Earth, Ecology and Environmental sciences

A scientific request for an efficient instrument for unambiguous in-situ analysis of the composition of the Solar system rises up, since an abundance of complex organic compounds at planets, moons and interplanetary medium has been experimentally confirmed. New experimental data will unveil chemical history of the Solar System and probable mechanisms of formation of extraterrestrial organic compounds. A space-grade Orbitrap™-based high-resolution mass spectrometer will allow to obtain required data. In scope of this research project, Lab-CosmOrbitrap and OLYMPIA mass analyzer instruments developed within the CosmOrbitrap project were optimized. New sampling systems and ionization mechanisms proposed for the future space-grade instruments have been developed and evaluated. Experimental calibration data for solid (the real Moon fragment) and gaseous samples (He, C2H4, N2 and CO) required for the currently designed space instruments (CRATER, CORALS and HANKA) were measured.

Oxidation of SO2 to sulfuric acid impacts acid precipitation and aerosol nucleation in Earth’s atmosphere in remote and polluted environments.  This oxidation can take place in both the liquid and gas phase.  Only the gas-phase oxidation is expected to lead to new particles because of the clustering reactions of H2SO4. This aerosol nucleation has a major effect upon air quality and Earth’s radiative balance, and is of crucial importance to the chemistry of the atmosphere. 
The rate limiting step in this process is the reaction of OH radicals with SO2 to form HSO3. The pressure- and temperature-dependent reaction of OH + SO2 has been studied many times previously – since its importance was first recognized in the 1970s. Notwithstanding, some of the most recent literature has cast doubt on much of this data, especially under conditions that are relevant to atmospheric chemistry. 
Here, we present measurements of the rate coefficient using the pulsed laser photolysis–laser induced fluorescence technique as a function of temperature (249–373 K) and of pressure in helium, argon, nitrogen and oxygen bath gases (30–600 Torr). In addition, relative rate measurements using a chamber at 760 Torr (N2, O2 and air) were also performed to corroborate our absolute observations. By utilizing these new data, together with the available literature data, an updated pressure- and temperature-dependent parameterization will be provided. This allows the atmospheric impact of this reaction to be constrained with a new level of certainty.
 

The use of residual biomass from forest harvesting for energy production is viewed as a means to reduce fossil-fuel consumption. However, the impact of wood energy harvesting on soil and future site productivity remains a major concern. During this fellowship, we analysed why forest biomass harvesting of whole trees in Quebec reduced soil organic carbon (C) and total nitrogen (N) reserves in certain sites. We also estimated soil C and N labile and stable fractions in the Centre-Val de Loire region in France, and its relationship with current soil sensitivity indices to residual biomass harvesting. This research shed new insights on soil properties that could explain their sensitivity or resilience to forest biomass harvesting. We believe that this fellowship made a significant contribution to scientific knowledge and address pressing societal challenges.

The Earth’s radiation environment couples to the upper atmosphere through precipitation of energetic electrons in high-latitude regions. This precipitation is driven by electromagnetic waves in the plasma environment around the Earth, including waves generated by lightning discharges. We use data from the DEMETER mission, built and operated by LPC2E between 2004-2010, to better understand the propagation characteristics of these lightning-generated signals and their effects on the radiation environment. Further, we use lessons and heritage from the DEMETER mission to inform design decisions and data analysis techniques for the upcoming CANVAS mission, a collaboration between the University of Colorado Boulder and LPC2E. CANVAS is expected to launch in mid-2024.

The present study was conducted to elucidate the connections of modern groundwater pollution to specific munitions materials used and destroyed during and after World War I (WWI).  Large quantities of unexploded munitions are still present in the tunnels and soils of former battlefields. We performed analyses of the isotopic compositions of nitroaromatics, nitrate, and perchlorate in samples of munition and contaminated groundwater collected at three sites along the WWI battlefront in northern France. The isotopic data from these samples indicates a direct connection between the groundwater contamination and the WWI munitions. Potential adverse effects on public health from munitions compounds in groundwater indicate an urgent need for further evaluation of the continuing presence of legacy WWI munitions and their contribution to chronic groundwater pollution in the region.

 The Moon is a cornerstone for understanding the early history (origin, budget and timing) of volatile elements (H, C, F, S, Cl) delivered to all terrestrial planets. The volatile study of lunar magmatism is the most direct way to reconstruct the volatile budget of the Moon’s interior.  However, this reconstruction is compromised by magmatic processes that modify the initial compositions of the lunar magmas. The final goal of our work is to determine how sulfide saturation and segregation in all the compositional range of lunar lavas have affected the sulfur isotopic composition of the magmas. The determined sulfur isotopic fractionation between lunar silicate melts and immiscible sulfide blebs will allow us to directly unravel the sulfur isotopic composition of the heterogeneous reservoirs forming the Moon’s interior, and therefore, provide fundamental information on the early evolution of sulfur isotopes of the Earth’s satellite. 

Mineral reactions in subsurface energy systems result in deviations from local equilibriums and can impact critical engineering properties of the system, including storage capacity (porosity) and injectivity (permeability). Accurate understanding and prediction of reaction rates and impacts on formation properties is needed for safe and efficient design and implementation of these engineered systems. Precise simulation of mineral reaction rates is limited by a poor understanding of the mineral reactive surface area in porous media. Here, pore scale numerical simulations are leveraged to simulate mineral reactions for varied flow and reaction conditions and the effective surface area analyzed. Numerical simulations of reactions in a porous media mesh are carried out in OpenFOAM® and a new scaling factor, relating the effective surface area to the accessible surface area, determined.

The work presented is a report on a research stay as part of LE STUDIUM for visiting researchers from September 1 to November 30, 2025, at the Laboratory of Physics and Chemistry of the Environment and Space (LPC2E) of the CNRS in Orléans. This is a research stay whose objective is to apply an in-depth methodology for the microphysical, optical, and radiative characterization of aerosols at the surface and at altitude. This technique is based on in situ measurements taken by the LOAC instrument during flights using weather balloons, climate model simulations, and data from airborne and satellite sensors. This enabled us to understand the measurement methodology using the LOAC instrument, which has already been tested by the CNRS's LPC2E, and aerosol modeling using ECSM2 model simulations. Based on the measurement campaigns carried out, we analyzed the aerosol profile as well as that of PM1, PM2.5, and PM10, and the volume size distribution of the particles. Also, based on aerosol extinction evaluated using the Mie code, we were able to determine the aerosol optical depth (AOD), which is an integration of the extinction coefficient across the atmospheric layer. In addition, this trip was an opportunity to participate in a validation study of the ATLID lidar aboard the EarthCare satellite, which has been in orbit since May 2024. This has enabled us to learn a new approach to the optical and microphysical characterization of aerosols that can be applied in Burkina Faso and West Africa in general.

The booming field of diffusion chronometry allows geoscientists to extract the timing and duration of subsurface magmatic processes that occur prior to volcanic eruptions. The technique relies on modeling step-wise, concentric chemical gradients that form within magmatic minerals as they grow or get perturbed by new incoming magma prior to volcanic unrest. These chemical ‘tree rings’ are smeared with time by element diffusion, so that the amount of time between perturbation and eruption can be recovered if the mobility (diffusivity) of elements is calibrated in the lab at magma temperatures. This project aims to resolve recently uncovered discrepancies between widely-used element diffusivities obtained in simplified systems (e.g., mineral-mineral couples) and those obtained in melt bearing systems (mineral-melt couples). The new experiments carried out during a STUDIUM-supported sabbatical in 2024-2025 confirmed that the presence of melt is responsible for important differences in element mobilities for olivine, perhaps via the presence of H2O. Diffusivities in plagioclase, by contrast, are not influenced by melt or H2O, implying that current community practices are robust. The underlying mechanisms by which these differences in element behavior appear are still being investigated, and new tools recently tested (hyperspectral cathodoluminescence) may hold important clues as to the presence and distribution of point defects in these minerals. 

Larix decidua, the European larch, is an excellent model to evaluate the association between genetic and phenotypic variation with environmental gradients in forest species. In the present work we evaluated the genetic variation of neutral and selective SNP markers together with the variation of eight quantitative traits along an altitudinal gradient in a natural population of this species located in the Provence-Alpes-Côte d'Azur Region (France). Four samples of about 200 trees each were obtained respectively from plots situated at 1350, 1700, 2000, and 2300 m above sea level. In each sampled individual four tree ring variables and four plasticity variables were evaluated. The molecular dataset consisted of the individual patterns of 46388 SNP loci. The joint analysis of molecular and quantitative trait data allowed evaluating population structure, detecting presumptively selective loci, and demonstrating the adaptive significance of the quantitative variables considered.

Plants are exposed to multiple stressors simultaneously, but can receive help deterring biotic stressors from belowground mutualists such as arbuscular mycorrhizal fungi. Previous research has identified that this “help” occurs primarily via enhanced direct defences against chewing herbivores. However, our preliminary data had suggested that AM fungi promote indirect defenses against sucking herbivores like aphids. Here we tested this premise in tomato. We exposed plants to colonization by AM fungi or not, and herbivory by potato aphids or not. We then measured plant biomass as well as changes in volatile organic chemistry over time, and attraction to plants within our treatments by parasitoids in wind tunnel trials. While analyses are ongoing, we found an influence of AM fungi on plant biomass and a trend toward greater attraction of parasitoids to plants hosting AM fungi. Surprisingly we found no impact of aphid herbivores on the attraction of their parasitoids, and no interaction between AM fungi and aphid herbivory on parasitoid attraction. This suggests that AM fungi do, as we hypothesized, promote indirect defences of plants.

The ongoing acceleration of climatic change makes it even more urgent to understand how tree seed sources (provenances) respond when growing in climates different from those they are naturally adapted to, either when planted on warmer or on colder sites than the climate that occur at their native distribution site. We evaluated four years of growth, bud phenology and survival of a Larix decidua clonal elevational reciprocal transplant trial in the French Alps, at Villard-St-Pancrace, close to Briançon (LN 44.9°; LE 6.65°). The experiment has four experimental sites, distributed along a north-faced Alpine steep-slope, at contrasting elevations: 2,400, 2,000, 1,700 and 1,350 m a.s.l. On each site, 4 sets of 30 clones were reciprocally planted, with each set originating from adult trees selected in natural forest plots at nearly the same elevations (2,300, 2,000, 1,700 and 1,350 m a.s.l). Results indicate that: (a) Plot populations have lower survival rates when relocated to environmental extremes within the mountain range, whether to colder sites at higher elevations or to warmer sites at lower elevations. (b) Growth also decreases when they are moved to colder (higher elevation) sites, although in general it increases when they are moved to warmer (lower elevation) sites. (c) Such growth pattern might be in part explained by the phenology of the leader bud elongation: by the end of spring, leader buds have already started to elongate at lower elevations, meanwhile they are still in full dormancy at the highest elevational site.