The influence of Fe(II) competition on the sorption and migration of Ni(II) in MX-80 bentonite

The results from batch sorption experiments on montmorillonite systems have demonstrated that bivalent transition metals compete with one another for sorption sites. For safety analysis studies of high level radioactive waste repositories with compacted bentonite near fields, the importance of competitive sorption on the migration of radionuclides needs to be evaluated. Under reducing conditions, the bentonite porewater chosen has a Fe(II) concentration of ∼5.3 × 10⁻⁵ M through saturation with siderite. The purpose of this paper is to assess the influence of such high Fe(II) concentrations on the transport of Ni(II) through compacted bentonite, Ni(II) was chosen as an example of a bivalent transition metal. The one-dimensional calculations were carried out at different Ni(II) equilibrium concentrations at the boundary (Ni(II)_EQBM) with the reactive transport code MCOTAC incorporating the two site protolysis non electrostatic surface complexation/cation exchange sorption model, MCOTAC-sorb. At a Ni(II)_EQBM level of 10⁻⁷ M without Fe(II) competition, the reactive transport calculations using a constant K_d approach and the MCOTAC-sorb calculation yielded the same breakthrough curves. At higher Ni(II)_EQBM (10⁻⁵ M), the model calculations with MCOTAC-sorb indicated a breakthrough which was shifted to later times by a factor of ∼5 compared with the use of the constant K_d approach.When sorption competition was included in the calculations, the magnitude of the influence depended on the sorption characteristics of the two competing sorbates and their respective concentrations. At background Fe(II) concentrations of 5.3 × 10⁻⁵ M, and a Ni(II)_EQBM level of 10⁻⁷ M, the Ni(II) breakthrough time was ∼15 times earlier than in the absence of competition. At such Fe(II) concentrations the Ni(II) breakthrough curves at all source concentrations less than 3.5 × 10⁻⁵ M (fixed by the NiCO_3,S solubility limit) are the same i.e. Ni(II) exhibits linear (low) sorption.Competitive sorption effects can have significant influences on the transport of radionuclides through compacted bentonite i.e. reduce the migration rates. Since, for the case considered here, the Fe(II) concentration in the near field of a high-level radioactive waste repository may change in time and space, the transport of bivalent transition metal radionuclides can only be properly modelled using a multi-species reactive transport code which includes a sorption model.     

Broad-band calibration of marine seismic sources used by R/V Polarstern for academic research in polar regions

Air guns and air-gun arrays of different volumes are used for scientific seismic surveys with R/V Polarstern in polar regions. To assess the potential risk of these research activities on marine mammal populations, knowledge of the sound pressure field of the seismic sources is essential. Therefore, a broad-band (0–80 kHz) calibration study was conducted at the Heggernes Acoustic Range, Norway. A GI (2.4 l), a G (8.5 l) and a Bolt gun (32.8 l) were deployed as single sources, 3 GI (7.4 l), 3 G (25.6 l) and 8 VLF™ Prakla-Seismos air guns (24.0 l) as arrays. Each configuration was fired along a line of 3–4 km length running between two hydrophone chains with receivers in 35, 100, 198 and 263 m depth. Peak-to-peak, zero-to-peak, rms and sound exposure levels (SEL) were analysed as functions of range. They show the typical dipole-like directivity of marine seismic sources with amplitude cancellation close to the sea surface, higher amplitudes in greater depths, and sound pressure levels which continuously decrease with range. Levels recorded during the approach are lower than during the departure indicating a shadowing effect of Polarsterns's hull. Backcalculated zero-to-peak source levels range from 224–240 dB re 1 μPa @ 1 m. Spectral source levels are highest below 100 Hz and amount to 182–194 dB re 1 μPa Hz^–1. They drop off continuously with range and frequency. At 1 kHz they are ∼30 dB, at 80 kHz ∼60 dB lower than the peak level. Above 1 kHz amplitude spectra are dominated by Polarstern's self-noise. From the rms and sound exposure levels of the deepest hydrophone radii for different thresholds are derived. For a 180 dB rms-level threshold radii maximally vary between 200 and 600 m, for a 186 dB SEL threshold between 50 and 300 m.     

Anomalous Diffuse CO2 Emissions at the Masaya Volcano (Nicaragua) Related to Seismic-Volcanic Unrest

Anomalous changes in the diffuse emission of carbon dioxide within the Masaya caldera have been observed before two seismic events that occurred at 10 and 30 km from the observation site. Their epicenters are located, respectively, south of Managua in Las Colinas (4.3 magnitude) and the Xiloa caldera (3.6 magnitude), in 2002 and 2003, recorded by the geochemical station located at El Comalito, Masaya volcano (Nicaragua). Anomalous increases were observed, which occurred around 50 and 8 days before the main seismic event that took place in Las Colinas, and 4 days before the seismic swarm at the Xiloa caldera, with a maximum CO₂ efflux of 9.3 and 10.7 kg m^?2 day^?1, respectively. The anomalous CO₂ efflux increases remained after filtering with multiple regression analysis was applied to the CO₂ efflux time series, which indicated that atmospheric variables, during the first 4 months, explained 23 % CO₂ variability, whereas, during the rest of the time series, CO₂ efflux values are poorly controlled with only 6 %. The observed anomalies of the diffuse CO₂ emission rate might be related to pressure changes within the volcanic–hydrothermal system and/or to geostructural changes in the crust due to stress/strain changes caused before and during the earthquakes’ formation, and seem not to be related to the activity of the main crater of Masaya volcano.     

An integrated socio-environmental framework for glacier hazard management and climate change adaptation: lessons from Lake 513, Cordillera Blanca, Peru

Glacier hazards threaten societies in mountain regions worldwide. Glacial lake outburst floods (GLOFs) pose risks to exposed and vulnerable populations and can be linked in part to long-term post-Little Ice Age climate change because precariously dammed glacial lakes sometimes formed as glaciers generally retreated after the mid-1800s. This paper provides an interdisciplinary and historical analysis of 40?years of glacier hazard management on Mount Hualcán, at glacial Lake 513, and in the city of Carhuaz in Peru’s Cordillera Blanca mountain range. The case study examines attempted hazard zoning, glacial lake evolution and monitoring, and emergency engineering projects to drain Lake 513. It also analyzes the 11 April 2010 Hualcán rock-ice avalanche that triggered a Lake 513 GLOF; we offer both a scientific assessment of the possible role of temperature on slope stability and a GIS spatial analysis of human impacts. Qualitative historical analysis of glacier hazard management since 1970 allows us to identify and explain why certain actions and policies to reduce risk were implemented or omitted. We extrapolate these case-specific variables to generate a broader socio-environmental framework identifying factors that can facilitate or impede disaster risk reduction and climate change adaptation. Facilitating factors are technical capacity, disaster events with visible hazards, institutional support, committed individuals, and international involvement. Impediments include divergent risk perceptions, imposed government policies, institutional instability, knowledge disparities, and invisible hazards. This framework emerges from an empirical analysis of a coupled social-ecological system and offers a holistic approach for integrating disaster risk reduction and climate change adaptation.     

Spurenelemente in den Unterrotliegend-Sedimenten der Saar-Nahe-Senke

Zusammenfassung Die Schichten des Unterrotliegenden wurden im Raum Kusel auf ihre Spurenelementführung untersucht. Es ergab sich für einige Elemente eine Abhängigkeit der Gehalte von der petrographischen Ausbildung der Sedimente. Eine stratigraphische Gliederung mit Hilfe der Geochemie war nicht möglich. Ein 10 km im Streichen verfolgbarer bituminöser Schieferton zeigte Anreicherungen von U, Cu, Mo, V. Eine Uranvererzung in Kohlen der Wahnweger Schichten konnte als epigenetisch deszendent bestimmt werden.

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The contents of trace elements in Unterrotliegend sediments have been investigated in the area of Kusel. The amount of some trace elements depended on petrographic composition of the sediments. The results of geochemical research did not show any correlation to stratigraphy. A bituminous shale extending about 7 miles showed enrichment of U, Cu, Mo, V. A mineralisation of uranium in coal seams could be proved as epigenetically descendent.

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Résumé Les sédiments de l'Unterrotliegende dans la région de la ville de Kusel sont examinés pour leurs éléments en traces. Certains éléments dépendent de la composition pétrographique des sédirnents, mais la géochimie ne permet pas une classification stratigraphique. Des schistes bitumineux sont enrichis en U, Cu, Mo et V sur une dizaine de km. La minéralisation en uranium d'une couche de charbon apparaît comme épigénétique et descendante.

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The computation of the free barotropic oscillations of a global ocean model including friction and loading effects

A set of 61 normal modes with periods between 7.8 and 133.1 h has been calculated, using a 1° model of the global ocean, including the Arctic Ocean. The model explicitly considers frictional forces and ocean self-attraction and loading effects. The latter effects have generally been taken into account by parameterization, but for some modes the effects have also been considered fully. Due to friction, the computed eigenfrequencies are complex, exhibiting also the varying dissipative properties of the modes and their dependence on the distribution of potential and kinetic energies over the oceanic regions. In detail, gravity modes having periods less then 80 h and dominating the semi-diurnal and the diurnal tides, topographically controlled vorticity modes with periods longer than diurnal, and two planetary vorticity modes with periods of 96.8 and 119.4 h have been identified. These planetary vorticity modes have their energies distributed over Pacific, Atlantic, and Indian Oceans, while the other modes with periods longer than 80 h, as vorticity modes, have their energies concentrated on topographic structures of restricted extension. The modes are discussed with respect to their wave properties, e.g., concerning quasi-standing-wave resonances and to the appearance of Kelvin waves of different orders and trapped by different coastlines. In particular, the relevance of specific modes for the development of the fields of the most important semi-diurnal and diurnal tidal constituents is investigated.