Transport of Chromium-51  in an
Organically Polluted Environment
LARRY W. CANTER, Assistant Professor
Department of Civil Engineering
Tulane University
New Orleans, Louisiana
EARNEST F. GLOYNA, Professor
Department of Civil Engineering
University of Texas at Austin
Austin, Texas
Many factors affect the transport of radioactive waste materials by streams.
The factor examined in this research was the influence of chemical oxidation
states and their associated ionic species on radionuclide transport (1). The radionuclide chosen for this research was 51cr, a transition metal which exists in
aqueous systems in either a cationic form or an anionic form, depending on the
oxidation state. The two main oxidation states of 51cr are trivalent (III) and hex-
avalent (VI). Trivalent 51Cr normally occurs in streams in a cationic hydrous
form, Cr (OH)+2, and hexavalent 51cr normally occurs in an anionic chromate
form, CrOj.
In order to examine the selected transport factor, the research was divided
into four major studies: 51cr oxidation state changes in natural water, the affinity of 51cr for clay and sediment, the uptake of S^Cr in aquaria systems, and the
transport of SlCr in a model river under both natural and imposed conditions.
These studies were conducted at The University of Texas at Austin.
This paper is a report of a study involving the transport of 51cr in a model
river subjected to an imposed condition of organic pollution. The specific objectives for this study were to determine: 1) the effect of an organically-polluted
environment on the transport of 51cr (VI) in a model river system under conditions of steady flow, both during and after the continuous release of 51cr (VI) for
a short period of time; 2) the effect of an organically-polluted environment on
the changes of the oxidation state of the 5lCr (VI) in the water phases of a model
river system under conditions of steady flow, both during and after the continuous
release of °^Cr (VI) for a short period of time.
LITERATURE EVALUATION
Chromium chemistry can become quite involved since chromium is a transition metal and very chemically "active. " Transition metals have the ability to
from complex compounds and chromium is no exception. There are more than
2, 000 known compounds of chromium in the class known as complex compounds
(2).
Chromium can exhibit oxidation states ranging from (-II) to (VI). The most
stable oxidation states of chromium under environmental conditions are the trivalent (III) and hexavalent (VI) states. In general, the chemical reactivity of
51Cr (III) is greater than that for °TCr (VI) (3). A radiochemical procedure is
available for separating the two oxidation states when they are present in the same
solution (4).
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