Science Forums 2

[Michaelangelica]

August 4, 2009
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A biogeochemical cycle is a pathway by which a chemical element, such as carbon, or compound, like water, moves through Earth's biosphere, atmosphere, hydrosphere and lithosphere.

In effect, the element is "recycled," although in some cycles the element is accumulated or held for long periods of time.

Chemical compounds are passed from one organism to another, and from one part of the biosphere to another, through biogeochemical cycles.

Water, for example, can go through three phases (liquid, solid, gas) as it cycles through the Earth system. It evaporates from plants as well as land and ocean surfaces into the atmosphere and, after condensing in clouds, returns to Earth as rain and snow.

Researchers are discovering that biogeochemical cycles--whether the water cycle, the nitrogen cycle, the carbon cycle, or others--happen in concert with one another. Biogeochemical cycles are "coupled" to each other and to Earth's physical features.

"Historically, biogeochemists have focused on specific cycles, such as the carbon cycle or the nitrogen cycle," said Tim Killeen, NSF assistant director for geosciences. "Biogeochemical cycles don't exist in isolation, however. There is no nitrogen cycle without a carbon cycle, a hydrogen cycle, an oxygen cycle, and even cycles of trace metals such as iron."

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"Seemingly subtle chemical changes may have large effects," said Cole.

"Consider that global climate change is caused by increases in carbon dioxide and methane, gases which occupy less than ½ of one percent of the atmosphere. Now more than ever, we need a comprehensive view of Earth's biogeochemical cycles."
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Details about the ESA CBC sessions may be found by visiting the links below.

nsf.gov - National Science Foundation (NSF) News - Earth's Biogeochemical Cycles, Once in Concert, Falling Out of Sync - US National Science Foundation (NSF)