First hydrocarbon soil and water sampling in Brittany, France: the story behind

Located in Brittany, western France, the Ploufragan site housed a soap factory in the 20^th century. A soap, le Brochin, that made the hands of workers and mechanics white was invented there in 1919. In 1948, the Renaud-Lucienne bought the factory and was authorised to produce the soap from 1951. This meant the site was used for caustic and paint manufacturing activity and also used motor oil regeneration activity. However, gradually, the activity declined and the company closed in 1994.

For nearly thirty years, the buildings of the former soap factory were derelict and the site was recognized as abandoned by the Ministry of the Environment in 1996. Due to the pollution on the site, the French government has charged the ADEME (Agency for the Environment and Energy Management) with ensuring its decontamination. The buildings of the factory were demolished in 2017 and the site was fully examined for contamination in autumn 2021. The findings were alarming as the pollution levels of the soil and groundwater reached very high values of hydrocarbon contamination.

Interest of the society and MIBIREM research

Through ADEME, the partners of the Laboratoire Interdisciplinaire des Environnements Continentaux (LIEC) in Nancy, France, which is part of the CNRS (Centre National de la Recherche Scientifique) became aware of this site. The site is also of interest of the research to the MIBIREM project. “We are looking for sites contaminated with hydrocarbons to carry out our research, which is aimed at developing a bioremediation process by identifying microorganisms capable of breaking down the hydrocarbons”- says Dr. Aurélie Cébron, research director at the CNRS.

Experience on site Ploufragan

LIEC researchers went to take soil and groundwater samples in early April 2023. Led by Dr. Aurélie Cébron, alongside Christophe Gauthier and Audrey Vauloup – both assistant engineers at the CNRS, the researchers spent two days in the field sampling the water from piezometers (wells installed in the ground to access the water table) and the soil from five sub-sites about ten meters apart. Water sampling was facilitated by Erwan Goulian of DND Biotech – a partner in the MIBIREM consortium. For the soil samples, a mechanical drill was used to sample at depths of 0 to 2m and then 2 to 4m.

Dr. Aurélie Cébron further explains: “the pollution was there, no doubt about it, on the surface of the water in the piezometers we observed a layer of almost 40cm of floating (pure hydrocarbons), like a pool of oil floating on the surface of the water table. The soil cores were literally dripping with a black viscous liquid: hydrocarbons. The smell of hydrocarbons also accompanied us during these two days: we had the impression of being in a service station.”

What happens next?

The samples were collected to measure the contaminants present and assess their chemical characteristics. The microbial diversity (mainly bacteria) present in these samples will be determined using molecular tools: after extracting the DNA and sequencing it, the researchers will be able to see whether certain microorganisms are found in greater numbers in the most polluted areas. The researchers will also evaluate the biodegradation of hydrocarbons by setting up microcosms in the laboratory; furthermore, they will try to isolate bacterial consortia capable of efficiently degrading hydrocarbons for the rest of the project.

This site is only one of fifteen in total that will be sampled as part of the MIBIREM project, and hydrocarbons are only one type of contaminant studied among the three considered in the project, the others being cyanides and hexachlorocyclohexane (HCH).