Download Unit 2 Biogeo

Biogeochemical Cycles
The cycling of matter (i.e. N, P, S, C, & H2O) through Earth’s systems (biological, geological, and chemical
interactions).
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The main source of energy that drives all cycles is the sun.
The hydrologic cycle helps all of the other nutrients cycle (powered by the sun)
Good example of the Law of Conservation of Matter.
Matter flows in one direction – it is not recycled but does cycle through a system
Cycles from biotic matter (living organisms) to abiotic matter (nutrients in the environment)
Macronutrient cycles include N, P, S, C, and H2O.
Nitrogen Cycle –
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Mostly an atmospheric cycle (78% of atmosphere is N 2 gas)
Cannot be used by animals in its gaseous state.
Necessary for life: proteins, nucleic acids…
Often a limiting factor in plant growth because NH3, NH4+, & NO3- are water soluble & leach out of soil
Human interference in N-Cycle:
 Fertilizer & animal runoff from feedlots (places where livestock is raised as a food source) – run off into waterways
causes eutrophication
 Vehicle exhaust – small amounts of NOx found in fossil fuels (this is
the most dangerous greenhouse gas (per molecule).)
The N-cycle:
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N2 in the air undergoes nitrogen fixation in the soil by
nitrogen fixing bacteria (found in legumes).
N2 is converted to NH4+ through Ammonification.
NH4 + is converted to NO2- & NO3- through Nitrification
One of two things can now happen……
NO3- is useful to plants & can be absorbed by plant roots
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(fertilizer) through Assimilation
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As plants decompose (by aerobic or anaerobic bacteria),
to becomes NH4+ again (Ammonification) & the cycle
repeats.
OR
NO3- gets fixed by denitrifying bacteria (Denitrification) and returns to the air as N2 (cycle repeats)
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Phosphorus Cycle –
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Sedimentary cycle – never exists as a gas
Main storehouse is in rocks
Required for nucleic acids, ATP, phospholipids in cell
membranes, bones, teeth, shells
Human interferences in P-Cycle:
 Fertilizer & animal runoff (same as above)
 Detergents high in P; runoff into waterways.
The P-Cycle:
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PO4-3 (on land or in the ocean) released by
weathering & taken up by plants or runs off into
other water ways.
Animals get PO4-3 by eating plants & other animals
decomposition changes organic molecules w/ P back into PO 4-3 which dissolves in water & returns to
sediment
Sulfur Cycle –
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Atmospheric and geologic cycle
Main storehouse: in the ground
Natural sources: hydrogen sulfide (in swamps),
volcanic gas
Human Interference:
 By-product of burning fossil fuels.
 67% of S in atmosphere comes from coal burning
power plants.
The S-Cycle:
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H2S + O2 (atm)  SO2
SO2 + O2 SO3
SO3 + H2O  H2SO4 (acid deposition,
S returned to soil & water, taken up by plants & animals)
Carbon Cycle –
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mostly atmospheric cycle, also geologic
required for the formation of living things
Largest reserves (“carbon sinks”): sedimentary rocks
(limestone) & oceans (dissolved CO2 & living things in
ocean)
Human Interferences:
 Fossil fuels removed faster than they can be
replenished
 CO2 & CO are being produced more than vegetation can
consume it.
 Excess CO2 adds to greenhouse effect
 Removal of forests “produces” CO2 by not absorbing it.
The C-Cycle:
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CO2 is absorbed by plants (photosynthesis) &
converted to glucose.
Moves through the food chain.
Animals breathe out CO2 into the atmosphere (respiration)
Animal / Plant waste / remains return C to the ground. Over time becomes fossil fuels
We remove fossil fuels. Combustion leads to CO2 & CO. (also occurs when burning biomass)
Absorbs into the ground (on land & in oceans) and becomes rock (limestone – CaCO3)
Hydrologic (water) Cycle –
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Mostly atmospheric
Main storehouse: Oceans, groundwater, surface water
Necessary for life on earth – weather, movement of other nutrients, cell / organs, etc.
Human Interference:
 As the Earth gets hotter, more water stays in the evaporative form
instead of on Earth where we use it.
 Water that is contaminated may not get cleaned
 fast enough for human consumption
The H2O Cycle:
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Evaporation (l g) from surface water;
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Transpiration evaporation from plants.
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Condensation (g  l) into clouds
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Precipitation falls back to earth
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Infiltration absorbs into the ground or
runs off into local waterways