Low-Cost Microbiotests for Toxicity Monitoring during Bioremediation of Contaminated Soils

Abstract

This paper addresses in the first place the need to apply toxicity tests with batteries of species from different trophic levels for an (ecologically meaningful) determination of the toxic hazard of contaminated soils. Furthermore, "direct contact" tests must be performed as well as assays on pore waters, leachates or percolates. Most toxicity tests available to date are dependent on the continuous maintenance of live stocks and their application is restricted to a limited number of highly specialized laboratories. Repeated toxicity testing in bioremediation programs is very expensive and there is an urgent need for cost-effective alternatives. Microbiotests with micro-algae, protozoans and various invertebrate test species have been developed over the last few years, which depart from dormant or immobilized stages of the test biota and are hence independent of the burden of continuous stock cultur-ing/maintenance. The sensitivity of these new assays (named Toxkits) has been compared to that of "conventional" aquatic and direct-contact tests in a variety of studies on pure chemicals as well as on natural samples, and found to be equivalent, if not better. Recently a direct contact microbiotest, the Ostracodtoxkit, was developed for sediments, which now also seems to be applicable, to contaminated soils. besides numerous applications in aquatic toxicology, the low-cost and user-friendly Toxkit microbiotests now also appear to be an attractive tool for routine toxicity monitoring and/or follow-up of detoxication in bioremediation programs of contaminated soils.