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Respiration
Oxygen gas is poisonous to bacteria that causes
gangrene.
Human benefits
Pure oxygen is used to ensure the complete
combustion of different chemicals.
Oxygen is used to treat water and cut and weldmetals.
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Atmospheric oxygen
-is an important part of the
Earth's atmosphere and of the conditions that
allow for life on Earth.
Sources of oxygen:
(1.) break up of water vapour through process
driven by sunlight - water molecules disassociated
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(2.) Photosynthesis- is the process of converting light energy to
chemical energy and storing it in the bonds of sugar.- Oxygen is produced by plants
and cyanobacteria and phytoplankton in the ocean,.- photosynthesis and aerobic respiration involve
the alternate release and utilization of oxygen
Aerobic respiration-is a process of cellular respiration thatuses oxygen in order to break down molecules-creates a substance known as adenosine
triphosphate (ATP) * Photosynthesis accounts for 98% of the world's
atmospheric oxygen, while the break up of watermolecules by ultraviolet radiation composes the other1-2%.
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Nevertheless, at some time in Earths history,
the amount of oxygen introduced into the
atmosphere had to exceed the amount taken up in
respiration and geological processes. Part of theoxygen present in the atmosphere is from the past
imbalance between photosynthesis and
respiration in plants.
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Photosynthesis Respiration Requires sunlight Does not need sunlight Occurs in cells Occurs in cells
with chlorophyll
Uses water Gives off water Uses carbon dioxide Releases carbon dioxide Gets energy from sun Releases energy from
sugar Makes sugar Breaks down sugar
Releases oxygen Uses oxygen
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The main reservoirs of oxygen cycle:
Water ( H2O )
Carbon dioxide ( CO2 )
Atmosphere
Lithosphere
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Sources of atmospheric oxygen :
Most of the Hydrogen escapes intospace
Water molecules are disassociatedto produce hydrogen and oxygen
Water Vapor break-up
SUNLIGHT
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Exchange Pools
Plants-Take in carbon dioxide from the atmosphere
and then releases oxygen in the atmosphere
through the process ofPhotosynthesis
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The other main source of atmospheric
oxygen is photosynthesis, which
produces sugars and oxygen from
carbon dioxide and water
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Phytoplankton and Cyanobacteria
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Weathering processes initiated by organisms
can also free oxygen from the lithosphere.
Plants and animals extract nutrient mineralsfrom rocks and release oxygen in the process.
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Oxygen CyclesOxygen Cycles
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The Oxygen Cycle in the
Biosphere
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In the biosphere the main cycles are respiration andphotosynthesis.
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The OxygenThe Oxygen CCycle in theycle in the
HydrosphereHydrosphere
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OxygenOxygen in water is known asin water is known as dissolved oxygendissolved oxygen or DOor DO..
1. diffusion from the
surrounding air
2. aeration (rapid movement)
3. as a waste product of
photosynthesis.
How does oxygen get into water?
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When the water in a stream enters a pond,When the water in a stream enters a pond,
microorganisms in the pond begin to metabolizemicroorganisms in the pond begin to metabolize
(break down) organic matter, consuming oxygen in(break down) organic matter, consuming oxygen in
the process.the process.
In nature, oxygenIn nature, oxygen
enters water whenenters water whenwater runs over rockswater runs over rocks
and creates tremendousand creates tremendous
amountsamounts of surfaceof surface
area.area. The high surfaceThe high surface
area allows oxygen toarea allows oxygen totransfer from the airtransfer from the air
into the water veryinto the water very
quickly.quickly.
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TheThe OxygenOxygen CycleCyclein the Lithospherein the Lithosphere
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The lithosphere mostly
fixes oxygen in mineralssuch as silicates and
oxides. Most of the time
the process is
automatic all it takes is
a pure form of anelement coming in
contact with oxygen
such as what happens
when iron rusts.
An example of surface weathering chemistry
is formation of iron-oxides (rust):
4FeO + O2 2Fe2O3
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Marine organisms in the biosphere create calcium
carbonate shell material (CaCO3) that is rich in oxygen.
When the organism dies its shell is deposited on theshallow sea floor and buried over time to create the
limestone rock of the lithosphere.
Weathering processes
initiated by organisms
can also free oxygen
from the lithosphere.
Plants and animals
extract nutrient
minerals from rocksand release oxygen in
the process
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The Oxygen Cycle in theThe Oxygen Cycle in the
AtmosphereAtmosphere
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In the atmosphere Oxygen is freed by the process
called photolysis. This is when high
energy sunlight breaks apart oxygen bearing
molecules to produce free oxygen.
One of the most well known photolysis it the ozonecycle. O2 oxygen molecule is broken down to atomic
oxygen by the ultra violet radiation of sunlight. This
free oxygen then recombines with existing O2
molecules to make O3 or ozone. This cycle is
important because it helps to shield the Earth from
the majority of harmful ultra violet radiation turning it
to harmless heat before it reaches the Earths surface.
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Atmosphere
Surface Organic Matter
Reduced Constituentsof the Crust
Burial
Respirationand Decay
NetPrimary
Production
Weathering
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Several human activities yield adverse effects to the amount of
oxygen in the world. These would include:
o Production of ODS or ozone-depleting substances (i.e. CFCs)
o Denudation of forested areas
o Pollution and eutrophication
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In the past, chlorofluorocarbons or CFCs were used in
refridgerants and coolants.
These substances, along with brominated CFCs, undergo photo-
induced scission to produce chlorine or bromine free radicals.
e.g. CCl3FCCl2F. +Cl.
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This yields in a deficiency of ozone molecules which are
responsible for reflecting off harmful UV radiation.
As a result, photosynthetic organisms and other animals that take
part in the CO2-O2 interaction are greatly harmed.
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This pressing concern was addressed by the signing of the
Montreal Protocol on Substances That Deplete the Ozone Layer
It is an international treaty designed to protect the ozone
layer by phasing out the production of numerous substances
believed to be responsible for ozone depletion.
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This unilateral legislative attempt was successful in obtaining
ratification by over 191 countries.
Because of this, it was quick in gaining motion and ultimately
levelled off or decreased atmospheric ODS content.
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Plants, due to their photosynthetic process, contribute much to
the production of oxygen gas.
With the increase of forested areas being converted into
agricultural, commercial or residential land, the potential
photosythetic output of that specific area greatly reduces.
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Needless to say, the more trees that are cut down, the slower the
overall rate of oxygen synthesis becomes.
This also disrupts the equilibrium of the CO2-O2 interaction
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Pollutants in bodies of water also affect the amount of dissolved
oxygen. Some of these may include excess amounts of nitrogen
and sulfur.
This occurence is called eutrophication, which is an increase in
phytoplankton initiated by the addition of artificial or natural
substances such as nitrates and phosphates
through fertilizers or sewage, to an aquatic system.
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As the organisms in the said bloom die, they are acted upon by
bacteria and other decomposers. The presence of these
decomposers depletes the water of its dissolved oxygen and
increases the production of carbon dioxide.
As an adverse effect, hypoxia occurs, which is the depletion of
oxygen in the water, which induces reductions in specific fish and
other animal populations.
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