Summary

Environmental chemistry is the scientific study of chemical and biochemical processes occurring in the environment; World Environmental Day is celebrated on 5 June every year.

Environmental pollution is the effect of undesirable changes in the surroundings that have harmful effects on living things. Pollutants are generally classified as rapidly degradable (e.g. discarded vegetables), slowly degradable (e.g. agricultural waste), and non-biodegradable (e.g. DDT, plastic materials).

Atmospheric pollution includes tropospheric and stratospheric pollution. The troposphere and stratosphere greatly affect the biosphere of the earth, which is why the study of pollution in these two regions is most important. Tropospheric pollution: the troposphere is the lowest region of the atmosphere, in which man, animals and plants exist; gaseous pollutants like SOx, NOx, CO, CO₂, O₃ and hydrocarbons, and particulate pollutants like dust, mist, fumes and smog, cause pollution in the troposphere.

Acid rain: when the pH of rain water becomes lower than 5.6, it is called acid rain. Acid rain is a byproduct of various human activities that emit sulphur oxides and nitrogen oxides into the atmosphere. It damages buildings, statues and other monuments; acid rain falling into water reservoirs like rivers and ponds also adversely affects microbes, aquatic plants and fishes.

Greenhouse effect: the process of warming up of the earth is known as the greenhouse effect, or global warming. CO₂, CH₄, O₃, CFC, N₂O and water vapour present in the atmosphere act as greenhouse gases; the heat-retaining capacity of a greenhouse gas is called its Global Warming Potential (GWP). The GWP-based sequence of the greenhouse gases covered in this unit is CFC > N₂O > CH₄ > CO₂.

Stratospheric pollution: the stratosphere extends above the troposphere, up to about 50 km above earth's surface. Depletion of the ozone layer: the ozone layer present in the stratosphere protects living species against harmful UV rays from space, but Ozone Depletion Substances (ODS) used by humans deplete the ozone layer. To create awareness of this across the whole world, the United Nations decided to celebrate 16 September of every year as "Ozone Layer Protection Day."

Water pollution: water is the elixir of life, but it is polluted by point and non-point sources. Institutions like the World Health Organization (WHO), the Bureau of Indian Standards (BIS) and the Indian Council of Medical Research (ICMR) have prescribed standards for the quality of drinking water.

Soil pollution: the lithosphere with a humus cover is known as soil. The topsoil provides the water and all the nutrients required by plants for their growth. Industrial waste, artificial fertilisers and pesticides result in soil pollution. …