476 TRANSURANIC ELEMENTS IN THE ENVIRONMENT 



where yy and C^ are plutonium concentrations (pCi/g) of vegetation and soil, respectively, 

 X is distance from ground zero, and a and b are constants derived from least-squares 

 analysis. If bj > by, the vegetation/soil ratio will increase with increasing distance from 

 ground zero and decreasing soil concentration. 



To obtain an expression for plutonium concentration in vegetation as a function of 

 soil concentration, R. 0. Gilbert (personal communication) performed a regression 

 analysis to fit the available data (636 paired samples of vegetation and soil) to the 

 following equation: 



in(yv) = ln(a)+bln(Cs) 



V= A + bS 



or 



where V= In (yy) 



S = ln(Cs) 



A = In (a) 



^ ^ r SV^^(l/n)(SV)^ '. 

 ISS^ -(l/n)(SS)^J 



A = V - bS 



V and S = the mean of V and S, respectively. 



[This method of calculating b is indicated because measurements of both yy and Cs are 

 subject to error. See Ricker (1973) for a discussion of this method of calculation.] 

 The results of tliis analysis are summarized as follows: 



H 



With antilogs, the mean vegetation/soil ratio is 



yy(nCi/g) 



Crv 



Cs(nCi/g) 



0.0303 

 0.3937 



0.0770 



which is somewhat lower than the value (0.096) obtained from the grouped data 

 presented by Romney et al. (1975). 



