Bioavailability of the fungicides carbendazim and iprodione in soil, alone and in mixtures

Measures to protect soil ecosystems require research data on the effects of toxic chemicals on soil organisms. In the co-operative MIXTOX project, the effect of mixtures of toxic chemicals on some animal species in soil is studied. Mutual interactionsin the behaviour of toxic chemicals in soil may be expected to affect the exposure of the organisms to the mixtures. The fungicides carbendazim and iprodione compete in the adsorption on soils, which increases their bio-availability in mixtures. The transformation of the fungicides is slowed down in mixtures, which also increases their bio-availability. The exposure of soil animals to the fungicides in soil solution is much higher in the mixtures than when a fungicide alone is present in soil. The inclusion of copper in the mixture has little additional effect on the bio-availability of the fungicides in pore water. Chemical analyses in the framework of the dose-response experiments of the research partners serve as a check on the dose and on unexpected losses of the fungicides.