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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 Sinks3. 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 out2. Algae, plants photosynthesize it3. 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
• NO3-• NO2-• NH4+• NH3
• N2
• Nitrogen • Ammonium
(ion)• Ammonia • Nitrate (ion)• Nitrite (ion)
• Nitrate (ion)• Nitrite (ion)• Ammonium
(ion)• Ammonia • Nitrogen
N Cycle Processes1. 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 Processes3. 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 Process5. 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 FUELPURPOSE: Energy purposes, driving cars
• Emits NO (nitric oxide) into atm.
• NO combines with H2O HNO3
– Nitric acid!
ACID RAIN
Fertilizers & ManurePURPOSE: 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 slowly2) Burning fuels interferes in these 2 cycles3) Runoff leads to overgrowth of aquatic
ecosystems in these 2 cycles4) Volcanoes are part of this cycle5) Guano is important in this cycle6) Very little of this cycle occurs in the air7) Bacteria is important to this cycle8)What 2 cycles contribute to acid rain?9) Weathering is the main action in this cycle
• P• N, S• P, N
• S• P• P• N• S, N• P
Human activities have changed the composition of the atmosphere since the pre- industrial era