1. Biogeochemical Cycles
Carbon Cycle
Phosphorous Cycle
Sulfur Cycle
Water Cycle
Nitrogen Cycle

2. Biogeochemical Cycle:
The complete path a chemical takes through the four major components of Earth’s systems.
Atmosphere – atmos refers to vapor so in this case we mean the gases in the environment
Hydrosphere – hydro refers to “water” so in this case we mean oceans, rivers, lakes, groundwater, and glaciers
Lithosphere – litho means “stone” so in this case we mean rocks and soils
Biosphere – bio means “life” so in this case we mean living things such as plants and animals

3. Biogeochemical Cycles and Life: Limiting Factors
Macronutrients
Elements required in large amounts by all life
Include the “big six” elements that form the fundamental building blocks of life:
carbon, oxygen, hydrogen, phosphorus, nitrogen, sulfur
Micronutrients
Elements required either in
small amounts by all life or
moderate amounts by some forms of life and not all by others
Limiting factor
When chemical elements are not available at the right times, in the right amounts, and in the right concentrations relative to each other

4. Processes in Carbon Cycling
Carbon cycles between the living (biotic) and non-living (abiotic) environments.
Gaseous carbon is fixed in the process of photosynthesis and returned to the atmosphere in respiration.
Carbon may remain locked up in biotic or abiotic systems for long periods of time, e.g. in the wood of trees or in fossil fuels such as coal or oil.
Humans have disturbed the balance of the carbon cycle through activities such as combustion and deforestation.
Burning fossil fuels
Petroleum

5. The Carbon Cycle

6. © 2008 John Wiley and Sons Publishers

7. Changing the location of Carbon is a major issue in global warming.
Carbon is moving from fossil fuels to the atmosphere as CO2 .
It took millions of years to form fossil fuels (detritus underground + time, heat, and pressure.)
We are pumping fossil fuels out of the ground in hundreds of years.

8. Carbon Transformations
Most Carbon moves around when things eat each other.
Processes other than trophic are:
Geological sedimentation of carbon in the ocean. Carbon comes out of solution.
Combustion of fossil fuel moves Carbon to the atmosphere
Major Carbon Sinks:
The Ocean
Forests

9. Phosphorus Cycling
Phosphorus cycling is very slow and tends to be local; in aquatic and terrestrial ecosystems, it cycles through food webs.
Phosphorous is lost from ecosystems through run-off, precipitation, and sedimentation.
A very small amount of phosphorus returns to the land as guano (manure, typically of fish- eating birds). Weathering and phosphatizing bacteria return phosphorus to the soil.
Human activity can result in excess phosphorus entering water ways from runoff of animal wastes, fertilizers and discharges from sewage treatment systems and is a major contributor to eutrophication.
Deposition as guano…
Loss via sedimentation…
Fertilizer production

10. The Phosphorus Cycle
Part of important molecules such as DNA and ATP as well as part of necessary ions.
It is also an essential element for life and often is a limiting nutrient for plant growth.
Phosphorus does NOT exist in the atmosphere!!
We mine large quantities of phosphate rock to make fertilizers and some detergents.

11. The Phosphorus Cycle
Guano
deposits

12. Molecular bridges in proteins
Sulfur Cycling
Sulfur is an essential component of proteins and is important in determining the acidity of precipitation, surface water, and soil.
Sulfur circulates through the biosphere as:
hydrogen sulfide (H2S)
sulfur dioxide (SO2)
sulfate (SO42-)
elemental sulfur (S)
Human activity releases large quantities of sulfur through:
combustion of sulfur-containing coal and oil,
refining petroleum,
smelting, and other industrial processes
Natural Sulfur released through volcanic eruptions
Sulfur in gasoline
Molecular bridges in proteins
Elemental sulfur

13. The Sulfur Cycle SO2 from combustible fossil fuels
Sulfates in the atmosphere (SO42-)
SO2 and sulfates from volcanoes, hot springs and biogenic activity
Reduced sulfur (H2S)
Decomposition and other processing
Microorganisms
Acid precipitation
Sulfates in water (SO42-)
Sulfates in soil(SO42-)
Uptake by plants
Sulfur in living organisms
Sedimentation of sulfides and sulfates
Organic deposition
Iron sulfides in deep soil and sediments
Uplifting in groundwater and and weathering
Mining
Inorganic sulfur
Sulfur in fossil fuels

14. Water Transformations
The hydrological (water) cycle, collects, purifies, and distributes the Earth’s water.
Over the oceans, evaporation exceeds precipitation. This results in a net movement of water vapor over the land.
On land, precipitation exceeds evaporation. Some precipitation becomes locked up in snow and ice for varying lengths of time.
Most water forms surface and groundwater systems that flow back to the sea.
Precipitation
Rivers and streams

15. Steps:
Evaporation - (liquid to gas) of water from the oceans and from land. May also occur as runoff from streams, rivers, and sub-surface groundwater
Transpiration: liquid to gas from plants
Condensation – (gas to liquid) leads to the next step
Precipitation - (water in any form falling from atmosphere) on land
Infiltration – entry of water into the earth’s surface
Percolation – when water descends through soil and rock – under root zone
Runoff – water moves from surface to bodies of water

16. The Water Cycle
Transport overland: net movement of water vapor by wind
Condensationconversion of gaseous water vapor into liquid water
Precipitation over the ocean
Rain clouds
Precipitation
(rain, sleet, hail, snow, fog)
Precipitation to land
Evaporation from the ocean
Evaporation
Evaporation from inland lakes and rivers
Evaporation from the land
Transpiration
Transpiration from plants
Groundwater movement (slow)
Surface runoff (rapid)
Infiltration: movement of water into soil
Aquifers: groundwater storage areas
Percolation: downward flow of water
Water locked up in snow and ice
Rivers
Lakes
Ocean storage
97% of total water

17. The Demand for Water
Humans intervene in the water cycle by utilizing the resource for their own needs.
Water is used for consumption, municipal use, in agriculture, in power generation, and for industrial manufacturing.
Industry is the greatest withdrawer of water but some of this is returned. Agriculture is the greatest water consumer.
Using water often results in its contamination. The supply of potable (drinkable) water is one of the most pressing of the world’s problems.
Hydroelectric power generation…
Irrigation…
Washing, drinking, bathing…

18. Nitrogen Nitrogen makes up 78% of our atmosphere
Nitrogen is used by plants and animals to make proteins
Nitrogen can be combined with other atoms to make compounds such as:
N2: nitrogen gas NO3-: nitrates
NH4+: ammonium ions NO2: nitrogen dioxide

19. Nitrogen in the Environment
Nitrogen cycles between the biotic and abiotic environments. Bacteria play an important role in this transfer.
Nitrogen-fixing bacteria are able to fix atmospheric nitrogen.
Nitrifying bacteria convert ammonia to nitrite, and nitrite to nitrate.
Denitrifying bacteria return fixed nitrogen to the atmosphere.
Atmospheric fixation also occurs as a result of lightning discharges.
Humans intervene in the nitrogen cycle by producing and applying nitrogen fertilizers.

20. Nitrogen Transformations
The ability of some bacterial species to fix atmospheric nitrogen or convert it between states is important to agriculture.
Nitrogen-fixing species include Rhizobium, which lives in a root symbiosis with leguminous plants. Legumes, such as clover, beans, and peas, are commonly planted as part of crop rotation to restore soil nitrogen.
Nitrifying bacteria include Nitrosomonas and Nitrobacter. These bacteria convert ammonia to forms of nitrogen available to plants.
Root nodules
in Acacia
Nodule
close-up

21. Eutrophication

22. National Geographic: Fertilized World (May 2013)
world/charles-text

23. 1. Nitrogen fixation Gas N2 converted to ammonia NH3 Combustion
Volcanic action
Lightning
Nitrogen fixing bacteria

24. 2. Nitrification To nitrate Preformed by soil bacteria 2 step process
Conversion of ammonia or ammonium (when water reacts with ammonia)
To nitrate
Preformed by soil bacteria
2 step process

25. 3. Assimilation
Plant roots absorb nitrate, ammonia or ammonium and incorporate these molecules into plant proteins and nucleic acids

26. 4. Ammonification
Conversion of biological nitrogen compounds to ammonia and ammonium ions
Urea in urine
Uric acid in bird waste

27. 5. Denitrification Reduction of nitrate to N2 gas
Denitrifying bacteria

28. Nitrogen Cycle

29. Check Your Understanding!
1. What is the molecular formula for nitrogen gas? _________
2. Define nitrogen fixation.
3. What type of plants are considered nitrogen fixers?
4. Why is lightning considered a nitrogen fixer?
5. How does nitrogen first enter the soil?
6. How does nitrogen become available to plant?
7. How do animals obtain the nitrogen?
8. Why do animals need nitrogen?
9. In what form(s) does nitrogen leave an animal’s body (including yours)?
10. What type of organisms return nitrogen to the soil and air?