Predicting toxicity of aromatic ternary mixtures to algae

Abstract

Aquatic ecosystems are often polluted with more than one type of contaminant, and information on the combined toxic effects of mixed pollutants on aquatic organisms is scarce at present. Acute toxicity of aromatic compounds and their ternary mixtures to the alga (Scenedesmus obliquus) was determined by the algae growth inhibition test. The median effective concentration (EC 50) value for a single aromatic compound and EC 50mix values for mixtures were obtained. the logarithm of n-octanol/water partition coefficient (logP mix) and the frontier orbital energy gap (ΔE mix) for mixtures were calculated. Based on the quantitative structure-activity relationship model for single chemical toxicity log(1/EC 50)=0.426logP−1.150ΔE+12.61 (n=15, R 2=0.917 and Q 2=0.878), the following two-descriptor model was developed for the ternary mixture toxicity of aromatic compounds: log(1/EC 50mix)=0.682logP mix−0.367ΔE mix+4.971 (n=44, R 2=0.869 and Q 2=0.843). This model can be used to predict the combined toxicity of mixtures containing toxicants with different mechanisms of action.