Transcript 4.4 - Mrs. Loch

BIOGEOCHEMICAL CYCLES
4.4
WATER (Hydrologic) CYCLE
• It is a “redistribution” of water. A drought
somewhere = more water somewhere else
The Carbon Cycle
SOME QUESTIONS….
1. How is Carbon present in us?
– Carbohydrates, fats, proteins, DNA/RNA, etc.
2. How is CO2 removed from atmosphere and water?
– Producers use photosynthesis
– 6CO2 + 6H2O  6O2 + C6H12O6
Sources and Sinks
3. How is carbon put back into the
atmosphere/water?
• Aerobic respiration
4. How are coal & oil formed?
• Buried organic matter is compressed = more
bonds = more energy
5. How is this carbon cycled back to CO2?
• Burned (+ oxygen)
What happens to CO2 in the ocean?
1. CO2 stays dissolved in water
& can “fizz” back out
2. Algae, plants photosynthesize it
3. Carbonate & bicarbonate ions form
4. These Carbon forms can react with Calcium
– Forms CaCO3 shells/skeletons
– Ultimately these form limestone over millions of
years.
What’s an experiment you could
design to replicate the carbon cycle
PHOTOSYNTHESIS  RESPIRATION
How do humans disrupt the C cycle?
1. Removal of vegetation
– Can’t absorb through photosynthesis
2. Burning fossil fuels/wood
– Produces excess CO2
What is the greenhouse effect?
Is this a problem?
NITROGEN CYCLE
Facts
• Nitrogen makes up 78% of atmosphere
– N= N (N2)
– This form is NOT usable by plants & animals
– This problem must be FIXED!
• Bacteria play a major role in the N cycle
– Make it available for plants, which animals then
eat
– Everything dies & bacteria change the N back to
the original form in the air
Match the Nitrogen Forms
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•
•
•
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NO3NO2NH4+
NH3
N2
• Nitrate (ion)
• Nitrite (ion)
• Ammonium
(ion)
• Ammonia
• Nitrogen
• Nitrogen
• Ammonium
(ion)
• Ammonia
• Nitrate (ion)
• Nitrite (ion)
N Cycle Processes
1. Nitrogen Fixation  turns stable nitrogen into
a usable form
– cyanobacteria or Rhizobium bacteria
– lightning
2. Ammonification first step in another
process to convert nitrogen gas into plant
friendly form
– done by bacteria or fungi
Nodules: Rhizobium bacteria live in
N cycle Processes
3. Nitrification  two step process in continuing
conversion
– NH4 to NO3- (aerobic bacteria)
– Has an intermediate NO2- step (toxic to plant)
4. Assimilation  plants use N to make
important biological molecules
– Plants do this for themselves
– Animals eat these plants to get their N
N cycle Process
5. Decomposition  starts the other half of the
cycle; dead things put their N back
– Decomposing bacteria do this
6. Denitrification  final step that returns the
cycle to the starting point
– back to N2 or N2O
– Anaerobic bacteria do this
– Return this into the atmosphere
• Start all over again!
NITROGEN CYCLE
Nitrogen Cycle
5 HUMAN CONTRIBUTIONS
Burning Fuel (+)
Fertilizers/manure bacteria (+)
Mining minerals, take out plants/water too
much (-)
Burn grasslands/clear forests (-/+)
Sewage and farming runoff (+)
BURNING FUEL
PURPOSE: Energy purposes, driving cars
• Emits NO (nitric oxide) into atm.
• NO combines with H2O  HNO3
– Nitric acid!
ACID RAIN
Fertilizers & Manure
PURPOSE: Helps plants grow (plants like N)
• Farm animals have bacteria in their guts
– They add this to the ground in their poop
– Remember  these bacteria denitrify
• Also, we add fertilizers which gives more
starting material to the denitrification process
• N2O (Nitrous oxide) is a greenhouse gas
because it doesn’t react with anything else
– It just stays there
Mining & Farming
• Take out minerals (NH4NO3)
– PURPOSE: to produce commercial fertilizers
• Remove fixed N from topsoil
– PURPOSE: we harvest plants to eat
– Interferes with assimilation/decomposition
Burn Grasslands/Clear Forests
• PURPOSE: create open farmland
• Removes Plants  interferes with
assimilation/ammonification
• Burning adds NO to atmosphere
– Same as burning fuel  leads to HNO3
Sewage & Farming Runoff
• Animal waste has a variety of N-containing “stuff”
• Water from farms removes the N from fertilizers
• Plants love N! This runoff goes into lakes,
streams, etc. and increases algae/plants there
– Plants die (food supply for decomposers)
• Decomposers increase
– respire too much, use up too much O2
 causes trouble!
Eutrophication
PHOSPHORUS CYCLE
Where is the most P found?
Where is the least P found?
What is important to its cycle?
Phosphorus Cycle
Where P is found…
• Earth’s crust
water,
organisms
• Most = phosphate salts (PO4 3-)
in ocean sediments
• Soil doesn’t have a lot
(therefore limiting factor)
• Very little in air (P is not a gas)
How is it cycled?
• VERY SLOWLY
– So slow, it appears one way (land to ocean)
– Hundreds of millions of years
• WEATHERING  the slow breakdown of rock
– Dissolves in water, taken up by plant roots
• Cycles through living things
– Animals eat plant (or herbivores)
Cycle returns
• Cycle returns through waste & decay
– Guano  phosphate-rich manure typically of fish
eating birds
• Severe erosion of rock
• Geologic processes  push up and expose
sea floor which slowly weathers
Human Interference
• Mining (+)
– To make fertilizer & detergents
– Leaves huge pits/ponds that weather & pollute
water
• Cut tropical rain forests (-)
– Very little P in soil; removal of plants prevents
decay and cycling back
• Runoff (+)
– Animal wastes, sewage, fertilizer: excess P in
water
Remember why runoff is bad…
• Too much nutrient leads to LOTS of plant
growth
– Cyanobacteria, algae, plants
• Eventually overgrow/block out sun
• Ultimately die  increase decomposers 
use up O2  kill fish and other “respirators”
Phosphate Cycle
SULFUR CYCLE
Where is it found?
• Most = underground in rocks & minerals
– Buried deep under ocean sediments
• Atmosphere
– Gases & sea spray particles
How is it cycled?
• Volcanic eruptions
– Colorless, poisonous gases (SO2, H2S)
• Anaerobic bacteria in bogs, swamps
– Colorless, poisonous gas (H2S)
• Sea spray particles (SO4 2-)
• Plankton emit DMS (dimethylsulfide)
• In atmosphere…
– Sulfur trioxide gas yields sulfuric acid
Human Intervention
• 99% of SO2 (1/3 of all S) is from humans
• Burn sulfur-containing coal, oil for power
– 2/3 human sulfur input
• Refine petroleum
• Smelt minerals into desired metals (Cu, Pb, Zn)
• Other industrial processes
N, P or S?
1) This cycle occurs VERY slowly
2) Burning fuels interferes in these 2 cycles
3) Runoff leads to overgrowth of aquatic
ecosystems in these 2 cycles
4) Volcanoes are part of this cycle
5) Guano is important in this cycle
6) Very little of this cycle occurs in the air
7) Bacteria is important to this cycle
8)What 2 cycles contribute to acid rain?
9) Weathering is the main action in this cycle
• P
• N, S
• P, N
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•
•
•
•
•
S
P
P
N
S, N
P
Human activities have changed the composition of the
atmosphere since the pre- industrial era