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protect your mother earth

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-        Protect your mother earth     jatinder pal singh  assistant prof. physics

 

There are several reasons why it is instructive to begin an overview of the global environmental crisis with a detailed study of the problem of the infamous s” ozone hole.”

First many people are very frightened and puzzled by it, and we might all be glad to understand it a little better.

Second it is indeed very serious; some especially among those living in the  (Southern Hemisphere) would insist that it is the most immediately. Pressing environmental problem we ace today.

Third, it is in certain respects relatively conceptually simple and the philosophical and policy imperatives that it raises are relatively clear cut although no less painful to conform than those arising out of many other issues we will consider. Most people, although certainly not all agree about that should be done about it. There is surprisingly little scientific disagreement about the basic nature and seriousness of the hole as compared to many other highly contentious issues such as the greenhouse effect, deforestation and nuclear safety. From the scientific and historical point of view, we know pretty well what went wrong. This makes the ozone hole quite rare among ecological problems, where disputes about the facts of the mater get inextricably entangled with disputes about values. The consensus on the ozone hole is very recent. Ten years ago the debates about the ozone hole is very recent. Ten years ago the debates about the ozone hole sounded much like the debates about the ozone hole sounded much like the debates about the greenhouse effect today.

Hence the ozone surprises are almost a “textbook” case, if there could be such a thing, of an environmental disaster. It defines a basic pattern that we will see repeated again and again in other contexts. It is also, as we shall see, replete with terrible ironies and devastating surprises.

 

IN THE BEGINNING ………….

Very early in the Earth’s history (more than 3 billion years ago), our planer possessed what is technically known as a “reducing” atmosphere – a mixture of compounds such as water vapour, carbon dioxide, and probably methane and ammonia, with little or no free oxygen. There was a high flux of UV (ultraviolet radiation) from the sun, at levels which would be lethal to most forms of life today. Somehow, simple life-forms appeared on the Earth that used anaerobic processes ( processes not requiring oxygen) to get their energy. There are many such bacteria still present on the Earth – the so-called chemoautotrophic bacteria that make iron plumbing smell of sulfur, for example.

About 3.5 billion years ago, photosynthetic forms evolved. Photosynthesis is the complex process by which organisms containing chlorophyll or similar compounds can utilize solar energy to create carbohydrates from water and carbon dioxide, releasing free oxygen in the process. Photosynthesis was the most sophisticated strategy that had yet been fund for extracting energy from the environment, and these early photosynthesizes (such as the blue-green algae) eventually came to dominate the biosphere.

With the evolution of photosynthesis, the planet experienced its first pollution crisis, for oxygen is very toxic to most anaerobic organisms. As oxygen released by photosynthesis built up, the anaerobes declined, and now survive only in places where there is very little free oxygen, such as the bottom of the sea and our intestines. Aerobic organisms, which could use the oxygen, for respiration, evolved. Respiration (which is really a highly controlled combustion process) makes much more energy available to the organism than any anaerobic process; this in turn allows respiring organisms a much higher level of activity than anaerobic organisms or photosynthesizes, and these organisms quickly took over as dominant life-forms on the planet.

As oxygen accumulated in the atmosphere, an ozone layer begin to form. Ozone is a form of oxygen created by the action of high energy ultraviolet light (UV) son oxygen. Ozone observes ultraviolet light ( or more precisely, UV is observed by the  creation and destruction of ozone). This protected the surface of planet from the high energy ultraviolet light from the Sun, which allowed  more complex and delicate life-forms ( like us) to evolve. Hence we could summarize this whole process by  saying that life itself help to create the very atmospheric conditions that made its own continuance and further evolution possible, The ozone layer is one among many important examples of components of the earth’s physical environment that are are  bioorgenic (meaning, created and maintained by life itself).

The ozone layer also helps to maintain the very structure of the atmosphere. The ultraviolet energies observed by the ozone layer are re-radiated to the upper atmosphere ( the stratospheres) as heat, warming it and  thereby causing the temperature inversion that defines the boundary between the stratosphere and the lower atmosphere ( or troposphere). The total or near total disappearance of the ozone layer might result in atmospheric instabilities of a type never before  experienced, quite apart from the destruction of most life on Earth by irradiation.

Ozone and the Ozonosphere

Ozone itself is a bluish, irritating gas with a pungent odour. It is a powerful oxidant and can be used as bleach and sterilizing agent; in large enough concentration it is quite toxic.

Ninety present of the ozone in the atmosphere is normally in the stratosphere, concentrated at an altitude of around 12 to 25 kilometers.( This layer is sometimes called the ozonosphere.) However, in a heavy smog, ozone concentration at ground level can be as much as ten times higher than normal, causing respiratory irritation and damage to plants. One of the many ironies of the ozone story is that while we  have to little where it is needed, we are often getting too much where it is not, both effects being due to different kinds of pollution.

If all the ozone that is normally present in the atmosphere were to be separated out from the air in which it is mixed, and were concentrated into a single  layer at ground- level temperature and pressure, it would only be about 3 millimeters thick. The existence of all life on Earth more complex than bacteria depends on this evanescent wisp of gas.

The  UV  radiation that can reach the earth ‘s  surface can be divided into two bands , usually called UV—B ( the far ultraviolet )  and UV—A  ( or the near ultra – violet). The UV that gives us a sunburn sis mostly UV – A, a little bit of which can actually be good for us. The effect of ozone is to filter most out of the UV-B, the most energetic (and hence the most potentially damaging) radiation that would otherwise reach the Earth’s  surface. Hence the depletion f the ozone layer not only increases the intensity of the UV radiation reaching the surface, but it tends to shirt the peak energy into the UV-B range. This is the kind of UV that does the most harm to sensitive biomolecules such as proteins and nucleic acids.

Ozone is constantly being created and destroyed by the action of UV on oxygen  in the stratosphere. There are other natural processes that destroy ozone as well, but until recently the processes of creation and destruction were usually in balance, so that the net amount of ozone created was equal to the amount being destroyed. ( This is an example of as dynamic equilibrium.) This happy sate of affairs went on for a few billion years until about the year A.D. 1928, when a brilliant industrial chemist named Thomas Midgley, Jr., invented CFCs(chlorofluorocarbons). These compounds, which are rare or non-existent in the Earth’s normal chemistry, break down ozone, leaving the planet’s surface again at risk from ultraviolet radiation from the Sun. and this is where our story really begins.

What Are CFCs?

Midgley ( who was also the creator of tetraethyl lead) was really just trying to solved what seemed to be straight  forward problem of product safety. By1928, the refrigeration industry was expanding rapidly, but the only working fluids available for refrigerators were compound like ammonia, methylene chloride, or sulfur dioxide, all toxic flammable, or corrosive. Some accidental deaths from leaky refrigerators had actually occurred. It was essential to find a refrigerant that was safe, sand CFCs fit the bill perfectly.

Chlorofluorocarbons are chemically very similar to methane and other simple hydrocarbons, but with the hydrogens replaced by fluorines and chlorines. They have great chemicals stability, which makes them almost entirely nontoxic and nonflammable. Midgley demonstrated these desirable properties by inhaling some CFCs and then blowing out a candle flame. They also turned out to have many other useful properties – as solvents, propulsion agents for spray cans, and forming agents in plastic manufacture. But it is precisely their stability that allows them to survive the rip to the stratosphere; most other chlorine – containing compounds break down long before then. Before CFCs, there was no mechanism that could transport significant amounts of chlorine to the stratosphere. Hence there is a considerable irony in this story: the very property of CFCs that makes them so useful is also the property that makes them so deadly. Sit was many years, however, before anyone became aware of this.

First Warnings

The first intimations that CFCs could be endangering the ozone layer came by an indirect route. In the late 1960s, there was considerable controversy in the United States over weather the government should support major project to develop a fleet  of commercial SSTs,  These  would have that could fly high in the stratosphere at supersonic speeds , cutting international  travel times to a fraction of the time required by standard subsonic commercial aircraft . jet aircraft release nitric oxide as a combustion  by product,  and it was known that nitric oxide  can attack ozone. Hence a worry was born that fleets of  SSTs  might damage the ozone  layer,  and this fear may have had something to do with the eventual abandonment of the project. ( cost was likely at least  as important a factor in the decision. See roan 1989.)It is now believed that he nitric  oxide from jet exhaust would pose a minimal threat to the ozone layer. But the debate led scientists to ask if there were other industrial pollutants that might damage ozone. The first measurements  of CFC  concentrations  in the atmosphere  had been made in the early 1970s by  James lovelock .  Because the amount revealed by his measurements were so low  (  a few parts per trillion at that  time —–  they are now much higher )  Lovelock remarked  that they posed  no danger, a position he later  reversed.  In 1973 , chemist  Sherwood  Rowland  set his  postdoctoral  fellow  Mario Molina the problem of investigating  whether CFCs  could be  having any effect  on the ozone layer.  Rowland  and Molina  soon  discovered to their consternation  that ozone  can  be broken down by chlorine  via a catalytic reaction cycle —–  that is a reaction in which a substance (  in this case chlorine )  promotes a reaction but is not used up by it .

The  important point to not is that because  the  reaction is  catalytic, a very  small amount of the catalyst ( chlorine )  can  break down a great deal of ozone , even thought the concentration of CFCs  in the atmosphere is at trace levels.  In fact , one chlorine atom  will  break  down  between 10,000 and 100, 000 ozone molecules before it finally precipitates  out of the atmosphere (  usually as a form of acid rain , to add environment insult to injury). This is a good illustration of general rule that we are gradually learning to respect: the danger posed by a pollutant may not be in simple proportion to its amount or concentration in the environment.

A check of CFC production figures convinced Rowland sand Molina that CFCs could eventually (but not for several decades, they first estimated ) do significant damage to the ozonosphere. It is reported that Rowland came home from the lab one day and reported to his wife, ” It looks like the end of the world!”4

Rowland and Molina, and then many other scientists and concerned citizens, began to argue that CFCs should be restricted. Sin the late 1970s a number of countries (Canada, the United States, Norway and Sweden) introduced bans on CFCs usage for aerosol sprays, and overall consumption of CFCs briefly decreased before beginning its inexorable climb again in the 1980s. However, there was, up until the mid 1980s, still no absolutely convincing evidence either that    CFCs actually were breaking down ozone in the stratosphere, sor that ozone was becoming depleted. In other swords it was not known  with certainly that CFCs do harm the ozone layer, only that they could. The CFC industry fraught back vigorously, using all the public relations powers at its disposal, and played on the scientific uncertainties to argue that the case against CFCs had not been established. The debate became at times very bitter and personal?

Bit by bit, further scientific evidence accumulated that CFCs might indeed be doing exactly what Rowland and Molina had predicted they would do. But many uncertainties remained.

The Ozone Hole Appears

Since 1957 ( the international Geophysical Year), a team of scientists led by James Farman had been measuring ozone levels, among other geophysical data, at the British research station in Antarctica. This was just for the sake of “pure” science, and they were close to being   shut down by budget cuts on at least one occasion.

In 1984, Far man and colleagues noticed that ozone reading over the polar region had been dropping markedly since the late 1970s, with a more dramatic drop each year. It seemed that a large hole was appearing over Antarctica in the ozone layer each Antarctic spring. Farman publishes his results in 1985.Sshortly afterward, it was discovered that an American NIMBUS weather satellite had been showing the same thing since the late 1970s,but the data from the satellite had been rejected because it was assumed that any readings that were so low must be due to  instrumental error!

In the southern spring ( September to November) there is nearly 100 percent depletion of ozone in some areas of Antarctica and over the Southern Sea. There is a loss of zero to 10 percent ( and occasionally higher) in other areas of  the world, even as far as the Equator. These differences are definitely greater than the normal variations in the long – run average levels. And there is a similar deflection in the Arctic each northern spring , but less severe.

Intense debate sprang up on the cause of the ozone hole, and the call was renewed to ban CFCs. Several theories were proposed to account for the hole; sat the time of its discovery there still was no proof (although certainly a strong suspicion) that it was due to CFCS. In 1986 and 1987, teams of scientist went to Antarctica and under conditions of some hardship studied the ozone hole intensively. Aircraft were flown through the hole to take direct samples of the air. ( It was no travel matter to fly a treatmental  ER-2 at altitudes above 60,000 ft over Antarctica in the winter time. If a plane had gone down, the pilots would have had little hope of being rescued. Considerable personal courage, both physical amoral may be needed to answer the question that need to be answered). By early 1988, scientist were finally convinced that they had found unmistakable evidence that  CFCs were guilty : ” The extensive new data leave no doubt that man made CFCs are primarily responsible for the ozone could be broken down so quality. The situation is much worse than they had predicted.

The explanation for this lies partially in an important fact about catalytic chemistry that ha not been noticed, and partially in the very unusual  meteorological condition in the Antarctic winter. I will most of the fascinating but very technical details. Here is the essence of the matter: CFCs are broken down by energetic ultraviolet in the stratosphere, releasing chlorine which quickly is taken up in harmless ” reservoir compounds.” In the Antarctic winter, a stratospheric vortex forms, a great whirlpool of air as big ass the continent itself. Within the vortex, polar stratospheric clouds (PSCs) form, clouds of tiny ice crystals. This was some what unexpected since the stratosphere is usually too dry to form cloud. The reservoir compounds can breakdown into highly reactive chlorine and chlorine monoxide at very high rate on  the ice crystals; this is the “heterogeneous” chemistry that surprised the experts . When sunlight hits the PSCs in the Antarctic spring, it stimulates the breakdown  of ozone by the accumulated chlorine and chlorine monoxide, and a huge forms in the ozone layer. Eventually as the polar vortex breaks up un late spring, the depleted air mixes with air at lower latitudes, causing patches of low ozone world wide. A similar process occurs in the Northern Hemisphere, although the hole formed is less deep because the northern polar vortex is much less intense. And there is strong evidence, as well that this process can occur anywhere in the stratosphere where dust or ice particles are available. The eruption of the volcano Pinatubo, for instance, is suspected to have provided enough stratospheric dust to contribute significantly to recent ozone deplection.9

The key factor that no one had originally anticipated was the ability of tiny ice crystals and dust particles to promote and accelerate the catalytic breakdown reactions. Sin fact, it is well known that catalytic reactions of many kinds go faster on surfaces; perhaps this possibility had not occurred even to the most vigilant of experts because of a belief in the stratosphere as a volume of pristine clean air.

The ozone story is therefore a history of surprises: first, that CFCs can decompose ozone catalytically, sand second that the decomposition can be further accelerated by the freakish ” heterogeneous chemistry” that occurs on the surface of ice crystals in the Antarctic winter vortex.

One often hears of “worst case scenarios”; it is as if for CFCs every worst case scenario has, so far, come true.

BIOLOGICAL EFFECTS OF OZONE DEPLETION

For simplicity, we can divide the biological effects of ozone depletion into two sorts: effects on humans, and effects on life in general.

The effects on humans naturally get the most press. The most dramatic dangers are skin cancer and retinal burn. A 2 percent increase in UN-B reaching the ground is predicated to lead to a 6 to 8 percent increase in skin cancer in people with light skin. People in the Southern Hemisphere are especially at risk. It is estimated, for instance, that two-thirds of all Australians now loving will eventually need treatment for skin cancer, while in Canada skin cancer rates have been going up 5 to 7 percent per year. There will also be an increase in sunburn and retinal burn. Three is also a poorly understood effect upon the human immune system; UV-B seems to suppress the activity of certain types of immune system cells. It is suspected that neither pigmentation nr sunscreen protects against this effect. For that matter, there is no epidemiological evidence that sunscreen actually protects against skin cancer either, only a presumption that it must do because it blocks UV-B.11

The deepest concern, from the viewpoint of understanding the consequences of the ozone hole for the integrity of the ecosystem as a whole, is the possible effects upon animals, plants, and marine organisms. Recently, sheep near Punta Arenas in southern Chile, an area that occasionally finds itself directly under the ozone hole,12 have been suffering unusual tumours, cataracts, and retinal burns. While locals are convinced, there is no “scientific” sroof that this is due to increased UV exposure.13

Much investigative work has ready been done on the biological effects of UV. There is much reason to fear that ozone depletion could lead to greatly diminished growth and vitality of forests and agricultural crops. For instance, some recent studies indicate that land plant biomass can be reduced by as much as 10 to 20 percent; even a short burst of UV early in the growing season can irreversibly stunt plant growth.14 Even more serious could be its effects son the krill ( near –microscopic crustaceans, which serve as staple food for many marine mammals and birds) and marine micro-organisms such as plankton and algae. UV can  penetrate sea water to a considerable depth ( sunburn is a hazard for scuba shivers). The plankton and algae are the very base of the marine food chain and, furthermore, provide much more the planets oxygen. Of course, marine organism must already be adapted to a fair amount of UV, but they clearly have their limits. There is already evidence that UV levels 10 to 20 percent higher than normal can damage marine micro-organisms, as well as small fish. A recent detailed survey of Antarctic waters found evidence that photosynthesis by those phytoplankton regularly exposed to the ozone hole is reduced by 6 to 12 perecent.15

No one yet knows exactly how serious the situation could become, although it appears probable that the base of the planetary food chain will, from now on, suffer some and possibly significant extra stress from UV – B, above and beyond  all other stresses being imposed upon it by human action, for decades to come.

Where Thing stand Now

By 1988, it was clear that there is a worldwide ozone depletion of a few percent, and between 50 percent sand nearly 100 percent depletion in the Antarctic hole. This implies a significant increase in ultraviolet exposure for many parts of the world, especially in the Southern Hemisphere. Governments at last began ponderously to address fact that this is an international emergency. In 1987, a treaty was signed in Montreal by 51 nations and the European community, under the auspices of UNEP ( United Nations Environmental Program) to limit the release of CFCs, and halos. In March 1988, Dupont Corporation, a major producer ( and defender) of CFCs, finally conceded the danger and said that it will phase out production of CFCs. The Montreal Protocol was strengthened in 1990 and again in 1992, with phase out deadlines moved up, but some countries have not yet signed.

CFCs had already been band as aerosol propellants by the late 1970s by Canada, the United States, Norway, and Sweden. This resulted in a brief drop in production of CFCs, but production rose quickly again to a peak of over a million tones per year in the late1980s. Finally, production has begun to fall sharply in the mid-1990s as a consequence of the Montreal Protocol.16 On the face of it, therefore, the worst of the crisis may have passed. Unfortunately, matters are not so simple.

The Antarctic ozone hole continues to appear every Antarctic spring and is, if anything, deepening and becoming more stable and long lived. CFCs remain in the atmosphere  for a hundred years or more, and are still being added to the atmosphere a significant rate. All over the world, there are old refrigerators rusting in dumps, just waiting to release their loads of Freon into the atmosphere. Even given full compliance with the Montreal Protocol, the concentration of CFCs in the stratosphere is expected to double or triple over the next few years. Even if we entirely stop producing CFCs this very day, the stratospheric concentration will continue to increase for some years because it takes some time for CFCs to diffuse to the stratosphere. According to Environment Canada (19994b). ” he period of maximum stratospheric ozone depletion will be around the turn of the century.”

There is a little recent good news: the rate of increase of CFCs sin the atmosphere is slowing from 6 percent per year to a mere 3 percent per year.17 It is difficult to tell how much is due to the slowdown of industrial activity coming from the economic recession of the early 1990s.

The Outlook

For  decades  the biosphere will be subjected  to more UV- B  than normal –  some areas  such as the southern sea, dangerously  more at some times of the years. There is no question that will this have some deleterious effect on the  ecosystem , as well as putting human beings themselves at higher risk in a number of ways. Exactly how much harm will be done is very difficult to say , expect that is very likely that it will get worse than it is now .  It is within the bounds of possibility that  UV levels over some parts of the earth will become near—lethal , particularly in the southern latitudes.

Best case scenario; CFCs  are phased out or replaced by about the turn of he century, and life on earth succeeds in enduring marginal UV—B  stress for 100 years or so, although with a hard to predict overall  reduction  in vitality  the global  ecosystem and possibly some species extinctions or at least realignment of marine ecosystem .

The worst case ;  use of CFCs  does not stop,  due to a failure to uphold  effective international agreement.  It is impossible to predict the result of this, but the experiment should not be tried – especially given the possibility that there could be further ‘’ surprises”

Ozone is still being created at a constant rate by sunlight, and eventually, s the CFCs finally settle out of the atmosphere, the ozone layer  will “self heal.” But it will take at least a hundred for it to return to its pre-1970s condition.

“Lifestyle” Changes

Many parents now accept the necessity of leathering their small children with sunscreen before sending them out to play, much as sexually active adults in the 1990s nows accept the grim necessity of ” safe” sex. In 1987, the regain administration briefly dared to suggest that such ” personal protection” would do in place of regulation to control CFCs. It was not made clear how sunglass and floppy hats  were expected to protect krill or field crops from UV-B. This proposal was greeted with howls of derision, sand the embarrassment may have helped to persuade the United States to eventually support the Montreal Protocol.18 It seems painfully clear that while lifestyle changes ( such as wearing sunglass regularly) are a reasonable, personal response to the UV – B threat, they are hardly going to solve the problem.

Structure of the Problem

The ozone problem has the following structure, which with minor variations one sees repeated in the case of many of the technologies that human ingenuity has provided:

• Ingenious invention of very useful product or method, done with the best of intentions. However, no one asks if product could do long term damage ;  there is a  complete lack of foresight.
• we  come to depend on this product.  It becomes so useful, at least to some, that almost nothing else will do quite as well; society evolves a kind of dependency on the product, which makes it very difficult to drop it or switch a substitute. There is a real reason why the market supports the vast trade in CFCs; it is not just corporate greed is a factor in the response to the problem.
• Experts warn of danger, but  are mostly disbelieved.
• Evidence (often indirect) mounts, but disbelief continues.
• Strongest denial of warnings from those who benefit most from the product or process. It becomes a political issue, decided in part by advertisement and lobbying.
• Conflict between short-term economic and long-term environmental interest.
• Finally there is undeniable evidence that experts were right; indeed, it is worse than they predicted, because there is a completely unexpected mechanism that enhances the effect.
• Some still can’t be convinced.

 

About the Author

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