Hoarfrost and rime chemistry in Poland—An introductory analysis from meteorological perspective

Hoarfrost and rime analysis was based on the collection of samples between 2003 and 2006 from 8 sites, which represent both lowland (northern) and mountainous (southern) parts of Poland. On the other hand 4 of these sites belong to “urban” and 4 to “rural” category. pH, conductivity, SO₄²⁻, NO₃⁻, Cl⁻, H⁺, NH₄⁺, Ca²⁺, Mg²⁺, Na⁺, K⁺ have been determined in order to study the chemistry of hoarfrost and rime. Higher total inorganic ionic content (TIC) in hoarfrost and rime (2.46 meq·l⁻¹ and 1.23 meq·l⁻¹ respectively) was observed when compared with precipitation (0.37 meq·l⁻¹). Large variability of TIC and chemical composition of individual samples were typical at each of the measurement sites depending on emission patterns, atmospheric conditions and local terrain topography. Higher concentrations of both hoarfrost and rime occurred in southern (mountainous) rather than in northern (lowland) part of Poland which can be explained by worse pollutant dispersion conditions in the south. The surprisingly low hoarfrost concentrations in urban coastal stations in the area of the Bay of Gdansk were attributed to the cleaning effect of nocturnal breeze-type circulation, best pronounced in cool part of the year. Due to relatively high pollutant concentration and long duration, hoarfrost and rime are at least significant factors in environmental processes in different ecosystems in Poland.     

Geo‐questionnaire: A Method and Tool for Public Preference Elicitation in Land Use Planning

Geo‐questionnaire involves an integration of sketchable maps with questions, aimed at eliciting public preferences and attitudes about land allocation and services. Respondents can link their answers with corresponding locations on a map by marking points or sketching polygon features. Geo‐questionnaires have been used to learn about perceptions and preferences of city residents for specific types of land use, place‐based services, and development projects. This article reports on results of an empirical study, in which an online geo‐questionnaire was designed and implemented to elicit preferences of residents in guiding an urban development plan. Preferences collected in the form of polygon sketches were processed using GIS operations and mapped for visual interpretation. The article focuses on aggregation and analysis of respondent preferences including the analysis of positional and attribute uncertainty. Results of the study show that geo‐questionnaire is a scalable method for eliciting public preferences with a potential for meaningfully informing land use planning.     

2-D seismic tomographic and ray tracing modelling of the crustal structure across the Sudetes Mountains basing on SUDETES 2003 experiment data

The seismic data obtained during SUDETES 2003 experiment are analysed, and detailed crustal structure for profiles S02, S03 and S06 is presented using three different 2-D techniques: (1) “smooth” tomography of refracted waves travel times, (2) ray tracing of reflected and refracted waves, and (3) joint velocity and depth of reflector tomographic inversion. In spite of different interpretation techniques used, the models of the crustal structure show common characteristic features. The low velocity (V_p < 4 km/s) sedimentary layer was documented in the northeastern part of the study area. The topmost basement has in general a velocity of 5.8–6.0 km/s, and velocities at ca. 20 km depth are 6.15–6.25 km/s. The strong reflecting boundaries were found at 20–23 and 25–28 km depth with a velocity contrast about 0.4 km/s, and the highest velocities in the lowermost crust are 6.8–7.2 km/s. In general, the crust of the Bohemian Massif is slightly thicker (33–35 km) than in the northern part of the area. Velocities beneath Moho are relatively low, of 7.95 km/s. On the basis of well recorded reflected waves, mantle reflectors were discovered in the depth interval ca. 40–70 km. Apart of new results for the geology and tectonics of the area, some conclusion could be made about different techniques used. In the 2-D case the “clasical” ray tracing method with using all correlated phases gives the most adequate model of the structure, because of full, manual control of the model creation. The “smooth” first arrival travel times tomography, although very fast, is not satisfactory enough to describe the complex structure. So, the best candidate in 3-D case seems to be travel time tomography for both refracted and reflected waves in multi-layers models.     

Platinum-group element distribution in the oxidized Main Sulfide Zone, Great Dyke, Zimbabwe

In the Great Dyke mafic/ultramafic layered intrusion of Zimbabwe, economic concentrations of platinum-group elements (PGE) are restricted to sulfide disseminations in pyroxenites of the Main Sulfide Zone (MSZ). Oxidized ores near the surface constitute a resource of ca. 400 Mt. Mining of this ore type has so far been hampered due to insufficient recovery rates. During the oxidation/weathering of the pristine ores, most notably, S and Pd are depleted, whereas Cu and Au are enriched. The concentrations of most other elements (including the other PGE) remain quite constant. In the oxidized MSZ, PGE occur in different modes: (1) as relict primary PGM (mainly sperrylite, cooperite, and braggite), (2) in solid solution in relict sulfides (dominantly Pd in pentlandite, up to 6,500 ppm Pd and 450 ppm Pt), (3) as secondary PGM neoformations (i.e., Pt–Fe alloy and zvyagintsevite), (4) as PGE oxides/hydroxides that replace primary PGM as the result of oxidation, (5) hosted in weathering products, i.e., iron oxides/hydroxides (up to 3,600 ppm Pt and 3,100 ppm Pd), manganese oxides/hydroxides (up to 1.6 wt.% Pt and 1,150 ppm Pd), and in secondary phyllosilicates (up to a few hundred ppm Pt and Pd). In the oxidized MSZ, most of the Pt and Pd are hosted by relict primary and secondary PGM; subordinate amounts are found in iron and manganese oxides/hydroxides. The amount of PGE hosted in solid solution in sulfides is negligible. Considerable local variations in the distribution of PGE in the oxidized ores complicate a mineralogical balance. Experiments to evaluate the PGE recovery from oxidized MSZ ore show that using physical concentration techniques (i.e., electric pulse disaggregation, hydroseparation, and magnetic separation), the PGE are preferentially concentrated into smaller grain size fractions by a factor of 2. Highest PGE concentrations occur in the volumetrically insignificant magnetic fraction. This indicates that a physical preconcentration of PGE is not feasible and that chemical, bulk-leaching methods need to be developed in order to successfully recover PGE from oxidized MSZ ore.     

Elasticity and equation of state of Li<Subscript>2</Subscript>B<Subscript>4</Subscript>O<Subscript>7</Subscript>

A single crystal X-ray diffraction study on lithium tetraborate Li₂B₄O₇ (diomignite, space group I4₁ cd) has been performed under pressure up to 8.3 GPa. No phase transitions were found in the pressure range investigated, and hence the pressure evolution of the unit-cell volume of the I4₁ cd structure has been described using a third-order Birch–Murnaghan equation of state (BM-EoS) with the following parameters: V ₀  = 923.21(6) ų, K ₀  = 45.6(6) GPa, and K′ = 7.3(3). A linearized BM-EoS was fitted to the axial compressibilities resulting in the following parameters a ₀  = 9.4747(3) Å, K _0a  = 73.3(9) GPa, K′ _a  = 5.1(3) and c ₀  = 10.2838(4) Å, K _0c  = 24.6(3) GPa, K′ _c  = 7.5(2) for the a and c axes, respectively. The elastic anisotropy of Li₂B₄O₇ is very large with the zero-pressure compressibility ratio β _0c /β _0a  = 3.0(1). The large elastic anisotropy is consistent with the crystal structure: A three-dimensional arrangement of relatively rigid tetraborate groups [B₄O₇]²⁻ forms channels occupied by lithium along the polar c–axis, and hence compression along the c axis requires the shrinkage of the lithium channels, whereas compression in the a direction depends mainly on the contraction of the most rigid [B₄O₇]²⁻ units. Finally, the isothermal bulk modulus obtained in this work is in general agreement with that derived from ultrasonic (Adachi et al. in Proceedings-IEEE Ultrasonic Symposium, 228–232, 1985; Shorrocks et al. in Proceedings-IEEE Ultrasonic Symposium, 337–340, 1981) and Brillouin scattering measurements (Takagi et al. in Ferroelectrics, 137:337–342, 1992).     

Buried Late Weichselian thermokarst landscape discovered in the Czech Republic,central Europe

Pronounced climatic warming associated with the Late Weichselian Pleniglacial‐to‐Lateglacial transition caused considerable environmental changes throughout the former periglacial zones (in Europe ~53°–46°N). During permafrost degradation and subsequent ground subsidence (i.e. thermokarst processes), the landscape changed rapidly. In this study we investigated a flat mid‐altitude area in south Bohemia, Czech Republic, lying close to the southern limit of the Weichselian permafrost. We discovered palaeo‐lake basins with sedimentary infillings up to 11 m in depth. According to radiocarbon and palynostratigraphical dating, these basins were formed at the onset of the Late Pleniglacial‐to‐Lateglacial transition, whereas the smaller depressions were formed later. We suggest that the basins resulted from thermal and fluvio‐thermal erosion of the former permafrost and represent remnants of discontinuous gullies and possibly collapsed frost mounds (pingo/lithalsa scars). The formation of this a fossil thermokarst landscape was climatically driven and multiple phased, with the major phase during the climatic warming and wetting at the onset of GI‐1e (Bølling) and the minor phase during GI‐1c (Allerød). This study enhances knowledge of the palaeogeography of the former European periglacial zone by showing that Late Pleistocene thermokarst activity could have had a significant impact on the evolution of the landscape of at least some regions of central Europe along the southern limit of the continuous permafrost zone. The research also points to a similar history for the physical transformation of the landscape of the former European periglacial zone and current thermokarst landscapes and could be a valuable source of information with respect to the future transformation of the Arctic under conditions of ongoing global warming.     

Determination of three-dimensional in situ stresses from anelastic strain recovery measurement of cores at great depth

In order to examine whether the anelastic strain recovery (ASR) method can be applied for determining the in situ stress in hard rocks at great depths, the anelastic strain recovery of oriented cores was measured in six independent directions. The core specimens were taken from four depths within the range of about 2400–4500 m MD at the METI Niitsu well in Japan; the rock materials were mudstone, dolerite, basalt and andesite. For all the rocks the expansional anelastic strains were obtained, the magnitude of the strains in various directions continuously measured for 1 or 2 weeks was of the order of 1000 × 10^− 6 in mudstone; in contrast, strains of the other cores did not exceed a few hundred microstrains. These strains were used for a three-dimensional analysis of the principal in situ stresses. At the third depth, the principal stress directions were considered to be affected by fractures pre-existing near the core, and showed the features of a very local stress state. With the exception of this data, the directions determined by the ASR method were in agreement with those determined using other in situ measurement methods. Based on two assumptions, i.e., (i) the rock stress in vertical direction is equal to density-related gravitational overburden stress, (ii) the ratio of anelastic strain recovery compliance of shear deformation mode and the compliance of volumetric deformation mode is equal to 2, the values of the three principal stresses were estimated. The values of the minimum principal stress in the plane perpendicular to the well axis determined in this study were in agreement with those determined based on extended leak-off tests (ELOT or XLOT) conducted at the same well. Therefore, it can be said that the ASR method is well suited for use in directly determining the directions of principal in situ stresses in three dimensions and in estimating the magnitude of the stresses in isotropic rocks at great depths, such as those encountered when drilling deep into a submarine seismogenic zone.     

Elastic properties of seafloor sediments from the modelling of amplitudes of multiple water waves recorded on the seafloor off Bear Island,North Atlantic

Wide‐angle seismic data acquired by use of air‐guns and ocean bottom seismometers (OBS) contain strong direct water arrivals and multiples, generally considered as noise and thus not included in the modelling. However, a recent study showed that standard ray‐tracing modelling of the water multiples recorded off the Bear Island, North Atlantic, provided a reliable estimate of the velocity distribution in the water layer. Here, we demonstrate that including the amplitudes in the modelling provide valuable information about the V_P contrast at the seafloor, as well as the V_P/V_S ratio and attenuation (Q_P) of the uppermost sediments. The V_P contrast at the seafloor is estimated at about 250 m/s, within a precision of approximately ±30 m/s. The V_P/V_S ratio in the uppermost sedimentary layer is modelled in the range 2.25–2.50 and the Q_P factor is estimated at 1000 for the water, 30–50 for the uppermost layer and 40–50 for the second sedimentary layer. The values obtained for the sediments suggest a lithology dominated by silty clays, with porosity below average.     

Modelling hydraulic and capillary-driven two-phase fluid flow in unsaturated concretes at the meso-scale with a unique coupled DEM-CFD technique

The goal of the research was to demonstrate the impact of thin porous interfacial transition zones (ITZs) between aggregates and cement matrix on fluid flow in unsaturated concrete caused by hydraulic/capillary pressure. To demonstrate this impact, a novel coupled approach to simulate the two-phase (water and moist air) flow of hydraulically and capillary-driven fluid in unsaturated concrete was developed. By merging the discrete element method (DEM) with computational fluid dynamics (CFD) under isothermal settings, the process was numerically studied at the meso-scale in two-dimensional conditions. A flow network was used to describe fluid behaviour in a continuous domain between particles. Small concrete specimens of a simplified particle mesostructure were subjected to fully coupled hydro-mechanical simulation tests. A simple uniaxial compression test was used to calibrate the pure DEM represented by bonded spheres, while a permeability and sorptivity test for an assembly of spheres was used to calibrate the pure CFD. For simplified specimens of the pure cement matrix, cement matrix with aggregate, and cement matrix with aggregate and ITZ of a given thickness, DEM/CFD simulations were performed sequentially. The numerical results of permeability and sorptivity were directly compared to the data found in the literature. A satisfactory agreement was achieved. Porous ITZs in concrete were found to reduce sorption by slowing the capillary-driven fluid flow, and to speed the full saturation of pores when sufficiently high hydraulic water pressures were dominant.