Cesium in Soils
and Plants in the Sagebrush Steppe Ecosystem
Investigators
and Affiliations
Lawrence L. Cook,
Graduate Student, Graduate Student, Department of Biological
Sciences, Idaho State University, Pocatello, ID
Richard S. Inouye, Professor, Department of Biological Sciences,
Idaho State University, Pocatello, ID
Terence P. McGonigle, Associate Professor, Department of Botany,
Brandon University, Brandon, Manitoba, Canada
Funding Sources
The Idaho State
University Department of Biological Sciences
The Idaho State University Center for Ecological Research and
Education
The Inland Northwest Research Alliance
The Idaho State University Graduate Student Research and
Scholarship Committee
A Bechtel Educational Outreach Program grant awarded to Richard
Inouye
Sigma Xi
Accomplishments
This research was conducted as part of a doctoral program and
has been completed.
Dissertation
Abstract
Cesium (Cs)
movement in ecosystems is important due to Cs radioisotopes
introduced via nuclear technologies. Stable Cs uptake by plants
is comparable to Cs radioisotopes. Three lines of investigation
were used to determine stable Cs movement in the sagebrush
steppe ecosystem of the eastern Snake River Plain. First, 27
sites were surveyed to determine Cs concentrations in 28 soil
and 330 plant samples. Titanium (Ti) was used to indicate soil
contamination on plant samples. Cesium in soils correlated with
quartz and cation exchange capacity. Cesium in plants correlated
with Ti. Transfer factors, i.e., the concentration ratio of
plant Cs to soil Cs, were on the order of 10-3.
Second, the
validity of Ti to indicate soil contamination was assessed.
Milling inert filter paper indicated that background Ti levels
account for concentrations to 10 mg Ti•kg plant-1.
Concentrations of Ti and Cs associated with seedlings grown in a
dust-free environment increased significantly with moderate
dusting. Washing dust-laden plants with seven washing agents
revealed none as superior in removing soil from seven species
and none was effective in removing all soil from any one
species. Energy dispersive spectrometry showed plant surface
elemental signatures consistent with soil coatings.
Third, four
grasses were evaluated as phytoremediation candidates via
greenhouse experiments. The species were Agropyron spicata
(bluebunch wheatgrass), A. cristatum (crested
wheatgrass), Leymus cinerus (Great Basin wildrye), and
Bromus tectorum (cheatgrass). Plant Cs concentrations were
higher in Cs-spiked soil. Total Cs per seedling was greatest in
the high Cs, high fertility, and high moisture soil treatment
combination.
These studies
indicated: (1) the uptake of Cs by regional plants is low and
much of the Cs is in soil adhering to plant surfaces, (2) Ti is
a reliable indicator of soil contamination for plant samples
slated for trace element analysis and should be used when
assessing trace element composition of field samples, and (3)
Great Basin wildrye, bluebunch wheatgrass, crested wheatgrass,
and cheatgrass are viable phytoremediation agents when used in a
strategy combining soil fertilization and irrigation and
possibly stable Cs addition. Preference should be given to the
native bluebunch wheatgrass and Great Basin wildrye because they
do not negatively impact regional biodiversity.
