Department of Nuclear Engineering and Radiation Health Physics
Oregon State University, 116 Radiation Center, Corvallis, Oregon 97331-5902
T 541-737-2343 | F 541-737-0480 | nuc_engr@ne.engr.orst.edu | http://ne.oregonstate.edu
Earthfort ProVide Testing at Oregon State University
Introduction:
Seventy years of development in the nuclear industry has seen an increase in the use and utility of
radionuclides in a variety of fields. The responsible use of radioactivity provides electricity, medical
treatment, and many industrial applications to millions across the globe. Along with the beneficial uses of
radioisotopes come costs and risks. Accidents have the potential to disperse radioactivity over significant
geography; when radionuclides are inadvertently released to the environment they can pose human and
environmental hazards and the ability to mitigate accidents and remediate contaminated lands is crucial
one.
The remediation of contaminated land is time and cost intensive. In many cases the solution has been the
wholesale removal of contaminated soils and treatment of the soil as hazardous waste. This is not a
practical approach for large-scale releases and recent years have seen a number of investigations into
alternative approaches. One approach is bioremediation, the use of biota to either remove contamination
or affect its mobility in the environment. In the case of radioisotopes the hazard cannot be removed
through bioremediation, but bioremediation can affect the transport of radionuclides through the
environment. This can be tremendously valuable, if the mobility of a contaminant can be reduced this will
restrict the total area affected by the contamination minimizing the costs of remediation. Altering
environmental mobility can directly reduce the risks to humans by restricting transport into groundwater
or into agricultural crops for human consumption.
Earthfort, a Corvallis Oregon company, approached Oregon State University
to investigate the use of a proprietary bioremediation product, Earthfort’s
ProVide. Graduating students in Nuclear Engineering and Radiation Health
Physics at Oregon State conducted a series of experiments to determine the
effect of Earthfort’s products on the mobility of radiocesium in soil.
Experimental Design:
Twenty 35 cm soil columns were constructed and packed with soil. The
bottom 5 cm of each column was rock filled to simulate a water table. Figure
1 is an illustration of the soil column design. Any water that percolated
through the column was collected for analysis. Also considered was the effect
of plants on radiocesium mobility both with and without Earthfort’s ProVide.
7.5 uCi (277500 Bq) of Cs-134 was applied to the surface of each column as
a CsCl salt dissolved in 1 ml of water. Water was added to each column on a
daily basis to simulate contaminated rainfall. Earthfort ProVide was applied
as directed to experimental group columns while control groups received no
ProVide. Cs-134 is an activation product rather than a fission byproduct, but
their behavior in the environment is for practical purposes identical. The
results of this work are as applicable to Cs-137 as to Cs-134.
Figure 1. Soil column
design
Results:
A more complete set of the results was provided to Earthfort, presented here is some representative data.
Figures 1 and 2 are profiles of Cs activity with depth in columns without plants. The -30 cm depth values
are activity in water that percolated through the whole column and was collected at the column’s base.
Figures 4 and 5 present the same data for columns with plants. The column depth of 5 cm represents the
fraction of the total activity added found in plant material
Figure 2. Profile of activity with depth of soil
columns containing ProVide.
Figure 3. Profile of activity with depth of soil columns
not containing ProVide.
Figure 4. Profile of activity with depth of soil
columns containing ProVide and radish.
Figure 5. Profile of activity with depth of soil
columns containing a radish and no ProVide.
Figure
Figure 6. Sum of the total activity found in radishes grown with and
without ProVide.
Discussion and Conclusions:
The results for the mobility of cesium in soil in the presence and absence of ProVide are not statistically
different. Columns with only soil showed more mobility in columns without ProVide than columns with.
Columns that grew radishes showed the opposite result, with cesium appearing to be more mobile in
columns with ProVide. There may be an explanation for these differences in the presence of the radishes
in the column, interactions between bacterial colonies and plant roots in the rhizosphere may provide
some explanation. There was significant variation within the treatment groups; any difference might be
attributable only to randomness, t-tests do not support an effect at this time.
The differences in total uptake of cesium by radishes in columns with and without ProVide are
suggestive, but not statistically defensible. If ProVide does sequester cesium, making it unavailable for
uptake by plants, this could be a valuable remediation tool. Unfortunately these data present the same
difficulty in making a definitive statistical statements; the variation within treatment groups means that
any difference might be attributable only to randomness, t-tests do not support an effect at this time.
The sample sizes for these experiments were small and the time was limited to less than a month. Further
work and more statistically robust experiments may allow for more definitive statements as to the effect
of ProVide on radiocesium mobility and uptake in plants. Expanding the timeframe of the experiments
and experimenting with a wider variety of plants and radionuclides might allow for a clearer
understanding of ProVide’s effects and allow for a statistical determination of the presence of an effect.
The work was conducted by Nichole McAllister, Matt Bensen, Michelle Comolli, Sam Hays, Jenelle
Parson, Matthew Stevens, and Jesse Whitlow.
Kathy Higley, PhD
Department of Nuclear Engineering and Radiation Health Physics
Oregon State University
Corvallis, Oregon 97331
USA
David Bytwerk, PhD
Department of Nuclear Engineering and Radiation Health Physics
Oregon State University
Corvallis, Oregon 97331
USA