A study on As, Cu, Pb and Zn (bio)availability in an abandoned mine area (São Domingos, Portugal) using chemical and ecotoxicological tools

The aim of this study was to relate the results obtained by chemical methods, used to assess environmental (bio)availability, with the ecotoxic response and bioaccumulation of trace elements (TE) by the earthworm Eisenia fetida exposed to field-contaminated, metal-polluted soils from a sulphide mine. The extracting solution 0.5 M NH₄CH₃COO, 0.5 M CH₃COOH and 0.02 M EDTA (pH 4.7), was able to predict environmental bioavailability of TE to E. fetida. However, the toxicological bioavailability could not be predicted from the results of the chemical extractions or from the bioaccumulation results: E. fetida reproduction was higher in soils where environmental bioavailability of TE and bioaccumulation values were also higher. In this study, the toxic response of the organism seemed to be more influenced by the overall nutritional status of the soil (e.g. pH, organic matter, plant nutrient availability and cation exchange capacity) than by its TE contamination. In the case of anthropogenic multi-contaminated sites, the different soil characteristics exert an important and confounding influence in the toxic response and the relationship between different bioavailable fractions cannot be easily established, emphasising the need to combine results from chemical methods with those from bioassays when evaluating the bioavailability of TE in these soils.