The ecotoxicity of aqueous leachates obtained from mining soils
was tested using algae and daphnia. In the algae assay, leachate from
undiluted samples of soils 2, 3 and 5 showed similar toxicity despite
differences in the concentrations of As and metals measured in these
leachates (Table 5). Algal growth is highly affected by nutrients present
in the soil solution, and nutrient concentration differences could overshadow
the toxicity of the samples. However, in the dose–response
test, results in each series were dose-dependent and more coherent
with soil concentrations than those obtained in the assaywith undiluted
soil samples. Thus, EC50 values varied in the order S2 b S3 b S4 b S5
according with the element concentration in soils (Table 6).