484 TRANSURANIC ELEMENTS IN THE ENVIRONMENT 



equations for the long-term components of the lungs and lymph nodes and for the 

 gastrointestinal tract, respectively. The solution to Eq. 22 is 



rba(t) = Ia (0.0021 +0.015(1 - e^^> ') + 5.61 X 10"^ (e-^^* -e"^-*) 



+ 3 X 10"' [0.381 +0.12(1 -e"-^'^)]} (26) 



Integration of Eq. 26 and evaluation of the integral from t = to t = 1 77 days give the 

 amount reaching the blood in 1 77 days as 0.676 la . Applying this result to the Area 1 3 cow, 

 the total ^^^Pu expected to have entered the blood via inhalation would be 3.76 pCi. 

 Compared with 3000 pCi for ingestion (see above), this is a negligible quantity. 



On the basis of this comparison, we shall assume that plutonium concentrations in 

 cow milk, muscle, and liver are due to ingestion only, or, conversely, that the 

 contribution from inhalation is negligible. Even after 10 yr of exposure in Area 13, the 

 contribution from inhalation would be no more than 0.56% of the total. 



Comparison of Model Predictions and Field Data. Plutonium concentrations in lungs, 

 liver, and muscle are given in Table 4 for four cows included in the Area 13 grazing study. 



TABLE 4 Concentrations of ^ ^ ^ '^ "* ^ Pu in Tissues of 

 Cattle Grazed in Area 13 (NTS) 



*Data extracted from Smith, Barth, and Patzer (1976). 

 t Data extracted from Smith (1977). 

 :j:Not reported. 



Cow 2 (Smith, Barth, and Patzer, 1976) was placed in the inner compound for 177 days. 

 Cows 1, 4, and 6 grazed the outer compound for 433 days (Smith, 1977). Cow 1 weighed 

 252 kg, and cow 4 weighed 300 kg; the weiglit of cow 6 is not known. We shall assume 

 that the average weight of the cows from the outer compound was 275 kg. Tissue weights 

 for these cattle were not reported; but we estimate for a 275 -kg cow that the average lung 

 weight is about 2.1 kg and the average liver weiglit is 4.8 kg, based on a study made by 

 Smith and Baldwin (1974). At 45% of body weight (Smith, 1977), the muscle weight for a 

 275-kg cow would be about 125 kg. 



Lungs. On the basis of these and other considerations, the concentration of ^^^Pu in 

 the lungs of the cows from the outer compound of Area 13 can be estimated as follows: 



P _ (76mVday)(10~^ g/m^)(215 pCi/g)(Q.18) 1 -e''^^^^ 

 ^""^ 2AYg X 



= 55 pCi/kg (vs. 48 pCi/kg, Table 4) 



