et al., 2010), so that a certain fraction of arsenic can be mobilized by
changes in the geochemical conditions.
3.4. Ecotoxicity data
Toxicity data on soil and aquatic organisms obtained in the assessment
of undiluted samples of soils using the MS-3 microcosm system
are shown in Table 5. Data were expressed as a percentage of inhibition
with respect to control soil. As expected, the toxic effects varied substantially
depending on soil and test species. In the earthworm assay,
only the soils nearest to the mine (S2 and S3) caused earthworm
mortality, whereas S4 and S5 did not show significant differences with
control soil. However, soil 5, which presented the lowest element concentrations,
showed sublethal effects on this organism with a decrease
in earthworm weight of 50±4%. All soils were toxic to the three tested
species of plants, but effects varied with the plant species and the endpoint
measured (i.e., emergence of seedling or growth). Samples 2 and
3 presented the greatest adverse effects on R. sativus germination and
weight of T. aestivum and V. sativa. However, in other tests, effects on
plants were independent of the concentration of As and metals in the
soil. The effects of soil S5 on plants were pronounced, despite the low