156 EHHALT 



also the possibility that a fraction of the tropospheric CH 4 is taken up by the 

 soil and consumed by microorganisms. A small fraction, about 10%, of the CH 4 

 enters the stratosphere and is destroyed there, mainly by the same reaction that 

 acts in the troposphere. The resulting reaction products are very important for 

 the chemistry and the water and ozone budget of the stratosphere. The CH 4 

 cycle is closed at the earth's surface, where the ultimate reaction products of 

 CH 4 , C0 2 , and H 2 are photosynthesized to plant matter. Some of the plant 

 matter enters the soil as litter, a fraction of which is eventually decomposed 

 anaerobically with the release of CH 4 . The CH 4 cycle makes a small but 

 significant contribution to the carbon cycle. Between 1.8 X 10 5 and 

 8.0 X 10 1 5 g C0 2 /year pass through it annually. This amounts to a few percent 

 of the annual C0 2 uptake by land plants which is about 1 30 X 10 1 5 g/year. 



REFERENCES 



1. M. V. Migeotte, Spectroscopic Evidence of Methane in the Earth's Atmosphere, Phys. 

 Rev., 73: 519-520(1948). 



2. U. Fink, D. H. Rank, and T. Q. Wiggins, Abundance of Methane in the Earth's 

 Atmosphere, Office of Naval Research Report NR-014-401, 1965. 



3. A. E. Bainbridge and L. E. Heidt, Measurements of Methane in the Troposphere and 

 Lower Stratosphere, Tellus, 18: 221-225 (1966). 



4. D. H. Ehhalt, Methane in the Atmosphere, J. Air Pollut. Contr. Ass., 17: 518-519 

 (1967). 



5. S. Manabe and R. T. Wetherald, Thermal Equilibrium of the Atmosphere with a Given 

 Distribution of Relative Humidity, J. Atmos. Sci, 24: 241-259 (1967). 



6. J. C. McConnell, M. B. McElroy, and S. C. Wofsy, Natural Sources of Atmospheric CO, 

 Nature, 233: 187-188(1971). 



7. W. F. Libby, unpublished. 



8. G. E. Hutchinson, A Note on Two Aspects of the Geochemistry of Carbon, Amer. J. 

 Sci, 247: 27-32 (1947). 



9. S. F. Singer, Stratospheric Water Vapor Increase Due to Human Activities, Nature, 233: 

 543-545 (1971). 



10. E. Robinson and R. C. Robbins, Sources, Abundance, and Fate of Gaseous Atmospheric 

 Pollutants, Final Report, Stanford Research Institute, February 1968. 



11. T. Koyama, Gaseous Metabolism in Lake Sediments and Paddy Soils and the Production 

 of Atmospheric Methane and Hydrogen, J. Geophys. Res., 68: 3971—3973 (1963). 



12. P. S. Conger, Ebullition of Gases from Marsh and Lake Waters, Publication 59, 

 Chesapeake Biology Laboratory 42, 1943. 



13. J. W. Swinnerton and V. J. Linnenbom, Gaseous Hydrocarbons in Sea Water: 

 Determination, Science, 156: 1119-1120(1967). 



14. H. Levy, Normal Atmosphere: Large Radical and Formaldehyde Concentrations 

 Predicted, Science, 173: 141-143 (1971). 



15. N. R. Greiner, Hydroxyl Radical Kinetics by Kinetic Spectroscopy. VI. Reactions with 

 Alkanesin the Range 300-500° K,J. Chem. Phys., 53: 1070-1076 (1970). 



16. D. H. Ehhalt, L. E. Heidt, and E. A. Martell, The Concentration of Atmospheric- 

 Methane Between 44 and 62 Kilometers Altitude, J. Geophys. Res., 77: 1972 (in press). 



17. R. E. Newell, Water-Vapor Pollution in the Stratosphere by the Supersonic Trans- 

 porter?, Nature, 226: 70-71 (1970). 



