UNDERSTANDING VARIATION IN PARTITION COEFFICIENT, Kd ...

Element
Table 5.2. Concentrations of contaminants used in the aqueous
species distribution calculations.
Total Conc.
(µg/l)
Reference for Concentration of Contaminant
Used in Aqueous Speciation Calculations
Cd 1.0 Hem (1985, p. 142) lists this value as a median concentration of dissolved
cadmium based on the reconnaissance study of Duram et al. (1971) of metal
concentrations in surface waters in the United States.
Cs -- Distribution of aqueous species was not modeled, because mobility of dissolved
cesium is not significantly affected by complexation (see Section 5.3).
Cr 1.4 Hem (1985, p. 138) lists this value as an average concentration estimated by
Kharkar et al. (1968) for chromium in river waters.
Pb 1.0 Hem (1985, p. 144) lists this value as an average concentration estimated by
Duram et al. (1971) for lead in surface-water samples from north- and southeastern
sections of the United States.
Pu 3.2 x 10 -7 This concentration is based on the maximum activity of 239,240 Pu measured by
Simpson et al. (1984) in 33 water samples taken from the highly alkaline Mono
Lake in California.
Rn -- Aqueous speciation was not calculated, because radon migrates as a dissolved gas
and is not affected by complexation (see Section 5.7).
Sr 110 Hem (1985, p. 135) lists this value as the median concentration of strontium for
larger United States public water supplies based on analyses reported by Skougstad
and Horr (1963).
Th 1.0 Hem (1985, p. 150) gives 0.01 to 1 µg/l as the range expected for thorium
concentrations in fresh waters.
3 H -- Aqueous speciation was not calculated, because tritium ( 3 H) migrates as tritiated
U 0.1 and
1,000
water.
Because dissolved hexavalent uranium can exist as polynuclear hydroxyl
complexes, the hydrolysis of uranium under oxic conditions is therefore dependent
on the concentration of total dissolved uranium. To demonstrate this aspect of
uranium chemistry, 2 concentrations (0.1 and 1,000 µg/l) of total dissolved
uranium were used to model the species distributions. Hem (1985, p. 148) gives
0.1 to 10 µg/l as the range for dissolved uranium in most natural waters. For
waters associated with uranium ore deposits, Hem states that the uranium
concentrations may be greater than 1,000 µg/l.
5.4