Mélanie Davranche

Mélanie Davranche
Université de Rennes 1 | UR1 · UMR CNRS 6118 - Géosciences Rennes

professor

About

139
Publications
16,359
Reads
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3,998
Citations
Additional affiliations
September 2015 - present
Université de Rennes 1
Position
  • Professor
September 2001 - August 2015
Université de Rennes 1
Position
  • Professor (Assistant)
September 1996 - September 2000
University of Limoges
Position
  • Ph. D.

Publications

Publications (139)
Article
The nanoplastics presence in the ocean and soil demonstrates their global distribution in the environment. Due to their colloidal properties, nanoplastics could influence trace metal speciation in natural matrices, which...
Article
Full-text available
It has long been considered that ferric phases stabilize organic matter (OM) in soils. Temporarily waterlogged soils, in which Fe is submitted to regular reductive solubilization and oxidizing precipitation, have often been used to study these processes. However, few studies have been interested in the evolution of the OM quality under such conditi...
Article
Microplastics from the North Atlantic Gyre deposited on Guadeloupe beaches were sampled and characterized. A new method is developed to identify which elements were present as additives in these microplastics. The method used both acidic leaching and acidic digestion. Several elements (Al, Zn, Ba, Cu, Pb, Cd, Mn, Cr) were identified as pigments. Fu...
Presentation
Presentation for the French conference GDR Polymères et Océans
Article
Rare earth elements (REE) naturally occur at trace levels in natural systems but, due to their increasing use in modern technologies, they are now released into the environment, and considered as emerging contaminants. Therefore, the development of numerical predictive models of their speciation in various physico-chemical conditions is required to...
Article
Iron (Fe) isotopes are now recognized as useful tracers of Fe sources and biogeochemical processes in natural environments but many uncertainties remain regarding the mechanisms that control their isotopic fractionation. Ultrafiltration techniques applied to separate Fe species could potentially bias Fe isotopic compositions. Here, we investigated...
Article
Full-text available
Although redox reactions are recognized to fractionate iron (Fe) isotopes, the dominant mechanisms controlling the Fe isotope fractionation and notably the role of organic matter (OM) are still debated. Here, we demonstrate how binding to organic ligands governs Fe isotope fractionation beyond that arising from redox reactions. The reductive biodis...
Article
More environmentally relevant nanoplastic models are urgently needed. Models of environmental plastics are used to develop analytical methods to get an accurate picture of how nanoplastics behave in natural systems,...
Article
Environmental iron-organic matter (Fe-OM) aggregates play a major role in the dynamic of pollutants. Nowadays, there is a lack of information about the control exerted by their structural organization on their reactivity towards metal(loid)s and in particular, the impact of major ions, such as calcium. The sorption capacity of mimetic environmental...
Article
The occurrence of nanoplastics in the environment is now known and presents new threats linked to plastic debris issues. New questions about the formation pathways and life cycle assessment of nanoplastics in continental and marine environments have been raised. In the present study, we focused on the Guadeloupe island coastal system. For the first...
Article
Iron-organic matter (Fe-OM) aggregates are a key factor in the control of pollutant mobility. Their physical and structural organization depends on the prevailing physicochemical conditions during their formation and on subsequent exposure to variations in porewater goechemistry. Among these conditions, calcium (Ca) could be a major parameter given...
Article
While several studies have investigated the potential impact of nanoplastics, proof of their occurrence in our global environment has not yet been demonstrated. In the present work, by developing an innovative analytical strategy, the presence of nanoplastics in soil was identified for the first time. Our results demonstrate the presence of nanopla...
Article
Electron transfer in the critical zone is driven by biotic and abiotic mechanisms and controls the fate of inorganic and organic contaminants, whether redox-sensitive or not. In these environments, Fe- and Mn-bearing minerals, as well as organic matter, are key compounds. They interact with each other and constitute important electron shuttles. As...
Article
In wetlands, stream riverbanks represent a large redox reactive front. At their surface, ferric deposits promote their capacity to trap nutrients and metals. Given that rare earth elements (REE) are now considered as emerging pollutants, it seems that the riverbank interface is a strategic area between wetlands and streams in terms of controlling t...
Article
Full-text available
A microfluidic laboratory recently opened at Synchrotron SOLEIL, dedicated to in-house research and external users. Its purpose is to provide the equipment and expertise that allow the development of microfluidic systems adapted to the beamlines of SOLEIL as well as other light sources. Such systems can be used to continuously deliver a liquid samp...
Article
The oxidation of magnetite into maghemite and its coating by natural organic constituents are common changes that affect the reactivity of iron oxide nanoparticles (IONP) in aqueous environments. Certain ubiquitous compounds such as humic acids (HA) and phosphatidylcholine (PC), displaying a high affinity for both copper (Cu) and IONP, could play a...
Presentation
Iron-Organic Matter (Fe-OM) nanoaggregates produced by redox alternation in wetlands are a key factor in the control of metallic pollutants mobility. Their ability to adsorb metal(loid)s depends on the size, morphology and structural arrangement between Fe and OM phases, which is mainly controlled by the OM occurrence. The physical, chemical and mo...
Article
Full-text available
Engineered oxide nanoparticles have appeared as a highly promising tool for soil remediation. However, their behaviour under complex environmental exposures (i.e. in natural soils) remains poorly understood and a relevant issue to complete their risk assessments. Prior using iron oxide nanoparticles in soil remediation scenarios, it is crucial to e...
Conference Paper
Nous avons étudié les effets cumulatifs des cycles répétitifs redox, qui se produisent naturellement pendant les périodes d'inondation dans les sols des zones humides. Notre objectif était de ralentir l'oxydation abiotique du fer (Fe) pour étudier la dynamique des colloïdes et des nano-agrégats de Fe-matière organique (Fe-MO). Pour atteindre cet ob...
Article
Iron - organic matter (Fe-OM) nanoaggregates are highly abundant in wetlands. Iron oxyhydroxides and natural OM are strong sorbents for metals and metalloids due to their high density of binding sites. They are thus considered as a major vector for the transport of metallic pollutants in this type of aquatic system. However, their structural organi...
Article
The ability of nanoplastics (NPTs) to bioaccumulate and cotransport pollutants in the whole organism is one of the most dangerous aspects of this form of plastic debris, defining a new class of emerging pollutants that is still largely unknown. In this context, it is essential to have accurate and representative models of nanoplastics to better und...
Article
The nanoscale size of plastic debris makes them potential efficient vectors of many pollutants and more especially of metals. In order to evaluate this ability, nanoplastics were produced from microplastics collected on a beach exposed to the North Atlantic Gyre. The nanoplastics were characterized using multi-dimensional methods: asymmetrical flow...
Conference Paper
We investigated the cumulative effects of repetitive redox cycles, which occur naturally during flooding and wetting periods in wetland soils. Our aim was to slowdown Fe abiotic oxidation to study the Fe-organic matter colloids and nano-aggregates dynamic. To achieve this goal, reduction/oxidation cycles were performed on a soil suspension/solution...
Article
Fe oxyhydroxides in riverbanks and their high binding capacity can be used to hypothesize that riverbanks may act as a "biogeochemical filter" between wetlands and rivers and may constitute a major mechanism in the trapping and flux regulation of chemical elements. Until now, the properties of Fe minerals have been very poorly described in riverban...
Article
Colloids have been recognized as key vectors of pollutants in aqueous environment. Amongst them, those formed by iron (Fe) and organic matter (OM) are of major importance due to their ubiquity in the surface environment and strong affinity for metals. In the recent years, Fe stable isotopes have been increasingly used to elucidate the sources and b...
Article
Environmental contextThe origin of organic matter at Earth’s continental surface can be either terrestrial or microbial, and its precise composition can influence its reactivity towards metals. We investigated the potential of rare earth elements to fingerprint the origin of various organic matters through their reactivity and composition. The rare...
Article
Plastic pollution in the marine environment poses threats to wildlife and habitats through varied mechanisms, among which are the transport and transfer to the food web of hazardous substances. Still, very little is known about the metal content of plastic debris and about sorption/desorption processes, especially with respect to weathering. In thi...
Poster
The goal of the present study is to reveal the potential Fe isotopic fractionation occurring relative to the size fractionation of Fe in the presence of OM.
Article
The evolution of rare earth element (REE) speciation between reducing and oxidizing conditions in a riparian wetland soil was studied relative to the size fractionation of the solution. In all size fractions obtained from the reduced and oxidized soil solutions, the following analyses were carried out: organic matter (OM) characterization, transmis...
Article
Nanoparticles play an important role in controlling the mobility of pollutants such as arsenic (As) in the environment. In natural waters, aggregates of nanoparticles can be constituted of organic matter (OM) associated with iron (Fe). However, little is known about their network structure, especially the role of each component in the resulting agg...
Article
Although the behavior of Arsenic (As) under reducing conditions in periods of high water levels in wetlands is well understood and documented, there is a lack of information under oxidizing conditions when the water level decreases. In this study, we were interested in the first stage of the oxidizing period, when oxidation products are still in su...
Article
Soils in riparian wetlands are periodically flooded, resulting in the establishment of reducing conditions and the solubilization of As, subsequently to the reductive dissolution of Fe(III)-oxyhydroxides. When the water level decreases, the wetlands are reoxidized. However, although the behavior of As under the reducing period is well documented, t...
Article
Although it has been suggested that several mechanisms can describe the direct binding of As(III) to organic matter (OM), more recently, the thiol functional group of humic acid (HA) was shown to be an important potential binding site for As(III). Isotherm experiments on As(III) sorption to HAs, that have either been grafted with thiol or not, were...
Article
The foundation of nanoscience is that the properties of materials change as a function of their physical dimensions, and nanotechnology exploits this premise by applying selected property modifications for a specific benefit. However, to investigate the fate and effect of the engineered nanoparticles on toxic metal (TM) mobility, the analytical lim...
Article
Full-text available
Wetlands are specific areas able to regulate metals mobility in the environment. Among metals, rare earth elements (REE) appear to be particularly interesting because of the information that could be provided by the REE patterns. Moreover, as REE are becoming a matter of great economic interest, their significant release into the environment may be...
Article
Arsenic (As) is a toxic and ubiquitous element which can be responsible for severe health problems. Recently, Nano-scale Secondary Ions Mass Spectrometry (nanoSIMS) analysis has been used to map organomineral assemblages. Here, we present a method adapted from Belzile et al. (1989) to collect freshly precipitated compounds of the re-oxidation perio...
Article
The presence of arsenic(As)-bearing Fe(III) oxyhydroxides in wetland zones may threat water quality due to the reduction processes that affect these zones. These processes have indeed the potential of releasing As into the soil solutions, and ultimately into the nearby river network, being given the hydrological connectivity that exists between wet...
Article
Understanding the processes involved in the control of arsenic (As) dynamics within soils has become a challenging issue for soil and water quality preservation. Interactions between mineralogical phases, organic ligands and bacterial communities - closely linked to the chemical conditions of the medium - were thus investigated through a geochemica...
Article
Humic substances are major natural complexing agents that strongly influence the cycling of metal cations in the environment. The metal to humic acid (HA) concentration ratio (metal loading) can significantly impact the overall HA complexation properties in natural soils and waters. At low metal loading, cations bind to strong multi-carboxylate or...
Presentation
L’empoisonnement à l’arsenic (As), via la contamination des eaux souterraines utilisées comme eaux de boisson est responsable de l’une des plus grandes mortalités et morbidités. En conditions oxydantes, l’As est majoritairement présent à l’état V et le fer (Fe) sous forme d’oxydes, connus pour adsorber l’As, alors qu’en conditions réduites l’As(III...
Article
Full-text available
Arsenic (As) is a toxic and ubiquitous element found in the atmosphere, soils, rocks, natural waters and organisms, which can be responsible for severe health problems. The As behaviour in soil is controlled by both pH and redox potential of the medium, as well as the metals and the organic matter concentration. However, which kind of interaction b...
Presentation
Full-text available
La matière organique (MO), et plus spécialement les substances humiques (SH), sont connues pour complexer de nombreux métaux comme les terres rares, Al, Mn, Mg... Cependant, il existe peu d’étude sur les interactions entre le Fe(II) et la MO (Schnitzer et Skinner, 1966; Van Dijk, 1971; Rose et Waite, 2003; Yamamoto et al., 2010). Or, bien comprendr...
Article
Iron (Fe) reactivity and arsenic (As) reactivity in wetland soils were studied by applying a generalized dissolution rate law to data recovered from reductive dissolution experiments using As-bearing-Fe(III)-oxyhydroxides (ferrihydrite and lepidocrocite). Although As does not correspond to a separate mineral, the kinetic law can be successfully use...
Article
Competitive mechanisms between rare earth elements (REE) and aluminium for humic acid (HA) binding were investigated by combining laboratory experiments and modeling to evaluate the effect of Al on REE–HA complexation. Results indicates that Al3+ competes more efficiently with heavy REE (HREE) than with light REE (LREE) in acidic (pH = 3) and low R...
Article
Shallow groundwater samples (filtered at 0.2 μm) collected from a catchment in Western France (Petit Hermitage catchment) were analyzed for their major- and trace-element concentrations (Fe, Mn, V, Th and U) as well as their dissolved organic carbon (DOC) concentrations, with the aim to investigate the controlling factors of vanadium (V) distributi...
Article
Shallow groundwater samples (filtered at 0.2 μm) collected from a catchment in Western France (Petit Hermitage catchment) were analyzed for their major- and trace-element concentrations (Fe, Mn, V, Th and U) as well as their dissolved organic carbon (DOC) concentrations, with the aim to investigate the controlling factors of vanadium (V) distributi...
Article
The Humic Ion Binding Model VI (Model VI) – previously used to model the equilibrium binding of rare earth elements (REE) by humic acid (HA) – was modified to account for differences in the REE constant patterns of the HA carboxylic and phenolic groups, and introduced into PHREEQC to calculate the REE speciation on the HA binding sites. The modific...
Article
The present study makes use of a detailed water balance to investigate the hydrological status of a peatland with a basal clay-rich layer overlying an aquifer exploited for drinking water. The aim is to determine the influence of climate and groundwater extraction on the water balance and water levels in the peatland. During the two-year period of...
Article
In wetland soils, several soil phases such as Fe(III)-oxyhydroxides, organic matter (OM) or mixed Fe-OM particles can host trace metals which can be subsequently released during soil reduction. Anoxic and oxic wetland soil incubation experiments, combined with analyses of soil solutions sampled from a natural wetland during a reduction event, are u...