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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’
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