The Impact of Air Pollution in Greenhouse Effect,Acid Rain and Ozone Depletion
The greenhouse effect refers to the maintanance of an equable temperature over the planet and it linked to global warming. Global warming is a global rise in temperature due to the accumulation in the atmosphere of gases that permit radiation from the sun to reach the earth’s surface but prevent the heat from escaping back to space. Although the extent and the impact of the greenhouse effect is controversial, many biologist believe that it could significantly alter our environment in the future. Gases such as chlorofluorocarbons are involved in producing the greenhouse effect. These gases are the relatively recent by-product of the manufacture of refrigerator, plastics and aerosol propellants. Other gases that promote the greenhouse effect have been part of our atmosphere for millions of years carbon dioxide and methane.
D. L Lindstrom of the university of Illinois at Chicago and D. R MacAyeal of the University of Chicago recently examined records of cores of the ancient ice from Siberia, Scandinavia and the Arctic Ocean. Using computers to stimulate the status of ice and atmosphere going back 30000 years, they found that levels of carbon dioxide had increased enough at the end of the most recent ice age to melt the ice and raise the earth’s temperature. Their findings suggest that cycles of ice ages followed by shorter warm periods, may have been caused solely by raising and failing levels of carbon dioxide in the atmosphere.
In 1986 worldwide carbon dioxide emissions from transportation and industrial sources totaled somewhat less than 5 billions tons. By 1987 the total was more than 5. 5 billions and has continued to rise. The burning of fossils fuels and deforestation have caused a 25％ increase of carbon dioxide in the atmosphere since 1850. In the last 25 years alone, the increased insulation of carbon dioxide has resulted in the earths atmosphere becoming 0. 4 warmer, and between 1983 and 1990 the surface temperature of the ocean rose about 0. 8
These increases in temperature may seem insignificant, but during the last ice age in North America, when ice covered the northern United States and Canada, the average temperature of the earth at sea level was only 4 ℃ colder then it is now. In 1989, Mostafa Tolba, head of the United Nations Environment Program, estimated that if the current levels of gases release into atmosphere continue, the earth’s temperature will melt the polar ice craps; the released water will raise sea levels and inundate low-lying, often densely populated, costal areas. The U. S. Environmental Protection Agency estimates that for each 30 cm inland. During the past century, worldwide ocean levels have risen 12. 7 cm and it is estimated that more than 1. 8 million hectares of the land in the united States alone will be flooded if the temperature rises as predicted. Higher temperature can also affects winds, currents and weather patterns, causing heavy rainfall in the others. The greatest grain-production areas of the world lie in the interiors of continents. If they become warmer and driver, world food supplies may be affected.
Swamps and wetlands have long been known to be sources of methane produced by anaerobic bacteria. Many animals produce methane during digestion and large amounts of this gas are released by wood-digesting organisms in the guts of termites. The total annual production of methane in the atmosphere has also increased slowly in recent years. A small part of this increased numbers of termites in cleared tropical rain forests areas, which in 1990 were being destroyed at the rate of more than 50000 hectares per day. This means that we clear an area of tropical rain forest equivalent to that of more than 1000 basketball courts every seconds, 24 hours per day.
Acid rain occurs after the burning of fossil fuels release sulphur and nitrogenous compounds into the atmosphere. There, sunlight converts these compounds to nitrogen and sulphur oxides and they combine with water to become acid rain. Acid rain changes the pH of the lakes and streams and kills many organism in them. It also injuries plants upon which it falls. About half of the Black Forest in Germany has succumbed to this effects. Acid rain has also stunted or killed trees growing downwind from industrial sites. Acid rain also affects nonliving materials. For example, the natural weathering of ancient Mayan ruins in Southern Mexico, the Parthenon in Greece, and monuments in Washington D. C. , has been accelerated by acid rain during the past decades. Acid rain is not responsible for all dead or dying trees in the world’s forests. Some trees have perished as a results of insufficient rainfall during successive dry years. Others have succumbed to insects infestations or salt scattered to melt ice and snow on roads, and still others have been weakened by disease.
Ozone is form of oxygen in the stratosphere that is more effective than ordinary oxygen in shielding living organism from intense ultraviolet radiation. Ozone is produced from oxygen with the aid of ultraviolet light. Chlorofluorocarbon which are inert chemicals used for refrigerator and other industrial purposes, are broken down by sunlight at high altitudes into active compounds that destroy ozone. Destruction of ozone in the stratosphere results in increased exposure to ultraviolet radiation, which increases the incidence of skin cancers, genetic mutations, and damage to vegetation especially crops.
The accelerating destruction of the ozone shield has been recognized as a serious global problem by both the united States and the European Economic Community. In 1987 the United States proposed a 50％ reduction in the production and uses of chlorofluorocarbons by the year 2000, and in 1989 the European Economic Community proposed a total ban on chlorofluorocarbon, also by the year 2000. In 1990, however, developing nations such as India, China and Brazil had plans to expand the production of chlorofluorocarbon and contended that a ban would place them at an economic disadvantages. Because global cooperation on this matter is urgently needed, the major industrial nations are seeking way to allay the economic concerns of developing countries by, for example, producing viable alternatives to chlorofluorocarbon. One such alternative was introduced in 1994, when non-CFC refrigerants became standard in the air-conditioning systems of most new automobile sold in the United States and elsewhere.
Chlorofluorocarbon are not the only danger to the protective ozone layer. Bromine-based compounds called halons, which are commonly found in electronic equipment and portable fire extinguishes, can be up 10 times more destructive of ozone than are chlorofluorocarbon. Halon concentrations in the atmosphere increased about 20％ per year between 1980 and 1986, according to the Environmental protection Agency. Some scientist believe the concentrations are as much as 50％ higher than that and are recommending the powders and other inert gases be substituted for halons in fire extinguishes. Over the last 100 years the global population has increased four-fold to seven billion people and may reach nine billion by 2075. How to produce enough food to feed all these people is one of the biggest global challenges.
Throughout the twentieth and early twenty-first century, food production has been dramatically increased by improving agricultural yields, particularly by applying nitrogen fertilisers. In 1908, the German chemist Fritz Haber invented a method for producing ammonia fertilizer from the inert nitrogen gas which is in the air all around us. Haber’s discovery earned him a Nobel prize and paved the way for cheap, industrially-produced fertilizer. A miracle of industrial chemistry, today around 150 mega-tonnes of nitrogen fertiliser are produced annually and half of the global population would not be alive without Haber’s process. However increasingly it is being realised that this huge benefit to human development comes at a high price. Human production of reactive nitrogen is now more than double natural nitrogen fixation and we have unwittingly conducted a huge global-scale experiment in geoengineering.
The problem is that the nitrogen we spray on our fields does not stay there in perpetuity – much of it is washed into rivers or evaporated into the atmosphere. In water-bodies, nitrogen causes algal blooms that kill fish, impair drinking water quality and reduce aquatic biodiversity. In the atmosphere nitrogen from agriculture combines with oxides of nitrogen produced by burning fossil fuels. In the UK, levels of this nitrogen pollution are often more than ten times higher than the natural background and scientists have observed acute nitrogen deposition events even in the remote Arctic. Atmospheric nitrogen is a severe threat to human health, reducing the life expectancy of at least half of Europe’s population by six months or more. Increasingly scientific research shows that nitrogen deposition is also a serious threat to ecosystems. A paper just published in Proceedings of the National Academy of Sciences shows the impacts of nitrogen deposition in the environment may extend even further than previously thought. Dr Richard Payne and Professor Nancy Dise, of Manchester Metropolitan University, together with colleagues at Lancaster University and the Open University, studied more than 100 individual plant species’ reactions to nitrogen deposition at 153 grassland sites across Europe.
The scientists found that many species, particularly wildflowers such as creeping buttercup, harebell, yarrow, and autumn hawkbit, were much less abundant in areas with high nitrogen levels, such as central Britain, the Netherlands, northern Germany and Brittany. But particularly surprising was the discovery that many species declined at very low levels of pollution, often below the legally-recognised ‘safe’ level. Professor Dise said: “One of the drawbacks of previous studies is that most field experiments to establish limits on pollution are near the populated and polluted areas where most scientists live. It may be that long-term exposure to even medium levels of pollution have already changed these ecosystems. In this latest research, we studied many grasslands along the natural gradient of pollution across Europe. And we found that at even relatively ‘clean sites’, low levels of pollution had an effect on the abundance of some plant species.” This surprising result shows that even areas a long way from pollution sources and previously thought to be free from air pollution impacts may have been affected. But this is an environmental concern that most people have never heard about. Dr Payne said: “We have been very good at communicating the problem of climate change and carbon emissions but have failed at communicating the nitrogen problem. Until the public are aware of the issue then policy makers are unlikely to take action.” The scale of the problem is huge. It has been estimated nitrogen pollution costs the countries of the European Union alone up to €320 billion a year- but progress in tackling it has been limited.
Over recent decades many developed countries have been quite successful at reducing nitrogen produced by fossil fuel burning; UK emissions of nitrogen oxides are down by almost 60% over the last 40 years. But tackling agricultural emissions has proved much more difficult. Nitrogen fertilizers are essential to feeding the world’s population but we can try to reduce the amount we use and the amount we lose into the environment. The production of meat and dairy products contributes disproportionately to the nitrogen problem: nitrogen is released in the production of crops and then more nitrogen is released when these are fed to animals. In western countries we consume more animal products than is necessary for a healthy diet; if this can be reduced it would have big environmental benefits. At the same time, better agricultural practices such as improved techniques for manure spreading can more than halve nitrogen emissions, as well as saving money. The Netherlands has some of the highest levels of nitrogen deposition anywhere in Europe but have achieved big reductions by legislating for low-emission farming techniques. It is clear that the nitrogen problem isn’t going to be solved quickly, which poses the question – if we must have nitrogen pollution where should it be? Payne and Dise’s research might hold an answer. Dr Payne said: “We found that lots of species are lost with only a little pollution but once the ecosystem is very polluted adding more pollution doesn’t make much difference”. This suggests that to conserve as many species as possible new pollution sources should be put in areas that are already polluted and degraded to avoid any new pollution in currently unpolluted areas.
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