Environmental Engineering Reference
In-Depth Information
When the samples were filtrated prior to analysis, all contaminants absorbed or
adsorbed by the algae were removed from the sample. Even though there were large
differences between the toxic effects of the samples, the samples were in general
toxic to the test organisms and treatment by adding aluminum was relevant.
The EC50 values obtained by the algal test (72 h exposure) and standard deviation
for the different aliquots from the sample III and IV, are shown in Fig. 2 .
EC50 values above 100% dilution were calculated by extrapolation of the dose-
respond curve and not by concentration of the samples, for example by evaporation.
As shown in Fig. 2 the toxic effect of the stormwater runoff decreased with increasing
aluminum concentration up to 7 mg Al Al/L. Above 7 mg Al/L the toxic effect increased
with increasing aluminum concentration. In the aliquots added 30 and 40 mg Al
Al/L, the toxic effect was greater than for the pure sample. That is, aluminum
reduced the toxic effect of the stormwater runoff up to a certain level. Above this
level the aluminum itself became the source of the toxic effect. In Fig. 3 , EC10
600
600
500
500
400
400
300
300
200
200
100
100
0
0
0
10 0 0 0
0246810
Aluminum concentration [mg Al L -1 ]
Aluminum concentration [mg Al L -1 ]
Fig. 2 EC 50 values and standard deviations for the aliquots from sample III ( left graph ) and
sample IV ( right graph ) measured with the algal test. A high EC 50 -value is equivalent to a low
toxic effect
100
100
80
80
60
60
40
40
20
20
0
0
02468 0
0
10 0 0 0
Aluminum concentration [mg Al L -1 ]
Aluminum concentration [mg Al L -1 ]
Fig. 3 EC 10 values and standard deviations for the aliquots from sample III ( left graph ) and sample
IV ( right graph ) according to the algal test. The higher the EC 10 -values, the lower the toxic effect
 
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