1. GOVT.SCIENCE (AUTO.) COLLEGE
JABALPUR
SESSION : - 2018 - 19
SUBJECT:- ENVIRONMENTAL CHEMISTRY
SUBMITTED TO : -
DR.
SHIKHA SAXENA
SUBMITTED BY : -
HIMANSHU ASATI
M.Sc. - 4th SEM
Sr. No. - 11
TOPIC - NITROGEN CYCLE
2. INTRODUCTION
• The nitrogen cycle is a biogeochemical cycle.
• N itrogen is converted into multiple chemical forms as it
c i r c u l a t e s among the atmosphere, terrestrial and marine
environment.
• Nitrogen availability can effect rate of key ecosystem
process, primary production and decomposition.
• Alteration in global nitrogen cycle has been observed
• Fossil fuel combustion, use of artificial nitrogen
fertilizers and release of nitrogen in waste water.
5. • Conversion of nitrogen to nitrates and nitrites
through atmosphere, industrial and biological
Process is called as nitrogen fixation.
• But most fixation is done by free-living or
symbiotic bacteria known as Diazotrophs.
• These bacteria have the nitrogenase enzyme.
N2
Nitrogen
3H2
2NH3
1 NITROGEN FIXATION
Ammonia
7. • the incorporation of inorganic nitrogen
compounds into organic molecules.
• Nitrates and ammonia are assimilated
or Incorporated into specific tissue.
Nitrogen is assimilated in the f o rm
ammonium ions directly from roots.
2 ASSIMILATION
8.
9. • The remains of all living thing and their waste products
are decomposed by microorganisms in the process of
ammonification which yields ammonia from organic nitrogen.
• Ammonia can leave the soil or be converted into other
nitrogen compounds depending on part of soil condition.
CH3CHNH2COOH +1/2O2
Alanine
Alanine
CH3COCOOH + NH3Deaminase
Pyruvic acid Ammonia
3 AMMONIFICATION
NH3 NH4+
Ammonia Ammonium
10.
11. • The conversion of ammonium to nitrate is performed
mainly by the Nitrifying bacteria.
• In the primary stage of nitrification, the oxidation of
ammonium to nitrite is performed by Nitrosomonas sps.
which further converts in to nitrates.
• Other bacterial species such as Nitrobacter are
responsible for the oxidation of the nitrities to nitrates.
• Ammonia gas is toxic to plants.
4 NITRIFICATION
13. • Denitrification is the reduction of nitrates back
into nitrogen gas (N2), completing the nitrogen cycle.
• This process is performed by bacterial species
such as Pseudomonas and Clostridium in anaerobic
conditions.
• They use the nitrate as an electron acceptor in
the place of oxygen during respiration.
• Denitrification occurs in anaerobic conditions.
5 DENITRIFICATION
14.
15. FORMS OF NITROGEN
• It is in the form of dinitrogen(N2) gas.
• Organic form of nitrogen make up a very h i g h
percentage of the total nitrogen.
• Plants are able to use only very specific
inorganic forms of nitrogen.
• It is present in the form of organic nitrogen,
ammonia, a m monium, nitrite, nitrate,
nitrous oxide, nitric oxide or inorganic nitrogen.
16. MICROBES IN NITROGEN CYCLE
1) Nitrogen fixation through Nitrogenase
symbiotic relationship.
2) bacteria (Deaminase) break down proteins
through t h e process by decay.
3) Nitrosomonas and Nitrobacter help in
nitrification.
4) Pseudomonas/clostridium help in
denitrification.