NUTRIENT CYCLING

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NUTRIENT CYCLING

• ORGANISMS are comprised of
• - C, H, O, N, S and about 20 other "essential"
  elements
• BIOGEOCHEMICAL
• CYCLES

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• Global water cycle
• Differential evaporation - precipitation over
  land and sea

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Atmospheric Rivers
Taken Feb. 16, 2004
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Soil-water migration - average watershed in
Central Maine
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CARBON CYCLE (Gaseous cycle)
respiration fermentation
photosynthesis

• Buildup of organic matter - fossil fuels

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See similar in text Fig. 194
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The cycle has a dynamic nature

• The addition of CO2 to the atmosphere through
  fossil fuel burning in
• a) 1900 - 1 billion tons
• b) 1955 - 2 billion tons
• 1980 - 5 billion tons
• Currently about 7 billion tons
• (1960-1980 from about 325 ppm to 345 ppm)
• CO2 content of atmosphere in 1988 was 351 ppm and
  in 1992 was 356 ppm
• In 1996 it was 363 ppm, in 1999 it was 370 ppm
• CO2 content of atmosphere in 2004 was 377 ppm
• In 2006 it was measured at 381 ppm - a dramatic
  rise since 2004

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Recent CO2 Trend
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• CO2 taken up by the ocean can be pumped to the
  ocean floor and stored there for long periods.

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Another part of the answer increased plant
growth.

• Problem decreasing forest mass of the tropics
  and the decay and burning from that deforestation
  
• European studies growth of the temperate forests
  over the past 20 years
• Forests vs. pasture

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NITROGEN CYCLE(Gaseous cycle)

• When proteins are broken down in respiration, a
  waste product containing nitrogen is released.
• Usually, the waste product of cells is ammonia
• Decomposers can break down urea and similar
  compounds to ammonia

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Nitrogen Cycle
Denitrification
Bacteria
Bacteria
NH3 (NH4)
Bacteria
Nitrification
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Nitrogen fixation

• Rhizobium bacteria and blue green bacteria
  (cyanobacteria)
• Lightning - converts N and O gas to NO, which
  combines with oxygen to form NO2.
• NO2 water in the atmosphere -gt NO3

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Ammonification

• Changing of organic N to Ammonium (NH4)
• Accomplished by decay bacteria and fungi
• NH4 can be utilized by plants

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Nitrification (accomplished by chemosynthetic
autotrophs)

• NH4 --gt NO2 (by Nitrite bacteria)
• NO2 --gt NO3 (by Nitrate bacteria)

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Denitrification

• Bacteria using nitrate in place of Oxygen as
  electron donors.
• Mostly in anaerobic conditions

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See text Fig. 193
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Primary Productivity - Nutrient Runoff
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Nitrogen in the Forest(Atmospheric component
missing)
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Cycling time
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Biome types where are the main reserves of N?
Taiga
Tundra
Grassland
Deciduous forest
Equatorial forest
Savannah
Soil
Above ground
Root
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N content leaf decomposition

• Text Fig. 19.7

Text Fig. 19.12
Text Fig. 19.7
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Effect of grazers on N cycle
Text Fig. 19.19
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Exotic species
Myrica is the largest source of N input to this
Hawaiian ecosystem.
Text Fig. 19.20
Some species can have major effects on mineral
cycling and change net flux for some nutrients.
Text Fig 19.21
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Ways we interfere with the N cycle

• Emission of large quantities of NO (nitric oxide)
  
• NO combines to form HNO3 (nitric acid) -gt acid
  rain and fog.
• Emission of nitrous oxide (N2O) into atmosphere.
  
• Mining mineral deposits for commercial inorganic
  fertilizers.
• Adding excess nitrate ions and ammonium ions to
  aquatic ecosystems

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SEDIMENTARY VS. GASEOUS CYCLES

• FOR PHOSPHORUS
• Soil Dissolved Phosphates Decomposer
  Phosphatising Bacteria
• Add excretion from Consumer to Dissolved
  Phosphates and erosion from Phosphate rocks to
  Dissolved Phosphates.

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Phosphorus in the forest
Litterfall
Forest Floor
Retranslocation
Soil Organic P
Uptake
Phosphate P
(Dissolved)
Immobilization
Mineralization
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Overall Phosphorus Cycle
FERTILIZER
GUANO
agriculture
weathering
uptake by autotrophs
uptake by autotrophs
weathering
LAND FOOD WEBS
DISSOLVED IN OCEAN WATER
MARINE FOOD WEBS
DISSOLVED IN SOIL WATER, LAKES, RIVERS
death, decomposition
death, decomposition
settling out
weathering
sedimentation
ROCKS
MARINE SEDIMENTS
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P stream inputs and outputs
Text Figs. 19.24 19.25
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Lake Phosphorus
Text Fig. 19.28
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SULFUR CYCLE - gaseous and sedimentary

• Enters atmosphere from
• 1. combustion of fossil fuels
• 2. volcanic action
• 3. gases released by decomposition
• Generally is released as H2S, but is quickly
  oxidized to SO2.
• 150 thousand metric tons of SO2 annually
  introduced to the atmosphere through human
  activities
• 99 of the SO2 reaching the atmosphere comes
  from human activities.

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Sulfur Cycle
Hydrogen sulfide (H2S)
Oxygen (O2)
Atmosphere
Sulfur dioxide (SO2) and Sulfur trioxide (SO3)
Water (H2O)
Dimethyl (DMS)
Industries
Sulfuric acid (H2SO4)
Volcanoes and hot springs
Ammonia (NH2)
Oceans
Fog and precipitation (rain, snow)
Ammonium sulfate (NH4)2SO4
Animals
Plants
Sulfate salts (SO42-)
Aerobic conditions in soil and water
Decaying organisms
Sulfur (S)
Anaerobic conditions in soil and water
Hydrogen sulfide (H2S)
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Atmospheric

• 1. S02 -----oxidation------gtS03
• happens more quickly in a polluted atmosphere in
  the presence of nitrous oxides and hydrocarbons
• other metallic oxides (Fe, Mn, Cu, Pb, Al) aid
  also
• Fe oxide can make the change occur in the dark
• 2. SO3 ---------gt H2SO3 or H2SO4

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Sulfur Cycle
Hydrogen sulfide (H2S)
Oxygen (O2)
Atmosphere
Sulfur dioxide (SO2) and Sulfur trioxide (SO3)
Water (H2O)
Dimethyl (DMS)
Industries
Sulfuric acid (H2SO4)
Volcanoes and hot springs
Ammonia (NH2)
Oceans
Fog and precipitation (rain, snow)
Ammonium sulfate (NH4)2SO4
Animals
Plants
Sulfate salts (SO42-)
Aerobic conditions in soil and water
Decaying organisms
Sulfur (S)
Anaerobic conditions in soil and water
Hydrogen sulfide (H2S)
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Release of Sulfur deposits

• Bacteria act on dead organic material and release
  the sulfur as hydrogen sulfide or sulfate.
• Sulfur, in the presence of Fe and anaerobic
  conditions precipitates as FeS2
• Pyrytic rocks (containing ferrous sulfide) often
  overlie coal deposits.
• When exposed to air and water, the FeS2 oxidizes
  to FeSO4 (ferrous sulfate) and H2SO4 or ferrous
  hydroxide (Fe(OH3))

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Means of reducing the SO2 added to the
atmosphere Prevention

• 1. Burn low sulfur coal
• 2. Remove sulfur from coal.
• 3. Convert coal to gas or liquid fuel.
• 4. Fluidized bed combustion (FBC) of coal.
• removes about 90 of the SO2, reduces CO2 by
  20, and increases energy efficiency by 5..
• 5. Remove sulfur during combustion by limestone
  injection multiple burning (LIMB).

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Dispersion or Cleanup

• 6. Use smokestacks tall enough to pierce the
  thermal inversion layer.
• 7. Remove pollutants after combustion by using
  flue gas scrubbers.
• 8. Add a tax on each unit emitted.

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