Ecotoxicological assessment of soils. Bioavailability from an ecotoxicological point of view

It is the aim of the Federal Soil Protection Act (Bundes-Bodenschutzgesetz, BBodSchG 1998) to protect or to restore the functions of the soil in a sustainable way. According to the BBodSchG (1998) the natural (ecological) functions of the soil include: - the basis for life and habitat, for human beings, animals, plants and soil organisms (in one word: the biospherical function), - as part of natural systems, especially as part of water and nutrient cycles, - as a medium for decomposition, balance and restoration as a result of its filtering, buffering and substance-converting properties, especially for groundwater protection. According to the BBodSchG Paragraph 2, p. 3, a harmful soil change is an impairment of the soil functions that can lead to increased risk, applicable disadvantage or a considerable nuisance for a single person or for the general public. The existence and extent of a contaminant, or the combination of different contaminants, in a soil leads to an impairment of soil functions. This depends on the type of substance or the combination of substances respectively (substance-specific properties) as well as on its concentration, soil properties and the respective use of soil. The derivation of the precautionary, trigger and action values indicated in the Soil Protection Ordinance (Bundesbodenschutzverordnung, BBodSchV) is substance-based, as commonly performed in toxicology. Presently soil values have been derived only for some chosen environmentally relevant contaminants concerning the potential risk of target protection (e.g. human health, groundwater) taking into consideration defined transfer pathways. Principally analogous substances and values can be derived for the transfer pathway soil --> soil organisms. Results for some contaminants have already been published (Dreher et al. 2000). During the assessment of a soil exceedence values concerning a specific soil use or reuse of soil can be checked analytically applying standardized methods