In the earlier Chapters, you have read about the population, biotic community and delicately balanced functioning of ecosystem. You have studied in Chapter 19 that increased resource use by people, depletion of fossil fuel reserves, and the large scale changes in land use systems are having a large impact on all components of the environment. Pollution is an undesirable change in physical, chemical or biological characteristics of our air, land or water, caused by excessive accumulation of pollutants (substance causing pollution). These changes will waste or deteriorate our raw-material resources and the environment. Pollution adversely affects biological species, including humans. It damages our industrial processes, living conditions and cultural assets. Other significant changes brought about through human activities are changes in the lower atmosphere. These occur due to the increased in concentration of carbon dioxide and other greenhouse gases, and the depletion of stratospheric ozone layer. These environmental changes, occurring on a global scale, are influencing the air, water, land resource, biological diversity as well as human health. In this chapter, we will read about : (i) the causes, effects and control of pollution, (ii) the implications of global environmental changes due to increasing concentration of greenhouse gases, and (iii) the depletion of ozone in the stratosphere and its possible effects.

Kinds of Pollution

Pollution can be classified in many ways. On the basis of part of environment where it occurs most (atmosphere, hydrosphere and lithosphere), it can be classified as air pollution, water pollution and soil pollution. In terms of origin, pollution may be natural (e.g., volcanic eruptions which add tons of toxic gases and particulate matter in the environment), or anthropogenic (man-made, such as industrial pollution, agricultural pollution, etc.). According to the physical nature of the pollutants, the categories include: gases, particulate matter, temperature, noise, radioactivity, etc. These categories can be named as gaseous pollution, dust pollution, thermal pollution, noise pollution, radioactive pollution, etc.

From the ecosystem viewpoint, pollutants can be categorised into non-biodegradable and biodegradable pollutants. Non-biodegradable materials, such as chlorinated hydrocarbon pesticides (dichloro diphenyl trichloro ethane or DDT, benzene bags, used soft-drink cans, etc. are either not degraded or degraded only very slowly by decomposers in the nature. Therefore, non-biodegradable pollutants are difficult to mange, and in most cases there is not treatment process to handled the anthropogenic input of such materials in the ecosystem.

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