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Accueil > Ateliers transverses > BioGéochimie des systèmes Eau-Minéraux-Organismes (BioGEMO)

BioGeochemistry of organism-water-minerals interfaces(BioGEMO)

scientific coordination : G. IMFELD

publié le , mis à jour le

BioGEMO meetings : 09-02/2015-2016 (Salle de réunion, 1 rue Blessig)

Who ?
Friday 18th

September, 11h

Damien : Presentation done at the Goldschmidt (‘Microstructural Modifications of Dissolving Silicate Minerals : Why Should We Bother ?’) + ongoing projects ? Damien Daval Gwenaël
Friday 02nd

October, 11h

Charline : Compound-specific isotope analysis method development on pesticides ?
+ advises to PhD students : How to find a good postdoc ?
Charline Wiegert Sylvain
Friday 23th

October, 11h

Fatima : design and expected results of ‘DT50’ and ‘Ageing’ experiments of pesticide behavior in soils ? Fatima Meite Charline
Friday 13th

November, 11h

Izabella : Cu and Zn stable isotopes in wastewater Izabella Babcsanyi Fatima
Friday 4th

December, 11h

Joëlle : Rare earth element in Rouffach and elsewhere ? Joëlle Duplay Izabella
Friday 18th

December, 11h

Bastien : design and expected results of ‘intermediate experiment’ on mineral weathering + planning end of thesis Bastien Wild Benoît
Friday 8th

January, 11h

Benoît : Lab + instrument management : students’ preliminary training, lab security and organization ? Benoît Guyot Damien
Friday 22th

January, 11h

Gwenaël : ‘Visiting the Winogradski experiment : a biogeochemical benchmark’ Gwenaël Imfeld Tiphaine
Friday 12th

February, 11h

Sylvain (+Fatima/Charline/Benoît) : synthesis of the Rouffach campaign 2015 ? Sylvain Payraudeau Pablo
Friday 26th

February, 11h

Pablo : PhD thesis plan (modelling at the agricultural catchment scale) Pablo Zaldivar Bastien
Friday 11th

March, 11h

Tiphaine : ongoing projects on SOM and DOM ? Tiphaine Weber

1. Context and focus of BioGEMO
Earth’s elemental cycles are affected by biogeochemical processes but also by anthropogenic activities. However, the mechanistic interpretation of chemical dynamics in natural or anthropogenic surface and subsurface environments is often limited by an incomplete understanding of the coupled biotic and abiotic processes that govern chemical phase partitioning, transformation and transport. These heterogeneous and dynamic environments are characterised by a wide range of biogeochemical molecular scale reactions, whose relative importance is affected by pore, pedon and catchment or watershed scale drivers. Biogeochemical reactions form redox gradients that depend on the chemical composition, prevailing redox couples and microbial activities, and more generally modify the composition of pore water (chemical affinity, secretion of organic ligands), impacting the mineral dissolution and precipitation. Reciprocally, surface and subsurface environments may operate as biogeochemical reactors, which control the water flow and its chemical constituents (nutrients and contaminants). These environments thus reflect chemical reactions that generate larger scale structures (e.g., regolith formation), phenomena (e.g., catchment hydrologic response), and ecological services (e.g. regulation of water quality).
However, the underlying mechanisms and reaction networks driving the origin, transportation and evolution of natural and anthropogenic organic and inorganic compounds in biogeochemically active water-organisms-minerals interfaces have yet to be unravelled. The functioning of these biogeochemical hotspots and their role in biogeochemical cycling and transformation can be partly addressed by probing their properties at various scales. Among the biogeochemical hotspots, the rhizosphere, the soil and the mineralosphere have unexplored capabilities of biotic and abiotic transformations.

Fig. 1.

a : a biogeochemically dynamic water-mineral-organism interface : the rhizosphere.
b : a fluid-mineral interface : the mineralosphere (silicate-rich layer can be observed : how its fluid transport properties govern the mineral reactivity ?

2. Objectives of BioGEMO
The objective of our transveral axis BioGEMO is to explore the trends, attempts and approaches to study and predict the processes at the water-mineral-organisms interface. Our approach is multidisciplinary confrontation and discussion of observations and predictions obtained at different time scales (the hourly time step for microbial or annual activity for mineral reactivity) and space (nm characterizing the process elementary at EMO interface dm integrating biogeochemical dynamism across the rhizosphere or mineralosphere, or up to the catchment scale).

3. The BioGEMO workshops
In a series of workshops for the period 2013-2017, four main discussion themes are proposed in 2 hours meetings including a presentation and a ‘brain-storming’ discussion :
- 1- Characterization of biogeochemical and transformations processes in the water-mineral-organisms interface
e.g. : experimental approaches of ground and laboratory, coupling of microbial, isotopic, mineralogical, hydro-geochemical, microscopic methods, etc.
- 2- Biogeochemical mechanisms governing the mobilization and the transfer of solutes at the catchment scale
e.g. : biogeochemical cycles and/or transfer of organic /inorganic elements / contaminants on the scale of ponds hillsides natural/anthropisés, etc.
- 3- Modelling of biogeochemical processes in the water-mineral-organisms interface : biological processes in geochemical modelling and solute transport
e.g. : modelling of the interactions fluid / mineral phases/microorganisms ; biogeochemical models of reactive transfer in answer to the hydro-biogeochemical dynamics of the EMO systems, etc.
- 4- Joint design of ‘BioGEMO experiences and projects’ at the LHyGeS (brainstorming and plan)

4. Linking approaches – Bridging the gap
The advent of spectroscopic (e.g. GISAXS, EFTEM, STXM) and microscopic (e.g. HRTEM, AFM, SIMS) techniques has revolutionized our ability to study chemical reactions (including redox transformations) occurring at the (microorganism)-fluid-mineral interface at micrometer to molecular scales (e.g. Benzerara et al., 2003, 2005 ; Daval et al. 2009 ; Hellmann et al. 2012 ; Daval et al. 2013). This expanding panel of techniques provides a cornerstone, which has only been partly explored to confirm and/or revisit mechanisms and kinetics of water-microorganisms-minerals interactions. Such mechanistic understanding of geomicrobial processes at the micron and submicron scales will improve our understanding of their impact on elemental cycling and contaminant transformation at the ecosystem scale. In addition, measurements of isotopic fractionation and isotopic tracers, particularly when coupled to spectroscopic or modelling approaches, present new opportunities for assessing the chemical reactions, microbial activities and physical transport processes at water-microorganisms-minerals interfaces (e.g. Imfeld et al. 2009 ; Behrens et al. 2012). Recent analytical advances have allowed results of non-traditional stable isotope analyses (Fe, Mg, Ca, Cd, Cu, Hg, etc.) and more traditional isotope analyses of unique phases (e.g., C, N, H, O, S). These complementary approaches should now be combined to provide a critical link to unravel biogeochemical cycles, identify sources of contamination and improve our understanding on reaction pathways in macro-scale terrestrial environments. Increasing detail and resolution with which geochemical processes and microbial activity can now be characterised creates new challenges for the quantitative reactive modelling of the biogeochemical functioning of environmental systems. The upscaling of microscale processes and reaction parameters is crucial today to practically apply the new experimental knowledge at the field scale. Practical applications for topical environmental concerns, such as the evaluation of contaminated site remediation (Imfeld et al. 2008), or CO2 sequestration (Bearat et al. 2006 ; Daval et al. 2011), are directly concerned by these fundamental breakthroughs. Clearly, there is a need to (i) bridge the gap between geochemistry and microbiology to realistically account for biogeochemical reactions at various scales, and to (ii) quantify the impact of anthropogenic forcing on biogeochemical processes, contaminant behaviour, and ecosystem services.

5. Previous workshops
Spring Workshop’s 2013
Damien DAVAL, researcher in the LHyGeS, will present and discuss the EC2CO project " VALVE : Vestige of the change and the change of vestiges " that he coordinates :
The interactions between fluid and mineral represent the common denominator of geological, environmental, societal problems or engineering varied. In each of these various contexts, the method adopted to estimate the long-term evolution of the elementary flows during the interactions fluid-rock bases frequently on the same strategy. This strategy, reductionnist by definition, consists (1) to determine in laboratory, on freshly crushed monomineral powders, the laws of kinetics of dissolution of silicates and (2) to implement such laws in codes of reactive transport where the reactivity of a rock is described as the resultant of the reactivity of its constituent minerals. Today, the application of mécanistiques laws based on experiments of laboratory on monominerals in the modelling of process of large-scale change is an inescapable practice there hydro-and biogeochemistry.
While we expect from the use of these laws of the large-scale predictions of time(weather) and from space, it is collectively accepted that in the absence of individual established specific adjustments, they overestimate generally the speeds of change measured in the natural environment in a considerable way (until 6 orders of height). This observation illustrates the necessity of identifying the physical causes responsible for our difficulty extrapolating speeds determined in laboratory to revise the laws of speed classically implemented in the codes of reactive transport, and to hope eventually(later) to generate more reliable simulations.
This project exactly aims at investigating innovative tracks which could contribute to reduce such distances, by putting at the heart of our approach the link between the macroscopic kinetics of dissolution of silicates and their state of microscopic surface, in an environment forced réactionnel. This objective is justified in consideration (1) of the small quantity of studies centered on the link between speed of dissolution and evolution of the mineral surface (by comparison with plentiful literature dedicated to the links between speed of dissolution and chemical composition of the fluid) ; (2) In the observation that mechanisms of "ageing" of the exposed surfaces are effectively for the work during the processes of change, although their effects are neither integrated into the current codes, nor inevitably measurable on the scale of time approached in laboratory (week / month). To revisit the laws of change of silicates through an approach linking characterization of natural objects, experiments in laboratory in controlled conditions and digital modelling constitutes the heart of this project.

Summer Workshop’s 2013
Le prochain atelier de l’axe transverse du LHyGeS "BioGéochimie des systèmes Eau-Minéraux-Organismes" : BioGEMO a eu lieu le 20 septembre 2013, 10h00-12h00, salle de réunion (2ème).
Lors de cet atelier, Marie-Claire Pierret et Sylvain Payraudeau ont présenté un regard croisé sur les observations au Strengbach et à Rouffach autour du thème :
"Mécanismes biogéochimiques régissant la mobilisation et le transfert de solutés à l’échelle de bassins versants naturels ou anthropisés".
Sur la base de ces exposés, l’objectif est de discuter ensuite ensemble des mécanismes bio-géochimiques régissant les transferts à l’échelle de bassins versants, et possiblement comment les identifier et les conceptualiser.
Un volet présentation et un autre volet sur réflexions ont permis de donner des éléments de réponse aux questions suivantes :
- Quelles sont les approches majeures actuellement utilisées internationalement pour identifier et caractériser les mécanismes biogéochimiques régissant les transferts à l’échelle du bassin versant ?
- Quelles sont les approches intégrées à développer en priorité (rapprochant les communautés scientifiques hydrologiques, biogéochimiques et biologique) qui permettraient d’accroître la compréhension du cycle de l’eau et des cycles biogéochimiques à l’échelle du bassin versant ? Quelles sont les verrous principaux à la mise en œuvre de ces approches ?
- Comment renforcer les recherches menées sur les interactions et les couplages entre processus élémentaires (biologiques, géochimiques et hydrologiques) au sein de bassin versants ? Au sein du LHygeS ?
- Comment l’étude des mécanismes biogéochimiques régissant le transfert dans les bassins versants faiblement anthropisés (comme le Strengbach) peut servir à l’étude des transferts dans les bassins versant fortement anthropisés ou pollués (comme le bassin de Rouffach) ? Au sein du LHygeS ?
- En se projetant dans les 10-20 prochaines années, quelles perspectives voyez-vous pour étudier et prédire les mécanismes biogéochimiques régissant les transferts à l’échelle du bassin versant ?