Biomarker measurements in Trifolium repens and Eisenia fetida to assess the toxicity of soil contaminated with landfill leachate: a microcosm study.

To assess the toxicity of a soil contaminated with landfill leachate, biomarker measurements in two species living in close contact with the soil, i.e. a plant species Trifolium repens and an animal species Eisenia fetida, were conducted. Briefly, both species were studied after simultaneous exposure conducted in microcosms. The organisms were exposed to soil supplemented with pure leachate, leachate diluted to 50%; leachate diluted to 25% and without leachate. After a 10 weeks exposure period, we observed an increase in the Olive Trail Moment in T. repens, compared to the reference, for 50% and pure leachate. The response observed appears to be dose-dependent and linear in our experimental conditions. Addition of the leachate to the reference soil induced an increase in Cd-Metallothionein-coding mRNA quantity in E. fetida. In addition, expression level of another gene implied in detoxification and coding Phytochelatin synthase was significantly induced in worms exposed to the reference soil spiked with the leachate, regardless presence of T. repens. Thus, T. repens and E. fetida can be used in a complementary manner to assess soil quality. Sensitivities of the test species yield sensitive bioassays as both species responded at low doses despite the buffering effect of the soil.