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Here, we review the nitrogen cycle on Earth, its.

. Definition. , nitrate) from the ecosystem and returns it to the atmosphere in a biologically inert form (N 2).

In nature, two principal processes of nitrogen fixation are known.

. As might be expected in view of the importance of the presence of nitrogen in living matter, most—if not all—organic nitrogen compounds are physiologically active. .

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Bacteria play a key role in the nitrogen cycle.

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21% oxygen, O₂. Emissions of Nr released into the atmosphere from agriculture, industry, and urban areas contribute to high levels of fine particulate matter (PM 2.

Emissions of Nr released into the atmosphere from agriculture, industry, and urban areas contribute to high levels of fine particulate matter (PM 2. .

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04%), and trace gases.

Nitrogen is also found in the Earth's crust as part of organic matter and humus.

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In terms of . The. 25% of the atmosphere by mass.

. Water vapor accounts for roughly 0. Nitrogen is a crucially important component for all life. Nitrogen, a component of proteins and nucleic acids, is essential to life on Earth. .

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04 %) and trace gases. Oct 8, 2010 · Despite the importance of nitrogen and its overwhelming abundance in the atmosphere, N 2 is virtually inert; hence, fixed inorganic nitrogen [most commonly nitrate (NO 3 –) and ammonium (NH 4 +) ions] often limits primary productivity in both marine and terrestrial ecosystems (2, 4, 5).

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Here, we review the nitrogen cycle on Earth, its.

It exists as a colorless, odorless, nontoxic gas and makes up about 78 percent of the atmosphere.

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