Biogeochemical Cycles

EQ: Identify and describe the flow of nutrients in each biogeochemical cycle.

Explain the impact that humans have on the biogeochemical cycles.

What does biogeochemical mean?

• Bio

• Geo

• Chemical

BIOGEOCHEMICAL CYCLES

‘Fundamentals’ of biogeochemical cycles

• All matter cycles...it is neither created nor destroyed...

• As the Earth is essentially a closed system with respect to matter, we can say that all matter on Earth cycles .

• Biogeochemical cycles: the movement (or cycling) of matter through a system

Matter = elements (carbon, nitrogen, oxygen) or molecules (water)

so the movement of matter (for example carbon) between these parts of the system is, practically speaking, a biogeochemical cycle

The Cycling Elements:

macronutrients : required in relatively large amounts

carbon , hydrogen , oxygen , nitrogen , phosphorous sulfur

other macronutrients:

potassium , calcium , iron , magnesium

micronutrients : required in very small amounts, (but still necessary)

boron (green plants) copper (some enzymes) molybdenum (nitrogen-fixing bacteria)

ATMOSPHERE

LITHOSPHERE

HYDROSPHERE

ECOSPHERE

6 of the most important cycles are the water, carbon, nitrogen, sulfur, phosphorus and oxygen.

1. Water

2. Carbon

3. Nitrogen

4. Phosphorous

5. Sulfur

6. Oxygen

I. The Water Cycle

• Evaporation -Water changes from liquid to gas

• Transpiration -Water evaporates from the leaves into the atmosphere.

• Condensation - Water vapor (gas) turns into liquid water forming clouds.

• Precipitation-Water droplets become large enough to fall to Earth-Rain, snow, sleet, or hail

• Surface Runoff - Rain, snow, that flows into streams, rivers, or canals.

HYDROLOGIC CYCLE

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Figure 4-28Page 76

Precipitation toland

Transpirationfrom plants

Runoff Surface runoff(rapid)

Evaporationfrom land Evaporation

from ocean Precipitation toocean

Ocean storage

Surfacerunoff(rapid)

Groundwater movement (slow)

Rain cloudsCondensation

Transpiration

Evaporation

PrecipitationPrecipitation

Infiltration andPercolation

Effects of Human Activities on Water Cycle

• We alter the water cycle by:– Withdrawing large amounts of freshwater.– Clearing vegetation and eroding soils.– Polluting surface and underground water.– Contributing to climate change.

Water Quality Degradation

II. The Carbon Cycle

Where does carbon come from?

Natural Sources

of

Carbon

Sources of Carbon from Human Activity

•Death of plants and animals•Animal waste•Atmospheric CO2•Weathering•Methane gas from cows (and other ruminants)•Aerobic respiration from terrestrial and aquatic life

•Burning wood or forests•Cars, trucks, planes•Burning fossil fuels such as coal, oil and natural gas to produce heat and energy.

Carbon in Oceans• Additional carbon is stored in the ocean.

• Many animals pull carbon from water to use in shells, etc.

• Animals die and carbon substances are deposited at the bottom of the ocean.

• Oceans contain earth’s largest store of carbon.

Fig. 3-27, pp. 72-73

MARINE CARBON CYCLE

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Diffusion between atmosphere and ocean

Carbon dioxidedissolved in ocean water

Marine food websProducers, consumers,

decomposers, detritivores

Marine sediments, includingformations with fossil fuels

Combustion of fossil fuels

incorporation into sediments

death, sedimentation

uplifting over geologic time

sedimentation

photosynthesis aerobic respiration

Figure 4-29aPage 78

TERRESTRIAL CARBON CYCLE

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photosynthesis aerobic respirationTerrestrial

rocks

Soil water(dissolved

carbon)

Land food websproducers, consumers,

decomposers, detritivores

Atmosphere(most carbon is in carbon dioxide)

Peat,fossil fuels

combustion of wood (for clearing land; or for fuel

sedimentation

volcanic action

death, burial, compaction over geologic timeleaching

runoff

weathering

Figure 4-29b Page 79

Combustion of fossil

fuels

Effects of Human Activities on Carbon Cycle

We alter the carbon cycle by adding excess CO2 to the atmosphere through:Burning fossil fuels.Clearing vegetation

faster than it is replaced.

Figure 3-28Figure 3-28

III. The Nitrogen Cycle

• Where does nitrogen come from?

Sources of Nitrogen

•Inorganic fertilizers•Nitrogen Fixation•Animal Residues•Crop residues•Organic fertilizers

Forms of Nitrogen

• Urea CO(NH2)2

• Ammonia NH3 (gaseous)• Ammonium NH4

• Nitrate NO3

• Nitrite NO2

• Atmospheric Dinitrogen N2

• Organic N

Roles of Nitrogen

• Plants and bacteria use nitrogen in the form of NH4

+ or NO3-

• It serves as an electron acceptor in anaerobic environment

• Nitrogen is often the most limiting nutrient in soil and water.

Nitrogen is a key element for

• amino acids• nucleic acids (purine, pyrimidine) • cell wall components of bacteria

(NAM).

Effects of Human Activities on the Nitrogen Cycle

• We alter the nitrogen cycle by:– Adding gases that contribute to acid rain.– Adding nitrous oxide to the atmosphere through

farming practices which can warm the atmosphere and deplete ozone.

– Contaminating ground water from nitrate ions in inorganic fertilizers.

– Releasing nitrogen into the troposphere through deforestation.

Effects of Human Activities on the Nitrogen Cycle

• Human activities such as production of fertilizers now fix more nitrogen than all natural sources combined.

Figure 3-30Figure 3-30

IV. The Phosphorous Cycle

IMPORTANCE OF PHOSPHOROUS CYCLE

• 1.Phosphorous is an essential nutrient of both plants and animals.

• 2. It is part of DNA molecules which carry genetic information.

• 3. It is part of ATP and ADP) that store chemical energy for use by organisms in cellular respiration.

• 4. Forms phospholipids in cell membranes of plants and animal cells.

• 5. Forms bones, teeth, and shells of animals as calcium phosphate compounds.

PHOSPHOROUS CYCLE

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GUANO

FERTILIZER

ROCKS

LAND FOOD WEBS

DISSOLVED IN OCEAN

WATER

MARINE FOOD WEBS

MARINE SEDIMENTS

weathering

agriculture

uptake by autotrophs

death, decomposition

sedimentation settling out weathering

leaching, runoff DISSOLVED IN SOIL WATER,

LAKES, RIVERS

uptake by autotrophs

death, decomposition

miningmining

excretionexcretion

Figure 4-33Page 82

uplifting over geologic time

HUMAN IMPACTS TO PHOSPHOROUS CYCLE

1. Humans mine LARGE quantities of phosphate rock to use in commercial fertilizers and detergents. Phosphorous is NOT found as a gas, only as a solid in the earth’s crust. It takes millions to hundreds of millions of years to replenish.

2. Phosphorous is held in the tissue of the trees and vegetation, not in the soil and as we deforest the land, we remove the ability for phosphorous to replenish globally in ecosystems.

3. Cultural eutrophication – ad excess phosphate to aquatic ecosystems in runoff of animal wastes from livestock feedlots, runoff of commercial phosphate fertilizers fro cropland, and discharge of municipal sewage.

Effects of Human Activities on the Phosphorous Cycle

• We remove large amounts of phosphate from the earth to make fertilizer.

• We reduce phosphorous in tropical soils by clearing forests.

• We add excess phosphates to aquatic systems from runoff of animal wastes and fertilizers.

V. The Sulfur Cycle

IMPORTANCE OF SULFUR CYCLE

1. Sulfur is a component of most proteins and some vitamins.

2. Sulfate ions (SO4 2- ) dissolved in water are common in plant tissue. They are part of sulfur-containing amino acids that are the building blocks for proteins.

3. Sulfur bonds give the three dimensional structure of amino acids.

4. Many animals, including humans, depend on plants for sulfur-containing amino acids.

SULFUR CYCLE

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Figure 4-34Page 83

Sulfur

Hydrogen sulfide

Sulfate salts

Plants

Acidic fog and precipitation

Ammonium sulfate

Animals

Decaying matterMetallic

sulfide deposits

Ocean

Dimethyl sulfide

Sulfur dioxide Hydrogen sulfide

Sulfur trioxide Sulfuric acidWater

Ammonia

Oxygen

Volcano

Industries

Effects of Human Activities on the Sulfur Cycle

• We add sulfur dioxide to the atmosphere by:– Burning coal and oil– Refining sulfur containing petroleum.– Convert sulfur-containing metallic ores into free

metals such as copper, lead, and zinc releasing sulfur dioxide into the environment.

VI. The Oxygen Cycle

The Oxygen cycle

PHOTOSYNTHESIS

Photosynthesis: occurs within the chloroplasts of green plants. The photosynthetic membranes are arranged in flattened sacs called the thylakoids.

6CO2 + 12H2O C6H12O6 + 6O2 + 6H2O light

(reactants) (products)

Function: Chemical energy

Storage for cell use

CELLULAR RESPIRATIONCellular Respiration occurs in light simultaneously with photosynthesis. It occurs in the cytoplasm and mitochondria.

It is the reverse reaction of photosynthesis.

Function = chemical energy release

C6H12O6 + 6O2 + 6H2O 6CO2 + 12H2O+

chemical energy

(reactants) (products)

CULTURAL EUTROPHICATION

Cultural Eutrophication & Anoxia

• Eutrophication: natural process; over 1000’s of years, lakes fill in with sediment, become marshes then dry land

• Cultural Eutrophication: same process, but speeded enormously by loading with “limiting nutrients” (typically P, sometimes N)

• Problems associated with cultural eutrophication– Algal blooms – Water anoxia

ROCK CYCLE

HUMAN IMPACTS ON THE ROCK CYCLE

• 1. Humans are excavating minerals and removing rock material. It takes millions of years for rock to form.

• 2. Humans remove sediments for building materials. This removes sediments that may form sedimentary rocks in the future.

• 3. Humans are filling in wetlands (peatlands), area that will form future coal beds.

1. Which part of the atmosphere is the ozone layer right above?A. Stratosphere B. Troposphere C. Mesosphere D. Thermosphere

2. How long does it take rock formations to form?A. 1,000 years B. 10,000 years C. 100,000 years D. 1,000,000 years E. 10,000,000 years

3. What is cultural eutrophication good for?A. Fish B. Dissolved Oxygen in the lake C. algae D. clear lake

Works Cited

1. http://science.pppst.com/carboncycle.html2. westernreservepublicmedia.org/earthmotion3/

images/Carbon_Cycle.ppt3. clima-dods.ictp.it/d3/annalisa/ocean_sv/lecture1.ppt4. www.geology.wmich.edu/Koretsky/envs2150/

Pcycle_1.ppt