Toxic effects of heavy metals in three worm species exposed in artificially contaminated soil substrates and contaminated field soils

The toxicity of chemicals is often determined in standardised laboratory experiments. OECD artificial soil (artisoil) is often used to determine chemical toxicity for soil organisms. This report presents exposure and effect assessments of metals for three worm species (Eisenia andrei, Enchytraeus crypticus and Enchytraeus albidus) in metal contaminated field soils. The species differ with respect to metal sensitivity and ecological niche. Field soils were sampled at geometrically increasing distances from a former zinc smelter, to mimic a concentration-effect curve. The soils were characterised for various physico-chemical parameters. The concentrations of zinc, copper, lead and cadmium were measured, and metal partitioning over solid and liquid phase was determined using total-, 0.01M-CaCl2-extractable- and pore water concentrations. Soil characteristics differed between sampling sites. Metal extractability tended to be lower in the field soils in comparison with artisoil to which metal salts were added. Exposure assessment showed that body concentrations of various metals increased less in the smelter soils than in artisoil with similar metal concentrations. Effect assessments were made by determining concentration-response curves for the dominant metal zinc alone, and for the mixtures of metals present in the soils, at similar soil pH. When expressed by total soil concentrations, toxic effects in field soils were less than in artisoil for E. andrei. For E. crypticus the opposite was found. E. albidus did not perform well in the soils, and was not used further. The predictability of effects in field soil from laboratory toxicity data improved when differences in metal extractability and joint effects of metals were taken into account. Joint effects were judged by application of the concept of relative concentration addition. It is recommended to take these factors into account when laboratory toxicity data are used to predict effects at contaminated sites or to derive soil quality criteria