and Spitsyn, 1974a, 1974b; Giesy and Paine, 1977a). Cycling processes and
biological uptake of Pu must be understood prior to environmental releases
so that rational assessments of its hazards can be determined.
Accumulation
of plutonium by algae and bacteria is dependent upon the aqueous forms of
plutonium
(Andelman and Rozzell,
1970;
Noshkin,
1972).
While much is known
about plutonium separations chemistry, little is’ known about the environmental
chemistry and speciation of plutonium (Noshkin, 1972).
Francis (1973) stated that chelation with naturally occurring organic soil
components may be important in the movement of transuranics in natural food
chains leading to man.
Szalay (1964) suggested that humic acids be used in
the disposal of radioactive wastes because these organic compounds immobilize
radionuclides.
Pillai and Mathew (1976) studied the effects of humics on Pu
solubilization in sea water but emphasized that further information is needed
on the chemical behavior and influence of humics on Pu behavior in water.
Routson et al.
(1976)
reported that Put4 tends
While Pu-humic interactions have been
investigated
Routson, etal.,
1975;
1976),
no studies
have considered the effect ofhumics and fulvics on the availability of
plutonium to aquatic biological systems.
Recalcitrant, naturally occurring organic compounds, variously known as humics,
fulvics, and tannics are of worldwide distribution in soil and aquatic systems.
Because of their ubiquity,
these large polyphenolic compounds are involved
in the chemical processes of nearly all surface waters (Schnitzer and Khan,
1972).
Organic ligans, which can form complexes, with metals are important
in determining the form, movement, and availability of trace metals in
natural waters
(Rashid and Leonard,
1973;
density of 4.5 x 10°
cells
+
mi7l
(K'
=
3.6 day!)
to make an
density of 5 x 10° celis + mi~! in experimental flasks.
Andelman,
1974;
Pittwell,
1974;
Jackson, 1975; Giesy, 1976). The distribution of organic carbon between
various nominal diameter fractions varies spatially and temperally.
Because
of this variability in nominal diameter of organics an understanding of the
effects of the various sized fractions must be obtained instead of total organic
ligand.
The surface waters of the Southeast are soft and contain high concentrations
of refractory organic compounds.
This coupled with the large number of present
and projected nuclear power plants and nuclear fuel production and reprocessing
facilities for the region makes crucial the understanding of Pu cycling and
fluxing processes in aquatic ecosystems.
The objective of this study was to
determine the effects of various sized organics on Pu uptake by an algal and
bacterial species.
A. hydrophila were incubated with 237put4 for 6 hr on a rotary shaker at 200
rpm.
Algal and bacterial cell densities were determined, using calibrated
phytoplankton (0.1 ml) and Petroff-Hausser counting chambers respectively.
Plutonium-237 was obtained from Oak Ridge National
Laboratory and assayed by
the Savannah River Laboratory.
Plutonium was prepared as 23?pyt4 (Table 1).
Plutonium stocks (1.1 x 1072 uci + ml)were stored in 0.5 N HNO3 in polyethylene.
Water samples were collected from Skinface Pond, Aiken, Co., South Carolina.
Particulates of nominal diameter > 0.15 um were removed and the remaining
dissolved and colloidal
constituents fractionated and concentrated by membrane
ultrafiltration (Giesy and Briese, 1977; Giesy and Paine, 1977b).
Uptake experiments were conducted in
One milliliter of
237put4
100 ml medium in
flasks.
(bacterial
The
volume of NaOH required to adjust the experimental solutions containing
organics and 237pyt4 spike had been previously determined.
Present
in experimental media at
Organics were
the concentration at which they were
found
in nature.
The resulting experimental media contained 1.1 x 10-4 yi 237 py +4
at pH 4.5.
Solutions were mixed and allowed to stand 5 min before algal or
bacterial inoculations.
Algae and bacteria were separated from experimental media by centrifugation
into a phthalate separator (Giesy and Paine, 1977b).
taining all components of
Control cultures, con-
the medium but no algal or bacterial
cells,
were
handled in the same manner as experimental cultures to evaluate contamination
in the separation procedure or Pu polymerization.
Reagent blanks, controls
and experimentals were analyzed for 237 pu using a GeLi detector
an INOTEC 4000 channel pulse height analyzer.
interfaced to
Since all
replicates
could not be centrifuged concurrently, experimental units were blocked
orthogonally over time.
Significance of treatment effects were tested using
standard analysis of variance
Axenic cultures of Scenedesmus obliquus (Turp) Kutz (strain #1592) were obtained
from the Indiana University Culture Collection.
Aeromonas hydrophila (strain
#7966) was obtained from the American Type Culture Collection.
Stock, axemic
300 ml Erlenmeyer
stock was added to AAP or AAP + 0.5% TBS
uptake) and adjusted to pH 4.5 with 1.0 N NaOH using a microburette.
The experimental design was a randomized block design.
MATERIALS AND METHODS
techniques and means separated with Student-
Newman Keubs multiple range test.
level.
Significance was tested for at the a = 0.05
s. obliguus cultures were maintained in 200 ml Algal Assay Procedure (AAP)
medium aerated with sterile air (Anon, 1971).
Stock algal cultures were checked
532
initial cell
S. obliquus and
to form complexes with many
organic Jigans such as those in soil.
(Bondietti, et al.,
periodically for bacteria contamination by plating on peptose agar, incubating
in tryptic soy broth (TSB) and microscopic examination.
Stock and experimental cultures were incubated at 24 + 2°C under 4035 lux illumination from
balanced spectrum "Growlux" fluorescent bulbs on a 16 hr light-8 hr dark
regime.
Algal inocula were taken from 10 day old S. obliquus cultures with
cell densities of 4.2 x 10° cells + ml | and relative growthrate {K' 0.68
day “).
Initial 8. obliquus cell densities were concentrated by centrifugation
to between 1 and 2 x 10° cells « mi7! in experimental flasks.
Stock A.
hydrophila cultures were maintained in AAP-tryptic soy broth (TSB) medium
(Difco). A. hydrophila inocula were drawn from 24 hr cultures with cell
533