METHANE IN THE ATMOSPHERE 



147 



TABLE 2 

 SOURCES OF ATMOSPHERIC CH 4 * 



atmosphere (based 



on 1.41 ppM mixing 



ratio) 

 Annual output of CH 4 



from natural-gas 



wells in 1965 

 Annual production of 



dry organic 



matter 



5.2 x 10 1 



1.65 x 10 1 



25 



*The amount of CH 4 in the atmosphere, the production by natural-gas wells and the 

 annual production of dry plant material are given in the last three lines for comparison. 



tAverage source strength taken to be equal to Koyama's (Ref. 11) value for paddy soils. 



^Area estimated by Twenhofel (Ref. 26). 



§Source strength based on average production of CH 4 by Maryland marshes (Refs. 12 

 and 27). 



^Source strength assumed to be 10% of Koyama's (Ref. 11) value for paddy soils. 



for the source strength of marshes. Therefore I have added the CH 4 productivity 

 obtained by Conger 1 2 for Maryland marshes. It is only half the value for paddy 

 soils, which is in fair agreement. If we assume this value to be more 

 representative of the global average for swamps, we obtain an annual CH 4 

 production of only 2.7 X 10 14 g/year. The correct value probably lies 

 somewhere between the two estimates given in Table 2. 



Finally, Robinson and Robbins, 1 ° in their data for humid tropical areas 

 (listed separately from their data for swamps in Table 2), assumed a source 

 strength of 0.1 of that of the paddy fields. Since the area is large, the resulting 



