Entry of pollutants causes disturbances in an ecosystem which manifest themselves into a chain of adverse reactions often very complex in nature.
The degradation of the environment thus brought about can be grouped into various categories based either on the nature and type of environment being affected or the nature and the type of pollutant causing the problem. Based on the nature and type of environment affected the pollution may be of the following three types:
1. Air pollution 2. Water pollution
3. Soil pollution.
However, such a classification does not provide any other information except for the type of habitat being involved. Pollutants are often found to contaminate more than one type of environment and in such cases the discussions tend to overlap.
Based on the nature of the pollutant as well as the type of habitat involved in pollution, the present authors prefer to classify Environmental pollution into the following two categories:
This category includes pollution caused by pollutants which are discharged on earth's surface -both on land and in water. As the biosphere forms a thin crust over land surface as well as in water, these pollutants interact with it. While the constituents of the biosphere are adversely affected the pollutants are also biologically degraded into simple, harmless compounds and are finally eliminated. The following four types of pollutants may be distinguished in this category:
1. Simple Biodegradable Pollutants:
These include simple wastes which are easily and quickly degraded into harmless constituents. Domestic wastes, organic matter of plant and animal origin, faecal matter, blood, urine etc. are placed in this group.
2. Complex Biodegradable Pollutants:
These include wastes which are resistant to degradation by biological agencies. They are degraded very slowly in the environment arid persist for long durations. It is due to their persistent nature that they cause problems different from those caused by simple bio-degradable wastes. Synthetic chemicals, crude etc. are placed in this group.
3. Pollution Caused by Physical Agents:
These include the pollution caused by harmful I and irritating physical agents such as heat, noise and radiation etc. Thermal, Noise and Radio-active pollutants are placed in this group.
(B) The Pollution of Earth's Atmosphere:
This category includes gases, vapours and fine particulate material which escape into the atmosphere. They pollute the air around us and come in contact with biosphere only when they are unable to go high up in the atmosphere. At higher altitudes, where the biosphere is absent they cause problems of a radically different nature from those caused by pollutants of earth's surface. Most of these pollutants are finally brought down to earth's surface along with precipitation to be converted to harmless form on land surface or in aquatic systems.