Question

Define pollution. With reference to water pollution, explain biochemical oxygen demand, algal bloom, biomagnification and eutrophication.

Answer 1

a) Pollution is the addition of the undesirable amounts of wastes and contaminants in the soil, water, air or any other resources resulting in the deterioration of the quality.

b) BOD is abbreviated form of Biological Oxygen Demand which is the amount of oxygen required by microbes to break down the organic matter present in a certain volume of a sample of water. The amount of BOD in the water is a measure of the amount of organic material in the water. In polluted water, BOD is high as it contains a large amount of organisms.

c) With time, streams draining into the lake introduce nutrients such as nitrogen and phosphorus, which encourage the growth of aquatic organisms. As the lake's fertility increases, algal bloom occurs. Algal bloom causes the deterioration of water quality and fish mortality and dead remains begin to be deposited on the lake bottom.

d) Biomagnification is the accumulation or increasing bioconcentration of lipophilic pesticides in the top members of the food chain. During biomagnification, the concentration of pesticides goes on increasing according to the food chain and highest values occur in the consumers of the top trophic level.

e) Accelerated eutrophication is the aging of a water body due to nutrient enrichment of its water. This is the condition due to the movement of the chemicals containing nitrates and phosphates in the water system.