Question

Write short notes on
(a) green house effect
(b) photochemical smog
(c) Acid rain
(d) chlorofluorocarbons
(e) electrostatic precipitator
(f) ozone depletion

Answer 1

Pollution is defined as any undesirable change in the physical, chemical, and biological characteristics of air, water, and soil, which adversely affects the living organisms.

Complete answer: (a) Greenhouse effect: Greenhouse effect is a naturally occurring phenomenon, in which the shortwave radiations are absorbed and the longwave radiations are reflected by the earth and are responsible for the heating of earth surface and atmosphere.
(b) Photochemical smog: It contains secondary pollutants or photochemical oxidants. Photochemical smog is grey or yellowish-brown, opaque smog formed at high temperature over cities and towns due to still air, emission of nitrogen oxides, and volatile hydrocarbons from automobile exhaust and solar energy. It is having an oxidizing environment.
(c) Acid Rain: Acid rain refers to precipitation with a pH of less than 5. It is in fact a mixture of sulphuric acid and nitric acid; the ratio of the two acids varies depending on the relative quantities of sulphur dioxide and nitrogen oxides present in the atmosphere.
(d) Chlorofluorocarbons: These are nontoxic, noninflammable, chemically inert synthetic gaseous compounds of carbon and halogens. These are increasingly used in refrigerator, air conditioners, fire extinguishers, production of plastic foams, evaporation of industrial solvents as propellants in an aerosol spray.
(e) Electrostatic precipitator: These are the devices to remove smaller particles from the emissions. These devices are very efficient. Here small particles present in dirty air are first charged electrically and then allowed to settle down over differently charged scrubbers.
(f) Ozone depletion: Ozone gas is formed by the action of UV rays on molecular oxygen and is also degraded by UV rays into molecular oxygen; so there should be a balance between the formation and degradation of ozone in the stratosphere.

Additional Information: Pollutant are of two kinds : A biodegradable pollutant and non-biodegradable pollutants.

Note: An international treaty called Montreal protocol was signed act montreal in 1987 .