Pollution, Solid & Radioactive Wastes

1 Mark Questions

1.State the cause of accelerated eutrophication. [Delhi 2014]

Ans. Effluents from industries and domestic sewage and other human activities are the causes of accelerated eutrophication,

1. Inspite of being non-polluting, why are there great apprehensions in using nuclear energy for generating electricity? [Foreign 2014]

Ans. Despite being non-polluting, there are great apprehensions in using nuclear energy for generating electricity because of

1. danger of accidental leakage.
2. lack of safe disposal methods of radioactive waste.
3. Why is the use of unleaded petrol recommended for motor vehicles equipped with catalytic convertors? [All India 2013,2012 Foreign 2010] or

Why are owners of motor vehicles equipped with catalytic convertors advised to use unleaded petrol? [Delhi 2009]

Ans. Lead found in petrol corrode the catalytic rods of platinum, rhodium which act as the catalyst in catalytic convertor and decreases its efficiency. Thus, unleaded petrol is recommended for motor vehicles equipped with catalytic convertors

1. Why is Eichhornia crassipes nick named as Terror of Bengal? [Delhi 2012]

Ans. The plant Eichhornia crassipes is nick named as the Terror of Bengal' because it grows at an alarming rate and spreads on the surface of the water body. This cuts out light and also causes an increase in the oxygen demand. Thus, causing the death of fishes and other aquatic organisms,

1. How do algal blooms affect the life in water bodies? [All India 20113]

Ans. Algal blooms cause deterioration of the water quality. They reduce the dissolved oxygen content of water and cause mortality (death) of aquatic animals like fish. They also secrete chemicals, toxic to humans and many other animal

1. Eichhornia crassipes is an alien hydrophyte introduced in India. Mention the problems posed by this plant. [All India 2010c]

Ans. Eichhornia crassipes (water hyacinth) is the world's most problematic aquatic weed. It grows abundantly in eutrophic water bodies and imbalances water ecosystem. It blocks the water, ways and growth of other organisms due to its excessive growth

1. Given below are a few impurities in Urban wastewater. Select two colloidal impurities:

ammonia, faecal matter, silt, bacteria, calcium. [All India 2009c]

Ans. Faecal matter and bacteria are two colloidal impurities suspended in urban waste

1. Name the world's most problematic aquatic weed. What is the nature of the waterbody in which the weeds grow abundantly? [Delhi 2008]

Ans. The world's most problematic weed is Eichhornia crassipes (water hyacinth). In Eutropic water bodies, weeds grow abundantly

2 Marks Questions

1. Name two metals used in a catalytic convertor. How do they help in keeping the environment clean? [Delhi 2014c]

Ans. The two metals used in a catalytic convertor are platinum palladium and rhodium (any two).

The catalytic convertors fitted in automobiles reduce the emission of poisonous gases by converting the unburnt hydrocarbons into CO₂ and water, carbon monoxide to CO₂ and Nitric oxide (NO) to nitrogen, while the exhaust is passed through them.

10.'Fish mortality increases with influx of nutrients in a freshwater body'. Write two reasons. How will the influx of nutrients affect the BOD level of this waterbody? [All India

2014c]

Ans. Fish mortality increases with influx of nutrients in a freshwater body because

1. Abundant nutrients encourage the growth of free floating algae and plants, thereby increasing organic matter.
2. With the increase in organic matter and its deposition, the water body becomes shallows and warmer. Further deteroriation of organic matter makes the environment toxic and unfit for survival of aquatic life, i.e. fishes.

The influx of nutrients increases the BOD level of water body, as the microbes flourishing in it consume up all the oxygen in degrading the organic matter. As the Biochemical Oxygen Demand (BOD) increases, the Dissolved Oxygen (DO) decreases, making the water body unfit