PARTHEBAN

POLLUTION

also called environmental pollution
the addition of any substance or form of energy (e.g., heat, sound, radioactivity) to the environment at a rate faster than the environment can accommodate it by dispersion, breakdown, recycling, or storage in some harmless form.

A pollutant need not be harmful in itself. Carbon dioxide, for example, is a normal component of the atmosphere and a by-product of respiration that is found in all animal tissues; yet in a concentrated form it can kill animals. Human sewage can be a useful fertilizer, but when concentrated too highly it becomes a serious pollutant, menacing health and causing the depletion of oxygen in bodies of water. By contrast, radioactivity in any quantity is harmful to life, despite the fact that it occurs normally in the environment as so-called background radiation.

Pollution has accompanied mankind ever since groups of people first congregated and remained for a long time in any one place. Primitive human settlements can be recognized by their pollutants—shell mounds and rubble heaps. But pollution was not a serious problem as long as there was enough space available for each individual or group. With the establishment of permanent human settlements by great numbers of people, however, pollution became a problem and has remained one ever since. Cities of ancient times were often noxious places, fouled by human wastes and debris. In the Middle Ages, unsanitary urban conditions favoured the outbreak of population-decimating epidemics. During the 19th century, water and air pollution and the accumulation of solid wastes were largely the problems of only a few large cities. But, with the rise of advanced technology and with the rapid spread of industrialization and the concomitant increase in human populations to unprecedented levels, pollution has become a universal problem.

The various kinds of pollution are most conveniently considered under three headings: air, water, and land.

Pollutants commonly are classified according to the part of the environment primarily affected by them: either the air, water, or land. Sub groupings depend on characteristics of the pollutants themselves: chemical, physical, thermal, and others. Many pollutants affect more than one resource.

AIR POLLUTION

The substances that pollute the atmosphere are either

gases, finely divided solids, or finely dispersed liquid aerosols. Five major classes of pollutants are discharged into the air: carbon monoxide, sulfur oxides, hydrocarbons, nitrogen oxides, and particulates (dust, ash). The principal source of air pollution is the burning of fossil fuels—e.g., coal, oil, and derivatives of the latter, such as gasoline—in internal-combustion engines or for heating or industrial purposes. The single largest source of air pollution is automotive exhaust fumes, which contain carbon monoxide and various hydrocarbons and nitrogen oxides. Most sulfur oxide emissions are from utility and industrial plants that burn coal and oil, both of which contain sulfur as an impurity. Air pollution is a particular problem in urban areas, where the ultraviolet rays in sunlight combine with hydrocarbons and nitrogen oxides to form photochemical smog. On a somewhat wider scale, sulfur dioxides and nitrogen oxides from the burning of fossil fuels can combine with atmospheric water vapour to form acid rain (q.v.), which is damaging to water, forest, and soil resources. As a result of the increased consumption of fossil fuels, levels of carbon dioxide in the atmosphere have risen steadily in the 20th century and show signs of increasing atmospheric temperatures worldwide owing to the greenhouse effect (q.v.).

Air pollution is reduced or controlled by various methods. Automotive emissions are reduced by redesigning engines, installing devices to control their exhaust emissions, and improvements in fuel and fuel additives. Coal-burning power plants can be replaced by less polluting ways to generate electricity that involve the use of natural gas, nuclear fuels, or flowing water. Pollutants can be removed, or scrubbed, from the gases emitted in industrial smokestacks by electrostatic precipitation.

WATER POLLUTION

Water pollution includes the accumulation in oceans, lakes, streams, and groundwater of substances that are either directly harmful to life or that have harmful secondary or long-term effects. The principal sources of water pollution are sewage, industrial waste, garbage and refuse, and agricultural fertilizers, pesticides, and herbicides. Any body of water has the capacity to absorb or break down introduced materials, and sewage and some organic industrial wastes are broken down naturally by microorganisms into forms in which they are useful to aquatic life. But if the capacity of a body of water to dissolve, disperse, or recycle is exceeded, all additional substances become pollutants. The major sources of water pollution are untreated sewage from cities and towns, chemical fertilizers and pesticides that have run off farmland into rivers and streams, and chemicals from industrial plants located along waterways.

The domestic waste water in sewage systems can be artificially treated and purified to remove its pollutants before the water is discharged back into the environment in a process called water treatment. Industrial waste water can likewise be purified, or else production methods at the plant can be changed to minimize the production of wastes or recycle them for further industrial use. Agricultural wastes are generally less concentrated and take longer to produce aggravating effects than industrial and municipal sewage wastes originating in or near cities.

LAND POLLUTION

Land pollution mainly involves the deposition on land of solid wastes—such as cans, bottles, plastic containers, paper, and used cars—that cannot be broken down quickly or, in some cases, at all. Aside from recycling, disposal methods include concentrating such materials in landfills, burning them in incinerators, or dumping them in the ocean. The term “land pollution” also includes the accumulation on land of toxic chemicals (in solid or liquid form) produced by industry and of radioactive wastes from nuclear processing facilities.

NOISE POLLUTION

One form of pollution that is characteristic of industrial societies is noise. The intensity of sound is measured in logarithmic units known as decibels; a change from a level of 10 decibels to one of 20 decibels actually represents a 100-fold increase in the sound level. At a level of 80 decibels, sound is annoying; but steady exposure to noise in excess of 90 decibels—a level that is frequently exceeded by many common urban sounds, such as jackhammers, jet planes, and excessively loud music—can cause permanent loss of hearing. In addition to causing loss of hearing, there is some evidence that noise can produce other deleterious effects on human health and on work performance.

Many large cities have taken measures to decrease the level of urban noise; the problem has received much attention with the advent of supersonic jet airplanes. These aircraft, which travel at speeds faster than the speed of sound, create sound waves (sonic booms) equivalent to those of major explosions and capable of damaging structures. The extent to which continuous exposure to sonic booms affects human health and functioning has yet to be determined. Nevertheless, in 1971 the U.S. Congress voted down appropriations to support the development of supersonic transport (SST) planes; several countries, including Britain and France, however, have manufactured such aircraft.

Chemical pollutants

Among the most serious chemical pollutants are the chlorinated hydrocarbon pesticides, such as DDT, aldrin, and dieldrin; the polychlorinated biphenyls (PCBs), which are used in a variety of industrial processes and in the manufacture of many kinds of materials; and such metals as mercury, lead, cadmium, arsenic, and beryllium. All of these substances persist in the environment, being slowly, if at all, degraded by natural processes; in addition, all are toxic to life if they accumulate in any appreciable quantity.

The persistent pesticides have created serious ecological problems. As they move through successively higher organisms in food chains, they accumulate in increasingly concentrated forms at each level, causing damaging effects to the predators at the end of the chains—i.e., they are present in low quantities in simple organisms but become more concentrated as these organisms are consumed by more complex ones, which are themselves consumed by predators. Among the species known to be adversely affected are such meat-eating birds as falcons, hawks, and eagles and such fish-eating birds as pelicans, petrels, cormorants, and egrets. The reproduction capacity of all of these birds has been affected by an accumulation of DDT or a similar compound in their tissues. This is manifested by an impairment in the ability of the females to form eggshells properly. As a result, some species lay soft-shelled or shell-less eggs that cannot be hatched, and there has been a general decline in the numbers of these birds in Europe, Japan, and North America. Although the effects of the same chemicals on mammals is less obvious and still a matter for investigation, some studies suggest that DDT can reduce the productivity of plant plankton, upon which all other marine life depends.

There also is substantial evidence that pesticides lose the ability to control the pests they were designed to kill. Many insect species have developed immunity to a wide range of synthetic pesticides, and the resistance is inherited by their offspring. Furthermore, it has been observed that repeated use of such chemicals creates pest populations in areas in which none previously existed. This happens because the pesticides destroy populations of carnivorous, predatory insects that had in the past kept the plant-eating insects in check.

Among other materials that are harmful to most forms of life are such metals as mercury, lead, and arsenic. The increasing release of these substances into the biosphere by industrial processes has created conditions that are now generally viewed as harmful to human welfare. Studies have been conducted on metallic pollutants to determine the normal environmental levels, the levels that are toxic to humans, and the extent to which industrial processes are responsible for the problem.

The ultimate control of pollution will presumably involve the decision not to allow the escape into the environment of the substances that are harmful to life, the decision to contain and recycle those substances that could be harmful if released into the environment in excessive quantities, and the decision not to release into the environment substances that persist and are toxic to living things. Essentially, therefore, pollution control does not mean an abandonment of existing productive human activities but their reordering so as to guarantee that their side effects do not out weigh their advantages.

COURTESY: BRITANNICA ENCYCLOPEDIA.

OZONE LAYER DEPLETION

OZONE LAYER DEPLETION AND ITS EFFECT

Ozone is present in all atmospheric regions. But the formation and transformation of ozone takes place in stratosphere. This layer of the atmosphere plays a vital role on life on the earth. Ozone absorbs the UV radiation from the sun, thereby protecting life on our planet. Ozone formation occurs rapidly in the atmosphere above the equatorial regions, where solar radiations is more intense. Much of this ozone is transferred to the poles by the air masses, which moves in horizontal direction.

In stratosphere the air masses only move in a horizontal direction. Due to this condition, pollutants can remain in stratosphere for hundreds of years. A prime destroyer of ozone is Chloroflurocarbons

The pollutants especially that of aerosol(from the rockets and aircrafts) CFCs, HFC’s (fossil burning) etc gets dispersed in the air and can reach high region of the stratosphere(upto 60 miles above the earth ). These pollutants in stratosphere destroy the ozone layers. The continous attack by the pollutants leads to the thinning of ozone layer. Thinning of ozone layer was termed as ozone hole. The depletion of ozone layer leads to penetration of more ultra violet radiation on biosphere. Increased UV radiation elevates the incidence of cataract, skin diseases (skin cancer) and affects the functioning of the immune system.

Damages nucleic acids in the living organisms. UV radiation inhibit photosynthesis in plants and phytoplankton, which in turn affect the whole food chain.

What are CFC’s?

Chloroflurocarbons constitute a family of man made chemical compound. It was invented in the 1930’s. they are non-toxic and harmless to handl. CFC’s are extremely stable and non-flammable. This stability gives them a long life span in the atmosphere allowing its transport to the stratosphere. In stratosphere UV radiation releases chlorine from the rest of the molecule. A single chlorine atom can destroy thousands of molecules of ozone. CFC is used in refrigerators.

GREEN HOUSE EFFECT

The green house effect is a warming that helps to maintain an average global temperature of approximately 60’ farhenheit. During this process sunlight enters earths atmosphere as a short wave radiation which is absorbed by earth’s surface. The planet becomes heated and emits lomg wave radiation towards the atmosphere in which the green house gases absorb them, and in the process gets energitized and emits energy in all directions. Due to this process the temperature of the earth is increasing.

According to the National Academy of sciences the earths surface temperature has risen by about 1’F in the past century.

Problem arises even due to the increase in the concentration of these green house gases. The 20^th century warmest year occurred in the 1998. the snow cover in the northern hemisphere and the ice of the Artic shelf has decreased globally. The sea level has risen by 418 inches over the past century.

Man made green house gases which are found to be the most heat absorbant are hydroflurocarbons(HFC’s), perfluorocarbons (PFC) and sulphur hexafluoride(SF6).

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