Abraham G. Dayklee

• As we have already seen that while
energy does not cycle through an
ecosystem, chemicals do.
• The inorganic nutrients cycle
through more than the organisms,
however, they also enter into the
atmosphere, the oceans, and even
rocks.
• Since these Chemicals cycle through
both the Biological and the
Geological world, we call the overall
cycles BIOGEOCHEMICAL
CYCLES.
• Each chemical has its own unique
cycle, but all of the cycles do have
some things in common.

They are:
• Reservoirs - are those parts of the
cycle where the chemical is held in
large quantities for long periods of
time.
• Exchange pools, on the other hand,
where the chemical is held for only
a short time.
• Residence time - The length of
time a chemical is held in an
exchange pool or a reservoir
• For example: The Oceans are a
Reservoir for water, while a
Cloud is an Exchange pool.

• Water may reside in an ocean for
thousands of years, but in a cloud for a
few days at best.
• While all inorganic nutrients cycle,
we will focus on only 4 of the most
important cycles
• They include:
1.

• It is also called Hydrological cycle
or the hydrologic cycle; it describes
the continuous movement of water
on, above and below the surface of
the Earth.
• The water moves from one reservoir
to another, such as from river to
ocean, or from the ocean to the
atmosphere, by physical processes:
• Namely: Evaporation, Condensation,
Precipitation, Infiltration, Surface
runoff, and Subsurface flow.
• In doing so, the water goes through
different forms: liquid, solid (ice)
and vapor.
• The water cycle involves the
exchange of energy, which leads to
temperature changes.

• In the Water cycle, energy is
supplied by the SUN, which drives
evaporation whether it be from
ocean surfaces or from treetops.
• The Sun also provides the energy
which drives the weather systems
which move the water vapor
(clouds) from one place to another
(otherwise, it would only rain over
the oceans).
• Precipitation occurs when water
condenses from a gaseous state in the
atmosphere and falls to earth.
• Evaporation is the reverse process in
which liquid water becomes gaseous.
 When water evaporates, it takes up
energy from its surroundings and
cools the environment.

• When it condenses, it releases
energy and warms the environment.
Once water condenses, gravity
takes over and the water is pulled
to the ground.
• Gravity continues to operate,
either pulling the water
underground (groundwater) or
across the surface (runoff).
• In either event, gravity continues
to pull water lower and lower until
it reaches the oceans (in most
cases; the Great Salt Lake, Dead
Sea, Caspian Sea, and other such
depressions may also serve as the
lowest basin into which water can
be drawn).

• The oceans are salty because any
weathering of minerals that occurs as
the water runs to the ocean will add
to the mineral content of the water.
• However, water cannot leave the
oceans except by evaporation, and
evaporation leaves the minerals
behind.
• Organisms play an important role
in the water cycle, having
significant amount of water (up
to 90% of their body weight).
• Animals and plants lose water
through evaporation from the
body surfaces, and through
evaporation from the gas
exchange structures (such as
lungs).

1. Water withdrawal from streams, lakes
and groundwater (salt water intrusion
and groundwater depletion)
2. Clear vegetation from land for
agriculture, mining, road and building
construction. (nonpoint source runoff
carrying pollutants and reduced
recharge of groundwater)
3. Degrade water quality by adding
nutrients(NO2, NO3, PO4) and
destroying wetlands (natural
filters).
4. Degrade water clarity by clearing
vegetation and increasing soil
erosion.

• It is the biogeochemical cycle by
which carbon is exchanged among the
biosphere, pedosphere, geosphere,
hydrosphere, and atmosphere of the
Earth.
• Carbon is the main component of
biological compounds as well as a
major component of many minerals
such as limestone.
• It describes the movement of
carbon as it is recycled and reused
throughout the biosphere, as well as
long-term processes of carbon
sequestration to and release from
carbon sinks.
• The carbon cycle was initially
discovered by Joseph Priestley and
Antoine Lavoisier, and popularized
by Humphry Davy

NATURAL SOURCES OF
CARBON:
1. Death of plants and animals
2. Animal waste
3. Atmospheric CO2
4. Weathering
5. Methane gas from cows (and
other ruminants)
6. Aerobic respiration from
terrestrial and aquatic life
SOURCES OF CARBON FROM
HUMAN ACTIVITY:
1. Burning wood or forests
2. Cars, trucks, planes
3. Burning fossil fuels such as coal,
oil and natural gas to produce heat
and energy.

The biogeochemical cycle of oxygen
within its four main reservoirs:
1. The Atmosphere (air), the total
content of biological matter within
2. The Biosphere (the global sum of
all ecosystems)
3. The Hydrosphere (the combined
mass of water found on, under, and
over the surface of planet Earth)
4. The Lithosphere/Earth's crust
• The main driving factor of the oxygen
cycle is photosynthesis, which is
responsible for the modern Earth's
atmosphere and life on Earth in its
current form
• The largest reservoir of Earth's oxygen is
within the silicate and oxide minerals
of the crust and mantle (99.5% by
weight).

• The Earth's atmosphere, hydrosphere and
biosphere together weigh less than 0.05%
of the Earth's total mass.
Atmosphere is 20.9% oxygen by
volume present mainly as free
oxygen molecules (O2) with other
oxygen-containing molecules
including ozone (O3), carbon
dioxide (CO2), water vapor (H2O),
and sulfur and nitrogen oxides
(SO2, NO, N2O, etc.)
• Biosphere is 22% oxygen by volume
present mainly as a component of
organic molecules (CxHxNxOx) and
water molecules
• Hydrosphere is 33% oxygen by vol.
present mainly as a component of water
molecules with dissolved molecules
including free oxygen and carbonic
acids (HxCO3)

 Lithosphere
is 94% oxygen
by volume
present mainly
as silica
minerals (SiO2)
and other oxide
minerals

• The nitrogen cycle is the
biogeochemical cycle by which
nitrogen is converted into
multiple chemical forms as it
circulates among the
atmosphere, terrestrial, and
marine ecosystems.
• Important processes in the
nitrogen cycle include fixation,
ammonification, nitrification,
and denitrification
• The majority of Earth's atmosphere
(80%) is nitrogen, making it the
largest source of nitrogen.
• The nitrogen cycle is of particular
interest to ecologists because
nitrogen availability can affect the
rate of key ecosystem processes,
including primary production and
decomposition.

• SOURCES OF NITROGEN:
1. Lightning
2. Inorganic fertilizers
3. Nitrogen Fixation
4. Animal Residues
5. Crop residues
6. Organic fertilizers
• FORMS OF NITROGEN:
1. Urea  CO(NH2)2
2. Ammonia  NH3 (gaseous)
3. Ammonium  NH4
4. Nitrate  NO3
5. Nitrite  NO2
6. Atmospheric Dinitrogen N2
7. Organic N

• Human activities such as fossil fuel
combustion, use of artificial
nitrogen fertilizers, and release of
nitrogen in wastewater have
dramatically altered the global
nitrogen cycle.
• Nitrogen is present in the environment
in a wide variety of chemical forms
including:
1. Organic nitrogen, ammonium (NH+
4)
2. Nitrite (NO−
2),
3. Nitrate (NO−
3),
4. Nitrous oxide (N2O),
5. Nitric oxide (NO)
6. Inorganic nitrogen gas (N2).

• ROLES OF NITROGEN:
1. Plants and bacteria use nitrogen
in the form of NH4
+ or NO3
-
2. It serves as an electron acceptor
in anaerobic environment
3. Nitrogen is often the most
limiting nutrient in soil and water.
It’s a key component for:
• Amino acids
• Nucleic acids (purine, pyrimidine)
• Cell wall components of bacteria
(NAM).

• The phosphorus cycle is the
biogeochemical cycle that describes
the movement of phosphorus through
the lithosphere, hydrosphere, and
biosphere
• On the land, phosphorus gradually
becomes less available to plants over
thousands of years, because it is
slowly lost in runoff
• Unlike other cycles, the atmosphere
does not play a significant role in
the movement of phosphorus,
because phosphorus and
phosphorus-based compounds are
usually solids at the typical ranges
of temperature and pressure found
on Earth.

• Phosphorous is held in the tissue of
the trees and vegetation, not in the soil
and as we deforest the land, we remove
the ability for phosphorous to replenish
globally in ecosystems
• Cultural Eutrophication – add excess
phosphate to aquatic ecosystems in
runoff of animal wastes from livestock
feedlots, runoff of commercial
phosphate fertilizers fro cropland, and
discharge of municipal sewage.
• Humans mine LARGE
quantities of phosphate rock to
use in commercial fertilizers
and detergents.
• Phosphorous is NOT found as a
gas, only as a solid in the
earth’s crust. It takes millions
to hundreds of millions of years
to replenish.

1. Phosphorous is an essential nutrient
of both plants and animals.
2. It is part of DNA molecules which
carry genetic information.
3. It is part of ATP and ADP) that store
chemical energy for use by
organisms in cellular respiration.
4. Forms phospholipids in cell
membranes of plants and animal
cells.
5. Forms bones, teeth, and shells of
animals as calcium phosphate
compounds.

• Sulfur is one of the macronutrients
required by plants and is obtained by
them from the soil and from the
atmosphere.
• It is present in proteins and gives a
distinctive odor to many substances.
• It is also a component of the amino
acid cysteine and is present in a large
number of enzyme systems.
• Several groups of prokaryotes
utilize and release sulfur.
• The major reservoirs for sulfur in
the global cycle are pyrite and
gypsum (an evaporite of
seawater) in the lithosphere and
in seawater

Approximately 1/3 of all sulfur emitted
into atmosphere comes from human
activities.
1. Burning sulfur containing coal and
oil to produce electric power (SOx =
acid deposition).
2. Refining petroleum – (SOx
emissions)
3. Smelting to convert sulfur
compounds of metallic minerals
into free metals (Cu, Pb, Zn)
4. Industrial processing.

1. Sulfur is a component of most
proteins and some vitamins.
1. Sulfate ions (SO4
2- ) dissolved in
water are common in plant tissue.
They are part of sulfur-containing
amino acids that are the building
blocks for proteins.
3. Sulfur bonds give the three
dimensional structure of amino
acids.
4. Many animals, including
humans, depend on plants for
sulfur-containing amino acids.

• References: