Geochemical CyclesGeochemical Cycles

Geochemical CyclesGeochemical CyclesCarbon CycleCarbon Cycle

Early atmosphere of Earth 95% COEarly atmosphere of Earth 95% CO22. . Photosynthetic plants removed some of the COPhotosynthetic plants removed some of the CO22 and added Oand added O22. Today’s atmosphere is 0.04% . Today’s atmosphere is 0.04% COCO22!!

Reactions of photosynthesis and cellular Reactions of photosynthesis and cellular respiration couldn’t take place without carbon. respiration couldn’t take place without carbon. These two reactions form a continuous cycle.These two reactions form a continuous cycle.

Two important sources of Carbon are the ocean Two important sources of Carbon are the ocean (since CO(since CO22 dissolves easily in H dissolves easily in H220) and rocks 0) and rocks (such as coal, ore and limestone formed from (such as coal, ore and limestone formed from dead organisms)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.

And, another way to look at the carbon cycle:

Humans affect the Carbon CycleHumans affect the Carbon Cycle

Burning of fossil fuels, (Burning of fossil fuels, (oil, coal and oil, coal and

natural gas).natural gas). Fossil fuels were formed very long Fossil fuels were formed very long

ago and is “fixed”: essentially ago and is “fixed”: essentially locked out of the carbon cycle. locked out of the carbon cycle.

By burning fossil fuels the carbon is By burning fossil fuels the carbon is released back into the cycle. released back into the cycle.

We presently release more carbon into the We presently release more carbon into the air than can be reabsorbed by air than can be reabsorbed by photosynthetic organisms, thereby we have photosynthetic organisms, thereby we have a net INCREASE of carbon in the cycle. a net INCREASE of carbon in the cycle.

This atmospheric carbon has a role to play This atmospheric carbon has a role to play in the warming of the atmosphere.in the warming of the atmosphere.

Humans affect the Carbon CycleHumans affect the Carbon Cycle

Geochemical CyclesGeochemical CyclesNitrogen CycleNitrogen Cycle

Organisms require Nitrogen to form amino Organisms require Nitrogen to form amino acids for the building of proteins.acids for the building of proteins.

Lots of NLots of N22 in our atmosphere in our atmosphere

Unfortunately, most organisms CANNOT Unfortunately, most organisms CANNOT use atmospheric nitrogen.use atmospheric nitrogen.

Nitrogen-fixing bacteria CAN use NNitrogen-fixing bacteria CAN use N22 from from

the atmosphere. 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 Cycle Continued … Nitrogen-fixing bacteria live in the soil and in Nitrogen-fixing bacteria live in the soil and in

roots of legumes. roots of legumes. These bacteria also form nitrites (NOThese bacteria also form nitrites (NO22) and ) and

nitrates (NOnitrates (NO33); which are compounds containing ); which are compounds containing

N and O.N and O. Nitrate is the most common source of N for Nitrate is the most common source of N for

plants.plants. Animals get N from the proteins they eat. Animals get N from the proteins they eat. Decomposers return N to the soil in the form of Decomposers return N to the soil in the form of

ammonia and the cycle repeats.ammonia and the cycle repeats. So, oftentimes, the nitrogen cycle does not So, oftentimes, the nitrogen cycle does not

require the N to be returned to atmospheric form!require the N to be returned to atmospheric form!

Nitrogen Cycle SummaryNitrogen Cycle Summary

All living organisms require nitrogen – to All living organisms require nitrogen – to form amino acids to build proteins. form amino acids to build proteins.

Proteins are important for locomotion, Proteins are important for locomotion, reproduction, defense, and structure.reproduction, defense, and structure.

Nitrogen makes up 78% of atmosphere as Nitrogen makes up 78% of atmosphere as NN2 2

Nitrogen-fixing bacteria are very important - Nitrogen-fixing bacteria are very important - NN22 needs to be “fixed” before it can be used needs to be “fixed” before it can be used

by most living things.by most living things.

NITROGEN CYCLEN2

Crops

Fertilizer Production

Lightning

Legume

Nitrogen-Fixing

Bacteria in soil & roots

NitrogenFixation

Ammonia

NitratesNitrites

Decomposers

Denitrification

Sheep

(GAS)

From the production and use of nitrogen From the production and use of nitrogen fertilizers to the burning of fossil fuels in fertilizers to the burning of fossil fuels in automobiles, power plants, and industries, automobiles, power plants, and industries, humans impact this cycle.humans impact this cycle.

Nitrogen is essential to living organisms and Nitrogen is essential to living organisms and its availability plays a crucial role in the its availability plays a crucial role in the world's ecosystems.world's ecosystems.

Excessive nitrogen additions can pollute Excessive nitrogen additions can pollute ecosystemsecosystems

Humans affect the Nitrogen CycleHumans affect the Nitrogen Cycle

Increased global concentrations of nitrous Increased global concentrations of nitrous oxide (Noxide (N22O), a potent greenhouse gas, in O), a potent greenhouse gas, in the atmosphere the atmosphere

Increased concentrations of nitric oxide, Increased concentrations of nitric oxide, (NO) that drive the formation of smog along (NO) that drive the formation of smog along with Nwith N22OO

Losses of soil nutrients such as calcium and Losses of soil nutrients such as calcium and potassium that are essential for long-term potassium that are essential for long-term soil fertilitysoil fertility

Humans affect the Nitrogen CycleHumans affect the Nitrogen Cycle

Acidification of soils and of the waters Acidification of soils and of the waters of streams and lakesof streams and lakes

Greatly increased transport of nitrogen Greatly increased transport of nitrogen by rivers into estuaries and coastal by rivers into estuaries and coastal waters where it is a major pollutant.waters where it is a major pollutant.

Humans affect the Nitrogen CycleHumans affect the Nitrogen Cycle