Application of bioassays for the ecotoxicity assessment of contaminated soils.

The use of bioassays for soil characterization is receiving significant attention as a complementary tool to chemical analysis. Bioassays consist of direct toxicity assays of environmental samples that are transferred to the laboratory and analyzed for toxicity against selected organisms. Such soil samples contain the combination of the different pollutants present in situ and enable factors such as the bioavailability of contaminants or the interactions (synergic and antagonic) between them to be simultaneously studied.In this chapter, methods for soil toxicity assessment based in the guidelines developed by OECD for single substances are described. These methods have been adapted for their application to the assessment of complex matrices such as soils. The field sample can be tested undiluted and/or diluted with "uncontaminated" soil to create a pollution gradient. In the diluted samples, concentration/response relationships may be obtained. Toxicity assays to soil organisms include earthworms, plants, and microorganisms tests. In addition, toxicity assays with soil extracts are recommended. Assays of extracts with algae, daphnia, and fish (in vitro test using fish cell lines) are also described.