Entry 15: Nutrient/Biogeochemical Cycles 2

Well, I hope you have a undersatnding of Nutrient cycles already, if you have not, please read the last post. The content may seem quite difficult to understand initially, as I copied most information from websites and put them here without rephrasing as it's really difficult to rephrase certain parts. I hope you undersatnd, Ms Qiu. Read slowly, and you should be able to get it though.
Without further ado...Many elements cycle through ecosystems, organisms, air, water, and soil. Many of these are trace elements. Other elements, including carbon, nitrogen, oxygen, hydrogen, sulfur, and phosphorus are critical components of all biological life. Together, oxygen and carbon account for 80 percent of the weight of human beings. Because these elements are key components of life, they must be available for biological processes. Carbon, however, is relatively rare in the Earth's crust, and nitrogen, though abundant in the atmosphere, is in a form that is not useable by living organisms. The biogeochemical cycles transport and store these important elements so that they can be used by living organisms. Each cycle takes many different pathways and has various reservoirs, or storage places, where elements may reside for short or long periods of time. Each of the chemical, biological, and geological processes varies in their rates of cycling. Some molecules may cycle very quickly depending on the pathway. Carbon atoms in deep ocean sediments may take hundreds to millions of years to cycle completely through the system. An average water molecule resides in the atmosphere for about ten days, although it may be transported many miles before it falls back to the Earth as rain. I shall elaborate on the water cycle in my next post, do read on.

Informatrion obtained from:
1)http://www.enviroliteracy.org/subcategory.php/198.html
2)http://library.thinkquest.org/C007506/cycles.html