Noise pollution

Land pollution

Land pollution involves the deposition on land of solid wastes--e.g., used cars, cans, bottles, plastic containers, paper--that cannot be broken down quickly or, in some instances, cannot be broken down at all by the action of organic or inorganic forces. (The term biodegradable is used to describe those materials that can be decomposed and recycled by biological action.) When such materials become concentrated within any one area, they interfere with organic life and create unsightly accumulations of trash.

Methods of disposal other than recycling include ocean dumping, which creates water pollution and destroys marine habitats; landfill, which often requires the availability of low-lying ground and frequently involves the destruction of marshland or swamps that have high biological value; and burning, which increases air pollution. Obviously, none of these methods is entirely satisfactory, although using landfill to create artificial landscapes, which then are covered with soil and planted with various kinds of vegetation, is a possibility that remains to be fully developed. It is the great quantity of debris produced by urban communities, more so than a shortage of raw materials, that forces the development of more effective means for recycling wastes. Land pollution also involves the accumulation on land of substances in dispersed solid or liquid form that are injurious to life. This has been particularly noticeable with those chemicals (e.g., DDT) that are spread for the purpose of exterminating pests but then accumulate to the extent that they can do damage to many other forms of life.

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.

Дата добавления: 2014-11-16