The degradation of natural resources can occur not only by the effects of pollutants but also by improper practices of resource utilisation. For example, the formation of fertile top soil takes centuries, but it is removed very easily (soil erosion) due to certain human activities.
(a) Write any four such human activities that lead to soil erosion.
(b) Mention two such problems that have come in the wake of Green Revolution.

Ozone gas is continuously formed by the action of UV rays on molecular oxygen and· also degraded into molecular oxygen. There should be a balance between the formation and degradation of ozone in the stratosphere.
(a) What is meant by ozone hole?
(b) Mention the unit to measure the thickness of ozone. 
(c) When is the ozone hole formed each year?

The pie chart given above shows the relative contribution of the four greenhouse gases to global warming.
(a) Why does a greenhouse warm up?
(b) Identify the gases, marked Band D in the pie diagram.
(c) Which among these gases causes ozone hole? Mention its relative contribution to global warming.

Greenhouse effect is a naturally occurring phenomenon that is responsible for heating earth's surface and atmosphere. Earth's surface emits heat in the form of infrared radiation, but most of it is absorbed by certain gases, called greenhouse gases, leading to global warming.
(a) Name two gases that contribute the most to global warming and mention their relative contribution towards this.
(b) What would have been the temperature of earth without greenhouse effect?
(c) What is the mean temperature ofthe earth now?

With the revolution of information technology, it has become an integral part of everyone's life, both in rural and urban India.
(a) Write howe-wastes are generated?
(b) How have the developed countries exploited the developing countries with respect to e-waste management?
(c) Mention the correct solution for the treatment of e-wastes.

DDT content in the water of a lake that supplies drinking water to the nearby villages was found to be 0.004 ppm. The pelicans of that area are reported to have 2.6 ppm of DDT. Answer the following questions based on the above observation.
(a) Why has the concentration of DDT increased in these birds?
(b) What possible harm will this cause to the bird population?
(c) Name the phenomenon.

In 1990s, due to the enormous vehicular traffic, Delhi ranked fourth among the most polluted cities of the world. The remedial measures taken by the Delhi Government brought marked improvement in the air quality by 2005
(a) Mention any four measures taken by the Delhi Government that reduced vehicular air pollution in Delhi.
(b) What is the norm set by Euro II for petrol and diesel vehicles?.

Observe the diagram of the catalytic converter given above and answer the following questions.
(a) Name the best fuel for vehicles fitted with catalytic converter. Justify your answer.
(b) What happens to nitric oxide and carbon monoxide in the automobile exhaust, when passed through the catalytic converter?
(c) Name any two metals used as catalyst in the catalytic converter.

Looking at the deteriorating air quality because of air pollution in many cities of our country, the citizens are very much worried and concerned about their health. The doctors have declared health emergency in the cities, where the air quality is very poor/hazarduous.
(a) Mention any two major causes of air pollution.
(b) Write any two harmful effects of air pollution on plants.
(c) Mention any two factors on which the harmful effects of air pollution on organisms depend.

A schematic representation of the functioning of an electrostatic precipitator is given above. Answer the following questions:
(a) ame two sites where installation of electrostatic precipitator is necessary.
(b) Mention a drawback of an electrostatic precipitator.
(c) How does a scrubber differ from this?