42 research outputs found
Inferences from the vertical distribution of Fe isotopic compositions on pedogenetic processes in soils
International audienceThe isotopic compositions of major elements in soils can help understand the mechanisms and processes that control the evolution of soils and the nature and dynamics of the soil constituents. In this study, we investigated the variations of the Fe concentrations and isotopic compositions combined with classical soil parameters, such as granulometry, pH, and C and N concentrations. We selected three soils submitted to different hydrodynamic functioning along a toposequence: a well-drained Cambisol and two hydromorphic soils, an Albeluvisol and a Gleysol. In the Cambisol, the isotopic variations were small indicating little redistribution of Fe which we attributed to centimetric-scale exchanges from the Si-bound to the weakly-bound iron pools and insignificant subsurface Fe export. In contrast, the hydromorphic soils showed an overall variation of 0.37â°for ÎŽ56Fe and an inverse correlation between the Fe isotopic compositions and the oxide-bound Fe concentrations. We suggest that, in the uppermost horizon, the mobilisation of oxide-bound Fe was due to the reducing conditions and predominantly involved the light Fe isotopes. Similarly, within the Bt horizon of the Albeluvisol, the fluctuations of the water table level induced changes in the redox conditions and thus Fe dissolution and transport of isotopically light Fe. The Fe isotopic composition profile in the B/C horizon of the Gleysol is dominated by the signature of the parental material. Overall, the variations of the underground water table combined with topography-driven water flow were suggested to be the main mechanisms of Fe translocation in these hydromorphic soils. Finally, the comparison between Fe isotope profiles in worldwide soils allows us to show that Fe isotopic variations can help discriminate between various mechanisms and scales of Fe transfer in soils and, accordingly, provide information on the evolution of soils, when used in combination with pedological, geochemical, geographical, and environmental characterisations
Response of copper concentrations and stable isotope ratios to artificial drainage in a French Retisol
Copper is a redox-sensitive trace element, which can be both, an essential micronutrient and a pollutant. We therefore analyzed Cu concentrations and stable isotope ratios (ÎŽ65Cu values) in a drained Retisol to trace the response of Cu to a changing hydrological regime and enhanced clay eluviation. The study soil was artificially drained 16 years before sampling resulting in macroscopically visible pedogenetic changes and is thus a suitable site to investigate the influence of pedogenetic processes on the fate of Cu. Samples were collected from all horizons along a trench at four distances from the drain: 0.6 m, 1.1 m, 2.1 m and 4.0 m. In the E&Bt horizon, four different soil volumes (ochre, pale brown, white-grey and black) were sampled at all four distances from the drain. Furthermore, we analyzed soil solutions sampled with piezometer, porous cups, and at the drain outlet. The Cu concentrations were lowest in the surface (Ap) horizons (6.5â8.5 ÎŒg gâ 1) and increased with depth to the clay-rich Bt horizons (10.5â12 ÎŒg gâ 1), because of clay eluviation and associated Cu transport. The ÎŽ65Cu values significantly decreased from the surface (Ap = â 0.25 ± 0.07â°) to the deeper horizons, but showed no significant variation among the deeper horizons (â 0.41 ± 0.28â°) and no correlation with the clay content, indicating that clay eluviation did not significantly affect ÎŽ65Cu values. The isotopically heavier ÎŽ65Cu values in the Ap horizons can probably be explained by agricultural management practices like sludge application and fertilization. Close to the drain (position 0.6 m), Cu concentrations were depleted and the lighter Cu isotope was enriched (â 0.91 ± 0.15â°) in the uppermost part of the E&Bt horizon. We attribute this to the changing redox conditions, caused by the lowering of the water level close to the drain. Copper concentrations in black and ochre volumes were significantly higher than in pale-brown and white-grey volumes. The black volume had significantly higher ÎŽ65Cu values than the ochre volume indicating preferential sorption/occlusion of the heavy Cu isotope by Fe oxides. Enhanced clay eluviation in bulk soil close to the drain and in specific soil volumes did not affect ÎŽ65Cu values. Cu concentrations (2.1â14 ÎŒg Lâ 1) and ÎŽ65Cu (0.04â0.42â°) values in water samples showed no clear relation with redox changes along the trench perpendicular to the drain. The enrichment of the heavy Cu isotope in the solution samples (Î65Cu(soil-solution) = â 0.61 ± 0.41) indicates that reductive Cu mobilization is not the main driver of Cu leaching, because this would preferentially mobilize isotopically light Cu. We conclude that the eluviation of the < 2 ÎŒm fraction, strongly controlled Cu concentrations, but had no discernible effect on ÎŽ65Cu values. The changing redox conditions did not seem to control Cu concentrations and the stable isotope distribution in most of the bulk soil, soil volumes and soil water. Instead, weathering, complexation of leached Cu, Cu application with fertilizers and sorption processes within the soil controlled its ÎŽ65Cu values
Geochronology, geochemistry and isotopic compositions of the volcanic rocks from oceanic (Hawaii) and continental (Eifel) intra-plate environments
The Eifel volcanism is part of the Central European Volcanic Province (CEVP) and is located in the Rhenish Massif, close to the Rhine and Leine Grabens. The Quaternary Eifel volcanism appears to be related to a mantle
plume activity. However, the causes of the Tertiary Hocheifel volcanism remain debated. We present geochronological, geochemical and isotope data to assess the geotectonic settings of the Tertiary Eifel volcanism.
Based on 40Ar/39Ar dating, we were able to identify two periods in the Hocheifel activity: from 43.6 to 39.0 Ma and from 37.5 to 35.0 Ma. We also show that the pre-rifting volcanism in the northernmost Upper Rhine Graben (59 to 47 Ma) closely precede the Hocheifel volcanic activity. In addition, the volcanism propagates from south to north within the older phase of the Hocheifel activity. At the time of Hocheifel volcanism, the tectonic activity in the Hocheifel was controlled by stress field conditions identical to those of the Upper Rhine Graben. Therefore, magma generation in the Hocheifel appears to be caused by decompression due to Middle to Late Eocene extension.
Our geochemical data indicate that the Hocheifel magmas were produced by partial melting of a garnet peridotite at 75-90 km
depth. We also show that crustal contamination is minor although the magmas erupted through a relatively thick continental lithosphere. Sr, Nd and Pb isotopic compositions suggest that the source of the Hocheifel magmas is a mixing between depleted FOZO or HIMU-like material and enriched EM2-like material. The Tertiary Hocheifel and the Quaternary Eifel lavas appear to have a common enriched end-member. However, the other sources are likely to be distinct. In addition, the Hocheifel lavas share a depleted component with the other Tertiary CEVP lavas. Although the Tertiary Hocheifel and the Quaternary Eifel lavas appear to originate from different sources, the potential involvement of a FOZO-like component would indicate the contribution of deep mantle material. Thus, on the basis of the geochemical and isotope data, we cannot rule out the involvement of plume-type material in the Hocheifel magmas.
The Koâolau Scientific Drilling Project (KSDP) has been initiated in order to evaluate the long-term
evolution of Koâolau volcano and obtain information about the Hawaiian mantle plume. High precision Pb triple spike data, as well as Sr and Nd isotope data on KSDP lavas and Honolulu Volcanics (HVS) reveal compositional source variations during Koâolau growth. Pb isotopic compositions indicate that, at least, three Pb end-members are present in Koâolau lavas. Changes in the contributions of each component are recorded in the Pb, Sr and Nd isotopes stratigraphy. The radiogenic component is present, at variable proportion, in all three stages of Koâolau growth. It shows affinities with the least radiogenic âKea-lo8â lavas present in Mauna Kea. The first unradiogenic component was present in the main-shield stage of Koâolau growth but its contribution decreased with time. It has EM1 type characteristics and corresponds to the âKoâolauâ component of Hawaiian mantle plume. The second unradiogenic end-member, so far only sampled by Honololu lavas, has isotopic characteristics similar to those of a depleted mantle.
However, they are different from those of the recent Pacific lithosphere (EPR MORB) indicating that the HVS are not derived from MORB-related source. We suggest, instead, that the HVS result from melting of a plume material. Thus the evolution of a single Hawaiian volcano records the geochemical and isotopic changes within the Hawaiian plume
Monnaies massaliotes du sanctuaire de la Cime de Tournerie et échanges de matériaux entre territoires cÎtiers et alpins.
International audienceThe discovery of a monetary deposit composed of 42 Great Bronze of Marseille (GBM) in the masonry of the sanctuary of the Cime de Tournerie (commune of Roubion, Alpes-Maritimes), led to the hypothesis that ores coming from the copper-bearing deposits of the southern Alps could have been used for the manufacture of certain coins related to the âGBM au Taureauâ type. Metallurgical analyses allow us to compare the isotopic compositions of these coins with those from different deposits. The study shows the existence of a compatibility between the copper used for the first issues of the GBM with bull and the copper deposits located near the sanctuary of the Cime de Tournerie. The existence of privileged relations between the mountain populations of the Mercantour and the maritime Phocaean populations could thus go beyond that of simple monetary circulation.La dĂ©couverte dâun dĂ©pĂŽt monĂ©taire composĂ© de 42 Grands Bronzes de Marseille (GBM) dans les maçonneries du sanctuaire de la Cime de Tournerie (commune de Roubion, Alpes-Maritimes), a conduit Ă Ă©mettre lâhypothĂšse que des minerais provenant des gĂźtes cuprifĂšres des Alpes du sud avaient pu ĂȘtre utilisĂ©s pour la fabrication de certaines monnaies liĂ©es au type « GBM au taureau ». Les analyses mĂ©tallurgiques permettent de comparer les compositions isotopiques de ces derniĂšres avec celles issues de diffĂ©rents gisements. LâĂ©tude montre lâexistence dâune compatibilitĂ© entre le cuivre utilisĂ© pour les premiĂšres Ă©missions des GBM au taureau et les gisements cuprifĂšres situĂ©s Ă proximitĂ© du sanctuaire de la Cime de Tournerie. Lâexistence de relations privilĂ©giĂ©es entre les populations montagnardes du Mercantour et les populations phocĂ©ennes maritimes pourrait donc dĂ©passer celle de la simple circulation monĂ©taire
Monnaies massaliotes du sanctuaire de la Cime de Tournerie et échanges de matériaux entre territoires cÎtiers et alpins.
International audienceThe discovery of a monetary deposit composed of 42 Great Bronze of Marseille (GBM) in the masonry of the sanctuary of the Cime de Tournerie (commune of Roubion, Alpes-Maritimes), led to the hypothesis that ores coming from the copper-bearing deposits of the southern Alps could have been used for the manufacture of certain coins related to the âGBM au Taureauâ type. Metallurgical analyses allow us to compare the isotopic compositions of these coins with those from different deposits. The study shows the existence of a compatibility between the copper used for the first issues of the GBM with bull and the copper deposits located near the sanctuary of the Cime de Tournerie. The existence of privileged relations between the mountain populations of the Mercantour and the maritime Phocaean populations could thus go beyond that of simple monetary circulation.La dĂ©couverte dâun dĂ©pĂŽt monĂ©taire composĂ© de 42 Grands Bronzes de Marseille (GBM) dans les maçonneries du sanctuaire de la Cime de Tournerie (commune de Roubion, Alpes-Maritimes), a conduit Ă Ă©mettre lâhypothĂšse que des minerais provenant des gĂźtes cuprifĂšres des Alpes du sud avaient pu ĂȘtre utilisĂ©s pour la fabrication de certaines monnaies liĂ©es au type « GBM au taureau ». Les analyses mĂ©tallurgiques permettent de comparer les compositions isotopiques de ces derniĂšres avec celles issues de diffĂ©rents gisements. LâĂ©tude montre lâexistence dâune compatibilitĂ© entre le cuivre utilisĂ© pour les premiĂšres Ă©missions des GBM au taureau et les gisements cuprifĂšres situĂ©s Ă proximitĂ© du sanctuaire de la Cime de Tournerie. Lâexistence de relations privilĂ©giĂ©es entre les populations montagnardes du Mercantour et les populations phocĂ©ennes maritimes pourrait donc dĂ©passer celle de la simple circulation monĂ©taire
Monnaies massaliotes du sanctuaire de la Cime de Tournerie et échanges de matériaux entre territoires cÎtiers et alpins.
International audienceThe discovery of a monetary deposit composed of 42 Great Bronze of Marseille (GBM) in the masonry of the sanctuary of the Cime de Tournerie (commune of Roubion, Alpes-Maritimes), led to the hypothesis that ores coming from the copper-bearing deposits of the southern Alps could have been used for the manufacture of certain coins related to the âGBM au Taureauâ type. Metallurgical analyses allow us to compare the isotopic compositions of these coins with those from different deposits. The study shows the existence of a compatibility between the copper used for the first issues of the GBM with bull and the copper deposits located near the sanctuary of the Cime de Tournerie. The existence of privileged relations between the mountain populations of the Mercantour and the maritime Phocaean populations could thus go beyond that of simple monetary circulation.La dĂ©couverte dâun dĂ©pĂŽt monĂ©taire composĂ© de 42 Grands Bronzes de Marseille (GBM) dans les maçonneries du sanctuaire de la Cime de Tournerie (commune de Roubion, Alpes-Maritimes), a conduit Ă Ă©mettre lâhypothĂšse que des minerais provenant des gĂźtes cuprifĂšres des Alpes du sud avaient pu ĂȘtre utilisĂ©s pour la fabrication de certaines monnaies liĂ©es au type « GBM au taureau ». Les analyses mĂ©tallurgiques permettent de comparer les compositions isotopiques de ces derniĂšres avec celles issues de diffĂ©rents gisements. LâĂ©tude montre lâexistence dâune compatibilitĂ© entre le cuivre utilisĂ© pour les premiĂšres Ă©missions des GBM au taureau et les gisements cuprifĂšres situĂ©s Ă proximitĂ© du sanctuaire de la Cime de Tournerie. Lâexistence de relations privilĂ©giĂ©es entre les populations montagnardes du Mercantour et les populations phocĂ©ennes maritimes pourrait donc dĂ©passer celle de la simple circulation monĂ©taire
Tropical Weathering History Recorded in the Silicon Isotopes of Lateritic Weathering Profiles
International audienc
Lead, zinc, and copper redistributions in soils along a deposition gradient from emissions of a Pb-Ag smelter decommissioned 100âŻyears ago
International audienceSourcing and understanding the fate of anthropogenic metals in a historical contamination context is challenging. Here we combined elemental and isotopic (Pb, Zn, Cu) analyses with X-ray Absorption Spectroscopy (XAS) measurements (Zn) to trace the fate, in undisturbed soil profiles, of historical metal contamination emitted by a 167-year-old Pb-Ag smelter decommissioned 100 years ago located in the Calanques National Park (Marseilles, France). Lead isotopic measurements show that entire soil profiles were affected by 74 years of Pb emissions up to similar to 7 km from the smelter under the main NNW wind, and indicate particulate transfer down to 0.8 m at depth. This vertical mobility of anthropogenic Pb contrasts with previous studies where Pb was immobilized in surface horizons. The contribution of anthropogenic Pb to the total Pb concentration in soil was estimated at 95% in surface horizons, and 78% in the deepest horizons. Zinc isotopic signatures of past emissions that are enriched in light isotopes compared to the natural geological background (-0.70 +/- 0.04% and -0.15 +/- 0.02%, respectively), were detected only in the surface horizons of the studied soils. Using XAS analyses, we showed that anthropogenic Zn was transformed and immobilized in surface horizons as Zn-Layered Double Hydroxide, thus favoring the enrichment in heavy isotopes in these surface horizons. No clear evidence of copper contamination by the smelter was found and Cu isotopes point to a bedrock origin and a natural distribution of Cu concentrations
Tropical weathering history recorded in the silicon isotopes of lateritic soils
International audienc
Stable Cu and Zn isotopes as tracers of contamination in organic wasteamended soils
International audienceAgriculture, and particularly animal husbandry, is one of the major waste producing activities on the planet. In response to continuously growing demand for animal protein, livestock production generates increasing amounts of manure. In 2017, 1 billion pigs were produced in the World, with approximately half of it in China. Livestock manure treatment and disposal have become a major issue of the present-day agriculture. Spreading this organicrich amendment on the soil helps improving soil physico-chemical properties and fertility at the same time that allows the manure recycling. Yet, pig and dairy manures are also rich in Cu and Zn. These potentially toxic trace metals are added to the animal feed, but not digested by the animals. Thus, intensive use of pig and dairy manures as amendment has for a consequence massif inputs of Cu and Zn in agricultural soils.In order to anticipate and prevent degradation of agricultural soils amended with livestock manure, it is crucial to understand the sources and the long-term behavior of these exogenous metals. Published works on manure-borne Cu and Zn in soils described rather low plant uptake, contamination of water resources and accumulation within the soil. A few studies, focused on the speciation, showed that Cu and Zn are present as Cu2S and ZnS in the pig manure. However, no ZnS was detected in soils amended with pig slurry, instead, Zn was found to be adsorbed on clay minerals and iron ox-hydroxides. In addition, none of these studies was able to differentiate between natural and exogenous trace elements. We have investigated manure-amended soils and the corresponding pig and dairy manures applied over several years in three experimental sites located in Brazil. We have analyzed Cu and Zn concentrations and isotopic compositions aiming at evaluating the potential of stable Cu and Zn isotopes as tracers of exogenous metal transformation and redistribution in soils. We observed that livestock manure amendments have ratherhomogeneous Zn isotopic compositions but show differences in Cu isotopic compositions, depending on the type of waste (pig slurry or dairy manure). Furthermore, Cu and Zn isotopic compositions of the soils that have received large amounts of manure amendments are (i) different from those of the control soil and (ii) intermediate between the isotopic compositions of the control soil and the manure applied. Thus, although the original isotopic signature of a given manure is most likely modified after spreading on the soil, the input of manure-borne Cu and Zn can be detected in soils, particularly in the case of massive treatments. These preliminary results show that stable Cu and Zn isotopes represent a promising tool for studying the behavior of exogenous trace elements from organic-rich amendments. Further application of this approach opens new perspectives, particularly for investigating target mineral phases and long-term behavior of these metal in soils, as well as for tracing the source of contamination in areas without monitoring history