Influence de la dégradation des matières organiques et du couvert végétal sur la composition isotopique du carbone organique dissous : le cas des alocrisols forestiers du Morvan

National audience; Pour étudier les processus de production et de transfert des matières organiques dissoutes (MOD) dans les sols et dans les hydrosystèmes, il est essentiel de définir des traceurs de l’origine des MOD. La composition en isotopes stables du carbone (13C/12C) est un marqueur potentiel des processus producteurs de MOD. De fait, des études récentes ont montré que la composition isotopique du carbone organique dissous (COD) dans des solutions de sols forestiers en région tempérée présentaient un enrichissement en 13C de 1 à 2 ‰ par rapport à la composition isotopique des MOS, en fonction des saisons et/ou du type de couverture végétale (Kaiser et al., 2001 ; Andreux et al., 200…

Influence of soil organic status on the dynamics and impact of copper on microbial communities in a vineyard soil

International audience

History and environmental impact of mining activity in Celtic Aeduan territory recorded in a peat-bog (Morvan – France)

International audience; The present study aims to document early mining and smelting activities by means of geochemical and pollen analyses performed in a peat-bog core collected around the Bibracte oppidum (Morvan, France), the largest settlement of the great Aeduan Celtic tribe (ca 180 BC -25 AD). The anthropogenic Pb profile indicates local mining operations starting from the Late Bronze Age, ca cal. 1400-1300 BC. Lead inputs peaked at the height of Aeduan civilization, and then decreased after the Roman conquest of Gaul, when the site was abandoned. Other phases of mining are recognised from the 11th century to Modern Times. They have all led to modifications in plant cover, probably re…

Evaluation of the addition of fertilizing component on microbial communities and decomposition of organic matter in soil

Organic matter (OM) influences many of the soil functions and occupies a central position in the global carbon cycle. At the scale of the agro-ecosystem, primary productivity is dependent on the recycling of soil organic matter (SOM) by the action of decomposers (mainly bacteria and fungi), which mineralize organic compounds, releasing the nutrients needed for plant growth. At a global scale, the recycling of the SOM determines the carbon flux between soil and atmosphere, with major consequences in terms of environmental quality. In this context, the management of SOM stocks in agro-ecosystems is a major issue from which depend the maintenance of the productivity and sustainability of agric…

Sedimentation and tropical vegetation changes in Southern Benin (West Africa), carbon-13 tracing of organic matter dynamics and fluctuations of the sea level during the last 7,000 years.

12 pages; International audience

Assessing the transfer of pentachlorophenol through soil columns using 13[C]isotope

Abstract The transfer of organic pollutants was studied through soil columns using 13 [C]-labelled pentachlorophenol (PCP) as a model compound. The organic carbon content and the 13 [C]/ 12 [C] ratio were measured in two soil sections, 0–3 cm and 3–6 cm, and in percolated water using an Elemental Analyser coupled with a Magnetic Mass Sector. The mass balance of carbon was evaluated and the amount of PCP was calculated in each compartment of the soil–water systems. The results show that more than 80% of the PCP-derived 13 [C] remained in the upper layer of the soil column. Approximately 20% was transferred to the lower soil layer, and less than 1% was found in the water leachates. The 13 [C]…

13C differentiation of dissolved organic carbon pool during carbon mineralization in soil from a native deciduous forest and a coniferous plantation

International audience

13C Differentiation between Dissolved and Solid Organic Carbon in Soils as Induced by Substitution of a Native Deciduous Forest by a Coniferous Forest

International audience

Influence of15N enrichment on the net isotopic fractionation factor during the reduction of nitrate to nitrous oxide in soil

5 pages; International audience; Nitrous oxide, a greenhouse gas, is mainly emitted from soils during the denitrification process. Nitrogen stable-isotope investigations can help to characterise the N(2)O source and N(2)O production mechanisms. The stable-isotope approach is increasingly used with (15)N natural abundance or relatively low (15)N enrichment levels and requires a good knowledge of the isotopic fractionation effect inherent to this biological mechanism. This paper reports the measurement of the net and instantaneous isotopic fractionation factor (alpha(s/p) (i)) during the denitrification of NO(3) (-) to N(2)O over a range of (15)N substrate enrichments (0.37 to 1.00 atom% (15)…

The relationship between copper accumulated in vineyard calcareous soils and soil organic matter and iron

Summary The intensive use for over 100 years of copper sulphate (Bordeaux mixture) to fight mildew in vineyards has led to a substantial accumulation of copper (Cu) in surface soils. To assess the effects of such large concentrations, the surface soils of 10 Burgundy vineyards were sampled and analysed for total organic matter (carbon and nitrogen) and metal (copper and iron) contents. Physical (i.e. size fractionation) and chemical (sequential extraction) methods were used to determine the distribution of these elements. The most Cu-contaminated plots showed the largest accumulation of organic carbon and Cu in the coarse sand and fine sand fractions. Copper was strongly correlated with org…

Différenciation isotopique (13C) du carbone organique dissous (COD) au cours de la dégradation des matières organiques dans les sols forestiers : influence de la végétation

National audience

Measurements ofWγandZγproduction inppcollisions ats=7  TeVwith the ATLAS detector at the LHC

The integrated and differential fiducial cross sections for the production of a W or Z boson in association with a high-energy photon are measured using pp collisions at root s = 7 TeV. The analyse ...

Copper Dynamics and Impact on Microbial Communities in Soils of Variable Organic Status

International audience; The effect of soil organic status on copper impact was investigated by means of a microcosm study carried out on a vineyard soil that had been amended with varying types of organic matter during a previous long-term field experiment. Soil microcosms were contaminated at 250 mg Cu kg−1 and incubated for 35 days. Copper distribution and dynamics were assessed in the solid matrix by a sequential extraction procedure and in the soil solution by measuring total and free exchangeable copper concentrations. Copper bioavailability was also measured with a whole-cell biosensor. Modifications of microbial communities were assessed by means of biomass-C measurements and charact…

Evaluation of the effect of an additional fertilizer on the dynamics of microbial community and the decomposition of organic matter in soil

Organic matter (OM) influences many of the soil functions and occupies a central position in the global carbon cycle. At the scale of the agro-ecosystem, primary productivity is dependent on the recycling of soil organic matter (SOM) by the action of decomposers (mainly bacteria and fungi), which mineralize organic compounds, releasing the nutrients needed for plant growth. At a global scale, the recycling of the SOM determines the carbon flux between soil and atmosphere, with major consequences in terms of environmental quality. In this context, the management of SOM stocks in agro-ecosystems is a major issue from which depend the maintenance of the productivity and sustainability of agric…

Organic carbon dynamics in soil particle-size separates of sandy Spodosols when forest is cleared for maize cropping

Summary In southwest France, much of the forest lands on sandy Spodosols has been converted to continuous maize cropping in the last few decades. To evaluate the impacts of such change on the content and properties of the soil organic matter, we compared the amount of organic carbon and 13C natural abundance in soil and particle-size separates at three locations, selected on the basis of different contents of 0–50 μm particles (clay + silt). After three decades of cultivation, the amount of carbon from the forest pools (Cf) decreased by about 60%, attributable mainly to easily degradable material in sand-sized fractions (−70%). However, a recalcitrant residue remained in soil at a constant …

Élevage et forêt sur la montagne dijonnaise à la fin du Moyen Âge. Deux établissements forestiers d’éleveurs en Terre de Saint-Seine Saint-Martin-du-Mont (Côte d’Or)

International audience

Etude et gestion des processus biogéochimiques couplant les cycles du carbone et de l'azote à l'origine de la libération de composés polluants, du sol vers les compartiments eau et air de l'environnement

13C differentiation of the dissolved organic carbon pool during carbon mineralization in soil from a native deciduous forest and a coniferous plantation

International audience

Effet du statut organique des sols pollués sur la dynamique et l'impact du cuivre sur les communautés microbiennes

National audience; L’effet du statut organique des sols (SOS) sur l’impact du cuivre a été évalué par une approche en microcosmes et lysimètres d’un sol de vigne amendé en diverses matières organiques lors d’une expérience de terrain de long terme. Des microcosmes et des lysimètres du sol de vigne ont été contaminés à 240 mg Cu kg-1 et incubés à 23°C pendant 12 mois. La distribution et la dynamique du cuivre ont été caractérisées par fractionnement granulométrique et spéciation solide en extraction séquentielles et par spéciation liquide par mesure de concentration de cuivre échangeable total (ICP-AES), libre (électrode sélective) et biodisponible (biosensor). L’impact du cuivre sur les com…

Photoinductive efficiency of soil extracted humic and fulvic acids

Humic and fulvic acids extracted from soils of different genesis were investigated for their ability to photoinduce the transformation of fenuron (2 x 10(-4) mol(-1)) at 365 nm. The ratio of the initial rate of fenuron consumption over the rate of light absorption by humic substances was found to be higher for fulvic acids (range 2.0 x 10(-3) to 9.0 x 10(-5)) than for humic acids (range 1.7 x 10(-4) to - 3.6 x 10(-5)). Within the FAs population, this ratio decreased as the specific absorption coefficient at 365 nm increased. It seems therefore that most of 365-nm absorbing components have no photoinductive activity and even reduce that of photoinductive chromophores.

Shifts in microbial diversity through land use intensity as drivers of carbon mineralization in soil

10 pages; International audience; Land use practices alter the biomass and structure of soil microbial communities. However, the impact of land management intensity on soil microbial diversity (i.e. richness and evenness) and consequences for functioning is still poorly understood. Here, we addressed this question by coupling molecular characterization of microbial diversity with measurements of carbon (C) mineralization in soils obtained from three locations across Europe, each representing a gradient of land management intensity under different soil and environmental conditions. Bacterial and fungal diversity were characterized by high throughput sequencing of ribosomal genes. Carbon cycl…

Variations in soil-water use by grapevine according to plant water status and soil physical-chemical characteristics - A 3D spatio-temporal analysis.

14 pages; International audience; Understanding plant and soil-water relationships is crucial to optimise agricultural management. In this multidisciplinary work, soil geophysics and plant physiological measurements are coupled and a statistical method is proposed to visualising plant soil-water uptake in space and time. The method is applied in a vineyard context and shows differences in the use of tranpirable soil water by grapevine according to the type of soil and the time of the day (day/night).During two years the water stress experienced by a single Chardonnay/SO4 grapevine clone was monitored both at pre-dawn and midday by leaf water potentials in two field plots exclusively differe…

Le traçage isotopique pour étudier la production par les microorganismes du sol d'oxyde nitreux, gaz à effet de serre.

Domaine SCIENCES DE L’ALIMENT ET AGRO-ENVIRONNEMENT

13C composition of dissolved organic carbon in upland forested catchments of the Morvan Mountains (France): Influence of coniferous and deciduous vegetation.

10 pages; International audience; One of the main environmental changes caused by human activities is that of land use. These changes influence the quantity and quality of the dissolved organic matter (DOM) fluxes through the vegetation–soil–stream system. The aim of this work is to evaluate the influence of the substitution of native deciduous forests by well managed coniferous forests on dissolved organic carbon (DOC) fluxes and their associated carbon isotopic composition (d13CDOC). DOC fluxes and d13CDOC were monitored for 2 years in the streams of four similar upland forested catchments in the Morvan Mountains (France). Mean annual DOC concentrations and fluxes were 2–4 times lower in …

Dynamics and identification of soil microbial populations actively assimilating carbon from 13C-labelled wheat residue as estimated by DNA- and RNA-SIP techniques.

International audience; This work is the first report on the use of DNA-, RNA-SIP approaches to elucidate the dynamics and the diversity of bacterial populations actively assimilating C derived from plant residues labelled at more than 90% (13)C. Wheat-residues, were incorporated and incubated into soil microcosms for 28 days. At the end of the incubation time, no more than 55% of the total CO(2) released was (13)C-labelled, suggesting the occurrence of an important priming effect process. After 7 days, more than 30% of the whole DNA extracted were labelled, allowing an efficient separation of labelled from unlabelled DNA using density gradient centrifugation. The genetic structure of bacte…

Emissions and spatial variability of N2O, N2 and nitrous oxide mole fraction at the field scale, revealed with 15N isotopic techniques.

Abstract The accurate measurement of nitrous oxide (N 2 O) and dinitrogen (N 2 ) during the denitrification process in soils is a challenge which will help to estimate the contribution of soil N 2 O emissions to global warming. Oxygen concentration, nitrate concentration and carbon availability are generally the main factors that control soil denitrification rate and the amount of N 2 O or N 2 emitted. The aim of this paper is to present a database of the N 2 O mole fraction measured at the field scale, and to test hypotheses concerning its regulation. A 15 N-nitrate tracer solution was added to 36 undisturbed soil cores on a 20 m×20 m cultivated field plot. Fluxes of CO 2 , N 2 O and N 2 f…

Measurements of spin correlation in top-antitop quark events from proton-proton collisions ats=7  TeVusing the ATLAS detector

Measurements of spin correlation in top quark pair production are presented using data collected with the ATLAS detector at the LHC with proton-proton collisions at a center-of-mass energy of 7 TeV, corresponding to an integrated luminosity of 4.6 fb(-1). Events are selected in final states with two charged leptons and at least two jets and in final states with one charged lepton and at least four jets. Four different observables sensitive to different properties of the top quark pair production mechanism are used to extract the correlation between the top and antitop quark spins. Some of these observables are measured for the first time. The measurements are in good agreement with the Stan…

Quantifying the contribution of nitrification and denitrification to the nitrous oxide flux using 15N tracers.

8 pages; International audience; Microbial transformations of nitrification and denitrification are the main sources of nitrous oxide (N2O) from soils. Relative contributions of both processes to N2O emissions were estimated on an agricultural soil using 15N isotope tracers (15NH4+ or 15NO3-), for a 10-day batch experiment. Under unsaturated and saturated conditions, both processes were significantly involved in N2O production. Under unsaturated conditions, 60% of N-N2O came from nitrification, while denitrification contributed around 85-90% under saturated conditions. Estimated nitrification rates were not significantly different whatever the soil moisture content, whereas the proportion o…

High microbial diversity promotes soil ecosystem functioning

ABSTRACT In soil, the link between microbial diversity and carbon transformations is challenged by the concept of functional redundancy. Here, we hypothesized that functional redundancy may decrease with increasing carbon source recalcitrance and that coupling of diversity with C cycling may change accordingly. We manipulated microbial diversity to examine how diversity decrease affects the decomposition of easily degradable (i.e., allochthonous plant residues) versus recalcitrant (i.e., autochthonous organic matter) C sources. We found that a decrease in microbial diversity (i) affected the decomposition of both autochthonous and allochthonous carbon sources, thereby reducing global CO 2 e…

Water-extractable organic matter linked to soil physico-chemistry and microbiology at the regional scale

10 pages; International audience; A better understanding of the links between dissolved organic matter and biogeochemical processes in soil could help in evaluating global soil dynamics. To assess the effects of land cover and parental material on soil biogeochemistry, we studied 120 soil samples collected from various ecosystems in Burgundy, France. The potential solubility and aromaticity of dissolved organic matter was characterised by pressurised hot-water extraction of organic carbon (PH-WEOC). Soil physico-chemical characteristics (pH, texture, soil carbon and nitrogen) were measured, as was the δ13C signature both in soils and in PH-WEOC. We also determined bacterial and fungal abund…

C4 plant isotopic composition (delta13C) evidence for urban CO2 pollution in the city of Cotonou, Benin (West Africa).

9 pages; International audience; The carbon isotopic composition (delta13C) of plants can reveal the isotopic carbon content of the atmosphere in which they develop. The delta13C values of air and plants depend on the amount of atmospheric fossil fuel CO2, which is chiefly emitted in urban areas. A new indicator of CO2 pollution is tested using the delta13C variation in a C4 grass: Eleusine indica. A range of about 4 per thousand delta units was observed at different sites in Cotonou, the largest city in the Republic of Benin. The highest delta13C values, from -12 per thousand to -14 per thousand, were found in low traffic zones; low delta13C values, from -14 per thousand to -16 per thousan…

Isotopic Differentiation (13C) of Dissolved Organic Carbon and CO2 During Organic Matter Degradation in Forest Soils: Influence of Vegetation

International audience

Spatio-temporal analysis of grapevine water behaviour in hillslope vineyards. The example of Corton hill, Burgundy.

6 pages; International audience

The organic carbon derived from sewage sludge as a key parameter determining the fate of trace metals.

8 pages; International audience; In a sandy agricultural soil of south-west of France, continuously cultivated with maize and amended with sewage-sludge over 20 years, the behavior of three trace metals (Cu, Pb, and Zn) was studied during the sludge applications (1974-1993) and after its cessation (1993-1998). Using the delta13C analysis, the dynamics of different sources of organic matter were followed in order to elucidate the influence of the sludge-derived organic matter on the fate of trace metals in the soil and its particle size fractions. This study revealed that sludge-derived organic matter contributed to the formation of macroaggregates through the binding of preexisting microagg…

The use of soil electrical resistivity to monitor plant and soil water relationships in vineyards

Abstract. Soil water availability deeply affects plant physiology. In viticulture it is considered as a major contributor to the "terroir" expression. The assessment of soil water in field conditions is a difficult task especially over large surfaces. New techniques, are therefore required to better explore variations of soil water content in space and time with low disturbance and with great precision. Electrical Resistivity Tomography (ERT) meets these requirements, for applications in plant sciences, agriculture and ecology. In this paper, possible techniques to develop models that allow the use of ERT to spatialise soil water available to plants are reviewed. An application of soil wate…

Distribution, biodisponibilité, dynamique et impact du cuivre sur les communautés microbiennes dans les sols de vigne. Effet du statut organique des sols

National audience

Erosion of biodiversity affects the stability of soil microbial communities

Anthropogenic activities have led to a significant modification/reduction of biodiversity. By observing this erosion, the understanding of the relationship between biodiversity and ecosystem functioning has emerged as a central issue in ecological and environmental sciences during the last decade. This relationship between diversity-stability-function has been extensively studied by plant ecologists, but remains largely unexplored for soil microorganisms. In this context, we studied the impact of an erosion of biodiversity on the stability of soil microbial communities (i.e. resistance and resilience) in response to two perturbations: a residual metallic stress (mercury input at 20 ppm) and…

Influence of microbial diversity on soil organic carbon dynamics highlighted by a 13C-labelling technique

Soil organic matter (SOM) represents the main pool of carbon within the biosphere, estimated at roughly twice that in atmospheric CO2. In agrosystems, organic amendments are common to maintain soil C stocks. However, recent studies have revealed that these practices can lead to a priming effect, corresponding to enhanced release of CO2 into the atmosphere, due to over-mineralisation of soil organic carbon. Therefore, appropriate decisions regarding organic input management require better understanding of the biogeochemical cycles related to SOM dynamics. As soil microorganisms are major actors in SOM turnover, their diversity is likely to influence SOM dynamics. In this context, the relatio…

Stability of soil microbial structure and activity depends on microbial diversity

Despite the central role of microbes in soil processes, empirical evidence concerning the effect of their diversity on soil stability remains controversial. Here, we addressed the ecological insurance hypothesis by examining the stability of microbial communities along a gradient of soil microbial diversity in response to mercury pollution and heat stress. Diversity was manipulated by dilution extinction approach. Structural and functional stabilities of microbial communities were assessed from patterns of genetic structure and soil respiration after the stress. Dilution led to the establishment of a consistent diversity gradient, as revealed by 454 sequencing of ribosomal genes. Diversity …

Impact of changing forest management on soil organic matter in low mountain acid media

The impacts of changes in vegetation cover from native deciduous forest to Douglas fir ( Pseudotsuga menziesii Franco) and of human activity on soil organic matter (SOM) characteristics were studied in two low mountain areas of east-central France. No striking difference in soil type (Dystric Cambisol) was found between the two sites. Humus-rich horizons were of the “Dysmull” and “Moder” types, regardless of the nature of the bedrock. Contrary to a common affirmation concerning other coniferous species, Douglas fir had no negative effect on soil pH and humification degree of SOM, with respect to the native beech vegetation. Pruning and partial clearing slightly improved humification, espect…

A comparison of extraction procedures for water-extractable organic matter in soils

The characteristics of dissolved organic matter (DOM) in soils are often determined through laboratory experiments. Many different protocols can be used to extract organic matter from soil. In this study, we used five air-dried soils to compare three extraction methods for water-extractable organic matter (WEOM) as follows: (i) pressurised hot-water-extractable organic carbon (PH-WEOC), a percolation at high pressure and temperature; (ii) water-extractable organic carbon (WEOC), a 1-hour end-over shaking; and (iii) leaching-extractable organic carbon (LEOC), a leaching of soil columns at ambient conditions. We quantified the extraction yield of organic carbon; the quality of WEOM was charac…

: J. Sci. Food Agric.

Background: The measurement of carbon isotopic discrimination in grape sugars at harvest (δ13 C) is an integrated assessment of water status during ripening. It is an efficient alternative to assess variability in the field and discriminate between management zones in precision viticulture, but further work is needed to completely understand the signal.; Results: This work, spanning over 3 years, performed in a hillslope toposequence in Burgundy, delineates the relationships between main soil properties (gravel amount, slope, texture) and the grapevine water status assessed by δ13 C. The highest δ13 C, indicating most severe water deficit, was recorded in gravelly soils on steep slopes. The…

Variations du stockage et de la dynamique de la matière organique en fonction de l'utilisation des sols dans les savanes du Rift éthiopien.

13 pages; International audience

La perte de diversité affecte la stabilité structurelle et fonctionnelle des communautés microbiennes du sol

Les activités anthropiques impactent fortement la diversité des communautés microbiennes du sol. La question se pose de savoir dans quelle mesure ces modifications de diversité peuvent remettre en cause la capacité des sols à assurer les services dont dépendent les sociétés humaines. Pour répondre à cette question, une meilleure compréhension de la relation diversité-stabilité-fonction est indispensable. En 1999, Yachi et Loreau développent le concept d'assurance écologique selon laquelle une forte diversité d'espèces dans un écosystème permet une meilleure stabilité de son fonctionnement. Cette relation a largement été étudié chez les végétaux mais reste encore inconnue chez les microorgan…

Long-term effects of metal-containing farmyard manure and sewage sludge on soil organic matter in a fluvisol

Abstract Our aim was to establish the long-term effects of repeated applications after 20 y of organic amendments (farmyard manure at 10 t ha −1  y −1 , and urban sewage sludge at two different rates, 10 t ha −1  y −1 and 100 t ha −1 every 2 y) on the quality of a sandy and poorly buffered soil (Fluvisol, pH 6). Chemical characteristics and biodegradability of the labile organic matter, which is mainly derived from microbial biomass and biodegradation products of organic residues, were chosen as indicators for soil quality. The organic C content had reached a maximal value (30.6 g C kg −1 in the 100 t sludge-treated soil), i.e. about 2.5 times that in the control. Six years after the last a…

History and Environmental Impact of Mining Activity in Celtic Aeduan Territory Recorded in a Peat Bog (Morvan, France)

The present study aims to document historical mining and smelting activities by means of geochemical and pollen analyses performed in a peat bog core collected around the Bibracte oppidum (Morvan, France), the largest settlement of the great Aeduan Celtic tribe (ca. 180 B.C. to 25 A.D.). The anthropogenic Pb profile indicates local mining operations starting from the Late Bronze Age, ca. cal. 1300 B.C. Lead inputs peaked at the height of Aeduan civilization and then decreased after the Roman conquest of Gaul, when the site was abandoned. Other phases of mining are recognized from the 11th century to modern times. They have all led to modifications in plant cover, probably related in part to…

Monitoring soil volume wetness in heterogeneous soils by electrical resistivity. A field-based pedotransfer function.: A field-based pedotransfer function

11 pages; International audience; Modern irrigation techniques require accurate, rapid, cost-effective, spatial measurement of soil moisture. Electrical Resistivity Tomography (ERT) meets most of these requirements, but needs to be calibrated for each use because it is very sensitive to differences in soil characteristics. In this study, a pedotransfer function approach is used to remove the need for site-specific calibration, allowing ERT to be used directly to measure soil moisture. The study site was a hillslope vineyard, where eight calcaric-cambisol soil profiles were identified. From 2012 to 2013, 23 000 soil volume wetness measurements were acquired by Time Domain Reflectometry, and …

Contamination of soil by copper affects the dynamics, diversity, and activity of soil bacterial communities involved in wheat decomposition and carbon storage.

ABSTRACT A soil microcosm experiment was conducted to evaluate the influence of copper contamination on the dynamics and diversity of bacterial communities actively involved in wheat residue decomposition. In the presence of copper, a higher level of CO 2 release was observed, which did not arise from greater wheat decomposition but from a higher level of stimulation of soil organic matter mineralization (known as the priming effect). Such functional modifications may be related to significant modifications in the diversity of active bacterial populations characterized using the DNA stable-isotope probing approach.

Evidence of organic contamination in urban soils of Cotonou town (Benin).

14 pages; International audience; In Cotonou (Benin), growth of the population leads to an excessive use of natural resources, inducing organic contaminations. Surface soils collected in the town, were extracted and fractionated by liquid chromatography in three families: aliphatic, aromatic hydrocarbons and polar fractions. Each fraction was characterized by gas chromatography-mass spectrometry. All the results show that an anthropogenic input exists (waste oils). Indeed, aliphatic hydrocarbons have specific markers emphasizing the presence of petrogenic products: UCM (unresolved complex mixture), specific distribution of pentacyclic triterpane. However, specific molecular biomarkers revea…

Dynamics of copper and zinc sedimentation in a lagooning system receiving landfill leachate.

9 pages; International audience; This study characterises the sediment dredged from a lagooning system composed of a settling pond and three lagoons that receive leachates from a municipal solid waste (MSW) landfill in France. Organic carbon, carbonate, iron oxyhydroxides, copper (Cu) and zinc (Zn) concentrations were measured in the sediment collected from upstream to downstream in the lagooning system. In order to complete our investigation of sedimentation mechanisms, leachates were sampled in both dry (spring) and wet (winter) seasonal conditions. Precipitation of calcite and amorphous Fe-oxyhydroxides and sedimentation of organic matter occurred in the settling pond. Since different di…

Distribution and sources of bulk organic matter (OM) on a tropical intertidal mud bank in French Guiana from elemental and isotopic proxies

International audience; The mobile French Guiana coast is a shoreface region downdrift of the Amazon River, where enormous quantities of inorganic and organic materials are exchanged with the Atlantic Ocean. The rapid accumulation of these materials forms highly unstable shore-attached mud banks, which can be temporally emerged and then rapidly colonized and stabilized by microphytobenthos and opportunistic mangroves (i.e. Avicennia germinans). Mud banks are preferential sites for the accumulation and significant remineralization of organic matter (OM) due to intense erosion/deposition cycles and potential biological colonization. The distribution and sources of bulk sedimentary OM were cha…

Long-term mineral fertiliser use and maize residue incorporation do not compensate for carbon and nutrient losses from a Ferralsol under continuous maize–cotton cropping

9 pages; International audience; It has been repeatedly argued that mineral fertiliser application combined with in situ retention of crop residue biomass can sustain long-term productivity of West African soils. Using 20-year experimental data from southern Togo, a biannual rainfall area, we analysed the effect of two rates of mineral NPK fertiliser application to maize–cotton rotation on the long-term dynamics of soil C and nutrient contents, as compared with two control treatments. Mineral fertiliser treatments consisted of application to both maize (first season) and cotton (second season) the research-recommended NPK rates (Fertiliser-RR) and 1.5 times these rates (Fertiliser-1.5 RR). …

Relation entre mode d’usage agronomique, diversité microbienne et turn-over des matières organiques dans le sol

Affiche, résumé; International audience

Effect of temperature on soil microbial structure and fractionation during C mineralisation

International audience; Microbial carbon mineralization in soils leads to the production of different gaseous or dissolved components that have environmental impacts. Our study deals with the influence of soil temperature on the production of gaseous and dissolved carbon components during carbon mineralization in forest soils in France. After an incubation of soil samples for 42 days at 4 different temperatures, we determined both size and 13C isotopic signature of dissolved organic carbon and CO2 pools. We also characterised the soil microbial community structure (PLFA profiles). While temperature clearly increases the CO2 production, a low decrease of the dissolved organic carbon pool was…