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Surfactants (surfactants) are found in large quantities in industrial and domestic wastewater. Along with them, there are also oil products. In a certain concentration, they have a depressing effect on aquatic organisms. In recent decades, along with physicochemical methods for assessing the quality of water bodies, biodiagnostics - biotesting and bioindication - has been actively used. Depending on a number of factors, the effect of the combined action of substances on the test organism can be additive, antagonistic, or synergistic. Biotesting in combination with a multifactorial experiment makes it possible to identify the final effect and the nature of the combined toxic effect of pollutants. The study investigated the isolated and combined effect of oil and some surfactants on the duckweed. The criterion for the influence of pollutants was the growth dynamics of fronds of this aquatic plant. During biotesting, the most widely used anionic detergent, sodium dodecyl sulfate (SDS), was used. In addition, we studied the effect of the nonionic surfactant Tween-85 on this test object. The toxicity of the effect of certain substances on the duckweed was assessed, and this made it possible to calculate the concentrations that cause a certain toxic effect. Then a full two-factor experiment was carried out with the combined action of two pairs of substances: oil - SDS, oil - Tween-85. Regression equations for two pairs of substances are compiled. The action of the investigated compounds is interdependent. The nature of the combined toxic effect turned out to be less than additive.

The efficiency of vermipreparations has been investigated with the help of the test-reactions on various invertebrate organisms, plants and microorganisms. The principal possibility of the use of biotest on the basis of yeast, fungi, algae, water and ground-based plants, sponges, protozoan, small crustaceans, oligochaetes for an estimation of biological activity of vermipreparations and in further and for definition of quality, selection of dose of medicinal complex preparations is shown.