Cattle ranches are known to causes acute green house effect. This is due to

• mechanized milking practices

• methanogenic bacteria in rumen

• decomposition of left over fodder

• decomposition of organic remains in faeces.

A large quantity of urban sewage is drained to nearby village river. Which among the given conditions would happen after mixing of sewage into the river?

(i) Biochemical oxygen demand (BOD) of receiving water body increases.

(ii) Dissolved oxygen of receiving water body decreases.

(iii) It will not cause mortality among fishes and other aquatic creatures.

(iv) It will lead to nutrient enrichment of receiving water body.

• (i), (ii) and (iii)

• (i), (ii) and (iv)

• (ii) and (iii)

• (iii) and (iv)

93.

Which of the following is a secondary pollutant?

• Carbon dioxide

• Nitrogen oxides

• Peroxyacyl nitrates

• All of these

Assertion : Presence of large amounts of nutrients in water body causes excessive growth of planktonic algae.

Reason : It is due to biomagnification.

• If both assertion and reason are true and reason is the correct explanation of assertion.

• If both assertion and reason are true but reason is not the correct explanation of assertion

• If assertion is true but reason is false

• If both assertion and reason are false

In vehicles, catalytic converters are used

• to increase mileage of vehicles

• to convert CO₂ into carbonates

• to increase the efficiency of lead mixed petrol

• to convert CO to CO₂

Assertion: Amount of organic biodegradable compounds present in water is measured by the BOD of that water.

Reason: During biodegradation of biodegradable organic compounds, oxygen is released by bacteria

• If both assertion and reason are true and reason is the correct explanation of assertion

• If both assertion and reason are true but reason is not the correct explanation of assertion

• If assertion is true but reason is false

• If both assertion and reason are false.

Assertion: Algal blooms are formed in nutrientless water.

Reason: Algal blooms in water turn it unfit for human consumption, but cause enormous growth of fish.

• If both assertion and reason are true and reason is the correct explanation of assertion

• If both assertion and reason are true but reason is not the correct explanation of assertion

• If assertion is true but reason is false

• If both assertion and reason are false.

A lake near a village suffered heavy mortality of fishes within a few days. Consider the following reasons for this

• Lots of urea and phosphate fertilizer were used in the vicinity.

• The area was sprayed with DDT by an aircraft.

• The lake water turned green and stinky.

• Phytoplankton populations in the lake declined initially thereby greatly reducing photosynthesis.

Ozone in stratosphere extends

• 10 - 20 km

• 20 - 25 km

• 15 - 30 km

• 25 - 40 km

Assertion: Dimethyl mercury is a highly persistent pollutant that accumulates in food chains.

Reason: Mercury pollution is responsible for minamata.

• If both assertion and reason are true and reason is the correct explanation of assertion

• If both assertion and reason are true but reason is not the correct explanation of assertion

• If assertion is true but reason is false

• If both assertion and reason are false.