A 40 ka record of temperature and permafrost conditions in northwestern Europe from noble gases in the Ledo‐Paniselian Aquifer (Belgium)

The Ledo‐Paniselian Aquifer in Belgium offers unique opportunities to study periglacial groundwater recharge during the Last Glacial Maximum (LGM), as it was located close to the southern boundary of the ice sheets at that time. Groundwater residence times determined by ¹⁴C and ⁴He reveal a sequence of Holocene and Pleistocene groundwaters and a gap between about 14 and 21 ka, indicating permafrost conditions which inhibited groundwater recharge. In this paper, a dataset of noble gas measurements is used to study the climatic evolution of the region. The derived recharge temperatures indicate that soil temperatures in the periods just before and after the recharge gap were only slightly above freezing, supporting the hypothesis that permafrost caused the recharge gap. The inferred glacial cooling of 9.5°C is the largest found so far by the noble gas method. Yet, compared to other palaeoclimate reconstructions for the region, recharge temperatures deduced from noble gases for the cold periods tend to be rather high. Most likely, this is due to soil temperatures being several degrees higher than air temperatures during periods with extended snow cover. Thus the noble‐gas‐derived glacial cooling of 9.5°C is only a lower limit of the maximum cooling during the LGM. Some samples younger than the recharge gap are affected by degassing, possibly related to gas production during recharge in part of the recharge area, especially during times of melting permafrost. The findings of this study, such as the occurrence of a recharge gap and degassing related to permafrost and its melting, are significant for groundwater dynamics and geochemistry in periglacial areas. Copyright © 2010 John Wiley & Sons, Ltd.     

Determination of radionuclides in water at uranium mining remediation – a comparison of analytical methods

The corporate purpose of Wismut GmbH is to decommission its former mining holdings and to rehabilitate the landscape and the environment. Sample taking and analysing the value of contaminants are necessary steps for the remediation of waste rock piles, the recycling of contaminated areas, controlled flooding of uranium mines. Main emphasis lies on the determination of heavy metals and radionuclides of natural decay chains of U‐238 and U‐235. Yearly about 60 000…70 000 determinations of radionuclides in waters were done. Facing this high output of determinations it is a permanent task for laboratory and quality management to ask: Are the results of different methods comparable to each other? Is there a preferred analytical technology? Which matrix influences exist? and What about the analytical costs? Answers to these important questions are given in this report. Summarizing our investigations done in the last few years it is possible to say that – by using different analytical methods the results of radionuclides in water samples (surface or groundwater) are comparable, – a not negligible influence of Ra‐223, Ra‐224 and Ra‐228 may exist by using the DIN 38404 C18 method to determine Ra‐226, – a preferred method cannot be defined, – the choice of the analytical method should include analytical questions (the sample matrix, the occurrence of other disturbing radionuclides, the necessary detection limit) and economical questions (costs, other parameters to be determined).     

Calibration/Data Assimilation Approach for Integrating GRACE Data into the WaterGAP Global Hydrology Model (WGHM) Using an Ensemble Kalman Filter: First Results

We introduce a new ensemble-based Kalman filter approach to assimilate GRACE satellite gravity data into the WaterGAP Global Hydrology Model. The approach (1) enables the use of the spatial resolution provided by GRACE by including the satellite observations as a gridded data product, (2) accounts for the complex spatial GRACE error correlation pattern by rigorous error propagation from the monthly GRACE solutions, and (3) allows us to integrate model parameter calibration and data assimilation within a unified framework. We investigate the formal contribution of GRACE observations to the Kalman filter update by analysis of the Kalman gain matrix. We then present first model runs, calibrated via data assimilation, for two different experiments: the first one assimilates GRACE basin averages of total water storage and the second one introduces gridded GRACE data at \(5^\circ\) resolution into the assimilation. We finally validate the assimilated model by running it in free mode (i.e., without adding any further GRACE information) for a period of 3 years following the assimilation phase and comparing the results to the GRACE observations available for this period.     

Imaging the Mariánské Lázně Fault (Czech Republic) by 3-D ground-penetrating radar and electric resistivity tomography

Geodynamic activity in the area of West Bohemia is typified by the occurrence of earthquake swarms, Quaternary volcanism and high flux of mantle-derived CO₂. The highest swarm activity occurs beneath the eastern edge of the Cheb basin, which is delineated by the NW-SE trending morphologically pronounced Mariánské Lázn?? Fault (MLF) controlling the formation of the basin. The previous trenching survey across the MLF zone has identified several fault strands with possible Quaternary activity. In this paper we present the results of the geophysical survey focused to trace the faults signatures in geophysical sections and to build an image of near surface tectonics. The method of electric resistivity tomography (ERT) along two profiles parallel to the trench identified a strong resistivity contrast between the bodies of sandy gravels in the middle and conductive clayey sands to the west and weathered crystalline basement to the east. The 2-D ground penetration radar (GPR) sections show direct correlation of reflections with lithological boundaries identified in the trench. As expected, the GPR signal amplitudes increase with the resistivities found in the ERT sections. Two of the four faults identified in the trench are indicated in the resistivity and GPR sections. A 3-D GPR measurement has identified a spot of high amplitudes elongated parallel to the MLF trend, which coincides with the high resistivity body. To improve the signal-to-noise ratio of the time slices we stacked the GPR time slices within vertically homogeneous blocks. This provided a contrast image of the sand-gravel body including its boundaries in three dimensions. The detailed analysis of the 3-D GPR cube revealed additional fault that limits the highly reflective sands and appears to be offset by another younger fault. Our results suggest a complex fault pattern in the studied area, which deserves a further study.     

Towards an Open Information Infrastructure for Disaster Research and Management: Data Management and Information Systems Inside DFNK

The development of new and better methods for preventing and managing natural disasters requires a variety of different data sets, covering the range from referenced data, e.g. topographic data and digital elevation models, to various kinds of thematic data, e.g. data about soil, vegetation and land usage as well as monitoring data like precipitation and water levels. So a well-organised data and information management and the implementation of a modern processing environment to acquire, store, analyse and visualise data were decisive for the success of the German Research Network Natural Disasters (DFNK). An information infrastructure was established to support data management and information flows inside the network. A web-based portal offers general information to the public and internal documents, data and software tools to the project community. A catalog service allows the overview of existing but distributed data scombined with flexible data retrieval. Based on internet technology and global standards these concepts contribute to a superior information infrastructure and finally substantiate to the development of Spatial Data Infrastructures (SDI). SDIs aim is to improve availability and usability of spatial data for the manifold application areas. Disaster management is one field depending on a very high level on high-quality data equipment, and on a working SDI.     

An integrated suspended sediment transport monitoring and analysis concept

A new integrated suspended sediment monitoring strategy applying direct and indirect technologies is presented.Optical sensors continuously record the turbidity at one point in the channel cross section close to the river bank and are calibrated by water samples taken close to the sensor.Additionally measurements are performed to establish the distribution of suspended sediment in a cross section（bottle samples combined with acoustic devices）.Using correction factors（probe and cross-sectional factor） these monitoring methods are combined and it is,thus,possible to fully document the temporal and spatial variability of the suspended sediment transport and to estimate the suspended sediment load for certain time periods.This monitoring strategy was implemented at various measurement sites in Austria as well as at the Hainburg Road Bridge site on the Danube River.It has already been successfully applied for three years at this measurement site and suspended sediment loads during high discharges up to a 15 year flood event have been monitored.To evaluate the new monitoring methods the results were compared with load estimation methods found in the literature including averaging and ratio estimators as well as rating curves.The results prove that with the new methodology,the temporal variability of the suspended sediment transport can be detected more accurately compared with the other methods.They also demonstrate that the additional consideration of the spatial distribution of the suspended sediment concentration in the cross section is crucial as the mean concentration in the cross section can significantly exceed the concentration near the banks,especially at large rivers like the Danube River.     

A numerical model of exhumation of the orogenic lower crust in the Bohemian Massif during the Variscan orogeny

We present a numerical model of the main phase (370?C335 Ma) of the Variscan orogeny in the central part of the Bohemian Massif. The crustal deformation in our model is driven by radiogenic heating in the felsic lower crust, the lateral contraction of the Moldanubian domain due to convergence with the Saxothuringian plate (in the early stage of orogeny), and the indentation of the Brunovistulian basement into the weakened orogenic root (in the late stage). Our model explains the main geological events inferred from the geological record in the Moldanubian domain: formation of the orogenic plateau and onset of sedimentation at about 345 Ma, rapid exhumation of the orogenic lower crust at about 340 Ma and subsurface flow of crustal material (?? 335 Ma and later). The results of our modeling suggest that delamination of the lithosphere, often invoked to explain the high temperature metamorphism in the orogenic lower crust of the Bohemian Massif, is not the only physical mechanism which can transfer a sufficient amount of heat to the crust to trigger its overturn.     

Beeinflusst die Strukturgüte von Fließgewässern das Vorkommen von Makrophyten?

Does the Structural Quality of Running Waters Affect the Occurrence of Macrophytes? The morphological structure plays, besides e.g. nutrient concentration, an important role for the integrated assessment of running waters. This paper focuses on the relationship between structural quality and macrophyte vegetation. During summer 2000 structural quality according to LAWA, macrophyte vegetation, and selected habitat parameters were recorded in 135 mapping sections in running waters in Southern Germany. In streams of high structural diversity, generally higher species richness is expected than in rivers of low diversity of habitats. However, no significant differences in macrophyte species richness were detected between different classes of structural quality. In contrast, bryophytes alone showed a significant decrease in species richness with degradation of structural quality. The number of species of other macrophytes increased, respectively. The relationship between occurrence of macrophytes, structural quality, and other environmental variables was analysed using canonical correspondence analysis. Rivers of high structural quality mostly showed high flowing velocities and were heavily shaded. These environmental conditions, which characterize river types of mountainous regions, were predominantly tolerated by bryophytes. Vascular plants and charophytes generally prefer slowly flowing and unshaded habitats. River types exhibiting these environmental conditions often are more influenced by human activities and are more structurally degraded, respectively. With respect to these fundamental differences between river types, species richness of macrophytes and class of structural quality are not correlated when all types of rivers are taken into account. Type‐specific ecomorphological parameters, which conceal the differences in species richness caused by structural quality, are discussed. Structural degraded rivers can provide good environmental conditions for vascular plants and charophytes. To predict macrophyte species richness from structural quality, a differentiation of river types is essential.     

An equation of state for roedderites, (K,Na)2Mg5[Si12O30], based on Knudsen cell mass spectrometry and synthesis of eifelite-roedderite crystalline solutions

Knudsen cell mass spectrometry has been applied to obtain activity (a _i) vs composition (X _i) data for 18 synthetic roedderites. (K, Na)₂Mg₅Si₁₂O₃₀, at temperatures between 900° and 1100° C. The samples were synthesized at 800° C and 1 kbar P _{H 2}O and characterized by X-ray powder diffractometry (XRD) and electron probe microanalysis (EPMA) prior to mass spectrometric activity measurement. The experimental a _i-X _i data have been smoothed, assuming for now the simplest possible model of a two-site K-Na mixing for this binary crystalline solution. Using the Margules formalism, and expressing the results in terms of one atom of K-Na mixing, the tentative equation of state is: W _G [J/mol] =-8704 -0.0067 · P, with P given in bar. The temperature-dependence of W _G could not be resolved due to its large uncertainty on the order of 2.8 kJ/mol. A more rigorous thermodynamic model for roedderites will have to be deferred until information on temperature-dependent K-Na disordering becomes available. Besides roedderites, single-phase eifelite-roedderite crystalline solutions have also been snythesized for the first time. They show a symmetric positive excess volume of mixing, with W _V [J/bar·mol]=0.1064±0.0021.     

The Pfitsch-Mörchner Basin,an example of the post-Variscan sedimentary evolution in the Tauern Window (Eastern Alps)

A review of post-Variscan metasedimentary and metavolcanic successions in the western Tauern Window is presented. U/Pb – datations of zircons in metavolcanic rocks reveal ages between 309 and 280 Ma. Deposition of grey conglomerates and black pelites started before 309 Ma in the northernmost basin of the Tauern, the Riffler-Schönach basin. In the more central Pfitsch-Mörchner basin, the onset of conglomerate sedimentation can be dated into the time span between 293 and 280 Ma. The Pfitsch and Windtal Formations are newly defined. The basins were filled with up to 1 km of mainly continental clastics until Early Triassic. Short marine ingressions in Middle- and Late Triassic times flooded only basinal parts of the area where we suppose a more or less continuous sedimentation until the Late Jurassic. Only the Hochstegen Marble documents a nearly complete submergence in the area of the Tauern Window. In spite of the metamorphic overprint, the tentative interpretations of the sedimentary facies give a reasonable picture and allow correlations to nonmetamorphic areas in South Germany or the External Massifs of Eastern Switzerland.