Abstract :
The Netherlands Stimulation program on System-oriented Ecotoxicological Research
focused on three study areas, including two floodplains and a peaty grassland. All three
areas were polluted with metals, with total soil concentrations often exceeding Dutch
Intervention Values. The floodplain areas showed a homogeneous distribution of metal
pollution, while pollution in the peaty area was more heterogeneous. This study aimed at
establishing possible general trends in metal bioavailability by combining results obtained
at the three different study sites. Available metal concentrations, measured as pore water or
0.01 M CaCl2 extractable concentrations in soil, were lowest in the floodplain soils, probably
due to the high pH (>7.0) and high organic matter (8–30%) and clay contents (13–42%). In the
peaty soil, having a lower soil pH (4.5–6.5) but higher organic matter contents (38–60%), in
some but not all samples Cu concentrations in pore water and Cu and Pb concentrations in
0.01 CaCl2 extracts were higher than in non-polluted reference areas. Plants in the floodplain
areas had only low metal concentrations in their leaves, but soil invertebrates and small
mammals did contain elevated concentrations in their body. Cd showed high levels in
earthworms, snails and small mammals, while also Cu levels were sometimes increased in
earthworms, millipedes and small mammals from the floodplain areas. Earthworms from
the peaty area contained increased levels of Cu and Pb. These results suggest that metal
bioavailability cannot be predicted from available concentrations in pore water or 0.01 M
CaCl2 soil extracts, but requires measurement of biota and more insight into the
biodynamics of metal uptake.
