yon concentration in vegetation as a Funct To obtain an expression for plutonium performed (Gilbert, Persona ; was is analys sion regres a n, of soil concentratio an data (636 paired samples of vegetation communication) to fit the available n: equatio ing follow the soil) to In Cy.) v = (1n a) +b in (C ( s)> yy = 0.0620 C 9.76 The corresponding equation for the vegetation/soil ratio is: Cry = yy/C, = 0.062 C,-0-24 Equations (11) and (12) demonstrate the dependence of vegetation concentration on soil concentration and the fact that the vegetation/seil ratio tends to increase as soil concentration increases. The use of either equation for purposes may y be Limited by ¥ the extreme range Pred ictive purp g of sotl and vegetation g values and/or by various site specific factors which are not considered in the regression analysis, It might be better to apply the regression analysis to | where v - (in Yy) S =1n (C.), s°? A (Ina) i 7 | 5 bs bv - = (Ly) | I AzV- bs - Sampling strata means as shown in Table 3}. | Ta1ee? >Ss - (375) (12) Thus, for areas in which soil concentrations are 10, 1.0, and O.E nCi/g, the predicted vegetation/soil ratios would be 0.036, 0.062, and 0.107, respectively. . veA+ bs or a) \ Except for Strata 3 and 4 in Area 13, the measured and predicted values given in Table 3 seem to agree quite well, but the equations for Area 13 and GMX-5 (footnote to Table 3) predict higher values (especially at higher soil concentrations} than would be obtained from Equations (11) and (12), which are based on samples from all study areas. 3 where ¥ ig the mean of V and § is the mean of S- Discussion 1lts of this analysis are summarized as follows: The results n/soil ratios may be Equations (11) and (12) shed some light on how vegetatio expected to vary with respect to soil concentration, but they do not explain why. To approach this and related questions, we refer back to Equations (7) and (8), the proposed differential equations for the external and internal components of plant contamination. For the time being, at least, we can dismiss Equation (8) from further consideration because the greenhouse studies have shown that root uptake cannot account for more than a small fraction of the vegetation/soil ratios observed at NTS. both vy and cated because measurements of er, 1973). This method of calculating b is indi C, are subject to error (see Rick Parameter Standard Deviation eee 2.3096 . ae . V = -3.4961 7 = 0.9322 b= 0.7602 r= n 0.8084 (correlation coefficient) 636 Equation (7) For external contaminatfon has the following solucion: 0.0458 A = -2.7871 Ye vegetation/so 11 ratio is: Taking, antilogs, BS, the mean Cry = ¥y/ Cy, = 0-0303/0.3937 = 0.0770 (nci/g)/(nci/g), . which is somewhat lower than the waive (0.096) 9 presented by Romney ct al, (1975). brained from the grouped data a function of 30 il concentration (nCi/g) as The equations for vegetation is: concentration (nCi/g) = Kays OF) w g FA [l-exp(-Q. +4, g +4, )8)] A (13) where the parameters are defined following Equation (7), and ky = VyFy I = c, = bio, where, Vg is the deposition velocity on soil (cm/day), and Lg 18 a mass loading factor (g(soil)/cm*(air)). F, is a vegetation interception factor fen? /g (vegetation)), 641 (14) (15)