UNDERSTANDING VARIATION IN PARTITION COEFFICIENT, Kd ...

Cadmium
K d
Table C.2. Correlation coefficients (r) of the cadmium K d data set for soils.
Cadmium
K d
log (K d) 0.69 1
1
log (K d) Clay
Content
Clay Conc. -0.04 0.03 1
pH 0.50 0.75 0.06 1
CEC 0.40 0.41 0.62 0.35 1
C.4
pH CEC TOC Cd Conc.
TOC 0.20 0.06 0.13 -0.39 0.27 1
Cd Conc. -0.02 -0.10 -0.39 0.22 -0.03 -0.09 1
Fe Oxide
Conc.
0.18 0.11 -0.06 0.16 0.19 0.18 0.01
C.2.2 Cadmium K d Values as a Function of pH
The cadmium K d values plotted as a function of pH are presented in Figure C.1. A large amount
of scatter exists in these data. At any given pH, the range of K d values may vary by 2 orders of
magnitude. This is not entirely satisfactory, but as explained above, using more than 1 variable to
help categorize the cadmium K d values was not fruitful.
The look-up table (Table C.3) for cadmium K d values was categorized by pH. The regression
equation for the line presented in Figure C.1 is:
Cd K d = -0.54 + 0.45(pH). (C.1)
The minimum and maximum values were estimated based on the scatter of data points observed in
Figure C.1.