Effect of clay and organic matter type on the ecotoxicity of zinc and cadmium to the potworm Enchytraeus albidus

Clay and organic matter are considered as important parameters influencing bioavailability and ecotoxicity of metals in soils. As there exists a large variation in the type of clay and organic matter in field soils, the quant ity of these variables alone may not be good indicators of metal bioavailab ility. To test this hypothesis, toxicity experiments with the potworm Enchy traeus albidus were conducted in artificial soils with three types of clay and seven types of organic matter, while the soil pH was kept constant. The 14d LC50 of zinc and cadmium varied from 83.0 to 1140 mg Zn/kg D.W. and fr om 55.2 to 704 mg Cd/kg D.W., respectively, depending on the type of clay a nd organic matter that were used. Simultaneous measurements of the cation e xchange capacity showed that this soil parameter is a better indicator of t he bioavailability as it takes into account the type of clay and organic ma tter as well as other adsorption phases such as metal oxyhydroxides. (C) 20 01 Elsevier Science Ltd. All rights reserved.