Determination of SO4β1 for yttrium and the rare earth elements at I = 0.66 m and t = 25°C—implications for YREE solution speciation in sulfate-rich waters

We present a complete set of stability constants (_SO4β₁) for the monosulfato-complexes of yttrium and the rare earth elements (YREE), except Pm, at I = 0.66 m and t = 25°C, where _SO4β₁ = [MSO₄⁺] × [M³⁺]⁻¹[SO₄²⁻]⁻¹ (M ≡ YREE and brackets indicate free ion concentrations on the molal scale). Stability constants were determined by investigating the solubility of BaSO₄ in concentrated aqueous solutions of MCl₃. This is the first complete set to be published in more than 30 years.The resulting _SO4β₁ pattern is very similar in shape to one reported by de Carvalho and Choppin (1967a) (I = 2 mol/L; t = 25°C) that has been largely ignored. Stability constants vary little between La and Sm, but display a weak maximum at Eu. Between Eu and Lu, _SO4β₁ decreases by 0.2 log units, substantially exceeding the ±0.02 log unit average analytical precision. The stability constant for Y is approximately equal to that for Er. Our _SO4β₁ pattern is consequently distinctly different from the consensus pattern, based on a single data set from 1954, which is essentially flat, with a range of only 0.07 log units between the lowest and highest _SO4β₁ values within the lanthanide series (excluding Y).Values of _SO4β₁ obtained in this work, in conjunction with the ion-pairing model of Millero and Schreiber (1982), allow prediction of _SO4β₁ between 0 and 1 m ionic strength. These results are used to assess both the absolute and relative extent of YREE sulfate complexation in acidic, sulfate-rich waters.     

Carbonate slope re-sedimentation in a tectonically-active setting (Western Sicily Cretaceous Escarpment,Italy)

Tectonic processes are widely considered as a mechanism causing carbonate platform margin instabilities leading to the emplacement of mass transport deposits and calciturbidites. However, only few examples establishing a clear link between tectonics and re-sedimentation processes are known from the literature. The two-dimensional and three-dimensional wire-cut walls of hundreds of quarries extracting ornamental limestones (for example, Perlato di Sicilia) from the Western Sicily Cretaceous Escarpment in Italy expose a series of mass transport deposits. The depositional architecture, spatial facies distribution and sedimentary features of these deposits were studied in detail. Thin section analysis was used to define the microfacies characteristics and to determine the age of the re-sedimented limestones. Eleven facies types grouped into four facies associations were recognized that defined specific depositional processes and environments. The stratigraphic architecture of the slope was reconstructed using four composite facies successions based on the detailed analysis and correlation of the field sections. The palaeoslope orientation was reconstructed based on the analysis of synsedimentary faults, slump scars and pinch-out geometries. The Western Sicily Cretaceous Escarpment was strongly influenced by synsedimentary transtensional tectonics in combination with magmatic processes, as suggested by the presence of tuffites and pillow lava intercalations within the re-sedimented carbonate series. These volcanics point to a major role of crustal shear as a trigger for mass transport deposit emplacement. The facies distribution along the Western Sicily Cretaceous Escarpment delivers new insights into the deformation processes accompanying the crustal extension of the Cretaceous western Tethys realm.     

A hydropedological approach to simulate streamflow and soil water contents with SWAT+

Reflecting internal catchment hydrological processes in hydrological models is important for accurate predictions of the impact of climate and land-use change on water resources. Characterizing these processes is however difficult and expensive due to their dynamic nature and spatio-temporal variability. Hydropedology is a relatively new discipline focusing on the synergistic integration of hydrology, soil physics and pedology. Hydropedological interpretations of soils and soil distribution can be used to characterize key hydrological processes, especially in areas with no or limited hydrometric measurements. Here we applied a hydropedological approach to reflect flowpaths through detailed routing in SWAT+ for a 157 ha catchment (Weatherley) in South Africa. We compared the hydropedological approach and a standard (no routing) approach against measured streamflow (two weirs) and soil water contents (13 locations). The catchment was treated as ‘ungauged’ and the model was not calibrated against hydrometric measurements in order to determine the direct contribution of hydropedology on modelling efficiency. Streamflow was predicted well without calibration (NSE > 0.8; R² > 0.82) for both approaches at both weirs. The standard approach yielded slightly better streamflow predictions. The hydropedological approach resulted in considerable improvements in the simulation of soil water contents (R² increased from 0.40 to 0.49 and PBIAS decreased from 40% to 20%). The routing capacity of SWAT+ as employed in the hydropedological approach reduced the underestimation of wetland water regimes drastically and resulted in a more accurate representation of the dominant hydrological processes in this catchment. We concluded that hydropedology can be a valuable source of ‘soft data’ to reflect internal catchment structure and processes and, potentially, for realistic calibrations in other studies, especially those conducted in areas with limited hydrometric measurements.     

Thermoelastic stress due to a rectangular heat source in a semi-infinite medium. Presentation of an analytical solution

The thermoelastic response due to a time-dependent rectangular heat source in a semi-infinite medium is analyzed. The problem originates from studies of nuclear waste repositories in rock. Canisters containing heat-emitting nuclear waste are deposited over a large rectangular area deep below the ground surface. The solution for a time-dependent heat source is obtained from the corresponding instantaneous heat source by superposition. The thermoelastic problem for the instantaneous rectangular heat source in a infinite surrounding is solved exactly. An important step is the introduction of so-called quadrantal heat sources. The solution for the rectangle is obtained from four quadrantal solutions. The solution for the quadrantal heat source depends on the three dimelasionless coordinates only. Time occurs in the scale factors only. The condition of zero normal and shear stresses at the ground surface is fulfilled by using a mirror heat source and a boundary solution. The boundary solution accounts for the residual normal stress at the ground surface. Using a Hertzian potential, a surprisingly simple solution is obtained. The final analytical solution is quite tractable considering the complexity of the initial problem. The solution may be used to test numerical models for coupled thermoelastic processes. It may also be used in more detailed numerical simulations of the process near the heat sources as boundary conditions to account for the three-dimensional global process.     

The Černý Důl deposit (Czechoslovakia): An example of Ni-, Fe-, Ag-, Cu-arsenide mineralization with extremely high activity of arsenic; new data on paxite,novakite and kutinaite

Summary The erný Dl mineralization (Giant Mts., Czechoslovakia) consists of calcite veins cross-cutting metamorphic rocks and exhibiting a complex paragenesis of Ni-, Fe-, (Co)- and Cu-, Ag-arsenides associated with native arsenic. Several new minerals belonging to Cu–As and Cu–Ag–As systems were described from this deposit (koutekite, novakite, paxite, kutinaite). New data on paxite, novakite and kutinaite were obtained. Paxite, CuAs₂, is monoclinic,P2₁/c,a=5.830,b=5.111,c=8.084 Å, =99.7°,Z=4,D _calc=5.97 g/cm³, polysynthetically twinned along (010). Novakite belongs to the Cu–Ag–As system. It is monoclinic,C2/m,Cm orC2,a=16.269,b=11.711,c=10.007 Å, -112.7°,Z=4,D _calc=8.01 g/cm³. The ideal formula is Cu_20+x Ag_1–x As₁₀,x0.16. New microprobe analyses of kutinaite indicate a cell-content of 4 [Cu₁₄Ag₆As₇],D _calc=8.37 g/cm³.

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Résumé La minéralisation du gisement de erný Dl (Monts des Géants, Tchécoslovaquie) se distingue par une paragenèse complexe d'arséniures de Ni, Fe, (Co), Cu et Ag associés à l'arsenic natif, et apparaissant dans des filons de calcite qui recoupent une série de roches métamorphiques. Plusieurs minéraux nouveaux appartenant aux systèmes Cu–As et Cu–Ag–As ont été découverts dans ce gisement (koutekite, novakite, paxite, kutinaïte). De nouvelles données sur la paxite, la novakite et la kutinaïte ont été obtenues. La paxite, CuAs₂, est monoclinique,P2₁/c,a=5,830,b=5,111,c=8,084 Å, =99,7°,Z=4,D _calc=5,97 g/cm³; elle est polysythétiquement maclée suivant (010). La novakite est une phase du système Cu–Ag–As. Elle est monoclinique,C2/m,Cm ouC2,a=16,269,b=11,711,c=10,007 Å, =112,7°,Z=4,D _calc=8,01 g/cm³. Saformule idéale s'écrit Cu_20+x Ag_1–x As₁₀,x0,16. Des analyses de la kutinaïte conduisent à 4 [Cu₁₄Ag₆As₇] par maille,D _calc=8,37 g/cm³.L'étude paragénétique a permis de voir que le système hydrothermal à erný Dl couvre un interval de température large, s'étalant de500° à 100°C environ. Une très forte activité d'arsenic au cours des épisodes minéralisants tardifs a abouti à la cristallisation des arséniures de Cu riches en arsenic, stables à basse température. Cinq épisodes minéralisants ont été reconnus: le dépôt des arséniures de Ni, Fe, (Co) (löllingite, nickéline, pararammelsbergite, chloentite) était suivi de: kutinaïte, koutekite, arsenic natif et arséniures de cuivre riches en arsenic (novakite, Cu₂As, paxite). L'abondance des carbonates laisse entrevoir un rôle de composés ou de complexes de carbone dans l'évolution de ce système hydrothermal fortement réducteur.The study of mineral associations showed that the erný Dl hydrothermal system extended over a large temperature interval from 500° to 100°C. An extremely high arsenic activity during the late mineralization periods lead to the precipitation of low-temperature, As-rich copper arsenides. Five mineralization periods were distinguished: the precipitation of Ni-, Fe-, (Co)-arsenides (löllingite, nickeline, pararammelsbergite, chloanthite) was followed by kutinaite, koutekite, native arsenic and As-rich copper arsenides (novakite, Cu₂As, paxite). The abundance of carbonates suggests a possible role of carbon compounds or complexes in the evolution of this highly reducing hydrothermal system.

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With 2 Figures     

La sénégalite,Al2 (PO4) (OH)3 · H2O,un nouveau minéral

Senegalite is orthorhombic, mm2, a:b:c:=1.296:1:1.007; $\text{a}{}_0\text{=9.673,}\text{b}{}_0\text{=7.596,}\text{c}{}_0\text{=7.668}\text{A}\text{?}$, Z=4, G_calc=2551; space group Pna2. The strongest lines in the powder pattern are: 5.41(7); 4.089(9); 3.834(10); 3.610(8); 2.990(9); 2.348(8); 2.070(7) 1.929(7); 1.505(7) Å. The chemical analysis: Al₂O₃ ? 46.23; Fe₂O₃ ? 0.28; P₂O₅ ? 31.85 H₂O ? 21.00; sum 99.34, gives a formula Al₂(PO₄)(OH)₃ · H₂O. Colourless optically biaxial positive, n_S: α=1.562, β=1.566, γ=1.587, plane of optical axies (001), Z=a, Y=c; 2V=53°, weak dispersion r > v. Measured density 2.552. The DTA curve shows endothermic reactions at 250, 370 and 440°C corresponding to the dehydration of mineral. Infrared spectrum indicates the presence of OH and H₂O groups. Found in oxidation zone of Kouroudiako iron deposit, Senegal, associated with turquoise, augelite, wavellite and crandallite.     

Impact of Hydropower Regulation on River Water Composition in Northern Sweden

Using hydrogeochemical analysis of two large boreal rivers (pristine Kalix and hydropower regulated Lule) discharging into the Gulf of Bothnia, the major impacts of regulation on water discharge, element transport and their seasonal redistribution have been assessed. The pre-regulation hydrogeochemical features were assumed to be similar for the two rivers. For the Lule River, the average maximum runoff was almost halved, while the average minimum was tripled as a result of the regulation. The fraction of winter transport of total organic carbon (TOC), Fe, Si, suspended Mn and P in the Lule River was, according to a conservative estimate, two to three times higher than in the pristine river. Longer residence time in the Lule River delayed arrival of the suspended Mn peak and dissolved Si decline to the river mouth. During summer, the suspended C/N ratio in the regulated river was 10–20 compared to <10 for the pristine, suggesting presence of predominantly old organic material. This was supported by a virtually constant suspended P/Fe ratio throughout the year in the Lule River, indicating low abundance of phytoplankton. TOC varied irregularly in the Lule River suggesting temporal disconnection between the river and the upper riparian zone. The disappearance of the spring flow maximum, a shift of element transport from spring to winter and supply of mainly old organic material during the vegetation growth season may have a pronounced impact on the ecosystem of the Gulf of Bothnia and the river itself.     

Coastal flood risks and seasonal tourism: analysing the effects of tourism dynamics on casualty calculations

Since coastal tourism is one of the fastest growing sectors of tourism industry, coastal areas have become increasingly vulnerable in the case of flooding. While in recent years a number of different methods have been put forward to map coastal flood risks, the implications of tourism dynamics for the assessment of human casualties has remained largely overlooked in these models. This chapter examines to what extent the ignorance of (residential) coastal tourism may bias the calculations of human casualties. To this end, a case study has been conducted on the Belgian coast. Both the dynamic nature of coastal tourism and the behaviour of residential tourists in storm surge scenarios are considered. The results of this study show that including tourism dynamics in flood risk management is justified and appropriate, depending on the tourist attractiveness of the flood-prone area and its temporal fluctuations.