Pollutants, sources and sinks – Environmental Studies for NCET

Basic concepts

A pollutant is any substance or energy (heat, noise, radiation) released into the environment in amounts that harm living things or materials. Pollution is the undesirable change in the physical, chemical or biological features of air, water or land.

Sources:

Point sources: single, identifiable outlets, such as a factory pipe or chimney.
Non-point (diffuse) sources: spread over a wide area, such as farm runoff carrying fertilisers or city street runoff. These are harder to control.
Natural (volcanoes, dust storms) and anthropogenic (human-made) sources.

Types of pollutant:

Biodegradable: broken down by microbes (sewage, food waste).
Non-biodegradable / persistent: stay for a long time (plastics, DDT, mercury, lead).
Primary (released directly) and secondary (formed in the environment by reactions).

Sinks are places that absorb or store pollutants: oceans absorb CO₂, forests take up CO₂, and soil and sediments trap heavy metals.

Biomagnification: persistent chemicals become more concentrated at each higher level of a food chain, so top predators (fish-eating birds, humans) carry the highest doses. DDT thinned the eggshells of birds of prey.

Health and ecosystem impacts

Mercury: Minamata disease (Japan, 1950s).
Cadmium: itai-itai disease (Japan).
Arsenic in groundwater: skin lesions and cancer (parts of West Bengal and Bangladesh).
Excess fluoride: fluorosis (bones and teeth).
Nitrate in drinking water: “blue baby syndrome”.
Lead: damages the nervous system, especially in children.

Indian pollution laws

Water (Prevention and Control of Pollution) Act, 1974: created the Central and State Pollution Control Boards.
Air (Prevention and Control of Pollution) Act, 1981.
Environment (Protection) Act, 1986: umbrella law after the Bhopal gas tragedy of December 1984 (methyl isocyanate leak).
National Green Tribunal Act, 2010: set up a special court for environmental cases.

Key points

Point vs non-point sources; primary vs secondary pollutants.
Sink = reservoir that absorbs a pollutant.
Biomagnification is greatest at the top of a food chain.
Water Act 1974 (CPCB); Air Act 1981; EPA 1986; NGT 2010.

Exam tips

Match diseases to pollutants; this is a favourite. Know which Act created the pollution control boards (Water Act, 1974).

Common mistakes

Thinking the CPCB was created by the Air Act; it was created under the Water Act, 1974.
Calling farm runoff a point source.
Mixing up Minamata (mercury) and itai-itai (cadmium).

Fertiliser-laden runoff from many farm fields entering a river is an example of a:	Easy
Minamata disease, first reported in Japan in the 1950s, was caused by poisoning with:	Medium
The increase in concentration of a persistent pollutant such as DDT at successive levels of a food chain is called:	Easy
The Central Pollution Control Board was first set up under which Act?	Hard
The Environment (Protection) Act, 1986 was passed soon after which disaster?	Medium