Combination effects of metals in soil - acute toxicity test of bacteria with the leucine incorporation method

Sammanfattning: Within the field of ecotoxicology there is a concept called combination effects. There are two different approaches to combination effects, independent action (IA) and concentration addition (CA). The common assumption in both approaches is that there are no interactions between the substances within the mixture. These approaches are used for predicting the toxicity of whole mixtures and also to examine mixtures to detect potential synergistic or antagonistic effects (interactions). If a mixture does not show any synergistic or antagonistic effects, it is labelled as strict additive. In this study the CA concept was used for assessing the combination effects between the metals copper-­‐zinc and copper-­‐mercury in soils with different organic matter content, by measuring the bacterial growth with the leucine incorporation method. The results showed no synergistic or antagonistic effect between copper-­‐zinc, independent of soil type. The same result was obtained from the copper-­‐mercury experiment, which was conducted only in one soil. There was, however, a clear relationship between the toxicity of the metals in the soil (estimated as EC50) and the organic matter content. The leucine incorporation method was also compared with respiration, a more commonly used measurement within ecotoxicology.