Age et croissance de Raja batis et de Raja naevus en Mer Celtique     

Du Buit  Marie Henriette 《ICES Journal of Marine Science》1977,37(3):261-265

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Uptake of platinum group elements by the marine macroalga, Ulva lactuca     

Andrew Turner  Marie S. Lewis  Leyla Shams  Murray T. Brown 《Marine Chemistry》2007,105(3-4):271-280

Uptake of environmentally relevant platinum group elements (PGE) by the marine macroalga, Ulva lactuca, has been studied. Removal of nM concentrations of Rh(III), Pd(II) and Pt(IV) added to filtered sea water appeared to proceed via pseudo-first-order kinetics, with respective forward rate constants of either 0.0039 or 0.0042 h^− 1, 0.0058 or 0.0096 h^− 1 and 0.0017 or 0.0032 h^− 1, depending on whether an irreversible or reversible reaction was invoked. The (quasi-) equilibrium distribution coefficients, derived from linear fits to uptake (sorption) isotherms, were about 1400, 900 and 350 mL g^− 1 on a dry mass basis for Rh, Pd and Pt, respectively. With increasing sea water pH, over the range 7.9 to 8.4, uptake of Rh by Ulva increased considerably, whereas a small increase in Pt removal was observed; in contrast, uptake of Pd exhibited no clear dependence on pH. The percentage of metal taken up that was internalised within cells, evaluated by washing selected algal samples in 3 mM EDTA, was about 40% for Rh, 80% for Pd and 95% for Pt. Results of this study were interpreted in terms of what is known about the aqueous speciation of PGE in sea water. Thus, Rh exists as cationic hydrated chloride complexes which are readily adsorbed at the algal surface. Palladium has an exceptional affinity for organic ligands, and uptake (and internalisation) appears to be governed by competition for Pd²⁺ from aqueous and algal binding sites. Platinum (IV) exists predominantly as a series of (mainly) negatively charged chloride and mixed hydroxychloride complexes that have little propensity to interact with the algal surface; however, its high degree of internalisation requires at least some interaction with specific and perhaps physiologically active sites.  相似文献   

Inputs of iron,manganese and aluminium to surface waters of the Northeast Atlantic Ocean and the European continental shelf     

Jeroen T.M. de Jong  Marie Boyé  Maria D. Gelado-Caballero  Klaas R. Timmermans  Marcel J.W. Veldhuis  Rob F. Nolting  Constant M.G. van den Berg  Hein J.W. de Baar 《Marine Chemistry》2007

Dissolved Fe, Mn and Al concentrations (dFe, dMn and dAl hereafter) in surface waters and the water column of the Northeast Atlantic and the European continental shelf are reported. Following an episode of enhanced Saharan dust inputs over the Northeast Atlantic Ocean prior and during the cruise in March 1998, surface concentrations were enhanced up to 4 nmol L^− 1 dFe, 3 nmol L^− 1 dMn and 40 nmol L^− 1 dAl and returned to 0.6 nmol L^− 1 dFe, 0.5 nmol L^− 1 dMn and 10 nmol L^− 1 dAl towards the end of the cruise three weeks later. A simple steady state model (MADCOW, [Measures, C.I., Brown, E.T., 1996. Estimating dust input to the Atlantic Ocean using surface water aluminium concentrations. In: Guerzoni. S. and Chester. R. (Eds.), The impact of desert dust across the Mediterranean, Kluwer Academic Publishers, The Netherlands, pp. 301–311.]) was used which relies on surface ocean dAl as a proxy for atmospheric deposition of mineral dust. We estimated dust input at 1.8 g m^− 2 yr^− 1 (range 1.0–2.9 g m^− 2 yr^− 1) and fluxes of dFe, dMn and dAl were inferred. Mixed layer steady state residence times for dissolved metals were estimated at 1.3 yr for dFe (range 0.3–2.9 yr) and 1.9 yr for dMn (range 1.0–3.8 yr). The dFe residence time may have been overestimated and it is shown that 0.2–0.4 yr is probably more realistic. Using vertical dFe versus Apparent Oxygen Utilization (AOU) relationships as well as a biogeochemical two end member mixing model, regenerative Fe:C ratios were estimated respectively to be 20 ± 6 and 22 ± 5 μmol Fe:mol C. Combining the atmospheric flux of dFe to the upper water column with the latter Fe:C ratio, a ‘new iron’ supported primary productivity of only 15% (range 7%–56%) was deduced. This would imply that 85% (range 44–93%) of primary productivity could be supported by regenerated dFe. The open ocean surface data suggest that the continental shelf is probably not a major source of dissolved metals to the surface of the adjacent open ocean. Continental shelf concentrations of dMn, dFe, and to a lesser extent dAl, were well correlated with salinity and express mixing of a fresher continental end member with Atlantic Ocean water flowing onto the shelf. This means probably that diffusive benthic fluxes did not play a major role at the time of the cruise.  相似文献   

Vertical accuracy evaluation of freely available latest high-resolution (30 m) global digital elevation models over Cameroon (Central Africa) with GPS/leveling ground control points.     

Loudi Yap  Ludovic Houetchak Kandé  Robert Nouayou  Nasser Abdou Ngouh  Marie Brigitte Makuate 《International Journal of Digital Earth》2019,12(5):500-524

Digital Elevation Models (DEMs) contain topographic relief data that are vital for many geoscience applications. This study relies on the vertical accuracy of publicly available latest high-resolution (30?m) global DEMs over Cameroon. These models are (1) the ALOS World 3D-30?m (AW3D30), (2) the Shuttle Radar Topography Mission 1 Arc-Second C-Band Global DEM (SRTM 1) and (3) the Advanced Spaceborne Thermal Emission and Reflection Global DEM Version 2 (ASTER GDEM 2). After matching their coordinate systems and datums, the horizontal positional accuracy evaluation was carried out and it shows that geolocation errors significantly influence the vertical accuracy of global DEMs. After this, the three models are compared among them, in order to access random and systematic effects in the elevation data each of them contains. Further, heights from 555 GPS/leveling points distributed all over Cameroon are compared to each DEM, for their vertical accuracy determination. Traditional and robust statistical measures, normality test, outlier detection and removal were used to describe the vertical quality of the DEMs. The test of the normality rejected the hypothesis of normal distribution for all tested global DEMs. Overall vertical accuracies obtained for the three models after georeferencing and gross error removal in terms of Root Mean Square (RMS) and Normalized Median Absolute Deviation (NMAD) are: AW3D30 (13.06?m and 7.75?m), SRTM 1 (13.25?m and 7.41?m) and ASTER GDEM 2 (18.87?m and 13.30?m). Other accuracy measures (MED, 68.3% quantile, 95% quantile) supply some evidence of the good quality of AW3D30 over Cameroon. Further, the effect of land cover and slope on DEM vertical accuracy was also analyzed. All models have proved to be worse in the areas dominated by forests and shrubs areas. SRTM 1 and AW3D30 are more resilient to the effects of the scattering objects respectively in forests and cultivated areas. The dependency of DEMs accuracy on the terrain roughness is evident. In all slope intervals, AW3D30 is performing better than SRTM 1 and ASTER GDEM 2 over Cameroon. AW3D30 is more representative of the external topography over Cameroon in comparison with two others datasets and SRTM 1 can be a serious alternative to AW3D30 for a range of DEM applications in Cameroon.  相似文献   

Modeling the early evolution of Vesta          下载免费PDF全文

Marie Weisfeiler  Donald L. Turcotte  Louise H. Kellogg 《Meteoritics & planetary science》2017,52(5):859-868

The early evolution of the asteroid Vesta has been extensively studied because of the availability of relevant data, especially important new studies of HED meteorites which originated from Vesta and the Dawn mission to Vesta in 2011–2012. These studies have concluded that an early melting episode led to the differentiation of Vesta into crust, mantle, and core. This melting episode is attributed to the decay of ²⁶Al, which has a half‐life of 7.17 × 10⁵ yr. This heating produced a global magma ocean. Surface cooling of this magma ocean will produce a solid crust. In this paper, we propose a convective heat‐transfer mechanism that effectively cools the asteroid when the degree of melting reaches about 50%. We propose that a cool solid surface crust, which is gravitationally unstable, will founder into the solid–liquid mix beneath and will very effectively transfer heat that prevents further melting of the interior. In this paper, we quantify this process. If Vesta had a very early formation, melting would commence at an age of about 1,30,000 yr, and solidification would occur at an age of about 10 Myr. If Vesta formed with a time delay greater than about 2 Myr, no melting would have occurred. An important result of our model is that the early melting episode is restricted to the first 10 Myr. This result is in good agreement with the radiometric ages of the HED meteorites.  相似文献   

Synthesis,crystal structure,high-temperature behavior and magnetic properties of CoBiO(AsO4), a Co analogue of paganoite     

Almaz Aliev  Michael S. Kozin  Marie Colmont  Oleg I. Siidra  Sergey V. Krivovichev  Olivier Mentré 《Physics and Chemistry of Minerals》2015,42(8):663-670

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Hedgerow impacts on soil-water transfer due to rainfall interception and root-water uptake     

G. Ghazavi  Z. Thomas  Y. Hamon  J. C. Marie  M. Corson  P. Merot 《水文研究》2008,22(24):4723-4735

Hedgerow is one of the most important rural landscapes in the world, especially in Europe. Knowledge about the hydrological role of hedgerows is useful in many fields of study, such as hydrological modelling and rural landscape management. The aim of this study was to investigate the impact of a hedgerow on rainfall distribution, soil-water potential gradient, lateral water transfer and water balance. A hillslope with a hedgerow perpendicular to the slope was monitored. To evaluate hedgerow rainfall interception, rainfall was measured (hourly, daily, and by rainfall event) both next to and up to 16 m upslope and 12 m downslope perpendicularly away from the hedgerow. The strongest correlation between rainfall next to the hedgerow and rainfall at more distant points was obtained using data measured per rainfall event. The average percentage of rainfall intercepted equalled 28% for the leafed period and 12% for the leafless period. The impact of the hedgerow on spatial rainfall distribution was related to distance from the hedgerow and rainfall amount. Annual distribution of soil-water potential showed that the hedgerow influenced it up to 9 m upslope and 6 m downslope, the area in which most of the hedgerow's roots were observed. The soil was driest at the end of summer, which delayed soil rewetting during autumn in areas surrounding the hedgerow. Annual groundwater dynamics exhibited three distinct periods due to temporal rainfall distribution and, especially at the end of summer, root-water uptake. In addition, the total potential gradient showed that unsaturated flow was directed towards the hedgerow in summer and autumn. These results indicate that at the local scale hedgerows influences (1) spatial rainfall distribution, (2) soil rewetting, and (3) groundwater recharge, often at distances well beyond the hedgerow's drip line. Consequently, the processes involved in soil-water dynamics around hedgerows should be integrated into relevant hydrological models, especially for catchments with a dense hedgerow network. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Reply to comment on ‘Yamada H,Nakamura F,Watanabe Y,Murakami M and Nogami T. 2005. Measuring hydraulic permeability in a streambed using the packer test. Hydrological Processes 19: 2507–2524’     

Hiroyuki Yamada  Futoshi Nakamura  Yasuharu Watanabe  Marie Murakami  Takeshi Nogami 《水文研究》2008,22(17):3545-3545

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Hydrological regimes in a tropical valley of New Caledonia (SW Pacific): Impacts of wildfires and invasive fauna     

Caroline Marie Clémence Tramier  Pierre Genthon  Quentin Réginald Camille Paul Delvienne  Nicolas Luc Sauvan  Jean-Jérôme Olivier Cassan  Etienne Ebrard  Pascal Sébastien Dumas  Yann Queffélean 《水文研究》2021,35(3):e14071

In New Caledonia wildfires and invasive mammals (deer and wild pigs) constitute the major agents of land surface degradation. Our study reveals the linkage between land cover and water balance on the northeast coast of New Caledonia (2400 mm annual rainfall) located on a micaschist basement. The hydrological regime of characteristic and representative land surfaces is assessed using a 1-year record from three 100 m² plots each, located in a forest area degraded by an invasive fauna, in a woody savannah which is regularly burned, and in a healthy forest area. The three plots present highly contrasting hydrological regimes, with annual and maximum runoff/rain ratios during a rain event of, respectively, 0.82, 0.16, 0.03, and 2.7, 0.7, 0.2, for the degraded forest, the savannah and the healthy forest. Such results suggest that subsurface flow originating from the contributing area above the degraded forest plot should exfiltrate inside the plot. A conceptual model for the degraded forest plot shows that water exfiltrating inside the plot represents 61% of the observed runoff. In savannahs, water should mainly be transferred downstream by subsurface flow within a thick organic soil layer limited by an impervious clay layer at a 20–30 cm depth. Savannahs are generally located above forests and generate the transfer of rainwater to downslope forests. Exfiltration into the forests can be the result of this transfer and depends on the thickness and permeability of the forest topsoils and on topographic gradients. Water exfiltration in forest areas highly degraded by pigs and deer enhances erosion and increases further degradation. It probably also limits percolation in the areas located downstream by increasing the amount of superficial runoff concentrated in gullies.  相似文献   

Emulating exhalative chemistry: synthesis and structural characterization of ilinskite,Na[Cu5O2](SeO3)2Cl3, and its K-analogue     

Vadim M. Kovrugin  Oleg I. Siidra  Marie Colmont  Olivier Mentré  Sergey V. Krivovichev 《Mineralogy and Petrology》2015,109(4):421-430

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