Simulating zonal scale shifts in the partitioning of surface and subsurface freshwater flow in response to increasing pCO2

Freshwater discharge is one main element of the hydrological cycle that physically and biogeochemically connects the atmosphere, land surface, and ocean and directly responds to changes in pCO₂. Nevertheless, while the effect of near-future global warming on total river runoff has been intensively studied, little attention has been given to longer-term impacts and thresholds of increasing pCO₂ on changes in the partitioning of surface and subsurface flow paths across broad climate zones. These flow paths and their regional responses have a significant role for vegetation, soils, and nutrient leaching and transport. We present climate simulations for modern, near-future (850?ppm), far-future (1880?ppm), and past Late Cretaceous (1880?ppm) pCO₂ levels. The results show large zonal mean differences and the displacement of flows from the surface to the subsurface depending on the respective pCO₂ level. At modern levels the ratio of deeper subsurface to near-surface flows for tropical and high northern latitudes is 1:4.0 and 1:0.5, respectively, reflecting the contrast between permeable tropical soils and the areas of frozen ground in high latitudes. There is a trend toward increased total flow in both climate zones at 850?ppm, modeled to be increases in the total flow of 34 and 51%, respectively, with both zones also showing modest increases in the proportion of subsurface flow. Beyond 850?ppm the simulations show a distinct divergence of hydrological trends between mid- to high northern latitudes and tropical zones. While total wetting reverses in the tropics beyond 850?ppm due to reduced precipitation, with average zonal total runoff decreasing by 46% compared to the 850?ppm simulation, the high northern latitude zone becomes slightly wetter with the average zonal total runoff increasing by a further 3%. The ratio of subsurface to surface flows in the tropics remains at a level similar to the present day, but in the high northern latitude zone the ratio increases significantly to 1:1.6 due to the loss of frozen ground. The results for the high pCO₂ simulations with the same uniform soil and vegetation cover as the Cretaceous are comparable to the results for the Cretaceous simulation, with higher fractions of subsurface flow of 1:5.4 and 1:5.6, respectively for the tropics, and 1:2.2 and 1:1.6, respectively for the high northern latitudes. We suggest that these fundamental similarities between our far future and Late Cretaceous models provide a framework of possible analogous consequences for (far-) future climate change, within which the integrated human impact over the next centuries could be assessed. The results from this modeling study are consistent with climate information from the sedimentary record which highlights the crucial role of terrestrial-marine interactions during past climate change. This study points to profound consequences for soil biogeochemical cycling, with different latitudinal expressions, passing of climate thresholds at elevated pCO₂ levels, and enhanced export of nutrients to the ocean at higher pCO₂.     

Numerical simulation of three-dimensional saltwater–freshwater fingering instabilities observed in a porous medium

We consider saltwater–freshwater fingering instabilities in a saturated porous medium. In the first part, we present three-dimensional results obtained from a laboratory experiment using non-invasive imaging. In the second part, we define a set of model problems in which the performed laboratory experiments can be ranged in. Due to its highly non-linear behavior and inevitable modeling errors, a detailed numerical reproduction of the physical concentration measurements cannot be expected. Nevertheless, four criteria have been identified, two quantitative and two qualitative, which facilitate a substantiated comparison of the physical experiment and the numerical simulation. With respect to these criteria a high degree of similarity could be observed. The use of these features allows a deeper understanding of the physical processes and the influence of the initial conditions.     

Late Cretaceous eclogite in the Eastern Rhodopes (Bulgaria): evidence for subduction under the Sredna Gora magmatic arc

International Journal of Earth Sciences - The Rhodopes in Bulgaria and Greece represent a nappe stack of high-grade units with polymetamorphic history. Constraining the time of metamorphism in...     

Die Quadalquivirstörung

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Bacterial consortium and axenic cultures isolated from activated sewage sludge for biodegradation of imidazolium-based ionic liquid

Extensive research and increasing number of potential industrial applications made ionic liquids (ILs) important materials in design of new, cleaner technologies. Together with the technological applicability, the environmental fate of these chemicals is considered and significant efforts are being made in designing strategies to mitigate their potential negative impacts. Many ILs are proven to be poorly biodegradable and relatively toxic. Bioaugmentation is known as one of the ways of enhancing the microbial capacity to degrade xenobiotics by addition of specialized strains. The aim of current work was to select microbial species that could be used for bioaugmentation in order to enhance biodegradation of ILs in the environment. We subjected activated sewage sludge to the selective pressure of 1-methyl-3-octylimidazolium chloride ([OMIM][Cl]) and isolated nine strains of bacteria which were able to prevail in these conditions. Subsequently, we utilized axenic cultures (pure cultures) of these bacteria as well as mixed consortium to degrade this IL. In addition, we performed growth inhibition tests and found that bacteria were able to grow in 2 mM, but not in 20 mM solutions of [OMIM][Cl]. The biodegradation conducted by the isolated consortium was higher than conducted by the activated sewage sludge when normalized by the cell density, which indicates that the isolated strains seem specifically suited to degrade the IL.     

The Impact of Global/Local Bias on Task-Solving in Map-Related Tasks Employing Extrinsic and Intrinsic Visualization of Risk Uncertainty Maps

The form of visual representation affects both the way in which the visual representation is processed and the effectiveness of this processing. Different forms of visual representation may require the employment of different cognitive strategies in order to solve a particular task; at the same time, the different representations vary as to the extent to which they correspond with an individual’s preferred cognitive style. The present study employed a Navon-type task to learn about the occurrence of global/local bias. The research was based on close interdisciplinary cooperation between the domains of both psychology and cartography. Several different types of tasks were made involving avalanche hazard maps with intrinsic/extrinsic visual representations, each of them employing different types of graphic variables representing the level of avalanche hazard and avalanche hazard uncertainty. The research sample consisted of two groups of participants, each of which was provided with a different form of visual representation of identical geographical data, such that the representations could be regarded as ‘informationally equivalent’. The first phase of the research consisted of two correlation studies, the first involving subjects with a high degree of map literacy (students of cartography) (intrinsic method: N?=?35; extrinsic method: N?=?37). The second study was performed after the results of the first study were analyzed. The second group of participants consisted of subjects with a low expected degree of map literacy (students of psychology; intrinsic method: N?=?35; extrinsic method: N?=?27).The first study revealed a statistically significant moderate correlation between the students’ response times in extrinsic visualization tasks and their response times in a global subtest (r?=?0.384, p?<?0.05); likewise, a statistically significant moderate correlation was found between the students’ response times in intrinsic visualization tasks and their response times in the local subtest (r?=?0.387, p?<?0.05). At the same time, no correlation was found between the students’ performance in the local subtest and their performance in extrinsic visualization tasks, or between their scores in the global subtest and their performance in intrinsic visualization tasks. The second correlation study did not confirm the results of the first correlation study (intrinsic visualization/‘small figures test’: r?=?0.221; extrinsic visualization/‘large figures test’: r?=?0.135). The first phase of the research, where the data was subjected to statistical analysis, was followed by a comparative eye-tracking study, whose aim was to provide more detailed insight into the cognitive strategies employed when solving map-related tasks. More specifically, the eye-tracking study was expected to be able to detect possible differences between the cognitive patterns employed when solving extrinsic- as opposed to intrinsic visualization tasks. The results of an exploratory eye-tracking data analysis support the hypothesis of different strategies of visual information processing being used in reaction to different types of visualization.     

Multicomponent diffusion in garnets I: general theoretical considerations and experimental data for Fe–Mg systems

We have carried out a combined theoretical and experimental study of multicomponent diffusion in garnets to address some unresolved issues and to better constrain the diffusion behavior of Fe and Mg in almandine–pyrope-rich garnets. We have (1) improved the convolution correction of concentration profiles measured using electron microprobes, (2) studied the effect of thermodynamic non-ideality on diffusion and (3) explored the use of a mathematical error minimization routine (the Nelder-Mead downhill simplex method) compared to the visual fitting of concentration profiles used in earlier studies. We conclude that incorporation of thermodynamic non-ideality alters the shapes of calculated profiles, resulting in better fits to measured shapes, but retrieved diffusion coefficients do not differ from those retrieved using ideal models by more than a factor of 1.2 for most natural garnet compositions. Diffusion coefficients retrieved using the two kinds of models differ only significantly for some unusual Mg–Mn–Ca-rich garnets. We found that when one of the diffusion coefficients becomes much faster or slower than the rest, or when the diffusion couple has a composition that is dominated by one component (>75 %), then profile shapes become insensitive to one or more tracer diffusion coefficients. Visual fitting and numerical fitting using the Nelder-Mead algorithm give identical results for idealized profile shapes, but for data with strong analytical noise or asymmetric profile shapes, visual fitting returns values closer to the known inputs. Finally, we have carried out four additional diffusion couple experiments (25–35 kbar, 1,260–1,400 °C) in a piston-cylinder apparatus using natural pyrope- and almandine-rich garnets. We have combined our results with a reanalysis of the profiles from Ganguly et al. (1998) using the tools developed in this work to obtain the following Arrhenius parameters in D = D ₀ exp{–[Q _1bar + (P–1)ΔV ⁺]/RT} for D _Mg^* and D _Fe^*: Mg: Q _1bar = 228.3 ± 20.3 kJ/mol, D ₀ = 2.72 (±4.52) × 10⁻¹⁰ m²/s, Fe: Q _1bar = 226.9 ± 18.6 kJ/mol, D ₀ = 1.64 (±2.54) × 10⁻¹⁰ m²/s. ΔV ⁺ values were assumed to be the same as those obtained by Chakraborty and Ganguly (1992).     

Interplanetary dust detected by the Cassini CDA Chemical Analyser

During its cruise phase, prior to encountering Jupiter, the Cosmic Dust Analyser (CDA) onboard the Cassini spacecraft returned time of flight mass spectra (TOF MS) of two interplanetary dust particles. Both particles were found to be iron-rich, with possible traces of hydrogen, carbon, nickel, chromium, manganese, titanium, vanadium and minor silicates. Carbon, hydrogen, oxygen and potassium are also present as possible contaminants of the impact target of CDA. Silicates and magnesium do not feature predominantly in the spectra; this is surprising considering the expected dominance of silicate-rich minerals in interplanetary dust particles. The particle masses are and . The corresponding radii ranges for the particles, assuming densities from 7874-2500 kg m⁻³ are 0.7-4 μm and 2.6-6.8 μm, respectively. With the same density assumptions the β values (ratio of radiation pressure to gravitational force) are estimated as 0.027-0.21 and 0.016-0.06 respectively, allowing possible orbits to be calculated. The resulting orbits are bound and prograde with semi-major axes, eccentricities and inclinations in the region of 0.3-1.26 AU, 0.4-1.0 and 0-60° for the first particle and 0.8-2.5 AU, 0.2-0.9 and 0-30° for the second. The more probable orbits within these ranges indicate that the first particle is in an Aten-like orbit, whilst the second particle is in an Apollo-like orbit, despite both grains having very similar, predominantly metallic compositions. Other possible orbital solutions for both particles encompass orbits which more closely resemble those of Jupiter-family comets.