Back to Nitrogen Cycle            OXYGEN CYCLE                                     Forward to Phosphorus Cycle
 
 
 

                        Oxygen Cycle
                Image obtained from http://www.accessexcellence.com/AB/GG/photo_Resp.html
 
 

                  Facts:

           Sources of Oxygen:
                     1) photodisassociation of H2O vapor
                            2) photosynthesis

                   Since oxygen is so reactive its cycling is complex:
                     1) As a constituent of CO2 it circulates freely
                    throughout the biosphere.
                            2) Some CO2 combines with Ca to form carbonates.
                            3) O2 combines with nitrogen compounds to form
                    nitrates.
                            4) O2 combines with iron compounds to form ferric
                    oxides.
                            5) Photosynthesis and respiration
                            6) O2 in the troposphere is reduced to O3 (ozone).
                    Ground level O3 is a pollutant which damages lungs.
 

                                            Back to Nitrogen Cycle [Main Page]Forward to Phosphorus Cycle
              [Phosphorus Cycle; Sulfur Cycle; Nitrogen Cycle; Carbon Cycle]