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Papers by Gerard Blanc

XIèmes Journées, Les Sables d'Olonne, 2010

Alliance for Global Sustainability Bookseries, 2011

ABSTRACT Municipal wastewater (WW) discharges induce various environmental impacts on receiving f... more ABSTRACT Municipal wastewater (WW) discharges induce various environmental impacts on receiving freshwater systems e.g. contribution to metal pollution. Besides the quantity of metal release, metal speciation and possible transformation processes present danger to aquatic biota. In experimental mixtures of WW effluents with receiving waters, discharged dissolved trace metals showed different forms of behavior. Cobalt showed adsorption onto particles, while Cu showed desorption from particulate into dissolved state. In presence of high amounts of river particles, interactions with WW contaminants were elevated.

Applied Geochemistry, 2005

Results are presented from observation of dissolved metal concentrations and fluxes at 5 sites in... more Results are presented from observation of dissolved metal concentrations and fluxes at 5 sites in the Lot–Garonne fluvial system known for its historic metal contamination. The contamination originates from the upstream Lot River where a small tributary (Riou-Mort River) drains a smelting-waste area. Unlike non-neutralised acid mine drainage systems, the Riou-Mort waters were not acidic (6.8 < pH < 8.0) due to application of alkaline reagents for neutralisation. Relatively high dissolved U concentrations (up to 1.1 μg L−1) were attributed to these reagents. High metal concentrations (e.g., up to 23 and 1190 μg L−1, for Cd and Zn, respectively) in the Riou-Mort water resulted from the oxidation of the sulphide phases within the smelting-wastes. Pyrite oxidation rate was estimated (5530 t a−1; 35.7 t km−2 a−1) from the total amount of SO42- discharged in the river water. The related dissolved metal inputs into the Lot River were, e.g., 0.55 and 35 t a−1 for Cd and Zn, respectively. The dissolved Cd fluxes in the Lot River corresponded to 65% of those in the downstream Garonne River. The dissolved Zn fluxes were even similar to those in the Garonne River. Mass balance calculations showed that, downstream the Riou-Mort/Lot River confluence, the exchange between dissolved and particulate phases accounted for the removal of 15% of Zn and 50% of Cd from the dissolved phase. The calculated annual dissolved metal fluxes at the outlet of the Lot–Garonne River system are significant at the global scale, as they represent 0.02–0.25% of the global river budget.

Science of The Total Environment, 2006

The partitioning of particulate trace metals was investigated during one year of monthly sampling... more The partitioning of particulate trace metals was investigated during one year of monthly sampling of suspended particulate matter (SPM) at eight sites along the Lot–Garonne fluvial system, known for its polymetallic pollution. The chemical partitioning in five operationally defined fractions (exchangeable/carbonate, Fe/Mn oxides, organic matter/sulfides, acid soluble, residual) was determined using a multiple single extraction approach. This approach showed that Cd, Zn, Pb and Cu were mainly associated with acid soluble phases (84–95%, 65–88%, 61–82% and 55–80% of the respective total metal content), and therefore showed a high mean potential of mobilization and bioavailability. In the Riou-Mort River, draining the smelting-wastes, Zn, Cd and Mn showed high mobility as they were little associated with the residual fraction (1–2%) and mainly bound to the ‘exchangeable’ fraction of SPM (60–80%), probably weakly adsorbed on amorphous freshly-precipitated sulfide and/or oxide phases. Upstream and downstream of the anthropogenic source of metallic pollution, Mn and Cd, and Zn to a lesser extent, remained highly reactive. The other trace metals were mainly associated with the residual fraction and thus less mobile. However, the multiple single extraction scheme revealed that the most reactive transport phases were non-selectively extracted by the conventional extractants used here. These selectivity problems could not have been observed if sequential extraction was used.

Journal of Neurochemistry, 1990

Abstract: The contribution of dopamine (DA) afferents to the regulation of β-adrenergic receptor ... more Abstract: The contribution of dopamine (DA) afferents to the regulation of β-adrenergic receptor sensitivity (isoproterenol-stimulated adenylate cyclase activity) in the rat prefrontal cortex was investigated by comparing the effects of lesions affecting either both DA and noradrenaline (NA) or NA fibers alone. Bilateral 6-hydroxydopamine (6-OHDA) lesions made in the ventral tegmental area destroyed ascending DA and to a variable extent ascending NA fibers innervating the prefrontal cortex. Two opposite effects were observed depending on the extent of cortical NA denervation: (a) When NA denervation was complete (<4% of controls), a marked increase in the isoproterenol-sensitive adenylate cyclase activity (+78%) was found. The amplitude of this denervation supersensitivity was similar to that occurring following complete and selective destruction of NA innervation induced by bilateral 6-OHDA injections made into the pedunculus cerebellaris superior. (b) When 6-OHDA injections into the ventral tegmental area led to a partial destruction of cortical NA afferents (10–40% of control values), a hyposensitivity of the isoproterenol-induced adenylate cyclase activity (–30%) was observed. This effect contrasted with the moderate supersensitivity seen in rats with partial, but selective, destruction of NA innervation (pedunculus cerebellaris superior lesions). The hyposensitivity of β-adrenergic receptors obtained in rats with partial lesions of cortical NA fibers, but devoid of cortical DA innervation, suggests that DA neurons may regulate, under certain conditions, the denervation supersensitivity of β-adrenergic receptors.

Applied Geochemistry, 2007

High-resolution sampling (every 3 h) of SPM was performed during a major flood event in a heterog... more High-resolution sampling (every 3 h) of SPM was performed during a major flood event in a heterogeneous, medium scale watershed of the Garonne-Gironde fluvial-estuarine system (the Lot River; A = 10,700 km2; Q = 151 m3/s). Particulate metal and metalloid (Cd, Zn, Pb, Co, Cr, Ni, Mo, V, U, As, Sb, Th) concentrations were compared with monthly data of the same site (Temple site) obtained during 1999–2002. During the flood event, suspended particulate matter (SPM) concentrations closely followed river discharge with a maximum value (1530 mg/L) coinciding with the discharge peak (2970 m3/s). Trace metal/metalloid concentrations showed significant temporal variations and very contrasted responses. Particulate concentrations were similar to baseline values at the beginning of the flood and mostly increased during the event, showing anticlockwise and complex shape hystereses. Comparison of SPM yield (440,000 t) and particulate metal/metalloid fluxes during the flood with annual fluxes (1999–2002) highlights the great importance of major flood events in fluvial transport. Adequate sampling frequency during floods is necessary for reliable annual flux estimates and provides geochemical signals that may greatly improve our understanding of fluvial transport processes. The scenario of SPM and metal and metalloid transport during the flood are reconstructed by combining variations of Zn, Cd and Sb concentrations, concentration ratios (e.g. Zn/Cd, As/Th, Cd/Th) and hysteresis loops. Changes in SPM and metal/metalloid transport during distinct key stages of the flood were attributed to successive dominance of different water masses transporting material from different sources (e.g. industrial point source, bed sediment from reservoirs, plain erosion). Flood management (dam flushing) clearly enhanced the remobilization of up to 30-a old polluted sediment from reservoir lakes. Sediment remobilization accounted for ∼185,000 t of SPM (i.e. 42% of the total SPM fluxes during the flood) and strongly contributed to particulate metal/metalloid transport for Cd (90%), Zn (83%) and Pb (61%). Therefore, flood management needs to be taken into consideration in future models for erosion and pollutant transport.

Applied Geochemistry, 2007

Contaminated fluvial sediments represent both temporary sinks for river-borne pollutants and pote... more Contaminated fluvial sediments represent both temporary sinks for river-borne pollutants and potential sources in case of natural and/or anthropogenic resuspension. Reservoir lakes play a very important role in sediment dynamics of watersheds and may offer great opportunities to study historical records of river-borne particles and associated elements transported in the past. The fate and potential environmental impact of Hg depends on its abundance, its carrier phases and its chemical speciation. Historical Hg records and solid state Hg speciation were compared in sediments from two contrasting reservoirs of the Lot River (France) upstream and downstream from a major polymetallic pollution (e.g. Cd, Zn) source. Natural (geochemical background) and anthropogenic Hg concentrations and their relationships with predominant carrier phases were determined. The results reveal important historical Hg contamination (up to 35 mg kg−1) of the downstream sediment, reflecting the historical evolution of industrial activity at the point source, i.e. former coal mining, Zn ore treatment and post-industrial remediation work. Single chemical extractions (ascorbate, H2O2, KOH) suggest that at both sites most (∼75%) of the Hg is bound to organic and/or reactive sulphide phases. Organo-chelated (KOH-extracted) Hg, representing an important fraction in the uncontaminated sediment, shows similar concentrations (∼0.02 mg kg−1) at both sites and may be mainly attributed to natural inputs and/or processes. Although, total Hg concentrations in recent surface sediments at both sites are still very different, similar mono-methylmercury concentrations (up to 4 μg kg−1) and vertical distributions were observed, suggesting comparable methylation-demethylation processes. High mono-methylmercury concentrations (4–15 μg kg−1) in 10–40 a-old, sulphide-rich, contaminated sediment suggest long-term persistence of mono-methylmercury. Beyond historical records of total concentrations, the studied reservoir sediments provided new insights in solid state speciation and carrier phases of natural and anthropogenic Hg. In case of sediment resuspension, the major part of the Hg historically stored in the Lot River sediments will be accessible to biogeochemical recycling in the downstream fluvial-estuarine environment.

Earth and Planetary Science Letters, 1996

The Atlantis II Deep is located on the Red Sea axial rift. It is a topographic depression enclosi... more The Atlantis II Deep is located on the Red Sea axial rift. It is a topographic depression enclosing a volume of about 17 km3 between 1,900 m and 2,200 m depth that contains layered brines of temperatures up to 66°C and salinities up to 270‰. Previous geochemical investigations showed that the hot brines result from discharge of hydrothermal solutions that have exchanged heat and chemical components with the basaltic substratum. The last investigation of the Deep in 1992 showed that the brines occurred in four well mixed layers with the shallowest at a depth of 2,000 m. The temperature and salinity profiles describe a transition zone from 2,000 m to 1,900 m, above which Red Sea water occurs. The distribution of temperature and salt in this transition zone appears to be controlled by the topography of the Deep. The hydrographic structure of the brine column has been documented in the literature for seven time intervals between 1966 and 1992. Examination of these data shows that the system changed with time. The evolution of the entire package of brines that fill the Deep shows the following changes: (1) the temperature of the brines increased; (2) the salinity of the solutions increased; (3) the two brine layers described in 1966 still existed in 1992, but new layers appeared above them; (4) for 26 years, almost all additional heat and salt supplied in the Deep were confined to the depression and were not dispersed into the overlying seawater. The fourth point indicates that a heat and salt balance for the Deep can be calculated. The calculation of the heat that entered into the system was divided into two components: the temperature increase of the brines and the heat loss at the wall-rock; the latter component was negligible. The rate of heat input to the Deep was constant during the period considered, and amounted to 0.54 × 109 W. The salt input was also constant, and equalled 250–350 kg/s. During the period 1966–1992, heat and salt were most probably supplied by a hydrothermal solution with an average range of flow rate, temperature, and salinity of 670–1000 kg/s, 195–310°C, and 270–370‰, respectively.

Neuroscience, 2001

AbstractÐWe have previously shown that a large part of the d-amphetamine-induced release of dopam... more AbstractÐWe have previously shown that a large part of the d-amphetamine-induced release of dopamine in the nucleus accumbens is not associated with an increase in locomotor activity, and that ªfunctionalº dopamine release (i.e. release of dopamine associated with locomotor activity) requires the distal facilitation of noradrenergic transmission through a1adrenergic receptors in the prefrontal cortex. To determine the role of monosynaptic or polysynaptic projections from the prefrontal cortex to the nucleus accumbens in these amphetamine responses, either AMPA/kainate (6-cyano-7-nitroquinoxaline-2,3-dione, CNQX, 300 mM), N-methyl-d-aspartate (d(2)-2-amino-5-phosphono-pentanoic acid, APV, 500 mM) or metabotropic [(1)-a-methyl-4-carboxy-phenylglycine, MCPG, 10 mM] glutamate receptor antagonists were infused through a dialysis probe in the rat nucleus accumbens. CNQX and MCPG but not APV reduced the ªnon-functionalº release of dopamine evoked by local (3 mM) and systemic d-amphetamine (2 mg/kg i.p.) treatments. However, the locomotor hyperactivity and functional dopamine release induced by systemic d-amphetamine were abolished by MCPG, but neither by CNQX nor by APV. MCPG treatment also abolished the hyperlocomotor activity and functional dopamine release evoked by bilateral morphine injection into the ventral tegmental area. The dopamine release evoked by this morphine treatment was 16-fold lower than that induced by the systemic d-amphetamine injection, although similar behavioral activations were observed.

Science of The Total Environment, 2005

A 15-month experiment combining a geochemical survey of Cd, Cu, Zn and Hg with a bioaccumulation ... more A 15-month experiment combining a geochemical survey of Cd, Cu, Zn and Hg with a bioaccumulation study for three filter-feeding bivalve species (oysters, Crassostrea gigas; cockles, Cerastoderma edule; and clams, Ruditapes philippinarum) was conducted in a breeding basin of the Nord Médoc salt marshes connected to the Gironde estuary, which is affected by historic polymetallic pollution. Regular manual surface measurements of temperature, salinity, pH and dissolved O2 concentration and hourly multiprobe in situ measurements throughout several periods for 6–8 weeks were performed. The geochemical behavior of metals in water, suspended particulate matter and sediment and their ecotoxicological impact on the three bivalve species were evaluated by in situ exposure of juvenile oysters (water column) and adult cockles and clams (sediment surface).The physico-chemical parameters reflected seasonal variations and basin management. A distinct daily periodicity (except salinity) indicated intense photosynthesis and respiration. In summer, low dissolved O2 saturations (∼40–50%) occurred in the early morning at 30 cm above the sediment, whereas in depressions, the water column near the sediment surface was suboxic. Cadmium, Zn and Cu concentrations in suspended particulate matter exceeded typical estuarine values and were much higher than the homogeneously distributed concentrations in different depth ranges of the basin sediment. Particles collected in sediment traps showed intermediate metal concentrations close to sediment values. These results suggest trace metal recycling due to reductive dissolution under suboxic conditions at the sediment surface resulting in trace metal release to the water column and adsorption onto suspended particles. Dissolved Cd, Zn and Hg concentrations (e.g. 13–136 ng l−1; 0.3–25.1 μg l−1 and 0.5–2.0 ng l−1, respectively) in the basin corresponded to the concentration range typically observed in the Gironde estuary, except for some maximum values attributed to metal recycling. In contrast, dissolved Cu concentrations (1.08–6.08 μg l−1) were mostly higher than typical estuarine values, probably due to recycled Cu complexation by dissolved organic matter. Growth, bioaccumulation rates and kinetics in the whole soft body of the bivalves were analyzed every 40 days. Although Cd bioaccumulation of oysters was lower in the basin than in the estuary during the same period (27,000 ng g−1, dry weight and 40,000 ng g−1, respectively) these values are largely above the new human consumption safety level (5000 ng g−1, dw; European Community, 2002). For cockles and clams, Cd bioaccumulation was lower, reaching 1400 ng g−1 and 950 ng g−1, respectively. Similar results were obtained for Zn and Cu suggesting physiological differences between the species and/or differences in the exposure of the organisms due to physico-chemical conditions and metal distribution between dissolved and particulate phases. In contrast, Hg bioaccumulation was highest for cockles reaching bioconcentration factors of ∼200,000, which even exceeded that of Cd in oysters (50,000) for the same exposition period. Nevertheless, Hg concentrations remained relatively low in the three bivalve species.

Science of The Total Environment, 2004

The present paper is based on discharges and suspended particulate matter concentrations from a 9... more The present paper is based on discharges and suspended particulate matter concentrations from a 9-years high-resolution database for the Garonne River (large plain river) covering contrasted hydrologic years, and a 12-months high frequency sampling for the Nivelle River (small mountainous river). Annual SPM fluxes in the Garonne River range from 0.6×106 t year−1 (1997) to 3.9×106 t year−1 (1996). In contrast, the Nivelle River transported 11×103 t year−1 from December 1995 to December 1996. From the long-term observation of the Garonne River an empirical relation between SPM* (discharge-weighted mean annual SPM concentrations) and annual discharge was established. This relation allows estimating annual SPM fluxes for the Garonne River with less than 30% deviation from reference values for the whole range of mean annual discharge observed during the past decade. Specific (=area-normalized) annual SPM fluxes (YSPM) range from 11 to 74 t km−2 year−1 for the Garonne River. Comparison of these results with YSPM of the Nivelle River (69 t km−2 year−1 in 1996) suggests that interannual hydrological variations may have a greater impact on fluvial SPM transport than basin-specific parameters. By extracting individual SPM concentrations and corresponding discharge values from the database, different sampling frequencies were simulated and resulting SPM fluxes were then compared to reference fluxes derived from the complete database. If a deviation of simulated flux estimates from reference fluxes lower than ±20% is accepted, the Garonne River (large plain river) must be sampled at least every 3 days (10 samples per month) and the Nivelle River every 7 h (approx. 100 samples per month). For the Garonne River this minimum sampling frequency is valid for all contrasted hydrologic years of the observation period. Below these minimum sampling frequencies, annual SPM flux estimates may greatly differ from reference fluxes (up to 200%) and there is high probability of systematic underestimation. Consequently, annual SPM flux estimates for the Garonne River derived from the empirical relation (SPM*-annual discharge) are likely to be more satisfactory (errors <30%) than estimates based on sampling frequencies lower than the minimum frequency. These findings underline the need of adapted sampling strategies for erosion assessment, reliable chemical (e.g. nutrients and pollutants) mass balances and characterisation of fluvial transport mechanisms in the world's contrasted watersheds.

Science of The Total Environment, 2004

Fluvial cadmium (Cd) inputs into the Gironde estuary via the Lot–Garonne River system were evalua... more Fluvial cadmium (Cd) inputs into the Gironde estuary via the Lot–Garonne River system were evaluated using nine years of daily measurements of water discharge and total suspended sediment content (TSS) combined with monthly analyses of dissolved and particulate Cd concentrations. This study demonstrates that dissolved and particulate Cd concentrations in the Lot River have strongly decreased in the early 1990s. However, dissolved and particulate Cd concentrations in the Lot River are still higher than those in the Garonne River. In 1992–1998 mean annual Cd concentrations are more or less constant and thus, annual Cd fluxes mainly depend on hydrology. Daily total Cd fluxes range from 0.26 to 966 kg day−1 in the Lot River and from 0.31 to 1360 kg day−1 in the Garonne River, downstream their confluence. During dry years, Cd fluxes at La Réole are dominated by inputs from the upstream Garonne River, whereas during wet years they are controlled by inputs from the polluted Lot River watershed. The relation between particulate and dissolved Cd fluxes depends on TSS concentrations, which appear to be mainly controlled by the succession of floods and low waters reflecting short-term basin-scale climate variability. Cadmium concentrations, fluxes and the ratio between the particulate and dissolved Cd fluxes depends on the absolute value and instantaneous evolution (strong relative increase or decrease) of discharge. An empiric model permits deducing intervals of daily dissolved Cd fluxes from discharge, hydrological key situation and related intervals of ‘typical’ dissolved Cd concentrations. In 1992–1998 the Lot–Garonne River system shows close relations between annual dissolved and particulate Cd fluxes. These relations allow deducing annual particulate Cd fluxes using annual dissolved Cd fluxes obtained from the model. The validation a posteriori shows that our empiric model accurately reproduces the annual Cd fluxes estimated from the field data with uncertainty lower than 25% for dissolved fluxes and lower than 30% for the particulate fluxes. Consequently, the empiric model permits estimating annual dissolved and particulate Cd fluxes in the Lot–Garonne River system, from daily discharge data, without Cd analysis. Cadmium fluxes obtained from the model may be used as approximate values for gross fluvial Cd inputs into the Gironde estuary.

Marine Chemistry, 2002

In order to understand the relationship between authigenic precipitation of U, Mo, Cd, and the re... more In order to understand the relationship between authigenic precipitation of U, Mo, Cd, and the redox properties of the marine environment, we have studied the vertical distribution of these metals and of the major redox species (oxygen, nitrate, manganese, reactive iron, sulfate, carbon, and sulfur) in modern sediment. We have sampled four sites at 150 to 2800 m depth in the Bay of Biscay. At the shallowest station, where sediment is highly bioturbated, organic carbon levels are above 2% and particulate sulfides are abundant. At the deepest stations, sediment is much less bioturbated, and organic carbon levels are lower. At all sites, early diagenesis follows a well-established depth sequence of redox reactions, based on the bacterially mediated oxidation of organic matter. Manganese-oxides and authigenic U and Mo were extracted by an ascorbate solution. Molybdenum is associated with these oxides in the oxic part of cores. In the anoxic layer of the sediment, Mo precipitates as a detectable authigenic phase only when sulfide minerals are present, i.e. when sulfate reduction becomes important. In anoxic sediments, Cd enrichment is a good indicator of sulfide production from sulfate reduction even if the production is weak. Uranium precipitates at the depth of reactive iron (III) reduction. No relationship was observed between U and S. The U concentration at the depth of precipitation agrees with values calculated using estimated accumulation rates and a downward diffusive flux of dissolved U from the bottom seawater into the sediment. However, authigenic U concentrations continue to increase in the anoxic part of the cores. Therefore, it is difficult to establish a direct relationship between the process of U accumulation and the flux of Corg to the sediment.

Pharmacology Biochemistry and Behavior, 2003

Drugs of abuse, such as d-amphetamine or nicotine, are generally considered as acting through an ... more Drugs of abuse, such as d-amphetamine or nicotine, are generally considered as acting through an increased release of dopamine in a subcortical structure, the nucleus accumbens, thus inducing locomotor hyperactivity in rats. Following repeated treatments, the same drugs induce a progressive increase in locomotor response called behavioral sensitization. This process has been suggested to play a role in the acquisition and maintenance of addictive behaviors. Here we show that whereas behavioral sensitization to d-amphetamine (0.5 and 0.75 mg/kg) stays constant following three consecutive periods of withdrawal (15, 30 and 30 days), the same experimental conditions completely abolish behavioral sensitization to 0.3 and 0.5 mg/kg nicotine. Indeed, following these periods of withdrawal, locomotor responses to nicotine are identical to those obtained at the first nicotine injection or after repeated saline injections.However, when a monoamine oxidases inhibitor (MAOI), tranylcypromine (3 mg/kg) or pargyline (30 mg/kg), is co-injected with nicotine, behavioral sensitization is maintained despite submission of the animals to the same withdrawal experimental design. Since tobacco smoke is known to contain many compounds including MAOIs, our data suggest that addictive properties of tobacco may not be limited to nicotine. We propose that MAOIs potentiate effects of nicotine on monoamines release.

Science of The Total Environment, 2006

Daily measurements of water discharges and suspended particulate matter (SPM) concentrations and ... more Daily measurements of water discharges and suspended particulate matter (SPM) concentrations and monthly sampling for trace element analyses (Cd, Zn, Pb and Cu) were conducted from 1999 to 2002 on the Garonne, Dordogne and Isle Rivers, the three main tributaries of the Gironde Estuary, France. Dissolved and particulate Cd, Zn, Pb and Cu concentrations in the Isle River were generally higher than those in the Garonne River, despite the known historical polymetallic pollution affecting the Lot–Garonne River system. Even if the relatively high dissolved metal concentrations in the Isle River may be of importance for the local ecosystem, metal inputs into the estuarine and coastal zones are mainly controlled by fluvial transport via the Garonne River. Characteristic element concentration ratios (e.g., Zn/Pb) in SPM and stream sediments from the Dordogne and Isle Rivers suggest two different metal source areas with distinct geochemical signals. Low Zn/Pb ratios (< 8) and low Cu/Pb ratios (< 0.8) have been attributed to upstream source zones in the Massif Central, featuring various ore deposits and mining areas. High Zn/Pb ratios were assigned to downstream sources (e.g., vineyards), partly explaining high Zn and Cu concentrations and high Cu/Pb ratios (> 0.8) in SPM. Although SPM derived from the upstream parts of the studied watersheds may greatly contribute to the observed fluvial metal transport (up to ∼ 80% for Pb), the results suggest that intensive agriculture also considerably influences gross metal (e.g., Zn, Cu) fluxes into the Gironde Estuary. Relative contributions of upstream and downstream source zones may vary from one year to another reflecting hydrological variations and/or reservoir management. Monitoring fluxes and identifying distinct geochemical signals from source areas in heterogeneous watersheds may greatly improve understanding of contaminant transport to the coast.

Hydroécologie Appliquée, 2006

La détermination précise des flux de Cd dissous et particulaire du Lot et de la Garonne impose la... more La détermination précise des flux de Cd dissous et particulaire du Lot et de la Garonne impose la mise en place d'une stratégie d'échantillonnage spécifique. La fiabilité des méthodologies que nous employons a été vérifiée. Nous avons notamment montré que l'échantillonnage des MES par centrifugation de grands volumes d'eau (1000 L) est la méthode la plus adaptée pour calculer des flux, mais aussi pour accéder à la spéciation à l'état solide. Des mesures journalières de débits et de concentrations en MES combinées à des analyses de Cd dissous et particulaire permettent de proposer un bilan de masse de Cd pour le système fluviatile du Lot et de la Garonne. Ce bilan montre que 70-80 % du Cd transporté en aval par la Garonne (La Réole) provient du Lot dont la majorité (∼75 %) provient du bassin de Decazeville via la rivière Riou-Mort. Ce bilan montre également que les sédiments pollués en Cd et accumulés derrière les barrages hydroélectriques constituent une source secondaire en Cd dont la mobilisation dépend des variations hydrologiques, mais aussi des aménagements anthropiques. En considérant l'ensemble des apports fluviaux en Cd, nous estimons que 60-75 % du Cd apporté à l'estuaire de la Gironde est d'origine anthropique. Sur la base des données existantes, validées entre 1994 et 2000, les flux journaliers de Cd dissous ont été recalculés pour le Lot, et des relations caractéristiques entre flux de matières et débits ont été établies. Ainsi nous proposons un modèle prédictif empirique permettant une bonne estimation des flux de Cd dissous et particulaire à partir des seules données de débit. La comparaison de nos données de flux bruts avec les quelques données disponibles de flux nets (e.g. apports à l'océan) de Cd dissous suggère que plus de 50 % du Cd particulaire passent sous forme dissoute pendant les années humides (94 et 96) et que les flux de Cd dissous nets sont supérieurs aux flux totaux bruts pendant les années sèches (91 et 97). Ceci suggère que la réactivité estuarienne girondine libère progressivement sous forme dissoute, la quasi totalité du Cd apporté majoritairement sous forme particulaire par le fleuve. Abstract -In the Lot and Garonne Rivers, the precise determination of the dissolved and particulate Cd fluxes lead us to develop a specific sampling strategy with adapted sampling Article published by EDF and available at http://www.hydroecologie.org or http://dx.doi.org/10.1051/hydro:2006005 20 G. Blanc et al.

Marine Chemistry, 2004

Vertical profiles of heavy metals (Cd, Cu, Cr, Fe, Mn, Ni and Pb) in the particulate and dissolve... more Vertical profiles of heavy metals (Cd, Cu, Cr, Fe, Mn, Ni and Pb) in the particulate and dissolved phases and redox sensitive parameters (dissolved oxygen, nitrate, nitrite and ammonium) were analyzed for the first time in the continuum Maximum Turbidity Zone (MTZ) -Fluid Mud (FM; 50 g l À 1 < suspended particulate matter (SPM) < 500 g l À 1 )-consolidated sediment of a macrotidal, highly turbid estuary: the Gironde. The results show that the fluid mud is a layer of intense metal mobilization due to redox induced dissolution, releasing trace metals into the water column. This newly identified phenomenon creates a transient situation characterized by the onset of diagenetic sequences in the FM, i.e. in the lower part of the water column. These sequences overlie permanent diagenetic sequences in the consolidated sediment, similar to those typically observed in marine and estuarine sediments. The discontinuity of dissolved Cd, Ni and Pb concentrations at the sediment surface indicates that Mn reduction is faster in the FM than in the upper sediment, isolated from the oxic water column by the suboxic FM. Two separate diagenetic signals are preserved, as the installation of the diagenetic sequence in the FM is faster than the molecular diffusion of dissolved compounds through the FM -sediment interface. The diagenetic signal of trace metals (e.g. dissolved Cr maximum) in the upper sediment layer near the FM -sediment interface is interpreted as a transient record of past hydrologic situations, during which the absence of the FM layer permitted the installation of an oxic/suboxic front in the upper sediment. The resuspension of the FM during the spring tide probably results in a new distribution of these elements in the estuary, where they may be stabilized in the dissolved phase (e.g. by chloride complexes or dissolved organic compounds) or be adsorbed onto reactive particles (e.g. freshly precipitated Mn oxyhydroxides). (S. Robert).

Applied Geochemistry, 2004

Heavy metal (Zn, Cd, Cu and Pb) mass balances in the Lot-Garonne fluvial system have been establi... more Heavy metal (Zn, Cd, Cu and Pb) mass balances in the Lot-Garonne fluvial system have been established for 1999 and 2000. The mean annual discharges of these years are close to the mean discharge of the previous decade. The estimated annual dissolved and particulate fluxes in this model watershed integrate daily input from diffuse and point sources, diffusive fluxes at the water/sediment interface, changes in the dissolved-particulate partition and changes in sediment stock. Cadmium, Zn, Cu and Pb entering the Gironde estuary via the Garonne River (11–14 t a−1 of Cd; 1330–1450 t a−1 of Zn; 126–214 t a−1 of Cu and 127–155 t a−1 of Pb) are mainly transported in the particulate phase and the major part (i.e. ∼74 to 96% for Cd, ∼60% for Zn, ∼50 to 60% for Cu and ∼80% for Pb) is transported by the Lot River. The main anthropogenic heavy metal point source is located in a small upstream watershed (Riou-Mort River) accounting for at least 47% (Cd), ∼20% (Zn), ∼4% (Cu) and ∼7 to 9% (Pb) of the total heavy metal inputs into the Garonne River, although it contributes only 1% of the discharge. Mass balances for 1999 suggest that under mean annual hydrologic conditions on the basin scale, the heavy metal budget of the Lot-Garonne fluvial system is balanced and that the stocks of Cd [200 t; Environ. Tech. 16 (1995) 1145] and Zn in the Lot River sediment are constant under mean discharge conditions. Heavy metal input by molecular diffusion at the sediment surface represents an important component of dissolved metal inputs into the system (e.g. 30% for Cu). Except for Cu, these dissolved inputs are totally removed from solution by SPM. Based on the generally constant Zn/Cd (∼50) concentration ratio in sediment cores from the polluted Lot River reaches and the sediment stock of Cd [200 t; Environ. Tech. 16 (1995) 1145], the present day Zn stock in the Lot River sediments has been estimated at about 10,000 t. In addition to the mobilization of river-bed sediment and associated heavy metals by intense floods, local human activities, including river-bed dredging, may strongly modify the heavy metal budget of the river system. In 2000, the dredging-related remobilization of polluted Lot River sediment released 2–6 t Cd. This additional Cd point source was estimated to account for 15–43% of the gross inputs into the Gironde Estuary.

Drugs of abuse, such as psychostimulants and opiates, are generally considered as exerting their ... more Drugs of abuse, such as psychostimulants and opiates, are generally considered as exerting their locomotor and rewarding effects through an increased dopaminergic transmission in the nucleus accumbens. Noradrenergic transmission may also be implicated because most psychostimulants increase norepinephrine (NE) release, and numerous studies have indicated interactions between noradrenergic and dopaminergic neurons through ␣1-adrenergic receptors. However, analysis of the effects of psychostimulants after either destruction of noradrenergic neurons or pharmacological blockade of ␣1-adrenergic receptors led to conflicting results. Here we show that the locomotor hyperactivities induced by D-amphetamine (1-3 mg/kg), cocaine (5-20 mg/kg), or morphine (5-10 mg/kg) in mice lacking the ␣1b subtype of adrenergic receptors were dramatically decreased when compared with wild-type littermates. Moreover, behavioral sensitizations induced by D-amphetamine (1-2 mg/kg), cocaine (5-15 mg/kg), or morphine (7.5 mg/kg) were also decreased in knock-out mice when compared with wild-type. Ruling out a neurological deficit in knock-out mice, both strains reacted similarly to novelty, to intraperitoneal saline, or to the administration of scopolamine (1 mg/ kg), an anti-muscarinic agent. Finally, rewarding properties could not be observed in knock-out mice in an oral preference test (cocaine and morphine) and conditioned place preference (morphine) paradigm.

XIèmes Journées, Les Sables d'Olonne, 2010

Alliance for Global Sustainability Bookseries, 2011

ABSTRACT Municipal wastewater (WW) discharges induce various environmental impacts on receiving f... more ABSTRACT Municipal wastewater (WW) discharges induce various environmental impacts on receiving freshwater systems e.g. contribution to metal pollution. Besides the quantity of metal release, metal speciation and possible transformation processes present danger to aquatic biota. In experimental mixtures of WW effluents with receiving waters, discharged dissolved trace metals showed different forms of behavior. Cobalt showed adsorption onto particles, while Cu showed desorption from particulate into dissolved state. In presence of high amounts of river particles, interactions with WW contaminants were elevated.

Applied Geochemistry, 2005

Results are presented from observation of dissolved metal concentrations and fluxes at 5 sites in... more Results are presented from observation of dissolved metal concentrations and fluxes at 5 sites in the Lot–Garonne fluvial system known for its historic metal contamination. The contamination originates from the upstream Lot River where a small tributary (Riou-Mort River) drains a smelting-waste area. Unlike non-neutralised acid mine drainage systems, the Riou-Mort waters were not acidic (6.8 < pH < 8.0) due to application of alkaline reagents for neutralisation. Relatively high dissolved U concentrations (up to 1.1 μg L−1) were attributed to these reagents. High metal concentrations (e.g., up to 23 and 1190 μg L−1, for Cd and Zn, respectively) in the Riou-Mort water resulted from the oxidation of the sulphide phases within the smelting-wastes. Pyrite oxidation rate was estimated (5530 t a−1; 35.7 t km−2 a−1) from the total amount of SO42- discharged in the river water. The related dissolved metal inputs into the Lot River were, e.g., 0.55 and 35 t a−1 for Cd and Zn, respectively. The dissolved Cd fluxes in the Lot River corresponded to 65% of those in the downstream Garonne River. The dissolved Zn fluxes were even similar to those in the Garonne River. Mass balance calculations showed that, downstream the Riou-Mort/Lot River confluence, the exchange between dissolved and particulate phases accounted for the removal of 15% of Zn and 50% of Cd from the dissolved phase. The calculated annual dissolved metal fluxes at the outlet of the Lot–Garonne River system are significant at the global scale, as they represent 0.02–0.25% of the global river budget.

Science of The Total Environment, 2006

The partitioning of particulate trace metals was investigated during one year of monthly sampling... more The partitioning of particulate trace metals was investigated during one year of monthly sampling of suspended particulate matter (SPM) at eight sites along the Lot–Garonne fluvial system, known for its polymetallic pollution. The chemical partitioning in five operationally defined fractions (exchangeable/carbonate, Fe/Mn oxides, organic matter/sulfides, acid soluble, residual) was determined using a multiple single extraction approach. This approach showed that Cd, Zn, Pb and Cu were mainly associated with acid soluble phases (84–95%, 65–88%, 61–82% and 55–80% of the respective total metal content), and therefore showed a high mean potential of mobilization and bioavailability. In the Riou-Mort River, draining the smelting-wastes, Zn, Cd and Mn showed high mobility as they were little associated with the residual fraction (1–2%) and mainly bound to the ‘exchangeable’ fraction of SPM (60–80%), probably weakly adsorbed on amorphous freshly-precipitated sulfide and/or oxide phases. Upstream and downstream of the anthropogenic source of metallic pollution, Mn and Cd, and Zn to a lesser extent, remained highly reactive. The other trace metals were mainly associated with the residual fraction and thus less mobile. However, the multiple single extraction scheme revealed that the most reactive transport phases were non-selectively extracted by the conventional extractants used here. These selectivity problems could not have been observed if sequential extraction was used.

Journal of Neurochemistry, 1990

Abstract: The contribution of dopamine (DA) afferents to the regulation of β-adrenergic receptor ... more Abstract: The contribution of dopamine (DA) afferents to the regulation of β-adrenergic receptor sensitivity (isoproterenol-stimulated adenylate cyclase activity) in the rat prefrontal cortex was investigated by comparing the effects of lesions affecting either both DA and noradrenaline (NA) or NA fibers alone. Bilateral 6-hydroxydopamine (6-OHDA) lesions made in the ventral tegmental area destroyed ascending DA and to a variable extent ascending NA fibers innervating the prefrontal cortex. Two opposite effects were observed depending on the extent of cortical NA denervation: (a) When NA denervation was complete (<4% of controls), a marked increase in the isoproterenol-sensitive adenylate cyclase activity (+78%) was found. The amplitude of this denervation supersensitivity was similar to that occurring following complete and selective destruction of NA innervation induced by bilateral 6-OHDA injections made into the pedunculus cerebellaris superior. (b) When 6-OHDA injections into the ventral tegmental area led to a partial destruction of cortical NA afferents (10–40% of control values), a hyposensitivity of the isoproterenol-induced adenylate cyclase activity (–30%) was observed. This effect contrasted with the moderate supersensitivity seen in rats with partial, but selective, destruction of NA innervation (pedunculus cerebellaris superior lesions). The hyposensitivity of β-adrenergic receptors obtained in rats with partial lesions of cortical NA fibers, but devoid of cortical DA innervation, suggests that DA neurons may regulate, under certain conditions, the denervation supersensitivity of β-adrenergic receptors.

Applied Geochemistry, 2007

High-resolution sampling (every 3 h) of SPM was performed during a major flood event in a heterog... more High-resolution sampling (every 3 h) of SPM was performed during a major flood event in a heterogeneous, medium scale watershed of the Garonne-Gironde fluvial-estuarine system (the Lot River; A = 10,700 km2; Q = 151 m3/s). Particulate metal and metalloid (Cd, Zn, Pb, Co, Cr, Ni, Mo, V, U, As, Sb, Th) concentrations were compared with monthly data of the same site (Temple site) obtained during 1999–2002. During the flood event, suspended particulate matter (SPM) concentrations closely followed river discharge with a maximum value (1530 mg/L) coinciding with the discharge peak (2970 m3/s). Trace metal/metalloid concentrations showed significant temporal variations and very contrasted responses. Particulate concentrations were similar to baseline values at the beginning of the flood and mostly increased during the event, showing anticlockwise and complex shape hystereses. Comparison of SPM yield (440,000 t) and particulate metal/metalloid fluxes during the flood with annual fluxes (1999–2002) highlights the great importance of major flood events in fluvial transport. Adequate sampling frequency during floods is necessary for reliable annual flux estimates and provides geochemical signals that may greatly improve our understanding of fluvial transport processes. The scenario of SPM and metal and metalloid transport during the flood are reconstructed by combining variations of Zn, Cd and Sb concentrations, concentration ratios (e.g. Zn/Cd, As/Th, Cd/Th) and hysteresis loops. Changes in SPM and metal/metalloid transport during distinct key stages of the flood were attributed to successive dominance of different water masses transporting material from different sources (e.g. industrial point source, bed sediment from reservoirs, plain erosion). Flood management (dam flushing) clearly enhanced the remobilization of up to 30-a old polluted sediment from reservoir lakes. Sediment remobilization accounted for ∼185,000 t of SPM (i.e. 42% of the total SPM fluxes during the flood) and strongly contributed to particulate metal/metalloid transport for Cd (90%), Zn (83%) and Pb (61%). Therefore, flood management needs to be taken into consideration in future models for erosion and pollutant transport.

Applied Geochemistry, 2007

Contaminated fluvial sediments represent both temporary sinks for river-borne pollutants and pote... more Contaminated fluvial sediments represent both temporary sinks for river-borne pollutants and potential sources in case of natural and/or anthropogenic resuspension. Reservoir lakes play a very important role in sediment dynamics of watersheds and may offer great opportunities to study historical records of river-borne particles and associated elements transported in the past. The fate and potential environmental impact of Hg depends on its abundance, its carrier phases and its chemical speciation. Historical Hg records and solid state Hg speciation were compared in sediments from two contrasting reservoirs of the Lot River (France) upstream and downstream from a major polymetallic pollution (e.g. Cd, Zn) source. Natural (geochemical background) and anthropogenic Hg concentrations and their relationships with predominant carrier phases were determined. The results reveal important historical Hg contamination (up to 35 mg kg−1) of the downstream sediment, reflecting the historical evolution of industrial activity at the point source, i.e. former coal mining, Zn ore treatment and post-industrial remediation work. Single chemical extractions (ascorbate, H2O2, KOH) suggest that at both sites most (∼75%) of the Hg is bound to organic and/or reactive sulphide phases. Organo-chelated (KOH-extracted) Hg, representing an important fraction in the uncontaminated sediment, shows similar concentrations (∼0.02 mg kg−1) at both sites and may be mainly attributed to natural inputs and/or processes. Although, total Hg concentrations in recent surface sediments at both sites are still very different, similar mono-methylmercury concentrations (up to 4 μg kg−1) and vertical distributions were observed, suggesting comparable methylation-demethylation processes. High mono-methylmercury concentrations (4–15 μg kg−1) in 10–40 a-old, sulphide-rich, contaminated sediment suggest long-term persistence of mono-methylmercury. Beyond historical records of total concentrations, the studied reservoir sediments provided new insights in solid state speciation and carrier phases of natural and anthropogenic Hg. In case of sediment resuspension, the major part of the Hg historically stored in the Lot River sediments will be accessible to biogeochemical recycling in the downstream fluvial-estuarine environment.

Earth and Planetary Science Letters, 1996

The Atlantis II Deep is located on the Red Sea axial rift. It is a topographic depression enclosi... more The Atlantis II Deep is located on the Red Sea axial rift. It is a topographic depression enclosing a volume of about 17 km3 between 1,900 m and 2,200 m depth that contains layered brines of temperatures up to 66°C and salinities up to 270‰. Previous geochemical investigations showed that the hot brines result from discharge of hydrothermal solutions that have exchanged heat and chemical components with the basaltic substratum. The last investigation of the Deep in 1992 showed that the brines occurred in four well mixed layers with the shallowest at a depth of 2,000 m. The temperature and salinity profiles describe a transition zone from 2,000 m to 1,900 m, above which Red Sea water occurs. The distribution of temperature and salt in this transition zone appears to be controlled by the topography of the Deep. The hydrographic structure of the brine column has been documented in the literature for seven time intervals between 1966 and 1992. Examination of these data shows that the system changed with time. The evolution of the entire package of brines that fill the Deep shows the following changes: (1) the temperature of the brines increased; (2) the salinity of the solutions increased; (3) the two brine layers described in 1966 still existed in 1992, but new layers appeared above them; (4) for 26 years, almost all additional heat and salt supplied in the Deep were confined to the depression and were not dispersed into the overlying seawater. The fourth point indicates that a heat and salt balance for the Deep can be calculated. The calculation of the heat that entered into the system was divided into two components: the temperature increase of the brines and the heat loss at the wall-rock; the latter component was negligible. The rate of heat input to the Deep was constant during the period considered, and amounted to 0.54 × 109 W. The salt input was also constant, and equalled 250–350 kg/s. During the period 1966–1992, heat and salt were most probably supplied by a hydrothermal solution with an average range of flow rate, temperature, and salinity of 670–1000 kg/s, 195–310°C, and 270–370‰, respectively.

Neuroscience, 2001

AbstractÐWe have previously shown that a large part of the d-amphetamine-induced release of dopam... more AbstractÐWe have previously shown that a large part of the d-amphetamine-induced release of dopamine in the nucleus accumbens is not associated with an increase in locomotor activity, and that ªfunctionalº dopamine release (i.e. release of dopamine associated with locomotor activity) requires the distal facilitation of noradrenergic transmission through a1adrenergic receptors in the prefrontal cortex. To determine the role of monosynaptic or polysynaptic projections from the prefrontal cortex to the nucleus accumbens in these amphetamine responses, either AMPA/kainate (6-cyano-7-nitroquinoxaline-2,3-dione, CNQX, 300 mM), N-methyl-d-aspartate (d(2)-2-amino-5-phosphono-pentanoic acid, APV, 500 mM) or metabotropic [(1)-a-methyl-4-carboxy-phenylglycine, MCPG, 10 mM] glutamate receptor antagonists were infused through a dialysis probe in the rat nucleus accumbens. CNQX and MCPG but not APV reduced the ªnon-functionalº release of dopamine evoked by local (3 mM) and systemic d-amphetamine (2 mg/kg i.p.) treatments. However, the locomotor hyperactivity and functional dopamine release induced by systemic d-amphetamine were abolished by MCPG, but neither by CNQX nor by APV. MCPG treatment also abolished the hyperlocomotor activity and functional dopamine release evoked by bilateral morphine injection into the ventral tegmental area. The dopamine release evoked by this morphine treatment was 16-fold lower than that induced by the systemic d-amphetamine injection, although similar behavioral activations were observed.

Science of The Total Environment, 2005

A 15-month experiment combining a geochemical survey of Cd, Cu, Zn and Hg with a bioaccumulation ... more A 15-month experiment combining a geochemical survey of Cd, Cu, Zn and Hg with a bioaccumulation study for three filter-feeding bivalve species (oysters, Crassostrea gigas; cockles, Cerastoderma edule; and clams, Ruditapes philippinarum) was conducted in a breeding basin of the Nord Médoc salt marshes connected to the Gironde estuary, which is affected by historic polymetallic pollution. Regular manual surface measurements of temperature, salinity, pH and dissolved O2 concentration and hourly multiprobe in situ measurements throughout several periods for 6–8 weeks were performed. The geochemical behavior of metals in water, suspended particulate matter and sediment and their ecotoxicological impact on the three bivalve species were evaluated by in situ exposure of juvenile oysters (water column) and adult cockles and clams (sediment surface).The physico-chemical parameters reflected seasonal variations and basin management. A distinct daily periodicity (except salinity) indicated intense photosynthesis and respiration. In summer, low dissolved O2 saturations (∼40–50%) occurred in the early morning at 30 cm above the sediment, whereas in depressions, the water column near the sediment surface was suboxic. Cadmium, Zn and Cu concentrations in suspended particulate matter exceeded typical estuarine values and were much higher than the homogeneously distributed concentrations in different depth ranges of the basin sediment. Particles collected in sediment traps showed intermediate metal concentrations close to sediment values. These results suggest trace metal recycling due to reductive dissolution under suboxic conditions at the sediment surface resulting in trace metal release to the water column and adsorption onto suspended particles. Dissolved Cd, Zn and Hg concentrations (e.g. 13–136 ng l−1; 0.3–25.1 μg l−1 and 0.5–2.0 ng l−1, respectively) in the basin corresponded to the concentration range typically observed in the Gironde estuary, except for some maximum values attributed to metal recycling. In contrast, dissolved Cu concentrations (1.08–6.08 μg l−1) were mostly higher than typical estuarine values, probably due to recycled Cu complexation by dissolved organic matter. Growth, bioaccumulation rates and kinetics in the whole soft body of the bivalves were analyzed every 40 days. Although Cd bioaccumulation of oysters was lower in the basin than in the estuary during the same period (27,000 ng g−1, dry weight and 40,000 ng g−1, respectively) these values are largely above the new human consumption safety level (5000 ng g−1, dw; European Community, 2002). For cockles and clams, Cd bioaccumulation was lower, reaching 1400 ng g−1 and 950 ng g−1, respectively. Similar results were obtained for Zn and Cu suggesting physiological differences between the species and/or differences in the exposure of the organisms due to physico-chemical conditions and metal distribution between dissolved and particulate phases. In contrast, Hg bioaccumulation was highest for cockles reaching bioconcentration factors of ∼200,000, which even exceeded that of Cd in oysters (50,000) for the same exposition period. Nevertheless, Hg concentrations remained relatively low in the three bivalve species.

Science of The Total Environment, 2004

The present paper is based on discharges and suspended particulate matter concentrations from a 9... more The present paper is based on discharges and suspended particulate matter concentrations from a 9-years high-resolution database for the Garonne River (large plain river) covering contrasted hydrologic years, and a 12-months high frequency sampling for the Nivelle River (small mountainous river). Annual SPM fluxes in the Garonne River range from 0.6×106 t year−1 (1997) to 3.9×106 t year−1 (1996). In contrast, the Nivelle River transported 11×103 t year−1 from December 1995 to December 1996. From the long-term observation of the Garonne River an empirical relation between SPM* (discharge-weighted mean annual SPM concentrations) and annual discharge was established. This relation allows estimating annual SPM fluxes for the Garonne River with less than 30% deviation from reference values for the whole range of mean annual discharge observed during the past decade. Specific (=area-normalized) annual SPM fluxes (YSPM) range from 11 to 74 t km−2 year−1 for the Garonne River. Comparison of these results with YSPM of the Nivelle River (69 t km−2 year−1 in 1996) suggests that interannual hydrological variations may have a greater impact on fluvial SPM transport than basin-specific parameters. By extracting individual SPM concentrations and corresponding discharge values from the database, different sampling frequencies were simulated and resulting SPM fluxes were then compared to reference fluxes derived from the complete database. If a deviation of simulated flux estimates from reference fluxes lower than ±20% is accepted, the Garonne River (large plain river) must be sampled at least every 3 days (10 samples per month) and the Nivelle River every 7 h (approx. 100 samples per month). For the Garonne River this minimum sampling frequency is valid for all contrasted hydrologic years of the observation period. Below these minimum sampling frequencies, annual SPM flux estimates may greatly differ from reference fluxes (up to 200%) and there is high probability of systematic underestimation. Consequently, annual SPM flux estimates for the Garonne River derived from the empirical relation (SPM*-annual discharge) are likely to be more satisfactory (errors <30%) than estimates based on sampling frequencies lower than the minimum frequency. These findings underline the need of adapted sampling strategies for erosion assessment, reliable chemical (e.g. nutrients and pollutants) mass balances and characterisation of fluvial transport mechanisms in the world's contrasted watersheds.

Science of The Total Environment, 2004

Fluvial cadmium (Cd) inputs into the Gironde estuary via the Lot–Garonne River system were evalua... more Fluvial cadmium (Cd) inputs into the Gironde estuary via the Lot–Garonne River system were evaluated using nine years of daily measurements of water discharge and total suspended sediment content (TSS) combined with monthly analyses of dissolved and particulate Cd concentrations. This study demonstrates that dissolved and particulate Cd concentrations in the Lot River have strongly decreased in the early 1990s. However, dissolved and particulate Cd concentrations in the Lot River are still higher than those in the Garonne River. In 1992–1998 mean annual Cd concentrations are more or less constant and thus, annual Cd fluxes mainly depend on hydrology. Daily total Cd fluxes range from 0.26 to 966 kg day−1 in the Lot River and from 0.31 to 1360 kg day−1 in the Garonne River, downstream their confluence. During dry years, Cd fluxes at La Réole are dominated by inputs from the upstream Garonne River, whereas during wet years they are controlled by inputs from the polluted Lot River watershed. The relation between particulate and dissolved Cd fluxes depends on TSS concentrations, which appear to be mainly controlled by the succession of floods and low waters reflecting short-term basin-scale climate variability. Cadmium concentrations, fluxes and the ratio between the particulate and dissolved Cd fluxes depends on the absolute value and instantaneous evolution (strong relative increase or decrease) of discharge. An empiric model permits deducing intervals of daily dissolved Cd fluxes from discharge, hydrological key situation and related intervals of ‘typical’ dissolved Cd concentrations. In 1992–1998 the Lot–Garonne River system shows close relations between annual dissolved and particulate Cd fluxes. These relations allow deducing annual particulate Cd fluxes using annual dissolved Cd fluxes obtained from the model. The validation a posteriori shows that our empiric model accurately reproduces the annual Cd fluxes estimated from the field data with uncertainty lower than 25% for dissolved fluxes and lower than 30% for the particulate fluxes. Consequently, the empiric model permits estimating annual dissolved and particulate Cd fluxes in the Lot–Garonne River system, from daily discharge data, without Cd analysis. Cadmium fluxes obtained from the model may be used as approximate values for gross fluvial Cd inputs into the Gironde estuary.

Marine Chemistry, 2002

In order to understand the relationship between authigenic precipitation of U, Mo, Cd, and the re... more In order to understand the relationship between authigenic precipitation of U, Mo, Cd, and the redox properties of the marine environment, we have studied the vertical distribution of these metals and of the major redox species (oxygen, nitrate, manganese, reactive iron, sulfate, carbon, and sulfur) in modern sediment. We have sampled four sites at 150 to 2800 m depth in the Bay of Biscay. At the shallowest station, where sediment is highly bioturbated, organic carbon levels are above 2% and particulate sulfides are abundant. At the deepest stations, sediment is much less bioturbated, and organic carbon levels are lower. At all sites, early diagenesis follows a well-established depth sequence of redox reactions, based on the bacterially mediated oxidation of organic matter. Manganese-oxides and authigenic U and Mo were extracted by an ascorbate solution. Molybdenum is associated with these oxides in the oxic part of cores. In the anoxic layer of the sediment, Mo precipitates as a detectable authigenic phase only when sulfide minerals are present, i.e. when sulfate reduction becomes important. In anoxic sediments, Cd enrichment is a good indicator of sulfide production from sulfate reduction even if the production is weak. Uranium precipitates at the depth of reactive iron (III) reduction. No relationship was observed between U and S. The U concentration at the depth of precipitation agrees with values calculated using estimated accumulation rates and a downward diffusive flux of dissolved U from the bottom seawater into the sediment. However, authigenic U concentrations continue to increase in the anoxic part of the cores. Therefore, it is difficult to establish a direct relationship between the process of U accumulation and the flux of Corg to the sediment.

Pharmacology Biochemistry and Behavior, 2003

Drugs of abuse, such as d-amphetamine or nicotine, are generally considered as acting through an ... more Drugs of abuse, such as d-amphetamine or nicotine, are generally considered as acting through an increased release of dopamine in a subcortical structure, the nucleus accumbens, thus inducing locomotor hyperactivity in rats. Following repeated treatments, the same drugs induce a progressive increase in locomotor response called behavioral sensitization. This process has been suggested to play a role in the acquisition and maintenance of addictive behaviors. Here we show that whereas behavioral sensitization to d-amphetamine (0.5 and 0.75 mg/kg) stays constant following three consecutive periods of withdrawal (15, 30 and 30 days), the same experimental conditions completely abolish behavioral sensitization to 0.3 and 0.5 mg/kg nicotine. Indeed, following these periods of withdrawal, locomotor responses to nicotine are identical to those obtained at the first nicotine injection or after repeated saline injections.However, when a monoamine oxidases inhibitor (MAOI), tranylcypromine (3 mg/kg) or pargyline (30 mg/kg), is co-injected with nicotine, behavioral sensitization is maintained despite submission of the animals to the same withdrawal experimental design. Since tobacco smoke is known to contain many compounds including MAOIs, our data suggest that addictive properties of tobacco may not be limited to nicotine. We propose that MAOIs potentiate effects of nicotine on monoamines release.

Science of The Total Environment, 2006

Daily measurements of water discharges and suspended particulate matter (SPM) concentrations and ... more Daily measurements of water discharges and suspended particulate matter (SPM) concentrations and monthly sampling for trace element analyses (Cd, Zn, Pb and Cu) were conducted from 1999 to 2002 on the Garonne, Dordogne and Isle Rivers, the three main tributaries of the Gironde Estuary, France. Dissolved and particulate Cd, Zn, Pb and Cu concentrations in the Isle River were generally higher than those in the Garonne River, despite the known historical polymetallic pollution affecting the Lot–Garonne River system. Even if the relatively high dissolved metal concentrations in the Isle River may be of importance for the local ecosystem, metal inputs into the estuarine and coastal zones are mainly controlled by fluvial transport via the Garonne River. Characteristic element concentration ratios (e.g., Zn/Pb) in SPM and stream sediments from the Dordogne and Isle Rivers suggest two different metal source areas with distinct geochemical signals. Low Zn/Pb ratios (< 8) and low Cu/Pb ratios (< 0.8) have been attributed to upstream source zones in the Massif Central, featuring various ore deposits and mining areas. High Zn/Pb ratios were assigned to downstream sources (e.g., vineyards), partly explaining high Zn and Cu concentrations and high Cu/Pb ratios (> 0.8) in SPM. Although SPM derived from the upstream parts of the studied watersheds may greatly contribute to the observed fluvial metal transport (up to ∼ 80% for Pb), the results suggest that intensive agriculture also considerably influences gross metal (e.g., Zn, Cu) fluxes into the Gironde Estuary. Relative contributions of upstream and downstream source zones may vary from one year to another reflecting hydrological variations and/or reservoir management. Monitoring fluxes and identifying distinct geochemical signals from source areas in heterogeneous watersheds may greatly improve understanding of contaminant transport to the coast.

Hydroécologie Appliquée, 2006

La détermination précise des flux de Cd dissous et particulaire du Lot et de la Garonne impose la... more La détermination précise des flux de Cd dissous et particulaire du Lot et de la Garonne impose la mise en place d'une stratégie d'échantillonnage spécifique. La fiabilité des méthodologies que nous employons a été vérifiée. Nous avons notamment montré que l'échantillonnage des MES par centrifugation de grands volumes d'eau (1000 L) est la méthode la plus adaptée pour calculer des flux, mais aussi pour accéder à la spéciation à l'état solide. Des mesures journalières de débits et de concentrations en MES combinées à des analyses de Cd dissous et particulaire permettent de proposer un bilan de masse de Cd pour le système fluviatile du Lot et de la Garonne. Ce bilan montre que 70-80 % du Cd transporté en aval par la Garonne (La Réole) provient du Lot dont la majorité (∼75 %) provient du bassin de Decazeville via la rivière Riou-Mort. Ce bilan montre également que les sédiments pollués en Cd et accumulés derrière les barrages hydroélectriques constituent une source secondaire en Cd dont la mobilisation dépend des variations hydrologiques, mais aussi des aménagements anthropiques. En considérant l'ensemble des apports fluviaux en Cd, nous estimons que 60-75 % du Cd apporté à l'estuaire de la Gironde est d'origine anthropique. Sur la base des données existantes, validées entre 1994 et 2000, les flux journaliers de Cd dissous ont été recalculés pour le Lot, et des relations caractéristiques entre flux de matières et débits ont été établies. Ainsi nous proposons un modèle prédictif empirique permettant une bonne estimation des flux de Cd dissous et particulaire à partir des seules données de débit. La comparaison de nos données de flux bruts avec les quelques données disponibles de flux nets (e.g. apports à l'océan) de Cd dissous suggère que plus de 50 % du Cd particulaire passent sous forme dissoute pendant les années humides (94 et 96) et que les flux de Cd dissous nets sont supérieurs aux flux totaux bruts pendant les années sèches (91 et 97). Ceci suggère que la réactivité estuarienne girondine libère progressivement sous forme dissoute, la quasi totalité du Cd apporté majoritairement sous forme particulaire par le fleuve. Abstract -In the Lot and Garonne Rivers, the precise determination of the dissolved and particulate Cd fluxes lead us to develop a specific sampling strategy with adapted sampling Article published by EDF and available at http://www.hydroecologie.org or http://dx.doi.org/10.1051/hydro:2006005 20 G. Blanc et al.

Marine Chemistry, 2004

Vertical profiles of heavy metals (Cd, Cu, Cr, Fe, Mn, Ni and Pb) in the particulate and dissolve... more Vertical profiles of heavy metals (Cd, Cu, Cr, Fe, Mn, Ni and Pb) in the particulate and dissolved phases and redox sensitive parameters (dissolved oxygen, nitrate, nitrite and ammonium) were analyzed for the first time in the continuum Maximum Turbidity Zone (MTZ) -Fluid Mud (FM; 50 g l À 1 < suspended particulate matter (SPM) < 500 g l À 1 )-consolidated sediment of a macrotidal, highly turbid estuary: the Gironde. The results show that the fluid mud is a layer of intense metal mobilization due to redox induced dissolution, releasing trace metals into the water column. This newly identified phenomenon creates a transient situation characterized by the onset of diagenetic sequences in the FM, i.e. in the lower part of the water column. These sequences overlie permanent diagenetic sequences in the consolidated sediment, similar to those typically observed in marine and estuarine sediments. The discontinuity of dissolved Cd, Ni and Pb concentrations at the sediment surface indicates that Mn reduction is faster in the FM than in the upper sediment, isolated from the oxic water column by the suboxic FM. Two separate diagenetic signals are preserved, as the installation of the diagenetic sequence in the FM is faster than the molecular diffusion of dissolved compounds through the FM -sediment interface. The diagenetic signal of trace metals (e.g. dissolved Cr maximum) in the upper sediment layer near the FM -sediment interface is interpreted as a transient record of past hydrologic situations, during which the absence of the FM layer permitted the installation of an oxic/suboxic front in the upper sediment. The resuspension of the FM during the spring tide probably results in a new distribution of these elements in the estuary, where they may be stabilized in the dissolved phase (e.g. by chloride complexes or dissolved organic compounds) or be adsorbed onto reactive particles (e.g. freshly precipitated Mn oxyhydroxides). (S. Robert).

Applied Geochemistry, 2004

Heavy metal (Zn, Cd, Cu and Pb) mass balances in the Lot-Garonne fluvial system have been establi... more Heavy metal (Zn, Cd, Cu and Pb) mass balances in the Lot-Garonne fluvial system have been established for 1999 and 2000. The mean annual discharges of these years are close to the mean discharge of the previous decade. The estimated annual dissolved and particulate fluxes in this model watershed integrate daily input from diffuse and point sources, diffusive fluxes at the water/sediment interface, changes in the dissolved-particulate partition and changes in sediment stock. Cadmium, Zn, Cu and Pb entering the Gironde estuary via the Garonne River (11–14 t a−1 of Cd; 1330–1450 t a−1 of Zn; 126–214 t a−1 of Cu and 127–155 t a−1 of Pb) are mainly transported in the particulate phase and the major part (i.e. ∼74 to 96% for Cd, ∼60% for Zn, ∼50 to 60% for Cu and ∼80% for Pb) is transported by the Lot River. The main anthropogenic heavy metal point source is located in a small upstream watershed (Riou-Mort River) accounting for at least 47% (Cd), ∼20% (Zn), ∼4% (Cu) and ∼7 to 9% (Pb) of the total heavy metal inputs into the Garonne River, although it contributes only 1% of the discharge. Mass balances for 1999 suggest that under mean annual hydrologic conditions on the basin scale, the heavy metal budget of the Lot-Garonne fluvial system is balanced and that the stocks of Cd [200 t; Environ. Tech. 16 (1995) 1145] and Zn in the Lot River sediment are constant under mean discharge conditions. Heavy metal input by molecular diffusion at the sediment surface represents an important component of dissolved metal inputs into the system (e.g. 30% for Cu). Except for Cu, these dissolved inputs are totally removed from solution by SPM. Based on the generally constant Zn/Cd (∼50) concentration ratio in sediment cores from the polluted Lot River reaches and the sediment stock of Cd [200 t; Environ. Tech. 16 (1995) 1145], the present day Zn stock in the Lot River sediments has been estimated at about 10,000 t. In addition to the mobilization of river-bed sediment and associated heavy metals by intense floods, local human activities, including river-bed dredging, may strongly modify the heavy metal budget of the river system. In 2000, the dredging-related remobilization of polluted Lot River sediment released 2–6 t Cd. This additional Cd point source was estimated to account for 15–43% of the gross inputs into the Gironde Estuary.

Drugs of abuse, such as psychostimulants and opiates, are generally considered as exerting their ... more Drugs of abuse, such as psychostimulants and opiates, are generally considered as exerting their locomotor and rewarding effects through an increased dopaminergic transmission in the nucleus accumbens. Noradrenergic transmission may also be implicated because most psychostimulants increase norepinephrine (NE) release, and numerous studies have indicated interactions between noradrenergic and dopaminergic neurons through ␣1-adrenergic receptors. However, analysis of the effects of psychostimulants after either destruction of noradrenergic neurons or pharmacological blockade of ␣1-adrenergic receptors led to conflicting results. Here we show that the locomotor hyperactivities induced by D-amphetamine (1-3 mg/kg), cocaine (5-20 mg/kg), or morphine (5-10 mg/kg) in mice lacking the ␣1b subtype of adrenergic receptors were dramatically decreased when compared with wild-type littermates. Moreover, behavioral sensitizations induced by D-amphetamine (1-2 mg/kg), cocaine (5-15 mg/kg), or morphine (7.5 mg/kg) were also decreased in knock-out mice when compared with wild-type. Ruling out a neurological deficit in knock-out mice, both strains reacted similarly to novelty, to intraperitoneal saline, or to the administration of scopolamine (1 mg/ kg), an anti-muscarinic agent. Finally, rewarding properties could not be observed in knock-out mice in an oral preference test (cocaine and morphine) and conditioned place preference (morphine) paradigm.