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Table 6
Ecotoxicity results of bioluminescence emitted by the bacterial strains.
Sample Bacterial strain
ZntLux a Arslux a Merlux a pBtaclux b
(a) Induction factor and inhibition rate calculated from the bioluminescence
S 1 4.8 99.6 9.9 6.5
S 2 0.9 324.9 0.8 –
S 3 4.0 1.2 12.9 –
S 4 1.4 0.8 0.9 –
S 5 0.7 0.9 1.0 –
S 6 0.6 0.8 0.9 –
S 7 5.4 79.8 138.1 18.4
S 8 1.2 0.9 0.9 –
S 9 1.3 2.1 0.8 –
S 10 1.2 1.2 0.8 –
Sample Chemical analysis Biological analysis (prediction with decision trees)
Cd As Cu Hg Cd As Cu Hg
(b) Comparison between MTE leached water­soluble concentrations and range “biologically” detected by the bacterial strains (unit: M)
S 1 4.5 × 10 −7 3.7 × 10 −7 2.3 × 10 −6 – 10 −8 to 10 −7 10 −6 to 10 −5 – –
S 2 1.8 × 10 −7 29.7 × 10 −7 1.1 × 10 −6 – – 10 −6 to 10 −5 – –
S 3 9.1 × 10 −7 3.6 × 10 −7 1.8 × 10 −6 – 10 −8 to 10 −7 < 10 −6 – –
S 7 48.9 × 10 −7 3.3 × 10 −7 0.8 × 10 −6 – 10 −8 to 10 −7 10 −6 to 10 −5 10 −4 to 10 −5 10 −9 to 10 −5
a IF: induction factor.
b Inhibition rate (%).
pollution on ecosystems seems therefore particularly appropriate
in this type of study.
4.2. Relevance of ecotoxicity tests for risk assessment posed by
landfilling
The D. magna ecotoxicity test was more sensitive to MTE impact
than the Microtox ® test. But, unlike tests on the different bacterial
strains, they do not both provide information on MTE quantification.
Ecotoxicity differences were measured for some samples,
especially S 2 and S 8 . These differences can be firstly explained by
water flea sensitivity. Detection capabilities of the ecotoxicity of
the leachate are actually dependent on the test used [62,63] and it
has been already shown that V. fischeri was generally less sensitive
than D. magna [10,64]. Instead of these tests, experiments by using
bacterial strains allowed to determine and quantify the element
which was potentially bioavailable and/or toxic for bacteria [50].
Then, response in ecotoxicity tests was not always directly correlated
with total or water­soluble concentrations [65]. These results
are in agreement with data previously obtained by Plaza et al. [14]
concerning the influence of pH and CEC on MTE behaviour in soils.
Results of this study have shown that this new bioassay enables
the screening of samples in terms of environmental risk during
remediation process [24]. However, the drawback of the lack of
specificity of one strain and the effect of a mixture of MTE (synergistic
or antagonistic effects) could be overcome by using a panel of
bacterial strains coupled with a predictive model [24]. Due to the
lack of specific bacteria for lead, the introduction of other strains
induced by lead like Rastonia Metallidurans AE 1433 [66] could
improve the interpretation of the data.
Table 7
Hazard classification, adapted from [10,60].
Sample Score Class a MCW b W c PW d
D. magna Microtox Zntlux Arslux Merlux pBtaclux
S 1 4 3 1 3 2 2 V 4 2.5 62.5
S 2 4 0 0 4 0 0 V 4 1.3 33.3
S 3 4 1 1 1 2 0 V 4 1.5 37.5
S 4 2 1 1 0 0 0 III 2 0.7 33.3
S 5 0 0 0 0 1 0 II 1 0.2 16.7
S 6 3 0 0 0 0 0 IV 3 0.5 16.7
S 7 4 3 2 3 4 2 V 4 3.0 75.0
S 8 4 0 1 0 0 0 V 4 0.8 20.8
S 9 2 0 1 1 0 0 III 2 0.7 33.3
S 10 2 0 1 1 0 0 III 2 0.7 33.3
a
Class
MCW
I No acute toxicity PE < 20% IR/InR < 1 0
II Slight acute toxicity 20% ≤ PE < 50% 1 ≤ IR/InR < 5 1
III Acute toxicity 50% ≤ PE < 75% 5 ≤ IR/InR < 50 2
IV High acute toxicity 75% ≤ PE < 100% 50 ≤ IR/InR < 100 3
V Very high acute toxicity PE ≥ 100% IR/InR ≥ 100 4
b MCW: maximum class weight score.
c W: class weight score.
d PW: class weight score in percent.