Assessment of soil contamination – a functional perspective

In many industrialized countries the use of land is impeded bysoil pollution from a variety of sources. Decisions on clean-up, management or set-aside ofcontaminated land are based on various considerations, including human health risks, butecological arguments do not have a strong position in such assessments. This paper analyses whythis should be so, and what ecotoxicology and theoretical ecology can improve on thesituation. It seems that soil assessment suffers from a fundamental weakness, which relatesto the absence of a commonly accepted framework that may act as a reference. Soilcontamination can be assessed both from a functional perspective and a structuralperspective. The relationship between structure and function in ecosystems is a fundamentalquestion of ecology which receives a lot of attention in recent literature, however, ageneral concept that may guide ecotoxicological assessments has not yet arisen. On the experimentalside, a good deal of progress has been made in the development and standardized useof terrestrial model ecosystems (TME). In such systems, usually consisting of intactsoil columns incubated in the laboratory under conditions allowing plant growth and drainageof water, a compromise is sought between field relevance and experimental manageability.A great variety of measurements can be made on such systems, including microbiologicalprocesses and activities, but also activities of the decomposer soil fauna.I propose that these TMEs can be useful instruments in ecological soil quality assessments. Inaddition a ``bioinformatics approach'' to the analysis of data obtained in TME experimentsis proposed. Soil function should be considered as a multidimensional concept and thevarious measurements can be considered as indicators, whose combined values define the``normal operating range'' of the system. Deviations from the normal operating range indicatethat the system is in a condition of stress. It is hoped that more work along this line willimprove the prospects for ecological arguments in soil quality assessment.