On the breakdown of zircon upon “dry” thermal annealing

Zircon samples without and with secondary chemical alteration from diverse sources were subjected to heat treatment at 1400 °C for 96 h. Resulting new phases and textures suggest that decomposition of zircon into component oxides occurred in all experiments to various degrees. The crucible material was found to have a strong influence on the extent of breakdown, especially in the case of altered starting materials. In this study the progressive stages of the breakdown of zircon grains are described. The factors that may govern the decomposition are discussed, including radiation damage, secondary alteration and external reaction conditions (sample container, atmosphere). Alumina crucibles should generally be avoided in dry annealing of zircon, to minimise uncontrolled breakdown into oxides.     

LA-ICP-MS heavy metal analyses of fish scales from sediments of the Oxbow Lake Certak of the Morava River (Czech Republic)

Heavy metal concentrations were studied in the scales of recent and subrecent (2–25 years old) fish buried in the oxbow lake sediments of the Morava River. The samples were taken from two cores up to 4-m deep and analysed using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and an electron microprobe analysis (EMPA). The results were compared with heavy metal concentrations of bulk samples of the embedding sediment. The study has revealed substantial differences in heavy metal contents existing between the recent and subrecent fish scales documenting an extreme rapidity of the diagenesis/fossilization processes. The most apparent features of the early fossilization include the quick loss of the mucous envelope, collagen and magnesium and an enormous increase in the heavy metal concentrations in particular iron, which is connected with a colour change. The variations in heavy metal contents in fish scales within a sample are attributed to variations in heavy metal content in the environment and variable amounts of organic matter in the embedding sediment. In contrast to the contamination of the embedding sediment, no general increase in heavy metal concentrations in fish scales was observed down to the cores. It is inferred that the rapid sorption stabilizes the biologic hydroxyapatite of the fish scales, which thus rapidly attain a thermodynamic equilibrium with the embedding water-saturated sediment. The results show that the processes of sorption, fossilization and stabilization of hydroxyapatite can act very quickly over a time scale of several years and represent thus a great advantage in the preservation of the original signals of the ancient environments.     

Investigation of a large collapse sinkhole affecting a multi-storey building by means of geophysics and the trenching technique (Zaragoza city,NE Spain)

An active sinkhole around 100 m long has been investigated in the city of Zaragoza (NE Spain). Subsidence activity on this depression, including the sudden occurrence of a collapse sinkhole 5 m across, led to the abandonment of a factory in the 1990s. At the present time, a building with 100 flats and shallow pad foundations partially built on the sinkhole, is affected by rapid differential settlement. The development of the sinkhole results from the karstification of the halite- and glauberite- bearing bedrock and the sagging and collapse of the overlying bedrock and alluvium, more than 30 m thick. GPR and electrical resistivity profiles have provided information on the distribution and geometry of the subsidence structure. The application of the trenching technique and geochronological methods (AMS and OSL dating) has allowed us to infer objective and practical data on the sinkhole including (1) Limits of the subsidence structure, (2) subsidence mechanisms, (3) cumulative subsidence (>408 cm), (4) subsidence rates on specific failure planes (>1.8 cm/year), (5) episodic displacement regime of some fault planes. The available information indicates that the progressive deformation recorded in the building will continue and might be punctuated by events of more rapid displacement. This work illustrates the practicality of the trenching technique for the study of sinkholes in mantled karst areas.     

Mercury enrichments in core sediments in Hugli–Matla–Bidyadhari estuarine complex,north-eastern part of the Bay of Bengal and their ecotoxicological significance

Mercury concentrations (Hg_T) in fine-grained fraction (<63 μm) of core sediments of the Hugli–Matla–Bidyadhari estuarine complex, India were analyzed. Results revealed a wide range of spatial variations (<4–93 ng g⁻¹ dry weight) with a definite enhancement level at the lower stretch of the estuarine complex infested with mangrove plants, which might act as a sink to Hg_T. An elevated concentration of Hg was encountered in surface/subsurface layer of the core in majority of the cases resulting from physical, biogenic and postdepositional diagenetic processes that remobilized and resuspended the metal from deeper sediments. A strong positive correlation was observed between the Hg and clay fraction content of the sediments, while the correlations of Hg with Al, Fe and Mn were poor. Based on the index of geoaccumulation (I _geo) and effects range-low (ER-L) value, it is considered that the sediments are less polluted and thus there is less chance of ecotoxicological risk to organisms living in sediments.     

Fitting the integrated spectral energy distributions of galaxies

Fitting the spectral energy distributions (SEDs) of galaxies is an almost universally used technique that has matured significantly in the last decade. Model predictions and fitting procedures have improved significantly over this time, attempting to keep up with the vastly increased volume and quality of available data. We review here the field of SED fitting, describing the modelling of ultraviolet to infrared galaxy SEDs, the creation of multiwavelength data sets, and the methods used to fit model SEDs to observed galaxy data sets. We touch upon the achievements and challenges in the major ingredients of SED fitting, with a special emphasis on describing the interplay between the quality of the available data, the quality of the available models, and the best fitting technique to use in order to obtain a realistic measurement as well as realistic uncertainties. We conclude that SED fitting can be used effectively to derive a range of physical properties of galaxies, such as redshift, stellar masses, star formation rates, dust masses, and metallicities, with care taken not to over-interpret the available data. Yet there still exist many issues such as estimating the age of the oldest stars in a galaxy, finer details of dust properties and dust-star geometry, and the influences of poorly understood, luminous stellar types and phases. The challenge for the coming years will be to improve both the models and the observational data sets to resolve these uncertainties. The present review will be made available on an interactive, moderated web page (), where the community can access and change the text. The intention is to expand the text and keep it up to date over the coming years.     

Laboratory studies on the sputtering contribution to the sodium atmospheres of Mercury and the Moon

To ascertain the importance of sputtering by solar wind ions on the formation of a sodium exosphere around Mercury and the Moon, we have irradiated with 4 keV He ions, the Na bearing tectosilicates: albite, labradorite, and anorthoclase, as well as adsorbed Na layers deposited on albite and on olivine (a neosilicate that does not contain Na). Sodium at the surface and near surface (<40 Å) was quantified with X-ray photoelectron spectroscopy before and after each irradiation to determine the depletion cross section. We measured a cross section for sputtering of Na adsorbed on mineral surfaces, σ_s ≈ 1 × 10^?15 cm² atom^?1. In addition, mass spectrometric analyses of the sputtered flux show that a large fraction of the Na is sputtered as ions rather than as neutral atoms. These results have strong implications for modeling the sodium population within the mercurian and the lunar exospheres.     

An indurated Pleistocene coastal barrier on the inner shelf of the Gulf of Valencia (western Mediterranean): evidence for a prolonged relative sea-level stillstand

The objective of this study is to document and interpret a recently discovered carbonate-cemented coastal barrier on the inner shelf of the Gulf of Valencia (western Mediterranean Sea). The coastal barrier was identified in a high-resolution digital bathymetric model based on a cartographic survey of the study area using a multibeam echosounder. Moreover, radiocarbon dating and petrographic analyses were performed on a rock sample recovered from the seabed. The data reveal the submerged coastal barrier to be approx. 1.7 km wide and 70 km long, and incised by channels of various dimensions. Aligned more or less parallel to the modern coastline, it is interpreted as corresponding to the shoreline of a former sea-level stillstand. The barrier and lagoon system became stranded above sea level in the course of a subsequent forced regression, which also caused the incision of the river courses. Age dating of the cemented rock suggests that the fossil coastal barrier most probably formed during the prolonged Tyrrhenian (Eemian) sea-level highstand, induration taking place by carbonate cementation at the contact between freshwater and seawater (beach-rock formation). The fact that the fossil barrier is today submerged below modern sea level is explained by the sustained subsidence affecting the region.     

Evaluation of the presence of major anionic surfactants in marine sediments

The contamination of aquatic environments has become the focus of increasing regulation and public concern due to their potential and unknown negative effects on the ecosystems. The present work develops a monitoring and statistical study, based on the analysis of variance test (ANOVA) and the multivariable analysis, both for insoluble soap and LAS in order to compare the behavior of different anionic surfactants in this environmental compartment. First, a novel and successfully validated methodology to analyze insoluble soap in these samples is developed. The matrix effect and the comparison of different extraction techniques were also performed. The optimized analytical methodologies were applied to 48 representative samples collected from the Almeria Coast (Spain) and then a statistical analysis to correlate anionic surfactant concentration and several variables associated with marine sediment samples was also developed. The results obtained showed relevant conclusions related to the environmental behavior of anionic surfactants in marine sediments.     

Joint inversion of teleseismic P waveforms and surface-wave group velocities from ambient seismic noise in the Bohemian Massif

Joint inversion of teleseismic P-waveforms and local group velocities of surface waves retrieved from ambient seismic noise has been performed to model velocity structure of the crust and uppermost mantle of the Bohemian Massif. We analysed P-waveforms of 381 teleseismic earthquakes recorded at 54 broadband seismic stations located on the territory of the Czech Republic and in its close surroundings. Group velocities of Rayleigh and Love surface waves were obtained by cross-correlating long-term recordings of seismic noise. The basis for waveform inversion is the well-known methodology of P-to-S receiver functions constructed from converted phases. Due to instabilities in direct inversion of receiver functions caused by the necessity of applying deconvolution, we propose an alternative formulation to fit observed and calculated radial components of P waveforms. The joint inversion is transformed into a search for the minimum of the cost function defined as a weighted sum of waveform and group velocity misfits. With the use of the robust stochastic optimizer (Differential Evolution Algorithm), neither derivatives nor a starting model are needed. The task was solved for 1D layered isotropic models of the crust and the uppermost mantle. We have performed a sequence of inversions with models containing one, two, three and four layers above a half-space. By using statistical criteria (F-test) we were able to select the simplest velocity models satisfying data and representing local geological structures. Complex crustal models are typical for stations located close to boundaries of major tectonic units. The relatively low average P to S wave-velocity ratio is in agreement with the generally accepted view that the BM crust is predominantly felsic.