Abundances Of Si Research Articles

Chandraobservation of the Galactic supernova remnant CTB 109 (G109.1–1.0)

Context: We study the X-ray emission of the Galactic supernova remnant (SNR) CTB 109 (G109.1-1.0), which is well-known for its enigmatic half-shell morphology both in radio and in X-rays and is associated with the anomalous X-ray pulsar (AXP) 1E2259+586. Aims: We want to understand the origin of the X-ray bright feature inside the SNR called the Lobe and the details of the interaction of the SNR shock wave with the ambient interstellar medium (ISM). Methods: The Lobe and the northeastern part of the SNR were observed with Chandra ACIS-I. We analysed the spectrum of the X-ray emission by dividing the entire observed emission into small regions. The X-ray emission is best reproduced with one-component or two-component non-equilibrium ionisation models depending on the position. In the two-component model one emission component represents the shocked ISM and the other the shocked ejecta. Results: We detect enhanced element abundances, in particular for Si and Fe, in and around the Lobe. There is one particular region next to the Lobe with a high Si abundance of 3.3 (2.6 - 4.0) times the solar value. This is the first, unequivocal detection of ejecta in CTB 109. Conclusions: The new Chandra data confirm that the Lobe was created by the interaction of the SNR shock and the supernova ejecta with dense and inhomogeneous medium in the environment of SNR CTB 109. The newly calculated age of the SNR is t ~ 1.4 x 10^4 yr.

Search for associations containing young stars: chemical tagging IC 2391 and the Argus association★

We explore the possible connection between the open cluster IC 2391 and the unbound Argus association identified by the SACY survey. In addition to common kinematics and ages between these two systems, here we explore their chemical abundance patterns to confirm if the two substructures shared a common origin. We carry out a homogenous high-resolution elemental abundance study of eight confirmed members of IC 2391 as well as six members of the Argus association using UVES spectra. We derive spectroscopic stellar parameters and abundances for Fe, Na, Mg, Al, Si, Ca, Ti, Cr, Ni and Ba. All stars in the open cluster and Argus association were found to share similar abundances with the scatter well within the uncertainties, where [Fe/H] = -0.04 +/-0.03 for cluster stars and [Fe/H] = -0.06 +/-0.05 for Argus stars. Effects of over-ionisation/excitation were seen for stars cooler than roughly 5200K as previously noted in the literature. Also, enhanced Ba abundances of around 0.6 dex were observed in both systems. The common ages, kinematics and chemical abundances strongly support that the Argus association stars originated from the open cluster IC 2391. Simple modeling of this system find this dissolution to be consistent with two-body interactions.

Study of dwarfs and giants in the Hyades cluster

Results are reported of a study of the atmospheric chemical composition for 12 F5-K0 type stars in the Hyades cluster. The study uses spectra obtained with the 1.93-m telescope of the Haute-Provence Observatory (France) with the ELODIE echelle-type spectrograph in the wavelength range 440–680 nm. The spectral resolution is R = 40000, and S/N is ∼50. The equivalent widths of the lines are measured in the wavelength range 510–680 nm. The main parameters of the stars are determined: the effective temperature T eff, the gravity logg, the microturbulence velocities V t , and the abundances of Na, Mg, Al, Si, Ca, Ti, V, Cr, Fe, Co, Ni, Y, La, Ce, and Nd. The abundance estimates for the dwarfs and giants are similar within the errors of determination, except for the Na abundances.

Abundances determined using Si ii and Si iii in B-type stars: evidence for stratification

It is becoming clear that determination of the abundance of Si using lines of Si II and Si III can lead to quite discordant results in mid to late B-type stars. The difference between the Si abundances derived from the two ion states can exceed one dex in some cases. We have carried out a study intended to clarify which kinds of B stars exhibit this discrepancy, to try to identify regularities in the phenomenon, and to explore possible explanations such as abundance stratification by comparing models to observed spectra. We used spectra from the ESPaDOnS spectropolarimeter and FEROS spectrograph, supplemented with spectra from the ESO and ELODIE archives, of magnetic Bp, HgMn, and normal B-type stars ranging in effective temperature from about 10500 to 15000 K. Using these spectra, we derived abundances using the spectrum synthesis program ZEEMAN which can take into account the influence of magnetic fields. For each star, accurate abundances of Si II, Si III, Ti, Cr, and Fe were derived. All magnetic Bp stars in our sample show a discordance between the derived abundances of the first and second ions of silicon, with the latter being between 0.6 - 1.7 dex higher. The same behaviour is observed in the non-magnetic stars but to a much smaller extent: Si III is enhanced by between 0.3 - 0.8 dex compared to Si II.We do not detect the discrepancy in three stars, HD 22136 (normal), HD 57608 (HgMn) and HD 27295 (HgMn); these are the only stars in our sample for which the microturbulence parameter is significantly different from zero, and which therefore probably have convection occurring in their atmospheres. We find that vertical stratification of silicon in the atmospheres of B-type stars may provide an explanation of this phenomenon, but our detailed stratification models do not completely explain the discrepancies, which may, in part, be due to non-LTE effects.

An aluminium tool for multiple stellar generations in the globular clusters 47 Tucanae and M 4

We present aluminium abundances for a sample of about 100 red giant stars in each of the Galactic globular clusters 47 Tuc (NGC 104) and M 4 (NGC 6121). We have derived homogeneous abundances from intermediate-resolution FLAMES/GIRAFFE spectra. Aluminium abundances are from the strong doublet Al i 8772-8773 Å, as in previous works done for giants in NGC 6752 and NGC 1851, and nitrogen abundances are extracted from a large number of features of the CN molecules by assuming a suitable carbon abundance. We added previous homogeneous abundances of O and Na and newly derived abundances of Mg and Si for our samples of 83 stars in M 4 and 116 stars in 47 Tuc to obtain the full set of elements from proton-capture reactions produced by different stellar generations in these clusters. By simultaneously studying the Ne-Na and Mg-Al cycles of H-burning at high temperature, our main aims are to understand the nature of the polluters at work in the first generation and to ascertain whether the second generation of cluster stars was formed in one or, rather, several episodes of star formation. Our data confirm that in M 4 only two stellar populations are visible. On the other hand, for 47 Tuc a cluster analysis performed on our full dataset suggests that at least three distinct groups of stars are present on the giant branch. The abundances of O, Na, Mg, and Al in the intermediate group can be produced within a pollution scenario; results for N are ambiguous, depending on the C abundance we adopt for the three groups.

Kinematics and chemical abundances of the B star HD 28248

We perform a detailed elemental abundance study of the early-type B star HD 28248 and estimate its orbital path in the Galaxy. From the comparison of spectroscopic observations performed at the European Southern Observatory at La Silla in 2001/Oct/07 with non-LTE synthetic spectra using a new wrapper for the simultaneous fitting of several lines of a given atomic species, the abundances of He, C, N, O, Mg, Al, Si, P, S, Ar and Fe were determined for the first time. The radial velocity of HD 28248 has been also estimated from the positions of centroids of nine neutral helium lines and Mgiiλ 4481Å, allowing to calculate its right-handed Galactic space-velocity components U,V and W and estimate its orbital path in the Galaxy for the first time. Our chemical analysis depicted an outstanding enrichment of several atomic species, particularly [Fe/H]=+0.25dex and [O/Fe]=+0.32dex. The kinematic parameters show that its orbit is confined to the galactic disk with a scale height of 400pc and the star has moved about 4kpc from its birthplace to the current position. The elemental abundances do not follow the predicted [Fe/H] and [O/Fe] gradients currently established for the Galaxy. A hypothetical scenario for the contamination could be the mass transfer in a binary system during previous evolutionary phases.

TAGGING THE CHEMICAL EVOLUTION HISTORY OF THE LARGE MAGELLANIC CLOUD DISK

We have used high-resolution spectra obtained with the multifiber facility FLAMES at the Very Large Telescope of the European Southern Observatory to derive kinematic properties and chemical abundances of Fe, O, Mg and Si for 89 stars in the disk of the Large Magellanic Cloud (LMC). The derived metallicity and [alpha/Fe], obtained as the average of O, Mg and Si abundances, allow us to draw a preliminary scheme of the star formation history occurred in this region of the LMC. The derived metallicity distribution shows two main components: one component (comprising ~ 84% of the sample) is peaked at [Fe/H] = -0.48 dex and it shows an [alpha/Fe] ratio slightly under solar ([alpha/Fe] ~ -0.1 dex). This population was probably originated by the main star formation event occurred 3-4 Gyr ago (possibly triggered by tidal capture of the Small Magellanic Cloud). The other component (comprising ~ 16% of the sample) is peaked at [Fe/H] ~ -1 dex and it shows an [alpha/Fe] ~ 0.2 dex. This population was probably generated during the long quiescent epoch of star formation in between the first episode and the most recent bursts. Indeed, in our sample we do not find stars with chemical properties similar to the old LMC globular clusters nor to the iron-rich and alpha-poor stars recently found in the LMC globular cluster NGC 1718 and predicted to be also in the LMC field, thus suggesting that both these components are small (< 1%) in the LMC disk population.

Major‐element abundances on the surface of Mercury: Results from the MESSENGER Gamma‐Ray Spectrometer

Orbital gamma‐ray measurements obtained by the MESSENGER spacecraft have been analyzed to determine the abundances of the major elements Al, Ca, S, Fe, and Na on the surface of Mercury. The Si abundance was determined and used to normalize those of the other reported elements. The Na analysis provides the first abundance estimate of 2.9 ± 0.1 wt% for this element on Mercury's surface. The other elemental results (S/Si = 0.092 ± 0.015, Ca/Si = 0.24 ± 0.05, and Fe/Si = 0.077 ± 0.013) are consistent with those previously obtained by the MESSENGER X‐Ray Spectrometer, including the high sulfur and low iron abundances. Because of different sampling depths for the two techniques, this agreement indicates that Mercury's regolith is, on average, homogenous to a depth of tens of centimeters. The elemental results from gamma‐ray and X‐ray spectrometry are most consistent with petrologic models suggesting that Mercury's surface is dominated by Mg‐rich silicates. We also compare the results with those obtained during the MESSENGER flybys and with ground‐based observations of Mercury's surface and exosphere.

The Chamaeleon II low-mass star-forming region: radial velocities, elemental abundances, and accretion properties

Radial velocities, elemental abundances, and accretion properties of members of star-forming regions (SFRs) are important for understanding star and planet formation. While infrared observations reveal the evolutionary status of the disk, optical spectroscopy is fundamental to acquire information on the properties of the central star and on the accretion characteristics. 2MASS archive data and the Spitzer c2d survey of the Chamaeleon II dark cloud have provided disk properties of a large number of young stars. We complement these data with spectroscopy with the aim of providing physical stellar parameters and accretion properties. We use FLAMES/UVES+GIRAFFE observations of 40 members of Cha II to measure radial velocities through cross-correlation technique, Li abundances by means of curves of growth, and for a suitable star elemental abundances of Fe, Al, Si, Ca, Ti, and Ni using the code MOOG. From the equivalent widths of the Halpha, Hbeta, and the HeI-5876, 6678, 7065 Angstrom emission lines, we estimate the mass accretion rates, dMacc/dt, for all the objects. We derive a radial velocity distribution for the Cha II stars (<Vrad>=11.4+-2.0 km/s). We find dMacc/dt prop. to Mstar^1.3 and to Age^(-0.82) in the 0.1-1.0 Msun mass regime, and a mean dMacc/dt for Cha II of ~7*10^(-10) Msun/yr. We also establish a relationship between the HeI-7065 Angstrom line emission and the accretion luminosity. The radial velocity distributions of stars and gas in Cha II are consistent. The spread in dMacc/dt at a given stellar mass is about one order of magnitude and can not be ascribed entirely to short timescale variability. Analyzing the relation between dMacc/dt and the colors in Spitzer and 2MASS bands, we find indications that the inner disk changes from optically thick to optically thin at dMacc/dt~10^(-10) Msun/yr. Finally, the disk fraction is consistent with the age of Cha II.

A photospheric metal line profile analysis of hot DA white dwarfs with circumstellar material

Some hot DA white dwarfs have circumstellar high ion absorption features in their spectra, in addition to those originating in the photosphere. In many cases, the line profiles of these absorbing components are unresolved. Given the importance of the atmospheric composition of white dwarfs to studies of stellar evolution, extra-solar planetary systems and the interstellar medium, we examine the effect of including circumstellar line profiles in the abundance estimates of photospheric metals in six DA stars. The photospheric C and Si abundances are reduced in five cases where the circumstellar contamination is strong, though the relative weakness of the circumstellar Si IV absorption introduces minimal contamination, resulting in a small change in abundance. The inability of previous, approximate models to reproduce the photospheric line profiles here demonstrates the need for a technique that accounts for the physical line profiles of both the circumstellar and photospheric lines when modelling these blended absorption features.

Chemical abundances of 1111 FGK stars from the HARPS GTO planet search program

We performed a uniform and detailed abundance analysis of 12 refractory elements (Na, Mg, Al, Si, Ca, Ti, Cr, Ni, Co, Sc, Mn and V) for a sample of 1111 FGK dwarf stars from the HARPS GTO planet search program. 109 of these stars are known to harbour giant planetary companions and 26 stars are hosting exclusively Neptunians and super-Earths. The main goals of this paper are i) to investigate whether there are any differences between the elemental abundance trends for stars of different stellar populations; ii) to characterise the planet host and non-host samples in term of their [X/H]. The extensive study of this sample, focused on the abundance differences between stars with and without planets will be presented in a parallel paper. The equivalent widths of spectral lines are automatically measured from HARPS spectra with the ARES code. The abundances of the chemical elements are determined using a LTE abundance analysis relative to the Sun, with the 2010 revised version of the spectral synthesis code MOOG and a grid of Kurucz ATLAS9 atmospheres. To separate the Galactic stellar populations we applied both a purely kinematical approach and a chemical method. We found that the chemically separated (based on the Mg, Si, and Ti abundances) thin and thick discs are also chemically disjunct for Al, Sc, Co and Ca. Some bifurcation might also exist for Na, V, Ni, and Mn, but there is no clear boundary of their [X/Fe] ratios. We confirm that an overabundance in giant-planet host stars is clear for all the studied elements.We also confirm that stars hosting only Neptunian-like planets may be easier to detect around stars with similar metallicities as non-planet hosts, although for some elements (particulary alpha-elements) the lower limit of [X/H] are very abrupt.

Physical parameters and chemical abundances of [formula omitted] Ceti

A detailed spectroscopic study of a β Cephei variable star, δ Ceti, is presented. Physical fundamental parameters are estimated from the best fitting of 26 neutral helium lines and Balmer profiles: effective temperature, superficial gravity and projected rotation velocity. Non-LTE abundances of He, C, N, O, Ne, Mg, Al, Si, P, S, Ar and Fe are achieved using model atmospheres with updated atomic data. Our analysis show an N-enrichment and Fe overabundance, with [O/Fe]≅ −0.73dex, confirming this object to be a metal-rich star, which is a requirement for the κ-mechanism to trigger the pulsations observed in β Cephei stars.

CHEMICAL ABUNDANCES OF THE MILKY WAY THICK DISK AND STELLAR HALO. I. IMPLICATIONS OF [α/Fe] FOR STAR FORMATION HISTORIES IN THEIR PROGENITORS

We present the abundance analysis of 97 nearby metal-poor (-3.3<[Fe/H]<-0.5) stars having kinematics characteristics of the Milky Way (MW) thick disk, inner, and outer stellar halos. The high-resolution, high-signal-to-noise optical spectra for the sample stars have been obtained with the High Dispersion Spectrograph mounted on the Subaru Telescope. Abundances of Fe, Mg, Si, Ca and Ti have been derived using a one-dimensional LTE abundance analysis code with Kurucz NEWODF model atmospheres. By assigning membership of the sample stars to the thick disk, inner or outer halo components based on their orbital parameters, we examine abundance ratios as a function of [Fe/H] and kinematics for the three subsamples in wide metallicity and orbital parameter ranges. We show that, in the metallicity range of -1.5<[Fe/H]<= -0.5, the thick disk stars show constantly high mean [Mg/Fe] and [Si/Fe] ratios with small scatter. In contrast, the inner, and the outer halo stars show lower mean values of these abundance ratios with larger scatter. The [Mg/Fe], [Si/Fe] and [Ca/Fe] for the inner and the outer halo stars also show weak decreasing trends with [Fe/H] in the range [Fe/H]$>-2$. These results favor the scenarios that the MW thick disk formed through rapid chemical enrichment primarily through Type II supernovae of massive stars, while the stellar halo has formed at least in part via accretion of progenitor stellar systems having been chemically enriched with different timescales.

Abundance analysis of four members of the metal-rich open cluster NGC 6253★

We report on VLT/UVES high-resolution spectra of four members of the old metal-rich open cluster NGC 6253: a main-sequence star, two red-clump stars and a blue straggler. We performed equivalent width analysis and derived Fe, Si, Ca, Ti, Cr and Ni abundances as well as abundance ratios. For our main-sequence star, we obtained a metallicity of (rms), whereas for the two giants we found that our metallicities are on average +0.19 ± 0.13 (rms), lower than what was determined for the same stars in previous studies. We also found that, within the uncertainties, the abundance ratios of α and iron-peak elements match those in the solar surroundings, with the possible exception of Si in two giant stars in our sample.

The chemical diversity of exo-terrestrial planetary debris around white dwarfs

We present Hubble Space Telescope (HST) ultraviolet spectroscopy of the white dwarfs PG 0843+516, PG 1015+161, SDSS 1228+1040, and GALEX 1931+0117, which accrete circumstellar planetary debris formed from the destruction of asteroids. Combined with optical data, a minimum of five and a maximum of 11 different metals are detected in their photospheres. With metal sinking time-scales of only a few days, these stars are in accretion/diffusion equilibrium, and the photospheric abundances closely reflect those of the circumstellar material. We find C/Si ratios that are consistent with that of the bulk Earth, corroborating the rocky nature of the debris. Their C/O values are also very similar to those of bulk Earth, implying that the planetary debris is dominated by Mg and Fe silicates. The abundances found for the debris at the four white dwarfs show substantial diversity, comparable at least to that seen across different meteorite classes in the Solar system. PG 0843+516 exhibits significant overabundances of Fe and Ni, as well as of S and Cr, which suggests the accretion of material that has undergone melting, and possibly differentiation. PG 1015+161 stands out by having the lowest Si abundance relative to all other detected elements. The Al/Ca ratio determined for the planetary debris around different white dwarfs is remarkably similar. This is analogous to the nearly constant abundance ratio of these two refractory lithophile elements found among most bodies in the Solar system. Based on the detection of all major elements of the circumstellar debris, we calculate accretion rates of ≃1.7 × 108 to ≃1.5 × 109 g s−1. Finally, we detect additional circumstellar absorption in the Si IV 1394, 1403 A doublet in PG 0843+516 and SDSS 1228+1040, reminiscent to similar high-ionization lines seen in the HST spectra of white dwarfs in cataclysmic variables. We suspect that these lines originate in hot gas close to the white dwarf, well within the sublimation radius.

HUBBLE SPACE TELESCOPEFUV SPECTRA OF THE POST-COMMON-ENVELOPE HYADES BINARY V471 Tauri

We have carried out an analysis of the HST STIS archival spectra of the magnetic white dwarf in the Hyades eclipsing-spectroscopic, post-common envelope binary V471 Tauri, time resolved on the orbit and on the X-ray rotational phase of the magnetic white dwarf. An HST STIS spectrum obtained during primary eclipse reveals a host of transition region/chromospheric emission features including N V (1238, 1242), Si IV (1393, 1402), C IV (1548, 1550) and He II (1640). The spectroscopic characteristics and emission line fluxes of the transition region/chromosphere of the very active, rapidly rotating, K2V component of V471 Tauri, are compared with the emission characteristics of fast rotating K dwarfs in young open clusters. We have detected a number of absorption features associated with metals accreted onto the photosphere of the magnetic white dwarf from which we derive radial velocities. All of the absorption features are modulated on the 555s rotation period of the white dwarf with maximum line strength at rotational phase 0.0 when the primary magnetic accretion region is facing the observer. The photospheric absorption features show no clear evidence of Zeeman splitting and no evidence of a correlation between their variations in strength and orbital phase. We report clear evidence of a secondary accretion pole. We derive C and Si abundances from the Si IV and C III features. All other absorption lines are either interstellar or associated with a region above the white dwarf and/or with coronal mass ejection events illuminated as they pass in front of the white dwarf.

Interstellar polarization and grain alignment: the role of iron and silicon

We compiled the polarimetric data for a sample of lines of sight with known abundances of Mg, Si, and Fe. We correlated the degree of interstellar polarization $P$ and polarization efficiency (the ratio of $P$ to the colour excess $E(B-V)$ or extinction $A_V$) with dust phase abundances. We detect an anticorrelation between $P$ and the dust phase abundance of iron in non silicate - containing grains $< [\rm Fe(rest)/H > ]_\rm d$, a correlation between $P$ and the abundance of Si, and no correlation between $P/E(B-V)$ or $P/A_V$ and dust phase abundances. These findings can be explained if mainly the silicate grains aligned by the radiative mechanism are responsible for the observed interstellar linear polarization.

Suzaku study of the centrally brightened supernova remnant G272.2−3.2

In this work, the results from Suzaku observation of Galactic supernova remnant G272.2-3.2 are presented. Spectra of G272.2-3.2 are well fitted by a single-temperature variable abundances non-equilibrium ionization (VNEI) model with an electron temperature kTe \sim 0.77 keV, ionization timescale {\tau} \sim 6.5 \times 10^10 cm-3 s and absorbing column density NH \sim 1.1 \times 10^22 cm-2. We have detected enhanced abundances of Si, S, Ca, Fe and Ni in the center region indicating that the X-ray emission has ejecta origin. We estimated the electron density ne to be \sim0.48f^-1/2 cm-3, age \sim4300f^1/2 yr and the X-ray total mass Mx = 475f^1/2 M by taking the distance to be d=10 kpc. To understand the origin of the centrally-peaked X-ray emission of the remnant, we studied radial variations of the electron temperature and surface brightness. The relative abundances in the center region suggest that G272.2-3.2 is the result of a Type Ia supernova explosion.

The evaporite–coal transition: Chemical, mineralogical and organic composition of the Late Triassic Abu Ruweis Formation, NW Jordan—Reference type of the “Arabian Keuper”

The Abu Ruweis Formation, NW Jordan, was studied with regard to its chemical (major, minor elements, REE, S-, O-, C isotopes, organic chemistry), mineralogical compositions (rock-forming minerals), coal petrography (maceral analyses) and palynology (age determination and palaecosystem) for the evaporite–coal facies transition which is very rarely found. The palynomorphs point to a Late Triassic/Carnian age of formation. Strong evaporation in the series is demonstrated by the presence of dolomite, gypsum and celestite. Mg, Ca, F, Cl, S, Sr and Ba reflect the variation of evaporation during basin subsidence. A detrital influx is characterized by the abundance of Si, Ti, Al, Fe, Mn Ce, Co, Cr, V, Y and the (Zr+Rb)/Sr ratio. Salinity variation may be characterized by the fractionation of LREE (La) and HREE (Lu). The element triplet Zn, Cu and Pb offers a clue to the redox regime and supports the idea of mineralogical-based proximity indicators: Zn (Eh≪0)⇒Cu (Eh≤0)⇒Pb (Eh≤0). Oxygen isotope composition (δ18O −8.3 to −0.9‰) of the carbonate fraction resulted in uniform isotope formation temperatures near 50°C. Temperature data obtained during coal petrography yielded maximum paleotemperatures of 100°C for the black shale and about 70°C for the remaining coal samples that are likely to reflect hot brine activity in some parts of the basin. The carbon isotopic composition (δ13C −12.4 to −3.9‰) of the carbonate fractions indicates a biogenic 12C-enriched CO2 source, which probably was admixed to marine pore water bicarbonate (with δ13C near 0‰) during early diagenesis. The S isotope composition (sulfide fraction −28.9 to −24.0‰) is typical of sulfides formed in the course of bacterial reduction with some sulfate (sulfate fraction +7.5 to +11.6‰) resulted from later re-oxidation of the sulfides. Phosphate distribution is a measure for the aridity while high-sulfur contents in the coal-bearing sediments point to brackish or alkaline waters. The results of the organic chemistry are interpreted in terms of a bloom of algae which were preserved during dysaerobic conditions in the course of early diagenesis. Sesqui- and diterpenoids are most probably derived from precursor molecules abundant in leaf resins of conifers. Phenanthrene and its methylated analogues derived from combustion products of fossil fuels generated by wild fires. Among the maceral types, textinites A and B represent xylem features of tree trunks and the crassi-cutinite upper leaf cuticles. The data allow for a definition of a special geological setting called the “Arabian Keuper Facies”. This facies type is characterized by an evaporite–coal transition which translates into a geodynamic setting positioned between the fully marine “Alpine Triassic Facies” of the Tethyan Ocean where submarine brines were responsible for the Alpine-type MVT Pb–Zn deposits and the epicontinental “Germanic Keuper Facies” that lacks both hydrothermal activity and major marine incursions.

Synthesis of Zeolitic Material from Paper Sludge Ash Using Diatomite

Paper sludge ash (PSA) was partially converted into zeolites by reaction with 3 M NaOH solution at 90°C for 24 h. The PSA had a low abundance of Si and significant Ca content, due to the presence of calcite that was used as paper filler. Diatomite, which contains amorphous silica and dissolves easily in alkali solution, was mixed with the ash, and then added to the NaOH solution to increase its Si content during alkali reaction and thus synthesize zeolites with high cation exchange capacity (CEC). The original ash without addition of diatomite yielded hydroxysodalite with CEC ca. 0.5 mmol/g. Addition of diatomite to the ash yielded zeolite-P with a higher CEC (ca. 1 mmol/g). The observed concentrations of Si and Al in the solution during the reaction explain the crystallization of these two phases. The reaction products were tested for their adsorption capacity for nutrients from liquid fertilizer, such as K+, NH4+ and PO43−. The product with zeolite-P exhibits high ability to adsorb these nutrients from liquid fertilizer, which is desirable for application in soil improvement.