UAU102F, University of Iceland Fall
Throstur Thorsteinsson ([email protected]) 1
Introduction toEnvironmental Science
Throstur Thorsteinsson
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.
Fig 5.3
© 2005 John Wiley and Sons Publishers
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
Fig 5.5
© 2005 John Wiley and Sons Publishers
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 phosphorusnitrogen 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
UAU102F, University of Iceland Fall
Throstur Thorsteinsson ([email protected]) 2
The Geologic Cycle: The processes responsible for formation and change of
Earth materials
Best described as a group of cycles: Tectonic
Hydrologic
Rock
Biochemical
Fig 5.6
© 2005 John Wiley and Sons Publishers
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
Fig 5.7
© 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
UAU102F, University of Iceland Fall
Throstur Thorsteinsson ([email protected]) 3
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
Fig 5.8
© 2005 John Wiley and Sons Publishers
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
Fig 5.9
© 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
UAU102F, University of Iceland Fall
Throstur Thorsteinsson ([email protected]) 4
Primary resource for photosynthesis
Anthropogenic emissions from: Burning fossil fuels Mining Land conversion Industrial processes
Carbon Emissions from 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
Do we have a problem?
Atmospheric concentrations expected to increase drastically
350 ppm considered safe (2 degrees temp increase)
See 350.org
2100
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
UAU102F, University of Iceland Fall
Throstur Thorsteinsson ([email protected]) 5
Photosynthesis:
energy (sunlight) + 6CO2 + H2O => C6H12O6 + 6O2
Respiration:
C6H12O6 (organic matter) + 6O2 => 6CO2 + 6 H2O + energy
26126
22
6
6(sunlight)Energy
OOHC
OHCO
Energy66
6
22
26126
OHCO
OOHC
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.
Fossil fuels
Deforestation
Desertification
Land-use
UAU102F, University of Iceland Fall
Throstur Thorsteinsson ([email protected]) 6
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
© 2005 John Wiley and Sons Publishers
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.
Fig 5.20
© 2005 John Wiley and Sons Publishers
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