English Abstract In this report a description is given of the (further)
development of bioassays for estimating the bioavailability of metals in
soils using earthworms (Eisenia fetida), lettuce (Lacuca sativa) and Radish
(Raphanus sativus). The bioassays can be used in unpolluted, contaminated
and cleaned-up soils. In former research soils cleaned-up by extraction
appeared to have lost structure and nutrients so that earthworms died and
plants didn't grow. A standard additive was developed which enables the
performance of the bioassays in both contaminated and cleaned-up soils
without, influencing the bioavailability of the metals. Therefore several
additives (peat, clay, sand, perlite, cow-dung and nutrient solution) in
varying quantities were tested in some contaminated and cleaned-up soils.
The influence of the additives on the survival of worms and the growth of
radish and lettuce were established. The bioassays lasted 4 weeks. A
suited standard additive for the bioassay using earthworms appeared to be: 8
vol% perlite ; 1 g cow-dung/ worm ; nutrient solution. The developed
standard additive for the bioassays using radish or lettuce consists of: 8
vol% perlite ; nutrient solution. The standard additives were tested in
contaminated and cleaned-up soils and appeared to enable survival of the
earthworms and proper growth of radish and lettuce. The additives did not
influence the bioavailability of the metals in these
soils.
