1971; Trabalka and Eyman, 1976; Elwood et al., 1976). This concept
substitutes the concentrations of an element in sediment and suspended
particutate matter for the concentration in water normally used in the
calculation of a CF, The underlying expectation is that, due to the
high Ky's, observed element accumulation in tissues of higher trophic
levels will be dominated by gut absorption rather than by direct uptake
which were one to two orders of magnitude greater than fish from the
lake. Data on fishes from White Oak Lake show a trend of decreased
concentrations of 7797?"°Pu at higher trophic levels (Table 2).
Comparable concentrations in plutonium were observed in the three species
which feed on bottom dwelling invertebrates (bluegill and goldfish) or
on suspended particulate matter (shad}. Stomach content analysis of
these three species showed significant amounts of clay material to be
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Tropnic Transfe r Factors (TTF) for Fresh water and Marine
Environments. TIF is defined as (Puj in Organisms
( wet weight)/[Pul in Sediment or Suspended Particulate
Matter (wet weight) .
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Figure 2.
Benthic invertebrates and rooted macrophytes (Ludwigia, Elodea, and Sagi ttoria)
from White Oak Lake contained comparable concentrations of 7°°-?*°Pu
tx
1074
Some of the variation in TTF values observed can be explained by the
relative trophic position of the organisms analyzed. The number of
intervening food chain transfers between the organism analyzed and the
abiotic source of plutonium should be inversely related to the observed
TTF value, This is demonstrated in Figure 2 where organisms at lower
trophic levels have higher TTF values than fishes, Therefore, in assessing potential transfer of plutonium to man from aquatic ecosystems, it
is important to concentrate on those food sources most closely tinked
te sediment as a measure of maximum plutonium in human food. These
would represent a short, single trophic transfer food chain as opposed
to the traditional concept of the grazer food chains. Examples of
important groups include bottom-feeding fishes, shell fish, and rooted
Macrophytes such as rice. A major dietary component of a large segment
of the world population is rice. Although we could find no data on
accumulation of plutonium in rice, this information is important since
it is representative of a single trophic transfer from sediment and/or
water to man. Noshkin (1972) pointed out that marine organisms associated
with the sediment-water interface, (i.e., benthic invertebrates) contain
one hundred times higher plutonium burdens than marine free swimming
vertebrates.
“2
4979
contamination has contributed a major fraction of observed plutonium
concentrations in phytoplankton materials in previous studies) the
maximum possible TTF value should be on the order of one. In fact values
in Figure 2 are significantly less than one, as expected.
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This term, then, serves as a realfstic measure of plutoniumdiscrimination
in food chains. If our hypothesis is correct, (i.e., sediment cross-
1071
Again, we stress that external contamination with sedimentary
particulate matter and gut loading are not considered to represent true
uptake and should be considered separately. An example of the utility
of the approach can be seen in Figure 2 where TTF is used rather than CF
to express transfer of plutonium from abiotic to biotic components in
various systems, This figure clearly shows that plutonium is discriminated
against in food chains of aquatic systems. TIF values for fishes of ~ 107?
to 107* are comparable to those observed in mammalian gavage studies
(Baxter and Sullivan, 1972; Carritt et al., 1947; Weeks et al., 1956).
WHITE OAK LAKE
from water,