Comparative biological tests in aquatic systems to determine the adverse effect of combinations of pollutants with several components

In tests with luminous bacteria, algae and daphnes as representatives of different trophic stages, the combination effect of heavy metals (Cd, Cr) and organic pollutants (p-chloroaniline, 1,2,3-trichlorobenzene, Na3-NTA) in aquatic ecosystems is exemplarily tested with subsequent comparison of the results with models of the combination effect. The author differentiates between the principles of action ''similar joint action'' = ''concentration addition'', ''independent action'' = ''response addition'' and ''synergistic action'' and employs mathematical models juxtaposing a ''simple similar action'', and ''independent action'' to a ''complex similar action'' and ''dependent action'', respectively, as well as the ''toxic unit model'', which translates the concentration of a substance into the corresponding toxicological efficacy. Most, but not all of the investigated binary mixtures of substances exhibited additive effects, but some of the combination effects depended on the proportions in the mixture. Further combination effects found were less-than-additive, more-than-additive (Cd/Cr) and antagonistic ones. (uWA)