Environmental fate and effects of foaming agents containing sodium lauryl ether sulphate in soil debris from mechanized tunneling

A wide use of foaming agents as lubricants is required in mechanized tunneling. Their main component, the anionic surfactant sodium lauryl ether sulphate (SLES), can remain in residual concentrations in soil debris, influencing their potential reuse as by-product. This study aimed at evaluating the environmental fate and effects of a foaming product used for conditioning soils collected from real excavation sites, in the presence/absence of an anti-clogging polymer, both containing SLES. Soil microcosm experiments were set-up and incubated for 28 days. Over time, soils and their water extracts (elutriates) were collected to perform both ecotoxicological tests (Vibrio fischeri, Lepidiumsativum, Eisenia foetida, Hetereocypris incongruens, Danio rerio) and SLES analysis. The results showed that, just after conditioning, SLES did not exert any hazardous effect on the organisms tested except for the bacterium V. fischeri, which was the most sensitive to its presence. However, from day seven the toxic effect on the bacterium was never observed thanks to the SLES decrease in the elutriates (<2 mg/L). SLES degraded in soils (half-lives from 9 to 25 days) with higher disappearance rates corresponding to higher values of microbial abundances. This study highlights the importance of site-specific studies for assessing the environmental reuse of spoil materials.