Buried Paleosols as Reference Objects for Assessing the Current Level of Soil Pollution with Lead in the Lower Volga Steppes

The estimation of soil contamination with anthropogenic lead requires uncontaminated analogues of the recent soils for comparison. For this purpose, a paleosol buried under a 2-m high burial mound of the Bronze Age and protected by it from atmospheric deposition during 4500 years was studied. The content and isotopic composition of mobile and total lead in the buried and recent soils (roadside and remote from lead sources) were compared. Obvious signs of anthropogenic contamination were revealed in only the upper layer of the roadside soil within 10 m from a highway. These were an increase in the absolute content of all lead forms; a high relative content of mobile forms; high ratios of Pb relative to Ti, Zr, and Y; and the similarity between isotopic compositions of the soil lead and the lead from modern atmospheric aerosols and Russian gasoline. Interestingly, no significant difference was found in the total lead contents or in the isotopic compositions between the recent soil remote from roads and the buried soil. However, some signs of anthropogenic impact could be revealed by the analysis of mobile lead forms, which make up a small portion of the total content

Trace element heterogeneity along isochronous growth layers in bivalve shell : consequences for environmental reconstruction

International audienceTo precisely reconstruct environmental changes from high-resolution bivalve shell geochemistry, the shell layers must represent environmental conditions at the time of deposition. Therefore, calcium carbonate along growth lines that formed at the same time should show the same geochemical signature. We test this assumption by evaluating the geochemical spatial homogeneity along growth layers (i.e., shell secreted at a given time) on shell cross-sections of modern shells of the bivalve Protothaca thaca, for ontogenitically young and old specimens. Analyses were carried out using laser ablation ICP-MS and solution nebulization ICP-MS. Scanning electron microscope images showed signs of early diagenesis of old shell sections (close to the umbo) compared with recent (close to the ventral margin). The spatial distribution of Sr/Ca, Mg/Ca and Ba/Ca along growth layers differed consistently between old and recent shell sections. Elemental distribution at the ventral margin of young specimens was similar for the two specimens analyzed and similar to the element distribution in the older specimens at a similar ontogenic stage (closer to the umbo). If a balancing of the shell composition with the surrounding seawater between the old and recent part of the shell, supported by diagenesis, cannot be excluded, we assume that trace element incorporation process at a given time varied with the age of the specimen, in connection with changes of mantle characteristics. Whereas Ba/Ca and Sr/Ca were almost constant for shell secreted at a given time close to the current ventral margin, all individuals showed significant Mg/Ca heterogeneities, with reproducible patterns. We assumed that this would be due to a zonation of the outer epithelium of the mantle that would favor or inhibit the transport of Mg into the extrapallial fluid, and subsequently into the shell. Time-series obtained crossing successive growth layers using laser ablation ICP-MS and solution nebulization ICP-MS on a same-shell growth section were similar for Sr/Ca and Ba/Ca ratios and not for Mg/Ca, which reflected both the different spatial resolutions of the analytical techniques and the heterogeneous distribution of Mg/Ca. In the P. thaca shells, Sr and Ba seemed to be most promising as potential high-resolution environmental proxies. Our study showed that the location of high-resolution analyses points in shell cross-section must be i/ precisely defined and ii/ consistently followed along the shell section to provide accurate environmental records; i.e., without bias related to shell layer heterogeneities

Evaluation of infrared femtosecond laser ablation for the analysis of geomaterials by ICP-MS

International audienceThe capabilities of an infrared (IR) Ti:sapphire femtosecond laser (approximate to 800 nm) to ablate and analyze geomaterials such as monazite, zircon and synthetic glass reference materials is evaluated, with emphasis on U/Pb ratio determinations useful for dating accessory minerals in rocks. We particularly discuss the influence of pulse duration ( respectively 60, 200, 350, 500, 670, 830, 2000 and 3000 fs) on the internal precision ( 2 min ablation), reproducibility over two weeks and accuracy of quadrupole ICP-MS measurements. The best results for all these criteria are obtained when using the shortest pulse duration ( 60 fs). It was found that internal precision and reproducibility were improved by a factor of 3 and 4, respectively, from picosecond to 60 fs pulsewidths. Reproducibility at this pulse duration for U/Pb ratio determinations is of 2% RSD or better, depending on the material analyzed, and this ratio is accurate within this uncertainty. Lead isotopic ratios also benefit from the shortest pulsewidth. They are measured at 60 fs with a precision (< 0.5% RSD) approaching the limitations of quadrupole ICP-MS. Preliminary data were also obtained using the 3rd harmonic (approximate to 266 nm) of the Ti: sapphire fundamental wavelength and they are compared with the infrared mode. There seems to be no obvious analytical benefit to switch from IR to UV in the femtosecond laser ablation regime. Analyses of zircon 91500 with IR pulses led to better repeatability, around 0.9% ( 10 values, 1 sigma), compared to 3% for the UV pulses. The accuracy appears to be comparable for the two wavelengths

Amorphous Materials: Properties, Structure, and Durability{dagger} Arsenic enrichment in hydrous peraluminous melts: Insights from femtosecond laser ablation-inductively coupled plasma-quadrupole mass spectrometry, and in situ X-ray absorption fine structure spectroscopy

International audienc

Trace element geochemistry of the 1991 Mt. Pinatubo silicic melts, Philippines: Implications for ore-forming potential of adakitic magmatism.

The dacite pumice erupted from Mt. Pinatubo on June 15, 1991 (whole-rock, rhyolitic groundmass glasses and homogenized melt inclusions) has been analyzed using inductively coupled plasma-mass spectrometry (ICP-MS), nanosecond and femtosecond laser ablation ICP-MS and secondary ion mass spectrometry (SIMS) to evaluate its ore-forming potential. Data suggest that adakite magmas are metal-rich and concentrate ore metals during magmatic differentiation. Sulfides segregate in limited amounts under the hydrous, oxidizing conditions typical of adakitic magmas resulting in incompatible behavior for Au (6–22 ppb), Cu (26–77 ppm), and Pb, Mo, As, and Sb in melts of dacitic to rhyolitic compositions. Metal transfer from this adakite magma to the coexisting aqueous phase was favored by the peraluminous composition of the rhyolitic melt and high aqueous chloride concentrations. Mass balance calculations suggest that the pre-eruptive aqueous phase could have extracted a minimum of 100 t Au and 5 × 105 t Cu from the Mt. Pinatubo magma. Our data suggest that intrusives having adakitic signatures are genetically associated with Au–Cu and Cu–Mo mineralization, auriferous porphyry copper deposits, and epithermal gold veins. High H2O, Cl, Sr/Y, Pb/Ce, Mo/Ce, As/Ce and Sb/Ce in Mt. Pinatubo melts reflect the contribution of deep fluids derived from subducted sediments and altered MORBs in the dacite genesis. The slab-derived fluids carrying mobile elements are likely responsible for the enrichment of adakite magmas in gold, associated metals and H2O, and may explain the exceptional ore-forming potential of adakite magmatism

Graphene oxide worsens copper-mediated embryo-larval toxicity in the pacific oyster while reduced graphene oxide mitigates the effects

Due to their properties, graphene-based nanomaterials (GBMs) are triggering a great interest leading to an increase of their global production and use in new applications. As a consequence, their release into the environment is expected to increase in the next years. When considering the current knowledge in the evaluation of GBMs ecotoxic potential, studies aiming to evaluate the hazard associated to these nanomaterials towards marine species and particularly considering potential interactions with other environmental pollutants such as metals are scarce. Here we evaluated the embryotoxic potential of GBMs, which include graphene oxide (GO) and its reduced form (rGO), both individually and in combination with copper (Cu) as a referent toxicant, towards early life stages of the Pacific oyster through the use of a standardized method (NF ISO 17244). We found that following exposure to Cu, dose-dependent decrease in the proportion of normal larvae was recorded with an Effective Concentration leading to the occurrence of 50% of abnormal larvae (EC50) of 13.85 ± 1.21 μg/L. Interestingly, the presence of GO at a non-toxic dose of 0.1 mg/L decreased the Cu EC50 to 12.04 ± 0.85 μg/L while it increased to 15.91 ± 1.57 μg/L in presence of rGO. Based on the measurement of copper adsorption, the obtained results suggest that GO enhances Cu bioavailability, potentially modifying its toxic pathways, while rGO mitigates Cu toxicity by decreasing its bioavailability. This research underscores the need to characterize the risk associated to GBMs interactions with other aquatic contaminants and supports the adoption of a safer-by-design strategy using rGO in marine environments. This would contribute to minimize the potential adverse effects on aquatic species and to reduce the risk for economic activities associated to coastal environments

Différences inter-variétales d’accumulation de Cd chez le blé dur (Triticum durum sp.)

National audienc

Caractérisation du standard d’eau de rivièreslrs-6 (nrc-cnrc) compilation interlaboratoiredu silicium, des terres rares et de 21 autreséléments en trace

National audienceL’analyse des eaux nécessite, généralement, des matériaux deréférence certifiés afin d’assurer la qualité des mesures. En Géosciences,il existe peu de standards d’eau de rivière naturelle ayantun nombre important d’éléments certifiés. Or, depuis plusieursannées, une dizaine de laboratoires étudient les éléments majeurset en traces dans les solutions naturelles (groupe de travail del’atelier du CNRS ”Isotrace”) et valident leurs mesures avec les19 éléments certifiés de l’eau de rivière d’Ottawa SLRS produitpar le NRC-CNRC. D’autres éléments non certifiés de cette eausont régulièrement analysés par ces laboratoires à l’aide d’ICP-MS(Inductively Coupled Plasma Mass-Spectrometry) et d’ICP-OES(Inductively Coupled Plasma Optical-Emission Spectrometry).Ces travaux ont fait l’objet de deux publications sur les lots SLRS-4 et SLRS-5. Le nouveau lot SLRS-6 est disponible depuis fin 2015et le groupe de travail propose, dès à présent, les valeurs pour unevingtaine d’éléments en traces non certifiés par le producteur.Comme pour les lots précédents, il a été vérifié que les résultatsobtenus étaient cohérents pour les éléments certifiés par le producteur.Ensuite, des valeurs moyennes et leurs incertitudes associées sontproposées pour des éléments non certifiés par NRC-CNRC telsque le silicium et une vingtaine d’éléments en traces dont les terresrares.L’ensemble des valeurs obtenues est comparé au lot SLRS-5 précédent: SLRS-6 est caractérisé par des teneurs généralement plusfaibles que SLRS-5 ce qui en fait un matériau plus difficile àétudier, proches des limites de détection des techniques utilisées.Enfin, pour comprendre les biais éventuels observés dans les laboratoires,il est aussi discuté individuellement des variations pourchaque élément

Dissolved metal (Fe, Mn, Zn, Ni, Cu, Co, Cd, Pb) and metalloid (As, Sb) in snow water across a 2800 km latitudinal profile of Western Siberia: impact of local pollution and global transfer

Snow cover is known to be an efficient and unique natural archive of atmospheric input and an indicator of ecosystem status. In high latitude regions, thawing of snow provides a sizable contribution of dissolved trace metals to the hydrological network. Towards a better understanding of natural and anthropogenic control on heavy metals and metalloid input from the atmosphere to the inland waters of Siberian arctic and subarctic regions, we measured chemical composition of dissolved (<0.22 µm) fractions of snow across a 2800 km south–north gradient in Western Siberia. Iron, Mn, Co, Ni, and Cd demonstrated sizable (by a factor of 4–7) decrease in concentration northward, which can be explained by a decrease in overall population density and the influence of dry aerosol deposition. Many elements (Mn, Ni, Cu, Cd, Pb, As, and Sb) exhibited a prominent local maximum (a factor of 2–3) in the zone of intensive oil and gas extraction (61–62◦ N latitudinal belt), which can be linked to gas flaring and fly ash deposition. Overall, the snow water chemical composition reflected both local and global (long-range) atmospheric transfer processes. Based on mass balance calculation, we demonstrate that the winter time atmospheric input represents sizable contribution to the riverine export fluxes of dissolved (<0.45 µm) Mn, Co, Zn, Cd, Pb, and Sb during springtime and can appreciably shape the hydrochemical composition of the Ob River main stem and tributaries

Variability in grain cadmium concentration among durum wheat cultivars: impact of aboveground biomass partitioning

Aims Varietal screening was conducted to characterize how French durum wheat lines (Triticum turgidum L. subsp. durum) differ in the concentration of cadmium (Cd) in their grains and to identify the main (eco) physiological processes behind these differences. Methods Eight French and two Canadian durum wheat lines were grown hydroponically in a nutrient solution with a low concentration of Cd (2 nM). At maturity, the partitioning of biomass and Cd among organs was analyzed and elemental profiles of the grain were obtained. Results Grain Cd concentration ranged from 0.03 to 0.08 mu g g(-1) and was thus in the same range as that measured in field trials. The level of Cd in the grain was correlated with levels of P, Mn and Zn. French lines behaved like high-Cd cultivars. A 2.4-fold variation in grain Cd was observed within French lines, which was not explained either by a difference in uptake or by a difference in the root sequestration of Cd. One important finding is that the leaf biomass was the most influential variable explaining the genotypic variation in grain Cd observed within French lines. Conclusions The partitioning of aboveground biomass may influence the concentration of Cd in grain, in addition to the sequestration of Cd in roots