Nitrogen Cycles

Nitrogen is in the atmosphere as

N₂ (78%)

N₂ is an inert gas and cannot

be used by plants or animals

N₂ can be converted to a usable form via

lightning

N-fixing plants and cyanobacteria

Industrial process (energy intensive)

Nitrogen limits __ growth

plant

Nitrogen is easily lost from

biological systems

Essential (limiting) nutrients

enzymes

amino acids, proteins

pigments (ex: chlorophyll)

Range of valance (oxidation) states

NH₄⁺(-3) to NO₃^- (+5)

What drives the nitrogen cycle?

microbial reactions

Largest Nitrogen Reservoirs

Atmosphere (principal reservoir)

Sedimentary Rocks

Processes in the N Cycle

N₂ fixation

Nitrification

Assimilation

Ammonification

Denitrification

Anammox

DNRA

Assimilatory nitrate reduction

N₂ fixation

Reduced

N₂ → NH₃

Nitrification

Oxidized

NH₃ → NO₃^-

Assimilation

Depends

NO₃^- or NH₃ / NH₄⁺ → Organic N

Ammonification

Depends

Organic N → NH₃

Denitrification

Reduced

NO₃^- → N₂

Anammox

Reduced and oxidized

NH₄⁺ + NO₂^- → N₂

DNRA

Reduced

NO₃^- → NH₃

Assimilatory Nitrate Reduction

Reduced

NO₃^- → NH₃

CO₂ +H₂O → CH₂O + O₂

Common Organic Nitrogen Groups (Oxidation States)

Amines (-3)

Amides (-3)

Nitriles (-1)

Nitro Compounds (+3)

Organic Nitrosonium Groups (+2)

Runoff of fertilizer can lead to serious ___ problems

eutrophication

NO & NO₂ are gases associated with production of _____

O₃ in troposphere

__ is a greenhouse gases associated with destruction of O₃ in the stratosphere

N₂O