A New Method for Low‐Temperature Decomposition of Chromites and Dichromium Trioxide using Bromic Acid Evaluated by Chromium Isotope Measurements

In recent years, routine application of the stable isotope determination of chromium (Cr) in environmental and health protection research has led to the search for simpler chromite decomposition techniques. As the range of Cr isotope abundance ratios in nature is very narrow, conventional chromite decomposition techniques are no longer suitable, due to the relatively high risk of contamination during laboratory procedures. We have developed a protocol for the decomposition of chromites based on oxidation by bromic acid at room temperature. The procedure takes 15 d and requires two doses of bromic acid during the reaction period (day 1 and 8), due to the limited stability of the reagent. Chromium extracted by alkaline oxidative fusion and by bromic acid decomposition yielded statistically indistinguishable δ⁵³Cr values, measured by multi‐collector inductively coupled plasma‐mass spectrometry following addition of a ⁵⁰Cr‐⁵⁴Cr double‐spike.     

Megabenthic diversity patterns and community structure of the Blanes submarine canyon and adjacent slope in the Northwestern Mediterranean: a human overprint?

The composition and structure of megabenthic communities in the Blanes canyon and adjacent open margin (Northwestern Mediterranean) were studied. The aim was to assess the effect of the canyon and commercial fishing intensity on the community composition and structure of benthic megafauna by (i) describing the megabenthic community composition, (ii) quantifying faunal abundance and biomass and (iii) describing community structure with MDS analyses and biodiversity indices. The results are compared between three sites (canyon head, canyon wall and open margin) located between 435 m and 700 m. Samples were collected using a commercial bottom trawl between April 2003 and March 2004. These sites are exploited by the local fishing fleet that targets the rose shrimp Aristeus antennatus . A total of 131 megabenthic species were identified from the three sites, with fishes and decapod crustaceans being the most speciose, most abundant and of higher biomass. The species richness, abundance and biomass of non-crustacean invertebrates were low. There were no significant differences in total abundance and biomass between the three sites. However, community structure analysis suggests that the open margin community is significantly different from the canyon head and canyon wall, with a lower species richness, lower diversity and lower evenness. The open margin community also reflects a higher degree of disturbance compared to the two canyon habitats. The results indicate that there is a canyon effect on the community structure of benthic megafauna, but this may be modulated by differing fishing pressure, which adds an additional factor to margin heterogeneity.     

The border as an engine for mobility and spatial integration: A study of commuting in a Swedish–Norwegian context

The purpose of the study was to analyse how cross-border commuting differed from intranational commuting in Sweden, and how cross-border mobilities affected spatial integration. The authors analysed patterns and spatial flows of cross-border commuting by comparing them with characteristics of intranational commuting. In the article, they explore the assumption that the border constitutes an ‘engine’ for work-related mobility, which affects processes of spatial integration in cross-border areas. The empirical material comprised data from surveys of commuting from the Swedish county of Värmland to Norway and commuting within Värmland. The findings showed that cross-border commuting shared common features with intranational commuting, including how the frequency of commuting was dependent on distance. The motives for commuting differed, and the reasons for working in Norway were economic rather than professional. In terms of spatial integration, cross-border commuting was mainly one-directional, from Sweden to Norway, while leisure mobility and migration tended to be in the opposite direction. The authors conclude that the border region is characterised by integration through specialisation, which involves a permanent state of ‘transient’ mobility. Thus, a win-win situation can be distinguished, in which the border serves as a resource and an ‘engine’ for cross-border integration, mobility and economic activities.     

Air–Sea \mathrm{CO}_{2} Gas Transfer Velocity in a Shallow Estuary

The air–sea transfer velocity of $\mathrm{CO}_{2}\, (k_{\mathrm{CO}_{2}})$ was investigated in a shallow estuary in March to July 2012, using eddy-covariance measurements of $\mathrm{CO}_{2}$ fluxes and measured air–sea $\mathrm{CO}_{2}$ partial-pressure differences. A data evaluation method that eliminates data by nine rejection criteria in order to heighten parametrization certainty is proposed. We tested the data evaluation method by comparing two datasets: one derived using quality criteria related solely to the eddy-covariance method, and the other derived using quality criteria based on both eddy-covariance and cospectral peak methods. The best parametrization of transfer velocity normalized to a Schmidt number of 600 $(k_{600})$ was determined to be: $k_{600} = 0.3\,{U_{10}}^{2.5}$ where $U_{10}$ is the wind speed in m $\mathrm{s}^{-1}$ at 10 m; $k_{600}$ is based on $\mathrm{CO}_{2}$ fluxes calculated by the eddy-covariance method and including the cospectral peak method criteria. At low wind speeds, the transfer velocity in the shallow water estuary was lower than in other coastal waters, possibly a symptom of low tidal amplitude leading to low intensity water turbulence. High transfer velocities were recorded above wind speeds of 5 m $\mathrm{s}^{-1}$ , believed to be caused by early-breaking waves and the large fetch (6.5 km) of the estuary. These findings indicate that turbulence in both air and water influences the transfer velocity.     

Long-Term Evolution of FU Ori-Type Stars at Infrared Wavelengths

We investigated the brightness evolution of 5 FU Ori systems in the 1–200 μm wavelength range using observations from the Infrared Space Observatory, 2MASS and MSX data. The SEDs were compared with earlier ones derived from the IRAS photometry and ground-based observations around the epoch 1983. In three cases no difference was seen, in one object the near- and mid-infrared part of the spectrum became fainter by a factor of 2, and in the fifth case a marginal fading was observed. We study in detail the case of V1057 Cyg.     

Projected evolution of circulation types and their temperatures over Central Europe in climate models

The study deals with changes in large-scale atmospheric circulation (represented by circulation types) and associated surface air temperatures as projected in an ensemble of regional climate models (RCMs) from the ENSEMBLES project. We examine changes of circulation type frequencies and means of daily maximum and minimum temperatures within circulation types in individual seasons for two time slices of transient runs under the SRES A1B scenario (2021–2050 and 2071–2100) with respect to the control period (1961–1990). To study the influence of driving data, simulations of the driving general circulation models (GCMs) also are evaluated. We find that all models project changes of atmospheric circulation that are statistically significant for both future time slices. The models tend to project strengthening of the westerly circulation in winter and its weakening in summer. We show that increases of daily maximum and minimum temperatures in all seasons differ for individual circulation types. There are, however, only few features of the projected changes in the future circulation–temperature links that are common among the models, in particular relatively smaller warming for westerly types. Only in winter, projected changes in circulation types tend to contribute to the projected overall warming. This effect is negligible and mostly opposite in the other seasons. We also detect a strong influence of driving data on RCMs’ simulation of atmospheric circulation and temperature changes.     

A closing Ligurian Sea?

Two earthquakes occurred in the Ligurian Sea in December 1989 and April 1990. Both were widely felt along the French and Italian Rivieras, thus reminding us of the seismic risk in this region. The significant increase in the number of seismic stations in the area facilitated the study of these two shocks and their related aftershocks. Using different techniques (absolute and relative hypocentral locations, doublet analysis and waveform modeling), we computed accurate hypocentral locations and estimated the location-error range for earthquakes in this area. We also computed the focal mechanisms for both mainshocks, and we present here a synthesis that integrates previous data. The reactivation in compression of the Ligurian Sea sphenochasm is confirmed, which would eventually result in the closing of an aborted oceanic domain. As the seismic activity is clearly restricted to the northern margin, we suggest it locally results from the lateral expulsion of the south-western Alps along the Apulian indenter.     

Accuracy of Laser Ablation U-Pb Zircon Dating: Results from a Test Using Five Different Reference Zircons

Using a state‐of‐the‐art 193 nm‐LA‐MC‐ICP‐MS system and with careful control of analytical procedures, the long term external reproducibility and accuracy of the ages Phanerozoic zircons measured over a period of months using calibrator bracketing for the ²⁰⁶Pb/²³⁸U and ²⁰⁷Pb/²⁰⁶Pb ages were ca. 1% (2 RSD) if a single reference zircon was used for the matrix‐matched calibration. When different reference zircons were used for the calibration, suspicious systematic shifts in the obtained ages were observed and thus a reduction in the overall accuracy of the dating method became obvious. Such shifts were within a few percent range of the U‐Pb and Pb/Pb ages and seemed to vary independently of zircon age and composition. A “test of accuracy” experiment was conducted reducing instrumental effects as far as possible by analysing five different reference zircons mounted on a single mount eight times during the same session. An identical protocol was used for all analyses, with unchanged instrument parameters and with ion beam intensities kept as identical as possible. For data reduction, every zircon served consecutively as the reference zircon for calibration, with the others in the batch treated as unknowns. The known reference age and the four calculated ages obtained using the four other RMs for calibration were then compared. Even using such a strict analytical protocol, shifts in ²⁰⁶Pb/²³⁸U, ²⁰⁷Pb/²³⁵U and ²⁰⁷Pb/²⁰⁶Pb ratios were still present. They varied non‐systematically and ranged from ?4.35% to 3.08% for the investigated age range (1065 Ma to 226 Ma). Assuming the absence of instrumental effects (i.e., memory, dead‐time correction, non‐linearity of ion counters and interdetector calibration, crystallographic orientation, ablation cell geometry and setup, gas flows), the observed shifts were attributed to matrix and/or ablation related effects. It is proposed that non‐spectral matrix effects in the Ar plasma torch resulted in non‐uniform signal enhancement (or depression?) leading to shifts both in elemental and Pb isotopic ratios. Additionally, the ablated particle size distribution could be an important factor controlling plasma conditions and thus mass bias and fractionation. Until such effects are well understood and controlled, it would seem that any LA‐ICP‐MS zircon U‐Pb and ²⁰⁷Pb/²⁰⁶Pb age determination cannot be meaningfully interpreted at below a ca. 3% to 4% (2 RSD) confidence level.