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Geochemical Cycles. 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.
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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
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.
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).
SUN WATER CYCLE Precipitation Precip and Conden Movement of water vapor by wind Mountains Evaporation & Transpiration Run Off Streams LAKES Evaporation OCEANS Aquifer Groundwater
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
Geochemical Cycles Carbon Cycle • Early atmosphere of Earth 95% CO2. Photosynthetic plants removed some of the CO2 and added O2. Today’s atmosphere is 0.04% CO2! • 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 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.
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.
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.
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.
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!
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.
Sheep NITROGEN CYCLE N2 Fertilizer Production Lightning Denitrification (GAS) Nitrogen Fixation Crops Legume Nitrogen-Fixing Bacteria in soil & roots Decomposers Ammonia Nitrates Nitrites
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
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
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.
