Polyphase scheelite and stanniferous silicates in a W-(Sn) skarn close to Felbertal tungsten mine,Eastern Alps

Mineralogy and Petrology - The scheelite exploration target Messelingscharte (Eastern Tyrol, Austria) is located in vicinity of the world-class Felbertal tungsten deposit. W-(Sn) mineralisation...     

Sustainable Capture: Concepts for Managing Stream‐Aquifer Systems

Most surface water bodies (i.e., streams, lakes, etc.) are connected to the groundwater system to some degree so that changes to surface water bodies (either diversions or importations) can change flows in aquifer systems, and pumping from an aquifer can reduce discharge to, or induce additional recharge from streams, springs, and lakes. The timescales of these interactions are often very long (decades), making sustainable management of these systems difficult if relying only on observations of system responses. Instead, management scenarios are often analyzed based on numerical modeling. In this paper we propose a framework and metrics that can be used to relate the Theis concepts of capture to sustainable measures of stream‐aquifer systems. We introduce four concepts: Sustainable Capture Fractions, Sustainable Capture Thresholds, Capture Efficiency, and Sustainable Groundwater Storage that can be used as the basis for developing metrics for sustainable management of stream‐aquifer systems. We demonstrate their utility on a hypothetical stream‐aquifer system where pumping captures both streamflow and discharge to phreatophytes at different amounts based on pumping location. In particular, Capture Efficiency (CE) can be easily understood by both scientists and non‐scientist alike, and readily identifies vulnerabilities to sustainable stream‐aquifer management when its value exceeds 100%.     

Atmospheric Mercury Concentrations from Several Observatory Sites in the Northern Hemisphere

In an effort to investigate both large-scale (spatial) and short/long-term (temporal) distribution characteristics of atmospheric mercury, we have combined and analyzed the Hg concentration data sets collected continuously by four different scientific groups for the areas and periods covering (1) America (three sites near the Canadian Great Lakes (CGL): 1997–2000), (2) Asia (Seoul, Korea (SEL): 1997–2002), (3) Arctic (Alert, Canada (ALT): 1995–2001), and (4) Europe (Mace Head, Ireland (MH): 1996–2002). The mean concentrations of Hg data from those widely dispersed monitoring stations were computed to be (1) 1.58 ± 0.23, 1.69 ± 0.32, and 1.93 ± 0.44 (three sites in CGL), (2) 5.06 ± 2.46 ng m^–3 (SEL), (3) 1.55 ± 0.41 (ALT), and (4) 1.76 ± 0.31 (MH). Intersite relationships were investigated among all different stations using the data groups divided into different temporal intervals. The analysis of diurnal variation patterns of Hg indicated differences in regional source/sink characteristics, with increasing amplitudes of variability toward areas under the strong influence of anthropogenic sources. When the analysis was made over different seasons, the patterns contrasted greatly between the Arctic and the other areas. It was found that the relative enhancement of Hg concentrations was dominant during winter/spring in most areas due to direct or indirect influences of anthropogenic emissions. However, the pattern for the Arctic area was distinguished pronouncedly from others with the spring minimum and summer maximum both of which reflect the potent effects of mercury depletion phenomenon (MDP). By contrast, no long-term trend, either being an increase or decrease, was evident from any of the stations during each respective study period. Although our initial attempts to examine the distribution characteristics of Hg analyzed by different scientific groups were successful, we feel that these efforts should be continued further to extend the compatibility of the global database of Hg.     

Carbon and Oxygen Isotopic Composition of Surface‐Sediment Carbonate in Bosten Lake (Xinjiang,China) and its Controlling Factors

Bosten Lake is a mid-latitude lake with water mainly supplied by melting ice and snow in the Tianshan Mountains. The depositional environment of the lake is spatially not uniform due to the proximity of the major inlet and the single outlet in the western part of the lake. The analytical results show that the carbon and oxygen isotopic composition of recent lake sediments is related to this specific lacustrine depositional environment and to the resulting carbonate mineralogy. In the southwestern lake region between the Kaidu River inlet and the Kongqi River outlet, carbon isotope composition (δ13C) values of the carbonate sediment (?1‰ to ?2‰) have no relation to the oxygen isotope composition of the carbonate (δ18O) values (?7‰ to ?8‰), with both isotopes showing a low variability. The carbonate content is low (<20%). Carbonate minerals analyzed by X-ray diffraction are mainly composed of calcite, while aragonite was not recorded. The salinity of the lake water is low in the estuary region as a result of the Kaidu River inflow. In comparison, the carbon and oxygen isotope values are higher in the middle and eastern parts of the lake, with δ13C values between approximately +0.5‰ and +3‰, and δ18O values between ?1‰ and ?5‰. There is a moderate correlation between the stable oxygen and carbon isotopes, with a coefficient of correlation r of approximately 0.63. This implies that the lake water has a relatively short residence time. Carbonate minerals constitute calcite and aragonite in the middle and eastern region of the lake. Aragonite and Mg–calcite are formed at higher lake water salinity and temperatures, and larger evaporation effects. More saline lake water in the middle and eastern region of the lake and the enhanced isotopic equilibrium between water and atmospheric CO2 cause the correlating carbon and oxygen isotope values determined for aragonite and Mg–calcite. Evaporation and biological processes are the main reasons for the salinity and carbonate mineralogy influence of the surface-sediment carbonate in Bosten Lake. The lake water residence time and the CO2 exchange between the atmosphere and the water body control the carbon and oxygen isotope composition of the carbonate sediment. In addition, organic matter pollution and decomposition result in the abnormally low carbon isotope values of the lake surface-sediment carbonate.     

The Sun at 8.5 mm wavelength — results of observations with high angular resolution

High resolution single dish observations of the solar radio emission with the Effelsberg 100-m telescope at 8.5 mm wavelength (antenna beam width is 31) show a good correlation of small active regions, seen in quiet Sun areas, associated with the longitudinal magnetic fields, but not with structures seen in H light.Some characteristics of these 8.5 mm structures, such as diameter and temperature, point to a correlation with supergranular cells. Although the lifetime of these structures is longer than several hours, weak intensity variations within a time scale of minutes could be recorded. From the observational results it was possible to derive roughly an energy dissipation rate for the 8.5 mm structures. This value is a factor of 100 higher than that obtained earlier at 2.8 cm wavelength in a similar manner.A center-to-limb variation at 8.5 mm, especially a limb brightening, could not be detected.     

Benefits of receiver clock modeling in code-based GNSS navigation

Due to the limited frequency stability and poor accuracy of typical quartz oscillators built-in GNSS receivers, an additional receiver clock error has to be estimated in addition to the coordinates. This leads to several drawbacks especially in kinematic applications: At least four satellites in view are needed for navigation, high correlations between the clock estimates and the up-coordinates. This situation can be improved distinctly when connecting atomic clocks to GNSS receivers and modeling their behavior in a physically meaningful way (receiver clock modeling). Recent developments in miniaturizing atomic clocks result in so-called chip-scale atomic clocks and open up the possibility of using stable atomic clocks in GNSS navigation. We present two different methods of receiver clock modeling, namely in an extended Kalman filter and a sequential least-squares adjustment for code-based GNSS navigation using three different miniaturized atomic clocks. Using the data of several kinematic test drives, the benefits of clock modeling for GPS navigation solutions are assessed: decrease in the noise of the up-coordinates by up to 69 % to 20 cm level, decrease in minimal detectable biases by 16 %, and elimination of spikes and subsequently decrease in large position errors (35 %). Hence, a more robust position is obtained. Additionally, artificial partial satellite outages are generated to demonstrate position solutions with only three satellites in view.     

Seasonal changes in the soil moisture distribution around bare rock outcrops within a karst rocky desertification area (Fuyuan County,Yunnan Province,China)

The spatial and temporal soil moisture distribution is an important control on surface ecological processes in areas with rock outcrops resulting from karst rocky desertification (KRD). To explore the local effects of bare rocks within different seasons, soil moisture was measured in a KRD region (Fuyuan County, Yunnan Province, southwest China) at different depths and in different directions and distances from rock outcrops in both the dry and the wet seasons. The soil moisture north and east of the rocks was higher compared to the other directions and to the control plot. This effect is attributed to the shading by the rocks. The shading effect is evident in all seasons but more pronounced in the dry season. In the wet season, the directional dependency is restricted to the surface layer and the increase in soil moisture with depth is more pronounced around the rocks than at the control plot. This is attributed to precipitation-induced runoff from the rock outcrops infiltrating into the deeper layers at the rock–soil interface. These findings suggest the redistribution of water in the wet season and the spatial variation of evapotranspiration in the dry season are factors controlling the local soil moisture pattern around the rock outcrops.