Chemistry Reference
In-Depth Information
Intercept
−
Intercept
M
2
M
2
Log
ρ=
(1.8)
M
2
Slope
Common
Pr
obit
(
P
M
1 +
M
2
) =
Intercept
M
1
+
Slope
Common
Log
(
C
M
1
+ ρ
M
2
C
M
2
)
(1.9)
The relative potency, ρ
M
2
, functions here much like a currency exchange rate
functions. It converts concentration of one metal into the equivalent concentration of
the other. If one were interested in detecting trends away from perfect similar joint
action and toward independent action, the absolute difference between estimated
slopes from Equations (1.6) and (1.7), i.e., |
Slope
M
1
−
Slope
M
2
| could be used as a
metric of deviation from similar mode of action.
Newman and Clements (2008) reanalyzed the binary metal mixture effect
on bacterial bioluminescence data of Ownby and Newman (2003) using these
models (Figure 1.8). A common slope was anticipated if two mixed metals were
3
MnNi
CoNi
MnZn
2
CuZn
CoMn
NiZn
CuMn
CuNi
CoZn
1
CuCo
0
3
CuMn
CuCo
CuNi
CuZn
2
1
MnZn
NiZn
MnNi
CoZn
CoNi
CoMn
0
0
0.01
0.02
0.03
Absolute Dierence in σ
p
FIGURE 1.8
Deviations from perfect independent (top panel) and perfect similar (bottom
panel) action for binary mixtures of metals are predictable from differences in paired metal
softnesses. Specific paired metals in mixtures are indicated next to each data point, e.g.,
MnNi = a binary mixture of Mn
2+
and Ni
2+
. This figure is Figure 9.8 from Newman, M.C., and
W.H. Clements. 2008.
Ecotoxicology: A Comprehensive Treatment
. Boca Raton, FL: CRC Press.
