Surface phase transformations,surface complexation and solubilities of hydroxyapatite in the absence/presence of Cd(II) and EDTA     

Karin Viipsi  Staffan Sjöberg  Andrey Shchukarev  Kaia Tõnsuaadu 《Applied Geochemistry》2012

The removal of Cd from aqueous solutions by hydroxyapatite (HAP) was investigated with and without EDTA being present. Batch experiments were carried out using synthetic hydroxyapatite with Ca/P 1.57 and a specific surface area of 37.5 m²/g in the pH range 4–9 (25 °C; 0.1 M KNO₃). The surface composition of the solid phases were analysed by X-ray Photoelectron Spectroscopy (XPS). The surface layer of HAP was found to undergo a phase transformation with a (Ca + Cd)/P atomic ratio of 1.4 and the involvement of an ion exchange process (Ca²⁺ ↔ Cd²⁺). The amount of Cd removed from the solution increased with increasing pH, reaching ≈100% at pH 9. In the presence of EDTA Cd removal was reduced due to the formation of [CdEDTA]²⁻ in solution. The solubility of HAP increases in the presence of EDTA at pH values above 5, mainly due to the formation of [CaEDTA]²⁻. In contrast to this, the solubility was found to decrease in the presence of Cd²⁺ and CdEDTA²⁻. Using XPS the formation of a Cd-enriched HAP surface was found, which was interpreted as the formation of a solid solution of the general composition: Ca_8.4-xCd_x(HPO_4)1.6(PO_4)4.4(OH_)0.4${\text{Ca}}_{8.4-x}{\text{Cd}}_x({\text{HPO}}_4{)}_{1.6}({\text{PO}}_4{)}_{4.4}(\text{OH}{)}_{0.4}$.  相似文献   

Mg-(Fe + Ti)-Al petrochemical diagram for the melting of mantle pyrolite: Implications for the derivation conditions of the parental magmas of major volcanic series     

Zh. A. Fedotov 《Petrology》2012,20(7):640-657

The Mg-(Fe + Ti)-Al melting diagram for pyrolite based on experimental data from literature shows the composition of the liquid as a function of pressure and the degree of pyrolite melting. Three mechanisms of liquid separation from a mantle source material are discussed: (i) gravitational mechanism, which works at a degree of source material melting of 25%, (ii) filter pressing mechanism, which is efficient at degrees of melting lower than 2%, and (iii) nearly complete local melting of mantle material. Garnet in the solid residue is thought to play an important role by affecting the chemistries of mantle magmas. The comparison of petrochemical and experimental data in a Mg-(Fe + Ti)-Al ternary plot shows that picrite and ferropicrite alcaline primary magmas are segregated at depths of 120 and 210 km, respectively, in the garnet stability zone, at degrees of melting lower than 2%; and tholeiite basalt magmas are segregated above this zone. At degrees of melting of 25%, picrobasalt, komatiite-basalt, picrite, and ferropicrite primary magmas of the tholeiite series are derived at depths of 80, 130, 240, and 300 km, respectively. Ultrabasic komatiite magma is generated at high degrees of mantle source melting, with the solid residues devoid of garnet. The tholeiite basalt series can be produced by two parental melts: aluminous and magnesian basaltic, both separated from the mantle sources via the filter pressing mechanism: the former at depths shallower than 30 km in ocean spreading zones (TOR-2), and the latter at depths of 50?C60 km in oceanic spreading zones (TOR-1) and in the subcontinental lithosphere. Primary magnesian basalt magmas of the calc-alkaline and tholeiite series are derived in the lithospheric mantle at the same depths and low degrees of melting. Different evolutionary trajectories of compositionally similar primary magmas are controlled by the conditions of their further fractional crystallization: in compressional environments and with fluids saturating the melts in subduction zones for the former and in extensional environments and free magma ascent to the surface for the latter. Ultrapotassic rock series, such as lamprophyres, leucitites, kamafugites, lamproites, and kimberlites, are most probably generated via the melting of the metasomatized subcratonic mantle.  相似文献   

Sampling error distribution for the ensemble Kalman filter update step     

Andrey Kovalenko  Trond Mannseth  Geir N?vdal 《Computational Geosciences》2012,16(2):455-466

In recent years, data assimilation techniques have been applied to an increasingly wider specter of problems. Monte Carlo variants of the Kalman filter, in particular, the ensemble Kalman filter (EnKF), have gained significant popularity. EnKF is used for a wide variety of applications, among them for updating reservoir simulation models. EnKF is a Monte Carlo method, and its reliability depends on the actual size of the sample. In applications, a moderately sized sample (40–100 members) is used for computational convenience. Problems due to the resulting Monte Carlo effects require a more thorough analysis of the EnKF. Earlier we presented a method for the assessment of the error emerging at the EnKF update step (Kovalenko et al., SIAM J Matrix Anal Appl, in press). A particular energy norm of the EnKF error after a single update step was studied. The energy norm used to assess the error is hard to interpret. In this paper, we derive the distribution of the Euclidean norm of the sampling error under the same assumptions as before, namely normality of the forecast distribution and negligibility of the observation error. The distribution depends on the ensemble size, the number and spatial arrangement of the observations, and the prior covariance. The distribution is used to study the error propagation in a single update step on several synthetic examples. The examples illustrate the changes in reliability of the EnKF, when the parameters governing the error distribution vary.  相似文献   

The use of FTIR methods for rapid determination of contents of mineral and biogenic components in lake bottom sediments,based on studying of East Siberian lakes     

S. K. Petrovskii  O. G. Stepanova  S. S. Vorobyeva  T. V. Pogodaeva  A. P. Fedotov 《Environmental Earth Sciences》2016,75(3):226

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The data zoo in Astro-WISE     

Gijs A. Verdoes Kleijn  Andrey N. Belikov  John P. McFarland 《Experimental Astronomy》2013,35(1-2):187-201

In this paper we describe the way the Astro-WISE information system (or simply Astro-WISE) supports the data from a wide range of instruments and combines multiple surveys and their catalogues. Astro-WISE allows ingesting of data from any optical instrument, survey or catalogue, processing of this data to create new catalogues and bringing in data from different surveys into a single catalogue, keeping all dependencies back to the original data. Full data lineage is kept on each step of compiling a new catalogue with an ability to add a new data source recursively. With these features, Astro-WISE allows not only combining and retrieving data from multiple surveys, but performing scientific data reduction and data mining down to the rawest data in the data processing chain within a single environment.  相似文献   

Astro-WISE interfaces     

Andrey N. Belikov  Willem-Jan Vriend  Gert Sikkema 《Experimental Astronomy》2013,35(1-2):301-318

From a simple text interface to a graphical user interfaces—Astro-WISE provides the user with a wide range of possibilities to interact with the information system according to the user’s tasks and use cases. We describe a general approach to the interfacing of a scientific information system. We use this approach to create a number of services, which allows the user to browse the data stored in the system, to process the data and to exchange the newly created images and catalogs with the users within the system and wider astronomical community. Reusability of interfaces and services is another important feature of our approach. It reduces the time and resources spent to interface other information systems created from Astro-WISE.  相似文献   

Change of Internal Ocean Circulation Variations in Warming Climate     

Polonsky  A. B.  Fedotov  A. B. 《Doklady Earth Sciences》2022,504(1):310-314

Doklady Earth Sciences - Using numerical simulation results in the scope of two-layer oceanic model, it is shown that weakening of wind-driven circulation in the warming climate should be...  相似文献