42 Ol 21-year half-life as shown in the lower curves of Figures 36 and 37. o 4 CENTER 1 oO Oo O Oo 4 0.10 NA Q SOUTH © Q WEST & NORTH - KGD= 0.000 0.01 dot ec a E < w oO & 2 CENTER E = SOUTH D WEST A NORTH Preliminary measurements of *°*Ra concentration in a few samples from each of the trees as given in Tables a a ° oO oO = oO O00! 20.01 - o O 40.¢ ° Ol SCALE BKGD= 0.015 re +—T,= 21.4 yrs 0.002 0 i | 20 l 40 ! 60 i 80 9.0001 5 i AGE (YRS) Fic. 35—Variation of *°Pb specific activity with age of wood in black oak. 20.40 BO AGE BO Teo (yrs) 120 0.07 Fic, 37—-The upper curve shows variation of ™°Pb 5 activity with age of wood in White Oak II. The lower is the same with a constant background of 0.015 pCi * subtracted (see text). 0.2 STABLE Pb VS AGE 4.0 ORS o O SOUTH D WEST & NORTH & nN Y a o oe = So 2 1 214 yrs 2 a o f o NL — oo & ook Q 1 3 oO BKGD= 0.00 vA a < ~~ oO Oo 0 OOlF 7.0! Pb (.gm Pb/gm DRY) =or 2.8 0.70F WHITE OAK I 0.60 WHITE OAK IL O50 SCALE _> BKGD = 0.01 O04, oge 0.000! } 20 } 40 1 60 1 80 : loo 1 120 AGE (yrs) Fig. 36—The upper curve shows variation of ™°Pb specific activity with age of wood in White Oak I; the lower one is these data with a constant background of 0.010 pCi *°Pb/g sub- tracted (see text). 0.40 0.30 0.20 i | 20 40 l 60 ! 80 l i0O)— 120 TIME (YEARS) Fic. 38—The variations in concentrations of stable le: the various trees with age, Pay Vi