A biogeochemical cycle is one of several natural cycles, in which conserved matter moves through the biotic and abiotic parts of an ecosystem. In geography and Earth science, a biogeochemical cycle or substance turnover or cycling of substances is a pathway by which a chemical substance moves through biotic (biosphere) and abiotic (lithosphere, atmosphere, and hydrosphere) compartments of Earth. The following presentation discusses the role of humans in the biogeochemical cycles.

1. Biogeochemical Cycles and
Human Activities
WATENTENA AMOS
MAY, 2018

2. Objectives
o Identify and describe the flow of
nutrients in each biogeochemical cycle.
o Explain the impact that humans have on
the biogeochemical cycles.

3. Food for thought:
o What happens to energy in an
ecosystem?
o What happens to matter in an
ecosystem?

4. Solar Energy Sustains Life on Earth

5. Survival Secrets
o Two Secrets of Survival: Energy Flow
and Matter Recycle
o An ecosystem therefore survives by a
combination of energy flow and matter
recycling.

6. Energy Flow and Matter Recycle

7. MATTER CYCLING IN ECOSYSTEMS
oNutrients are the elements and
compounds that organisms need to
live, grow, and reproduce.
oBiogeochemical cycles move these
substances through air, water, soil,
rock and living organisms.

8. Unique Properties of Water
o There are strong forces of attraction
between molecules of water.
o Water exists as a liquid over a wide
temperature range.
o Liquid water changes temperature slowly.
o It takes a large amount of energy for
water to evaporate.
o Liquid water can dissolve a variety of
compounds.
o Water expands when it freezes.

9. The Water Cycle
PrecipitationPrecipitation
Transpiration
Condensation
Evaporation
Ocean storage
Transpiration
from plants
Precipitation
to land
Groundwater movement (slow)
Evaporation
from land Evaporation
from ocean Precipitation
to ocean
Infiltration and
Percolation
Rain clouds
Runoff
Surface runoff
(rapid)
Surface
runoff
(rapid)

10. Effects of Human Activities
Humans alter the water cycle through:
oWithdrawing large amounts of
freshwater.
oClearing vegetation and eroding
soils.
oPolluting surface and underground
water.
oContributing to climate change.

11. The Carbon Cycle

12. Globe Carbon Cycle

13. The Carbon Foot Print

14. Effects of Humans on the Carbon Cycle
Humans alter the carbon cycle by adding
excess CO2 to the atmosphere through:
oBurning fossil fuels.
oClearing vegetation faster than it is
replaced.

15. The Nitrogen Cycle

16. Modified Nitrogen Cycle

17. Effects of Human Activities
oAdding gases that contribute to
acid rain.
oContaminating ground water from
nitrate ions in inorganic
fertilizers.
oReleasing nitrogen into the
troposphere through
deforestation.

18. Effects of Human Activities
o Human activities such as production of
fertilizers now fix more nitrogen than
all natural sources combined.
o Adding nitrous oxide to the atmosphere
through farming practices which can
warm the atmosphere and deplete
ozone.

19. The Nitrogen Foot Print

20. The Phosphorous Cycle
Dissolved
in Ocean
Water
Marine Sediments Rocksuplifting over
geologic time
settling out
weathering
sedimentation
Land
Food
Webs
Dissolved
in Soil
Water,
Lakes,
Rivers death,
decomposition
uptake by
autotrophs
agriculture
leaching, runoff
uptake by
autotrophs
excretion
death,
decomposition
mining
Fertilizer
weathering
Guano
Marine
Food
Webs

21. Effects of Human Activities
o We remove large amounts of
phosphate from the earth to make
fertilizer.
o We reduce phosphorous in tropical
soils by clearing forests.
o We add excess phosphates to
aquatic systems from runoff of
animal wastes and fertilizers.

22. The Sulphur Cycle
Hydrogen sulfide
Sulfur
Sulfate salts
Decaying matter
Animals
Plants
Ocean
Industries
Volcano
Hydrogen sulfide
Oxygen
Dimethyl
sulfide
Ammonium
sulfate
Ammonia
Acidic fog and
precipitation
Sulfuric
acid
WaterSulfur
trioxide
Sulfur dioxide
Metallic
sulfide
deposit
s

23. Effects of Human Activities
Humans add sulfur dioxide to the
atmosphere by:
o Burning coal and oil
o Refining sulfur containing petroleum.
o Convert sulfur-containing metallic ores
into free metals such as copper, lead,
and zinc releasing sulfur dioxide into the
environment.

24. Is the Earth Alive?
Some have proposed that the earth’s
various forms of life control or at
least influence its chemical cycles and
other earth-sustaining processes.
oThe strong Gaia hypothesis: life
controls the earth’s life-sustaining
processes.
oThe weak Gaia hypothesis: life
influences the earth’s life-
sustaining processes.

25. Thank You