Julie Lions

The kinetics and mechanisms of perfluorooctanoic acid (PFOA, CF₃–(CF₂)₆–COOH) defluorination were investigated in alkaline dimethyl sulfoxide/water (DMSO/H₂O) solutions under various conditions. PFOA and its by-products were characterized and relatively quantified using ultra-high-pressure liquid chromatography coupled with mass spectrometry, while degradation efficiency was assessed by potentiometric fluoride measurements with an F⁻-selective electrode, complemented by scanning electron microscopy and energy-dispersive spectroscopy. The redox degradation mechanisms of PFOA were projected through a detailed description of redox reactions involving only carbon atoms within PFOA and its by-products, driven by OH·/OH⁻ and H₂O/H· redox couples, into which OH· and H· are transient redox intermediates associated with electron-transfer events, rather than freely diffusing radical species; OH· and H· originated from the redox reactions between the electron donor OH⁻ and the electron acceptors O₂, PFOA and H₂O. The nucleophilic and/or electrophilic nature of redox reactions depends on the carbon oxidation state. The most favorable PFOA degradation pathway involves the stepwise oxidation of carbon driven solely by OH·/OH⁻ redox couple, leading to the elimination of a –CF₂– unit as 2 F⁻ and CO₃²⁻. The OH·/OH⁻ and H·/H₂O redox couples mediate secondary electron-transfer pathways, resulting in the simultaneous oxidation and reduction of two different carbon atoms within the same molecule. Water content and its continuous formation during the redox reactions limit the process by enhancing the solvation of OH⁻, thereby decreasing the oxidizing capacity of the OH·/OH⁻ redox couple. The higher the NaOH/PFOA molar ratio (≥ 62:1), the lower the H₂O content (DMSO/H₂O volume ratio ≥ 3.87:1) and the higher the temperature (≥ 120 °C), the greater the PFOA defluorination.

Aquifers may naturally contain undesirable and toxic trace elements, known as geogenic contaminants. The presence of these micropollutants poses a major challenge for groundwater management, and has health, economic, and environmental consequences.Areas with high concentrations, either elevated or exceed the guideline value of water standards, are generally identified through the analysis of groundwater data. However, it should be possible to predict these occurrences based on their presence in the solid matrices of aquifers and their mobilization controlled by the physicochemical conditions of the water.To better predict the occurrence of inorganic natural pollutants, we have developed a methodology, based on an integrated approach to better understand the distribution of these elements in aquifers, the conditions controlling their presence, and their evolution in groundwaters.The methodology combines two complementary approaches: i) predictions of geogenic elements content in rocks, including their speciation, using a source to sink methodology are cross-correlating with ii) hydrogeochemistry to identify water-rock interaction processes and the potential mobility of the elements according to physicochemical conditions (e.g., redox conditions). This makes it possible to predict the spatial distribution of geogenic elements (e.g. As, Se, F, etc.) as well as the processes of mobilization in groundwater.Using a geographic information system (GIS), this study compares predicted occurrences using a source-to-sink (S2S) approach with available data including a large dataset on groundwater quality data (ADES data base, a national database publicly available). By interpretating the chemical composition of water, geochemical modelling via PHREEQC and geological data, it is possible to confirm but also to contribute to the S2S modelling.The study focuses on aquifers linked to the Massif Central (France). Geological source-to-sink paleomaps and drilling data are used to correlate the availability in sedimentary deposits of elements such as arsenic (As), selenium (Se), fluorine (F), with the main periods of erosion, transfer, deposit and remobilisation between the end of the Cretaceous and the Miocene. Arsenic, in particular, is studied in various geological layers with a focus on its speciation and mobilization in confined aquifers such as the Beauce calcareous confined aquifer (Southern Paris Basin).This approach presents a real interest in terms of groundwater quality, as it helps to anticipate water quality degradation linked to groundwater exploitation in aquifer impacted by the natural presence of geogenic metals.This work is part of the PEPR OneWater DEESAC project (France 2030), illustrating a transdisciplinary approach combining geology, geophysics, geochemistry, and hydrogeology.

Natural arsenic concentrations in groundwater locally exceed drinking water standards, raising public health concerns. Preventing its release requires identifying its 3D distribution in rocks and water–rock interactions. We address this through a source-to-sink approach applied to predicting arsenic distribution in Miocene sedimentary deposits of the southwestern Paris Basin, where geogenic arsenic is present and monitored in aquifers (e.g., lacustrine deposits of Beauce Fm. – Aquitanian) underlying sedimentary cover (fluvial deposits of Sables et Argiles de Sologne Fm. – Burdigalian to Pliocene).Our approach combines source-to-sink tools, chiefly geomorphology and sedimentology, with arsenic geochemistry in order to trace arsenic transfer from source areas to sedimentary reservoirs. It involves: (1) identifying sources coupling the reconstruction of paleoreliefs from planation surfaces and paleodrainage areas and characterizing arsenic concentrations in the drainage areas using pXRF ; (2) characterizing depositional environments, including sedimentary facies and their actual and past physicochemical conditions, and the associated arsenic content in terms of abundance, speciation, carrier phases within each facies (pXRF, sequential extractions, μXRF and ICP-MS), and mechanisms of arsenic retention (sorption, complexation and mineral precipitation).Two source-to-sink systems have been identified in our study: (i) an Aquitanian endorheic lake system and (ii) a mid-Miocene terrigenous system. The Aquitanian system is fed by the surrounding reliefs, leading to the remobilization of arsenic contained in older sedimentary series. Arsenic is sequestered in deep-lake facies, where it is mainly trapped by framboidal pyrite and organic matter under reducing conditions. The mid-Miocene system reflects a reorganization of the drainage basins, resulting in the recycling of older formations and material derived from the northern Massif Central (MCF). Arsenic is predominantly carried by pyrite in reduced floodplain facies. Tectono-hydrogeological destabilizations since the Tortonian have promoted the oxidation of these reduced sedimentary reservoirs, the release of arsenic in groundwater and partial precipitation of secondary arsenic carrier phases.This study highlights the role of geomorphology and sedimentology in controlling arsenic drainage and trapping, and establishes a link between initial trapping and current groundwater quality. (ANR-22-PEXO-0010 – PEPR One Water Eau bien commun research program).

This study presents a comprehensive sensitivity analysis framework to disentangle the drivers of predictive uncertainty in spatial interpolation and how they ultimately affect spatial predictions. Developed within a Global Sensitivity Analysis context, the proposed approach is model-independent and generic, allowing for broad application across diverse spatial interpolation workflows.The framework is demonstrated using groundwater Sulfate concentration in the Paris Basin, a dataset characterised by sparse and highly clustered sampling across six distinct aquifers according to the French "BD LISA" hydrogeological system (https://bdlisa.eaufrance.fr/). We represent the underlying spatial process as a Gaussian Random Field, leveraging Integrated Nested Laplace Approximations for computationally efficient Bayesian inference. This allows for a probabilistic treatment of uncertainty even within complex spatial structures.We systematically evaluate the impact of several key uncertainty factors related to both data and model configuration: (1) the number of monitoring stations and their spatial distribution; (2) the selection of the environmental covariates and the functional form of their effects (linear vs. non-linear); (3) the treatment of censored data (values below detection limits); and (4) structural assumptions regarding the spatial covariance function, specifically the estimation of variogram hyperparameters such as range, sill, and nugget effects and their prior specification. By propagating these uncertainty sources through our framework, we derive domain-wide aggregated sensitivity measures. These metrics quantify how specific data topologies—including sampling density, clustering effects, and censoring rates—govern the stability and accuracy of the resulting spatial interpolations.Finally, the results facilitate an in-depth discussion on the limitations of purely probabilistic methods in data-poor scenarios. We provide an outlook on the potential of extra-probabilistic approaches, such as imprecise or interval-based kriging, to more robustly address the wide range of epistemic uncertainties inherent in environmental monitoring.We acknowledge financial support of the French National Research Agency within the HOUSES project (grant N°ANR-22-CE56-0006).

Confined aquifers, generally more protected from anthropogenic pressure, present potential alternative water resources of good quality to surface and subsurface water resources. However, their exploitation, potentially affecting the resource in a long-term way, requires a good understanding of their functioning to ensure their sustainable management. In order to gain some understanding of the processes involved in confined aquifers, we present here results obtained from the multilayered Beauce limestone aquifer, in the Centre region of France. This aquifer is already heavily exploited for drinking water supply and agriculture.The developed methodology implies 1) a new interpretation of potential recharge areas from the newly acquired aquifer geometry through geological data analysis, 2) an extensive analysis of the piezometric and geochemical (major and trace elements) and isotopic groundwater database, and 3) new data obtained from groundwater sampled from a nested piezometer plateform.The main results are synthesized below:Several potential recharge zone have been identified. The first one corresponds to a fault zone that could allow exchanges between the surface, the Beauce limestone and deeper aquifers. The second one is a local outcrop of the limestone caused by an anticline. The third one corresponds to local, diffuse recharge from the unconfined water table where the overlying aquitard become thinner or non-existent; The Beauce limestone formation comprises two main aquifer sub-units, locally separated, when existing, by a semi-permeable aquitard. The two sub-aquifers nevertheless may have distinct geochemical signatures, even though they are largely interconnected; Piezometric data indicate that the groundwater regionally flows from east to west, originating in an area where the aquifer does not outcrop and indicating indirect recharge from another aquifer; Dissolved inorganic carbon isotopes (13C, 14C) show an apparent ageing of the groundwater in the opposite direction to the flow, with more ancient groundwater upstream (up to 30 ka B.P.) and younger groundwater downstream (< 10 ka B.P.). Depleted groundwater in 2H and 18O, in agreement with the radiocarbon residence time, confirm the paleoclimatic effect recorded in the confined Beauce limestone aquifer although the confined aquifer is relatively shallow (< 150 m deep). These results allow to better understand the hydrodynamic behaviour of this aquifer by highlighting potential recharge zones, groundwater origin as well as the possible exchanges between inter- and intra-aquifer systems. Combining all the available information (geological, hydrogeological, chemical and isotopic) is thus essential for establishing robust conceptual model of multi-layer confined systems and will provide useful information to managers for the sustainable management of the resource.

In France, two-thirds of the water withdrawn for drinking water supply comes from groundwater (OFB, 2017), hence monitoring PFAS is essential to document spatial distribution, dynamics and anticipate potential impacts on water quality.A good monitoring resolution in term of spatial extend, frequency, analytic performance is crucial to better understand sources, pathways and potential impacts. We propose a focus on the regulatory groundwater monitoring for France, where an increasing number of PFAS compounds have been regulated for monitoring, going from 6 in 2015 to 20 in 2022, in compliance with the European Drinking Water Directive (Directive 2020/2184). However, as PFAS represent a family of more than 10,000 compounds, it is necessary to assess the total PFAS contamination, beyond the list of regulated parameters.The concept of the “total PFAS” is not yet clearly defined and is open to question. Measurement by combustion ion chromatography (CIC) provides access to adsorbable organic fluorine (AOF), i.e. the total measurement of fluorinated organic compounds, without the need to identify each individual compound. It is a fast, inexpensive method that gives an indication of the overall level of contamination. However, it can also include substances other than PFAS (e.g. fluorinated pharmaceuticals). Methodological and analytical developments under the framework of the H2020 PROMISCES project (GA No 101036449) will contribute to the deployment of this approach in water monitoring.At the French level, we analysed the available data on PFAS concentrations in groundwater (from the ADES[1] database) from different perspectives.In terms of spatial contamination, PFAS occurrences were mapped in relation to different hydrogeological contexts and pressures (emission sources, aquifer types, density of use,…). These groundwater occurrence maps are of interest for the implementation of health monitoring of water intended for drinking water supply, both from the point of view of geographical sectors and water ressources, but also for the analysis of the contexts to be targeted. This will support decision making for drinking water supply where health risk is of primary interest.In terms of time, the first PFAS analyses are reported for the period 2009-2011. In the whole dataset, the more densely monitored parameters (> 30,000 analyses) are PFOA, PFOS, PFHpA, PFHxA, PFDS, and PFHxS.Quantification rates vary considerably between the different molecules analysed. PFOS is the compound with the highest quantification frequency (17.8%). It is also the most frequently researched compound (about 38,000 analyses). Other compounds researched with the same intensity (about 35,000 analyses) have lower quantification frequencies: PFHxA (12.3%), PFOA (11.2%), PFHxS (10.5%), PFBS (7.8%), PFHpA (7.1%), PFBA (5.4%). For the dataset considered, 12 of the 20 compounds were found, on average, less than 3 times out of 100.Our work highlights that PFAS are widely observed in French groundwaters. Quantification rates are among the highest reported for micropollutants at the national level. Given the potential time-delay effect, due to stock effect, in the soil and unsaturated zone is suspected, and the documented adverse effects on human health, careful monitoring of these compounds is essential in the near future to support decision-making.

Resource scarcity has increased interest in the circular economy (CE) for environmental, economic, and social sustainability. The goal is to minimize waste generation and efficiently incorporate waste back into production processes without adversely impacting human health or the environment.By recognising the importance of assessing the potential accumulation of chemicals and associated risks within the CE, the Horizon 2020 project PROMISCES focuses specifically on the so-called "forever chemicals" such as per- and polyfluoroalkyl substances (PFAS) in five CE routes, including semi-closed water cycles for drinking water (DW), wastewater reuse in agriculture, nutrient recovery from sewage sludge, material recovery from dredged sediments, and groundwater and land remediation for safe reuse.Based on the results from literature reviews, experiments and case studies, the project addresses the fate and transfer of PFAS across these CE routes. Despite the challenge of analysing PFAS in complex matrices such as sludge and wastewater, robust and sensitive methods have been developed and the following conclusions can be obtained:Wastewater treatment provides a limited removal efficiency, especially when wastewater treatment plants receive large contributions from industrial wastewater streams. Advanced wastewater treatment technologies implemented for micro-pollutant removal are not fully effective for all PFAS. Additionally, degradation of precursors can result in increased PFAS concentrations in the effluent. Consequently, until new treatment solutions are implemented, PFAS hotspots may not be able to implement wastewater reuse (e.g. for irrigation).Riverbank filtration, as a first DW treatment stage, demonstrates limited removal of PFAS. Accordingly, in the presence of an upstream emission source, DW providers may need to implement advanced water treatment technologies.During wastewater and landfill leachate treatment, particularly long-chain PFAS may accumulate in sludge. Although low level of targeted PFAS compounds were quantified, the presence of precursors in sludge is suspected and may present a barrier to its agronomic valorization. To date, PFAS content in sewage sludge is not regulated and depending on the country, sludge may be spread on agricultural land, incinerated, or disposed in landfills. Valorisation of dredged sediment as secondary raw material has the advantage of limiting the cost of management and limiting the use of raw materials. Depending on the nature of the sediment (in particular organic matter content) and on the PFAS loads, different treatments result in different removal efficiencies. Moreover, treatments can result in the formation of new persistent PFAS from precursors. When initial loads are low, it seems possible to eliminate PFAS from the solid fraction. Nevertheless, the destruction of residual PFAS in the washing solution is necessary.In situ and on-site treatments of water and soil are confronted with environmental realities. Even if treatment trains can help overcome the complexity of PFAS treatment, the process efficiency is highly dependent on the alkyl chain length and the functional groups. As for sediment, although various treatment techniques exist, such as PFAS immobilisation, these do not result in complete degradation or removal of PFAS. This stands in the way of achieving a CE, as only after full removal of PFAS, safe reuse of resources can be guaranteed.

The PROMISCES project aims to understand the origins, routes and fates of industrial persistent, mobile and potentially toxic pollutants (iPM(T)s), including per- and polyfluoroalkyl substances (PFAS). These substances, also called “forever chemicals”, can be harmful to the environment, human health and circular economy resources.PROMISCES will develop, test and demonstrate, new technologies and innovations to prevent, monitor and remediate iPM(T)s in the soil-sediment-water system under real-life conditions in the field. In this way, PROMISCES will establish more cost-effective, sustainable and ecological technologies for remediating PFAS and iPM(T)s.The project will support the European Green Deal goals and sustainability roadmap of urbanised areas by reducing the environmental impacts on waters (surface and groundwater, urban runoff, drinking waters, wastewater, landfill leachate), soils (contaminated sites, brownfields) and dredged sediments (river, seaports) and of nutrient and material recovery (from sewage sludge to recovered fertilisers, dredged sediments to valorised materials, reclaimed water to crops).To pursue this objective, PROMISCES is centered around seven representative case studies in different European regions linked with challenging chemical pollution, including locations in Spain, Italy, Bulgaria, France, Germany and the Danube river basin between Vienna and Budapest.This Horizon2020-Green Deal project will address key technological challenges while also developing recommendations for implementing relevant EU plans - such as the Zero Pollution Action Plan, the Circular Economy Action Plan and the EU chemicals strategy for sustainability - and EU policy directives, such as the Sewage Sludge Directive and the Water Framework Directive.

The Water Framework Directive (WFD) requires EU member states to assess the chemical status of groundwater bodies, a status defined according to threshold values for harmful elements and based on/the natural background level (NBL). The NBL is defined as the expected value of the concentration of elements naturally present in the environment. The aim of this study is to propose a methodology that will be broadly applicable to a wide range of conditions at the regional and national scale. Using a statistical approach, the methodology seeks to determine NBLs for SO₄, As, Cd, Cr, Cu, Ni, Zn, and F based on the lithology of aquifers from which groundwater monitoring data were collected. The methodology was applied in six EU countries to demonstrate validity for a wide range of European regions. An average concentration was calculated for each parameter and chosen water point and linked to a lithology. Based on the dataset created, significant differences between lithologies and pressure categories (urban, agricultural, industrial, and mining) were tested using a nonparametric test. For each parameter, 90th percentiles were calculated to provide an estimation of the maximum natural concentrations possible for each lithology.