A Case Study of Spectral and Non‐Spectral Interferences on Copper Isotope Measurements by Multi‐Collector ICP‐MS (Wet Plasma)     

Jérôme C. J. Petit  Aurélien Taillez  Nadine Mattielli 《Geostandards and Geoanalytical Research》2013,37(3):319-335

Mathematical modelling was combined with experimental Cu isotope measurements to demonstrate the effect of the sample matrix in changing the absolute and relative abundances of spectral interferences from Ti and Cr species. This unforeseen non‐spectral effect, evidenced by variable inaccuracies of the different Zn‐normalised Cu isotope ratios, was investigated by comparing real sedimentary samples and artificial solutions intended to match the Cu:Ti:Cr ratios of the real samples after (one or two step) chromatographic processing. Artificial solutions showed positive bias in δ⁶⁵Cu_X/Y with the magnitude depending on (a) the ^6XZn/^6YZn ratio used for normalisation, (b) the Ti/Cu ratio and (c) the transmission coefficient of the TiO species. In contrast, real samples showed different δ⁶⁵Cu_X/Y patterns and displayed a more complex population of Ti and Cr oxides and hydroxides, giving rise to positive and negative inaccuracies that were two to six times higher compared with the artificial samples. The results evidence contrasting behaviour of Ti and Cr when forming polyatomic species in the plasma and stress that artificial solutions may fail to predict how residual elements interact with the analyte/dopant pair during MC‐ICP‐MS analyses. More importantly, the study shows that all Zn isotope ratios do not have the same merit in correcting for mass bias in the presence of matrix elements and should all be monitored to verify the absence of spectral interferences for Cu isotope measurements. In this respect, accurate Cu data could be generally obtained by a two‐step chromatographic purification providing a minimum reduction of ~ 21000 and ~ 3000 times the initial amounts of Ti and Cr, respectively.  相似文献   

Proceedings of the Workshop on the Role of Volatiles and Atmospheres on Martian Impact Craters     

Nadine G. Barlow  Sarah T. Stewart  Olivier S. Barnouin‐Jha 《Meteoritics & planetary science》2006,41(10):1423-1424

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Polarization in the young cluster NGC 6611: circumstellar, interstellar, or ... both?     

Pierre Bastien  François Ménard  Patrice Corporon  Nadine Manset  Frédérick Poidevin  Gaspard Duchêne  Jean-Louis Monin 《Astrophysics and Space Science》2004,292(1-4):427-433

We obtained linear polarization observations of 82 A/B-type stars in the young cluster NGC 6611, in order to probe the circumstellar material and to search for any evidence of intracluster or interstellar material that could also contribute to the polarization. We found linear polarization values that reach up to 14%. We consider the distribution of the polarization, its position angle, correlations with extinction and membership probability, polarization variability and wavelength distribution to identify the origin of the polarization toward NGC 6611. The polarization is found to be dominated by interstellar polarization, although some stars also have some circumstellar polarization. There is no evidence for intracluster dust. Rather, the dust must be located in a low density cloud toward the general line of sight to NGC 6611 and in front of it. The depth of that cloud along the line of sight increases slowly from the south–east to the north–west. The cloud is threaded by a very uniform magnetic field.  相似文献   

Holocene Refreshening and Reoxygenation of a Bothnian Sea Estuary Led to Enhanced Phosphorus Burial     

Nikki Dijkstra  Nadine B. Quintana Krupinski  Masako Yamane  Stephen P. Obrochta  Yosuke Miyairi  Yusuke Yokoyama  Caroline P. Slomp 《Estuaries and Coasts》2018,41(1):139-157

Salinity variations in restricted basins like the Baltic Sea can alter their vulnerability to hypoxia (i.e., bottom water oxygen concentrations <2 mg/l) and can affect the burial of phosphorus (P), a key nutrient for marine organisms. We combine porewater and solid-phase geochemistry, micro-analysis of sieved sediments (including XRD and synchrotron-based XAS), and foraminiferal δ¹⁸O and δ¹³C analyses to reconstruct the bottom water salinity, redox conditions, and P burial in the Ångermanälven estuary, Bothnian Sea. Our sediment records were retrieved during the Integrated Ocean Drilling Program (IODP) Baltic Sea Paleoenvironment Expedition 347 in 2013. We demonstrate that bottom waters in the Ångermanälven estuary became anoxic upon the intrusion of seawater in the early Holocene, like in the central Bothnian Sea. The subsequent refreshening and reoxygenation, which was caused by gradual isostatic uplift, promoted P burial in the sediment in the form of Mn-rich vivianite. Vivianite authigenesis in the surface sediments of the more isolated part of the estuary ultimately ceased, likely due to continued refreshening and an associated decline in productivity and P supply to the sediment. The observed shifts in environmental conditions also created conditions for post-depositional formation of authigenic vivianite, and possibly apatite formation, at ～8 m composite depth. These salinity-related changes in redox conditions and P burial are highly relevant in light of current climate change. The results specifically highlight that increased freshwater input linked to global warming may enhance coastal P retention, thereby contributing to oligotrophication in both coastal and adjacent open waters.  相似文献   

Mineralogy and the release of trace elements from slag from the Hegeler Zinc smelter,Illinois (USA)     

Nadine M. Piatak  Robert R. Seal II 《Applied Geochemistry》2010

Slag from the former Hegeler Zn-smelting facility in Illinois (USA) is mainly composed of spinifex Ca-rich plagioclase, fine-grained dendritic or coarse-grained subhedral to anhedral clinopyroxenes, euhedral to subhedral spinels, spherical blebs of Fe sulfides, silicate glass, and less commonly fayalitic olivine. Mullite and quartz were also identified in one sample as representing remnants of the furnace lining. Secondary phases such as goethite, hematite and gypsum are significant in some samples and reflect surficial weathering of the dump piles or represent byproducts of roasting. A relatively rare Zn-rich material contains anhedral willemite, subhedral gahnite, massive zincite, hardystonite and a Zn sulfate (brianyoungite), among other phases, and likely represents the molten content of the smelting furnace before Zn extraction. The bulk major-element chemistry of most slag samples is dominated by SiO₂, Al₂O₃, Fe₂O₃ and CaO. The bulk composition of the slag suggests a high viscosity of the melt and the mineralogy suggests a high silica content of the melt. Bulk slag trace-element chemistry shows that the dominant metal is Zn with >28.4 wt.% in the Zn-rich material and between 212 and 14,900 mg/kg in the other slags. The concentrations of other trace elements reach the following: 45 mg/kg As, 1170 mg/kg Ba, 191 mg/kg Cd, 242 mg/kg Co, 103 mg/kg Cr, 6360 mg/kg Cu, 107 mg/kg Ni, and 711 mg/kg Pb.  相似文献   

Tracing the metasomatic and magmatic evolution of continental mantle roots with Sr, Nd, Hf and and Pb isotopes: A case study of Middle Atlas (Morocco) peridotite xenoliths     

Nadine Wittig  D. Graham Pearson  Joel A. Baker 《Geochimica et cosmochimica acta》2010,74(4):1417-1435

We studied clinopyroxenes from spinel-facies peridotite xenoliths sampled by the Quaternary intra-plate volcanism of the Middle Atlas (Morocco) and present new trace element and Sr-Nd-Hf isotope data. However, we focus in particular on Pb isotope data and ²³⁸U/²⁰⁴Pb and ²³²Th/²⁰⁴Pb ratios of these clinopyroxenes. This data allows us to investigate: (a) the timing of metasomatic events, (b) the prevalence and persistence of elevated ²³⁸U/²⁰⁴Pb, ²³²Th/²³⁸U and ²³²Th/²⁰⁴Pb in continental mantle roots and (c) the ²³⁸U/²⁰⁴Pb and ²³²Th/²⁰⁴Pb composition of putative basaltic melts generated from such metasomatised sub-continental lithospheric mantle (SCLM).Incompatible trace element concentrations in these clinopyroxenes are elevated, marked by high-field strength element depletion and fractionated elemental ratios (e.g., U/Nb, Zr/Hf) most consistent with enrichment due to carbonatitic liquids. Sr, Nd and Hf isotopes have an affinity to HIMU.U, Th and Pb abundances in the clinopyroxenes generally exceed estimates of primitive mantle clinopyroxene. Pb isotope compositions of these clinopyroxenes are radiogenic and vary between ²⁰⁶Pb/²⁰⁴Pb = 19.93-20.25, ²⁰⁷Pb/²⁰⁴Pb = 15.63-15.66 and ²⁰⁸Pb/²⁰⁴Pb = 39.72-40.23. These Pb isotope systematics result in generally negative Δ7/4 but positive Δ8/4; setting these samples distinctly apart from typical HIMU. These Pb isotope compositions are also distinct from the associated host volcanic rocks. ²³⁸U/²⁰⁴Pb and ²³²Th/²⁰⁴Pb of these clinopyroxenes, which range from 26 to 81 and 136 to 399, respectively, are elevated and more extreme than estimates of MORB- and HIMU-source mantle.The Pb isotope evolution of the clinopyroxenes suggests that the metasomatic enrichment is younger than 200 Ma, which discounts the volcanic activity due to the opening of the Atlantic and the onset of the collision of the African and Eurasian plates as processes generating the lithophile element and isotope composition of this continental mantle root. Instead, the enrichment is thought to be associated with the Quaternary intra-plate volcanism in the Middle Atlas. However, the erupted mafic melts have unradiogenic Pb isotopes and lower ²³⁸U/²⁰⁴Pb, ²³²Th/²⁰⁴Pb and ²³²Th/²³⁸U relative to the clinopyroxene and do not seem to have equilibrated with the clinopyroxenes. The high Th abundances and the high ²³²Th/²³⁸U also suggest that the metasomatism was due to carbonatitic liquids.When literature data for Pb isotopes in mantle minerals are considered, the Pb isotope range of Archean, Proterozoic and Phanerozoic continental mantle roots is remarkable in that they are similar to the convecting mantle. This observation does not support the existence of sub-continental lithospheric mantle with high ²³⁸U/²⁰⁴Pb and ²³²Th/²⁰⁴Pb for long periods of time. Consequently, the narrow range of Pb isotopes in SCLM worldwide suggests that only the youngest metasomatic events are recorded by incompatible elements such as U, Th and Pb. Numerical modelling of putative magmas generated from Middle Atlas SCLM by fractional, non-modal melting calculations yield extremely high ²³⁸U/²⁰⁴Pb and ²³²Th/²⁰⁴Pb ratios. For example, pure SCLM magmas generated from 0.5% to 10% melting are anticipated to have ²³²Th/²⁰⁴Pb ratios exceeding those known from terrestrial basalts.  相似文献   

Distribution,abundance and growth of New Zealand sea lion Phocarctos hookeri pups on Campbell Island     

Simon Childerhouse  Nadine Gibbs  Gus McAlister  Shaun McConkey  Helen McConnell  Nathan McNally 《新西兰海洋与淡水研究杂志》2013,47(4):889-898

Nine weeks field work was completed during two trips in January/February and March/ April 2003 to investigate the distribution and abundance of New Zealand sea lion Phocarctos hookeri pups at Campbell Island. A total of 161 pups were tagged and a further 138 dead pups were found. A closed mark‐recapture model was used to estimate the total number of live pups (e.g., tagged plus untagged pups) at Campbell Island in April as 247 (SE = 28, 95% CI 198–308). Pup production at Campbell Island is estimated at 385, which comprises 13% of the total pup production for the species in the 2003 season. This is the first robust estimate of pup production for New Zealand sea lions at Campbell Island. The figure of 385 pups is considerably higher than any of the previous estimates reported from Campbell Island. The high level of pup mortality (36%) at Campbell Island for approximately the first 2 months after birth is higher than the 17% reported for the Auckland Islands for approximately the same period in 2003, but is similar to unusually high levels of mortality (20–30%) reported at the Auckland Islands in recent years. It was not possible to determine the cause of death of the 138 dead pups owing to scavenging and decomposition. Pups were found over the whole Island, with the exception of its northern end. Male pups were significantly heavier and faster growing than female pups over the same period.  相似文献   

Hypotaurine and thiotaurine as indicators of sulfide exposure in bivalves and vestimentiferans from hydrothermal vents and cold seeps     

Garth L. Brand  Robin V. Horak  Nadine Le Bris  Shana K. Goffredi  Susan L. Carney  Breea Govenar  & Paul H. Yancey 《Marine Ecology》2007,28(1):208-218

Vesicomyid clams, vestimentiferans, and some bathymodiolin mussels from hydrothermal vents and cold seeps possess thiotrophic endosymbionts, high levels of hypotaurine and, in tissues with symbionts, thiotaurine. The latter, a product of hypotaurine and sulfide, may store and/or transport sulfide non‐toxically, and the ratio to hypotaurine plus thiotaurine (Th/[H + Th]) may reflect an animal's sulfide exposure. To test this, we analyzed seep and vent animals with in situ sulfide measurements. Calyptogena kilmeri clams occur at high‐sulfide seeps in Monterey Canyon, while C. (Vesicomya) pacifica clams occur at seeps with lower levels but take up and metabolize sulfide more effectively. From one seep where they co‐occur, both had gill thiotaurine contents at 22–25 mmol kg⁻¹ wet mass, and while C. (V.) pacifica had a higher blood sulfide level, it had a lower Th/[H + Th] (0.39) than C. kilmeri (0.63). However, these same species from different seeps with lower sulfide exposures had lower ratios. Bathymodiolus thermophilus [East Pacific Rise (EPR 9°50′ N)] from high‐(84 μm ) and a low‐(7 μm ) sulfide vents had gill ratios of 0.40 and 0.12, respectively. Trophosomes of Riftia pachyptila (EPR 9°50′ N) from medium‐(33 μm ) and low‐(4 μm ) sulfide vents had ratios of 0.23 and 0.20, respectively (not significantly different). Ridgeia piscesae vestimentiferans (Juan de Fuca Ridge) have very different phenotypes at high‐ and low‐sulfide sites, and their trophosomes had the greatest differences: 0.81 and 0.04 ratios from high‐ and low‐sulfide sites, respectively. Thus Th/[H + Th] may indicate sulfide exposure levels within species, but not in interspecies comparisons, possibly due to phylogenetic and metabolic differences. Total H + Th was constant within each species (except in R. piscesae); the sum may indicate the maximum potential sulfide load that a species faces.  相似文献   

Silicate determination in sea water: Toward a reagentless electrochemical method     

Marielle Lacombe  Vronique Garon  Maurice Comtat  Louise Oriol  Joël Sudre  Danile Thouron  Nadine Le Bris  Christine Provost 《Marine Chemistry》2007,106(3-4):489-497

Silicate has been determined in sea water by four different electrochemical methods based on the detection of the silicomolybdic complex formed in acidic media by the reaction between silicate and molybdenum salts. The first two methods are based on the addition of molybdate and protons in a seawater sample in an electrochemical cell. Cyclic voltammetry presents two reduction and two oxidation peaks giving four values of the concentration and therefore increasing the precision. Then chronoamperometry is performed on an electrode held at a constant potential. A semi-autonomous method has been developed based on the electrochemical anodic oxidation of molybdenum, the complexation of the oxidation product with silicate and the detection of the complex by cyclic voltammetry. This method is tested and compared with the classical colorimetric one during ANT XXIII/3 cruise across Drake Passage (January–February 2006). The detection limit is 1 μM and the deviation between both methods is less than 3% for concentrations higher than 10 μM. Finally a complete reagentless method with a precision of 2.6% is described based on the simultaneous formation of the molybdenum salt and protons in a divided electrochemical cell. This latter method should be very useful for developing a reagentless sensor suitable for long term in situ deployments on oceanic biogeochemical observatories.  相似文献   

Habitat use by larval fishes in a temperate South African surf zone   总被引：1，自引：0，他引：1  

Peter Watt-Pringle  Nadine A. Strydom   《Estuarine, Coastal and Shelf Science》2003,58(4):765-774

Larval fishes were sampled in the Kwaaihoek surf zone on the south east coast of South Africa. On six occasions between February and May 2002, larval fishes were collected in two habitat types identified in the inner surf zone using a modified beach-seine net. The surf zone habitats were classified as either sheltered trough areas or adjacent exposed surf areas. Temperature, depth and current measurements were taken at all sites. Trough habitats consisted of a depression in surf topography characterised by reduced current velocities and greater average depth than adjacent surf areas. In total, 325 larval fishes were collected. Of these, 229 were collected in trough and 96 in surf habitats. At least 22 families and 37 species were represented in the catch. Dominant families were the Mugilidae, Sparidae, Atherinidae, and Engraulidae. Dominant species included Liza tricuspidens and Liza richardsonii (Mugilidae), Rhabdosargus holubi and Sarpa salpa (Sparidae), Atherina breviceps (Atherinidae) and Engraulis japonicus (Engraulide). Mean CPUE of postflexion larvae of estuary-dependent species was significantly greater in trough areas. The proportion of postflexion larval fishes in trough habitat was significantly greater than that of preflexion stages, a result that was not apparent in surf habitat sampled. CPUE of postflexion larvae of estuary-dependent fishes was negatively correlated with current magnitude and positively correlated with habitat depth. Mean body length of larval fishes was significantly greater in trough than in surf habitats. These results provide evidence that the CPUE of postflexion larvae of estuary-dependent fishes is higher in trough habitat in the surf zone and this may be indicative of active habitat selection for areas of reduced current velocity/wave action. The implications of this behaviour for estuarine recruitment processes are discussed.  相似文献