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(80-60) Evaluating the Environmental Risk of Contaminated Sites Through Direct Toxicity Assessment. Fernández, María*,1, Vega, Milagros1,2, Tarazona, José1, 1 Laboratory for Ecotoxicology. INIA., Madrid, Spain2 ERA Consult., Madrid, Spain ABSTRACT- A direct toxicity assessment is proposed to evaluate the environmental risk of contaminated sites. The purposes of this approach are: (1) to evaluate the risk of pollutants on soils, ground and surface waters within the site (2) to determine soil potential to affect nearby soils due to phenomena related to the transfer of pollution (3) to categorize sites attending to hazard properties of soil samples when remediation measures must be taken and (4) to detect the presence of unexpected pollutants and/or synergic effects comparing both chemical and toxicological data. Soil samples taken from contaminated sites and their leachates are analysed. Direct soil and leachates toxicity is assessed on soil and aquatic organisms respectively. Test species covering three trophic levels of soil (micro-organisms, terrestrial invertebrates and plants) and aquatic systems (algae, daphnia, fish) were selected for this study. OCDE standard methods for pure chemicals were modified to allow evaluating these complex matrixes. Successive dilutions of field samples with standard medium (soil or aquatic medium) are tested and L(E)C50 in each assay is estimated from a dose-response curve. Dilutions of soil are performed with a soil with high sand content (≥ 70%) and low organic carbon content (0.5-1.5 %). A soil with these characteristics represents a worst-case situation since adsorption of the pollutants to soil is minimum and the bioavailability is maximum. It intends to assess the potential transfer of contamination from the site. The usefulness and applicability of this methodology is presented. Key words: contaminated soils , ecotoxicological analysis, environmental risk, modified OCDE tests |
