Joint toxicity of linear alkylbenzene Sulfonates and pyrene on Folsomia fimetaria

Surfactants may enhance the biodegradation of hydrophobic substances in soils. This has partly been attributed to an increase in the bioavailability, brought about by the presence of surfactants. The aim of this study was to examine the ecotoxicological effects of the detergent linear alkylbenzene sulfonate (LAS) and the polycyclic aromatic hydrocarbon pyrene, alone and in combination, using the survival and reproduction of the collembolan Folsomia fimetaria as endpoints. The EC50 and EC10 were 803 and 161 mg kg(-1) for LAS, and 23 and 15 mg kg(-1) for pyrene. If LAS was able to increase the bioavailability of pyrene to springtails, it was expected that the combined effect of the two substances would exceed the effect found for each of the compounds tested separately. However, the results showed no effect of LAS on the toxicity of pyrene in the concentration range tested (1-750 mg LAS kg(-1) dry weight). Both the toxic unit concept and the isobologram method indicated that an additive approach would be the most useful when assessing the risk of these two compounds. (C) 2002 Elsevier Science (USA).