uau102f, university of iceland fallthorstur/teaching/uau102/w02_1_basics_geocycles.pdf · uau102f,...

UAU102F, University of Iceland Fall

Throstur Thorsteinsson ([email protected]) 1

Introduction toEnvironmental Science

Throstur Thorsteinsson

[email protected]

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


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



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


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


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



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


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


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



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

http://co2now.org/



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



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.

Fig 5.20


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