Assaying the effects of chemical ameliorants with earthworms and plants exposed to a heavily polluted metalliferous soil
2002
Morgan, A.J. ((Cardiff University (Royaume Uni). Cardiff School of Biosciences)) | Evans, A.J.M. | Winters, C. | Gane, M. | Davies, M.S.
The study examined the effects of chemical ameliorant additions (1 per cent montmorillonite, 1 per cent hydroxylapatite, or 1 per cent ferrous oxide) on the availability of cadmium (Cd), copper (Cu), lead (Pb) and zinc (Zn) to the earthworm, Lumbricus rubellus, exposed for 4 weeks to a circumneutral heavily polluted soil (Cd = 220 microg/g, Cu = 35 microg/g, Pb = 6070 microg/g, Zn = 124500 microg/g) in 1:0-1:3 dilutions with a clean soil, under laboratory conditions. Soil type (i.e. the dilution series) had a strong influence on the 1 M ammonium acetate extractable metal fractions in soil and on worm-tissue concentrations of Cd, Pb and Zn. Soil treatments (i.e. amelioration) significantly reduced only the soil Zn extractable fraction. Zn concentrations in worms tended to be lower in amended soils. A second experiment, involving curly cress (Lepidium sativum), grown either directly in the serial soil dilutions with 5 per cent ameliorant additions or in the water-extractable fractions of the soils, indicated that root growth is a more sensitive endpoint of metal availability than chlorophyll assays. It was concluded that chemical immobilization of metals is probably most effective in soils with low to moderate degrees of metal pollution, an integrated suite of bioassays incorporating different, ecologically relevant, taxa is to be recommended for monitoring metal bioavailabilities and biological effects
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