The influence of various seawater components on the buffer capacity for CO2     

A. De Luca Rebello  Isabel N.S. Moreira 《Marine Chemistry》1982,11(1):33-41

A series of experiments was performed using artificial seawater samples of increasing complexity, in order to identify, qualitatively and quantitatively, the contribution of main seawater components on the buffer capacity for CO₂.The results show that magnesium plays the most important role in the uptake, enhancing the capacity of the carbonate system alone by more than 100%.  相似文献   

A VAPID analysis of interstellar lithium in the ζ Oph sightline     

Ian D. Howarth  Richard J. Price  Ian A. Crawford  Isabel Hawkins 《Monthly notices of the Royal Astronomical Society》2002,335(2):267-274

We present observations of the Li  i 6708 Å doublet in the ζ Oph sightline, obtained at a resolution of ∼10⁶ and a signal-to-noise ratio of ∼1200, together with supplementary observations of K  i λ 7699 and the Na  i λ 3302 doublet. These observations marginally resolve the main '−15 km s⁻¹' system into its two principal clouds; we model the data using standard physical assumptions, but in a statistically rigorous manner, taking fully into account the hyperfine, doublet and isotopic structure for each species, in each cloud, using a new code, vapid . The average  ⁷Li/⁶Li  ratio determined in this sightline is  1.12±0.20 dex  (68 per cent confidence interval), in excellent agreement with the solar-system (meteoritic) value. The ratios in the individual clouds are determined with less precision, but are also consistent with the solar-system value, as is the total lithium abundance (with little evidence for depletion). The thermal and 'turbulent' broadening in the two clouds is discussed on the basis of observed line widths.  相似文献   

Predicted radio-continuum emission from the little Homunculus of the η Carinae nebula     

R. F. González  G. Montes  J. Cantó  L. Loinard 《Monthly notices of the Royal Astronomical Society》2006,373(1):391-396

In this paper, we compute theoretically the flux density and the spectral index of the free–free radiation at radio wavelengths produced by shocks in the inner bipolar emission nebula called the little Homunculus around the star η Carinae. The little Homunculus is believed to have formed as a result of the minor eruption suffered by the star in the 1890s. In our model, we consider a simplified interacting stellar wind scenario where the post-outburst η Carinae wind collides with the eruptive outflow (both assumed to be bipolar with conical symmetry). As a result of the interaction, shock-wave structures are formed and generate the development of two polar caps moving in opposite directions. After ∼100 yr (i.e. at present times), the polar caps are located ±2.3 arcsec on each side of the star, and remain embedded within the larger bipolar Homunculus that extends from −8 to +8 arcsec along its major axis. Using observational estimates of the characteristics of the eruptive event of the 1890s, and of the ambient wind powered by η Carinae in the decades after the eruption ended, we study the evolution of the polar caps formed as a result of a sudden increase in the wind velocity and an instantaneous drop in the mass-loss rate (just after the eruption) at the injection radius. We found that the little Homunculus emits continuum radiation that can be detected at radio frequencies and that indeed represents an important contribution to the total free–free emission detected from the η Carinae nebula.  相似文献   

On the Construction of Bootstrap Confidence Intervals for Estimating the Correlation Between Two Time Series Not Sampled on Identical Time Points     

Trottini  Mario  Vigo  Isabel  Vargas-Alemañy  Juan A.  García-García  David  Fernández  José 《Mathematical Geosciences》2021,53(8):1813-1840

Mathematical Geosciences - Two important issues characterize the design of bootstrap methods to construct confidence intervals for the correlation between two time series sampled (unevenly or...  相似文献   

The rip current hazard in Costa Rica   总被引：1，自引：1，他引：0  

Isabel Arozarena  Chris Houser  Alejandro Gutiérrez Echeverria  Christian Brannstrom 《Natural Hazards》2015,77(2):753-768

  相似文献   

Solar influence and hydrological variability during the Holocene from a speleothem annual record (Molinos Cave,NE Spain)   总被引：1，自引：0，他引：1       下载免费PDF全文

Arsenio Muñoz  Miguel Bartolomé  Alicia Muñoz  Carlos Sancho  Ana Moreno  John C. Hellstrom  Mª Cinta Osácar  Isabel Cacho 《地学学报》2015,27(4):300-311

We present a multi‐proxy approach to reconstructing Holocene climate conditions in northeastern Spain based on an excellent correlation among the lamina thickness, colour parameters and isotope (δ¹⁸O and δ¹³C) variations recorded in a speleothem. An age model constructed from five U/Th dates and annual lamina counting suggests that the uppermost 14.7 cm of the MO‐7 stalagmite grew between 7.2 and 2.5 ka before present but experienced a growth hiatus from 4.9 to 4.3 ka. Three spectral analysis methods were applied to 11 time series. The results reveal common solar periodicities on decennial (Gleissberg cycle) and centennial (De Vries‐Suess cycle) scales. The onset of Holocene carbonate precipitation in the MO‐7 stalagmite appears to be associated with a cold, wet period, whereas the hiatus and the end of growth are related to warm, dry periods. This environmental trend fits well within the regional Holocene climate.  相似文献   

The application of diffusion–reaction mixed model to assess the best experimental conditions for bark chemical activation to improve copper(II) ions adsorption     

G. Montes-Atenas  F. Valenzuela  S. Montes 《Environmental Earth Sciences》2014,72(5):1625-1631

Natural sorbents have been thoroughly assessed to determine their adsorption capabilities to remove pollutants from industrial wastewaters. Among them, pine bark has demonstrated potential for carrying out the removal of contaminants, particularly heavy metals, at the level of traces present in dissolved state. Nevertheless, to move towards the wastewater treatment implementation at large scale, the handling and processing requirements of pine bark to optimise the adsorption of heavy metals must be fully assessed. This research study presents a new mathematical model to evaluate the impact of acid pre-treatment of pine bark on heavy metals adsorption at different pine bark-aqueous solution pulp densities. A diffusion–reaction mixed model was developed and applied to the case study of copper(II) adsorption onto pine bark. The low binding energy inferred from analysing the adsorption isotherms suggested that a diffusive mechanism is governing the whole process. The mixed diffusion–reaction kinetic model indicated that the activation increases the rate at which metal ions are adsorbed, but it reduces the maximum achievable adsorption which in turn restricts its usefulness to relatively high pulp densities (above 10 g/L). The latter constitutes the first step towards optimising the use of bark pine for treating wastewater polluted with heavy metals and for establishing rules for scaling-up the process.  相似文献   

Millennial-scale variations in western Sierra Nevada precipitation during the last glacial cycle MIS 4/3 transition     

Jessica L. Oster  Isabel P. Montañez  Regina Mertz-Kraus  Warren D. Sharp  Greg M. Stock  Howard J. Spero  John Tinsley  James C. Zachos 《Quaternary Research》2014

Dansgaard–Oeschger (D–O) cycles had far-reaching effects on Northern Hemisphere and tropical climate systems during the last glacial period, yet the climatic response to D–O cycles in western North America is controversial, especially prior to 55 ka. We document changes in precipitation along the western slope of the central Sierra Nevada during early Marine Oxygen Isotope Stages (MIS) 3 and 4 (55–67 ka) from a U-series dated speleothem record from McLean's Cave. The timing of our multi-proxy geochemical dataset is coeval with D–O interstadials (15–18) and stadials, including Heinrich Event 6. The McLean's Cave stalagmite indicates warmer and drier conditions during Greenland interstadials (GISs 15–18), signified by elevated δ¹⁸O, δ¹³C, reflectance, and trace element concentrations, and less radiogenic ⁸⁷Sr/⁸⁶Sr. Our record extends evidence of a strong linkage between high-latitude warming and reduced precipitation in western North America to early MIS 3 and MIS 4. This record shows that the linkage persists in diverse global climate states, and documents the nature of the climatic response in central California to Heinrich Event 6.  相似文献   

Radiological and geochemical characteristics of an ultramafic massif (NE Portugal) regarding the site aptness to host a near surface repository for low and intermediate level radwaste     

Pedro Duarte  Lídia Silva  António Mateus  M. Fátima Araújo  Mário Reis  Romão Trindade  Isabel Paiva 《Environmental Earth Sciences》2013,68(2):547-557

The search for suitable sites to install near-surface repositories for low to intermediate level radioactive wastes has increased in the recent years, reflecting both the continuous rise in radioactive materials applications by the society and the increasing awareness of public perception regarding radwaste management. International recommendations towards the application of higher safety standards to low and intermediate level waste disposal sites being developed by the International Atomic Energy Agency (IAEA), and the European Commission decision that each Member State must safely dispose its own radwaste in its territory, according to national radwaste management plans, has leading to new soundly scientific studies. In Portugal, possible locations for that purpose are under study since 2006, following the pre-requisites indicated by IAEA. One of these sites overlaps a significant portion of an ultramafic massif, corresponding to an allochthonous and metamorphosed ophiolite complex. In the surveyed area of this massif, the prevailing rock type consists of (serpentinised) peridotites, occasionally containing irregular bodies of (amphibolitised) gabbros, over which an irregular/ill-developed regolith exists. The activities of ⁴⁰K, ¹³⁷Cs, ²¹⁰Pb, ²²⁶Ra and ²³²Th measured in samples representing three consecutive levels of the regolith upper portion in 13 stations confirm the heterogeneity put in evidence through in situ γ-ray surveys previously performed. The available dataset also demonstrates that radionuclide contents decrease prominently with depth, becoming closer to the bedrock values (up to ca. 41 Bq kg^?1 for ⁴⁰K in flaser-gabbros and near zero for all the remaining cases) but never reaching them. Therefore, the low/moderate radionuclide activity in the regolith upper portion reflect the contribution of sources that are independent of the lithological background; i.e. they indicate external and miscellaneous contributions to the “soil”-forming components, most of them coming from (dry or wet) atmospheric deposition. The chemical composition of the (serpentinised) peridotites and (amphibolitised) gabbros in the surveyed area, as well as their alteration products included in regolith, is homogeneous enough to be used as a faithful reference in monitoring studies of any kind. In addition, the significant ¹³⁷Cs activities measured in some top “soil” samples (up to 92 Bq kg^?1) strongly suggest that there are mineralogical specificities of the peridotite-derived regolith able to fix that radionuclide. This particular feature reinforces the existing criteria that favour the peridotites of Morais as a suitable host for a near surface repository of low to intermediate level radwaste.  相似文献   

Lavras do Sul: A New Equilibrated Ordinary L5 Chondrite from Rio Grande do Sul,Brazil     

M. E. Zucolotto  L. L. Antonello  M. E. Varela  R. B. Scorzelli  Isabel P. Ludka  P. Munayco  E. dos Santos 《Earth, Moon, and Planets》2012,108(2):139-150

The new Brazilian chondrite, Lavras do Sul, was found in 1985 at Lavras do Sul, Rio Grande do Sul State-Brazil (33°30′48″S; 53°54′65″W). It consists of a single mass weighing about 1 kg, covered by a black fusion crust with grayish interior. Four polished thin sections were prepared from a slice weighing 67 g on deposit at the Museu Nacional/UFRJ. It consists mostly of chondrules and chondrule fragments dispersed in a recrystallized matrix. Most chondrules are poorly defined and range in size from 300 to 2,000 μm, although some of them show distinct outlines, particularly when viewed under cross-polarized transmitted and reflected light. The texture of chondrules varies from non-porphyritic (e.g., barred-olivine, radial-pyroxene) to porphyritic ones (e.g., granular olivine as well as olivine-pyroxene). The meteorite contains mainly olivine (Fa_24.9), low-Ca pyroxene (Fs_22.6) and metal phases, with minor amounts of plagioclase, chromite and magnetite. Mössbauer Spectroscopy studies indicate that the metal phase is kamacite, tetrataenite and antitaenite. Veins of secondary iddingsite crosscut the thin section and some ferromagnesian silicates. The chemical composition indicates that Lavras do Sul is a member of the low iron L chondrite group. The poorly delineated chondritic texture with few well-defined chondrules, the occurrence of rare clinopyroxene and plagioclase (and maskelynite) with apparent diameters ranging from 5 to 123 μm led us to classify Lavras do Sul as an equilibrated petrologic type 5. The shock features of some minerals suggest a shock stage S3, and the presence of a small amount of secondary minerals such as iddingsite and goethite, a degree of weathering W₁. The meteorite name was approved by the Nomenclature Committee (Nom Com) of the Meteoritical Society (Meteoritic Bulletin Nº99).  相似文献