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Motivation for detecting engineered nanoparticles (ENPs) in the environment comes from a need to understand fate and behavior of these materials in natural matrices. The difficulty lies in the low expected ENP particle number concentration (PNC) and the presence of a large and variable background concentration of natural NPs. We report the PNCs and characteristics of cerium-bearing nanoparticles (Ce-NPs) and titanium-bearing nanoparticles (Ti-NPs) in an aquatic matrix (the Seine River and three of its tributaries) with the use of single particle ICP-MS (spICPMS) and electron microscopy (FEG-SEM). Ce-bearing and Ti-bearing particles were observed in suspended particulate matter collected onto 0.2 μm and 1 kDa filters, using FEG-SEM imaging. At Marnay-sur-Seine, the upstream point, PNCs for Ce-NPs and Ti-NPs were 0.47 ± 0.07 × 106 and 1.35 ± 0.17 × 106 particles as measured by spICPMS. The maximum PNC for both Ce-NPs and Ti-NPs, 1.59 ± 0.10 × 106 particles mL−1 and 5.89 ± 0.10 × 106 particles mL−1, respectively, were found in the Marne River, a major tributary to the Seine. It was shown that downstream of each confluence, an increase in the PNC of the Seine is observed, suggesting a significant contribution of the different tributaries. Mass balance of particles flows and elemental ratios of Ce/La showed that in the Marne and the Oise River, a contribution of natural CeO2 NPs exists. The anthropogenic contribution in TiO2 ENPs for the Marne River was further assessed with Ti/Al, Ti/V, and Ti/Y elemental ratios. Near constant element ratios in the Seine below the Orge River and Paris city suggest neither contribute significantly to Ce or Ti NP concentrations. The study provides further investigation of the strengths and limitations of the application of spICPMS to natural samples and contributes data to the currently highly-limited dataset on natural NP backgrounds in rivers, information that is key to assessing the potential for quantifying the input of ENPs to surface waters. Of the total mass of Ce and Ti, 83 and 90%, respectively, could be detected as particles by spICPMS.

The need to quantify engineered nanoparticles (ENPs) in the environment is due to the increasing incorporation of these particles in the daily products, which threatens human health and can possibly impact natural systems. Ceria NPs (CeO2NPs) and titanium dioxide NPs (TiO2NPs) are two of the most used ENPs in the world. In this study their occurrence was determined in river waters with accurate and relevant techniques such as single particle ICP-MS (spICPMS). In the Loire River (France), the variation of both CeO2NPs and TiO2NPs could be assessed locally, with an increase of the concentrations near a wastewater treatment plant (WWTP) outlet as well as in a lake connected to the river and dedicated to outdoor activities. In the upstream river water, supposedly less impacted by NPs, 6.4 ± 1.2 x 104 part mL-1 Ce-bearing and 13.4 ± 1.8 x 104 part mL-1 Ti-bearing particles were measured. These values increased to 33.9 ± 3.4 x 104 part mL-1 Ce-bearing and 80.3 ± 3.4 x 104 part mL-1 Ti-bearing particles near the WWTP outlet. Equivalent size for sphere distributions ranged from 24 nm to 70 nm for CeO2 and from 80 nm to 500 nm for TiO2 in the river water. In the lake, a raise of the concentrations has been observed with 38.3 ± 2.0 x 104 part mL-1 and 71.6 ± 2.1 x 104 part mL-1 containing Ce and Ti, respectively, with similar size distributions. FEG-SEM imaging confirms the occurrence of Ce- and Ti-bearing particles in the water samples. On the contrary, NPs seem to undergo strong heteroaggregation in the Loire river water. The Ce/La elemental ratios does not evolve from upstream to downstream the WWTP outlet, suggesting that a natural origin cannot be excluded to explain the increase observed in NPs number concentration. On the contrary, the Ce/La ratio increases in the outdoor activities center, which suggests the contribution of NPs potentially related to the cars parked nearby. Besides, elemental ratios Ti/V and Ti/Y have been assessed to highlight an anthropogenic source of Ti in both sampling sites, possibly to the sunscreens used during the summer.

This study compared effects of pH, ionic strength and complexation with Mg2+ on the chromophores and fluorophores of aquatic and terrestrial NOM exemplified by the standard isolates Suwannee River fulvic and humic acid (SRFA and SRHA) and Pahokee Peat fulvic and humic acids (PPFA and PPHA) provided by the International Humic Substance Society (IHSS). The intensity of the differential spectra of the NOM isolates increased monotonically with pH. These spectra comprised contributions of similar chromophore systems associated with the carboxylic and phenolic moieties. The intensity of SRFA and PPFA fluorescence changed non-monotonically vs. pH indicating that the deprotonation of the phenolic fluorophores decreased their emission yields. Examination of the effects of pH on the slopes of the log-transformed absorbance of NOM showed that the influence of deprotonation on the conformations of PPFA and PPHA molecules was less prominent than those for SRFA but not dissimilar to those of SRHA. Changes of the differential spectra and spectral slopes showed that Mg2+/PPFA and Mg2+/PPHA complexation was more effected by electrostatic interactions while the involvement of phenolic groups was notable for SRFA. The observed trends highlight similarities and differences in the properties of the chromophores and fluorophores in the standard isolates of soil and aquatic NOM. These results necessitate further systematic comparison of the properties of NOM isolates and those of unaltered NOM.

The difficulties when studying the behavior of engineered nanoparticles (ENPs), and the subsequent metal speciation in aquatic ecosystems, at environmentally relevant concentrations (i.e., ppt level) are often related to the occurrence of ENP constitutive elements at high concentrations as a background in aquatic media. In this study, the physicochemical behavior of CdSe/ZnS quantum dots (QDs) when spread at very low concentrations in surface waters was investigated. The above-mentioned issues were overcome with the use of isotopically labeled QDs, separated by centrifugal ultrafiltration (CU) and measured by high-resolution inductively coupled plasma mass spectrometry (HR-ICP-MS), combined with the detection of free and labile metal ions by scanned stripping chronopotentiometry (SSCP). They firmly provided a thorough comprehension regarding the transformation of QDs in surface waters. The physicochemical conditions of the medium including the presence of an analog of natural organic matter and a mineral (i.e., fulvic acid and goethite), the manufactured coating of the QDs [here thioglycolic acid (TGA)], and the occurrence of added Zn in the medium were considered in the study. The overall results show that, in the absence of mineral/organic matter, the TGA ligands in solution that detached from the QD surface after dissolution control the metal speciation, especially for Cd. Conversely, in a more representative aquatic ecosystem condition (i.e., with Zn in the background media together with fulvic acid and goethite), almost no Zn or Cd dissolution from the QDs is detected. SSCP measurements reveal that the Zn complexes formed with the organic/mineral material in the system are inert, whereas the speciation model calculations indicated that Cd2+ is bound to TGA ligands in solution and organic/inorganic matter—therefore suggesting that, under the studied conditions, aquatic organisms will be exposed to a very low concentration of free and labile metal ions issued from the QDs.

The increasing use of Quantum Dots (QDs) - nanoparticles exhibiting unique optical properties – and their incorporation in multiple engineering products is likely to result in the release of this new class of contaminants into natural systems. In soils, bacterial biofilms and mineral surfaces form highly reactive interfaces, which may control QDs' environmental fate. However, little is known regarding QDs' stability in, and modes of interactions with, biofilm/mineral interfaces. This study examines the interactions, distributions and stability of thioglycolic acid-capped CdSe/ZnS QDs at the corundum (α-Al2O3)/Shewanella oneidensis MR-1 interface, for exposure times ranging between 1 h to 24 h. Long Period – X-ray Standing Wave – Fluorescence Yield spectroscopy and Grazing Incidence – X-ray Absorption Spectroscopy were used. Results indicate increases in Zn and Se concentrations within the biofilm/crystal system with time, demonstrating its high accumulation capacity over 24 h. In addition, dissolution of a part of the ZnS shell occurs within 1 h, highlighting the potential degradation of QDs when exposed to the biofilm/crystal compartment. Once released, Zn(II) migrates toward the biofilm-crystal interface and interacts preferentially with the crystal surface. In contrast, the remaining CdSe core is mostly preserved, and stays within the biofilm thickness. However, at 24 h, Se and Zn present similar distribution profiles indicating a general reduction in ZnS shell dissolution at this longer exposure time.

Natural organic matter (NOM) is known to play an important role in the transport and binding of trace metal elements in aquatic and soil systems. Thallium is a pollutant for which the extent of the role played by NOM is poorly known. Consequently, this study investigates thallium(I) and its complexation to a purified humic substance as proxy for NOM. Experiments were performed with the Donnan Membrane Technique to separate, for the first time, the free Tl+ ion from its complexed form in the bulk solution. Various pH and concentrations were investigated at constant ionic strength and constant NOM proxy concentrations in solution. Experimental results were described with NICA-Donnan model. Thallium complexation was compared to silver complexation using literature data and using the same NICA-Donnan formalism. Parameters for these two cations (Tl+ and Ag+) are reported in this article, for the first time. Results display low thallium complexation to the NOM proxy while silver competes with divalent cations for the NOM binding sites. Calculated speciation for dissolved thallium highlights the dominance of free thallium (Tl+) in solution whereas Tl-NOM complexes contribute roughly 15% to total Tl(I) species in river and lake type waters. Similar results are obtained for soil solutions, Tl-bound to NOM

International audience; 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 a result, not only their solubility but also their structure controls the mobility of many essential and toxic elements. In addition, microorganisms that form hot spots and are widespread in environmental systems are also primordial players in electron transfer processes by acting as a catalyst between an electron donor and an acceptor, and through their contaminant detoxification metabolism.

The strengths and limits of isotopically labelled Engineered Nanoparticles (spiked ENPs) spread in biological media have been assessed. Multi-spiked CdSe/ZnS quantum dots (QDs), measuring 7 nm and coated with thioglycolic acid (TGA), were synthesized and enriched in 68Zn, 77Se and 111Cd. These QDs were dispersed at very low concentrations (0.1 to 5000 ppt) in diverse biological matrices (synthetic saliva, synthetic urine, plasma and Dulbecco’s phosphate buffered saline - DPBS growth medium) and the isotopic compositions were determined by HR-ICP-MS. The initial QDs concentrations were calculated to assess the limit of quantification (QD-LOQ) according to the matrix and the isotopically enriched element. The obtained results demonstrated the advantages of the isotopic labelling method in order to work at very low concentrations: the QD-LOQ values for the spiked Zn, Cd and Se originated from the QDs were 10, 0.3 and 6 ppt, respectively, which is below the conventional LOQ of the HR-ICP-MS used (30, 3 and 60 ppt for Zn, Cd and Se, respectively). Conversely, in complex matrices such as saliva, urine, plasma and DPBS growth medium, the QD-LOQ values increased significantly, with values ranging from 16 to 32 ppt for Cd, 446 to 10598 ppt for Zn and 1618 to 8317 ppt for Se. These QD-LOQs are dependent on factors as the elemental background concentration already present in the matrices, and the dilution factor. In this study, the QD-LOQs are expressed for the first time with respect to the background concentration in biological media (QD-RLOQ), which can be used to better assess and then predict the efficiency of the spiking method.

International audience; The increasing application of Quantum Dots (QDs) is cause of concern for the potential negative effects for the ecosystem, especially in soils that may act as a sink. In this study, soil leaching experiments were performed in quartz sand packed columns to investigate the behavior of core-shell CdSe/ZnS QDs coated with either small ligands (TGA-QDs) or more complex polymers (POAMA-QDs). Fluorescence emission was compared to mass spectrometric measurements to assess the nanoparticles (NPs) state in both the leachate (transported species) and porous media (deposited amounts). Although both QDs were strongly retained in the column, large differences were observed depending on their capping ligand stability. Specifically, for TGA-QDs elution was negligible and the retained fraction accumulated in the top-columns. Furthermore, 74% of the NPs were degraded and 38% of the Se was found in the leachate in non-NPs state. Conversely, POAMA-QDs were recovered to a larger extent (78.1%), and displayed a higher transport along the soil profile. Further experiments with altered NPs showed that homo-aggregation of the QDs prior injection determined a reduced mobility but no significant changes in their stability. Eventually, ageing of the NPs in the column (15 days) caused the disruption of up to 92% of the original QDs and the immobilization of NPs and metals. These results indicate that QDs will accumulate in top-soils, where transformations phenomena will determine the overall transport, persistency and degradation of these chemicals. Once accumulated, they may act as a source for potentially toxic Cd and Se metal species displaying enhanced mobility.

Neutropènia induïda per quimioteràpia; Càncer colorectal metastàtic Neutropenia inducida por quimioterapia; Cáncer colorrectal metastásico Chemotherapy-induced neutropenia; Metastatic colorectal cancer Background The phase II J003 (N = 169) and phase III RECOURSE (N = 800) trials demonstrated a significant improvement in survival with trifluridine (FTD)/tipiracil (TPI) versus placebo in patients with refractory metastatic colorectal cancer. This post hoc analysis investigated pharmacokinetic data of FTD/TPI exposure and pharmacodynamic markers, such as chemotherapy-induced neutropenia (CIN) and clinical outcomes. Patients and methods A total of 210 patients from RECOURSE were enrolled in this substudy. A limited sampling approach was used, with three pharmacokinetic samples drawn on day 12 of cycle 1. Patients were categorized as being above or below the median area under the plasma concentration–time curve (AUC) for FTD and TPI. We conducted a post hoc analysis using the entire RECOURSE population to determine the correlations between CIN and clinical outcome. We then carried out a similar analysis on the J003 trial to validate the results. Results In the RECOURSE subset, patients in the high FTD AUC group had a significantly increased CIN risk. Analyses of the entire population demonstrated that FTD/TPI-treated patients with CIN of any grade in cycles 1 and 2 had significantly longer median overall survival (OS) and progression-free survival (PFS) than patients who did not develop CIN and patients in the placebo group. Patients who required an FTD/TPI treatment delay had increased OS and PFS versus those in the placebo group and those who did not develop CIN. Similar results were obtained in the J003 cohort. Conclusions In RECOURSE, patients with higher FTD drug exposure had an increased CIN risk. FTD/TPI-treated patients who developed CIN had improved OS and PFS versus those in the placebo group and those who did not develop CIN. Similar findings were reported in the J003 cohort, thus validating the RECOURSE results. The occurrence of CIN may be a useful predictor of treatment outcomes for FTD/TPI-treated patients. This study was supported by Taiho Pharmaceutical Co., Ltd., Tokyo, Japan and Taiho Oncology, Inc., Princeton, NJ, USA. No grant numbers are applicable.

International audience; Surface waters from three catchments having contrasting land-uses (forested, agricultural, and urban) were sampled monthly and analysed for nanoparticulate titanium dioxide (NPs-TiO2) by single particle ICPMS and electron microscopy. We report one-year of data for NPs-TiO2 having average number and mass concentrations of 9.1 x 108 NPs-TiO2 particles L-1 and 11 μg NPs-TiO2 L-1 respectively. An increase in concentration during warmer months is observed in the forested and agricultural catchments. Both concentrations of NPs-TiO2 are within the range of recently reported values using similar analytical approaches. The positive correlations for NPs-TiO2 mass concentration or particle number with the concentration of some trace elements and DOC in the forested and agricultural catchments suggest the detected NPs-TiO2 in these two systems are mostly from geogenic origin. Additionally, microscopy imaging confirmed the presence of NPs in the three catchments. Furthermore, the land-area normalized annual flux of NPs-TiO2 (1.65 kg TiO2 year-1 km-2) was highest for the agricultural catchment, suggesting that agricultural practices have a different impact on the NPs-TiO2 dynamics and exports than other land-uses (urban or forestry). A similar trend is also found by the reanalysis of recent literature data.

International audience; To better understand the focusing process and to determine the focusing position (z(foc)) in Asymmetrical Flow Field-Flow Fractionation (AF4), theoretical and experimental studies were performed. A new theoretical expression that allows the calculation of z(foc) in AF4 channels of any shape having an axial plane of symmetry was established. The equation was then applied to the particular case of a trapezoidal AF4 channel with tapered ends. The applicability of this equation was verified by comparing the calculated results with the experimental measures of the focusing position obtained using blue dextran dye under different flow conditions. The calculated values and the experimental results were in good agreement. The total uncertainty associated with the calculated z(foc) was evaluated and was lower than 10%. A good repeatability and reproducibility of the focusing position was obtained.Moreover, the effects of the sample-injection position, the spacer thickness, the membrane aging, and the nature of the injected sample on the focusing position were investigated: z(foc) was not influenced by these parameters, proving the universal applicability of the equation given in this work for predicting the focusing position, when the assumption of constancy of the cross-flow velocity at the membrane, which underlies this equation, is fulfilled. Additionally, it is notable that this theoretical expression is suitable for different models of AF4 channel and not peculiar to specific suppliers

Fluorescence of the hydrophobic acid fraction (HPOA) of Suwannee River natural organic matter and Tb3+ excitation spectra were measured in tandem using the instantaneous and time-resolved emission modes. The intensity of HPOA fluorescence decreased in the presence of Tb3+, while the intensity of the emission from Tb3+ cations bound by HPOA increased by up to several orders of magnitude due to energy transfer (ET) from HPOA to Tb3+ ions. To determine intrinsic ET and fluorescence quenching (FQ) coefficients, NICA–Donnan modeling was carried. It showed that phenolic groups in HPOA dominated both the ET and FQ processes and that the binding of Tb3+ by HPOA could be described using the non-ideality parameter nTb, median binding constant log $$\tilde{K}_{\text{Tb}}$$ for the phenolic sites and intrinsic ET and FQ coefficients (denoted as ηTbΦ and αTbΦ), and were 0.48, 8.5, 1385 and 0.12, respectively. The high value of the energy transfer coefficient of Tb3+ ions bound by the phenolic groups in HPOA is indicative of both the match between the electronic levels of the donor and acceptor, and the short distance between them. The deviation of the data of Nica–Donnan modeling of the ET and FQ dependence of versus [Tb]total for a 1.0 M ionic strength highlights the need to quantify the distribution of donor–acceptor distances in HPOA molecules in more detail.

The behaviour and fate of copper (Cu) and zinc (Zn) at river confluences is poorly understood, although chemical and physical processes during mixing of compositionally different tributaries might condition metal availability and fluxes to the ocean. To identify and quantify the effect of such processes in river mixing zones, particulate Cu and Zn isotope signatures (delta(65) Cu-SPM and delta Zn-66(SPM)) were measured along cross sections and vertical profiles at the largest river confluence in the world, the "Encontro das Aguas" mixing zone of the Amazon River, where the organic-rich Negro River meets the sediment-rich Solimoes River. The Negro River suspended sediments, with highly variable Cu and Zn concentrations as well as delta Cu-65(SPM) and delta(66) Zn-SPM, are mostly influenced by organic matter and by the lateritic cover of the watershed. The Solimoes River suspended sediments, more homogeneous in Cu and Zn concentration and isotope composition across the river section, reflect the signature of weathered silicate-rich sediments derived from the Andes. The Solimoes River supplies the majority of the suspended Cu and Zn to the Amazon River, and despite important flux losses across the confluence (-35% for Cu and -27% for Zn), delta(65) Cu-SPM and delta(66) Zn-SPM show a conservative behaviour during the mixing. In the dissolved load, Cu concentrations and delta(65) Cu-diss, mostly supplied by the Solimoes River, behave conservatively whereas Zn, derived mainly from the Negro River, suffers an important loss ( -58%) that can be attributed to Zn adsorption onto the suspended sediments from the Solimoes River. This transfer does not induce a significant delta(66) Zn-SPM shift in the Amazon River suspended sediments. Therefore, Cu and Zn isotope ratios in the suspended sediments behave conservatively through this confluence, which mixes two very chemically-contrasted rivers. Our findings thus suggest that the riverine isotopic information on the sources of particulate Cu and Zn is preserved during tributary mixing.

International audience; Clay minerals play a relevant role in the transport and fate of trace elements in the environment. Though illite has been referred as an important Thallium (Tl) bearing phase in soils, mechanisms and affinity of thallium for clay minerals remain poorly known. This study investigated the sorption behavior of thallium as Tl(I) onto illite and smectite, two clay minerals occurring mainly in soils and sediments. Different sorption experiments were carried out under various pH conditions and Tl concentrations, in competition with sodium and calcium at a constant ionic strength of 0.01 mol L$^{-1}$. Our results showed that illite displayed more affinity than smectite for thallium. With illite, the distribution coefficients (K$_d$ in L kg$^{-1}$) varied between 10$^{2.75 \pm 0.17}$ and 10$^{4.0 \pm 0.17}$ in Na solutions versus between 10$^{2.25 \pm 0.17}$ and 10$^{3.0 \pm 0.17}$ in Ca solutions, depending on pH. With smectite, K$_d$ (in L kg$^{-1}$) ranged between 10$^{2.50 \pm 0.16}$ and 10$^{3.20 \pm 0.16}$ and between 10$^{1.25 \pm 0.16}$ and 10$^{1.95 \pm 0.16}$ in Na and Ca solutions, respectively. Sorption behavior was described with the Multi-Site Ion Exchanger model and selectivity coefficients with respect to protons were calculated for the first time. In all cases, independently of clay mineral and background elec-trolyte, low capacity but highly reactive sites were dominant in thallium uptake, highlighting Tl affinity for those sites. Moreover , the exchangeable and reversible interactions between Tl$^+$ and clays reactive sites suggested that in changing conditions, thallium could be released in solution. The role of clay minerals in thallium environmental cycle is evident and confirmed illite to be a dominant Tl bearing phase, in some environment competing with manganese oxides. Compared to others Tl bearing mineral phases, clays are ranked as follows: MnO$_2$ > illite > smectite $\sim$ ferrihydrite $\geq$ Al$_2$ O$_3$ $\geq$ goethite > SiO$_2$. Finally, over the three monovalent cations (Tl, Rb, Cs) Tl is the one less sorbed on illite independently of the background cations.

International audience; In case of nuclear accident, 90Sr and 134,137Cs are major radionuclides to account. In previous works (Appl. Geochem. 87, 167; ibid 93, 167), a database of ion-exchange parameters allowing the description of the Sr2+ and Cs+ adsorption on purified illite and smectite was developed for a multi-site ion-exchange (MSIE) model. In this study, the adsorption behaviours of Sr2+ and Cs+ were obtained with

Because of their mechanical, thermal, and chemical resistance, ceramic materials are suitable for challenging water treatments, where different metal oxides (MeO) have been tested as active layers. However, organic fouling is a major drawback impacting its performance. Organics adsorb onto the membrane surface and into their pores during long-term operation, resulting in irreversible fouling. This investigation focussed on the interfacial interactions between model organic acids and MeO to obtain a fundamental understanding of the adsorption phenomena. Batch adsorption experiments of a series of small molecular weight, oxygenated, aromatic organic acids were performed with Al2O3, TiO2, and ZrO2 particles, at pH 4.2 and 7.6. The adsorption of simple acids was described by the Langmuir model and exhibited a strong dependence on the relative abundance of carboxyl groups, aliphaticity/aromaticity, alkyl chain length, and presence of hydroxyl groups. The adsorption of model compounds was higher at low pH and decreased with increasing pH. The difference in Al2O3, TiO2, and ZrO2 surface characteristics, as evidenced by TEM, XRD, and BET, led to differences in the adsorption density. The results obtained with these well-defined organic structures will assist in better understanding the interfacial interactions between complex natural organic matter molecules and MeO of different characteristics.

International audience; The complex behaviour of Zn and Cu at the soil-river interface was investigated in soil and riverine water samples from the Rio Negro basin, a secondary tributary of the Rio Amazonas, using their stable isotope compositions. This acidic and organic river drains two types of intensely weathered terrains: podzols in its upstream part, and lateritic soils downstream. Bulk soil particles, suspended particulate matter (SPM) as well as colloidal fractions were sampled across the whole basin during low and high water stages.In the basin, Zn and Cu are mostly exported from lateritic soils and transported by organic colloids where significant losses are observed in the downstream part of the river. The use of delta Zn-66 and delta Cu-66 measurements reveals distinct stories for these two metals in suspended sediments and colloids. In the colloids, the constant delta Zn-66(coll) across the basin is induced by the same weak association mode between Zn and organic ligands, regardless of the origin of the water. By contrast, in SPM, the speciation of Zn and thus delta Zn-66(SPM) differ according to the type of drained soils. Zn is associated with organic complexes in particles exported with water draining podzol whereas Zn2+ is incorporated in the structure of the remaining kaolinite clays in lateritic output.The stronger reactivity of Cu than Zn with organic ligands induces its complete complexation. Copper is controlled by refractory particulate organic matter (POM) and by reactive colloidal organic matter; the latter being enriched in delta Cu-65 due to stronger binding interactions than in POM. While the Cu content remains constant in the upstream part of the Rio Negro, downstream, the decrease of SPM and colloidal Cu fluxes is associated with a constant delta Cu-65(SPM) and with an increase of delta Cu-65(coll) at the Rio Negro outlet. Geochemical mass balance modelling, based on SPM, Cu and Zn fluxes in SPM and their associated isotopic signatures, confirms distinct host phases for Zn and Cu, and identifies the most probable places where losses of these two metals occur. In colloids, the observed Cu isotope fractionation (from 0.24 to 0.45%) superimposed on the significant Cu-coll loss is assumed to result from a new isotopic equilibrium in a low velocity and high productivity zone: Cu-rich colloids enriched in Cu-63 aggregate and settle down, whereas the remaining heavy Cu is partially complexed on strong organic ligands secreted by phytoplankton, forming new Cu-colloids

International audience; The mu-dDIHEN allows direct nebulization of small samples into the plasma at a flow rate down to 5 mu L min(-1). It is composed of a demountable direct injection high efficiency nebulizer (d-DIHEN), a flow injection analysis (FIA) valve and a gas displacement pump (GDP) connected to a mu-mass-flow meter delivering very stable liquid flow. The system was successfully tested with sample loops of 10 and 50 mu L and for liquid flow rates between 5 and 50 mu L min(-1) on two different inductively coupled plasma mass spectrometry (ICP-MS) instruments, a sector-field-ICP-MS (SF-ICP-MS) and a multi-collector-ICP-MS (MC-ICP-MS), and for three different applications: boron isotopic ratio measurement of geological samples, multi-element analyses of natural water samples and gold nanoparticle characterization by single particle ICPMS (spICP-MS). Signal sensitivity was increasing with the liquid uptake rate of the mu-dDIHEN (and the GDP gas flow rate), but stopped increasing above 30 mu L min(-1), due to bad spray quality and poor ionization under extra-wet conditions. We successfully measured boron isotopic ratios (delta B-11) for reference material solutions with B concentrations between 10 and 200 mu g L-1; the reproducibility of the measurements depending on both the B concentration of the sample and the uptake rate: B-10 signals below 20-30 mV (with 10(11) ohms amplifiers) gave 2SD reproducibility >= 0.5 parts per thousand (n = 5). The best measurement conditions were not necessarily with the lowest uptake rate but rather at 25 mu L min(-1), allowing for higher signals. We also tested transient versus continuous measurement modes for a series of natural samples (with 10 and 50 mu L sample loops). The two modes gave fully comparable results but the transient mode allows triplicate delta B-11 measurements and is recommended for very small samples (

This research has been conducted over the last 10 years to characterise the spatio-temporal variability of aquatic organic matter (OM) composition in the Seine River watershed upstream and downstream of Paris Megacity and its effect on micro-pollutants. For this purpose, a large number of samples were collected under different hydrological conditions, and, over 1 year, three representative sites were monitored monthly. Furthermore, the evolution of the OM composition along an urbanisation gradient, from upstream to downstream of the Paris agglomeration, was characterised, highlighting the very strong impact of urban discharges, especially during low-water periods. Substantial differences in the chemical composition are emphasised relative to the urban or natural origin of the organic matter. Dissolved organic matter (DOM) interactions with metallic and organic micro-pollutants were studied, allowing us to (1) identify the key role of DOM on their speciation and bioavailability in aquatic systems and (2) demonstrate that these interactions depend on DOM composition and origin. The essential role of urban DOM on the speciation of trace metals in the Seine River downstream of the Paris agglomeration is also shown.

International audience; Humic substances impact the fate of radionuclides in the environment. The formation of mixed complexes between lanthanides(III), carbonates, and humic substances is still a matter of debate and further studies are needed. Time-resolved luminescence spectroscopy (TRLS) is used to evidence the presence of Eu(III)-CO 3-SRFA ternary complexes in media representative of environmental conditions. The evolutions of the Eu(III) lumi-nescence spectra from the 5 D 0 → 7 F 0 to the 5 D 0 → 7 F 2 transitions are showing modifications of the asymmetry ratio-area ratio of the 5 D 0 → 7 F 2 over the 5 D 0 → 7 F 1 transition-that indicates the presence of several species in addition to the EuCO 3 + and Eu-SRFA complexes. The occurrence of bi-exponential decay times, with one decay time faster than the one from Eu 3+ , is typical of the occurrence of fulvic complex, even in the presence of carbonate. The analyses of the indirect excitation of the Eu-CO 3-SRFA system are used to build complexation isotherms varying either SRFA or total carbonate concentrations in the framework of the NICA-Donnan modeling of the Eu(III)-SRFA system. In view of the restricted pH range, no strict attribution to the different possible types of sites can be done. Different complex(es) formations are considered and discussed.

International audience; Analytical barriers impose work at nanoparticles (NPs) concentrations orders of magnitude higher than the expected NPs concentrations in the environment. To overcome these limitations, the use of nontraditional stable isotope tracers incorporated in NPs (spiked-NPs) coupled with HR-ICP-MS has been proposed. The performance and efficiency of this analytical method was assessed in the case of quantum dots (QDs). Multi-isotopically labeled 111Cd77Se/68ZnS QDs were synthesized and their dissemination in natural aquatic matrices (river, estuarine and sea waters) was modeled at very low concentrations (from 0.1 to 5000 ppt). The QD limits of quantification (QD-LOQ) in each matrix were calculated according to the isotopic tracer. In ultrapure and simple medium (HNO3 2%), Zn, Cd, and Se originated from the QDs were quantifiable at concentrations of 10, 0.3, and 6 ppt, respectively, which are lower than the conventional HR-ICP-MS LOQs. In aquatic matrices, the QD-LOQs increase 10-, 130-, and 250-fold for Zn, Cd, and Se, respectively, but remain relevant of environmental concentrations (3.4 ppt ≤ QD-LOQs ≤ 2.5 ppb). These results validate the use of isotopically labeled ENPs at relevant concentrations in experimental studies related to either their fate, behavior, or toxicity in most aquatic matrices.

International audience; Hydrocarbon gases with unconventional carbon isotopic signatures were observed in the Solimiies sedimentary basin in north-west Brazil. Siderite contents measured with a new Rock-Eval methodology in the drill-cuttings samples of the Famenian source rock were found to decrease with the increase of gas maturity and with the occurrence of the gas isotopic anomalies. Triassic diabase intrusions induced heating of the source rock, which likely resulted in the gradual oxidative dissolution of siderite as suggested by the observation of etch pits on the siderite surfaces. It is proposed that ferrous iron from the carbonate was involved in a redox reaction with water producing ferric iron and Hy, then reducing CO2 and yielding an inverse correlation between siderite content and gas maturity. Alternatively, hydrogenation of highly mature kerogen by H-2 derived from siderite could explain the production of C-13-rich CH4. Mass balance considerations suggest that these mechanisms may account for a significant fraction of the hydrocarbon gases generated from the Famenian source rock in the Solimbes basin

International audience; In this study, we quantify zinc isotope fractionation during its sorption onto kaolinite, by performing experiments under various pH, ionic strength, and total Zn concentrations. A systematic enrichment in heavy Zn isotopes on the surface of kaolinite was measured, with Delta Zn-66(adsorbed-solution) ranging from 0.11 parts per thousand at low pH and low ionic strength to 0.49 parts per thousand at high pH and high ionic strength. Both the measured Zn concentration and its isotopic ratio are correctly described using a thermodynamic sorption model that considers two binding sites: external basal surfaces and edge sites. Based on this modeling approach, two distinct Zn isotopic fractionation factors were calculated: Delta Zn-66(adsorbed-solution) = 0.18 +/- 0.06 parts per thousand for ion exchange onto basal sites, and Delta Zn-66(adsorbed-solution) = 0.49 +/- 0.06 parts per thousand for specific complexation onto edge sites. These two distinct factors indicate that Zn isotope fractionation is dominantly controlled by the chemical composition of the solution (pH, ionic strength)

The extensive use of silver nanoparticles (AgNPs) is likely to result in their significant environmental release, and thus raises important concerns regarding their impact on ecosystems. In soils, bacterial biofilms can be found as mineral coatings, which form a complex interface that exhibits highly specific physico-chemical properties. As a result, this environmental compartment is likely to partially control the fate of AgNPs. However, the interaction modes that nanoparticles undergo at the solution/biofilm/mineral interface are not yet well understood. Thus, herein, the dynamics of the AgNP interactions at the Shewanella oneidensis MR-1 biofilm-corundum (α-Al2O3) interface were investigated via long-period X-ray standing waves fluorescence yield spectroscopy. Three different nanoparticle coatings with various properties (PVP, SiO2 and SiO2–NH2) are investigated, which demonstrate important differences in the partitioning and stability of AgNPs at this complex interface. The behavior of the two AgNPs coated with an organic layer, but with opposite charges (SiO2 and SiO2–NH2), indicates that initially, electrostatic interactions control the AgNPs partitioning at the solution/biofilm/mineral interface. In addition, the comparative study of the organic PVP-coated and the inorganic SiO2-coated AgNPs, which are both negatively charged, highlights the control imposed by the nanoparticle size and hydrophobic properties on their interactions with this complex interface.

In the tropic, the small watersheds are affected by intense meteorological events playing an important role on the erosion of soils and therefore on the associated organic carbon fluxes. We studied the geochemistry of three small watersheds around the Basse-Terre volcanic Island (FWI) during a four years period, by measuring DOC, POC and DIC concentrations. The mean annual yields ranged 8.1–15.8 t C km−2 yr−1, 1.9–8.6 t C km−2 yr−1 and 8.1–25.5 t C km−2 yr−1 for DIC, DOC and POC, respectively. Floods and extreme floods represent 45 to 70 % of the annual DOC flux, and more than 80 % of the annual POC flux. The DIC flux occurs essentially during the low water level, only 43 % of the annual DIC flux is exported during floods. The distribution of the dissolved carbon between the inorganic and the organic fraction is correlated to the hydrodynamic of rivers. During low water level and floods, the dissolved carbon is exported under the inorganic form (DIC/DOC = 2.6 ± 2.1), while during extreme floods, the dissolved carbon transported is mostly organic (DIC/DOC = 0.7 ± 0.2). The residence time of the organic carbon in Guadeloupean soils may vary from 381 to 1000 yr, and is linked to the intensity of meteorological events than the frequency of meteorological events. Looking at the global carbon mass balance, the total export of organic carbon coming from small tropical and volcanic mountainous rivers is estimated about 2.0–8.9 Tg C yr−1 for DOC and about 8.4–26.5 Tg C yr−1 for POC, emphasizing that these carbon fluxes are significant and should be included in global carbon budgets.

International audience; Multi-site ion exchange modelling permits describing the different adsorption behaviour of cations onto clay minerals. Considering several adsorption sites in the clay minerals' structure allows accurately representing the overall variations of adsorption behaviours. For a wider applicability in soils and sediments, it appears necessary to build a coherent thermodynamic adsorption database for radionuclides. $^{90}$Sr and $^{134,137}$Cs are major radionuclides to be considered in the case of nuclear accidents, but thermodynamic data on their adsorption on purified smectites are scarce. Therefore, a detailed study to determine Sr$^{2+}$ and Cs$^+$ adsorption parameter on smectite seems necessary. To provide this kind of information, this study is proposing multi-site ion exchange modelling of the adsorption of Sr$^{2+}$ and Cs$^+$ onto a pure Na-MX80 montmorillonite. The intrinsic parameters-site concentration and corrected selectivity coefficient for the Na$^+$/H$^+$ exchange-were first fitted using an already available Na saturation curve of a purified smectite. The adsorption of Sr$^{2+}$ and Cs$^+$ on a purified Na-MX80 bentonite was explored, including a kinetic study for Sr, as a function of pH and equilibrium concentration. The isotherms were modelled to determine the corrected selectivity coefficients for the 2Na$^+$/Sr$^{2+}$ and Na$^+$/Cs$^+$ exchange reactions. This study provides a part of a wider databasis that is currently under construction, which can be used to predict the adsorption of Sr and Cs in soils and sediments.

Summary Chemical extraction, multi-element stable isotopic dilution (ID) and multi-surface modelling were used to investigate the lability of cadmium (Cd) and copper (Cu) in nine types of soil with different properties and contaminated or not with Cd and Cu. The chemical extraction and ID analyses both showed that Cd was more labile than Cu in all the soil types studied. From the ID results, 32.8–93.3% of total Cd and 14.7–71.8% of total Cu were isotopically exchangeable after 3 days of equilibration. A single extraction in 0.43 m HNO3 gave similar results to the 3-day ID assay for Cu in most of the soils and for Cd in the non-calcareous soils. However, an eight-step selective sequential extraction (SSE) procedure gave different results from the ID assay for both metals. Predictions of the multi-surface model for the amounts of Cd and Cu adsorbed, based on measured metal ion activities in the soil solution and the concentrations of reactive surfaces in the soil, agreed with the ID results. The model predicted that soil organic matter was the predominant sorbent for Cd and Cu in the soils and that manganese oxide was the least important sorbent. The contributions of iron oxides to sorption were predicted to be small except in soil with a high pH and little organic matter. The predicted sorption on different soil components did not match SSE measurements.

International audience; The concentration and size fractionation of major and trace elements (TEs) linked to organo-mineral colloids along the landscape gradient soil water–peat mire–humic lakes–river–large oligotrophic lake have been investigated within two watersheds located in the subarctic region (Karelia, Russia) in the summer base-flow period. A large volume of natural waters was filtered in the field using cascade filtration and ultrafiltration (UF) with a progressively decreasing pore size [100, 20, 10, 5, 0.8, 0.4, 0.22, 0.1, 0.046, 0.0066 (100 kDa), 0.0031 (10 kDa) and 0.0014 µm (1 kDa)] followed by multi-elemental ICP-MS and dissolved organic carbon (DOC) analysis. In situ dialysis with 10 and 1 kDa molecular weight cutoff membranes was also conducted. According to the TE distribution among different size fractions in the continuum soil (mire)–humic lake–river–large lake, the following groups of elements could be distinguished: (1) elements significantly bound to the colloidal (1 kDa—0.22 µm) fraction and decreasing the proportion of this fraction from the feeding lake and stream to the terminal oligotrophic lake (Fe, Ti and U); (2) colloidally dominated (>80 %) elements exhibiting similar size fractionation in all studied settings (Y, REEs, Zr, Hf and Th); (3) elements appreciably bound to colloids (20–40 %) in organic-rich soil and bog waters and decreasing their colloidal fraction to approximately 10 % in the oligotrophic lake (Mg, Ca, Sr, Rb and Mo); and (4) elements linked to the colloidal fraction (40–80 %) and not demonstrating any systematic variation between different landscape units (Ni, Co, Cu, Cd, Cr, Mn, Zn and Pb). The in situ dialysis technique produced a similar picture of the colloidal size fractionation with generally lower proportions of elements in the colloidal fraction compared to the UF. Thermodynamic modeling of trace element speciation using available codes demonstrated that complexation with dissolved organic matter and adsorption at the surface of ferric colloids can adequately model the observed colloidal speciation of divalent metals. However, the modeling could not describe the distribution of trivalent and tetravalent hydrolysates (TE3+,4+) among different size fractions and cannot reproduce the experimentally observed proportion of their colloidal forms. Therefore, coprecipitation with organo-ferric colloids should be considered to account for the partitioning of TE3+,4+ between truly dissolved (

International audience; Natural organic matter (NOM) generated in all niches of the environment constitutes a large fraction of the global pool of organic carbon while magnesium is one of the most abundant elements that has multiple roles in both biotic and abiotic processes. Although interactions between Mg2+ and NOM have been recognized to affect many environmental processes, little is understood about relevant mechanisms and equilibria. This study addressed this deficiency and quantified Mg2+-NOM interactions using differential absorbance spectroscopy (DAS) in combination with the NICA-Donnan speciation model. DAS data were obtained for varying total Mg concentrations, pHs from 5.0 to 11.0 and ionic strengths from 0.001 to 0.3 mol L-1. DAS results demonstrated the existence Of strong interactions between magnesium and NOM at all examined conditions and demonstrated that the binding of Mg2+ by NOM was accompanied by the replacement of protons in the protonation-active phenolic and carboxylic groups. The slope of the log-transformed absorbance spectra of NOM in the range of wavelength 350-400 nm was found to be indicative of the extent of Mg2+-NOM binding. The differential and absolute values of the spectral slopes were strongly correlated with the amount of NOM-bound Mg2+ ions and with the concentrations of NOM-bound protons.

Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) allows the quantification of trace and ultra-trace elements (mg/kg to pg/kg) by separating elements as a function of their mass-to-charge ratios (m/z) after ionisation into an argon plasma. In spite of being rigorous and accurate, the “Results” modules provided by many manufacturers are often uneasy to use and operators have little control on the calculation. Moreover, the large amount of raw data generated makes the manual treatment very long and not reliable using a “home-made” spreadsheet. The user-FRiendly Elemental dAta procesSIng (uFREASI) software presented in this paper follows a configurable step-by-step procedure allowing a quick and reliable data treatment plus an automatic uncertainty propagation. The concentration calculation is performed using the ordinary least square method after an external calibration. The software proposes many options to correct and to monitor the signal, to warrant both quality and understanding of data treatment. uFREASI is supported by Windows, Mac OS X and Linux operating systems, is open and extensible, and is freely downloadable at http://www.ipgp.fr/~tharaud/uFREASI .

International audience; This study utilized the methods of fluorescence quenching and differential absorbance to probe in situ the extent and the nature of the interactions between rare earth ions (REIs) and humic substances. Experiments were conducted with the standard Suwannee river humic acid (SRHA) in the presence of varying amount of lanthanum, europium and terbium. The data of differential absorbance showed that the mechanism of SRHA-metal complexation was largely the same for all the examined REIs. In all cases several discrete bands whose properties were discerned via numerical decomposition of the differential spectra absorbance were observed. Their nature was examined based on the comparison of the experimental data and those of NICA-Donnan modeling carried out for Eu3+. The observed effects suggested that the changes of SAHA absorbance induced by REIs binding are likely to be caused by a bathochromic shift of the absorbance bands associated with such chromophores. The intensity of the Gaussian band with a maximum at 387 nm was observed to be proportional to the total concentration of SRHA-bound REIs. The data obtained in this study demonstrate the existence of complex yet quantifiable changes of the spectroscopic properties of humic species in the presence of REIs and their utility to quantify modes of interactions in such systems.

International audience; During the chemical weathering of lead blast furnace (LBF) and imperial smelting furnace (ISF) slags, possible Zn isotopes fractionation was studied as a function of pH, atmosphere (open air vs nitrogen), and time. Bulk LBF and ISF displayed heavier signatures compared to Johnson Matthey Company (JMC) Zn standard solution (i.e. 0.13 +/- 0.06 parts per thousand and 0.78 +/- 0.13 parts per thousand for LBF and ISF, resp). The Zn signatures vary greatly by changes in solution pH; heavier signatures at low pH and lighter signature at high pH. Smithsonite (ZnCO3) formation could induce a big delta Delta Zn-66(Nitro-Open.atm) of 1.13 parts per thousand at pH 10 and rapid zinc hydroxide precipitation could induce Delta Zn-66(Nitro-Open.atm) of 0.13-0.2 parts per thousand at pH 8.5. In addition, slags contain many mineral phases: similar to 80-84% of amorphous glassy phase (in v/v) and similar to 16-20% of many other crystalline phases. Zn isotope signatures in primary mineral phases can be extrapolated where the signature of the amorphous glassy phase lies between-035 parts per thousand and -0.42 parts per thousand, and that of the overall crystalline phases was estimated to be 2.12 parts per thousand for LBF and 5.74 parts per thousand for ISF. Therefore, un-weathered slags with many mineral phases can host distinct Zn isotope signatures, which further evolve significantly during chemical weathering. One should thus carefully consider the heterogeneity of slags and the low-temperature chemical processes which lead to diverse Zn isotopic signature in the end, when using Zn isotopes as tracer of smelter's contamination.

International audience; High Ca concentrations in complex matrices such as river waters often hamper the detection of titanium nanomaterials (TiO2 NPs) by single particle inductively coupled plasma mass spectrometry (spICPMS), because of isobaric interference of Ca-48 on the most abundant Ti isotope (Ti-48). Several approaches were used to reduce this interference while measuring TiO2 in solutions with different Ca concentrations up to 100 mg L-1. ICP-MS/MS was used with ammonia as the reaction ceLL gas and high resoLution (HR) ICP-MS was used under different resoLution settings. These approaches were compared by measuring different Ti isotopes (Ti-47 and Ti-49). spICPMS data were then treated with a deconvoLution method to filter out dissolved signals and identify the best approach to detect the Lowest possible corresponding spherical size of TiO2 NPs (D,in). ICP-MS/MS aLLowed for an important decrease of the theoretical D-min compared to standard quadrupole ICP-MS, down to 64 nm in uLtrapure water; however the sensitivity was reduced by the reaction gas and increasing Ca concentrations also increased the D-min. The comparably higher sensitivity of HR-ICP-MS aLLowed for theoretically measuring a D-min of 10 nm in uLtrapure water. Combined with the deconvoLution analysis, the highest resoLution mode in HR-ICP-MS Leads to the Lowest D-min at high Ca concentrations, even though significant broadening of the measured mass distributions occurred for TiO2 NPs at Ca concentrations up to 100 mg L-1

Environmental contextStudying the mechanism of binding between metals and natural organic matter is fundamental to understanding the transport and availability of these contaminants in the environment. The influence of sample treatment on the purification of organic matter showed significant differences in the interaction with metals. The results will contribute to improved modelling of metal binding to organic matter in soils, thereby providing a basis for a more realistic risk assessment. AbstractWe studied the changes in metal binding characteristics of extracted humic acids induced by HF/HCl treatment followed by dialysis, i.e. the last step of the International Humic Substances Society (IHSS) extraction protocol. We performed metal binding experiments with both the alkaline-extracted material (AE) and the fully purified (FP) humic acid using the electrochemical stripping technique (AGNES) and modelled the results using the NICA-Donnan model. The results showed an increase of free Zn, Cd and Pb concentrations of similar to 1 order of magnitude for the AE compared with the FP. These differences may be mostly explained by the different carbon content (51.3% FP and 36.5% AE) associated with an AE/FP carboxyl ratio of 0.5. Simulations using the NICA-Donnan model showed that halving the amount of carboxylic groups (Q(max,1)) for the FP reduced this difference to 0.25 log units for Cd and Zn and to 0.15 log unit for Pb. There is a clear need for further research on the differences between purified v. less-disturbed natural organic material, which will contribute to improved modelling of metal binding to organic matter in soils, hence providing a basis for a more realistic risk assessment. Coordenadoria de Aperfeicoamento do Pessoal de Nivel Superior (CAPES CSF) [981313-6] Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq PVE) [400572/2013-3] French national research agency (ANR) [ANR-10-LABX-21-01/LABEX RESSOURCES 21] Portuguese national funding agency for science, research and technology [FCT-ANR/AAG-MAA/0065/2012] Region Lorraine

International audience; Correct characterization of metal speciation and reactivity is a prerequisite for the risk assessment and remedial activity management of contaminated soil. To better understand the intrinsic reactivity of Pb and Zn, nine heavily and poorly contaminated soils were investigated using the combined approaches of chemical extractions, multi-element stable isotopic dilution (ID) method, and multi-surface modelling. The ID results show that 0.1-38% of total Pb and 3-45% of total Zn in the studied soils are isotopically exchangeable after a 3-day equilibration. The intercomparison between experimental and modelling results evidences that single extraction with 0.43 M HNO3 solubilizes part of non-isotopically exchangeable fraction of Pb and Zn in the studied soils, and cannot be used as a surrogate for ID to assess labile Pb and Zn pools in soil. Both selective sequential extraction (SSE) and modelling reveal that Mn oxides are the predominant sorption surface for Pb in the studied soils; while Zn is predicted to be mainly associated with soil organic matter in the soil with low pH and Fe/Mn oxides in the soils with high pH. Multi-surface modelling can provide a reasonable prediction of Pb and Zn adsorption onto different soil constituents for the most of the studied soils. The modelling could be a promising tool to decipher the underlying mechanism that controls metal reactivity in soil, but the submodel for Mn oxides should be incorporated and the model parameters, especially for the 2-pK diffuse layer model for Mn oxides, should be updated in the further studies

The increasing production of nanoparticles has raised strong concerns regarding their environmental release. In life cycle scenarios of nanoparticles, marine systems constitute one of the main final compartments, and the fate of nanoparticles in marine environments needs to be assessed. The dissolution kinetics of commercial uncoated and organic-coated ZnO nanoparticles in synthetic seawater were investigated using the Donnan membrane technique and 1000-Da pore size ultrafiltration. Uncoated nanoparticles reach a maximum dissolution within the first hour, approximately 24% of total ZnO at pH 8.2, and 4% at pH 7.7, followed by secondary carbonated phase precipitation (hydrozincite) until the system reaches a steady state after 30 d of interaction. Assuming a pseudo first-order kinetics for hydrozincite precipitation allowed calculation of kinetics constant values k0 p of 208 10 4mol L 1 h 1 15 10 4 mol L 1 h 1 (standard deviation) at pH 7.7, and 57 10 4mol L 1 h 1 11 10 4 mol L 1 h 1 at pH 8.2. The presence of an organic coating drastically modifies the life cycle of nanoparticles, with a maximum dissolution reached after 7 d of interaction, followed by a stationary phase lasting from 1 wk to 3 wk, and a subsequent Zn carbonate precipitation until a steady state is reached after 1.5 mo. Monitoring changes in the physicochemical parameters of nanoparticles after exposure to synthetic seawater constitutes an important step in predicting their fate in environmental systems, with major implications for ecotoxicological studies in which metallic speciation is required for toxicity evaluation

In this study an innovative approach is proposed to predict the relative contribution of each mineral phase to the total metal availability in soils, which, in other words, could be called the available metal fractionation. Through the use of isotopic exchange kinetics (IEK) performed on typical Ni bearing phases (i.e., two types of serpentines, chlorite, smectite, goethite, and hematite) the isotopic exchange and metal-solid interaction processes are connected, considering both the thermodynamic and kinetic aspects. Results of Ni IEK experiments on mineral phases are fitted with a pseudo-first order kinetic model. For each Ni bearing phase, this allows to (i) determine the number and size of exchangeable pools (ENi(i)), (ii) assess their corresponding kinetic constants (k(i)), and (iii) discuss the mechanism of Ni isotopic exchange at mineral surfaces. It is shown that all the phases investigated, with the only exception of hematite, present at least two distinct reactive pools with significantly differe...

In this work, modelling of Eu(III) speciation in a ternary system, i.e., in presence of purified Aldrich humic acid (PAHA) and α-Al2O3, is presented. First, the mineral surface charge is measured by potentiometric titrations and then described using the CD–MUSIC model. This model is also used to describe Eu(III) binding to the α-Al2O3 surface at different pH values, ionic strength and mineral concentrations. Time-resolved luminescence spectroscopy (TRLS) is then used to study the binding of Eu(III) to PAHA at pH 4 with different humic acid concentrations. The spectra are used to calculate a spectroscopic “titration curve”, used to determine Eu(III)/PAHA binding parameters in the NICA-Donnan model. Following a previous study (Janot et al., Water Res. 46, 731–740), modelling of the ternary system is based upon the definition of two PAHA pools where one fraction remains in solution and the other is adsorbed onto the mineral surface, with each possessing different proton and metal binding parameters. The modification of protonation behaviour for both fractions is examined using spectrophotometric titrations of the non-adsorbed PAHA fraction at different organic/mineral ratios. These data are then used to describe Eu(III) interactions in the ternary system: Eu(III) repartitioning in the ternary system is calculated for different pH, ionic strength and PAHA concentrations, and results are compared to experimental observations. The model is in good agreement with experimental data, except at high PAHA fractionation rates. Results show that organic complexation dominates over a large pH range, with the predominant species existing as the surface-bound fraction. Above pH 8, Eu(III) seems to be mostly complexed to the mineral surface, which is in agreement with previous spectroscopic observations (Janot et al., Environ. Sci. Technol. 45, 3224–3230).

International audience; This study examined the evolution of absorbance and fluorescence spectra of standard Suwannee River fulvic acid (SRFA) induced by its interactions with iron and aluminum. The results show that changes of SRFA absorbance are associated with a consistent response of the carboxylic and phenolic functional groups to iron and aluminum forming bonds with these groups, and their deprotonation induced by such binding. The observed changes of SRFA absorbance were quantified via the use of DSlope(325-375) parameter that determines the behavior of the slope of logarithms of SRFA absorbance in the range of wavelengths 325 -375 nm in the presence of varying concentrations of iron or aluminum. DSlope(325-375) values were correlated linearly with the concentration of SRFA-bound iron and aluminum determined using either NICA-Donnan or Stockholm Humic Model (SHM) but the correlation was stronger for the former model (R-2 > 0.98). The slopes of these correlations were similar for both iron and aluminum concentrations

In the tropical zone, small watersheds are affected by intense meteorological events. These events play an important role in the erosion of soils and therefore on the associated organic carbon fluxes to the ocean. We studied the geochemistry of three small watersheds around the Basse-Terre volcanic Island (French West Indies, FWI) during a four years period, by measuring dissolved organic carbon (DOC), particulate organic carbon (POC) and dissolved inorganic carbon (DIC) concentrations. The mean annual yields ranged between 8.1–15.8 tC km − 2 yr − 1 , 1.9–8.6 tC km − 2 yr − 1 and 8.1–25.5 tC km − 2 yr − 1 for DIC, DOC and POC, respectively. Floods and extreme floods (i.e., extremely high discharge associated to extreme meteorological events such as cyclones or tropical storms) account for 42.6% of the yearly water flux and represent 54.5% of the annual DOC flux, and more than 85% of the annual POC flux. The DIC flux occurs essentially during low water levels with 75% of the annual flux. During low water levels and floods, the dissolved carbon is exported in majority under the inorganic form (DIC/DOC = 2.6 ± 2.1), while during extreme floods, the dissolved carbon transported is mostly organic (DIC/DOC = 0.7 ± 0.2). The partial “residence time” taking into account only the physical processes (erosion and transport) in Guadeloupean soils has been estimated between 381 and 1000 years. These relatively short times could be linked to the intensity of meteorological events rather than the frequency of meteorological events. The total export of organic carbon coming from small tropical and volcanic mountainous rivers is estimated at 2.4 ± 0.6 MtC yr − 1 for DOC and at 5.9 ± 2.4 MtC yr − 1 for POC, emphasizing that these carbon fluxes are significant and should be included in global carbon budgets. In addition, the quality of terrestrial organic matter (POC/DOC, and C/N ratios) arriving to the ocean is different from the one of large river origin. These inputs are responsible for a fast transport of terrestrial organic matter to the ocean but their effect on regional and global carbon budget is still a matter of debate.

International audience; This study examined the binding of copper(II) by Suwannee River fulvic acid (SRFA) using the method of differential absorbance that was used at environmentally-relevant concentrations of copper and SRFA. The pH- and metal-differential spectra were processed via numeric deconvolution to establish commonalities seen in the changes of absorbance caused by deprotonation of SRFA and its interactions with copper(II) ions. Six Gaussian bands were determined to be present in both the pH- and Cu-differential spectra. Their maxima were located, in the order of increasing wavelengths at 208 nm, 242 nm, 276 nm, 314 nm, 378 nm and 551 nm. The bands with these maxima were denoted as A0, A1, A2, A3, A4 and A5, respectively. Properties of these bands were compared with those existing in the spectra of model compounds such as sulfosalicylic acid (SSA), tannic acid (TA), and polystyrenesulfonic acid-co-maleic acid (PSMA). While none of the features observed in differential spectra of the model compound were identical to those present in the case of SRFA, Gaussian bands A1, A3 and possibly A2 were concluded to be largely attributable to a combination of responses of salicylic- and polyhydroxyphenolic groups. In contrast, bands A4 and A5 were detected in the differential spectra of SRFA only. Their nature remains to be elucidated. To examine correlations between the amount of copper(II) bound by SRFA and changes of its absorbance, differential absorbances measured at indicative wavelengths 250 nm and 400 nm were compared with the total amount of SRFA-bound copper estimated based on Visual MINTEQ calculations. This examination showed that the differential absorbances of SRFA in a wide range of pH values and copper concentrations were strongly correlated with the concentration of SRFA-bound copper. The approach presented in this study can be used to generate in situ information concerning the nature of functional groups in humic substances engaged in interactions with metals ions. This information can be useful for further elaboration and development of detailed theoretic models that describe the complexation of metals in the environment

The central Amazon floodplains are particularly productive ecosystems, where a large diversity of organic carbon sources are available for aquatic organisms. Despite the fact that C-4 macrophytes generally produce larger biomasses than C-3 macrophytes, food webs in the central Amazon floodplains appear dominantly based on a C-3 carbon source. In order to investigate the respective fate and degradation patterns of C-4 and C-3 aquatic plant-derived material in central Amazon floodplains, we developed a 23-days batch experiment. Fatty acid and carbon concentrations as well as stable isotope compositions were monitored over time in 60 L tanks. These tanks contained Amazon water, with different biomasses of C-3 and C-4 macrophyte, representative of in situ densities occurring in central Amazon floodplains. In the C-4 Paspalum repens treatments, organic (POC, DOC) and inorganic carbon (DIC) got rapidly enriched in C-13, whereas in the C-3 Salvinia auriculata treatments, POC and DOC showed little change in concentration and isotopic composition, and DIC got depleted in C-13. The contribution of P. repens to POC and DOC was estimated to reach up to 94.2 and 70.7%, respectively. In contrast, no differences were reported between the C-3 S. auriculata and control treatments, an observation attributed to the lower C-3 biomass encountered in the field, to a slower degradation rate of C-3 compared to C-4 compounds, and to similar isotopic compositions for river POC and DOC, and C-3 compounds. The C-13 enrichments of POC, DOC, and DIC from P. repens treatments were attributed to an enhanced bacterially-mediated hydrolysis and mineralization of C-4 material. Evolutions of bacterial abundance and branched fatty acid concentrations confirmed the role of heterotrophic microbial communities in the high P. repens decomposition rate. Our experiment highlights the predominant role of C-4 aquatic plants, as a large source of almost entirely biodegradable organic matter available for heterotrophic activity and CO2 outgassing to the atmosphere.

Trace element (TE) speciation modelling in soil solution is controlled by the assumptions made about the soil solution composition. To evaluate this influence, different assumptions using Visual MINTEQ were tested and compared to measurements of free TE concentrations. The soil column Donnan membrane technique (SC-DMT) was used to estimate the free TE (Cd, Cu, Ni, Pb and Zn) concentrations in six acidic soil solutions. A batch technique using DAX-8 resin was used to fractionate the dissolved organic matter (DOM) into four fractions: humic acids (HA), fulvic acids (FA), hydrophilic acids (Hy) and hydrophobic neutral organic matter (HON). To model TE speciation, particular attention was focused on the hydrous manganese oxides (HMO) and the Hy fraction, ligands not considered in most of the TE speciation modelling studies in soil solution. In this work, the model predictions of free ion activities agree with the experimental results. The knowledge of the FA fraction seems to be very useful, especially in the case of high DOM content, for more accurately representing experimental data. Finally, the role of the manganese oxides and of the Hy fraction on TE speciation was identified and, depending on the physicochemical conditions of the soil solution, should be considered in future studies.

International audience; Soils and ore samples influenced by mining and metallurgical activity were collected in ultramafic soils (UM) complexes of Barro Alto and Niquelândia, in order to determine the contribution of each Ni bearing phases to the total exchangeable pool of Ni, and to point out if this pool was affected by anthropic activities. For this purpose, the IEK-model previously developed by the group (Zelano et al., submitted) was applied, on the basis of IEK experiments performed on pure typical Ni scavengers (serpentines, chlorite, smectite and iron oxydes) from ultramafic systems. For each typical scavenger, this model describes the percentage of Ni associated to exchangeable pool(s) as well as their corresponding kinetic constant(s) of exchange. The mineralogical composition of soil and ore samples and Ni solid speciation were first determined, and the IEK-model was applied on these bases. In almost all samples, an important contribution of serpentine to Ni exchangeable pool was highlighted, ranging between 10% and 45%. The important amount of organic matter (OM) in one of the studied soil samples, allowed to extrapolate generic OM ENi and k parameters, which were introduced in the IEK-model to improve its predictive capability. Obtained results provided evidences of how even a small content (3 wt%) of organic carbon (OC), can represent an important contribution of OM to the total ENi pool (60%). In the investigated ore samples, up to the 60% of ENi was attribute to smectite, responsible for fast ENi pool kinetic evolution. In addition, the model highlighted the role of the Fine Black Ash (FBA), by-products of the pyrometallurgical activity, detected into a soil sample, that is responsible for the 15% of ENi. This approach allowed to determine, for the first time, the relative contribution of each Ni bearing phase to the total exchangeable pool, in terms of concentration and kinetics.

International audience; Europium speciation is investigated by time-resolved luminescence spectroscopy (TRLS) in the presence of Suwannee River fulvic acid (SRFA). From complexation isotherms built at different total Eu(III) concentrations, pH values, ionic strength, and SRFA concentrations, it appears that two luminescence behaviors of Eu(III) are occurring. The first part, at the lowest CSRFA values, is showing the typical luminescence evolution of Eu(III) complexed by humic substances—i.e. the increase of the asymmetry ratio between the 5 D0→ 7 F2 and 5 D0→ 7 F1 transitions up to a plateau—, and the occurrence of a bi-exponential decay—the first decay being faster than free Eu 3+. At higher CSRFA, a second luminescence mode is detected as the asymmetry ratio is increasing again after the previous plateau, and could correspond to the formation of another type of complex, and/or it can reflect a different spatial organization of complexed europium within the SRFA structure. The luminescence decay keeps on evolving but link to hydration number is not straightforward due to quenching mechanisms. The Eu(III) chemical environment evolution with CSRFA is also ionic strength dependent. These observations suggest that in addition to short range interactions—intra-particulate complexation—, there might be interactions at longer range—inter-particulate repulsion—between particles that are complexing Eu(III) at high CSRFA. These interactions are not yet accounted by the different complexation models.

International audience; Zinc isotopes have been studied along two smelter-impacted soil profiles sampled near one of the largest Pb and Zn processing plants in Europe located in northern France, about 50 km south of Lille. Mean delta(66)Zn values along these two soil profiles range from +0.22 +/- 0.17 parts per thousand (2 sigma) to +0.34 +/- 0.17 parts per thousand (2 sigma) at the lowest horizons and from +0.38 +/- 0.45 parts per thousand (2 sigma) to +0.76 +/- 0.14 parts per thousand (2 sigma) near the surface. The delta(66)Zn values in the lowest horizons of the soils are interpreted as being representative of the local geochemical background (mean value +0.31 +/- 0.38 parts per thousand), whereas heavier delta(66)Zn values near the surface of the two soils are related to anthropogenic Zn. This anthropogenic Zn occurs in the form of franklinite (ZnFe(2)O(4))-bearing slag grains originating from processing wastes at the smelter site and exhibiting delta(66)Zn values of +0.81 +/- 0.20 parts per thousand (2 sigma). The presence of franklinite is indicated by EXAFS analysis of the topsoil samples from both soil profiles as well as by micro-XANES analysis of the surface horizon of a third smelter-impacted soil from a distant site. These results indicate that naturally occurring Zn and smelter-derived Zn exhibit significantly different delta(66)Zn values, which suggests that zinc isotopes can be used to distinguish between geogenic and anthropogenic sources of Zn in smelter-impacted soils. In addition to a possible influence of additional past sources of light Zn (likely Zn-sulfides and Zn-sulfates directly emitted by the smelter), the light delta(66)Zn values in the surface horizons compared to smelter-derived slag materials are interpreted as resulting mainly from fractionation processes associated with biotic and/or abiotic pedological processes (Zn-bearing mineral precipitation, Zn complexation by organic matter, and plant uptake of Zn). This conclusion emphasizes the need for additional Zn isotopic studies before being able to use Zn isotopes to trace sources and pathways of this element in surface environments

International audience; Eu(III) sorption onto $\alpha$-Al$_2$O$_3$ in the presence of purified Aldrich humic acid (PAHA) is studied by batch experiments and time-resolved laser-induced luminescence spectroscopy of Eu(III). Experiments are conducted at varying pH, at 0.1 mol/L NaClO$_4$, 10$^{-6}$ mol/L Eu(III), 1 g/L $\alpha$-Al$_2$O$_3$ and 28 mg/L PAHA, which assured a complete Eu(III)-PAHA complexation. Adsorption of Eu(III) presents the expected pH-edge at 7, which is modified by addition of PAHA. Presence of Eu(III) slightly increases PAHA sorption throughout the pH range. The evolutions of luminescence spectra and decay times of the binary systems, that is, Eu(III)/$\alpha$-Al$_2$O$_3$ and Eu(III)/PAHA, indicate a progressive surface- and humic-complexation with increasing pH. The typical biexponential luminescence decay in Eu(III)/PAHA system is also recorded; the fastest deactivation depending barely on pH. In ternary Eu(III)/PAHA/$\alpha$-Al$_2$O$_3$ system, the existence of a luminescence biexponential decay for all pH means that Eu(III) is always in the direct neighborhood of the humic substance. Below pH 7, the spectra of the ternary system (Eu(III)/PAHA/$\alpha$-Al$_2$O$_3$) are not different from the ones of Eu(III)/PAHA system, implying the same complex symmetry. Nevertheless, the increase of luminescence decay time points to a change in PAHA conformation onto the surface