96 



BACASTOW AND KEELING 



To calculate by model the 14 C/C variations of wood relative to standard for any 

 specific period, e.g., the industrial period of Table 1, we assume consistent with 

 Eq. 9 



Rl Rio 



Su =^ 



R. 



'w 



1 = 



Rio a wa R. 



1 =(1 + Su,)(l +5. )-l ^Su, +5 #( 



(12) 



The value of 5 #0 varies from model to model, but, for realistic values of the 

 parameters, the value is between 0.2 and 0.3%. 



The predicted C/C ratios of oceanic carbon are similarly expressed relative 

 to the oxalic acid standard for comparison with published data, after 

 cancellation of the I 3 C/ ! 2 C normalization of these data as discussed earlier. 



R 



R r 



*Mo 



R« R io R« 



Rr 



Ri 



"wad +5 .o) 



R d R d R, R d 



R: = R7 R: = Rr awa(1+5 -° ) 



(13) 



(14) 



TABLE 1 



RADIOCARBON CONTENT OF DATED WOOD RELATIVE 



TO STANDARD* 



Average date 

 of samples 



Total number 

 of tree rings 



Number of 

 samples 



Su w (A' 



7 



'0 



C), 



Ref. 



1861 

 1862 

 1862 

 1894 

 1898 

 1899 

 1900 



2 

 9 

 9 

 1 

 1 

 9 

 8 



Base-Line Period 



1945 

 1947 

 1948 

 1948 

 1949 

 1950 

 1951 



Industrial Period 



4 4 



9 1 



8 1 



3 3 

 7 1 

 7 2 



4 2 



"Values of Su w , as defined in the text, are expressed on the conventional 

 A 14 C scale (see references) as the per mil deviations of the 14 C activity of the 

 wood samples from an age-corrected oxalic acid standard. Both samples and 

 standard have been normalized to the same ' 3 C/' 2 C ratio. 



