Theory question 104
Pollution(a) (i) What is pollution? (ii) State four pollutants of water. (b) Describe the effects of each of the pollutants named on aquatic organisms.
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(a)(i) Pollution is the release of harmful substances or energy into the environment in amounts that damage living things or make the environment unpleasant or unsafe.
(ii) Any four: crude oil; sewage; industrial wastes/chemicals (heavy metals such as lead, mercury); fertilizers; pesticides/herbicides; hot water (thermal pollution); detergents; refuse/plastics.
(b) Effects (to match the pollutants named): oil – forms a film that stops oxygen dissolving, clogs gills and feathers, poisons organisms; sewage – decomposers use up oxygen so fish suffocate, spreads disease germs; fertilizers – cause eutrophication: algal bloom, then lack of oxygen and death of organisms; pesticides and heavy metals – poison organisms and build up along the food chain; hot water – lowers dissolved oxygen and kills sensitive organisms; detergents – froth reduces oxygen and harms gills; refuse/plastics – organisms get trapped or swallow them.
Give an effect for each pollutant you list.