Transboundary flow modeling: the Zohor depression of Austria and the Slovak Republic

Estimation of available ground water is a basic aspect of ground water management. Mathematical modeling is one of the methods that can be effectively used to obtain such estimates. A numerical model was used to calculate available ground water in the Zohor depression-an aquifer transcending national boundaries between the Slovak Republic and Austria. The aquifer, formed by Quaternary sediments overlying Neogene sequences, is composed of various clays interbedded with layers of sand, gravel, sandstones, and conglomerates. The AQUA computer model package was used to simulate flow in the aquifer. For model compilation, the following data were used: (1) effective precipitation; (2) surface water levels in surface water gauging profiles; and (3) withdrawal amounts. Hydraulic parameters of the aquifer were estimated based on information from 86 wells located in the area. The model was verified using data on ground water levels from a monitoring network. The simulation of the aquifer system permitted the estimation of the available ground water in the study area, showing that an additional 587 L/s can be abstracted. Ground water inflows to the Morava River, which flows through the region, range from 745 to 3100 L/s.     

CALCIUM-ALUMINIUM-RICH CHONDRULES IN THE UNEQUILIBRATED ORDINARY CHONDRITES

Calcium-aluminium-rich chondrules were found in L-3 (ALH-77015) and LL-3 (ALH-77278) chondrites. They consist of spinel, olivine, fassaite and glassy groundmass enriched in anorthite component. The bulk chemical compositions of the two chondrules are nearly the same and resemble those of the calcium-aluminium-rich inclusions in the carbonaceous chondrites, but the former is more enriched in MgO and SiO₂ and depleted in Al₂O₃ and CaO. The calcium-aluminium-rich chondrules would have been primarily early condensates which existed at the place where the chondrules were formed, and heated up to 1400 °C or higher to have melted and cooled at the rate similar to those for other chondrules, or the products of intensive heating followed by reaction with gas.     

Cosmic-ray streaming and anisotropies

The principal result of this paper is the demonstration that in interplanetary space the electric-field drifts and convective flow parallel to the magnetic field of cosmic-ray particles combine as a simple convective flow with the solar wind. In addition there are diffusive currents and transverse gradient drift currents. With this interpretation direct reference to the interplanetary electric-field drifts is eliminated and the study of steady-state and transient cosmic-ray anisotropies is both more systematic and simpler. Following a discussion of our present knowledge of the diffusion coefficient in the interplanetary medium, the theory is applied to steady-state anisotropies near Earth in the kinetic energy (T) range 7.5 MeV<T<20 GeV. First the theory of the diurnal variation atT>-2 GeV is examined and it is suggested that the azimuthal streaming associated with the observations be regarded simply as proof that there is no significant net radial flow of cosmic rays at these energies. Second, it is predicted that, near Earth, the radial anisotropy will have a (+?+) variation with energy and this prediction is very insensitive to the precise values of the parameters used: intensity spectrum, solar wind speed, radial density gradient, and diffusion coefficient. Then, third, the small and radial steady-state anisotropies reported by Raoet al. (1967) in the intervals 7.5<T<45 MeV and 45<T<90 MeV are re-examined and it is found that the gradients and diffusion coefficients required to produce the reported anisotropies in 7.5<T<45 MeV are inconsistent with those expected from other data.     

Seafloor environmental changes resulting from nineteenth century reclamation in Mishou Bay, Bungo Channel, Southwest Japan

This study reconstructed environmental changes to the seafloor associated with reclamation in Mishou Bay, Bungo Channel, Japan, based on measurements of sediment grain size, organic matter and sulfur contents of surface sediments and data from sediment cores. Grain size within sediment cores from the middle of Mishou Bay decreased from the beginning of the 1800s to the 1900s. In contrast, a grain size profile from the river mouth shows a gradual increase in grain size up through the sediment core. These changes in grain size indicate a decrease in tidal current velocity within the middle of the bay and that the delta system is gradually prograding from the river mouth. Records of organic matter composition and sulfur contents indicate that the effect of the river on seafloor sedimentation became stronger during the nineteenth century. These changes are related to reclamation during the late 1700s and 1800s. The decrease in sea area resulting from reclamation probably led to a decrease in tidal prism and current velocity. It is likely that the increasing effect of river water on sedimentation is associated with reclamation-related progradation of the river delta system.     

The phase boundary between wadsleyite and ringwoodite in Mg2SiO4 determined by in situ X-ray diffraction

The phase boundary between wadsleyite and ringwoodite in Mg₂SiO₄ has been determined in situ using a multi-anvil apparatus and synchrotron X-rays radiation at SPring-8. In spite of the similar X-ray diffraction profiles of these high-pressure phases with closely related structures, we were able to identify the occurrence of the mutual phase transformations based on the change in the difference profile by utilizing a newly introduced press-oscillation system. The boundary was located at ~18.9 GPa and 1,400°C when we used Shim’s gold pressure scale (Shim et al. in Earth Planet Sci Lett 203:729–739, 2002), which was slightly (~0.8 GPa) lower than the pressure as determined from the quench experiments of Katsura and Ito (J Geophys Res 94:15663–15670, 1989). Although it was difficult to constrain the Clapeyron slope based solely on the present data due to the kinetic problem, the phase boundary [P (GPa)=13.1+4.11×10⁻³×T (K)] calculated by a combination of a P–T position well constrained by the present experiment and the calorimetric data of Akaogi et al. (J Geophys Res 94:15671–15685, 1989) reasonably explains all the present data within the experimental error. When we used Anderson’s gold pressure scale (Anderson et al. in J Appl Phys 65:1535–1543, 1989), our phase boundary was located in ~18.1 GPa and 1,400°C, and the extrapolation boundary was consistent with that of Kuroda et al. (Phys Chem Miner 27:523–532, 2000), which was determined at high temperature (1,800–2,000°C) using a calibration based on the same pressure scale. Our new phase boundary is marginally consistent with that of Suzuki et al. (Geophys Res Lett 27:803–806, 2000) based on in situ X-ray experiments at lower temperatures (<1,000°C) using Brown’s and Decker’s NaCl pressure scales.     

Metal contents in Porites corals: Anthropogenic input of river run-off into a coral reef from an urbanized area, Okinawa

In order to monitor pollutants from urban areas to coral reefs, metal contents in Porites coral samples collected from the Hija River mouth and at nearby sites from the estuary were analyzed. The corals were cleaned by oxidative and reductive treatments to effectively eliminate detritus and organic materials. Metal-to-calcium (Me/Ca) ratios in the samples were determined by ICP-MS. Filtered samples of river water were also measured similarly for metal concentrations. The extent of anthropogenic contribution by riverine input was assessed by comparing the Me/Ca values in corals to those of Rukan-sho, an unpolluted coral reef. High riverine inputs of Mn, Cd, Zn and Ag were observed from Me/Ca values in the coral samples. Manganese in the coral samples showed strong dependence on salinity, varying inversely to the distance from terrestrial sources. Considering a lead background of 25.0 nmol/mol measured in the Rukan-sho corals, Pb/Ca in corals of the Hija River estuary that are two and three times higher may indicate lead enrichment in the river mouth. Because Pb is only moderately high in the Hija River water compared to its concentration in surface seawater, lead may have accumulated in the estuarine water and sediments, resulting in an elevated concentration of lead available for coral uptake.     

Groundwater flow in the transition zone between freshwater and saltwater: a field-based study and analysis of measurement errors

The quantification of groundwater flow near the freshwater–saltwater transition zone at the coast is difficult because of variable-density effects and tidal dynamics. Head measurements were collected along a transect perpendicular to the shoreline at a site south of the city of Adelaide, South Australia, to determine the transient flow pattern. This paper presents a detailed overview of the measurement procedure, data post-processing methods and uncertainty analysis in order to assess how measurement errors affect the accuracy of the inferred flow patterns. A particular difficulty encountered was that some of the piezometers were leaky, which necessitated regular measurements of the electrical conductivity and temperature of the water inside the wells to correct for density effects. Other difficulties included failure of pressure transducers, data logger clock drift and operator error. The data obtained were sufficiently accurate to show that there is net seaward horizontal flow of freshwater in the top part of the aquifer, and a net landward flow of saltwater in the lower part. The vertical flow direction alternated with the tide, but due to the large uncertainty of the head gradients and density terms, no net flow could be established with any degree of confidence. While the measurement problems were amplified under the prevailing conditions at the site, similar errors can lead to large uncertainties everywhere. The methodology outlined acknowledges the inherent uncertainty involved in measuring groundwater flow. It can also assist to establish the accuracy requirements of the experimental setup.     

Vertical heat transfer based on direct microstructure measurements in the ice-free Pacific-side Arctic Ocean: the role and impact of the Pacific water intrusion

This study quantifies diapycnal mixing and vertical heat transfer in the Pacific side of the Arctic Ocean, where sea-ice cover has disappeared between July and September in the last few decades. We conducted microstructure measurements in the open water region around the Canada Basin from late summer to fall in 2009 and 2010 using R/V Mirai. In the study domain, the dissipation rate of turbulent kinetic energy, ε, is typically as low level as O(10^?10) W kg^?1, resulting in vertical heat diffusivity of O(10^?7) m² s^?1, which is close to the molecular diffusivity of heat, suggesting comparatively little predominance of mechanical turbulent mixing. An exception is the case at the Barrow Canyon, where the strong baroclinic throughflow generates substantial vertical mixing, producing ε > O(10^?7) W kg^?1, because of the shear flow instability. Meanwhile, in the confluence region, where the warm/salty Pacific water and the cold/fresh Arctic basin water encounter, the micro-temperature profiles revealed a localized enhancement in vertical diffusivity of heat, reaching O(10^?5) m² s^?1 or greater. In this region, an intrusion of warm Pacific water creates a horizontally interleaved structure, where the double-diffusive mixing facilitates vertical heat transfer between the intruding Pacific water and the surrounding basin waters.