In summary, a notable difference between soils at nearby sites and
soils from intermediate and distant siteswas observed only in the earthwormtoxicity
test results. In the rest of the assays, the differences were
not as evident. Thus, all of the soils affected plant growth and microorganism
activity. Moreover, soil leachates showed transference of contaminants
from soil to leachate at levels which were toxic to algae and
D. magna, except soil 4, which was not toxic to daphnia. This fact indicates
that the soils have the capability to contaminate nearby courses of
ground and surface water via lixiviation of contaminants. Furthermore,
analysis of waters on the site indicated that even streams sited farthest
from the mine were toxic to one of the tested organisms. Nevertheless,
according to Spanish regulations (Ministerio de Medio Ambiente, 2005),
the toxicity of the soils and their leachates was lower than the threshold
established to declare a soil as contaminated (i.e., EC50 b 1% test soil/
total soil).