Influence of the molecular structure and exposure concentration on the uptake and elimination kinetics, bioconcentration, and biotransformation of anionic and nonionic surfactants

Abstract

In vivo experiments with fish (sole) were performed for pure homologs of linear alkylbenzene sulfonates (LAS) and alcohol ethoxylates (AEO), the most widely used anionic and nonionic surfactants. The surfactant concentration measured in the organism was higher than in the experimental water, and increased with the exposure concentration for both compounds. At the exposure levels tested the bioconcentration factors (BCF) for AEO were one order of magnitude higher than for LAS. Two linear relationships for hydrophobicity were established, one with BCF and the other with uptake rate. The influence of the exposure concentration on the uptake (k(1)) and elimination (k(2)) velocities was researched. The value obtained for k(1) for AEO was higher than for LAS, while k(2) was very similar for both compounds, indicating differences in the incorporation and but not in the depuration rate. For the first time, internal degradation products of LAS were identified and quantified in fish and water and the glucuronic conjugate of AEO was detected in an organism. The predominant biotransformation process for these compounds may be different: the results suggest a phase I biotransformation for LAS and phase II for AEO, due to their different molecular structures.