BIOGEOCHEMICAL CYCLES 4.4. WATER (Hydrologic) CYCLE It is a “redistribution” of water. A drought somewhere = more water somewhere else.

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