• Biogeochemical cycles: The
chemical interactions (cycles) that
exist between the atmosphere,
hydrosphere, lithosphere, and
• Biogeochemical cycles are
components of the broader cycle that
govern the functioning of planet Earth
• The transfer of matter involves biological,
geological and chemical processes; hence
the name biogeochemical cycles derives.
Biogeochemical cycles may also be
referred to as cycles of nature because
they link together all organisms and
abiotic features on earth (see Figure at
next slide). Matter is continually recycled
among living and abiotic elements on
• biogeochemical cycles facilitate the
transfer of matter from one form to
another and from one location to another
on planet earth. Additionally,
biogeochemical cycles are sometimes
called nutrient cycles, because they
involve the transfer of compounds that
provide nutritional support to living
• Parts that comprise planet earth have
been categorized into four spheres
(regions). One is the sphere which has
life and it is called the biosphere (it is the
region occupied by living organisms such
as plants, animals, fungi) and the other
three spheres are largely devoid of life,
• lithosphere (region occupied by soil, land
and the earth crust), atmosphere (air and
space) and hydrosphere (areas covered
by water such as rivers, lakes and
oceans). However, where the biosphere
overlaps the lithosphere, atmosphere or
hydrosphere, there is a zone occupied by
Categories of biogeochemical
• Biogeochemical cycles differ in their
pathways, and on this basis the
biogeochemical cycles have been
categorized into two:
Phosphorus cycle Sulfur cycle
Carbon cycle Oxygen cycle
Nitrogen cycle Hydrological cycle
• these cycles involve the transportation of
matter through the ground to water; that is to
say from the lithosphere to the hydrosphere.
Phosphorus is commonly found in water, soil and
sediments. Phosphorus cannot be found in air in
the gaseous state. This is because phosphorus is
usually a liquid at standard temperatures and
pressures. Phosphorus is mainly cycled trough
water, soil and sediments. However, very small
particles in the atmosphere may contain
phosphorus or its compounds. Phosphorus
moves slowly from deposits on land and in
sediments, to living organism , and much more
slowly back into the soil and water sediment. The
phosphorus cycle is the slowest one of the
Fig. 3-31, p. 77
Marine Sediments Rocks
settling out weatheringsedimentation
in Soil Water,
The cycle basically starts out in
the earth’s soil. The soil contains
phosphate and when something
grows out of the soil it should have
phosphate as well.
When the plants grow they are
consumed by herbivore and
The animal’s waste or the animal’s
body when it dies becomes detritus.
Detritus is non-
the detritus goes
deep into the soil,
detritivores in the
and become the
and the cycle
• Sulfur in its natural form is a solid, and
restricted to the sedimentary cycle in this
form. It is transported by physical
processes like wind, erosion by water, and
geological events like volcanic eruptions.
However, in its compounds such as sulfur
dioxide, sulfuric acid, salts of sulfate or
organic sulfur, sulfur can be moved from
the ocean to the atmosphere, to land and
then to the ocean through rainfall and
Effects of Human Activities
on the Sulfur Cycle
• We add sulfur dioxide to the atmosphere
–Burning coal and oil
–Refining sulfur containing petroleum.
–Convert sulfur-containing metallic ores
into free metals such as copper, lead,
and zinc releasing sulfur dioxide into
• these involve the transportation of
matter through the atmosphere.
Common example of gaseous cycles
• Carbon is one of the most important
elements that sustain life on earth. Carbon
dioxide and methane gases (compounds
of carbon) in the earth's atmosphere has a
substantial effect on earth's heat balance.
It absorbs infrared radiation and hence
may contribute to global warming and
MARINE CARBON CYCLE
Slide 35Slide 35Slide 35
atmosphere and ocean
Marine food webs
Marine sediments, including
formations with fossil fuels
Combustion of fossil fuels
Carbon Cycle Diagram
Carbon in Atmosphere
carbon to make
break down dead
part of oil or
Fossil fuels are
is returned to
• Fossil fuels release carbon stores very
• Burning anything releases more carbon
into atmosphere — especially fossil fuels
• Increased carbon dioxide in atmosphere
increases global warming
• Fewer plants mean less CO2 removed
• Nitrogen gas is the most abundant
element in the atmosphere and all the
nitrogen found in terrestrial ecosystems
originate from the atmosphere. The
nitrogen cycle is by far the most important
nutrient cycle for plant life.
Effects of Human Activities
on the Nitrogen Cycle
• We alter the nitrogen cycle by:
–Adding gases that contribute to acid rain.
–Adding nitrous oxide to the atmosphere
through farming practices which can warm
the atmosphere and deplete ozone.
–Contaminating ground water from nitrate
ions in inorganic fertilizers.
–Releasing nitrogen into the troposphere
Effects of Human Activities
on the Nitrogen Cycle
• Human activities
fertilizers now fix
than all natural
Figure 3-30Figure 3-30
Oxygen cycleOxygen cycle
• The oxygen cycle describes the
movement of oxygen within and between
its three main reservoirs: the atmosphere,
the biosphere, and the lithosphere. The
main driving factor of the oxygen cycle is
photosynthesis and because of this,
oxygen and carbon cycles are usually
linked and the two cycles are collectively
called oxygen-carbon cycle.
Fig. 3-26, p. 72
Groundwater movement (slow)
from land Evaporation
from ocean Precipitation
• This is some times called the water cycle.
Water is the most important chemical of
life for all living organisms on earth. Water
in the atmosphere is usually in form of
vapor but condenses to liquid water and
can solidify when temperatures are 00
form ice. Ninety three percent of water on
earth is in solid state mainly comprising
the ice caps and glaciers of Polar
• The earth has a limited amount of water. That water
keeps going around and around and around and
around and (well, you get the idea) in what we call
the "Water Cycle". This cycle is made up of a few
• Evaporation or (Transpiration)
• Accumulation or (Collection)
• Ground Water
• Evaporation is when the sun heats up
water in rivers, lakes or the ocean and
turns it into vapor or steam. The water
vapor or steam leaves the river, lake or
ocean and goes into the air.
• Water vapor in the air gets cold and
changes back into liquid, forming
clouds. This is called condensation.
• You can see this at home when you take a
shower and the windows and mirrors in
the bathroom fog up. You can also do this
by breathing on a mirror.
• Precipitation occurs when so much
water has condensed that the air cannot
hold it anymore. The clouds get heavy
and water falls back to the earth in the
form of rain, hail, sleet or snow.
• When water falls back to earth as
precipitation, it may fall back in the
oceans, lakes or rivers or it may end up
on land. When it ends up on land, it will
either soak into the earth (infiltration)
and becomes part of the “ground water”
that plants and animals use to drink or it
may run over the soil and collect in the
oceans, lakes or rivers where the cycle
starts all over again.
HUMAN IMPACTS TO WATER
1. Water withdrawal from streams, lakes and
groundwater. (salt water intrusion and groundwater
2. Clear vegetation from land for agriculture, mining,
road and building construction. (nonpoint source
runoff carrying pollutants and reduced recharge of
3. Degrade water quality by adding nutrients(NO2, NO3,
PO4) and destroying wetlands (natural filters).
4. Degrade water clarity by clearing vegetation and
Nature of elements transported in
• When living organisms die and decay, their
body structures disintegrate and may be
reduced to constituent molecules. Depending
on the region where disintegration of the
organisms occurred, the component molecular
elements then join the biogeochemical cycle.
Elements transported in the biogeochemical
cycles have been categorized as:
• 1. Micro elements – these are elements
required by living organisms in smaller
amounts. Examples of such elements include
boron used mainly by green plants, copper
used by some enzymes and molybdenum
used by nitrogen-fixing bacteria.
• 2. Macro elements – these are elements
required by living organisms in larger amounts.
Examples of such elements include carbon,
hydrogen, oxygen, nitrogen, phosphorous,
The importance of
• Biogeochemical cycles serve a variety of
functions at ecosystem level and in
ensuring survival of various organisms
including humans. Below are some of the
importance's of biogeochemical cycles.
• enable the transformation of matter from one
form to another.
• enable the transfer of molecules from one
locality to another.
• facilitate the storage of elements
• assists in functioning of ecosystems.
• cycles link living organisms with living
organisms, living organisms with the non living
organisms and nonliving organisms with non
• regulate the flow of substances.
Natural capital: simplified model of the phosphorus cycle. Phosphorus reservoirs are shown as boxes; processes that change one form of phosphorus to another are shown in unboxed print. QUESTION: What are three ways in which your lifestyle directly or indirectly affects the phosphorus cycle?
Natural capital: simplified model of the sulfur cycle. The movement of sulfur compounds in living organisms is shown in green, blue in aquatic systems, and orange in the atmosphere. QUESTION: What are three ways in which your lifestyle directly or indirectly affects the sulfur cycle?
Natural capital: simplified model of the hydrologic cycle.
Biogeochemical cycles enable the transformation of matter from one form to another. This transformation enables the utilization of matter in a form specific to particular organisms. For example humans utilize water in liquid form. Through the hydrological cycle, water vapour is condensed to liquid and ice converted to liquid water. Nitrogen, despite its abundance in the atmosphere it’s often the most limiting nutrient for plant growth. This problem occurs because most plants can only take up nitrogen in two solid forms: ammonium ion (NH4+) and the ion nitrate (NO3-). Therefore, biogeochemical cycles enable the provision of elements to organisms in utilizable forms.
Biogeochemical cycles enable the transfer of molecules from one locality to another. Some elements such as nitrogen a re highly concentrated in the atmosphere, but some of the atmospheric nitrogen is transferred to soil through the nitrogen cycle (which is a biogeochemical cycle).
Biogeochemical cycles facilitate the storage of elements. Elements carried through the biogeochemical cycles are stored in their natural reservoirs, and are released to organisms in small consumable amounts. For example through the nitrogen cycle and with the help of the nitrogen fixing bacteria, green plants are able to utilize nitrogen in bits though it is abundant in the atmosphere.
Biogeochemical cycles assists in functioning of ecosystems. An ecosystem is a system that properly functions in a state of equilibrium, and when ever any imbalances occur, the ecosystem through the biogeochemical cycles restores to the equilibrium state; this may take a few days or many years. The adjustment is such that the disturbing factor is eliminated.
Biogeochemical cycles link living organisms with living organisms, living organisms with the non living organisms and nonliving organisms with non living organism. This is because all organisms depend on one another and most especially, the biotic (living component) and a biotic component of the ecosystem are linked by flow on nutrients engineered by the biogeochemical cycles.
Biogeochemical cycles regulate the flow of substances. Since the biogeochemical cycles pass through different spheres, the flow of elements is regulated because each sphere has a particular medium and the rate at which elements flow is determined by the viscosity and density of the medium. Therefore elements in the biogeochemical cycles flow at differing rates with in the cycle and this regulates the flow of the elements in those cycles.