RATIOS IN TRANSURANIC ELEMENT STUDIES 201 



10 



c 



< 



o 

 z 

 o 

 o 





> 



0.01 



0.001 



0.023D 



ln(Y) = -2.66 - 0.00898D 



10 



0.1 



o 



c 



< 



LU 



o 



z 

 o 

 o 



o 



(/I 



3 

 ui 

 n 



0.01 



0.001 



100 200 300 



DISTANCE FROM GZ, ft 



400 



Fig. 10 Uranium-235 concentrations in vegetation and soil as a function of distance 

 from GZ at A site, Area 11, Nevada Test Site. 



where ai , |3i , ei and tta > i^a . ^2 represent, respectively, the parameters and error terms of 

 the regression of In vegetation concentration on distance and In soil concentration on 

 distance. Equation 4 corresponds to line 1 in Fig. 10 and Eq. 5 to hne 2. This approach 

 assumes that ei and €2 are related; they represent, respectively, the deviations from the 

 models given by Eiqs. 4 and 5 on the same unit, in this case location. Again the 

 straight -line fits look reasonable; for vegetation the univariate R^ =0.45 and for soil 

 R^ =0.77. 



The multivariate approach has two advantages: (1) it can be used to check the 

 assumption of proportionaHty that underlies the use of the ratio and (2) it can help 



