wastes and nitrate contaminated ground water. Its life span in the troposphere is 140-190 years and it traps about 230 times as much heat per molecule as CO2. The atmospheric concentration of N2O is 0.3 ppm and is increasing at a rate of0.2% annually.

Impacts of enhanced greenhouse effect

The enhanced greenhouse effect will not only cause global warming but will also affect various other climatic and natural processes

(1) Global temperature increase: It is estimated that the earth’s mean temperature will rise between 1.5 to 5.5°C by 2050 if input of greenhouse gases continues to rise at the present rate. Even at the lower value, earth would be warmer than it has been for 10,000 years.

(2) Rise in Sea Level: With the increase in global temperature sea water will expand. Heating will melt the polar ice sheets and glaciers resulting in further rise in sea level. Current models indicate that an increase in the average atmospheric temperature of 3°C would raise the average global sea level by 0.2–1.5 meters over the next 50-100years. One meter rise in sea level will inundate low lying areas of cities like Shanghai, Cairo, Bangkok, Sydney, Hamburg and Venice as well as agricultural lowlands and deltas in Egypt, Bangladesh, India and China will affect rice productivity. This will also disturb many commercially important spawning grounds, and would probably increase the frequency of storm


damage to lagoons, estuaries and coral reefs. In India, the Lakshadweep Islands with a maximum height of 4 meters above the level may be vulnerable. Some of the most beautiful cities like Mumbai may be saved by heavy investment on embankment to prevent inundation. Life of millions of people will be affected, by the sea level rise who has built homes in the deltas of the Ganges, the Nile, the Mekong, the Yangtze and the Mississippi river.

(3) Effects on Human Health: The global warming will lead to changes in the rainfall pattern in many areas, there by affecting the distribution of vector-borne diseases like malaria, filariasis, elephantiasis etc. Areas which are presently free from diseases like malaria; schistosomiasis etc. may become the breeding grounds for the vectors of such diseases. The areas likely to be affected in this manner are Ethiopia, Kenya and Indonesia. Warmer temperature and more water stagnation would favour the breeding of mosquitoes, snails and some insects, which are the vectors of such diseases. Higher temperature and humidity will increase/aggravate respiratory and skin diseases.

(4) Effects on Agriculture: There are different views regarding the effect of global warming on agriculture. It may show positive or negative effects on various types of crops in different regions of the world. Tropical and subtropical regions will be more affected since the average temperature in these regions is already on the higher side. Even a rise of 2°C may be quite harmful to crops. Soil moisture will decrease and evapotranspiration will increase, which may drastically affect wheat and maize production. Increase in temperature and humidity will increase pest growth like the growth of vectors for various diseases. Pests will adapt to such changes better than the crops. To cope up with the changing situation drought resistant, heat resistant and pest resistant varieties of crops have to be developed.

Measures to Check Global Warming

To slow down enhanced global warming the following steps will be important:

(1) Cut down the current rate of use of CFCs and fossil fuel.

(2) Use energy more efficiently.

(3) Shift to renewable energy resources.

(4) Increase Nuclear Power Plants for electricity production.

(5) Shift from coal to natural gas.

(6) Trap and use methane as a fuel.

(7) Adopt sustainable agriculture.

(8) Stabilize population growth.

(9) Efficiently remove CO2 from smoke stacks.

(10) Plant more trees.

(11) Remove atmospheric CO2 by utilizing photosynthetic algae.


Acid Rain

Acid rain is a phenomenon in which airborne acids produced by industrial operations and fossil fuel combustion fall to Earth in distant regions. The corrosive nature of acid rain causes widespread damage to the environment. The problem begins with the production of sulphur dioxide and nitrogen oxides from the burning of fossil fuels, such as coal, natural gas, and oil, and from certain kinds of manufacturing. Sulphur dioxide and nitrogen oxides react with water and other chemicals in the air to form sulphuric acid, nitric acid, and other pollutants. These acid pollutants reach high into the atmosphere, travel with the wind for hundreds of miles, and eventually return to the ground by way of rain, snow, or fog, and as invisible “dry” forms.

Damage from acid rain has been widespread in eastern North America and throughout Europe, and in Japan, China, and Southeast Asia. Acid rain leaches nutrients from soils, slows the growth of trees, and makes lakes uninhabitable for fish and other wildlife. In cities, acid pollutants corrode almost everything they touch, accelerating natural wear and tear on structures such as buildings and statues. Acids combine with other chemicals to form urban smog, which attacks the lungs, causing illness and premature deaths.

Formation of Acid rain

The process that leads to acid rain begins with the burning of fossil fuels. Burning, or combustion, is a chemical reaction in which oxygen from the air combines with carbon, nitrogen, sulphur, and other elements in the substance being burned. The new compounds formed are gases called oxides. When sulphur and nitrogen are present in the fuel their reaction with oxygen yields sulphur dioxide and various nitrogen oxide compounds. In the United States, 70 percent of sulphur dioxide pollution comes from power plants, especially those that burn coal. In Canada, industrial activities, including oil refining and metal smelting, account for 61 percent of sulphur dioxide pollution. Nitrogen oxides enter the atmosphere from many sources, with motor vehicles emitting the largest share—43 percent in the United States and 60 percent in Canada.

Once in the atmosphere, sulphur dioxide and nitrogen oxides undergo complex reactions with water vapour and other chemicals to yield sulphuric acid, nitric acid, and other pollutants called nitrates and sulphates. The acid compounds are carried by air currents and the wind, sometimes over long distances. When clouds or fog form in acid-laden air, they too are acidic, and so is the rain or snow that falls from them.

Acid pollutants also occur as dry particles and as gases, which may reach the ground without the help of water. When these “dry” acids are washed from ground surfaces by rain, they add to the acids in the rain itself to produce a still more corrosive solution. The combination of acid rain and dry acids is known as acid deposition.

Effect of Acid Rain

The acids in acid rain react chemically with any object they contact. Acids are corrosive chemicals that react with other chemicals by giving up hydrogen atoms. The acidity of a substance comes from


the abundance of free hydrogen atoms when the substance is dissolved in water. Acidity is measured using a pH scale with units from 0 to 14. Acidic substances have pH numbers from 1 to 6—the lower the pH number, the stronger, or more corrosive, the substance. Some non acidic substances, called bases or alkalis, are like acids in reverse—they readily accept the hydrogen atoms that the acids offer. Bases have pH numbers from 8 to 14, with the higher values indicating increased alkalinity. Pure water has a neutral pH of 7—it is not acidic or basic. Rain, snow, or fog with a pH below 5.6 is considered acid rain.

When bases mix with acids, the bases lessen the strength of an acid. This buffering action regularly occurs in nature. Rain, snow, and fog formed in regions free of acid pollutants are slightly acidic, having a pH near 5.6. Alkaline chemicals in the environment, found in rocks, soils, lakes, and streams, regularly neutralize this precipitation. But when precipitation is highly acidic, with a pH below 5.6, naturally occurring acid buffers become depleted over time, and nature’s ability to neutralize the acids is impaired. Acid rain has been linked to widespread environmental damage, including soil and plant degradation, depleted life in lakes and streams, and erosion of human-made structures.

Soil

In soil, acid rain dissolves and washes away nutrients needed by plants. It can also dissolve toxic substances, such as aluminium and mercury, which are naturally present in some soils, freeing these toxins to pollute water or to poison plants that absorb them. Some soils are quite alkaline and can neutralize acid deposition indefinitely; others, especially thin mountain soils derived from granite or gneiss, buffer acid only briefly.

Trees

By removing useful nutrients from the soil, acid rain slows the growth of plants, especially trees. It also attacks trees more directly by eating holes in the waxy coating of leaves and needles, causing brown dead spots. If many such spots form, a tree loses some of its ability to make food through photosynthesis. Also, organisms that cause disease can infect the tree through its injured leaves. Once weakened, trees are more vulnerable to other stresses, such as insect infestations, drought, and cold temperatures.

Spruce and fir forests at higher elevations, where the trees literally touch the acid clouds, seem to be most at risk. Acid rain has been blamed for the decline of spruce forests on the highest ridges of the Appalachian Mountains in the eastern United States. In the Black Forest of south western Germany, half of the trees are damaged from acid rain and other forms of pollution.

Agriculture

Most farm crops are less affected by acid rain than are forests. The deep soils of many farm regions, such as those in the Midwestern United States, can absorb and neutralize large amounts of acid. Mountain farms are more at risk—the thin soils in these higher elevations cannot neutralize so much acid. Farmers can prevent acid rain damage by monitoring the condition of the soil and, when necessary, adding crushed limestone to the soil to neutralize acid. If excessive amounts of nutrients have been leached out of the soil, farmers can replace them by adding nutrient-rich fertilizer.


Surface Water

Acid rain falls into and drains into streams, lakes, and marshes. Where there is snow cover in winter, local waters grow suddenly more acidic when the snow melts in the spring. Most natural waters are close to chemically neutral, neither acidic nor alkaline: their pH is between 6 and 8. In the north eastern United States and south eastern Canada, the water in some lakes now has a pH value of less than 5 as a result of acid rain. This means they are at least ten times more acidic than they should be. In the Adirondack Mountains of New York State, a quarter of the lakes and ponds are acidic, and many have lost their brook trout and other fish. In the middle Appalachian Mountains, over 1,300 streams are afflicted. All of Norway’s major rivers have been damaged by acid rain, severely reducing salmon and trout populations.

Plants and animals

The effects of acid rain on wildlife can be far-reaching. If a population of one plant or animal is adversely affected by acid rain, animals that feed on that organism may also suffer. Ultimately, an entire ecosystem may become endangered. Some species that live in water are very sensitive to acidity, some less so. Freshwater clams and mayfly young, for instance, begin dying when the water pH reaches 6.0. Frogs can generally survive more acidic water, but if their supply of mayflies is destroyed by acid rain, frog populations may also decline. Fish eggs of most species stop hatching at a pH of 5.0. Below a pH of 4.5, water is nearly sterile, unable to support any wildlife.

Land animals dependent on aquatic organisms are also affected. Scientists have found that populations of snails living in or near water polluted by acid rain are declining in some regions. In The Netherlands songbirds are finding fewer snails to eat. The eggs these birds lay have weakened shells because the birds are receiving less calcium from snail shells.

Human made structures

Acid rain and the dry deposition of acidic particles damage buildings, statues, automobiles, and other structures made of stone, metal, or any other material exposed to weather for long periods. The corrosive damage can be expensive and, in cities with very historic buildings, tragic. Both the Parthenon in Athens, Greece, and the Taj Mahal in Agra, India, are deteriorating due to acid pollution.

Human health

The acidification of surface waters causes little direct harm to people. It is safe to swim in even the most acidified lakes. However, toxic substances leached from soil can pollute local water supplies. In Sweden, as many as 10,000 lakes have been polluted by mercury released from soils damaged by acid rain, and residents have been warned to avoid eating fish caught in these lakes. In the air, acids join with other chemicals to produce urban smog, which can irritate the lungs and make breathing difficult, especially for people who already have asthma, bronchitis, or other respiratory diseases. Solid particles of sulphates, a class of minerals derived from sulphur dioxide, are thought to be especially damaging to the lungs.

Acid rain and global warming


Acid pollution has one surprising effect that may be beneficial. Sulphates in the upper atmosphere reflect some sunlight out into space, and thus tend to slow down global warming. Scientists believe that acid pollution may have delayed the onset of warming by several decades in the middle of the 20th century.

Efforts to control acid rain

Figure-2, Anatomy of an Air Scrubber A venturi air scrubber removes polluting particles from gas emissions by spraying a scrubber liquid directly into the emissions. The scrubber liquid surrounds the dirty particles, which are carried with the gas emissions into the separator cylinder. As the gas cycles upward through the cylinder, the liquid-covered particles drop from the gas into the contaminated liquid reservoir.

Acid rain can best be curtailed by reducing the amount of sulphur dioxide and nitrogen oxides released by power plants, motorized vehicles, and factories. The simplest way to cut these emissions is to use less energy from fossil fuels. Individuals can help. Every time a consumer buys an energy-efficient appliance, adds insulation to a house, or takes a bus to work, he or she conserves energy and, as a result, fights acid rain.

Another way to cut emissions of sulphur dioxide and nitrogen oxides is by switching to cleaner-burning fuels. For instance, coal can be high or low in sulphur, and some coal contains sulphur in a form that can be washed out easily before burning. By using more of the low- sulphur or cleanable types of coal, electric utility companies and other industries can pollute less. The gasoline and diesel oil that run most motor vehicles can also be formulated to burn more cleanly, producing less nitrogen oxide pollution. Clean-burning fuels such as natural gas are being used increasingly in vehicles. Natural gas contains almost no sulphur and produces very low nitrogen oxides. Unfortunately, natural


gas and the less-polluting coals tend to be more expensive, placing them out of the reach of nations that are struggling economically.

Pollution can also be reduced at the moment the fuel is burned. Several new kinds of burners and boilers alter the burning process to produce less nitrogen oxides and more free nitrogen, which is harmless. Limestone or sandstone added to the combustion chamber can capture some of the sulphur released by burning coal.

Once sulphur dioxide and oxides of nitrogen have been formed, there is one more chance to keep them out of the atmosphere. In smokestacks, devices called scrubbers spray a mixture of water and powdered limestone into the waste gases (flue gases), recapturing the sulphur. Pollutants can also be removed by catalytic converters. In a converter, waste gases pass over small beads coated with metals. These metals promote chemical reactions that change harmful substances to less harmful ones. In the United States and Canada, these devices are required in cars, but they are not often used in smokestacks.

Once acid rain has occurred, a few techniques can limit environmental damage. In a process known as liming, powdered limestone can be added to water or soil to neutralize the acid dropping from the sky. In Norway and Sweden, nations much afflicted with acid rain, lakes are commonly treated this way. Rural water companies may need to lime their reservoirs so that acid does not eat away water pipes. In cities, exposed surfaces vulnerable to acid rain destruction can be coated with acid-resistant paints. Delicate objects like statues can be sheltered indoors in climate-controlled rooms.

Cleaning up sulphur dioxide and nitrogen oxides will reduce not only acid rain but also smog, which will make the air look clearer. Based on a study of the value that visitors to national parks place on clear scenic vistas, the U.S. Environmental Protection Agency thinks that improving the vistas in eastern national parks alone will be worth $1 billion in tourist revenue a year.

International agreements

Acid rain typically crosses national borders, making pollution control an international issue. Canada receives much of its acid pollution from the United States—by some estimates as much as 50 percent. Norway and Sweden receive acid pollutants from Britain, Germany, Poland, and Russia. The majority of acid pollution in Japan comes from China. Debates about responsibilities and cleanup costs for acid pollutants led to international cooperation. In 1988, as part of the Long-Range Trans boundary Air Pollution Agreement sponsored by the United Nations, the United States and 24 other nations ratified a protocol promising to hold yearly nitrogen oxide emissions at or below 1987 levels. In 1991 the United States and Canada signed an Air Quality Agreement setting national limits on annual sulphur dioxide emissions from power plants and factories. In 1994 in Oslo, Norway, 12 European nations agreed to reduce sulphur dioxide emissions by as much as 87 percent by 2010.

Legislative actions to prevent acid rain have results. The targets established in laws and treaties are being met, usually ahead of schedule. Sulphur emissions in Europe decreased by 40 percent from 1980 to 1994. In Norway sulphur dioxide emissions fell by 75 percent during the same period. Since 1980 annual sulphur dioxide emissions in the United States have dropped from 26 million tons to 18.3


million tons. Canada reports sulphur dioxide emissions have been reduced to 2.6 million tons, 18 percent below the proposed limit of 3.2 million tons.

Monitoring stations in several nations report that precipitation is actually becoming less acidic. In Europe, lakes and streams are now growing less acid. However, this does not seem to be the case in the United States and Canada. The reasons are not completely understood, but apparently, controls reducing nitrogen oxide emissions only began recently and their effects have yet to make a mark. In addition, soils in some areas have absorbed so much acid that they contain no more neutralizing alkaline chemicals. The weathering of rock will gradually replace the missing alkaline chemicals, but scientists fear that improvement will be very slow unless pollution controls are made even stricter.

Ozone Layer Depletion

Ozone Layer is a region of the atmosphere from 19 to 48 km (12 to 30 mi) above Earth's surface. Ozone concentrations of up to 10 parts per million occur in the ozone layer. The ozone forms there by the action of sunlight on oxygen. This action has been taking place for many millions of years, but naturally occurring nitrogen compounds in the atmosphere apparently have kept the ozone concentration at a fairly stable level.

The ozone layer of the atmosphere protects life on Earth by absorbing harmful ultraviolet radiation from the Sun. If all the ultraviolet radiation given off by the Sun were allowed to reach the surface of Earth, most of the life on Earth’s surface would probably be destroyed. Short wavelengths of ultraviolet radiation, such as UV-A, B, and C, are damaging to the cell structure of living organisms. Fortunately, the ozone layer absorbs almost all of the short-wavelength ultraviolet radiation and much of the long-wavelength ultraviolet radiation given off by the Sun.

In the 1970s scientists became concerned when they discovered that chemicals called chlorofluorocarbons or CFCs—long used as refrigerants and as aerosol spray propellants—posed a possible threat to the ozone layer. Released into the atmosphere, these chlorine-containing chemicals rise into the upper stratosphere and are broken down by sunlight, whereupon the chlorine reacts with and destroys ozone molecules—up to 100,000 per CFC molecule. The use of CFCs in aerosols has been banned in the United States and elsewhere. Other chemicals, such as bromine halocarbons, as well as nitrous oxides from fertilizers, may also attack the ozone layer. Thinning of the ozone layer is predicted to cause increases in skin cancer and cataracts, damage to certain crops and to plankton and the marine food web, and an increase in atmospheric carbon dioxide (see Global Warming) due to the decrease in plants and plankton.

Beginning in the early 1980s, research scientists working in Antarctica began to detect a periodic loss of ozone in the atmosphere high above that continent. The so-called ozone “hole,” a thinned region of the ozone layer, develops in the Antarctic spring and continues for several months before thickening again. Studies conducted with high-altitude balloons and weather satellites indicated that the overall percentage of ozone in the Antarctic ozone layer is actually declining. Measurements over the Arctic regions indicated that a similar problem was developing there.

In 1985 the Vienna Convention for the Protection of the Ozone Layer was adopted. In 1987 a protocol under the Vienna Convention, known as the Montréal Protocol, was signed and later ratified by 36 nations, including the United States. A total ban on the use of CFCs during the 1990s was proposed by the European Community (now called the European Union) in 1989, a move endorsed by U.S. President George H. W. Bush. In December 1995 over 100 nations agreed to phase out developed countries' production of the pesticide methyl bromide by the year 2000. The pesticide was estimated


to cause about 15 percent of the ozone depletion. Production of CFCs in developed countries ceased at the end of 1995 and was to be phased out in developing countries by 2010.

Hydro chlorofluorocarbons, or HCFCs, which cause less damage to the ozone layer than CFCs do, began to be used as substitutes for CFCs following the adoption of the Montréal Protocol. HCFCs were to be used on an interim basis until 2030 in developed countries and until 2040 in developing countries. In addition, the United States passed legislation that would ban the production of the refrigerant HCFC-22, widely used in air conditioners, by 2010. Other industrialized nations also adopted measures to end HCFC-22 production prior to 2020. But production of HCFC-22 in developing nations was estimated in 2007 to be increasing at a rate of 20 to 35 percent each year.

Concerned about the increasing use of HCFCs, the United Nations Environment Program met again in September 2007 in Montréal, where more than 200 countries agreed to speed up the timetable for phasing out the use of HCFCs. Under the new agreement, developing countries would end all use of HCFCs by 2030, ten years earlier than previously agreed, and developed countries would end all use by 2020.

To monitor ozone depletion on a global level, in 1991 the National Aeronautics and Space Administration (NASA) launched the 7-ton Upper Atmosphere Research Satellite. Orbiting Earth at an altitude of 600 km (372 mi), the spacecraft measures ozone variations at different altitudes and provides thorough measurements of upper atmosphere chemistry.

The World Meteorological Organization (WMO), a specialized agency of the United Nations (UN), helps support the implementation of the Vienna Convention to protect the ozone layer. During the winter of 1995-1996 the WMO observed a 45 percent depletion of the ozone layer over one-third of the northern hemisphere, from Greenland to western Siberia, for several days. The deficiency was believed to have been caused by chlorine and bromine compounds combined with polar stratospheric clouds formed under unusually low temperatures.

The ozone hole over Antarctica reached a record size in 2001, the same year that the presence of CFCs in the atmosphere was thought to have peaked. Due to the international treaty to phase out production of CFCs, many scientists expected the ozone layer would begin to recover after the record thinning of 2001. To their surprise, however, measurements in 2006 indicated that the ozone hole had once again reached a record size. Most scientists attributed the increase in the ozone hole in 2006 to an unusually cold Antarctic winter. A study the same year by the WMO and the United Nations Environment Program, however, found that the ozone layer was recovering more slowly than predicted. This finding was expected to trigger an effort in 2007 to phase out the production of HCFC-22 more rapidly than previously planned.

Biodiversity Degradation

The variety of life on Earth, its biological diversity, is commonly referred to as biodiversity. The number of species of plants, animals, and microorganisms, the enormous diversity of genes in these species, the different ecosystems on the planet, such as deserts, rainforests and coral reefs are all part of a biologically diverse Earth. Appropriate conservation and sustainable development strategies attempt to recognize this as being integral to any approach. In some way or form, almost all cultures have recognized the importance of nature and its biological diversity for their societies and have therefore understood the need to maintain it. Yet, power, greed and politics have affected the precarious balance and have given birth to this crisis.


Biodiversity boosts ecosystem productivity where each species, no matter how small, all have an important role to play. For example, a larger number of plant species means a greater variety of crops; greater species diversity ensures natural sustainability for all life forms; and healthy ecosystems can better withstand and recover from a variety of disasters. And so, while we dominate this planet, we still need to preserve the diversity in wildlife.

It has long been feared that human activity is causing massive extinctions. Despite increased efforts at conservation, it has not been enough and biodiversity losses continue. The costs associated with deteriorating or vanishing ecosystems will be high. However, sustainable development and consumption would help avert ecological problems. The link between climate change and biodiversity has long been established. Although throughout Earth’s history the climate has always changed with ecosystems and species coming and going, rapid climate change affects ecosystems and species ability to adapt and so biodiversity loss increases. Biodiversity and Climate Change, Convention on Biological Diversity, December, 2009 From a human perspective, the rapid climate change and accelerating biodiversity loss risks human security (e.g. a major change in the food chain upon which we depend, water sources may change, recede or disappear, medicines and other resources we rely on may be harder to obtain as the plants and flora they are derived from may reduce or disappear, etc.).

Preservation Efforts

In an effort to protect global biodiversity and encourage the study, restoration, and sound management of endangered species, the IUCN and the World Conservation Monitoring Centre (WCMC) maintain a global list of endangered and vulnerable animal species called the Red List. A framework for international conservation efforts, the Red List database assesses the status of, and threats to, animal species worldwide. To add to this and other biodiversity databases, nongovernmental organizations such as Conservation International and World Wildlife Fund conduct periodic rapid assessments (focused, intensive evaluations) of biodiversity in various hotspots—regions like Madagascar that are both rich in endemic species and environmentally threatened.

This information is used in the administration of international agreements such as the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), signed by 125 nations in 1973 and put into effect in 1975. The purpose of CITES is to restrict exploitation of endangered plants and wildlife by regulating and restricting their trade. Despite legal protection, however, the future of many species, such as the African black rhinoceros, is in doubt because of poor law enforcement and the activities of poachers and dealers who supply the lucrative trade in endangered animals and animal parts. Similarly, the International Whaling Commission is charged with protecting global whale populations, but lacks the authority to enforce its rulings.

Several private and governmental efforts in the United States have been mobilized to save endangered species. One immediate approach is to protect a species by legislation. The Lacey Act of 1900 was enacted to protect wildlife from commercial trade and overhunting. The Marine Mammal Protection Act of 1972 banned the killing and importing of whales and nearly all marine mammals. In addition to promoting species and habitat protection in the United States, the Endangered Species Act (ESA) discouraged the exploitation of endangered species in other countries by banning the importation and trade of any products, such as elephant-tusk ivory, obtained from such species. Although the ESA is one of the most progressive national wildlife protection laws ever enacted, it is constantly threatened by development industries unhappy with the government restrictions. Pressure from developers and


from logging and mining interests also led to government efforts to roll back or circumvent ESA restrictions during the early 2000s.

The United States also has various agreements with other nations like Canada and Mexico for the legal protection of migratory birds. These include the Migratory Bird Treaty Act of 1918, the Migratory Bird Conservation Act of 1929, and the North American Waterfowl Management Plan of 1986. Canadian laws designed to protect endangered species include the Migratory Birds Convention Act of 1917, the Canadian Endangered Species Protection Act of 1996, and the Wild Animal and Plant Protection and Regulation of International and Interprovincial Trade Act of 1996.

Efforts to save endangered species also include captive breeding of severely endangered species later released in the wild to restore or add to a breeding population (a population of individuals capable of reproducing). Due to breeding in captivity (such as in zoos and specialized animal clinics), the number of known California condors, whooping cranes, and peregrine falcons has increased over the last 20 years. Genetic cloning techniques may one day help forestall extinction for endangered species that reproduce poorly on their own.

Captive breeding and cloning programs are considered a last resort, however, because such breeding may reduce the genetic diversity of the species and its ability to survive in the wild. For example, Pacific salmon raised in hatcheries may be less capable of surviving in adverse conditions than wild salmon, and if they interbreed with the wild fish, they may dilute the natural survival ability of wild salmon. Extremely difficult to successfully reintroduce to the wild, captive-bred animals are also more likely to carry disease, which they may transmit to the wild population. These programs are also extremely costly, sometimes reaching $500,000 per year per species. Moreover, captive breeding and cloning programs are a short-term repair that may divert attention from finding solutions to the original causes of the species decline, such as habitat destruction or toxic pollution. For some species, however, such as the California condor and the peregrine falcon, captive breeding has made the difference between survival and extinction.

The current global extinction crisis is one of the greatest challenges posed by the rapid growth and expansion of human populations. The protection of endangered species and habitats should be a top priority for international organizations, governmental agencies, industry, and individuals if there is hope for preserving the earth’s valuable biodiversity for future generations.

A United Nations Environment Program (UNEP) report on the global environment published in 2002 concluded that over 11,000 species (including almost a quarter of all mammals) face extinction within 30 years. In total more than 5,000 plants, 1,000 mammals, and 5,000 other animals (including one in eight birds) are endangered, mostly due to habitat destruction and invasion by nonnative species. The report states that factors that caused previous extinctions are operating with “ever-increasing intensity,” although it suggests that these problems could be eased if pacts such as the Convention on Biological Diversity and the Kyoto Protocol were implemented globally. The 1992 Convention on Biological Diversity seeks to maintain biodiversity, while the 1997 Kyoto Protocol seeks to curb emissions of greenhouse gases that contribute to global warming.


Land Degradation

Land degradation is a process in which the value of the biophysical environment is affected by one or more combination of human-induced processes acting upon the land. also environmental degradation is the gradual destruction or reduction of the quality and quantity of human activities animals activities or natural means example water causes soil erosion, wind, etc. It is viewed as any change or disturbance to the land perceived to be deleterious or undesirable. Natural hazards are excluded as a cause; however human activities can indirectly affect phenomena such as floods and bush fires.

This is considered to be an important topic of the 21st century due to the implications land degradation has upon agronomic productivity, the environment, and its effects on food security. It is estimated that up to 40% of the world's agricultural land is seriously degraded.

Land degradation is a broad term that can be applied differently across a wide range of scenarios. There are four main ways of looking at land degradation and its impact on the environment around it

1. A temporary or permanent decline in the productive capacity of the land. This can be seen through a loss of biomass, a loss of actual productivity or in potential productivity, or a loss or change in vegetative cover and soil nutrients.

2. A decline in the lands “usefulness”: A loss or reduction in the lands capacity to provide resources for human livelihoods. This can be measured from a base line of past land use.

3. Loss of biodiversity: A loss of range of species or ecosystem complexity as a decline in the environmental quality.

4. Shifting ecological risk: increased vulnerability of the environment or people to destruction or crisis. This is measured through a base line in the form of pre-existing risk of crisis or destruction.

A problem with measuring land degradation is that what one group of people call degradation, others might view as a benefit or opportunity. For example, heavy rainfall could make a scientific group be worried about high erosion of the soil while farmers could view it as a good opportunity to plant crops.

Causes

Land degradation is a global problem, largely related to agricultural use. The major causes include

• Land clearance, such as clear cutting and deforestation • Agricultural depletion of soil nutrients through poor farming practices • Livestock including overgrazing and over drafting • Inappropriate irrigation and over drafting • Urban sprawl and commercial development • Soil contamination including • Vehicle off-roading • Quarrying of stone, sand, ore and minerals • Increase in field size due to economies of scale, reducing shelter for wildlife, as hedgerows

and copses disappear • Exposure of naked soil after harvesting by heavy equipment • Monoculture, destabilizing the local ecosystem • Dumping of non-biodegradable trash, such as plastics


http://en.wikipedia.org/wiki/Clearcutting

http://en.wikipedia.org/wiki/Deforestation

http://en.wikipedia.org/wiki/Nutrient

http://en.wikipedia.org/wiki/Livestock

http://en.wikipedia.org/wiki/Overgrazing

http://en.wikipedia.org/wiki/Overdrafting

http://en.wikipedia.org/wiki/Irrigation

http://en.wikipedia.org/wiki/Overdrafting

http://en.wikipedia.org/wiki/Urban_sprawl

http://en.wikipedia.org/wiki/Soil_contamination

http://en.wikipedia.org/wiki/Off-roading

http://en.wikipedia.org/wiki/Quarry

http://en.wikipedia.org/wiki/Economies_of_scale

http://en.wikipedia.org/wiki/Biodegradable

http://en.wikipedia.org/wiki/Plastics

Effects

The main outcome of land degradation is a substantial reduction in the productivity of the land. The major stresses on vulnerable land include:

• Accelerated soil erosion by wind and water • Soil acidification and the formation of acid sulphate soil resulting in barren soil • Soil alkalinisation owing to irrigation with water containing sodium bicarbonate leading to

poor soil structure and reduced crop yields • Soil salination in irrigated land requiring soil salinity control to reclaim the land [8] • Soil water logging in irrigated land which calls for some form of subsurface land drainage to

remediate the negative effects • Destruction of soil structure including loss of organic matter

Overcutting of vegetation occurs when people cut forests, woodlands and shrub lands—to obtain timber, fuel wood and other products—at a pace exceeding the rate of natural re growth. This is frequent in semi-arid environments, where fuel wood shortages are often severe.

Overgrazing is the grazing of natural pastures at stocking intensities above the livestock carrying capacity; the resulting decrease in the vegetation cover is a leading cause of wind and water erosion. It is a significant factor in Afghanistan.

Agricultural activities that can cause land degradation include shifting cultivation without adequate fallow periods, absence of soil conservation measures, fertilizer use, and a host of possible problems arising from faulty planning or management of irrigation. They are a major factor in Sri Lanka and the dominant one in Bangladesh.

The role of population factors in land degradation processes obviously occurs in the context of the underlying causes. In the region, in fact, it is indeed one of the two along with land shortage, and land shortage itself ultimately is a consequence of continued population growth in the face of the finiteness of land resources. In the context of land shortage the growing population pressure, during 1980-1990, has led to decreases in the already small areas of agricultural land per person in six out of eight countries (14% for India and 22% for Pakistan).

Population pressure also operates through other mechanisms. Improper agricultural practices, for instance, occur only under constraints such as the saturation of good lands under population pressure which leads settlers to cultivate too shallow or too steep soils, plough fallow land before it has recovered its fertility, or attempt to obtain multiple crops by irrigating unsuitable soils.

High population density is not always related to land degradation. Rather, it is the practices of the human population that can cause a landscape to become degraded. Populations can be a benefit to the land and make it more productive than it is in its natural state. Land degradation is important factor of internal displacement in many African and Asian countries.

Severe land degradation affects a significant portion of the Earth's arable lands, decreasing the wealth and economic development of nations. As the land resource base becomes less productive, food security is compromised and competition for dwindling resources increases, the seeds of famine and potential conflict are sewn.


http://en.wikipedia.org/wiki/Soil_erosion

http://en.wikipedia.org/wiki/Soil_acidification

http://en.wikipedia.org/wiki/Acid_sulfate_soil

http://en.wikipedia.org/wiki/Alkaline_soil

http://en.wikipedia.org/wiki/Sodium_bicarbonate

http://en.wikipedia.org/wiki/Soil_structure

http://en.wikipedia.org/wiki/Soil_salination

http://en.wikipedia.org/wiki/Soil_salinity_control

http://en.wikipedia.org/wiki/Land_degradation#cite_note-Waterlog-8

http://en.wikipedia.org/wiki/Land_degradation#cite_note-Waterlog-8

http://en.wikipedia.org/wiki/Waterlogging_%28agriculture%29

http://en.wikipedia.org/wiki/Drainage_system_%28agriculture%29

http://en.wikipedia.org/wiki/Soil_structure

http://en.wikipedia.org/wiki/Organic_matter

http://en.wikipedia.org/wiki/Shifting_cultivation

http://en.wikipedia.org/wiki/Economic_development

http://en.wikipedia.org/wiki/Food_security

http://en.wikipedia.org/wiki/Food_security

http://en.wikipedia.org/wiki/Resource

http://en.wikipedia.org/wiki/Famine

Nuclear Fallout and Hazards

Radioactive Fallout, deposition on the surface of the earth of radioactive particles, released into the atmosphere as a result of nuclear explosions and by discharge from nuclear-power and atomic installations (see Nuclear Energy; Nuclear Weapons; Radioactivity). Public interest has centered particularly on the effects of fallout from the period of large-scale atmospheric nuclear-weapons testing in the 1950s and early '60s. Various allegations of resulting ill effects were made for many years, but only in 1984 was a landmark decision reached when a federal judge in Utah ruled that 10 persons had suffered from cancer because of government negligence concerning public exposure to fallout in that state. Another decision was reached in 1985 by the Pensions Appeal Tribunals of England and Wales with respect to a veteran of British atomic tests on Kiritimati (Christmas Island) in the 1950s.

Since the signing of the limited test ban treaty in 1963, fallout levels have waned worldwide. Some fallout was produced by the USSR's Chernobyl' nuclear accident.

Mechanism of Fallout

Radioactive fallout material is produced through nuclear fission and the activation of soil, air, water, and other materials in the vicinity of the detonation.

Individual radioactive particles are invisible and so light that they might drift around the world endlessly without settling to earth. This condition could be achieved, however, only if a nuclear bomb were detonated at a considerable distance beyond the earth's atmosphere. When a nuclear weapon is exploded close to the earth's surface, the violence of the detonation pulverizes vast quantities of surface material, much of which is drawn into the fireball and subsequently sucked into the hot mass that rises to form the characteristic mushroom cloud. Inside the fireball and stem of the bomb cloud the radioactive particles become attached to heavier particles. These heavier particles then act as ballast.

The more massive bits of matter fall back to earth within a matter of minutes, forming an extremely localized fallout, which might be called fallback. Less massive but easily visible particles, borne downwind by the bomb cloud, fall within several hours, and are designated local fallout. The nature and extent of local fallout depend on the type and size of the explosion, the altitude of detonation, and the strength and direction of the winds.

Microscopic particles stay aloft for longer periods of time. If the bomb explosion is of small or medium power, the bomb cloud may not penetrate the tropopause, that is, the atmospheric layer between the troposphere and the stratosphere. In this case, known as tropospheric fallout, the bomb fragments are swept around the world in a zone at the latitude of the explosion and are brought to earth when rain and other forms of precipitation cleanse the foreign material from the atmosphere.

If the force of the detonation is sufficient to inject the bomb debris above the tropopause, many of the small particles remain in the stratosphere to be acted on by stratospheric winds. This is known as stratospheric, or global, fallout. Because no precipitation occurs in the stratosphere, these particles may remain there for considerable periods of time. They are scattered horizontally, so that some of the


particles, after having made a number of revolutions about the earth, are found throughout the stratosphere. Vertical mixing, especially in the polar regions during winter and early spring, brings the material into the troposphere, where it behaves as tropospheric fallout.

Persistence of Bomb Fallout

The fission fragments produced by the splitting of uranium atoms or plutonium atoms and neutron-activated materials make up approximately 300 different radioactive isotopes (see Isotope). Each radionuclide is characterized by its own half-life, that is, by the time required for half of the radioactive substance to undergo spontaneous decay. Within the first hour after the explosion, most of the extremely short-lived substances—that is, those with half-lives that are measured in seconds and minutes—decay, and the total radioactivity from the bomb decreases more than a hundredfold.

After the first hour the remaining radioactivity dissipates at a constantly slower pace. The longer-lived fission products account for the bulk of the residual radioactivity. A few fission products are extremely long-lived; for example, the radionuclide strontium-90 (symbol 90Sr), also known as radiostrontium, has a half-life of 28 years. These long-lived species constitute the long-term radiation hazard.

Biological effect of fallout

The long retention of bomb debris in the stratosphere allows time for some of the short-lived fission products to be dissipated in the atmosphere. In the case of tropospheric fallout, some radioactive decay occurs in the atmosphere, thereby reducing somewhat the radiation dosage to those exposed on the earth's surface.

Long-lived radionuclides, such as 90Sr, do not decay much during the time spent in the stratosphere, however, and therefore they may exist for many years as a potential hazard, primarily through contamination of the foods that are consumed by humans.

Strontium-90

Fig-3, Radiation Victims


A nuclear bomb releases radiation that can cause serious long-term injuries to individuals who survive the heat and blast of the initial explosion. Civilians of all ages were injured by the atomic bomb that the U.S. dropped on Nagasaki, Japan on August 9, 1945.

Radiostrontium is similar to calcium in its chemical behaviour, including its deposition in human bone. Most biological systems prefer calcium to strontium; therefore, the amount of 90Sr absorbed by plant roots and by animals depends on the availability of calcium. When 90Sr is deposited directly on plants during fallout, however, a greater amount is absorbed by the plants than if only root uptake were involved, and thus more 90Sr is available to animals and humans. Also, although milk is used as an indicator of 90Sr in foods, because it has a high calcium content the human body absorbs less 90Sr from milk than from foods of lower calcium content. Most other foods are derived from a number of geographical areas having variable rates for fallout deposition and soil accumulation of 90Sr. This fact, together with variations in growing seasons and soils, and modern food-production and distribution practices, causes dietary levels of 90Sr relative to calcium to be lower in some areas and higher in others than would be expected on the basis of the amounts of fallout.

Once 90Sr enters the body, part of it is excreted and the remainder is deposited in newly formed bone along with calcium. In young bone the 90Sr and calcium are continually being replaced as the bone grows. In adult bone little replacement occurs; little 90Sr is deposited and its removal is quite slow. The amount of 90Sr remaining in bone depends on the quantities of 90Sr and calcium in the diet during periods of bone growth. The long retention time of 90Sr in bone is the basis for its potential hazard. In animal experiments and in human cases of radium poisoning where sufficient amounts of radioactive material are deposited in bone, a higher incidence of leukemia and bone cancer is seen. Current levels of 90Sr in humans are far too low for such effects to be observed.

Other Radionuclides

Although radioactive iodine-131 is extremely short-lived (half-life, eight days), it is one of the important potential sources of internal radiation exposure because it is concentrated in the thyroid gland. Soon after a nuclear accident or explosion, grass bearing iodine-131 is consumed by cows; the isotope quickly appears in their milk. Because milk is commonly consumed within a few days of production, significant amounts of iodine -131 can be ingested by people who are unaware of the danger. Other foods are generally consumed after a longer interval, so radioactivity would have decreased. When large amounts of radioiodine accumulate in the thyroid, an increase in the incidence of thyroid cancer occurs; levels accumulated from fallout to date are too low, or exposure is too recent, for such an effect to be observed.

Cesium-137, which has a half-life of 30 years, also enters the food chain and thus the human body. Like potassium, which it resembles chemically, it is found throughout and irradiates the entire body. Radiocesium remains in the body only a few months, however. Carbon-14, which has a half-life of 5760 years, is produced primarily by activation of nitrogen atoms in the air during nuclear detonations. It is also produced naturally and continuously by actions of cosmic rays. It comes down to earth as carbon dioxide and as such is taken up by plants, eventually being distributed in all biological material. Radiocarbon, therefore, is another radionuclide that irradiates the entire body.


Cesium-137, carbon-14, and those nuclides deposited on the earth that irradiate the body from without contribute to a whole-body radiation dose. Such a dose is a potential hazard genetically, and also affects the body itself.

Genetic impacts of fallout

In evaluating the long-range results of fallout, it is essential to consider the genetic effects of radiation. Radiation may cause mutations, that is, changes in the reproductive cells that transmit inherited characteristics from one generation to the next. Practically all radiation-induced mutations are harmful, and the deleterious effects persist in successive generations.

Potential Risks

Evaluation of the risk of potential radiation hazards from fallout involves much the same considerations as do other risks to large populations. Such evaluations are complex and are necessarily relative to possible benefits and other risks. In the case of fallout, the potential risk is global and involves many uncertainties regarding radiation doses and effects; the changing international situation must be continually assessed. In 1959 the Federal Radiation Council was established to advise the president on radiation matters, including fallout. This office was abolished in 1970, and its functions transferred to the Environmental Protection Agency.

The fallout hazard in a nuclear war would be considerably more serious than in nuclear testing. Immediate lethal, as well as long-term, effects would then have to be considered. Studies of such situations have led to fallout-shelter programs as part of civil-defense plans. Means of decontaminating land, water, and food also are being developed to combat possible effects of fallout during and following a nuclear attack. Many separate investigations, however, suggest that even if some humans survive an all-out nuclear war and potential nuclear winter (see Nuclear Weapons), they will probably be sterile.

Hazards from Nuclear Reactors

The growth of nuclear power as a source of electricity poses some problems in the control of radiation hazards. Fission products from the controlled-fission process used in reactors are hazardous to the environment if released in large quantities, as they were at Chernobyl' in 1986. Should an accident occur and the fission debris escape, the area for miles around a nuclear plant would be contaminated. To avert this, nuclear engineers design the power system so as to minimize the chances of accidental release.


Fig-4, Nuclear Ghost Town ‘Pripyat’, Ukraine, is a ghost town of empty buildings and overgrown weeds. The town had to be abandoned after the nuclear explosion at the nearby Chernobyl’ nuclear power plant Hazardous Waste

Hazardous Wastes, solid, liquid, or gas wastes that can cause death, illness, or injury to people or destruction of the environment if improperly treated, stored, transported, or discarded. Substances are considered hazardous wastes if they are ignitable (capable of burning or causing a fire), corrosive (able to corrode steel or harm organisms because of extreme acidic or basic properties), reactive (able to explode or produce toxic cyanide or sulfide gas), or toxic (containing substances that are poisonous). Mixtures, residues, or materials containing hazardous wastes are also considered hazardous wastes.

Many dangerous substances can be used only with special precautions that decrease their risks. When discarded, these substances are no longer under the direct control of the user and may pose special hazards to people or other organisms that come in contact with them. Because of such potential risks, hazardous wastes are processed separately from ordinary wastes.

In the United States in 1993, about 250 million metric tons of hazardous waste were produced, and hazardous waste went to 2584 treatment, storage, or disposal sites.


SOURCES OF HAZARDOUS WASTES Industrial Wastes Hazardous wastes are generated by nearly every industry; those industries that themselves generate few hazardous wastes nonetheless use products from hazardous waste generating industries. For example, in the computer software industry, writing software generates little hazardous waste, but the manufacture of computers involves many industrial processes. Making a computer circuit board generates spent electroplating baths that contain metal salts, and the production of computer chips uses acids, other caustic chemicals, and solvents. Other hazardous wastes are generated in the manufacture of fiber optics and copper wire used in electronic transmission, as well as magnetic disks, paper for technical manuals, photographs for packaging and publicity, and trucks for transportation of the finished product.

Agricultural Wastes

Industry is not alone in generating hazardous wastes. Agriculture produces such wastes as pesticides and herbicides and the materials used in their application. Fluoride wastes are by-products of phosphate fertilizer production. Even soluble nitrates from manure may dissolve into groundwater and contaminate drinking-water wells; high levels of nitrates may cause health problems.

Households Wastes

Household sources of hazardous wastes include toxic paints, flammable solvents, caustic cleaners, toxic batteries, pesticides, drugs, and mercury from broken fever thermometers. Local waste-disposal systems may refuse these items. If they are accepted, careful monitoring may be required to make sure soil or groundwater is not contaminated. The householder may be asked to recycle or dispose of these items separately.

Renovations of older homes may cause toxic lead paint to flake off from walls. Insulation material on furnace pipes may contain asbestos particles, which can break off and hang suspended in air; when inhaled, they can cause lung disease and cancer.

Medical Wastes

Hospitals use special care in disposing of wastes contaminated with blood and tissue, separating these hazardous wastes from ordinary waste. Hospitals and doctors' offices must be especially careful with needles, scalpels, and glassware, called “sharps.” Pharmacies discard outdated and unused drugs; testing laboratories dispose of chemical wastes. Medicine also makes use of significant amounts of radioactive isotopes for diagnosis and treatment, and these substances must be tracked and disposed of carefully.


Effect of Hazardous Wastes

Hazardous wastes may pollute soil, air, surface water, or underground water. Pollution of soil may affect people who live on it, plants that put roots into it, and animals that move over it. In Times Beach, Missouri, in 1983, oil contaminated with dioxin was spread on roads to keep dust down; thus, residents were exposed to high levels of dioxin. Sludge from municipal sewage disposal may contain toxic elements if industrial waste is mixed with domestic sewage. If the sludge is used as a fertilizer, these elements may contaminate fields. Toxic substances that do not break down or bind tightly to the soil may be taken up by growing plants; the toxic substances may later appear in animals that eat crops grown there and possibly in people who do so.

Air may become contaminated by direct emission of hazardous wastes. Evaporation of toxic solvents from paints and cleaning agents is a common problem. The air above hazardous waste may become dangerously contaminated by escaping gas, as can occur in houses built on mine tailings or old dump sites. Basements of homes built over uranium mine tailings often contain high levels of radioactive radon gas escaping from the radioactivity below.

River and lake pollution, if it is toxic enough, may kill animal and plant life immediately, or it may injure slowly. For example, fluoride concentrates in teeth and bone, and too much fluoride in water may cause dental and bone problems. Compounds such as dichlorodiphenyltrichloroethane (DDT), PCBs, and dioxins are more soluble in fats than in water and therefore tend to build up in the fats within plants and animals. These substances may be present in very low concentrations in water but accumulate to higher concentrations within algae and insects, and build up to even higher levels in fish. Birds or people that feed on these fish are then exposed to very high levels of hazardous substances. In birds, these substances can interfere with egg production and bone formation.

Even pollution that is not toxic can kill. Phosphates and nitrates, usually harmless, can fertilize the algae that grow in lakes or rivers. When algae grow, in the presence of sunlight, they produce oxygen. But if algae grow too much or too fast, they consume great amounts of oxygen, both when the sun is not shining and when the algae die and begin to decay. Lack of oxygen eventually suffocates other life; some living things may be poisoned by toxins contained in the algae. This process of algal overgrowth, called eutrophication, can kill life in lakes and rivers. In some cases, particular algae can also poison the drinking water of people and livestock.

Underground pollutants can be carried by underground water flow. These wastes form spreading underground plumes (long, featherlike columns) of contaminants, which may reach the surface if the water emerges in a spring or is pumped by wells. Especially dangerous are solvents that may have leaked from underground storage tanks or may have been carelessly poured on the ground. Toxic metal ions may also be present in these waste plumes.

Hazardous Waste Control


Source reduction: - The best way to eliminate hazardous wastes is not to generate them in the first place. For example, improvements have been made in the production of integrated circuits: The toxic chlorinated hydrocarbons commonly used in the 1970s were replaced in the 1980s by less toxic glycol ethers and in the 1990s by low-toxicity esters and alcohols.

Recycling:- Recycling is the recovery or reuse of usable materials from waste. About 5 percent of hazardous waste in the United States is recycled as solvents; a similar amount is recovered as metals.

For example, approximately 15 percent of sulphuric acid is recycled in chemical manufacturing. In the past, most sulphur used for sulphuric acid production was mined; now the amount of sulphur recovered from smelters (facilities that remove metals from ores), refineries (facilities that purify substances), and manufacturers is more than double that produced by mining.

In the United States, the practice of using industrial wastes, which often contain hazardous wastes, as ingredients in commercial fertilizers is encouraged as a means of recycling hazardous wastes. The safety of this practice has recently been called into question, however, and some states are starting to regulate it.

Treatment

Wastes may be made less hazardous by physical, chemical, or biological treatment. Nearly 10 percent of hazardous waste in the United States is treated with water; another 11 percent undergoes other treatment. For example, sodium hydroxide has been used to treat acid wastes at integrated-circuit plants. Some newer plants now treat hydrofluoric acid wastes with lime, producing relatively harmless calcium fluoride, the mineral fluorite. Sulphuric acid wastes, if not recycled, can be treated with ammonia wastes from the same plant, forming ammonium sulphate, a fertilizer.

Incineration has been used since human beings learned to control fire. It is the preferred method of handling infectious medical wastes. However, it should not be used for wastes that contain toxic heavy metals or chlorinated hydrocarbons: When burned, old painted surfaces can release lead or arsenic into the air, whereas chlorinated hydrocarbons produce hydrochloric acid and dioxins. Solids left over from incineration may have to be disposed of as hazardous waste. About 6 percent of hazardous waste in the United States is incinerated, and another 11 percent is burned along with fuel.

Solidification of wastes involves melting them and mixing them with a binder, a substance that eventually hardens the mix into an impenetrable mass. One suggested treatment of radioactive waste involves turning it into a glass through a process known as vitrification.

Approximately 8 percent of hazardous waste in the United States is stabilized—kept from moving through groundwater and air. Sometimes waste can be stabilized on-site; simple remedies such as covering the waste may be sufficient. Other stabilization methods involve building a barrier around the waste. This barrier can be of plastic, steel, concrete, clay, or even glass.

Disposal

Surface impoundment (placing liquid or semi liquid wastes in unlined pits) keeps waste in long-term storage, but it is not considered a method of final disposal. About 8 percent of hazardous waste is


injected into deep wells; 21 percent enters landfills (large, unlined pits into which solid wastes are placed) as its ultimate resting place.

Abandoned and particularly serious waste sites may qualify as “Superfund” sites, eligible for cleanup with government funding under legislation passed in 1980. In 1993, of about 38,000 hazardous-waste sites inventoried by the Environmental Protection Agency (EPA), 1407 sites were listed on or proposed for the National Priority List (NPL) for waste cleanup. In 1995 the EPA estimated that 73 million people lived within 4 miles of a Superfund site in the United States. Before 1995, 3300 emergency removals—urgent cleanups of hazardous wastes because of the immediate hazard they present—were conducted.

The serious problem of underground plumes of hazardous materials leaving the original disposal sites has only partial solutions at this time. The typical method of handling this problem is the drilling of wells around a plume's perimeter. Hazardous materials are then removed from some wells, and water may be injected into other wells to produce a barrier to the plume's motion. Drilling wells and monitoring holes near a toxic site carries risks; a plume originally confined between strata (horizontal layers of rock) may penetrate vertically through a drilled hole and escape confinement.

A recent method of treatment for shallow plumes of chlorinated solvents depends on their chemical reactivity. A trench is dug around the leaking waste site and filled with a mixture of soil and powdered iron. The iron then reacts with the chlorinated solvents, turning them into simple hydrocarbons, which are less hazardous.

International Issues

Worldwide, about 400 million metric tons of hazardous wastes are generated each year. In 1989 the Basel Convention on the Control of Trans boundary Movements of Hazardous Wastes and Their Disposal was adopted at a meeting convened by the United Nations Environmental Program and attended by 116 countries. The convention requires reduction of hazardous wastes and their movements across borders between countries. As of January 1996, 97 countries had ratified the convention; the United States was not yet among them. The import of hazardous wastes has been prohibited by about 90 countries.

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Environmental Crisis Causes and Manifestations

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Transcript of Environmental Crisis Causes and Manifestations