Why study radiocesium in fish
from Steel Creek?
Potential risks exist for both humans and wildlife because of the
presence of cesium-137 in Steel Creek. For example, cesium-137 may
be transferred to humans consuming fish that enter the Savannah River
from Steel Creek delta. Likewise, cesium-137 may be transferred to
wildlife that consume fish from this system. Most other isotopes of
concern have decayed away or have migrated from the creek. Research
at Steel Creek will be used to develop reliable risk assessments for
humans and wildlife, especially endangered forms.
Assessment of cleanup needs:
Data from research at Steel Creek will allow DOE to better assess
potential cleanup needs by providing baseline information regarding
the presence and availability of cesium-137 in the aquatic food chain.
In addition, newly collected data, when compared with previous data,
will allow determination of the ecological half-life of cesium-137
in Steel Creek. This, in turn, allows predictions to be made regarding
the future availability of this contaminant for uptake into food chains.
Much of the cesium-137 is no longer available to biota in the creek.
Furthering knowledge in the field of radioecology:
Research at Steel Creek will contribute to a better understanding
of the complex processes of bioaccumulation of cesium in aquatic food
chains and the behavior of cesium-137 in aquatic systems.
This understanding should enable future questions about radiocesium
in fish to be answered more easily and models for its dynamics to
Past research at Steel
Previous research by the Savannah River Ecology Laboratory (SREL)
at Steel Creek focused on questions concerning cesium-137 levels in
fish from the Steel Creek Corridor. During 1981, cesium-137 levels
were determined in fish and water
samples collected from four locations along the lower reaches of Steel
Creek between the delta and Highway 125. Results of this earlier investigation
provided valuable baseline information regarding cesium-137 levels
in fish that can be used in future investigations.
Perhaps the most important finding of this investigation was that
the ratio of radioactivity in fish vs. radioactivity in the creek
water was much higher than had generally been reported in other aquatic
systems. This high concentration factor (~3,000) was attributed
to the soft water and relatively low potassium levels in Steel Creek.
In addition to increased uptake of cesium-137, results also suggested
that bioaccumulation of cesium-137 occurred in fish from Steel Creek,
with top level predators like largemouth bass having more cesium-137
than the fish they fed upon. Exposure of wildlife depends, in part,
upon the type of fish they feed upon.
Current and future research
at Steel Creek
SREL researchers currently are determining cesium-137 levels in several
species of commercially and ecologically relevant fish species collected
from the Steel Creek delta and corridor during January -- May 1998.
The objective of this investigation is to address the following questions
concerning cesium-137 in fish from Steel Creek:
- What levels of cesium-137 currently are found in fish from Steel
- What risk is associated with humans consuming fish from Steel
- What risk is associated with wildlife consuming fish from Steel
- What is the ecological half-life of cesium-137 in Steel Creek?
- What is the magnitude of bio-accumulation of cesium-137 at higher
Several important species (i.e., species consumed by humans) from
the Steel Creek delta will be used in the development of human risk
assessments. Many of these species may migrate between Steel Creek
and the Savannah River. For select species, the equation for the frequency
distribution will be calculated to predict the probability that a
fish of a particular species will have a given level of cesium-137.
Along with information about fish body size, these data will be used
to determine the risks to humans consuming fish from Steel Creek delta
Risk assessments for wildlife consuming cesium-137 contaminated fish
will focus on Wood Storks (federally endangered species) and Bald
Eagles (federally threatened species). These risk assessments will
be based on cesium-137 levels in several ecologically relevant fish
species (i.e., species consumed by wildlife).
Levels of cesium-137 levels currently found in fish from the Steel
Creek corridor will be compared to cesium levels in fish recorded
during the 1981 SREL investigation to estimate the ecological half-life
of this radionuclide in the Steel Creek system. Tissue from each fish
also will be analyzed to determine the ratio of stable nitrogen isotopes.
These ratios will allow each fish species to be assigned to a trophic
position within the food chains of Steel Creek.
Future research needs include the continuation and completion of cesium-137
determinations and nitrogen isotope analyses for fish that already
have been collected. Furthermore, additional fish of several different
species will be collected from the Steel Creek delta during the fall
of 1998 to provide adequate sample sizes for determining frequency
distributions. Samples from these collections also will permit analyses
for seasonal variation in cesium-137 levels and will be available
for future analyses to determine levels of mercury in fish. The mercury
data will be used to refine the risk assessment calculations.
Deliverables from research
at Steel Creek
- An archived data set, including frequency distributions of cesium-137
levels in fish species from Steel Creek Delta that could be consumed
by the public or wildlife.
- Risk assessments for humans and wildlife that might be consuming
fish from Steel Creek.
- Estimation of the ecological half-life of cesium-137 in the Steel
- Contributions to the scientific community that include an increased
understanding of bioaccumulation of cesium-137 in aquatic food chains.
- Peer-reviewed publications reporting the results of research conducted
at Steel Creek.
- An informational brochure outlining risks associated with fish
consumption, to be distributed to the general public.
in Fish from Steel Creek