POLLUTION

Definition

Any damaging or unpleasant change in the environment that results from the physical, chemical, or biological side-effects of human industrial or social activities. Pollution can affect the atmosphere, rivers, seas, and the soil.
Air pollution is caused by the domestic and industrial burning of carbonaceous fuels, by industrial processes, and by car exhausts. Among recent problems are industrial emissions of sulfur(IV) oxide causing acid rain, and the release into the atmosphere of chlorofluorocarbons, used in refrigeration, aerosols, etc., has been linked to the depletion of ozone in the stratosphere. Carbon dioxide, produced by burning fuel and by car exhausts, is slowly building up in the atmosphere, which could result in an overall increase in the temperature of the atmosphere (greenhouse effect). Car exhausts also contain carbon monoxide and lead. The former has not yet reached dangerous levels, but vegetation near main roads contains a high proportion of lead and levels are sufficiently high in urban areas to cause concern about the effects on children. Lead-free gasoline is available. Photochemical smog, caused by the action of sunlight on hydrocarbons and nitrogen oxides from car exhausts, is a problem in several countries. Catalytic converters reduce harmful emissions from car exhausts.
Water pollutants include those that are biodegradable, such as sewage effluent, which cause no permanent harm if adequately treated and dispersed, as well as those which are nonbiodegradable, such as certain chlorinated hydrocarbon pesticides (e.g. DDT) and heavy metals, such as lead, copper, and zinc in some industrial effluents (causing heavy-metal pollution). When these accumulate in the environment they can become very concentrated in food chains. The pesticides DDT, aldrin, and dieldrin are now banned in many countries. Water supplies can become polluted by leaching of nitrates from agricultural land. The discharge of waste heat can cause thermal pollution of the environment, but this is reduced by the use of cooling towers.
In the sea, oil spillage from tankers and the inadequate discharge of sewage effluent are the main problems.
Other forms of pollution are noise from aircraft,traffic,and industry and the disposal of radioactive waste.

Definition

pollution: An undesirable change inthe physical, chemical, or biologicalcharacteristics of the natural environment,brought about by man’s activities.It may be harmful to human ornonhuman life. Pollution may affectthe soil, rivers, seas, or the atmosphere.There are two main classesof pollutants: those that are biodegradable(e.g. sewage), i.e. canbe rendered harmless by naturalprocesses and need therefore causeno permanent harm if adequatelydispersed or treated; and those thatare nonbiodegradable (e.g. heavymetals (such as lead) in industrialeffluents and DDT and other chlorinatedhydrocarbons used as pesticides),which eventually accumulatein the environment and may be concentrated in food chains. Other formsof pollution in the environment includenoise (e.g. from jet aircraft,traffic, and industrial processes) andthermal pollution (e.g. the release ofexcessive waste heat into lakes orrivers causing harm to wildlife). Recentpollution problems include thedisposal of radioactive waste; acidrain; photochemical smog; increasinglevels of human waste; high levelsof carbon dioxide and othergreenhouse gases in the atmosphere(see greenhouse effect); damage tothe ozone layer by nitrogen oxides,chlorofluorocarbons (CFCs), andhalons; and pollution of inland watersby agricultural fertilizers andsewage effluent, causing eutrophication.Attempts to contain or preventpollution include strict regulationsconcerning factory emissions, theuse of smokeless fuels, the banningof certain pesticides, the increasinguse of lead-free petrol, restrictions onthe use of chlorofluorocarbons, andthe introduction, in some countries,of catalytic converters to cut pollutantsin car exhausts.

Agricultural Uses

Pollution is a state of the environment represented by undesirable changes in the physical, chemical or biological characteristics of the biosphere brought about by human activities. Pollution is harmful to humanplant- and animal life. Air, water and soil are the natural resources chiefly affected by pollution.
The two classes of pollutants are: (a) biodegradable materials like sewage, which can be dangerous unless rendered harmless by specific processes, and (b) non-biodegradable materials like Pb, Cd and Hg which are part of industrial effluents.
Dichlorodiphenyltrichloroethane (DDT) and other chlorinated hydrocarbons used as pesticides accumulate in the environment and enter the food chain. Other forms of environmental pollution include noise pollution (such as from aircraft or traffic or industrial processes) and thermal pollution (such as excessive heat released into rivers and lakes causing harm to aquatic life). Populations of organisms thriving abnormally at the expense of other populations may themselves be regarded as pollutants.
Some of the recent pollution problems also stem from acid rain, radioactive waste and photochemical smog. Exorbitant levels of carbon dioxide and other green house gases such as chlorofluorocarbons (CFCs) in the atmosphere damage the ozone layer. Inland waters mixed with agricultural fertilizers, as also sewage effluents, when discharged into the sea, kill marine life.
The need to control environmental pollution in all its aspects is now widely recognized. Attempts to contain or prevent pollution include strict regulations concerning (a) limits on factory emissions, (b) use of smokeless fuel, (c) use of certain pesticides, (d) use of lead-free petrol, (e) limited use of chlorofluorocarbons, and (f) use of catalytic converters to cut pollutants in car exhausts.

Raw materials

Preparation Products