A new experiment to assess the impact of groundwater table level variations on petroleum hydrocarbon pollutants remobilization (LNAPL) in the climate change context

Amélie Cavelan (1) , Pierre Faure (1) , Fabrice Golfier (2) , Anne-Julie Tinet (2) , Constantin Oltean (2) , Stéfan Colombano (3) , Hossein Davarzani (3) , Jacques Deparis (3) , Catherine Lorgeoux (2) , Noële Enjelvin (4, 5)

1 LIEC - Laboratoire Interdisciplinaire des Environnements Continentaux
2 GeoRessources
3 BRGM - Bureau de Recherches Géologiques et Minières (BRGM)
4 LSE - Laboratoire Sols et Environnement
5 GISFI - Groupement d'Intérêt Scientifique sur les Friches Industrielles

Light Non-Aqueous Phase Liquids (LNAPLs) are an important source of soil contamination. When they infiltrate through the unsaturated zone, part of the LNAPLs remains trapped by capillary forces. The others accumulate above the top of the water table, forming a floating ‘free’ phase able to generate a long-term dissolved LNAPL plume. Seasonal variations in the groundwater level lead to significant vertical dispersion of these contaminants at the capillary fringe, favoring their release into the air and water. The IPCC predicts an intensification of these groundwater level variations over the next century in response to variations in rainfall intensity and frequency (related to climate change) and the increasing use of water resources. This context may strongly impact the LNAPL remobilization. It is, therefore, essential to better understand the impact of these groundwater level fluctuations on the remobilization processes of these hydrocarbon contaminants. To this end, an original experimental system combining indirect geophysical (electrical conductivity), in situ physical-chemical (pH, Eh, temperature), and geochemical measurements was developed at the GISFI station (Homécourt, France). This device allows the assessment and the comparison of nature and the amount of LNAPLs release into the atmosphere and water from a contaminated soil during two groundwater level fluctuations scenarios: one corresponding to the ‘actual’ rainfall pattern based on regional climate records; the other based on the most extreme IPCC scenario. This study will be conducted at different scales (laboratory decametric columns and 2 m3 lysimeters) and on soils of different geological complexity. The remobilized hydrocarbons will be collected via porous candles and gas collection chambers and regularly analyzed (GC-MS, FTIR). The complementarity of the monitoring methods will be evaluated and numerical simulations of the LNAPL flow and transport through the contaminated soil will be carried out to identify the processes responsible for the pollutant remobilization. This work is partly funded by the DEEPSURF project ”Lorraine Université d’Excellence”, ANR-15-IDEX-04-LUE”.

Mots clés: groundwater; LNAPL; climate change

Domaines: Sciences de l'environnement; Milieux et Changements globaux; Planète et Univers [physics]; Sciences de la Terre; Hydrologie

Amélie Cavelan, Pierre Faure, Fabrice Golfier, Anne-Julie Tinet, Constantin Oltean, et al.. A new experiment to assess the impact of groundwater table level variations on petroleum hydrocarbon pollutants remobilization (LNAPL) in the climate change context. 1st OZCAR TERENO International conference: Advancing critical zone science, Oct 2021, Strasbourg, France. , 1st OZCAR TERENO international conference: Advancing critical zone science : abstract book, 37, pp.240-241, 2021. ⟨hal-03379715⟩