Water transport in planetary ice shells by two-phase flow – a parametric study

We present a two-phase model for the generation of meltwater and its propagation through the outer shells of icy satellites such as Europa, Enceladus or Titan. We exploit the analogy with the process of partial melt generation in the Earth’s interior by adopting the formalism of two-phase flow developed in the mantle-dynamics community, and by means of scaling analysis we derive a reduced system appropriate for our planetary application. The resultant system couples Darcy’s law with the deformation of the viscous ice matrix. We numerically investigate the system in a simplified one-dimensional geometry, corresponding to a laterally uniform ice layer, and analyze the role of various physical parameters. We focus on the leading-order effects, namely (i) the key importance of ice permeability, (ii) the role of complex ice rheology depending on temperature, deformation mechanisms and water content, (iii) the possible contribution of surface tension and (iv) the effects of mechanical coupling between the phases. Our analysis suggests that the global water transport through temperate ice is mainly controlled by ice permeability and can be well approximated by a model in which the complex ice rheology is parameterized in terms of a constant viscosity. While the mechanical coupling between the phases dramatically affects the flow at the local scale, the surface tension appears to be insignificant.     

Mineralogy and environmental stability of slags from the Tsumeb smelter,Namibia

Three types of smelting slags originating from historically different smelting technologies in the Tsumeb area (Namibia) were studied: (i) slags from processing of carbonate/oxide ore in a Cu–Pb smelter (1907–1948), (ii) slags from Cu and Pb smelting of sulphide ores (1963–1970) and (iii) granulated Cu smelting slags (1980–2000). Bulk chemical analyses of slags were combined with detailed mineralogical investigation using X-ray diffraction analysis (XRD), scanning electron microscopy (SEM/EDS) and electron microprobe (EPMA). The slags are significantly enriched in metals and metalloids: Pb (0.97–18.4 wt.%), Cu (0.49–12.2 wt.%), Zn (2.82–12.09 wt.%), Cd (12–6940 mg/kg), As (930–75,870 mg/kg) and Sb (67–2175 mg/kg). Slags from the oldest technology are composed of primary Ca- and Pb-bearing feldspars, spinels, complex Cu–Fe and Cu–Cr oxides, delafossite–mcconnellite phases and Ca–Pb arsenates. The presence of arsenates indicates that these slags underwent long-term alteration. More recent slags are composed of high-temperature phases: Ca–Fe alumosilicates (olivine, melilite), Pb- and Zn-rich glass, spinel oxides and small sulphide/metallic inclusions embedded in glass. XRD and SEM/EDS were used to study secondary alteration products developed on the surface of slags exposed for decades to weathering on the dumps. Highly soluble complex Cu–Pb–(Ca) arsenates (bayldonite, lammerite, olivenite, lavendulan) associated with litharge and hydrocerussite were detected. To determine the mineralogical and geochemical parameters governing the release of inorganic contaminants from slags, two standardized short-term batch leaching tests (European norm EN 12457 and USEPA TCLP), coupled with speciation-solubility modelling using PHREEQC-2 were performed. Arsenic in the leachate exceeded the EU regulatory limit for hazardous waste materials (2.5 mg/L). The toxicity limits defined by USEPA for the TCLP test were exceeded for Cd, Pb and As. The PHREEQC-2 calculation predicted that complex arsenates are the most important solubility controls for metals and metalloids. Furthermore, these phases can readily dissolve during the rainy season (October to March) and flush significant amounts of As, Pb and Cu into the environment in the vicinity of slag dumps.     

Upgrading of some instrumentation devoted to increase space radiation environment understanding

Three methods permitting to characterize space and onboard spacecraft radiation environment have been developed and/or upgraded in our laboratories: MDU equipment with a semiconductor detector as sensitive element devoted to register energy deposition spectra in the Si-diode; a spectrometer of the linear energy transfer (LET) based on chemically etched polyallyldiglycolcarbonate (PADC) track etch detectors (TED); and thermoluminescent detectors (TLDs) with different dependences of relative TL yield on the LET of particles transferring their energy in them.We have used all these types of dosimetry equipments onboard spacecrafts since several years and succeeded to treat directly read data in terms of both quantitative and qualitative dosimetry characteristics and deduce from them related radiation risk.During last few years all these three types of detectors have been intensely studied to understand still better their possibilities to characterize space radiation fields. Particularly:

1.

Both PADC TED LET spectrometer and TLDs have been exposed in heavier ion beams with LET in water ranging from 1 to about 700 keV/μm with the goal to upgrade their calibration curves;

2.

A new method of MDU directly read data has been developed, permitting to measure not only dose in Si-detector, but also to estimate radiation protection quantities and the neutron contribution to the onboard exposure level;

3.

All three methods have been tested onboard spacecrafts during several missions.

Contribution presents, analyses and discusses the results obtained in items 1-3 and, also, the possibilities of these detectors to help in characterizing radiation fields during longer space missions, above 1 year.     

Large wood load and transport in a flood-free period within an inter-dam reach: a decade of monitoring the Dyje River,Czech Republic

This study examined the large wood (LW) load and transport during the non-flood period (2009–2018) following major floods that occurred in 2002 and 2006 within the inter-dam reach of the Dyje River (Czech–Austrian border). The LW load was examined in 36 river corridor segments scattered within the reach in the 2009–2018 period. Two whole-reach surveys (2011 and 2019) on LW frequency and distribution were conducted, and the export of LW to the downstream reservoir was analysed between June 2013 and December 2018. In the period of non-flood discharges, the recruitment and depletion of LW were highly variable processes in space and time, leading to a considerable change in the total LW quantity. Whereas the total number of LW pieces decreased, the total LW volume increased because of the increasing dimensions of newly recruited pieces. The annual variability in the quantity of newly recruited pieces was better explained by the variation in the maximum annual discharges (y = 41.043ln(x) + 3.2737, R² = 0.5352) than by the variability in the number of days with wind gusts >17.2 m/s (y = 1.5004x + 82.096, R² = 0.118). The land use change with the abandonment of human settlements after World War II and the progressive expansion of forest was the major historical factor driving the increased recruitment of LW to the river corridor. While the 2006 (>100-year RI) flood brought approximately 1,250 LW pieces to the reservoir, the 2013 (1.5-year RI) flood delivered 45 pieces. The long-term average monthly input of LW to the reservoir was 7.7 pieces. The exceptional low-magnitude flood of 2013, which occurred at the beginning of the monitoring period, was shown to be a threshold above which the number of LW pieces that floated to the dam significantly increased. © 2020 John Wiley & Sons, Ltd.     

A numerical model of exhumation of the orogenic lower crust in the Bohemian Massif during the Variscan orogeny

We present a numerical model of the main phase (370?C335 Ma) of the Variscan orogeny in the central part of the Bohemian Massif. The crustal deformation in our model is driven by radiogenic heating in the felsic lower crust, the lateral contraction of the Moldanubian domain due to convergence with the Saxothuringian plate (in the early stage of orogeny), and the indentation of the Brunovistulian basement into the weakened orogenic root (in the late stage). Our model explains the main geological events inferred from the geological record in the Moldanubian domain: formation of the orogenic plateau and onset of sedimentation at about 345 Ma, rapid exhumation of the orogenic lower crust at about 340 Ma and subsurface flow of crustal material (?? 335 Ma and later). The results of our modeling suggest that delamination of the lithosphere, often invoked to explain the high temperature metamorphism in the orogenic lower crust of the Bohemian Massif, is not the only physical mechanism which can transfer a sufficient amount of heat to the crust to trigger its overturn.     

Gravitational potential energy of the Sun

Summary The gravitational potential energy of the Sun and its corresponding internal energy have been estimated on the basis of the standard model of the Sun's internal structure. It is demonstrated that the principal moment of inertia of the Sun, computed from the model, does not fit the hydrostatic equilibrium limit.     

Industrial specialization and economic performance: A case of Czech microregions

An influential body of literature suggests that economic diversity rather than specialization fuels the economic performance of regions and nations. The authors argue that this hypothesis has no universal applicability and that a more differentiated view is needed. In particular, historical specificity of the local environment and structural characteristics of regional economies should be taken into account. They focus on the effects of industrial specialization on economic performance and the vulnerability of Central European post-communist regions, namely Czech microregions with less than 200,000 inhabitants. They examine whether the economic performance and vulnerability of these regions is fuelled rather by industrial specialization or diversity when controlling for other potential determinants of regional economic performance. Their findings show that the dependence of Czech regions on manufacturing correlates with higher economic performance but also with higher regional vulnerability. In addition, industrial specialization within manufacturing was found to be instrumental for the economic performance of regions with high dependence on manufacturing. With a decreasing share of employment in manufacturing, industrial diversity rather than specialization becomes more valuable for the economic performance of Czech regions.     

Gravitational potential energy of terrestrial planets

Summary The gravitational potential energies of Mercury, Venus and Mars have been computed on the basis of density models and compared to that of the Earth. It has been stated that the specific potential energy per unit mass is very close as regards the pair Earth and Venus, as well as the pair Mercury and Mars.Dedicated to the Memory of K. P     

Climate change scenarios of heat waves in Central Europe and their uncertainties

The study examines climate change scenarios of Central European heat waves with a focus on related uncertainties in a large ensemble of regional climate model (RCM) simulations from the EURO-CORDEX and ENSEMBLES projects. Historical runs (1970–1999) driven by global climate models (GCMs) are evaluated against the E-OBS gridded data set in the first step. Although the RCMs are found to reproduce the frequency of heat waves quite well, those RCMs with the coarser grid (25 and 50 km) considerably overestimate the frequency of severe heat waves. This deficiency is improved in higher-resolution (12.5 km) EURO-CORDEX RCMs. In the near future (2020–2049), heat waves are projected to be nearly twice as frequent in comparison to the modelled historical period, and the increase is even larger for severe heat waves. Uncertainty originates mainly from the selection of RCMs and GCMs because the increase is similar for all concentration scenarios. For the late twenty-first century (2070–2099), a substantial increase in heat wave frequencies is projected, the magnitude of which depends mainly upon concentration scenario. Three to four heat waves per summer are projected in this period (compared to less than one in the recent climate), and severe heat waves are likely to become a regular phenomenon. This increment is primarily driven by a positive shift of temperature distribution, but changes in its scale and enhanced temporal autocorrelation of temperature also contribute to the projected increase in heat wave frequencies.