Consider the following observations: (I) The pH of rain water is 5.6. (II) The amount of CO2 in the atmosphere is 0.03%. (III) The biochemical oxygen demand is 10ppm. (IV) Eutrophication. A polluted environment is observed under:
A
Both I and III
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B
Both I and IV
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C
Both III and IV
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D
I, III, and IV
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Solution
The correct option is C Both III and IV (I) If thepH of water = 5.5, it means the water is less acidic and contains less dissolved CO2. It is not polluted water.
(II) CO2 = 0.03% it indicates very less pollution.
(III) Biochemical oxygen demand (BOD) is the amount of dissolved oxygen needed (i.e. demanded) by aerobic biological organisms to break down organic material present in a given water sample at certain temperature over a specific time period. BOD = 10.00ppm means polluted water.
(IV) Eutrophication is the process by which over a period of few years, good quality water bodies are rendered useless as a result of over nutrition due to phosphate nitrates and biomass. Thus, this indicates polluted water.