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Geochemical Cycles. Water Cycle  Movement of water among ocean, atmosphere, and land.  Enters atmosphere through evaporation and transpiration (plant.

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Presentation on theme: "Geochemical Cycles. Water Cycle  Movement of water among ocean, atmosphere, and land.  Enters atmosphere through evaporation and transpiration (plant."— Presentation transcript:

1 Geochemical Cycles

2 Water Cycle  Movement of water among ocean, atmosphere, and land.  Enters atmosphere through evaporation and transpiration (plant leaves) Hurricane Katrina approaches Evaporation = water changing from liquid form to gas Transpiration = plant leaves losing water to the atmosphere

3 Geochemical Cycles Water Cycle  When air is warmed up, the particles get farther apart (and so have lower density).  H 2 0 rises in columns of warm air and may remain in atmosphere for about 2 weeks.  As the H 2 0 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.

4 Water Cycle  Enters land through precipitation and condensation.  Enters lakes or rivers through runoff  Enters groundwater where it enters the biosphere. When water vapor in the air cools (usually at night), it condenses on grass ( dew ) or in the air ( fog ). Runoff = any water moving across the land Groundwater = any water stored underground!

5 WATER CYCLE OCEANS LAKES Mountains Streams SU N Run Off Aquifer Groundwater Movement of water vapor by wind Precipitation Evaporation Precip and Conden Evaporation & Transpiration

6 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

7 Geochemical Cycles Carbon Cycle  Early atmosphere of Earth 95% CO 2. Photosynthetic plants removed some of the CO 2 and added O 2. Today’s atmosphere is 0.04% CO 2 !  Reactions of photosynthesis and cellular respiration couldn’t take place without carbon. These two reactions form a continuous cycle.  Two important sources of Carbon are the ocean (since CO 2 dissolves easily in H 2 0) and rocks (such as coal, ore and limestone formed from dead organisms) Carbon is found in the atmosphere primarily as CO 2 Photosynthesis : Plants taking CO 2 out of the atmosphere and using it to produce sugar. Cellular Respiration : Organisms take that sugar and in the process of burning energy release CO 2 back into the atmosphere.

8 CARBON CYCLE Volcanoes Burning of fossil fuels Photosynthesis Respiration CO 2 in the ATMOSPHERE CO 2 dissolved in the OCEAN FOSSIL FUELS Photosynthesis Used by man Created over time Land Biomass Aquatic Biomass Oil, Natural Gas, Coal… Limestone Dolomite Plant s Respiration Animals Plants Animals

9 And, another way to look at the carbon cycle:

10 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.

11  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. Humans affect the Carbon Cycle

12 Geochemical Cycles Nitrogen Cycle  Organisms require Nitrogen to form amino acids for the building of proteins.  Lots of N 2 in our atmosphere  Unfortunately, most organisms CANNOT use atmospheric nitrogen.  Nitrogen-fixing bacteria CAN use N 2 from the atmosphere. Nitrogen-fixing bacteria convert atmospheric N 2 into ammonia (NH 4 ) which is a form of nitrogen that plants CAN use.

13 Nitrogen Cycle Continued …  Nitrogen-fixing bacteria live in the soil and in roots of legumes.  These bacteria also form nitrites (NO 2 ) and nitrates (NO 3 ); 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!

14 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 N 2  Nitrogen-fixing bacteria are very important - N 2 needs to be “fixed” before it can be used by most living things.

15 NITROGEN CYCLE N2N2 Crops Fertilizer Production Lightning Legume Nitrogen-Fixing Bacteria in soil & roots Nitrogen Fixation Ammonia Nitrates Nitrites Decomposers Denitrification Sheep (GAS )

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17  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 Humans affect the Nitrogen Cycle

18  Increased global concentrations of nitrous oxide (N 2 O), a potent greenhouse gas, in the atmosphere  Increased concentrations of nitric oxide, (NO) that drive the formation of smog along with N 2 O  Losses of soil nutrients such as calcium and potassium that are essential for long-term soil fertility Humans affect the Nitrogen Cycle

19  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. Humans affect the Nitrogen Cycle


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