APPLICATION OF BIOASSAYS FOR SITE SPECIFIC RISK ASSESSMENT: Evaluation of Toxic Effects Exhibited by Organic Pollutants Present in Soil

摘要

In general, bioassays deliver important information on toxic effects exhibited by contaminated soil. They consider site specific conditions, such as the influence of the matrix on bioavailability, and chemical interactions if multiple contamination is present. However, as results cannot be linked to concentrations of single pollutants, the calculation of toxicity levels (LC50, NOEC, etc.) for particular contaminants is not possible but needed for risk characterization (linking exposure to effects). It might be appropriate to calculate, for instance, an LC50 for an effluent of an industrial plant which emits into a river. Based on flow rates, the exposure to organisms present in the river can be modelled and the risk may be calculated. However, further research is necessary to develop similar applications for contaminated soil. Moreover, at most sites, pollutants are heterogeneously distributed in soil. Therefore, greater number of samples has to be taken to meet statistical needs. This may increase the cost for site characterization dramatically, in particular, when applying test batteries for each sample. Nevertheless, when selecting appropriate test organisms, bioassays provide useful data to screen for hazards present and to establish a priority ranking for contaminated sites.