A seasonal climate model of the atmospheres of the giant planets at the voyager encounter time: I. Saturn's stratosphere

A radiative seasonal model which incorporates a multilayer radiative transfer treatment at wave-lengths longward of 7 μm is presented and applied to Saturn's stratosphere. Opacities due to H₂-He, CH₄, C₂H₂, and C₂H₆ are included. Season-dependent insolation is shown to produce a strong hemispheric asymmetry decreasing with depth at the Voyager encounter times, and seasonal amplitudes of 30°K at the poles are predicted in the high stratosphere. The ring-modulated dependence of the insolation and the orbital eccentricity are shown to have a significant effect. Calculations agree closely with the Voyager 1 and 2 radio occultation ingress profiles recorded at 76°S and 36.5°S for CH₄/H₂ = 3.5 + 1.4/? 1.0 × 10^?3;the estimated errors include modeling systematic errors and uncertainties in the occultations profiles. The possible role of aerosols in the stratospheric heating is analyzed. The Voyager 2 egress profile recorded at 31°S cannot be reproduced by calculations. Some constraints on the C₂H₂ and C₂H₆ abundances are derived. The upper portion of the occultation profiles (p < 3mbar) can be matched for C₂H₂/H₂ = 1.0 + 1.3/?0.6 × 10^?7, C₂H₆/H₂ = 1.5 + 1.8/?0.9 × 10^?6 at 76°S and C₂H₂/H₂ = 4 + 6/?4 × 10^?8, C₂H₆/H₂ = 6 + 9/?6 × 10^?7 at 36.5°N. At the northern occultation latitude, the discrepancy with the concentrations derived from analysis of IRIS spectra by R. Courtin, D. Gautier, A. Marten, B. Bézard, and R. Hanel (1984, Astrophys. J.287) can be explained by a sharp variation of the mixing ratios of these gases with altitude in the upper stratosphere. Other interpretations are discussed.     

SARG: The High Resolution Spectrograph of TNG

SARG is a cross dispersed echelle spectrograph in operation since late spring 2000 at the Italian Telescopio Nazionale Galileo (TNG) 3.5 m telescope, La Palma. SARG offers both single object and long slit (up to 26 arcsec) observing modes covering a spectral range from λ = 0.37 up to1 μm, with resolution ranging from R = 29,000 up to R = 164,000. Cross dispersion is provided by means of a selection of four grisms; interference filters may be used for the long slit mode (up to 26 arcsec). A dioptric camera images the cross dispersed spectra onto a mosaic of two 2048 × 4096 EEV CCDs (pixel size: 13.5 μm) allowing complete spectral coverage at all resolving power for λ < 0.8 μm. In order to reach a high wavelength calibration precision an iodine-absorbing cell is provided. A Distributed Active Temperature Control System (DATCS) maintains constant the temperature of all spectrograph components at a preset value. Early results show that SARG works according to original specifications in terms of wavelength coverage, efficiency (measured peak efficiency is about 13%),resolution (maximum resolution R = 164,000 using a 0.3 arcsec slit, R ∼144,000 using an image slicer), and stability (preliminary estimates of radial velocity accuracy is ∼3 m/s using the iodine cell and ±150 m/s without the iodine cell). This revised version was published online in July 2006 with corrections to the Cover Date.     

Chaotic Diffusion And Effective Stability of Jupiter Trojans

It has recently been shown that Jupiter Trojans may exhibit chaotic behavior, a fact that has put in question their presumed long term stability. Previous numerical results suggest a slow dispersion of the Trojan swarms, but the extent of the ‘effective’ stability region in orbital elements space is still an open problem. In this paper, we tackle this problem by means of extensive numerical integrations. First, a set of 3,200 fictitious objects and 667 numbered Trojans is integrated for 4 Myrs and their Lyapunov time, T_L, is estimated. The ones following chaotic orbits are then integrated for 1 Gyr, or until they escape from the Trojan region. The results of these experiments are presented in the form of maps of T_Land the escape time, T_E, in the space of proper elements. An effective stability region for 1 Gyr is defined on these maps, in which chaotic orbits also exist. The distribution of the numbered Trojans follows closely the T_E=1 Gyr level curve, with 86% of the bodies lying inside and 14% outside the stability region. This result is confirmed by a 4.5 Gyr integration of the 246 chaotic numbered Trojans, which showed that 17% of the numbered Trojans are unstable over the age of the solar system. We show that the size distributions of the stable and unstable populations are nearly identical. Thus, the existence of unstable bodies should not be the result of a size-dependent transport mechanism but, rather, the result of chaotic diffusion. Finally, in the large chaotic region that surrounds the stability zone, a statistical correlation between T_LandT_E is found.     

Palynological evidence for Lower Ordovician rocks (Tremadoc and Àrenig) in the Northern Greywacke Zone (Eastern Alps)

Until recently, only fossils of Caradoc to Carboniferous age have been reported from the Northern Greywacke Zone/Eastern Alps. New medium-preserved and diversified acritarch assemblages from the Lower Wildschönau Formation indicate a Lower Ordovician (Tremadoc and Arenig) age. These fossil spectra define a well-constrained time interval for a lower section of the Northern Greywacke Zone for the first time.     

Late Hercynian–Mesozoic thinning in the Alboran domain: metamorphic data from the northern Rif, Morocco

In the Alboran domain, two crustal-thickening late-orogenic extension cycles are superposed. The importance of the late Alpine thinning of the Alpujarride-Sebtide crustal section on top of the Beni Bousera peridotites is discussed here in metamorphic petrological terms. The Alpine metamorphism operated first under a HP–LT gradient, and reached the eclogite facies in the Permian–Triassic phyllites, before retrogression under a high geothermal gradient. A contrasting, higher temperature metamorphism characterizes the pre-Permian section, reaching the HP-granulite facies at the bottom of the crustal section. By reference to the western European setting, the granulites relate to the Hercynian orogeny, as supported by the isotopic ages of the enclosed, armoured monazite crystals. Thus, thinning of an overthickened crust might have occurred there during the late Hercynian extension and Tethyan opening, before being reactivated during the late Oligocene.     

Development and morphometry of sinkholes in coastal plains of Apulia, southern Italy. Preliminary sinkhole susceptibility assessment

Evolution of coastlines in karst areas may be strongly controlled by dissolution processes which favour the development of surface and subsurface landforms. The generation of caves in these environments is commonly favoured by the mixing between fresh and brackish waters. The sinkholes resulting from the upward propagation of the caves may interfere with the anthropogenic environment and cause damage to human elements (property and activities). To highlight the often underestimated importance of karst phenomena in coastal areas, we have analyzed a coastal stretch of Apulia, in southern Italy. The study area, covering an extension of about 6 km², is situated in the Ionian coast, and presents several interesting karst landforms that are generally connected to caves. Tens of sinkholes were mapped through field surveys, multi-year aerial-photographs (dating back to the 1940s) and archival research. We have performed a morphometric analysis of the sinkholes. The analysis describes the main parameters of the sinkholes (area, length, width, and depth), and the control exerted by the main discontinuity systems in the area. The detrimental effects derived from interaction between human environment and these karst landforms is also under consideration. A sinkhole susceptibility map, which may provide useful information for planners, developers and the insurance industry has eventually been produced through application of a decision tree model.     

Formation of Zn–Ca phyllomanganate nanoparticles in grass roots

It is now well established that a number of terrestrial and aquatic microorganisms have the capacity to oxidize and precipitate Mn as phyllomanganate. However, this biomineralization has never been shown to occur in plant tissues, nor has the structure of a natural Mn(IV) biooxide been characterized in detail. We show that the graminaceous plant Festuca rubra (red fescue) produces a Zn-rich phyllomanganate with constant Zn:Mn and Ca:Mn atomic ratios (0.46 and 0.38, respectively) when grown on a contaminated sediment. This new phase is so far the Zn-richest manganate known to form in nature (chalcophanite has a Zn:Mn ratio of 0.33) and has no synthetic equivalent. Visual examination of root fragments under a microscope shows black precipitates about ten to several tens of microns in size, and their imaging with backscattered and secondary electrons demonstrates that they are located in the root epidermis. In situ measurements by Mn and Zn K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy and X-ray diffraction (XRD) with a micro-focused beam can be quantitatively described by a single-phase model consisting of Mn(IV) octahedral layers with 22% vacant sites capped with tetrahedral and octahedral Zn in proportions of 3:1. The layer charge deficit is also partly balanced by interlayer Mn and Ca. Diffracting crystallites have a domain radius of 33 Å in the ab plane and contain only 1.2 layers (8.6 Å) on average. Since this biogenic Mn oxide consists mostly of isolated layers, basal 00l reflections are essentially absent despite its lamellar structure. Individual Mn layers are probably held together in the Mn–Zn precipitates by stabilizing organic molecules. Zinc biomineralization by plants likely is a defense mechanism against toxicity induced by excess concentrations of this metal in the rhizosphere.     

Effectiveness of sulfate-reducing passive bioreactors for treating highly contaminated acid mine drainage: I. Effect of hydraulic retention time

Sulfate-reducing passive bioreactors have proved to be an effective technology for the treatment of acid mine drainage (AMD) contaminated waters over relatively short periods of time (1–5 a). However, long-term efficiency can be limited by several factors including problems related to the hydraulic properties of the reactive mixture. In this study, the effect of two hydraulic retention times (HRTs) of 7.3 d and 10 d on the performance of passive bioreactors was evaluated over an 11-month period for the treatment of a highly contaminated AMD. Evolution of the porosity and hydraulic conductivity of the reactive mixture was also evaluated during the 15-month operation of two bioreactors. Results indicated that bioreactors were effective at both HRTs for increasing the pH and alkalinity of contaminated water and for SO₄ and metal removal (60–82% for Fe and up to 99.9% for Cd, Ni and Zn). Although the quality of treated effluent was significantly improved with the 10 d HRT compared to the 7.3 d HRT, results showed that the higher HRT reduced the porosity and the permeability of the reactive mixture which might lead to hydraulic related problems and, eventually, to limited efficiency in long-term operation compared to a shorter HRT. The choice of HRT for a passive bioreactor must therefore consider both the desired quality of treated effluent and the potential for deterioration of hydraulic properties in the reactive mixture.     

Effectiveness of sulfate-reducing passive bioreactors for treating highly contaminated acid mine drainage: II. Metal removal mechanisms and potential mobility

Column bioreactors were used for studying mechanisms of metal removal, assessment of long-term stability of spent reactive mixtures, as well as potential metal mobility after treating highly contaminated acid mine drainage (AMD; pH 2.9–5.7). Several physicochemical, microbiological, and mineralogical analyses were performed on spent reactive mixtures collected from 4 bioreactors, which were tested in duplicate for two hydraulic retention times (7.3d and 10d), with downward flow over an 11-month period. Consistent with the high metal concentrations in the AMD feed, and with low metal concentrations measured in the treated effluent, the physicochemical analyses indicated very high concentrations of metals (Fe, Mn, Cd, Ni, and Zn) in the top and bottom layers of the reactive mixtures from all columns. Moreover, the concentrations of Fe (50.8–57.8 g/kg) and Mn (0.53–0.70 g/kg) were up to twice as high in the bottom layers, whereas the concentrations of Cd (6.77–13.3 g/kg), Ni (1.80–5.19 g/kg) and Zn (2.53–13.2 g/kg) were up to 50-times higher in the top layers. Chemical extractions and elemental analysis gave consistent results, which indicated a low fraction of metals removed as sulfides (up to 15% of total metals recovered in spent reactive mixtures). Moreover, Fe and Mn were found in a more stable chemical form (residual fraction was 42–74% for Mn and 30–77% for Fe) relative to Cd, Ni or Zn, which seemed more weakly bound (oxidisable/reducible fractions) and showed higher potential mobility. Besides identifying (oxy)hydroxide and carbonate minerals, the mineralogical analyses identified metal sulfides containing Fe, Cd, Ni and Zn. Metal removal mechanisms were, therefore, mainly adsorption and other binding mechanisms with organic matter (for Cd, Ni and Zn), and the precipitation as (oxy)hydroxide minerals (for Fe and Mn). After 15 months, however, the column bioreactors did not lose their capacity for removing metals from the AMD. Although the metals were immobile during the bioreactor treatment, their mobility could increase from spent reactive mixtures, if stored inappropriately. Metal recovery by acidic leaching of spent substrates at the end of bioreactor operation could be an alternative.     

Baryt und ankerit aus Ammoniten des Berner Juras (Schweiz)

Barite has been found for the first time in the Swiss Jura (Hirni, Passwang). Small, white crystals of barite with yellow ankerite grow on calcite in different chambers of a Bajocian ammonite. Chemical data (by microprobe analysis) and lattice parameters (refined by leastsquares from powder patterns) are given for the two minerals. There is a distinct correlation between the cell dimensions and the chemical composition for both of them. The genesis is discussed.