Effect of humic substances on toxicity of inorganic oxidizer bioluminescent monitoring.

The current study deals with the effect of humic substances (HS) on toxicity of solutions of a model inorganic oxidizer, potassium ferricyanide. Chemical reactions responsible for toxicity changes are under consideration. The bioluminescent system of coupled enzymatic reactions catalyzed by bacterial luciferase and oxidoreductase was used as a bioassay. General and oxidative toxicity of ferricyanide solutions were evaluated. Ability of HS to decrease or increase general and oxidative toxicity of the solutions was revealed. Two types of chemical processes are supposed to be responsible for detoxification by HS: ferricyanide-HS complex formation and acceleration of endogenous redox reactions in the bioluminescent assay system. Decrease of oxidative toxicity of ferricyanide solution was observed under incubation with HS at all concentrations of HS used. Conditions for general toxicity decrease were prior incubation of ferricyanide with HS and low HS concentrations (< 10⁻⁴g/L). Acceleration of NADH auto-oxidation under higher HS concentrations was supposed to result in a toxicity increase.