Introduction
Pollution is an undesirable change in the physical, chemical or biological characteristics of our air, land, and water that may or will harmfully affect human life or that of desirable species, our industrial processes, living conditions, and cultural assets (Odum, 1971)
In other words, pollution is the unfavorable alteration of our environment, largely as a result of human activities (Southwick, 1976).
Types of pollution
Air pollution
Water pollution
Land pollution
Noise pollution
Thermal pollution
Radioactive pollution
Pollutants
certain kinds of byproducts and waste products which when are injected into the biosphere in quantities so great that they affect the normal functioning of ecosystems and have an adverse effect on plants, animals, and man are collectively called pollutants.
Types of pollutants
Pollutants primarily are grouped into the following two types:
1. Natural pollutants.
Certain pollutants such as carbon dioxide, carbon monoxide, Sulphur dioxide, lead, mercury and other trace elements are the consequence of life processes being produced through respiration, feces, urine and body decomposition. With an increase in human population, the pollutants are increasing with alarming rate.
2. Synthetic, man-made
Vast array of synthetic pollutants are increasing continuously with urbanization and industrial growth.
They include pesticides, detergents, pharmaceuticals, cosmetic products, organic acids, aerosols, and metals, etc.
Several of these compounds are extremely stable and persist in the environment for a considerable period posing serious environmental hazards.
Pollutants can be classified into two basic types: nondegradable pollutants and biodegradable pollutants (Odum, 1971).
Non biodegradable
materials and poisons, such as aluminum cans, mercurial salts, long-chain phenolic chemicals that either do not degrade or degrade only very slowly in the natural environment, are called nondegradable pollutants.
Such nondegradable pollutants not only accumulate but are often “biologically magnified” as they move in biogeochemical cycles and along food chains. Also, they frequently combine with other compounds in the environment to produce additional toxins.
Biodegradable pollutants
They include domestic sewage etc. The domestic sewage can be rapidly decomposed by natural processes or in engineered systems (such as a municipal sewage treatment plant) that enhance nature’s great capacity to decompose and recycle.
Problems arise with the biodegradable pollutants when their input into the environment exceeds the decomposition or dispersal capacity.
On the basis of their origin pollutants can be classified as follows.
Primary pollutants
Primary pollutants are the waste or exhaust products driven out because of combustion of fossil fuels and organic matter. These are oxides of Sulphur (SO2 and SO; oxides of CO2); oxides of nitrogen (especially); hydrocarbon (CH; ammonia and compounds of fluorine.
Secondary pollutants
Secondary pollutants are produced by various reactions of primary pollutants. These are sulphuric acid (H2SO4), carbonic acid (H2CO3), nitric acid (HNO3), hydrofluoric acid, ozone and peroxyl acetyl nitrate (PAN).