Nitrogen is a major
component of the earth’s atmosphere and is essential for all living organisms. It
enters the food chain through bacteria and algae in the soil. The bacteria then
forms nitrates out of atmospheric nitrogen which is dissolved in soil water by
the roots of plants. Nitrates are then incorporated by the plants to form
proteins, which can then be spread through the food chain. Nitrogen is also
released into the environment when organisms omit waste or die. Decomposers
break down the corpses and wastes into nitrogen in the form of ammonia.
This nitrogen can then be used again by nitrifying bacteria to fix nitrogen for
the plants.
Many human
activities affect the nitrogen cycle including dumping of raw sewage, burning
of fossil fuels, use of inorganic fertilizers, over mining nitrogen and
overharvesting legumes. Dumping of raw sewage contains nitrogenous wastes
therefore when large amounts of nitrogen collect in a water body, eutrophication can result, which is the accumulation
of excess nutrients which causes an algae bloom. The algae quickly deplete
all of the oxygen in the water, making it uninhabitable for fish and other
aquatic organisms. Eutrophication can also result in plant communities
saturated with nitrogen making the soil acidified and uninhabitable. Burning
fossil fuels and wood contributes a large amount of nitric oxide in the
atmosphere. Nitric oxide can combine with oxygen gas to form nitrogen
dioxide, which reacts with water vapour to form nitric acid. This can
precipitate out of the atmosphere in the form of acid rain. The acid can damage
trees and kill fish and other organisms. Overall many human activities are depleting
our source of nitrogen and corrupting the nitrogen cycle.
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