Give two examples of water pollutants.
Topic: Water pollutants
Answer
- SEWAGE and domestic waste — untreated human excreta and household waste discharged into rivers.
- INDUSTRIAL EFFLUENTS containing heavy metals such as mercury and lead, acids and other chemicals.
(Also acceptable: agricultural run-off containing pesticides and chemical fertilisers; oil spills; hot water from power plants.)
Two examples, one mark each, and they should be different in SOURCE — domestic and industrial — rather than two chemicals.
Adding the EFFECT of each strengthens the answer: sewage carries pathogens causing cholera and typhoid, and its decomposition consumes dissolved oxygen so that fish suffocate; heavy metals accumulate in the food chain, mercury causing Minamata disease and lead damaging the nervous system.
Agricultural run-off is worth knowing for a different reason: fertilisers cause EUTROPHICATION — an explosion of algal growth that covers the surface, blocks light and, when the algae die and decompose, strips the water of oxygen.