Sancho's Pollution Chemistry Lesson Notes Ordinary Level

POLLUTION CHEMISTRY LESSON NOTES FOR ORDINARY LEVEL

OBJECTIVES OF THE TOPIC:

Pollution refers to the introduction of harmful or undesirable substance to the environment

(i.e. the act of making air, water and soil unfit for use). Or

Pollution is the contamination of Earth’s environment with materials that interfere with human

health, the quality of life, or the natural functioning of ecosystems (living organism and their

physical surroundings).

Pollutant is any substance or species produced either by a natural source or by human activity

and produces adverse (unpleasant) effect on the environment. In addition, pollutant is a

substance already present in atmosphere, which spoils the environment by increase of its

concentration due to human activities.

Although some environmental pollution is a result of natural causes such as volcanic eruptions,

most is caused by human activities. Some common examples of pollutants are carbon monoxide,

Pollutant is defined as anything which is in a wrong place, time, and concentration and which

interferes with normal life activities. In addition, pollutant can be defined as the waste product

released into the environment by man’s activity in large enough quantities to be harmful to living

things. Pollutant can be chemical substances or energy in the form of sound (noise), heat or light.

Contaminant is a substance that does not occur in nature but is introduced in significant amount

into the atmosphere by human action or accidentally.

Pollutants are quite often thought be highly toxic substance only, but even the substances that

are normally considered harmless can cause pollution if they are present in undesirable

concentrations or in wrong places at the wrong time. For example, nitrates are added to soil to

increase plant growth but excessive concentration of nitrates in drinking water can be toxic.

There are two main categories of polluting materials, or pollutants.

(a) Biodegradable pollutants are materials, such as sewage, that rapidly decompose by

natural processes. These pollutants become a problem when added to the environment

faster than they can decompose. That is, they become harmless after their natural

destruction, and they cause no permanent harm if dispersed and treated adequately.

(b) Nondegradable pollutants are materials that either do not decompose or decompose

slowly in the natural environment. Once contamination occurs, it is difficult or

impossible to remove these pollutants from the environment. Undegradable pollutants

include heavy metals, pesticides and herbicides, plastics, glass, and they accumulate in

the environment and in food chains, especially in the tissue of animals at a high

concentration.