Question

The process that removes the nitrogen from an atmosphere is
I. Fertilizer production.
II. Eutrophication.
III. Nitrogen fixation.
IV. Denitrification.

A. I and II
B. I and III
C. I and IV
D. II and III
E. II and IV

Answer 1

Hint: Molecular nitrogen present in the atmosphere can be removed through various biological processes and converted into ammonia and other nitrogenous compounds. This ammonia produced can be utilized as compost.

Complete answer:
Fertilizer production: Ammonia is required for the production of nitrogen fertilizers. Hydrogen (obtained from natural gas) is combined with atmospheric nitrogen under high pressure and temperature conditions to form ammonia. This ammonia is utilized in producing nitric acid, both of these can later be combined to form nitrate fertilizers. Moreover, liquid carbon dioxide can also be combined with ammonia for formation of urea.
Nitrogen fixation: Nitrogen fixing bacteria can be utilized for harvesting free nitrogen from the atmosphere which can then be converted into ammonia, nitrites and nitrates for utilization by plant tissues.
Eutrophication and Denitrification doesn’t play a role in removing nitrogen from an atmosphere as Eutrophication is a process of algal accumulation over a water body due to raised level of nutrients particularly nitrogen, phosphorus and limiting factors in the water body required for photosynthesis. This results in depletion of oxygen levels in the concerned water body affecting the aquatic animals thriving in them. On the other hand, denitrification is a microbial process which involves reduction of nitrites and nitrates into molecular nitrogen.

Hence, the correct answer is option (B).

Note: There are certain bacteria present in soil. These bacteria produce nitrogenase enzymes which help in the production of ammonia by pulling nitrogen from the atmosphere. This ammonia acts as a fertilizer. Other bacteria subsequently convert this ammonia to nitrates which can then be utilized by plants.