Biogeochemical Cycles

I. Biogeochemical Cycles - Flow of chemical elements & compounds between living organisms & the physical environmentChemicals :

Absorbed or ingested by organisms (food chain)

Returned to the soil, air, and water by:1. Respiration 3. Lithosphere2. Excretion 4. Decomposition

Biogeochemical Processes

1. Regulate nutrients

2. Influence climate stability

3. Influence the purity of drinking water

Biogeochemical Cycles & the Earth

A. Water Cycle

B. Carbon Cycle

C. Nitrogen

D. Sulfur

E. Phosphorus

Water Cycle

Estimate of Global Water Distribution – Gleick, 1996

Volume

(1000 km3) Percent of

Total Water Percent of

Fresh Water Oceans, Seas, & Bays 1,338,000 96.5 -

Ice caps, Glaciers, & Permanent Snow

24,064 1.74 68.7

Groundwater 23,400 1.7 -

Fresh (10,530) (0.76) 30.1

Saline (12,870) (0.94) -

Soil Moisture 16.5 0.001 0.05

Ground Ice & Permafrost 300 0.022 0.86

Lakes 176.4 0.013 -

Fresh (91.0) (0.007) 0.26

Saline (85.4) (0.006) -

Atmosphere 12.9 0.001 0.04

Swamp Water 11.47 0.0008 0.03

Rivers 2.12 0.0002 0.006

Biological Water 1.12 0.0001 0.003

Total 1,385,984 100.0 100.0

Estimate of Global Water Distribution – Gleick, 1996

Volume

(1000 km3) Percent of

Total Water Percent of

Fresh Water Oceans, Seas, & Bays 1,338,000 96.5 -

Ice caps, Glaciers, & Permanent Snow

24,064 1.74 68.7

Groundwater 23,400 1.7 -

Fresh (10,530) (0.76) 30.1

Saline (12,870) (0.94) -

Soil Moisture 16.5 0.001 0.05

Ground Ice & Permafrost 300 0.022 0.86

Lakes 176.4 0.013 -

Fresh (91.0) (0.007) 0.26

Saline (85.4) (0.006) -

Atmosphere 12.9 0.001 0.04

Swamp Water 11.47 0.0008 0.03

Rivers 2.12 0.0002 0.006

Biological Water 1.12 0.0001 0.003

Total 1,385,984 100.0 100.0

A. Water Cycle Vocabulary Review

EvaporationLiquid water is heated by sun &

changed to water vapor Condensation

Water vapor is cooled and turns to liquid water droplets

PrecipitationAny form of water falling from the

sky

Water Cycle Vocabulary Review cont’

RechargeReplenishing of the water table

(usually by rain or melting snow)Runoff

Water that does not get absorbed by the ground and flows over an impermeable surface

Water Cycle Vocabulary Review cont’

UsageWhen plants &/or animals remove

water from the water table (ground water storage)

SurplusOccurs when the water table is full and

usage is low (may cause floods)Defecit

Occurs when usage is high & the water table drops (drought)

1. Effects of Human Activities on Water Cycle

Humans alter the water cycle by:Withdrawing large amounts of

freshwaterClearing vegetation and eroding soilsPolluting surface and underground

waterContributing to climate change

Ex.Deforestation & Water Pollution

2. Carbon Cycle/Global Warming Affect the Water Cycle

Increased ↑ temperature increased ↑precipitation, runoff, and soil moisture

Feedback from increased temp:

Increased ↑ cloud cover (1) reflects light back into the atmosphere, so decreased temp (Upper Atmosphere)

Increased ↑ cloud cover (2) water vapor absorbs heat in the atmosphere, so ↑ increased temp (below clouds)

B. Carbon Cycle

A biochemical circulation of the element carbon through the Earth System

1. Carbon is the building block of life

Carbon Cycle Cont’

2. Carbon is changed into different compounds as it goes through the cycle

CH4 = Methane Gas CO2 = Carbon Dioxide C6H12O6 = Carbohydrate (Sugar)

Carbon Cycle Cont’

3. Carbon enters atmosphere as Carbon Dioxide (CO2):

Exhaled by animals (Respiration) O2+Food = CO2+H2O+Energy

Produced by decomposers

3. Carbon Dioxide Enters Atmosphere Cont’

Released by burning Wood & Fossil Fuels

Released by Volcanic Eruptions

Diffuses out of the Oceans

Carbon Cycle Cont’

4. Carbon leaves atmosphere as CO2 taken up by plants during photosynthesis (trees, grass, algae)

CO2+H2O+sunlight =C6H12O6(Food) +O2

Carbon is stored in plant tissue as (C6H12O6) CarbohydratesEx. Glucose

Carbon Cycle Con’t

5. Animals eat plant Carbohydrates

6. Or algae/phytoplankton in oceans dies

Settles to bottom & becomes sediment

o Lithification- Sediment hardens /compacts into rock

7. Ocean is known as a Carbon Sink because it stores carbon

8. Carbon dioxide from Atmosphere is dissolved in the ocean during wave action

• Forms bicarbonate & Calcium Carbonate (lime that forms sea shells)

Carbon Cycle Con’t

Land Ocean

Air

1. Burial – Limestone Formation2. Fossilization

Carbon Cycle

HW KeyR

espi

ration

Pho

tosy

nthe

sis

Photosynthe

sis

Respiration

Lithification

Oil

NaturalGas

Coal

Shell formation

Wea

ther

ing

&

Ero

sion

Bur

ning

&

deca

y

absorption & desorption

volc

anis

m

Limestone

9. Effects of Human Activities on Carbon Cycle

Adding excess CO2 to the atmosphere:

Burning fossil fuels

Clearing vegetation faster than it is replaced

Figure 3-28

10. Relevance of Carbon Cycle to Climate Change

• CO2 in atmosphere is increasing 0.4% a year (= 40% in 100 yr.)

• Increasing CO2 causes increased temperatures. (Greenhouse effect)

• Heat captured by the atmosphere:a. CO2 = 50%b. CH4 = 20%c. CFCs = 15%d. NO2, H2O, O3 = 15%

Nitrogen Important to living things because

it is required to form amino acids Building blocks of proteins  

Most living things cannot use nitrogen gas in their cells

C. Nitrogen Cycle

Use nitrogen from the atmosphere to form ammonia (NH3) Form of nitrogen that plants can use

Live in the soil and in the roots of legumesEx of Legumes: peanuts, beans and clover

1. Nitrogen fixing bacteria

2. Nitrifying bacteria make NH3 into:

NO2- = Nitrites

NO3- =NitratesMost common form of nitrogen for plants, found in fertilizers

3. Animals get the nitrogen they need from proteins in the food they consume

4. Decomposers return the nitrogen to the soil in the form of ammonia which restarts the cycle

Nitrogen Cycle Cont’

http://watercycle.gsfc.nasa.gov/

5. Human Alter the Nitrogen Cycle by:

Adding gases that contribute to acid rainAdding 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

6. 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 3-30

a. Effects of Increased Nitrogen

1. Loss of soil nutrients (Ex. calcium, potassium)

2. Acidification of rivers and lakes (fertilizers and combustion of coal)

3. Increases nitrogen oxides in the atmosphere

(greenhouse gas—global warming)

(reduce ozone—increasing UV penetration)

a. Effects of Increased Nitrogen Cont’

4. Aids in spreading weeds into nitrogen poor areas (Eutrophication of lakes, ponds, streams)

Eutrophication

The process by which a body of water acquires a high concentration of nutrients.

Ex. of nutrients = phosphates and nitratesPromotes excessive growth of algaeAlgae die and decomposeHigh levels of organic matter and the

decomposing organisms deplete the water of available oxygen

Causes the death of other organisms, such as fish

a. Effects of Increased Nitrogen Cont’

5. Increasing nitrogen increases carbon fixation (linked to carbon cycle)

6. Increasing acidification increases weathering (increases rate of phosphorous cycle)

D. Sulfur Cycle

Acidic fog and precipitation

Ammonium

sulfate

Ammonia

Sulfuric acid Water

Sulfur trioxide

Oxygen Hydrogen sulfide Sulfur dioxide

Volcano Industries

Dimethyl sulfide

Ocean

Metallic

sulfide

deposits

Decaying matter

Animals

Plants

Hydrogen sulfide

Sulfur

Sulfate salts

1. Key Compounds of the Sulfur Cycle

a) Dimethyl sulfideb) Sulfur dioxidec) Sulfur trioxided) Sulfuric Acide) Ammonium Sulfatef) Hydrogen Sulfide

a. Dimethyl sulfide (CH3)2S

• Emissions from Phytoplankton

• Occurs over oceans

b. Sulfur dioxide SO2

Emissions:Industries example : power plantsVolcanoes

c. Sulfur trioxide SO3

• Primary agent in acid rain• SO3 (l) + H2O (l) → H2SO4 (l)

d. Sulfuric acid H2SO4

Gas released by cutting onions combines with water in your eye to form Sulfuric acid

Principal uses include: Ore processing Fertilizer processing Oil refining

e. Ammonium Sulfate (NH4)2SO4

Made when ammonia reacts with H2SO4

Uses: Fertilizer Agricultural spray

- aids for water soluble pesticides

f. Hydrogen Sulfide H2S

Emitted by volcanoes and hot springsRemains in atmosphere for 18 hoursChanges into sulfur dioxide

1. Importance in Biochemical Cycle

Nutrient for organismsBacteria oxidize sulfur for energy

(black smokers on ocean floor)Factor for plant

productivity

2. Effects of Human Activities on the Sulfur Cycle

Humans add sulfur dioxide to the atmosphere by:Burning coal and oilRefining sulfur containing petroleumConvert sulfur-containing metallic

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

E. Phosphorous

1. First isolated in 1669 by Hennig Brand, (German physician and alchemist)

Trying to make goldLet urine stand for days Boiled it down, captured gases &

condensed them

Phosphorus cont’

Results = white, waxy substance that glowed in the dark

Brand had discovered phosphorus

2. Greek means "light bearer

1. Phosphorus cont’

3. Essential to living organisms because it forms

DNA RNA ATP Fats of cell membranes

Phosphorus cont’

4. Not common in biosphere

5. Slowest biogeochemical cycle

6. Remains mostly on land in rock/soil minerals & in ocean sediments

7. Strictly a Lithosphere – Hydrosphere – Biosphere cycle (not Atmosphere)

Fig. 3-31, p. 77

Dissolvedin Ocean

Water

Marine Sediments Rocks

uplifting overgeologic time

settling out weatheringsedimentation

LandFoodWebs

Dissolvedin Soil Water,Lakes, Rivers

death,decomposition

uptake byautotrophs

agriculture

leaching, runoff

uptake byautotrophs

excretion

death,decomposition

mining Fertilizer

weathering

Guano

MarineFoodWebs

8. Effects of Human Activities on the Phosphorous Cycle

Removal large amounts of phosphate from the earth to make fertilizer

Reduce phosphorous in tropical soils by clearing forests

Add excess phosphates to aquatic systems from runoff of animal wastes and fertilizers

II. Laws of Thermodynamics

1st Law –energy/matter cannot be created nor destroyed, only changed from one form to another

E= mc2 Einstein

Laws of Thermodynamics

2nd Law- when energy changes, it is converted from a more useful, more concentrated form to a less useful, less concentrated form

Energy can never be recycled completely. Some energy is lost, usually as heat or light

III. Intro Energy Cycle

The movement of energy into & out of the Earth System

The amount of energy that enters the system should = the amount of energy that is removed Solar GeothermalTidal

A. Solar Power

99.985% of energy that enters the Earth’s system is from the sun

Drives the winds, oceans & waves

Causes rocks to weather, forming soil

1. Albedo

The percentage of energy that is reflected off the Earth without being changedForest = low albedo

reflects 5-10%Snow covered

field = high albedo 80-90%

Energy Flow

100 Units of sunlight entering Earth’s Atmosphere

51 Units are absorbed by surface

B. Geothermal Energy

.013% is energy from within the Earth Friction & radioactive

material

Drives the movement of the plates

Powers volcanoes, geysers, earthquakes & the rock cycle

C. Tidal Energy

.002% is energy that results from the Sun & Moon’s pull on Earth’ s ocean

Slows Earth’s rotation