Solved Examples on Environmental Issues
Question1: Which of the following does not occur when the sewage is discharged into water? [Delhi PMT 2003]
(a) Increase in O2
(b) Cyanophycean blooms occur
(c) Depletion of O2 layers
(d) Eutrophication
Answer: a
Solution: Depletion in O2 does not occur when the sewage is discharged into water.
Question2: Biological Oxygen Demand (BOD) is a measure of [AIIMS 2003]
(a) Industrial wastes poured into water bodies
(b) Extent to which water is polluted with organic compounds
(c) Amount of carbon monoxide inseparably combined with haemoglobin
(d) Amount of oxygen needed by green plants during night
Answer: b
Solution: The amount of dissolved oxygen needed by aerobic biological organisms in water body to break down organic material present in a given water sample at certain temperature over a specific time period is called Biological Oxygen Demand. Thus, Biological Oxygen Demand (BOD) is a measure of extent to which water is polluted with organic compounds
Question3: Positive pollution of soil is due to [CBSE PMT 2002]
(a) Excessive use of fertilizers
(b) Addition of wastes on soil
(c) Reduction in soil productivity
(d) All of these
Answer: d
Solution: Positive pollution of soil is because of overuse of chemical fertilizers, air pollutants and pesticides along with herbicides and fumigants.