i62 TRANSURANIC ELEMENTS IN THE ENVIRONMENT 



A soil-level standard of 2 (d/min) g~ ' of soil was tentatively set for the state of 

 Colorado (Johnson, Tidball, and Severson, 1976). The value of 2 (d/min) g' did not 

 specify the soil size fraction. If this value were used for tlie RF sample, then the 

 equivalent standard for the NTS would be 5 (d/min) g"' (1.26/0.52 x 2 = 5). Similar 

 calculations for ML and ORNL give 2 and 3 (d/min) g~ ' , respectively. 



Healy (1974) suggested 500 (d/min) g~' for bare soil without reference to any 

 particular site; thus this suggested level miglit be interpreted as a general guide. The soil 

 factors in Table 5 show that NTS has the lowest value of 0.52. If 500 (d/min) g^' were 

 used as a general guide, the allowable concentration for NTS would be 960 (d/min) g^' 

 (1/0.52 X 500 = 960). Similarly, for RF, ML, and ORNL, the values would be 395, 425, 

 and 615 (d/min) g^' , respectively. 



the importance of establishing a soil standard is related to long-term health risk for 

 exposed populations. For example, the U. S. Environmental Protection Agency (1977) 

 proposed a soil-screening level of 0.2 //Ci/m^ (surface 1-cm depth). This value was 

 established as a reasonable soil level whereby the resulting lung and bone doses to the 

 critical segment of the exposed population would be below proposed limits. 



TABLE 5 Soil Factor Calculated from Soil Activity Factor, 

 Depositional Factor, and Resuspendible Fraction 



Size, Soil Activity Soil activity Depositional Depositional Resuspendible Soil 



jum fraction fraction factor fraction factor fraction Pu index 



Nevada Test Site (Area 1 3) 



0.99 0.52 



0.50 0.91 7.27 1.39 0.91 1.26 



Mound Laboratory* 



<2 0.19 0.46 2.42 0.40 0.97 



2 to 4 0.09 0.14 1.56 0.12 0.19 



4tol25t 0.72 0.40 0.56 0.03 0.02 



1.00 1.00 4.54 1.18 1.00 1.18 



Oak Ridge National Laboratory 



0.98 1.00 3.14 0.69 1.00 0.69 



*Data from Muller and Sprugel, 1976. 



t Assumes particles greater than 45 jum to be less than 1 25 jum. 



