Biogeochemical Cycles

Energy FlowsMatter Cycles

Matter Cycles

A cycle is a group of processes in which matter repeatedly moves through a series of reservoirs.A reservoir is a place where matter or energy is stored. (atmosphere, hydrosphere, geosphere, biosphere)Many elements on Earth move between reservoirs. These cycles rely on energy sources to drive them.The length of time that energy or matter spends in a reservoir can vary from a few hours to several million years.

Biogeochemical Cycle

Click below to watch the Visual Concept.

The Water (Hydrologic) Cycle

If there is magic on this planet it is water

-Loren Eisley

“All the rivers run into the sea, yet the sea is not full…” - Ecclesiastes 1:7

The Water Cycle

The movement of water from the atmosphere to Earth’s surface and back to the atmosphere is called the water cycle.

In the water cycle, water changes from liquid water to water vapor through the energy transfers involved in evaporation and transpiration. During these processes, water absorbs energy and changes state.

When the water loses energy, it condenses to form water droplets, such as those that form clouds. Eventually, water falls back to Earth’s surface as precipitation.

Oceans – more evaporation than precipitationLand – more precipitation than evaporation (Runoff). Land is watered by the system.

Important Concepts

Water Quantity

The Earth’s water supplyOceans 97 %Atmosphere .0010 %Cryosphere (Ice caps/Glaciers) 2.23 %Salt Lakes .007 %Freshwater Lakes .009 %Rivers/Streams .0001 %Groundwater & Soil .609 %

Water Quantity cont’d

99.4% of Earth’s water is in the Oceans or Cryosphere (icecaps and glaciers) Of the remaining .6% only about .3 % is available to humans with current technology.

Freshwater lakes .009 %Rivers & Streams .0001 %Shallow Groundwater .303 %

– Total .3121 %

This totals approximately 21 billion gallons per person, which may sound like enough. However, the problem is that freshwater is not evenly distributed geographically.Humans now, as a GEOLOGIC force are able to affect (usually short-circuit) the hydrologic cycle.It is estimated that 60 % of all water withdrawn worldwide is “consumed” (or diverted from its normal water cycle pathway).

Human interactions with the Water Cycle

Excessive evaporation losses from irrigated land.Water diverted from one river or watershed to another.Groundwater pumped faster than it can be recharged into natural aquifers.Contamination of groundwater, lakes or rivers. (silt, sewage, fertilizers, pesticides, radioactive waste, toxic waste, heavy metals, pathogens, heat.)Excessive evaporation from reservoirs.

Water Cycle (summary)

Because freshwater on the planet is a renewable resource (as long as the Sun shines) we will never run out. However Human activity may modify the distribution and storage capacity in certain regions.

The Water Cycle

http://earthguide.ucsd.edu/earthguide/diagrams/watercycle/

The Water Cycle

Check up

What source of energy drives the water cycle? Explain.Describe how water moves through the water cycle.From what sources does water evaporate?List 3 ways that humans interact with the water cycle.

The Carbon CycleCarbon moves through all four spheres through the carbon cycle.In the short-term carbon cycle, plants convert carbon dioxide, CO2, from the atmosphere into carbohydrates(photosynthesis). When organisms’ bodies break down the carbohydrates and release some of the carbon back into the air as CO2 or through their organic wastes as CO2 (respiration),or methane CH4 (decomposition).

In the long-term carbon cycle, carbon is stored in the geosphere in a type of rock called a carbonate.

The Carbon Cycle

Check up

What source of energy ultimately drives the carbon cycle? ExplainIn what form is carbon found in the atmosphere? Where does it come from?Cellulose, which makes up the walls of plant cells contains carbon. What is the source of this carbon?How does carbon become part of the body of an animal?How is carbon released from the body of an animal?Briefly explain two ways that humans are interacting or impacting the natural carbon cycle.

Nitrogen Cycle

78% of Earth’s Atmosphere is Nitrogen

Used to build proteinsMost organisms cannot use atmospheric form, it must be changed or “fixed”N2 NO3

- or NH4

+

The Nitrogen Cycle

In the nitrogen cycle, nitrogen moves from the air to soil, from soil to plants and animals, and back to air again.Nitrogen is removed from air mainly by the action of nitrogen-fixing bacteria in the soil.The nitrogen then is taken up (absorbed) by plants. Plants are then are eaten by animals. Animals use the Nitrogen for building proteins and amino acids.

Nitrogen Cycle

The nitrogen is returned to the soil by decay and by animal wastes.Chemical processes that occur in the soil then release the nitrogen back into the air. Nitrogen in the atmosphere can also be fixed by the occurrence of lightning.

Nitrogen cycle

Check up

What source of energy ultimately drives the nitrogen cycle? ExplainHow do animals obtain nitrogen?In what form is nitrogen found in the atmosphere? What form of nitrogen are most plants able to absorb? How does it get into that form?List and explain two processes that return nitrogen to the atmosphere.

Human interaction

All natural cycles can be altered by human activities.The carbon cycle is affected when humans use fossil fuels.Deforestation removes the Earth’s ability to naturally “metabolize” CO2.

The nitrogen and phosphorus cycles are affected by agriculture.

What is meant by the phrase: Humans have become a Geologic

Force

Credits

Fred Montague, Environment Notebook, pp 108-112, Mountain Bear Ink, 2003Holt Earth Science 2010 edition