28 research outputs found
Toxic metal levels and fluxes in the Aulne River and its tributaries; impact of historical mining activities of Huelgoat-Poullaouen
In this study, we quantified the concentrations of toxic metals (Zn, Pb, Cd, Cu and As) in the waters of the Aulne River and its main tributaries. The objective was to assess the dissolved and particulate fluxes at the Aulne outlet and to estimate the contribution of the basins draining the former mining sites of Huelgoat-Poullaouen. Our results indicate not only significant concentrations of Pb, Zn and Cd in the tributaries draining the former mines (RiviĂšre d'Argent and Poullaouen Stream) but also a general contamination of the Aulne in these 3 elements, which ranks this river among the most polluted in France in the same order as the Lot or the Seine. On the other hand, our results do not show any marked anomaly in Cu or As and the levels recorded for these two metals are close to those found in other systems draining agricultural catchments. Our study also highlights the significant contribution of small streams to the overall flux of certain metals (e.g. 15% in the case of the Poullaouen for Pb) and therefore makes it possible to envisage a global remediation of the Aulne River and the Bay of Brest by targeting these small watercourses as a priority.Dans cette Ă©tude, nous avons quantifiĂ© les concentrations en mĂ©taux toxiques (Zn, Pb, Cd, Cu et As) dans les eaux de lâAulne et ses principaux affluents. Lâobjectif Ă©tait de dresser un bilan actuel des flux dissous et particulaires Ă lâexutoire de lâAulne et dâestimer la contribution des bassins drainant les anciens sites miniers de Huelgoat-Poullaouen. Nos rĂ©sultats indiquent non seulement des concentrations importantes de Pb, Zn et Cd dans les affluents drainant les anciennes mines (RiviĂšre dâArgent et ruisseau de Poullaouen) mais aussi une contamination gĂ©nĂ©rale de lâAulne en ces 3 Ă©lĂ©ments, ce qui classe cette riviĂšre parmi les plus polluĂ©es de France au mĂȘme titre que le Lot ou la Seine. A contrario, nos rĂ©sultats ne constatent pas dâanomalie marquĂ©e en Cu ou en As et les teneurs enregistrĂ©es pour ces 2 mĂ©taux sont proches de celles trouvĂ©es pour dâautres systĂšmes drainant des bassins versant agricoles. Notre Ă©tude souligne Ă©galement une contribution importante de petits cours dâeau aux flux global de certains mĂ©taux (e.g. 15% dans le cas du Poullaouen pour le Pb) et permet donc dâenvisager un assainissement global de lâAulne et de la Rade de Brest en sâattaquant prioritairement Ă ces petits cours dâeaux
Trace elements in bivalve shells: How âvital effectsâ can bias environmental studies
International audienceWe report on the concentrations of rare earths (REE), Y, Mg, Mn, Cu, Zn, Sr, Ba, Pb and U in a series of wild scallops (Placopecten magellanicus) collected alive on the same day in Saint Pierre et Miquelon (a French archipelago located south of Newfoundland) and ranging in age from 2 to about 20 years. We analyzed representative fragments from the entire last annual shell growth increment of each animal to assess changes in trace element incorporation with age.No correlation with the age of the animals was obtained for Sr and Mn concentrations, which are quite variable from one individual to another, even of similar age. On the other hand, for REE, Y, Cu, Zn, Ba and U, the concentrations measured in the last annual growth increment formed by animals aged 2 to 7 years are similar. From 8 years of age, the concentrations of these elements increased very strongly (for example for Yb, almost by an order of magnitude between 8 and 20 years of age), and possibly with some variation between individuals of the same age. Two elements show a different behavior: Mg concentrations in the shell margins increase continuously with the age of the animals; Pb concentrations are scattered but seem to decrease with the age of the animals.This turning point in the behavior of the elements from 8 years of age coincides with major metabolic changes, since at this age wild P. magellanicus from Newfoundland reduce their growth, in favor of gamete production. Our results demonstrate that metabolic activity of the animals largely controls the incorporation of many trace elements into the shells. These results demonstrate that the age of the animals must be taken into account when their shells are used to study pollution or (paleo) environmental condition
Stream chemical dynamic and metal accumulation in a temperate watershed affected by agricultural practices (Penzé, NW France)
RationaleUnderstanding the fate of metals in agricultural land is an important issue for agronomic sustainability. This study aimed at quantifying the export/retention of metals in a temperate watershed subject to important manuring activities. MethodsThe chemical composition of the Penze stream was examined at high resolution during a 1-year study in 2012. After immediate on-site filtration, here demonstrated as necessary to avoid modification of the dissolved-particulate partition, the concentrations of 21 elements were determined using inductively coupled plasma (ICP) optical emission spectrometry and ICP mass spectrometry. This dataset was extended with the local atmospheric deposition of several metals (Cd, Cr, Cu, Pb, Ni and Zn) monitored on a monthly basis. ResultsTwo groups were distinguished according to the evolution of the concentrations during floods. Some major cations (Na, Ca, Mg, Sr, K, Ba) and nitrate followed counter-clockwise hysteresis patterns originating from the dilution of the enriched groundwaters by surface waters. Conversely, Al, Fe, Mn, Ti, V, Cr, Co, Ni, Cu, Zn, Cd, Pb and U displayed high dissolved concentration increases at the early stage of floods due to washing out of the enriched soils. ConclusionsThe comparison of stream output fluxes for the two main inputs for the watershed, i.e. atmospheric deposition and manure spreading, indicates that the vast majority of the Cu and Zn (>99 and 96%, respectively), mainly originating from pig manure, is accumulated in the watershed. The accumulation rates for other metals were >60% for Ni and Cr, >75% for As and >90% for Pb and Cd
La SoufriĂšre volcanic eruption in 2021 was not responsible for the high Fe, Al, or Mn concentrations found in stranded Sargassum spp.
Partial melting of a C-rich asteroid: Lithophile trace elements in ureilites
International audienceUreilites are among the most common achondrites and are widely believed to sample the mantle of a single, now-disrupted, C-rich body. We analyzed 17 ureilite samples, mostly Antarctic finds, and determined their incompatible trace element abundances. In order to remove or reduce the terrestrial contamination, which is marked among Antarctic ureilites by light-REE enrichment, we leached the powdered samples with nitric acid. The residues display consistent abundances, which strongly resemble those of the pristine rocks. All the analyzed samples display light-REE depletions, negative Eu anomalies, low (Sr/Euâ)n, and (Zr/Euâ)n ratios which are correlated. Two groups of ureilites (groups A and B) are defined. Compared to group A, group B ureilites, which are the less numerous, tend to be richer in heavy REEs, more light-REE depleted, and display among the deepest Eu anomalies. In addition, olivine cores in group B ureilites tend to be more forsteritic (Mg# = 81.9-95.2) than in group A ureilites (Mg# = 74.7-86.1). Incompatible trace element systematics supports the view that ureilites are mantle restites. REE modelling suggests that their precursors were rather REE-rich (ca. 1.8-2 x CI) and contained a phosphate phase, possibly merrillite. The REE abundances in ureilites can be explained if at least two distinct types of magmas were removed successively from their precursors: aluminous and alkali-rich melts as exemplified by the Almahata Sitta trachyandesite (ALM-A), and Al and alkali-poor melts produced after the exhaustion of plagioclase from the source. Partial melting was near fractional (group B ureilites, which are probably among the least residual samples) to dynamic with melt porosities that did not exceed a couple of percent (group A ureilites). The ureilite parent body (UPB) was almost certainly covered by a crust formed chiefly from the extrusion products of the aluminous and alkali-rich magmas. It is currently uncertain whether the Al and alkali-poor melts produced during the second phase of melting reached the surface of the body. The fact that initial silicate melting of ureilitic precursors would have produced relatively low density liquids capable of forming an external crust to the UPB casts doubt on models that invoke chondritic outer layers to achondritic asteroids
Comparative geochemistry of four ferromanganese crusts from the Pacific Ocean and significance for the use of Ni isotopes as paleoceanographic tracers
Ferromanganese (Fe-Mn) crusts are potential archive of the Ni isotope composition of seawater through time. In this study we aim at (1) understanding Ni isotope fractionation mechanisms and metal enrichment processes in Fe-Mn deposits, (2) addressing global vs. local control of Ni isotope composition of these deposits. Two Fe-Mn crusts from the North Pacific Ocean (Apuupuu Seamount, Hawaii) and two Fe-Mn crusts from the South Pacific Ocean (near Rurutu Island, Austral archipelago of French Polynesia) were characterized for their elemental geochemistry and Ni isotope composition. Geochemical analyses were performed at millimeter intervals in order to provide time-resolved record of Ni isotopes. Chronology and growth rates were determined using cosmogenic 10Be isotope abundances. The results show that, despite different growth rates, textures and geochemical patterns, Fe-Mn crusts from both North and South Pacific Oceans have fairly homogenous Ni isotope compositions over the last âŒ17 Ma, yielding average ÎŽ60/58Ni values of 1.79 ±0.21 â° (2sd, n=31) and 1.73 ±0.21 â° (2sd, n=21) respectively. In one crust sample, however, layers directly in contact with the altered substrate show anomalously light ÎŽ60/58Ni values down to 0.25 ±0.05 â° (2se) together with rejuvenated 10Be/9Be ratios correlating with elevated Ni/Mn ratios. Such patterns are best explained by protracted fluidârock interactions leading to alteration of Mn-phases after crust formation. Isotopically light Ni is best explained by Ni isotope fractionation during adsorption rather than the contribution of external Ni sources (e.g. hydrothermal sources) having light Ni isotope compositions. The combination of our results with previously published data on Fe-Mn crusts indicates that the average Ni isotope composition in deep waters has not changed through the Cenozoic (âŒ70 Ma). We propose that Ni isotope variations in Fe-Mn crusts may not only record variations of Ni sources to the oceans, but also post-depositional processes depending on the growth history and geological settings of Fe-Mn crusts
Trace metal content from holopelagic Sargassum spp. sampled in the tropical North Atlantic Ocean: Emphasis on spatial variation of arsenic and phosphorus
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Trace elements in coralline algae as a new proxy for seawater chemistry and metal pollution
International audienceThe abundances of some macronutrients, and trace elements (K, Al, P, V, Mn, Co, Ni, Cu, Zn, Rb, Sr, Mo, Cs, Ba, Pb, Th, U, Y and REE) were determined in a series of coralline algae (Lithothamnion corallioides) samples (n = 101) collected alive in the Bay of Brest and the Iroise Sea (Western Brittany, NW France), in order to assess the potential of these algae as archives of seawater chemistry and potential metal pollution. REE and Y (REY) patterns are similar in shape to those of local seawater, exhibiting similar La, Ce and Y anomalies, but with abundances ranging between 4 and 5 orders of magnitude higher than seawater values. Variations in La anomalies (La/La* = 1.29-2.08), Y anomalies (Y/Ho = 38.6-55.8), and heavy rare earth enrichments (Prsn/Ersn = 0.22-0.52) are consistent with mixing of seawater with rivers flowing into the Bay of Brest. The behavior of other trace elements, such as Al and Cs, also reflects this mixing. Other parameters and processes can control the abundances of the other elements measured. For example, the presence of organic matter in studied samples controls the abundances of K and Rb. The abundances of base metals (e.g., Co, Ni, Cu) are highly sensitive to the various pollutants present in the Bay of Brest. In particular, the Pb content of coralline algae clearly reflects the pollution caused by mining of a nearby Pb deposit from the 18th to the early 20th century. Our results demonstrate the potential of coralline algae not only for tracing water masses, but also for studying metal pollution
A new chemical separation procedure for the determination of rare earth elements and yttrium abundances in carbonates by ICP-MS
International audienceThe determination of rare earth elements (REEs) and Y in carbonates can be complicated by low REE abundances and the presence of significant amounts of Ba resulting in problematic interferences when analysed by ICP-MS. We describe here a novel ion-exchange method using the DGA resin (TODGA), combined with addition of a Tm spike, which allows the separation of the REEs+Y as a whole prior to analysis using an Element XR ICP-MS. This method was validated with results obtained on three different reference carbonate materials (CAL-S, JLs-1 and BEAN, an in-house standard), yielding reproducibility levels better than 3% (RSD) in most cases. This new separation scheme is particularly well suited for carbonate samples having very low REE contents, but could be equally applied to various rock types and organic-rich sample matrices whenever quantitative Ba removal is required
Trace element variations in mussels' shells from continent to sea: The St. Lawrence system, Canada
International audienceRare Earth Elements (REE) and several trace elements abundances in mussel's shells collected along the St. Lawrence River, the Estuary, and the Gulf of St. Lawrence (EGSL) reveal coherent chemical variations, with a sharp contrast between freshwater and seawater bivalves. In freshwater mussel's shells, Rare Earth Elements and Y (REY) patterns are rather flat. Their Mn and Ba concentrations are higher than those of EGSL mussel shells, which are much richer in Sr. Shale-normalized REY abundances in mussel's shells from the EGSL show positive anomalies in La and Y and well-marked negative anomalies in Ce, reflecting those of seawater. Prince Edward Island shells show light REE depletion relative to PAAS, positive La and Y anomalies, and negative Ce anomalies. Our data confirm the lack of detectable Gd pollution in the St. Lawrence River and in the EGSL, as well as Pb pollution at the mouth of the Saguenay Fjord and near Rimouski