WP5 : Biogeochemical Functioning of Surface Environments – Role in the Formation of Biogenic Gases and the Transformation and Transfer of Pollutants

Sébastien Gogo (CNRS-ISTO), Fabienne Battaglia (BRGM-ISTO), Isabelle Cousin (INRA)

Background and rationale

The interactions between microorganisms and the carbon substrate and their roles in GG 16emissions (CO2, CH4, N2O, etc.) is studied in sphagnum bogs. In fact, these ecosystems concentrate 1/3 of the global inventory of carbon in the soil in a small area. They can have strong feedback effects on the air temperature by raising it by an increase of greenhouse gas originating from microbial activities. In these environments, due to climate change, an increase in coverage by vascular plants affecting the degradability of litter and promoting symbiosis with mycorrhizal fungi changing the capacity of bogs to sequester carbon is predicted.

More specifically, our research seeks:

  1. to test the respective effects of temperature and humidity (notably from experimental simulations on instrumented sites) on the chain of reactions between enzymatic activities – functioning and structure of microbial communities – labile and recalcitrant carbon, and modeling this chain of reactions ;
  2. to study the dynamics of the microbial communities involved in these reactions ;
  3. to improve our understanding of mycorrhizal fungi and the associated microorganisms in the rhizosphere.

Additionally, studies on the coupling of carbon and nitrogen cycles and their consequences on the quality of the aquatic and atmospheric environment are conducted on this type of ecosystem and extended to other ecosystems that generate greenhouse gas, such as agricultural land and forests.We propose to develop the study of the biogeochemical mechanisms behind the formation of reactive forms of nitrogen, both soluble (NO3- for example) and gaseous (NH3, NOx, N2O), and carbon (dissolved or gaseous molecules: CO2, CH4), and, more particularly, the mechanisms that couple these two cycles. Indeed, reactive forms of nitrogen are generally produced during redox reactions, catalyzed by microorganisms, involving nitrogen and carbon compounds (denitrification, for example). The stockpile of carbon in the environments can also change depending on the availability of nitrogen.

For this, understanding micro-organisms and their associated activities within “soil-water-aquatic environment” systems is  decisive for defining the evolution of these environments under great anthropogenic stress. This understanding allows envisioning means for remediation of polluted environments (soil, sediment, industrial and mining environments). The originality of this work consists of conducting experiments aimed at characterizing the preponderant microbiological and biogeochemical processes that are involved in the transformation and mobility of organic and/or metallic pollutants and for the acquisition of data that can be used as input in numerical models simulating the fluxes of pollutant transfer in natural environments.

In detail this WP aims at

  1. studying the behavior of the micro-organisms of contaminated environments (soil/sediment) and/or the subsoil, which act as catalysts for geochemical processes (Fe, S and N cycle, essentially) and for(trans)formation of mineral phases, for purposes of improving the prediction of transfers and transformations of toxic substances (inorganic and organic) in the soil, the subsoil and the aquifers ;
  2. identifying and select the micro organisms and biochemical processes of interest that can then be exploited in bio processes and in biosensors (metrological tools), or as bio indicators of the quality of the environments. These studies will first be based on experimental laboratory studies, in static systems (batches,aquariums) where pollutants are remobilized and transformed by the activity of microorganisms; and dynamic systems (odometers, columns from dm3 to m3) suited to the flux of pollutant transfer in the soil.

The biosphere under extreme conditions will be characterized via the study of the metabolism of thebacteria subjected to particular living conditions (pressure, temperature and salinity). The study of the deep biosphere (estimation 6 to 40%) will teach us about their role in the biogeochemical carbon and sulfur cycles in particular, as well as the mobility of metals, trace elements and elements at risk. Moreover, the study of natural hypersaline environments (70 g/L) will teach us about the role of biofilms on the interactions between microorganism and mineral precipitations. These specific benthic ecosystems (cyanobacteria and anoxygenic photosynthetic bacteria) producing large quantities of O2 and feeding on the CO2 and H2S issued from respiration and sulfate reduction are extremely sensitiveto variations of the water level, and thus climate. Here again, these studies will rely on innovative experimental arrangements that allow laboratory culturing of samples of water, rocks or microbial consortia in situ under representative conditions in terms of pressure (up to 200 bar), temperature (up to 120 °C) and/or typical chemical conditions for thesystems studied.

Results of WP 5 (2011-2014)

The main topics addressed were (i) the effects of redox conditions on biogeochemical cycles (C and N) and (ii) the transformation and mobility of organic and/or inorganic pollutants. The approach combines experimental studies (field and laboratory) and modeling studies at different scales.

Effects of redox conditions on the functioning of biogeochemical cycles – C dynamics in peatlands: effects of plant changes. The mechanisms involved in C dynamics in Sphagnum peatlands invaded by vascular plants (e.g. Molinia caerulea, Betula spp) were assessed by decomposition kinetics experiments (in situ and in laboratory) of litters from indigenous mosses (Sphagnum) and potentially invasive plants (Molinia caerulea, Betula spp, Pinus uncinata , Eriophorum vaginatum). A model integrating C fluxes (solid, dissolved and gaseous) was developed based on the experimental results. This model reproduces the early stages of decomposition especially when one organic matter (OM) pool is considered and when the rate of catalysis and respiration decreases with time following a negative exponential distribution. The results of incubations (monoculture and mixture) of Molinia caerulea and Sphagnum rubellum litters also showed a non-additive effect of the mixture on mass loss, dissolved OM and respiration reflecting a stimulation of C dynamic from Molinia caerulea due to better water holding conditions by Sphagnum mosses (in situ results) and possible microbial processes. Current laboratory experiments are addressing these possible microbial processes on the occurrence of such a non-additive effect.

Effects of redox conditions on the functioning of biogeochemical cycles – Control of CO2, CH4 and N2O emissions by soil hydrological conditions. Laboratory experiments simulating changes in hydrological conditions (water table, soil moisture, rainfall) have been conducted on unstructured soil samples and peat mesocosms. The results show:

– a gradual increase in CO2 flux simultaneously with a stepped decrease of CH4 flux during a gradual decrease in the water table level;
– a decrease in CO2 flux and a delayed increase of CH4 flux during a simulated rainfall event followed by a drying period;
– the presence of N2O emission peaks which are attributed to the reconnection of the pore network occur during soil water desaturation. This result is being introduced in the modeling of N2O emissions from soils.

Furthermore, we have shown that stochastic modeling of N2O emissions can predict the distribution frequency of the emissions of this gas at intra-plot scale. Stochastic modeling will be compared to spatially integrative measurements.

Organo-mineral interactions – Impact of organic matter and environmental constraints on the speciation and mobility of inorganic pollutants. In the context of management of polluted sites, organic matter (OM) amendments may be proposed in order to improve plant growth while applying a phytostabilization technique. When diffuse pollution affects large areas, the agricultural practices of soils amendment may impact transfer of inorganic pollutants, through bacterial activities, either affecting groundwater or food crops. The influence of specific bacteria activities on this phenomenon is poorly documented in the international state of the art. The Labex Voltaire work has contributed to the following scientific program aiming to enlighten the role of soil microbial populations on the behavior of inorganic pollutants in presence of OM. In particular, it appears that organic substances affect the ability of bacterial strains to oxidize AsIII into the less mobile AsV form. This also depends on soil characteristics, in particular the intrinsic soil OM concentration. Polluted soils containing arsenic and toxic metals (Pb, Sb), and incubated with or without OM, show an increase in As and Pb mobility linked to the conjunction of OM presence and microbial activity. The next step will be the preparation of a mesocosm experiment that will allow, in 2015, studying the influence of OM amendment and fluctuations of groundwater level on the mobility of arsenic and metals in an automatically monitored platform device.

Organo-mineral interactions – Ecodynamics of metals and metalloids in soils contaminated phytoremediated or undergoing revegetalisation. This work focused on studying the efficiency of two phytoremediation options: phytostabilisation and phytoextraction assisted by organic and inorganic amendments, to address the high concentrations of potentially toxic trace elements (PTTE) in a natural soil and in a contaminated technosols. Total concentrations of dissolved trace elements were determined in the soil pore water. The soil exposure intensity was measured by DGT (Diffusive Gradients in Thin films) sensors. Phytoavailability of PTTE was characterized by germination tests with bush beans grown on contaminated soils where foliar trace element concentrations were determined. Then an artificial neural network model was applied to understand the most relevant factors on the PTTE phytoavailability variability. Both options have been able to reduce concentrations or phytoavailability of PTTE in the presence of amendments. Artificial neural networks have been very effective in predicting the missing data and to determine the parameters controlling the variability of the PTTE phytoavailability from soil parameters.

Results of WP 5 (2015-2018)

The main topics addressed during this period focus on (i) effect of redox conditions on the functioning of biogeochemical cycles (C and N) and (ii) transformation and mobility of organic and/or inorganic pollutants. The approach combines experimental studies (field and laboratory) and modelling at different investigation scales.

Effect of redox conditions on C, N biogoechemical cycles.

Dynamics in peatlands: Effects of changes in plant cover. The mechanisms involved in C dynamics in Sphagnum peatlands invaded by vascular plants were assessed by decomposition kinetics experiments (in situ and in laboratory) of litters from indigenous mosses (Sphagnum) and potentially invasive plants (e.g. Molinia caerulea). A model integrating C fluxes (solid, dissolved and gaseous) was tested on the experimental results. This model reproduces the early stages of decomposition especially when one organic matter (OM) pool is considered and when the rate of catalysis and respiration decrease with time following a negative exponential distribution (Gogo et al., 2014). We demonstrated the synergistic effect of litter mixtures on (i) decomposition of the OM that can be related to their water content (Gogo et al., 2016) and (ii) the Dissolved Organic Carbon (DOC) contents and CO2 and CH4 production and emission that appear to be strongly related to soil temperature, which itself varies according to the vegetation cover (Leroy et al., 2017). A conceptual hydrological model has been developed to assess the impact of soil rewetting on hydrological functioning and DOC dynamics in a rehabilitated peatland. The model (ten calibrated parameters) correctly reproduced the time series of water table and pore water DOC concentrations. The water table drawdown severity has been identified as the major factor controlling DOC dynamics (Bernard-Jannin et al., 2017).

Figure 1. Mesocosm experiment (samples of soil and vegetal cover, not disturbed, 30 cm x 30 cm) to test the effect of plants and atmospheric nitrogen supply on GES fluxes and stocks of C and N

A conceptual hydrologic model was developed, that is suitable to reproduce the evolution of the water level and the dissolved organic carbon concentrations.

Figure 2. Simulated and observed concentrations (average, n=4) in dissolved organic carbon in the pore water of the « La Guette » peatland in the downstream zone (more wet, in blue), and in the upstream zone (drier, in red).

Control of CO2, CH4 and N2O by soil hydrological functioning.

In peatlands, hydrological factors effects on GHG have been studied 1) in mesocosms with a focus on drying/rewetting effects (2011-2015) and 2) in the field where their effect were combined with vegetation restoration treatments (2014- till now). The results showed that high water table, may increase the sink capacity of restored ecosystems by promoting the growth of a specific plant (sphagnum; Gogo et al, 2017, Gogo et al, in prep). Also, results from laboratory experiments simulating changes in thermohydric conditions that have been conducted on cropland soils showed that:

– N2O emission peaks attributed to the reconnection of the pore network occur during rapid soil water desaturation (Rabot et al., 2014; Rabot et al., 2015b). This result has been introduced in a model of N2O emissions from soils (Rabot et al. 2015a) and has been deposited in the INRA VSoil modeling platform (https://www6.inra.fr/vsoil/). Current work (2017-2018) is dedicated to the evaluation of this result at the intra-plot scale (10 m² scale) by rainfall simulations experiments (PhD of F. Poinçot);

– Equivalent N2O emissions occur for 4°C and 16°C temperatures, due to larger N2O reduction at 16°C than at 4°C (Bureau, 2017).

In this area, for agricultural soils, our work initially focused on two axes: i) the link between soil hydric  functioning and N2O emissions, and ii) the soil temperature dynamics and its relations with the GHG emissions. Insofar as the soil structure plays a preponderant role in the soil-water dynamics, we then developed – in connection with the WP3 – an original tool for characterizing the dynamics of the soil structure from monitoring of passive acoustic emissions.

It is known in the literature that N2O emissions in agricultural soils generally occur for soil water situations close to saturation (Water Filled Pore Space> 60%). However, the field data sometimes do not fit with this statement, because N2O measurements are not recorded at a high frequency. To improve our knowledge of the role of soil-water dynamics on N2O emissions by agricultural soils, we have built a multi-step-outflow device, covered by a chamber dedicated to the measurements of gas emissions (Rabot et al., 2016). This device made it possible to tune very precisely the hydric dynamics,  both during the wetting and desiccation phases.

Figure 3. Multi-step outflow device designed to characterize N2O emissions during drying wetting cycles (left) and dynamics of N2O emissions during 2 wetting-drying cycles (right).

Thanks to this device, the high temporal resolution monitoring of N2O emissions on cylinders of undisturbed soil (Ø = 7.5 cm, height = 5 cm) allowed us to highlight intense but fleeting peaks of N2O during the abrupt desaturation of the soil (Rabot et al., 2014). To go further in understanding this phenomenon, we have installed the multistep outflow inside an X-ray tomograph allowing the very rapid acquisition of soil images (about 1 minute for one scan).

Figure 4. Experiment of multistep outflow conducted in the tomograph of the CIRE platform (Centre d’Imagerie pour la Recherche et l’Enseignement) at the INRA center in Nouzilly (37).

The joint analysis of soil structure and N2O emission dynamics allowed us to demonstrate that N2O emission peaks can be attributed to the reconnection of the air-filled pore network to the surface of the sample during its rapid desaturation (Rabot et al., 2015).

Figure 5. Dynamics of N2O emissions recorded during two cycles of wetting (in blue) and drying (in yellow). The graph at the top left shows the evolution of the Euler number that characterizes the connection of the porous network. The emission peaks occur upon reconnection of the air-filled porous network.

Following this analysis of the role of soil hydric dynamics, we examined the role of temperature on N2O emissions. During a controlled temperature laboratory experiment (experiments on undisturbed soil samples in climatic chamber), we observed that the N2O emissions at 16 ° C are not higher than those at 4 ° C, or at realistic temperatures ranging from 4 to 16 ° C (reproducing the diurnal heat cycle.

Figure 6. Temporal dynamics of N2O emissions at different temperatures. With acetylene: the total production by denitrification is measured. Without acetylene: the actual emission is measured (because acetylene inhibits the reduction of N2O to N2).

We demonstrated that this is due to a relative increase in N2O reduction compared to its production that is faster at 16 ° C than at other temperature conditions .Finally the N2O emissions were equivalent to 4 ° C and 16 ° C, due to a greater reduction of N2O at higher temperature. The thermo-hydric dynamics, strongly determinant for N2O emissions (as demonstrated above) depends on the soil structure dynamics. We therefore decided to qualify this dynamics in a non-destructive way. An original passive acoustic wave measurement experiment was implemented thanks to the material acquired by the Labex.

Figure 7. Measuring device for acoustic wave emissions (MISTRAS acquisition unit and piezoelectric sensors).

A desiccation experiment of an undisturbed soil cylinder (loamy-clay soil) (Ø = 7.5 cm, height = 5 cm) was conducted in laboratory controlled conditions. We recorded, over time, i) the acoustic events emitted passively by the ground, ii) the weight of the sample to characterize the water dynamics, and iii) the changes of the surface of the sample by camera.

Figure 8. Characterization of the soil cracking dynamics: -a- surface of the soil cylinder with the acoustic wave detection sensor; -b- analysis of the movement of the soil surface; -c- acoustic events recorded as a function of time. The red arrow symbolizes the sharp increase in acoustic emissions at the beginning of the experiment; the green arrows symbolize the plateau at the end of acoustic emissions.

Analysis of the results shows that the dynamics of the acoustic events is correlated with the dynamics of the water loss and the movements of the sample surface, which allowed us to characterise the dynamics of the structure (Lacoste et al., 2016). These encouraging results made it possible to develop this theme at UR SOLS, and to improve this thematics thanks to an Agreenskills + grant obtained by Marine Lacoste: she made a long-term stay at ETH in Zurich in the group of D.  Or. Her work on acoustic emissions produced by the modification of the soil structure in relation to biological activity was recently published in Scientific Reports (Lacoste, M., Ruiz, S., Gold, D ., 2018. Scientific reports, 8 (1), 10236. DOI: 10.1038 / s41598-018-28582-9).

We have recently initiated works to characterize the isotopy of N2O subjected to reduction. The device was acquired recently, and we are currently working on the qualification of this instrument. At the interface between WP5 and WP6, we extrapolated N2O fluxes measured at the scale of the cultivated plot, to the landscape and territory scales (see results of WP6). At the interface between WP5 and WP4, we analysed the interest of using rhizobia-leguminous pairs to reduce soil N2O emissions (see results of WP4).

Dynamic of contaminants (organic and inorganic) and phytoremediation.

Dynamics of metallic pollutants coupled with the carbon cycle in soils The aim here is to enlighten the role of soil microbial populations in the behavior of inorganic pollutants in presence of organic matter (OM). First, studies with pure bacterial strains of contrasting metabolic profiles showed that organic substances affect their ability to oxidize AsIII into the less mobile AsV form. Then, the influence of OM on the global AsIII-oxidizing activities of complete soil microbial populations was shown to depend on soil characteristics, in particular the intrinsic soil OM concentration (Lescure et al., 2014). A one-year mesocosm study was conducted using an automatically monitored platform device in order to access the impact of water saturation episodes and of the input of bioavailable organic matter on the biogeochemical cycles of C and N, and on the behavior of As and metals in a soil highly contaminated by the destruction of arsenical shells (Thouin et al., 2017). The amorphous phase, which was the primary carrier of As, Zn, and Cu, was unstable under water saturated conditions, whereas the precipitation of mimetite contributed to the immobilization of Pb. The addition of OM contributed to the growth of As transformation microorganisms, and to the transport of As III to the surrounding environment (Thouin et al., 2018).

Figure 9. Tests of As(III)-oxidizing microbial activity on series of polluted soils, in presence of different types and concentrations of organic matter.
Figure 10. PRIME-LABBIO platform to study the dynamic behavior of pollutants in controlled conditions of soil saturation
Figure 11. Design of the PRIME-Labbio device for the study of the dynamic of pollutants in a soil contaminated by the burning of chemical ammunitions (Thouin et al., 2017)

Phytoremediation of soils contaminated with metals and metalloids The efficiency of two phytoremediation options, phytostabilisation and phytoextraction assisted by organic (biochar, compost) and inorganic (zerovalent iron, dolomitic limestone, siderurgical co-products etc.) amendments to address the high concentrations of potentially toxic trace elements (PTTE) such as Cu, Zn, Cr, Cd, Pb, As and Sb in contaminated (techno)sols was assessed. Total dissolved soil pore water concentrations, soil exposure intensity (DGT) and phytoavailability of PTTE were determined and assessed with artificial neural network model. Both assisted phytoremediation options were able to reduce phytoavailability of PTTE (Hattab et al., 2013a, b, 2014a,b,c, 2015,2016 ; Qasim and Motelica, 2014, 2015a,b,2016; Bart et al., 2016; Oustrière 2016,2017). Validation plants/amendments combination efficiency was done through studying the rhizosphere microflora, identifying the roots exsudates and evidencing the influence of these biogeochemical factors on the ecodynamics of the PTTE in mesocosms with raygrass and Salicaceae and biochar amendment. Microbial communities related to As cycle and effects of OM/microorganisms/exudates on PTTE speciation were investigated (Postdoc M.-P. Norini, 2016).

Figure 12. SEM observation and SEM-EDS of an amendment (biochar) in contact with a mining technosoil.
Figure 13. Study of the effect of the rhizosphere of Populus euramericana Dorskamp on the mobility of metals and metalloids in a technosoil in rhizobox (B. Qasim PhD thesis)

Bio-decontamination of soils contaminated by hydrocarbons A non-destructive new methodology for aerobic bio-treatment in situ monitoring of hydrocarbons contaminated aquifers was developed in the frame of the ANR-ECOTECH BIOPHY with the support of Labex Voltaire (PhD and postdoc grants : C. Noël, 2011-2015). Geophysical methods (Electrical Resistivity and Induced Polarization) combined with gas analyses with SPIRIT-LPC2E (CO2 flux with 13C/12C isotopic ratio determination) was used on a BTEX polluted site from a gasoline station (Guimbaud et al., 2016 and in Preparation, Noël et al. 2016a, 2016b). The investigated site is an old gasoline station near Paris contaminated by BTEX hydrocarbons remaining from tanks leak. A bioactive barrier has been set to stimulated aerobic biodegradation by H2O2 liquid injection in the aquifer.

Results. Geophysical measurements (2D tomography), have shown that an active depollution of a contaminated site with hydrocarbons is characterized by a zone of high conductivity (or low resistivity) due to the formation of conductive metabolites (ions in solution) resulting from the biodegradation of hydrocarbons (Technique : Electrical Resistivity Tomography or ERT) and of high chargeability due to the presence of many bacteria behaving like induced dipoles and often present in the form of biofilms (Technique : Time Domain Induced Polarization or DIP) (Noel et al., 2016 a,b)

Geochemical measurements (Flux and δ13C) have shown a good cartographic correlation observed from upstream to downstream the depollution plume between (i) the CO2 flux emitted at soil surface and the BTEX concentration in the aquifer and (ii) the δ13C/12C of CO2 emitted and the underground δ13C/12C of BTEX, with some fractionation factor. Results demonstrate the effectiveness of monitoring a stimulated bio-depollution in real time without excavation of soil matter by measurements of the surface CO2 emission fluxes with δ13C/12C characterization. For the first time, the dynamic of bio-depollution could be quantified from the Rayleigh equations applied on the monitoring of δ13C/12C of the CO2 released at ground surface. CO2 monitoring at ground surface could be a cost effective way to monitor real time biological or chemical treatments of depollution in order to optimize soil bio-treatment (Guimbaud et al., 2016 and in preparation to EST, 2018)

Perspective. Reduction of the costs could be achieved to follow-up studies of depollution from CO2 gas surface analysis and 2D tomography, compared to existing conventional methods using isotopic analysis of pollutants in subsoils by excavation. These new technics could be improved by more investigation on well characterize soils such as the experimental platforms PIVOTS-PRIME (join Region Centre – Europe funded project ARD2020) under construction at BRGM.

Figure 14. On-site gas analyzes and geo-physical measurements

Publications

Bart S., M. Motelica-Heino, F.  Miard, E. Joussein, M. Soubrand, S. Bourgerie, D. Morabito (2016) Phytostabilization of As, Sb and Pb by two willow species (S. viminalis and S. purpurea) on former mine technosols. CATENA 136, 44-52.

Bernard-Jannin, L., Binet, S., Gogo, S., Leroy, F., Défarge, C., Jozja, N., Zocatelli, R., Perdereau, L. and Laggoun-Défarge, F.: Hydrological control of dissolved organic carbon dynamics in a rehabilitated Sphagnum–dominated peatland: a water-table based modelling approach, Hydrology and Earth System Sciences Discuss., 2017, 1–24, doi:10.5194/hess-2017-578, 2017

Buttler A., Robroek B.J.M., Laggoun-Défarge F., Jassey V.E.J., Pochelon C., Bernard G., Delarue F., Gogo S., Mariotte P., Mitchell E.A.D., Bragazza L. (2015). Experimental warming interacts with soil moisture to discriminate plant responses in an ombrotrophic peatland, Journal of Vegetation Science, 26-5: 964–974

Binet S., K. Bru, T. Klinka, S. Touzé, M. Motelica-Heino. Water and Acrylamide monomer transfer rates from a settling basin to groundwaters”, Environmental Science and Pollution Research (2015) 22 (9), 6431-6439

D’Angelo B., Gogo S., Laggoun-Défarge F., Le Moing F., Jégou F., Guimbaud C. (2016). Soil Temperature Synchronisation improves representation of diel variability of Ecosystem Respiration in Sphagnum Peatlands. Agricultural and Forestry Meteorology, 223: 95-102.

De Oliveira T., Guégan R. (2016). Coupled organoclay/micelle action for the adsorption of diclofenac. Environ. Sci. Technol. 50 (18), 10209-10215 (2016).

Delarue F., Buttler A., Bragazza L., Grasset L., Vincent E., Jassey J., Gogo S., Laggoun-Défarge F., Experimental warming differentially affects microbial structure and activity in two contrasted moisture sites in a Sphagnum-dominated peatland. Science of the Total Environment, Elsevier, 2015, 511, pp.576 – 583. <10.1016/j.scitotenv.2014.12.095

Delarue F., Gogo S., Buttler A., Bragazza L., Jassey V.E.J., Bernard G., Laggoun-Défarge F. 2015. Indirect effects of experimental warming on dissolved organic carbon content in subsurface peat, J. Soil & Sediments, 14: 1800-1805

Fialkiewicz-Koziel B., Smieja-Król B., Frontasyeva M., Slowiński M., Marcisz K., Lapshina E., Gilbert D., Buttler A., Jassey V.E.J., Kaliszan K., Laggoun-Défarge F., Kolaczek P., Lamentowicz M. (2016). Anthropogenic- and natural sources of dust in peatland during the Anthropocene. Accepted in Scientific Reports. DOI 10.1038/srep38731

Gogo S., Laggoun-Défarge F., Merzouki F., Mounier S., Guirimand-Dufour A., Jozja N., Huguet A., Delarue F., Défarge C. (2016). In situ and laboratory non-additive litter mixture effect on C dynamics of Sphagnum rubellum and  Molinia caerulea litters. Journal of Soils and Sediments, 16: 13-27.

Gogo S, Leroy F, Bernard-Jannin L, Zocatelli R, Laggoun-Défarge F. Determinism of non-additive litter mixture effect on decomposition : role of the hydric properties of litters. In prep.

Guégan R., M. Giovanela, F. Warmont, M. Motelica-Heino. Nonionic organoclay: A ‘Swiss Army knife’ for the adsorption of organic micro-pollutants? Journal of Colloid and Interface Science (2015), 437, 71–79

Guezennec A.-G., C. Michel, K.Bru, S. Touze, N. Desroche, I. Mnif, M. Motelica-Heino. Transfer and degradation of polyacrylamide based flocculants in hydrosystems: a review”, Environmental Science and Pollution Research (2015), 22 (9), 6390-6406

Guimbaud C., C. Noel, M. Chartier, V. Catoire, M. Blessing, J.C. Gourry, C. Robert, A quantum cascade laser infrared spectrometer for CO2 stable isotope analysis: field implementation at a hydrocarbon contaminated site under bio-remediation; Journal of Environmental Sciences, special issue “Changing complexity of air pollution”, 40, 60-74, 2016.

Guimbaud C., C. Noel, E. Verardo, A. Grossel, F. Jégou, Z. Hu, C. Robert, J. Jacob, I. Ignatiadis, J.C. Gourry, A new approach to quantify the dynamics of in situ biodegradation of hydrocarbons in a contaminated aquifer by CO2 13C monitoring at ground surface, in preparation to “Environmental Science & Technology”.

Hattab N., M. Motelica-heino, X. Bourrat, O. Faure, J.L. Bouchardon. Phytostabilization of techno-soils contaminated with high concentration of trace elements assisted by fresh and mature organic amendments. Journal of Environmental Management (2015) 159, 37-47

Hattab-Hambli N., M. Motelica-Heino, M. Mench (2016) Aided phytoextraction of Cu, Pb, Zn, and As in copper-contaminated soils with tobacco and sunflower in crop rotation: Mobility and phytoavailability assessment. Chemosphere 145, 543-550.

Iconaru S., Guégan R., Popa C., Motelica-Heino M., Ciobanu C., Predoi D. (2016). Novel magnetite (Fe3O4) nanoparticles as adsorbents for As and Cu removal. Applied Clay Science (2016), 134, 128-135.

Huguet A., Meador T.B., Laggoun-Défarge F., Könneke M., Derenne S., Hinrichs K.U. (2017). Production rates of bacterial tetraether lipids and fatty acids in peatland under varying oxygen concentrations. Geochimica et Cosmochimica Acta, 203: 103-116. https://doi.org/10.1016/j.gca.2017.01.012

Lacoste, M., Ruiz, S., Or, D., (2018) Listening to earthworms burrowing and roots growing – acoustic signatures of soil biological activity. Scientific Reports, 8 (1), 10236. DOI : 10.1038/s41598-018-28582-9

Laggoun-Défarge F., Gogo S., Bernard-Jannin L., Guimbaud C., Zocatelli R., Rousseau J., Binet S., D’Angelo B., Leroy F., Jozja N., Le Moing F., Défarge C. (2016) Does hydrological restoration affect greenhouse gases emission and plant dynamics in Sphagnum peatlands? Mires & Peat.

Le Forestier L., M. Motelica-Heino, P.  Le Coustumer, M. Mench. Phytostabilisation of a copper contaminated topsoil aided by basic slags: assessment of Cu mobility and phytoavailability. Journal of Soils and Sediments (2015) accepté doi 10.1007/s11368-015-1299-8

Leroy F., Gogo S., Guimbaud C., Bernard-Jannin L., Hu Z., Laggoun-Défarge F. (2017). Vegetation composition controls temperature sensitivity of CO2 and CH4 emissions and DOC concentration in peatlands. Soil Biology and Biochemistry : 107 : 164-167.

Leroy, F., Gogo, S., Buttler, A., Bragazza, L., & Laggoun-Défarge, F. (2017). Litter decomposition in peatlands is promoted by mixed plants. Journal of Soils and Sediments, 1-11. DOI https://doi.org/10.1007/s11368-017-1820-3

Leroy F., Gogo, S. Guimbaud, C., Bernard-Jannin, L., Yin, X., Belot, G., Shuguang , W.; Laggoun-Défarge, F. Carbon balance and global warming potential modifications in Sphagnum-dominated peat mesocosms invaded by Molinia caerulea. Biogeosciences Discuss. (ms under review) https://doi.org/10.5194/bg-2017-423

Leroy F., Gogo, S. Guimbaud, C., Francez A.J., Zocatelli R., Défarge C., Bernard-Jannin L., Hu Z., Laggoun-Défarge F. Response of C and N cycles to N fertilization in Sphagnum and Molinia-dominated peat mesocosms. Journal of Environmental Science (accepté avec modifications mineures)

Leroy F, Gogo S, Guimbaud C, Bernard-Jannin L, Hu Z, Laggoun-Défarge F. Response of C and N cycles to N fertilization in Sphagnum and Molinia-dominated peat mesocosms. Sous presse à Journal of Environmental Sciences.

Lescure T., Moreau J., Charles C., Ben Ali Saanda T., Thouin H., Pillas  N., Bauda P., Lamy I., Battaglia-Brunet F. (2015) Influence of organic matters on AsIII oxidation by the microflora of polluted soils. Environ Geochem Health. DOI 10.1007/s10653-015-9771-3

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