Definitions [3]
Define ‘eutrophication’.
Eutrophication: “Organic matter in sewage poured into water bodies generally results in excessive growth of algae – which deoxygenates water and produces deadening atmosphere there.”
Define the following term:
Oil spills
Oil spills are the accidental discharges of petroleum into oceans or estuaries. The sources of spills are overturned oil tankers, offshore oil mining, and oil refineries.
Definition: Water pollution
Water pollution means any change in the water quality which makes it unsuitable for use by humans and by other living organisms.
Key Points
Key Points: Water Pollution
- The Water (Prevention and Control of Pollution) Act, 1974, was passed to safeguard water resources. Main sources — domestic sewage, industrial effluents and agricultural run-off.
- BOD (Biochemical Oxygen Demand) is the dissolved oxygen required by microorganisms to decompose organic matter in water. High BOD = high pollution = low oxygen = death of aquatic organisms.
- Algal bloom — excessive growth of planktonic algae due to excess nitrogen and phosphorus. Releases toxins and causes fish mortality. Water hyacinth (Eichhornia crassipes) — "Terror of Bengal" — is an invasive plant that chokes water bodies.
- Eutrophication — natural ageing of a lake by nutrient enrichment. When accelerated by human activities, it is called Cultural/Accelerated Eutrophication, depleting oxygen and killing aquatic life.
- Biomagnification — increase in concentration of toxic pollutants (DDT, mercury) at successive trophic levels. Non-degradable, accumulate in tissues and pass to the next trophic level.
- Thermal pollution — caused by thermal and nuclear power plants releasing hot coolant water, raising water temperature and killing aquatic flora and fauna.
