Oxygen cycles

Example 7.2 (a) Write the reduction and oxidation half-reactions that take place in the respiration process  

Answer Analyzing the change in oxidation numbers, carbon changes from O-v +4 In order to balance the number of electrons, this reaction is multiplied by 6 and 24e + 24H+ + 602 - 12H20 

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Some battery designs have a one-way valve for pressure rehef and operate on an oxygen cycle. In these systems the oxygen gas formed at the positive electrode is transported to the negative electrode where it reacts to reform water. Hydrogen evolution at the negative electrode is normally suppressed by this reaction. The extent to which this process occurs in these valve regulated lead —acid batteries is called the recombination-efficiency. These processes are reviewed in the Hterature (50—52). 

The oxygen cycle is often described by equation 16 at the positive electrode, and the reverse of equation 16 at the negative electrode,... 

These equations are based on the thermodynamically stable species. Further research is needed to clarify the actual intermediate formed during overcharge. In reahty, the oxygen cycle can not be fully balanced because of other side reactions, that include gtid corrosion, formation of residual lead oxides in the positive electrode, and oxidation of organic materials in the cell. As a result, some gases, primarily hydrogen and carbon dioxide (53), are vented. 

The Flow of Energy in the Biosphere and the Carbon and Oxygen Cycles Are Intimately Related... 

FIGURE 18.3 The flow of energy in the biosphere is coupled primarily to the carbon and oxygen cycles. 

P. Cloud and A. Gibor, The oxygen cycle. Article 4 in Chemistry in the Environment, pp. 31-41, Readings from Scientific American, W. H. Freeman, San Francisco, 1973. P. Brimblecombe, Air Composition and Chemistry, Cambridge Univ. Press, Cambridge, 1986, 224 pp. 

Carbon-nitrogen-oxygen cycle CNO fusion cycle in stars greater than 1 M(.) that produces odd-mass nuclei 13C, 150 and 15N. 

THE INFLUENCE OF ORGANIC MATTER ON THE GLOBAL BIOGEOCHEMICAL OXYGEN CYCLE... 

Farquhar J, Thiemens MH (2000) The oxygen cycle of the Martian atmosphere-regoUth system secondary phases in Nakhla and Lafayette. J Geophys Res 105 11991-11998 Farquhar J, Chacko T, Ellis DJ (1996) Preservation of oxygen isotopic compositions in granuhtes from Northwestern Canada and Enderby Land, Antarctica implications for high-temperature isotopic thermometry. Contr Miner Petrol 125 213-224 Farquhar J, Thiemens MH, Jackson T (1998) Atmosphere-surface interactions on Mars mea-... 

The oxygen cycle is the biogeochemical cycle that describes the movement of oxygen within and between its three main reservoirs the atmosphere, the biosphere, and the lithosphere. The main driving factor of the oxygen cycle is photosynthesis, which is responsible for the modern Earth s atmosphere and life. 

Anthropogenic impacts on the oxygen and ozone cycles 4.5.3.1 Oxygen cycle and anthropogenic processes... 

The oxygen cycle is complicated by its ability to take part in a lot of chemical reactions giving a multitude of epicycles. This fact makes the oxygen cycle sufficiently stable but hinders assessment of its stability. 

Harrison J.A. Matson P.A. and Fendorf S. (2005). Effects of a diel oxygen cycle on nitrogen transformations and greenhouse gas emission in a eutrophied, subtropical stream. Aquatic Sciences, 67, 308-315. 

Petsch ST (2004) The global oxygen cycle. In Schlesinger WH (ed) Treatise on Geochemistry, Vol. 8, Biogeochemistry. Elsevier, Amsterdam, pp 515-555... 

The Atmosphere. - The Hydrosphere. - Chemical Oceanography. - Chemical Aspects of Soil. - The Oxygen Cycle. - The Sulfur Cycle. - The Phosphorus Cycle. - Metal Cycles and Biological Methyla-tion. - Natural Organohalogen Compounds. -Subject Index. 

I had expected a report on oxygen cycles which would be more concerned with the more general atmospheric problems of its formation and changes that might occur under certain regimes. 

In some respects, the oxygen cycle in the atmosphere is most concerned with ozone chemistry which will be discussed later today. The effect of nitrogen fertilizers on the atmosphere would be most strongly felt through perturbation of stratospheric ozone. The general consensus now seems to be that the effect of nitrogen fertilizers upon the atmosphere will be small compared to the magnitude of other sources. 

Hamersley, M. R., and Howes, B. L. (2003). Contribution of denitrification to nitrogen, carbon, and oxygen cycling in tidal creek sediments ofa New England salt marsh. Mar. Ecol. Prog. Ser. 262, 55—69. 

Jenkins, W. J., and Goldman, J. C. (1985). Seasonal oxygen cycling and primary production in the... 

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