Agriculture Reference
In-Depth Information
Soil Solid Phase
Soil Pore Water
Kp = f(CEC, pH, %OM,
%clay, etc.)
Other Metal Species
Adsorbed +
Complexed
Metal Species
Organometal Complexes
Free Metal Ions (Me
n+
)
BCF = f(pH, ion conc., etc.)
LC
50
= f(pH, Me
n+
, etc.)
Soil Organism
FIGURE 17.3
The processes involved in the soilÏwater partitioning approach, worked out for heavy metals
(OM = organic matter, BCF = bioconcentration factor). (After Van Gestel and Ma 1993.)
●
●
3
+
▫
▫
●
+
●
2
▫
▫ chlorophenols
Y = -1.00*
+ 4.86
r
2
= 0.93
+
●
1
+ chloroanilines
Y = -1.04*
+ 5.00
r
2
= 0.95
▫
▫
▫
▫
▫
▫
+
+
●
0
●
chlorobenzenes
Y = -1.85*
+ 7.62
r
2
= 0.98
●
●
-1
1.5 2.5 3.5 4.5 5.5
FIGURE 17.4
Relationships among the toxicity of chlorophenols, chloroanilines, and chlorobenzenes to
Eisenia andrei
and log
K
. For
Lumbricus rubellus
, the relation with chlorophenols is log LC
(
H
mol L
−
1
)
ow
50
=
−
0.72*log
K
+ 4.46
r
2
= 0.87. (After Van Gestal and Ma 1993.)
ow
aged contaminants do not have as much ecotoxicological impacts as would be expected from the
total content. For pesticides, this process is termed
. It illustrates once more that the
bioavailable fraction of the total toxicity content is of prime importance.
Some studies have described the internal transport, more speciÝcally the storage of contami-
nants, in earthworms (Eijsackers 1989) but seldom also describe the ecological consequences of
this distribution pattern. Bengtsson and Rundgren (1992) suggested that increased metal contents
in the earthworm nerve cord, for instance, might primarily inÞuence the transfer of stimuli and
consequently earthworm mobility and behavior.
bound residues
TESTING CONTAMINANT TOXICITY WITH EARTHWORMS
When it is understood how the earthworm takes up a contaminant and distributes it through its body,
the next question is what kind of effects on the earthworm will result. The concentration of contam-
inants in the earthworm reproductive organs may exert a different effect compared with their accu-
mulation in the cerebral ganglion or in special storage organs. There has been a strong trend toward
