w a ~ Shank. 1977), Not measured. Bsoil value is an average for 0-1 cm soil depth computed from 1974, 1975 data from Health Physics monitoring Stations 33, 34 » and 38 (Environmental Monitoring Reports UCC ND 302 and Y/UB-4) and from site survey report (Oakes and Shank . 1977); Air value based on composite of samples from ORNL air monitoring stations (Oakes and f x 100. [238puj/[Total Pu] Values in parentheses are « 2 *38py; a % 235py Calculated for plant area and floodplain from data and model given in Environmental Monitoring Report, UCC ND 302, pp. 17 and 24. e d. Pu releases to the atmopshere in 1974 were 9 mCi yr=! and 0.004 mCi yr~! for Savannah River and Oak Ridge respectively. c Data on Pu released to atmosphere and onsite airborne concentrations from Milham et aZ., 1976 soil concentra-— tions of Pu are from McLendon et al. 1976 Offsite deposition and airborne concentrations are from Anonymous, 1975 Onsite deposition of Pu is unpublished data. 0.035 (17) 1.7 (15) k 210 (17) 10 (35) Ambient” © During Soil Cultivation Air Concentration (fCi m*3) *tThe 3 mCi km72 isopleth is within 1 km of the SRP source; the offsite region is beyond 20 km of the source. 0.0168 0.038 0.006 (16) 0.006 (8) 1.08 (43) 0.09 (14) Soil (0 - 15 cm) Suspendible 306 b wot? 4.1 (5) 25 to 150 (5) NM 6 x 1075°. 0.057 (12) Savannah River2?Or¢ 3 mCi km** isopleth Offsite 4.3 (58)4 Soil Concentration (pCi g ') Isotopic ratios of Pu can help differentiate between several potential sources causing environmental contamination, Thus, contributions of Pu from local sources and deposition from fallout can be distinguished, provided isotopic ratios of source terms are different. For example, the a % 239Pu for airborne Deposition (pCi m-? wk~!) A floodplain contaminated in 1944 contains from 25 to 150 pCi e7! of Pu mixed throughout the top 15 cm of the soil profile, The deposited Pu has been subjected to soil and ecological processes for over 30 years. Vegetation growing at the floodplain site {s exposed only to soil Pu. The element is not detectable in daily air samples unless airborne dust is generated by disturbances such as soil cultivation, a practice not routinely carried out in contaminated environments. Environmental Matrix Current release of Pu from Oak Ridge facilities to the atmosphere is negligible (UCCND, 1975, 1976). Incremental contribution of Pu to the local terrestrial environment is not distinguishable quantitatively or isotopically from Pu that originates from global fatlout. However, Pu released from Oak Ridge in liquid effluents has contaminated aquatic and terrestrial environments along White Oak Creek. PLUTONIUM IN ENVIRONMENTS OF NUCLEAR FACILITIES AT SAVANNAH RIVER AND OAK RIDGE Concentrations and characteristics of Pu in Savannah River and Oak Ridge environments are presented in Table 1, “An important distinction between the sites is that che annual atmospheric input of Pu to the study area at Savannah River is more than 3 orders of magnitude greater than the input to the floodplain site at Oak Ridge (footnote c, Table 1). The maximum concentration of Pu in soil at Savannah River (3 mCi km-?) is located within 1 km of the processing plant, while the concentration of Pu in offsite soils beyond 20 km from the processing plant was less than 2 mCi km72 (McLendon et al., 1976). The offsite soils:are approximately equivalent to the average accumulation of Pu from global fallout in sotl of middle latitudes (Hardy ef al., 1973). Near the processing plant, the ambient average air concentration was 1.7? fCi m~3 which increased by 1 to 2 orders of magnitude when dust was created by agricultural activities (Milham et al., 1976). Selective analysis of suspendible particles from the soil surface (approximately the 1 mm zone) shows that this fraction contains one to two orders of magnitude higher concentration of Pu than the 0 to 15 cm increment of the soil profile (McLendon et al., 1976; Milham et al., 1976). TABLE 1 PLUTONIUM LN SAVANNAH RIVER AND OAK RIDGE ENVIRONMENTS Plant Area [ Oak Ridge® Floodplain Vegetation is continuously contaminated as a result of chronic low-level release of Pu to the atmosphere at Savannah River, and direct deposition of Pu on vegetation by the aerial route probably is the most important pathway (Milham et al,, 1976). By comparison, at Oak Ridge, Pu was deposited on a floodplain in 1944 and plant uptake from the contaminated soil by the root pathway is considered to be the major pathway. With different source characteristics for Pu in terrestrial environments, the relative importance of aerial vs. root pathways of Pu incorporation by vegetation can be evaluated.