Geochemical Cycles

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Geochemical Cycles
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Water Cycle
Evaporation water changing from liquid form to
gas

• Movement of water among ocean, atmosphere, and
  land.
• Enters atmosphere through evaporation and
  transpiration (plant leaves)

Transpiration plant leaves losing water to the
atmosphere
Hurricane Katrina approaches
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Geochemical Cycles

• Water Cycle
• When air is warmed up, the particles get farther
  apart (and so have lower density).
• H20 rises in columns of warm air and may remain
  in atmosphere for about 2 weeks.
• As the H20 vapor rises, it cools into droplets
  (condenses), forming clouds

Condensation water vapor transforming into
liquid water. Occurs because cooler air does not
have as much space to hold water vapor.
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Water Cycle
Runoff any water moving across the land

• Enters land through precipitation and
  condensation.
• Enters lakes or rivers through runoff
• Enters groundwater where it enters the biosphere.

Groundwater any water stored underground!
When water vapor in the air cools (usually at
night), it condenses on grass (dew) or in the air
(fog).
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SUN
WATER CYCLE
Precipitation
Precip and Conden
Movement of water vapor by wind
Mountains
Evaporation Transpiration
Run Off
Streams
LAKES
Evaporation
OCEANS
Aquifer
Groundwater
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Humans affect the water cycle

• Higher global temperature increased evaporation.
• Higher ocean temps increase evaporation
• Reduction in rainforest reduces transpiration.
• Reduction of plant life increases runoff
• Glacial melting reduces amount of reflected light

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Geochemical Cycles

• Carbon Cycle
• Early atmosphere of Earth 95 CO2. Photosynthetic
  plants removed some of the CO2 and added O2.
  Todays atmosphere is 0.04 CO2!
• Reactions of photosynthesis and cellular
  respiration couldnt take place without carbon.
  These two reactions form a continuous cycle.
• Two important sources of Carbon are the ocean
  (since CO2 dissolves easily in H20) and rocks
  (such as coal, ore and limestone formed from dead
  organisms)

Carbon is found in the atmosphere primarily as CO2
Photosynthesis Plants taking CO2 out of the
atmosphere and using it to produce sugar.
Cellular Respiration Organisms take that sugar
and in the process of burning energy release CO2
back into the atmosphere.
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And, another way to look at the carbon cycle
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Humans affect the Carbon Cycle

• Burning of fossil fuels, (oil, coal and natural
  gas).
• Fossil fuels were formed very long ago and is
  fixed essentially locked out of the carbon
  cycle.
• By burning fossil fuels the carbon is released
  back into the cycle.

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Humans affect the Carbon Cycle

• We presently release more carbon into the air
  than can be reabsorbed by photosynthetic
  organisms, thereby we have a net INCREASE of
  carbon in the cycle.
• This atmospheric carbon has a role to play in the
  warming of the atmosphere.

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Geochemical Cycles

• Nitrogen Cycle
• Organisms require Nitrogen to form amino acids
  for the building of proteins.
• Lots of N2 in our atmosphere
• Unfortunately, most organisms CANNOT use
  atmospheric nitrogen.
• Nitrogen-fixing bacteria CAN use N2 from the
  atmosphere.

Nitrogen-fixing bacteria convert atmospheric N2
into ammonia (NH4) which is a form of nitrogen
that plants CAN use.
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Nitrogen Cycle Continued

• Nitrogen-fixing bacteria live in the soil and in
  roots of legumes.
• These bacteria also form nitrites (NO2) and
  nitrates (NO3) which are compounds containing N
  and O.
• Nitrate is the most common source of N for
  plants.
• Animals get N from the proteins they eat.
• Decomposers return N to the soil in the form of
  ammonia and the cycle repeats.
• So, oftentimes, the nitrogen cycle does not
  require the N to be returned to atmospheric form!

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Nitrogen Cycle Summary

• All living organisms require nitrogen to form
  amino acids to build proteins.
• Proteins are important for locomotion,
  reproduction, defense, and structure.
• Nitrogen makes up 78 of atmosphere as N2
• Nitrogen-fixing bacteria are very important - N2
  needs to be fixed before it can be used by most
  living things.

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NITROGEN CYCLE
N2
Fertilizer Production
Lightning
Denitrification
(GAS)
Nitrogen Fixation
Crops
Legume
Nitrogen-Fixing Bacteria in soil roots
Decomposers
Ammonia Nitrates Nitrites
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Humans affect the Nitrogen Cycle

• From the production and use of nitrogen
  fertilizers to the burning of fossil fuels in
  automobiles, power plants, and industries, humans
  impact this cycle.
• Nitrogen is essential to living organisms and its
  availability plays a crucial role in the world's
  ecosystems.
• Excessive nitrogen additions can pollute
  ecosystems

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Humans affect the Nitrogen Cycle

• Increased global concentrations of nitrous oxide
  (N2O), a potent greenhouse gas, in the atmosphere
  
• Increased concentrations of nitric oxide, (NO)
  that drive the formation of smog along with N2O
• Losses of soil nutrients such as calcium and
  potassium that are essential for long-term soil
  fertility

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Humans affect the Nitrogen Cycle

• Acidification of soils and of the waters of
  streams and lakes
• Greatly increased transport of nitrogen by rivers
  into estuaries and coastal waters where it is a
  major pollutant.