Impacts of Highway Runoff on Metal Contamination Including Rare Earth Elements in a Small Urban Watershed: Case Study of Bordeaux Metropole (SW France).

High temporal resolution sampling of runoff (15 samples/4 h) and river water (24 samples/24 h) was performed during a major rainstorm (41 mm/4 h) in the Bordeaux Metropole, after a dry and high vehicle-density period. Runoff was sampled at the outlet of one collector draining Northern Bordeaux Highway (NBH; 80,000-93,000 vehicles/day) and river water in the downstream Jalle River. The studied metals, including priority and emergent (Rare Earth Elements [REEs]) contaminants, showed major temporal and spatial variations in the dissolved and particulate concentrations. Hierarchical cluster analyses distinguished metal groups, reflecting different: (i) sources (i.e., automotive traffic: Zn-Cu-Ce and wastewater treatment plant: Cd-Ag-Gd) and/or (ii) processes (i.e., groundwater dilution by rainwater and sorption processes). The contribution of the particulate fraction to total metal fluxes was predominant in the NBH collector (except for Sr and Mo) and highly variable in the Jalle River, where the highest particulate metal loads were due to the export of road dusts exported by the NBH collector. Metal fluxes from the NBH collector represented highly variable fractions of daily fluxes into the Gironde Estuary at the outlet of the Jalle River, depending on elements and partitioning. The resulting relative contributions ranged from: 5% (Sr) to 40% (Cu) for dissolved phases and 30% (As) to 88% (Cu) for particulate phases. The first 40 min of the event accounted for 65% of the suspended particulate matter flux (and associated particulate metals) exported by the NBH collector, whereas the respective water flux contribution was 35%. This finding clearly demonstrates the importance of monitoring the first minutes of rainy events when establishing mass balances in urban systems.

In Situ Detection of Macronutrients and Chloride in Seawater by Submersible Electrochemical Sensors.

A new submersible probe for the in situ detection of nitrate, nitrite, and chloride in seawater is presented. Inline coupling of a desalination unit, an acidification unit, and a sensing flow cell containing all-solid-state membrane electrodes allows for the potentiometric detection of nitrate and nitrite after removal of the key interfering ions in seawater, chloride and hydroxide. Thus, the electrodes exhibited attractive analytical performances for the potentiometric detection of nitrate and nitrite in desalinated and acidified seawater: fast response time ( t95 < 12 s), excellent stability (long-term drifts of <0.5 mV h-1), good reproducibility (calibration parameter deviation of <3%), and satisfactory accuracy (uncertainties <8%Diff compared to reference technique). The desalination cell, which can be repetitively used for about 30 times, may additionally be used as an exhaustive, and therefore calibration-free, electrochemical sensor for chloride and indirect salinity detection. The detection of these two parameters together with nitrate and nitrite may be useful for the correlation of relative changes in macronutrient levels with salinity cycles, which is of special interest in recessed coastal water bodies. The system is capable of autonomous operation during deployment, with routines for repetitive measurements (every 2 h), data storage and management, and computer visualization of the data in real time. In situ temporal profiles observed in the Arcachon Bay (France) showed valuable environmental information concerning tide-dependent cycles of nitrate and chloride levels in the lagoon, which are here observed for the first time using direct in situ measurements. The submersible probe based on membrane electrodes presented herein may facilitate the study of biogeochemical processes occurring in marine ecosystems by the direct monitoring of nitrate and nitrite levels, which are key chemical targets in coastal waters.

DEGRO/DGK guideline for radiotherapy in patients with cardiac implantable electronic devices.

An increasing number of patients undergoing radiotherapy (RT) have cardiac implantable electronic devices [CIEDs, cardiac pacemakers (PMs) and implanted cardioverters/defibrillators (ICDs)]. Ionizing radiation can cause latent and permanent damage to CIEDs, which may result in loss of function in patients with asystole or ventricular fibrillation. Reviewing the current literature, the interdisciplinary German guideline (DEGRO/DGK) was developed reflecting patient risk according to type of CIED, cardiac condition, and estimated radiation dose to the CIED. Planning for RT should consider the CIED specifications as well as patient-related characteristics (pacing-dependent, previous ventricular tachycardia/fibrillation). Antitachyarrhythmia therapy should be suspended in patients with ICDs, who should be under electrocardiographic monitoring with an external defibrillator on stand-by. The beam energy should be limited to 6 (to 10) MV CIEDs should never be located in the beam, and the cumulative scatter radiation dose should be limited to 2 Gy. Personnel must be able to respond adequately in the case of a cardiac emergency and initiate basic life support, while an emergency team capable of advanced life support should be available within 5 min. CIEDs need to be interrogated 1, 3, and 6 months after the last RT due to the risk of latent damage.

Evidencing the Impact of Coastal Contaminated Sediments on Mussels Through Pb Stable Isotopes Composition.

Heavily contaminated sediments are a serious concern for ecosystem quality, especially in coastal areas, where vulnerability is high due to intense anthropogenic pressure. Surface sediments (54 stations), 50 cm interface cores (five specific stations), river particles, coal and bulk Pb plate from past French Navy activities, seawater and mussels were collected in Toulon Bay (NW Mediterranean Sea). Lead content and Pb stable isotope composition have evidenced the direct impact of sediment pollution stock on both the water column quality and the living organisms, through the specific Pb isotopic signature in these considered compartments. The history of pollution events including past and present contaminant dispersion in Toulon Bay were also demonstrated by historical records of Pb content and Pb isotope ratios in sediment profiles. The sediment resuspension events, as simulated by batch experiments, could be a major factor contributing to the high Pb mobility in the considered ecosystem. A survey of Pb concentrations in surface seawater at 40 stations has revealed poor seawater quality, affecting both the dissolved fraction and suspended particles and points to marina/harbors as additional diffuse sources of dissolved Pb.

Reactivity and bioconcentration of stable cesium in a hyperturbid fluvial-estuarine continuum: A combination of field observations and geochemical modeling.

Effective, post-accidental management needs an accurate understanding of the biogeochemical behavior of radionuclides in surface environments at a regional scale. Studies on stable isotopes (element homologs) can improve this knowledge. This work focuses on the biogeochemical behavior of stable cesium (Cs) along a major European fluvial-estuarine system, the Gironde Estuary (SW France). We present results obtained from (i) a long-term monitoring (2014-2017) of dissolved (Csd) and particulate (Csp) Cs concentrations at five sites along the freshwater continuum of the Garonne watershed, (ii) Csd and Csp concentrations during four oceanographic campaigns at contrasting hydrological conditions along longitudinal profiles of the estuarine system, (iii) a 24 h cycle of Csp at the estuary mouth, and (iv) a historical trend of Cs bioconcentration in wild oysters at the estuary mouth (RNO/ROCCH, 1984-2017). In addition, we model the partitioning of Cs within the estuarine environment for clay mineral interactions via PhreeqC. At fluvial sites, we observe a geogenic dependence of the Csp and a seasonal variability of Csd, with a downstream increase of the solid-liquid partitioning (log10 Kd values from 3.64 to 6.75 L kg-1) for suspended particulate matter (SPM) < 200 mg L-1. Along the estuarine salinity gradients, Cs shows a non-conservative behavior where fresh SPM (defined as Cs-depleted particles recently put in contact with Csd) act as a Cs sink during both flood and low discharge (drought) conditions. This sorption behavior was explained by the geochemical model, highlighting the relevance of ionic strength, water and SPM residence times. However, at high salinities, the overall log10 Kd value decreases from 6.02 to 5.20 for SPM ∼300-350 mg L-1 due to the Csd oceanic endmember. Despite wild oysters showing low bioconcentration factors (∼1220 L kg-1) at the estuary mouth, they are sensitive organisms to Cs fluxes.

Contrasting platinum trajectories in three major French rivers using dated sediment cores (1910-2021): From geochemical baseline to emerging source signals.

Platinum (Pt) is a Technology Critical Element (TCE) which, since the 1990s, has been mainly used in the industry in catalytic converters for automobile emission control. Previous studies have shown Pt contamination of road-side sediments and surface sediments in urban rivers and lakes but few of them have addressed temporal variations. The present work presents historical Pt concentration trends in 137Cs-dated sediment cores from floodplains or secondary channels at the outlets of three major French watersheds (Loire, Rhone, and Seine Rivers) covering the past ∼110 years, i.e., from the 1910s to 2021. Platinum baseline levels in the sediment were estimated for the Loire River (0.76 ± 0.22 µg kg-1 for the period ∼1910-∼1955) and the Rhone River (1.64 ± 0.41 µg kg-1), and historical Pt variations seem to reflect variations in hydrodynamics and grain size composition. Since the early 2000s, Pt concentrations in the Loire and the Rhone River sediments tend to increase (>2.5 µg kg-1) and were attributed to the use of car catalytic converters, an emerging technology since the 1990s using >50 % of European Pt demand. High and variable historical Pt concentrations (up to 14.6 µg kg-1) in the Seine River sediments may reflect legacy Pt sources due to former anthropogenic activities in this watershed, such as the use of Pt-based catalysts for petroleum refinery since the end of the 1940s, coal handling and precious metals refining, probably concealing the likely presence of an emerging traffic-related Pt signal. This first comparison of historical Pt concentration trends in sediments from contrasting watersheds allows to distinguish signals originating from different natural and anthropogenic sources (background level, historical sources, road traffic).

Temporal trajectories of artificial radiocaesium 137Cs in French rivers over the nuclear era reconstructed from sediment cores.

137Cs is a long-lived man-made radionuclide introduced in the environment worldwide at the early beginning of the nuclear Era during atmospheric nuclear testing's followed by the civil use of nuclear energy. Atmospheric fallout deposition of this major artificial radionuclide was reconstructed at the scale of French large river basins since 1945, and trajectories in French nuclearized rivers were established using sediment coring. Our results show that 137Cs contents in sediments of the studied rivers display a large spatial and temporal variability in response to the various anthropogenic pressures exerted on their catchment. The Loire, Rhone, and Rhine rivers were the most affected by atmospheric fallout from the global deposition from nuclear tests. Rhine and Rhone also received significant fallout from the Chernobyl accident in 1986 and recorded significant 137Cs concentrations in their sediments over the 1970-1985 period due to the regulatory releases from the nuclear industries. The Meuse River was notably impacted in the early 1970s by industrial releases. In contrast, the Seine River display the lowest 137Cs concentrations regardless of the period. All the rivers responded similarly over time to atmospheric fallout on their catchment, underlying a rather homogeneous resilience capacity of these river systems to this source of contamination.

First assessment of Rare Earth Element organotropism in Solea solea in a coastal area: The West Gironde Mud Patch (France).

Few studies exist on concentration and internal distribution of Rare Earth Elements (REEs) in marine fishes. REEs organotropism was determined in common sole (Solea solea) from the West Gironde Mud Patch (WGMP; N-E Atlantic Coast, France). The highest ∑REEs concentrations occurred in liver (213 ± 49.9 µg kg-1 DW) and gills (119 ± 77.5 µg kg-1 DW) followed by kidneys (57.7 ± 25.5 µg kg-1 DW), whereas the lowest levels were in muscles (4.53 ± 1.36 µg kg-1 DW) of Solea solea. No significant age- or sex-related differences were observed. The organotropism varied among groups of REEs. Light and heavy REEs preferentially accumulated in liver and gills, respectively. All considered organs showed different normalized REEs patterns, suggesting differences in internal distribution processes between organs. Further work should address: (1) baseline levels worldwide, and (2) factors controlling uptake and organ-specific concentration of REEs.

Impact of metallurgy tailings in a major European fluvial-estuarine system: Trajectories and resilience over seven decades.

Tailings containing mining and ore treatment waste, accumulated over long time periods are major contaminant sources at the watershed scale and may seriously impair environmental quality of river-sea continuums. A critical review of existing work in different disciplines addressing the multi-metal contamination of the Gironde Watershed, a major fluvial-estuarine model system representative of many other systems worldwide, has provided a condensed, yet pertinent overview on various aspects of this environmental problem. Combining long-term observation and contamination records from different environmental archives, there is a clear trend towards resilience for the main historical contaminants (Cd, Zn, Pb and Cu), yet suggesting that resilience needs appropriate management of both, tailings as the initial source and contaminated sediments acting as temporary metal traps which may transform into delayed sources. Contaminated sediment management is an increasingly important challenge due to (i) successful remediation at the contamination source itself (ii) global-change induced factors and strategies and (iii) lacking coordination of actions between upstream and downstream parts of the fluvial-estuarine continuum. Less studied and emerging metallic contaminants show recent trends in sediments and biota that are decoupled from the legacy contaminant trajectories due to recent sources and applications, suggesting that further work is needed to assess their potential impact on the environmental quality of the Gironde fluvial-estuarine system and that of other systems, especially in a context of worldwide rapidly growing mining activity and metal use.

Historical mass balance of cadmium decontamination trends in a major European continent-ocean transition system: Case study of the Gironde Estuary.

Despite the effective remediation efforts following the end of the metallurgic activity thirty years ago upstream the Lot River watershed, the levels of cadmium (Cd) accumulated in wild oysters from the downstream Gironde Estuary still exceed nowadays the admissible human consumption limit (5 mg/kg, d.w.). The main goal of this work is to quantify the role of sediments as long-term intra-estuarine sources or sinks of Cd and the transport of this contaminant towards the estuary mouth taking as case study the example of the highly turbid Gironde Estuary. The original estimation for the annual net fluxes of the suspended particulate matter ( [Formula: see text] and particulate Cd ( [Formula: see text] ) presented in this work between 1990 and 2020 indicates that 80% of the Cd discharged into the ocean is in dissolved form (Cdd). The values of [Formula: see text] vary proportionally to those of [Formula: see text] and ranged between 0.1 and 1.4 t/y, with a ten-year average decreasing from 0.8 to 0.6 t/y for the past 30 years. The differences between ten-year total (Cdp + Cdd) gross and net fluxes show that Cd has effectively been stored in estuarine sediments. This Cd storage was of about 43, 22 and 13 t for the 1990s, 2000s and 2010s, respectively. However, during years of low gross fluxes, estuarine sediments act as additional, secondary sources of bio-available/dissolved Cd into the water column, potentially relating to the continued observations of high Cd concentrations in wild oysters at the estuary mouth. In addition to the natural solubility of Cdp along the salinity and turbidity gradients of the estuary, natural and anthropogenic remobilization of bottom sediment particles further contribute to its mobilization from the particle phase, along with other numerous inorganic/organic pollutants. The mass balances presented in this work could support a new sediment management policy potentially more beneficial to the estuarine ecosystem.

High purity chemical etching and thermal passivation process for Ge(001) as nanostructure template.

An advanced two-step cleaning process of the Ge(001) surface for nanoscience requirements is presented. First, wet-chemical etching with a variant of the Piranha solution (H(2)SO(4), H(2)O(2), H(2)O) is used to remove contaminants as well as the native oxide layer. Second, passivation of the surface is achieved by a rapid thermal oxidation step, leading to a homogeneous protective oxide layer. The thickness of the oxide layer is tuned to be thick enough to protect the surface, yet thin enough to be completely removed by thermal treatment in ultra-high vacuum. The application of this recipe results in an outstandingly clean and atomically flat surface, with carbon contamination at the detection limit of x-ray photoelectron spectroscopy. Scanning tunneling microscopy and electron diffraction reveal a long range ordered surface with typical terrace diameters of ~100 nm, suitable for the growth of atomic-scale nanostructures.

Tracing cadmium contamination kinetics and pathways in oysters (Crassostrea gigas) by multiple stable Cd isotope spike experiments.

Laboratory experiments using stable Cd isotopes ((110)Cd and (112)Cd) were conducted to separately and simultaneously characterize Cd accumulation in different tissues of Pacific oysters (Crassostrea gigas) via the (i) trophic and (ii) direct pathways. For this, we exposed juvenile oysters to (110)Cd-spiked seawater ((110)Cd: 2 µg l(-1); constant level) and (112)Cd-spiked food (Thalassiossera weissflogii, (112)Cd: 2 µg l(-1) in 35×10(3) cells/oyster/L) in four experimental treatment groups, each containing 6 oysters, for 21 days with constant trophic feeding. These Cd contamination levels were ∼10 times lower than those typically used in experimental accumulation studies. Three oysters per treatment group were dissected every 7 days with separate sampling of the gills, digestive gland and the rest of the body. Metallothioneins were analysed in the digestive gland and gills. Cadmium concentrations and isotope ratios were measured in water (daily) and tissues (weekly) by GF-AAS and ICP-MS. The observed time-dependant evolution in Cd concentrations and (110)Cd/(114)Cd and (112)Cd/(114)Cd isotope ratios clearly revealed the bio-accumulation short-term kinetics and pathways of Cd contamination in the different tissues. Under the experimental conditions, significantly changed isotope ratios in gills and the digestive gland of oysters suggested rapid and efficient contamination by (110)Cd derived from direct exposure followed by internal Cd transfer between organs. Trophic contamination became measurable after 14 days of exposure corresponding to a trophic transfer rate of 1%. Constant metallothionein levels during the experiment suggested that the initially present metallothionein levels were sufficient to deal with the experimental Cd exposure.

Ultra-trace interference-free analysis of palladium in natural waters by ICP-MS after on-line matrix separation and pre-concentration.

The determination of palladium (Pd) in environmental samples by ICP-MS is challenging as all its isotopes are extensively interfered due to isobaric (e.g. 110Cd on 110Pd, 106Cd on 106Pd), polyatomic (e.g. 92Mo16O on 108Pd, 89Y16O on 105Pd) and doubly-charged (e.g. 208Pb2+ on 104Pd) species formed in the plasma from elements usually present at concentrations several orders of magnitude higher. As a result, the determination of Pd in natural waters is extremely scarce despite is has been proven that this metal is subject to a significant anthropogenic impact mainly linked to its use in catalytic converters in motor vehicles. In order to overcome this situation, we have developed an ultra-trace interference-free methodology for the determination of Pd in natural waters by ICP-MS after on-line matrix separation and preconcentration. The method is based on the strong affinity of Pd towards a commercially-available carboxymethylated polyethylenimine resin, which also has the ability to retain most of the transition metals. However, Pd is not eluted from the resin at typical elution conditions (e.g. 2 M HNO3, which removes all the interference-forming metals), but this can be attained by passing a diluted thiourea solution (10-3 M). Therefore, the interference-free on-line determination of Pd in natural waters was successfully achieved using a two-step elution procedure. Procedural blank values were 0.012 ±â€¯0.003 ng kg-1 (n = 6), which results in a detection limit of 0.010 ng kg-1, allowing the determination of dissolved Pd in natural samples at low, ambient concentrations. The optimized methodology was applied to determine the concentrations of Pd in the Gironde estuary, which represents the first dissolved Pd profile along an estuarine salinity gradient and one of the first dataset of Pd concentrations in natural waters at ambient levels in almost 4 decades. The simplicity of the preconcentration setup and the possibility for its automation offers new analytical opportunities, which will be useful for future studies aiming to improve our understanding of the behavior of Pd in natural waters.

Cell and tissue level responses in mussels Mytilus galloprovincialis dietarily exposed to PVP/PEI coated Ag nanoparticles at two seasons.

Silver nanoparticles (Ag NPs) are present in numerous consumer products due to their antimicrobial and other unique properties, thus concerns about their potential input into aquatic ecosystems are increasing. Toxicity of Ag NPs in waterborne exposed aquatic organisms has been widely investigated, but studies assessing the potential toxic effects caused after ingestion through the food web, especially at low realistic concentrations, remain scarce. Moreover, it is not well known whether season may influence toxic effects of Ag NPs. The main objective of this study was to determine cell and tissue level responses in mussels Mytilus galloprovincialis dietarily exposed to poly-N-vinyl-2-pirrolidone/polyethyleneimine (PVP/PEI) coated 5 nm Ag NPs for 1, 7 and 21 days both in autumn and spring. Mussels were fed every day with microalgae Isochrysis galbana exposed for 24 h to a low dose (1 µg Ag/L Ag NPs) in spring and to a higher dose (10 µg Ag/L Ag NPs) in spring and autumn. Mussels fed with microalgae exposed to the high dose accumulated Ag significantly after 21 days in both seasons, higher levels being measured in autumn compared to spring. Intralysosomal metal accumulation measured in mussel digestive gland and time- and dose-dependent reduction of mussels health status was similar in both seasons. DNA strand breaks increased significantly in hemocytes at both exposure doses along the 21 days in spring and micronuclei frequency showed an increasing trend after 1 and 7 days of exposure to 1 µg Ag/L Ag NPs in spring and to 10 µg Ag/L in both seasons. Values decreased after 21 days of exposure in all the cases. In conclusion, PVP/PEI coated 5 nm Ag NPs ingested through the food web were significantly accumulated in mussel tissues and caused adverse cell and tissue level effects both in autumn and in spring.

Advanced multichannel submersible probe for autonomous high-resolution in situ monitoring of the cycling of the potentially bioavailable fraction of a range of trace metals.

We report here on the development and application of a submersible, compact, low power consumption, integrated multichannel trace metal sensing probe (TracMetal). This probe is unique in that it allows high-resolution, simultaneous in-situ measurements of the potentially bioavailable (so-called dynamic) fraction of Hg(II), As(III), Cd(II), Pb(II), Cu(II), Zn(II). The TracMetal incorporates nanostructured Au-plated and Hg-plated gel-integrated microelectrode arrays. In addition to be selective to the fraction of metal potentially bioavailable, they offer protection against fouling and ill-controlled convective interferences. Sensitivities in the low pM for Hg(II) and sub-nM for the other target trace metals is achieved with precision ≤ 12%. The TracMetal is capable of autonomous operation during deployment, with routines for repetitive measurements (1-2 h-1), data storage and management, data computer visualization, and wireless data transfer. The system was successfully applied in the Arcachon Bay, to study the temporal variation of the dynamic fraction of the trace metals targeted. The in situ autonomous TracMetal measurements were combined with in situ measurements of the master bio-physicochemical parameters and sample collection for complementary measurements of the dissolved metal concentrations, organic matter concentrations and proxy for biological activities. The integration of all data revealed that various biotic and abiotic processes control the temporal variation of the dynamic fractions of the target metals (Medyn). The difference in the percentage of the dynamic forms of the metals studied and the short-term processes influencing their variation highlight the TracMetal potentiality as metal bioavailability-assessment sentinel to achieve comprehensive environmental monitoring of dynamic aquatic systems.

Design and realization of topological Dirac fermions on a triangular lattice.

Large-gap quantum spin Hall insulators are promising materials for room-temperature applications based on Dirac fermions. Key to engineer the topologically non-trivial band ordering and sizable band gaps is strong spin-orbit interaction. Following Kane and Mele's original suggestion, one approach is to synthesize monolayers of heavy atoms with honeycomb coordination accommodated on templates with hexagonal symmetry. Yet, in the majority of cases, this recipe leads to triangular lattices, typically hosting metals or trivial insulators. Here, we conceive and realize "indenene", a triangular monolayer of indium on SiC exhibiting non-trivial valley physics driven by local spin-orbit coupling, which prevails over inversion-symmetry breaking terms. By means of tunneling microscopy of the 2D bulk we identify the quantum spin Hall phase of this triangular lattice and unveil how a hidden honeycomb connectivity emerges from interference patterns in Bloch px ± ipy-derived wave functions.

Corbicula fluminea: A sentinel species for urban Rare Earth Element origin.

The increase in the global population, coupled with growing consumption of Rare Earth Elements (REEs), has led to increasing transfer of these emerging contaminants into the environment, particularly through the effluents from wastewater treatment plants (WWTP). The objectives of this study were to determine the geochemical quality of a French river subject to strong urban pressure (the Jalle River in the Bordeaux area) and to examine the bioavailability of natural and anthropogenic REEs in a model species of freshwater bivalve, the Asian clam Corbicula fluminea. To this end, two fractions (dissolved and total) of the water from the Jalle River were sampled and the bivalves were exposed by in situ caging during a three-month monitoring period. The REE patterns obtained showed the presence of Gadolinium (Gd) anomalies in the dissolved and total fractions as well as in Corbicula fluminea. The apparent bioavailability of natural REEs was in the following order for the dissolved fraction: Medium REEs (MREEs) > Light REEs (LREEs) > Heavy REEs (HREEs) and for the particulate fraction: MREEs > LREEs = HREEs. These results highlight the importance of the particulate fraction in the study of the bioavailability of REEs in bivalves. An increase of anthropogenic Gd (Gdanth) was observed in the dissolved fraction between the upstream site (3.4 ng.L-1) and the WWTP Downstream site (48.4 ng.L-1). The Gd anomaly observed in the water was also observed in Corbicula fluminea with a significant increase in the bioaccumulation of Gdanth, from 1.5 ± 1 ng.gDW-1 upstream to 4.1 ± 0.7 ng.gDW-1 downstream of the WWTP effluents, thus confirming the enhanced bioavailability of medical-origin Gd to freshwater bivalves. This study strongly suggests that Corbicula fluminea can be used as a sentinel species in the monitoring of Gd contamination of medical origin. It would thus appear important to consider the potential entry of this contaminant into the human food chain via other, commercially exploited bivalve species.

Tin-113 and Selenium-75 radiotracer adsorption and desorption kinetics in contrasting estuarine salinity and turbidity conditions.

Batch experiments were performed to study adsorption and desorption of 75Se and 113Sn radiotracers at environmentally representative concentrations of ~0.3 ng L-1 and ~3 ng L-1, respectively. The radiotracers were incubated with wet bulk sediments from the Gironde Estuary and the Rhône River, combining freshwater and coastal seawater salinity (S = 0, S = 32) and three different Suspended Particulate Matter (SPM) concentrations (10 mg L-1, 100 mg L-1, 1000 mg L-1) to simulate six hydrologically contrasting situations for each particle type. Results showed no measurable adsorption for 75Se under the experimental conditions, whereas >90% of 113Sn rapidly adsorbed onto the particles during the first hours of exposure. Adsorption efficiency increased with increasing SPM concentration and seemed to be slightly greater for the Rhône River sediments, potentially related to the intrinsic mineral composition. Desorption of spiked sediments exposed to filtered, unspiked freshwater and seawater only occurred for 113Sn (<15% of the previously adsorbed 113Sn) in the Garonne River sediments. This study provides insights to the potential environmental behaviour of hypothetical radionuclide releases of Se and Sn into highly dynamic and contrasting aquatic systems. Multiple accidental scenarios for the case of the Gironde Estuary and the Rhône River are discussed. These scenarios suggest that the environmental fate of soluble radionuclides like Se will be associated to water hydrodynamics and potentially more bioavailable whereas highly particle-active radionuclides like Sn will follow natural river/estuarine sedimentary regimes. Information on reactivity of radionuclides is important for improving the precision of current approaches aiming at modelling environmental radionuclide dispersion in continent-ocean transition systems.

Organotropism and biomarker response in oyster Crassostrea gigas exposed to platinum in seawater.

Platinum (Pt) is a technology critical element (TCE) for which biogeochemical cycles are still poorly understood. This lack of knowledge includes Pt effects on marine organisms, which proved to be able to bioconcentrate this trace element. Oysters Crassostrea gigas were exposed to stable Pt isotope spiked daily in seawater for 35 days. Seawater was renewed daily and spiked (with Pt(IV)) to three nominal Pt concentrations (50, 100, and 10,000 ng L-1) for two replicate series. Organotropism study revealed that gills, and to a lesser extent mantle, are the key organs regarding Pt accumulation, although a time- and concentration-dependent linear increase in Pt levels occurred in all the organs investigated (i.e., digestive gland, gonads, gills, mantle, and muscle). In oysters exposed to Pt concentrations of 10,000 ng L-1, significant biomarker impairments occurred, especially at cellular levels. They reflect altered lipofuscin and neutral lipid contents, as well as intralysosomal metal accumulation. These observations were attributed to activation of excretion/detoxification mechanisms, including Pt elimination through feces and clearly support the importance of the digestive gland in the response to direct Pt exposure. Despite relatively constant condition index, the integrative biological response (IBR) index suggests a generally decreasing health status of oysters.

Assessment of metal contamination in a small mining- and smelting-affected watershed: high resolution monitoring coupled with spatial analysis by GIS.

The Riou Mort River watershed (SW France), representative of a heavily polluted, small, heterogeneous watershed, represents a major source for the polymetallic pollution of the Lot-Garonne-Gironde fluvial-estuarine system due to former mining and ore-treatment activities. In order to assess spatial distribution of the metal/metalloid contamination in the watershed, a high resolution hydrological and geochemical monitoring were performed during one year at four permanent observation stations. Additionally, thirty-five stream sediment samples were collected at representative key sites and analyzed for metal/metalloid (Cd, Zn, Cu, Pb, As, Sb, Mo, V, Cr, Co, Ni, Th, U and Hg) concentrations. The particulate concentrations in water and stream sediments show high spatial differences for most of the studied elements suggesting strong anthropogenic and/or lithogenic influences; for stream sediments, the sequence of the highest variability, ranging from 100% to 300%, is the following: Mo < Cu < Hg < As < Sb < Cd < Zn < Pb. Multidimensional statistical analyses combined with metal/metalloid maps generated by GIS tool were used to establish relationships between elements, to identify metal/metalloid sources and localize geochemical anomalies attributed to local geochemical background, urban and industrial activities. Finally, this study presents an approach to assess anthropogenic trace metal inputs within this watershed by combining lithology-dependent geochemical background values, metal/metalloid concentrations in stream sediments and mass balances of element fluxes at four key sites. The strongest anthropogenic contributions to particulate element fluxes are 90-95% for Cd, Zn and Hg in downstream sub-catchments. The localisation of anthropogenic metal/metalloid sources in restricted areas offers a great opportunity to further significantly reduce metal emissions and restore the Lot-Garonne-Gironde fluvial-estuarine ecosystem.