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1975 Onsite deposition of Pu is unpublished data.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.