A Review of the Microtox® Toxicity Test System for Assessing the Toxicity of Sediments and Soils

Use of Microtox for screening sediment or soil samples from contaminated systems either alone or in combination with a battery of other tests is supported by an ever-increasing number of comparative studies demonstrating its utility, sensitivity, rapidity and affordability. Organic solvent extracts and direct solidphase material provide an assessment of the potential toxicity exerted by both dissolved and bound contaminants. In contrast, tests utilizing pore water or elutriates may be limited to assessing the contribution of dissolved contaminants only. Each approach is limited in the scope of its applications. The apparent toxicity of elutriates can be a function of extraction solvent and overall procedure. The apparent toxicity of solid-phase samples is influenced by sample color and composition — more specifically, the ratio of clay to silt. However, in general, the results obtained through in laboratory testing with the Microtox test system are often consistent with the results of both sediment invertebrate in laboratory toxicity tests and macroinvertebrate field surveys. There is also evidence that toxicity assessments obtained with the Microtox test system are related to analytically derived concentrations of certain classes of contaminants.