Download Biogeochemical cycles

UAU102F, University of Iceland
Fall
 In Earth science, a biogeochemical cycle is a pathway
by which a chemical substance moves through both
biotic (biosphere) and abiotic (lithosphere,
atmosphere, and hydrosphere) compartments of
Earth.
Introduction to
Environmental Science
Throstur Thorsteinsson
[email protected]
Fig 5.3
 Biogeochemcial (element) cycles
Carbon (C )
Oxygen (O)
Hydrogen (H)
Nitrogen (N)
Phosphorus (P)
Potassium (K)
Sulfur (S)
Calcium (Ca)
Sodium (Na)
Magnesium (Mg)
Manganese (Mn)
Molybdenum (Mo)
Cobalt (Co)
Zinc (Zn)
Aluminum (Al)
Copper (Cu)
Iron (Fe)
others
© 2005 John Wiley and Sons Publishers
Fig 5.5
 Macronutrients
 Elements required in large amounts by all life
 Include the “big six” elements that form the fundamental building
blocks of life:
carbon
oxygen
hydrogen phosphorus
nitrogen sulfur
 Micronutrients
 Elements required either in
 small amounts by all life or
 moderate amounts by some forms of life and not all by others
 Limiting factor
 When chemical elements are not available at the right times, in the
right amounts, and in the right concentrations relative to each other
© 2005 John Wiley and Sons Publishers
Throstur Thorsteinsson ([email protected])
1
UAU102F, University of Iceland
Fall
Fig 5.6
 The Geologic Cycle:
 The processes responsible for formation and change of
Earth materials
 Best described as a group of cycles:
 Tectonic
 Hydrologic
 Rock
 Biochemical
© 2005 John Wiley and Sons Publishers
Fig 5.7
 Tectonic cycle:
 Involves creation and destruction of the solid outer layer
of Earth, the lithosphere
 Plate tectonics:
 The slow movement of these large segments of Earth’s
outermost rock shell
 Boundaries between plates are geologically active areas
© 2005 John Wiley and Sons Publishers
 Divergent plate boundary:
 Occurs at a spreading ocean ridge, where plates are
moving away from one another
 New lithosphere is produced (seafloor spreading)
 Convergent plate boundary
 Occurs when plates collide
 Produces linear coastal mountain ranges or continental
mountain ranges
 Transform fault boundary
 Occurs where one plate slides past another
 San Andreas Fault in California
Throstur Thorsteinsson ([email protected])
2
UAU102F, University of Iceland
Fall
Fig 5.8
 The Hydrologic Cycle:
 The transfer of water from the oceans to the atmosphere
to the land and back to the oceans.
 Includes:
 Evaporation of water from the oceans
 Precipitation on land
 Evaporation from land
 Runoff from streams, rivers, and sub-surface groundwater
© 2005 John Wiley and Sons Publishers
Fig 5.9
 The rock cycle:
 Numerous processes that produce rocks and soils
 Depends on other cycles:
 tectonic cycle for energy
 Hydrologic cycle for water
 Rock is classified as
 Igneous
 Sedimentary
 Metamorphic
© 2005 John Wiley and Sons Publishers
 Carbon (C), the fourth most abundant element in the
Universe, after hydrogen (H), helium (He), and oxygen
(O), is the building block of life.
 On Earth, carbon cycles through the land, ocean,
atmosphere, and the Earth’s interior in a major
biogeochemical cycle
 Geological scale and the biological/physical scale.
 Gaseous form
 CH4, CO2
 Atmosphere
 Solid form
 CaCO3
 Shells
 Liquid form
 CO3, HCO3
 Ocean
Throstur Thorsteinsson ([email protected])
3
UAU102F, University of Iceland
Fall
 Carbon Emissions from
 Primary resource for
use of fossil fuels
increased since 1950 from
1.63 to 7.57 billion tons of
carbon
 CO2 Concentration 399
parts per million
(http://
/)
 Increased 20 percent
since 1959
photosynthesis
 Anthropogenic
emissions from:




Burning fossil fuels
Mining
Land conversion
Industrial processes
Do we have a problem?
2100
 Atmospheric
concentrations
expected to increase
drastically
 350 ppm considered
safe (2 degrees temp
increase)
 See 350.org
Throstur Thorsteinsson ([email protected])
 Average Global
Temperature in 2006
14.6°C, expected to
increase from 1.4° – 6°C in
100 years
 11 of the 12 years between
1995-2006 were amongst
the 12 warmest years on
record for global average
temperature
 Glaciers melting, profound
impact on ecosystems
4
UAU102F, University of Iceland
Photosynthesis:
energy
(sunlight)
+ 6CO2
+
Energy (sunlight)
 6 CO
2  H 2O
H2O=>
C6C6H12O6
H12O6  6 O2+ 6O2
Fall
 During winter in the northern hemisphere,
photosynthesis ceases when many plants lose their
leaves, but respiration continues.
 At spring, photosynthesis resumes and atmospheric
CO2 concentrations are reduced.
Respiration:
C6H12O6
(organic
matter) +
C6 H
12O6  6 O2
6O2 => 6CO2 + 6 H2O +
energy
6 CO2  6 H 2O  Energy
 Fossil fuels
 Deforestation
 Desertification
 Land-use
Throstur Thorsteinsson ([email protected])
5
UAU102F, University of Iceland
Fall
 The nitrogen cycle:
 Cycle responsible for moving important nitrogen
components through the biosphere and other Earth
systems
 Extremely important because nitrogen is required by all
living things; manufacture of protein and DNA
 Nitrogen fixation:
 The process of converting inorganic, molecular nitrogen
in the atmosphere to ammonia or nitrate, can now be
used.
 Denitrification:
 The process of releasing fixed nitrogen back to
molecular nitrogen that cannot be used
Since 1960
 Flows of biologically available
nitrogen in terrestrial
ecosystems doubled
 Flows of phosphorus tripled
> 50% of all the synthetic nitrogen
fertilizer ever used has been used since
1985
Human-produced Reactive Nitrogen
Humans produce as much biologically
available N as all natural pathways and this
may grow a further 65% by 2050
Fig 5.19
 The phosphorus cycle:
 Involves the movement of phosphorus throughout the
biosphere and lithosphere
 Important because phosphorus is an essential element
for life and often is a limiting nutrient for plant growth.
© 2005 John Wiley and Sons Publishers
Fig 5.20
© 2005 John Wiley and Sons Publishers
Throstur Thorsteinsson ([email protected])
6