Review on dating methods: Numerical dating in the quaternary geology of High Asia

Over the past few years, OSL and TCN datings of glacial material from High Asia have come into fashion. To this day, however, these techniques do not permit safe calibration. The intensity of the cosmic ray flux is being modulated by the solar and terrestrial magnetic fields and their secular fluctuations in the past. So far, these variations cannot be converted into the respective local TCN production rates for High Asia. We have reason to believe that the ages that are being calculated despite these uncertainties are generally overestimated. This assessment is supported by conventional radiocarbon dates and above all by the glacial chronology developed independently on the basis of the Quaternary geological method. The strongly emerging evidence for a much more extensive LGM glaciation of High Asia is, however, either being ignored or rejected by many authors, solely on the basis of the above-mentioned uncalibrated datings. This self-conceit based on the “dating fallacy”, as we call it, should be avoided since it goes decidedly against the standards of the scientific method established in Quaternary geology and makes a fundamental scientific discussion impossible.     

Using subsurface metazoan fauna to indicate groundwater–surface water interactions in the Nakdong River floodplain, South Korea

Hydrological interactions between surface water and groundwater (GW) can be described using hydrochemical and biological methods. Surface water–groundwater interactions and their effects on groundwater invertebrate communities were studied in the Nakdong River floodplain in South Korea. Furthermore, the GW-Fauna-Index, a promising new index for assessing the strength of surface-water influence on groundwater, was tested. The influence of surface water on groundwater decreased with increasing depth and distance from the river. While hydrochemistry prevailingly reflected the origin of the waters in the study area (i.e. whether alluvial or from adjacent rock), faunal communities seemed to display an affinity to surface-water intrusion. Fauna reacted quickly to changes in hydrology, and temporal changes in faunal community structure were significantly linked to the hydrological situation in the floodplain. The metazoan faunal community and the GW-Fauna-Index allow a distinction between surface and subsurface waters with varying degrees of exchange. The results indicate that hydrological conditions are reflected by faunal assemblages on a high spatiotemporal resolution, and that surface-water intrusion can be estimated using the GW-Fauna-Index.     

Global change and the biogeochemistry of the North Sea: the possible role of phytoplankton and phytoplankton grazing

Phytoplankton plays a dominant role in shelf biogeochemistry by producing the major part of organic matter. Part of the organic matter will reach the sediment where diagenetic processes like denitrification, apatite formation or burial will remove nutrients from the biogeochemical cycle. In this article current knowledge on the decadal plankton variability in the North Sea is summarized and possible implications of these changes for the biogeochemistry of the North Sea are discussed. Most of the observed interdecadal dynamics seem to be linked to large-scale oceanographic and atmospheric processes. Prominent changes in the North Sea ecosystem have taken place around 1979 and 1988. In general, the phytoplankton color (CPRS indicator of phytoplankton biomass) reached minimum values during the end of the 1970s and has increased especially since the mid 1980s. Changes with a similar timing have been identified in many time series from the North Sea through the entire ecosystem and are sometimes referred to as regime shifts. It is suggested that the impact of global change on the local biogeochemistry is largely driven by the phyto- and zooplankton dynamics during spring and early summer. At that time the extent of zooplankton–phytoplankton interaction either allows that a large part of the new production is settling to the sediment, or that a significant part of the new production including the fixed nutrients is kept within the pelagic system. The origin of the extent of the phytoplankton–zooplankton interaction in spring is probably set in the previous autumn and winter. In coastal areas, both large-scale atmospheric and oceanographic changes as well as anthropogenic factors influence the long-term dynamics. Due to eutrophication, local primary production nowadays still is up to five times higher than during pre-industrial conditions, despite a decreasing trend. Recently, introduced species have strengthened the filter feeder component of coastal ecosystems. Especially in shallow coastal seas like the Wadden Sea, this will enhance particle retention, shift organic matter degradation to the benthic compartment and enhance nutrient removal from the biogeochemical cycle by denitrification or apatite formation.     

Intrusion versus inversion—a 3D density model of the southern rim of the Northwest German Basin

An unsolved problem of regional importance for both the evolution and structure of the Northwest German Basin is the existence or non-existence of the so-called Bramsche Massif. Explaining the nature of this massif and the cause of a related strong, positive Bouguer anomaly (Bramsche Anomaly) is critical. In the study described here, we tested an existing “intrusion model” against a newer “inversion model” in the southern Northwest German Basin. In the intrusion model, the strongly-positive Bouguer anomaly represents the gravity effect of an intrusion at depths between 6 and 10 km. More recent interpretations invoke tectonic inversion rather than intrusion to explain increased burial and the low level of hydrocarbon maturity found in boreholes. We tested these different interpretations by constructing 3D forward density models to 15 km depth. The intrusion model was updated and adjusted to incorporate recent data and we also modelled pre-Zechstein structures using different scenarios. The final model has a very good fit between measured and modelled gravity fields. Based on currently available seismic and structural models, as well as borehole density measurements, we show that the positive Bouguer anomaly cannot be modeled without a high-density, intrusive-like body at depth. However, further in-sight into the crustal structures of the Bramsche region requires more detailed investigations. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Modeling the Permeability Loss of Metallic Iron Water Filtration Systems

Over the past 30 years the literature has burgeoned with in situ approaches for groundwater remediation. Of the methods currently available, the use of metallic iron (Fe⁰) in permeable reactive barrier (PRB) systems is one of the most commonly applied. Despite such interest, an increasing amount of experimental and field observations have reported inconsistent Fe⁰ barrier operation compared to contemporary theory. In the current work, a critical review of the physical chemistry of aqueous Fe⁰ corrosion in porous media is presented. Subsequent implications for the design of Fe⁰ filtration systems are modeled. The results suggest that: (i) for the pH range of natural waters (>4.5), the high volumetric expansion of Fe⁰ during oxidation and precipitation dictates that Fe⁰ should be mixed with a non‐expansive material; (ii) naturally occurring solute precipitates have a negligible impact on permeability loss compared to Fe⁰ expansive corrosion; and (iii) the proliferation of H₂ metabolizing bacteria may contribute to alleviate permeability loss. As a consequence, it is suggested that more emphasis must be placed on future work with regard to considering the Fe⁰ PRB system as a physical (size‐exclusion) water filter device.     

Magmatic evolution of the South Shetland Islands,Antarctica, and implications for continental crust formation

Lavas from the South Shetland Islands volcanic arc (northern Antarctic Peninsula) have been investigated in order to determine the age, petrogenesis and compositional evolution of a long-lived volcanic arc constructed on 32-km-thick crust, a thickness comparable with average continental crust. New ⁴⁰Ar–³⁹Ar ages for the volcanism range between 135 and 47 Ma and, together with published younger ages, confirm a broad geographical trend of decreasing ages for the volcanism from southwest to northeast. The migration pattern breaks down in Palaeogene time, with Eocene magmatism present on both Livingston and King George islands, which may be due to a change in both subduction direction and velocity after c. 60 Ma. The lavas range from tholeiitic to calc-alkaline, but there is no systematic change with age or geographic location. The compositions of lavas from the north-eastern islands indicate magma generation in a depleted mantle wedge with relatively low Sr and high Nd isotopic compositions and low U/Nb, Th/Nd and Ba/Nb ratios that was metasomatized by hydrous fluids from subducted basaltic oceanic crust. Lavas from the south-western islands show an additional sedimentary influence most likely due to fluid release from subducted sediments into the mantle wedge. Although magmatic activity in the South Shetland arc extended over c. 100 m.y., there is no evolution towards more enriched or evolved magmas with time. Few South Shetland arc lavas are sufficiently enriched with incompatible elements to provide a potential protolith for the generation of average continental crust. We conclude that even long-established subduction zones with magmatic systems founded on relatively thick crust do not necessarily form continental crustal building blocks. They probably represent only the juvenile stages of continental crust formation, and additional re-working, for example during subsequent arc-continental margin collision, is required before they can evolve into average continental crust.     

Uncertainties of geochemical modeling during CO<Subscript>2</Subscript> sequestration applying batch equilibrium calculations

One of the uncertainties in the field of carbon dioxide capture and storage (CCS) is caused by the parameterization of geochemical models. The application of geochemical models contributes significantly to calculate the fate of the CO₂ after its injection. The choice of the thermodynamic database used, the selection of the secondary mineral assemblage as well as the option to calculate pressure dependent equilibrium constants influence the CO₂ trapping potential and trapping mechanism. Scenario analyses were conducted applying a geochemical batch equilibrium model for a virtual CO₂ injection into a saline Keuper aquifer. The amount of CO₂ which could be trapped in the formation water and in the form of carbonates was calculated using the model code PHREEQC. Thereby, four thermodynamic datasets were used to calculate the thermodynamic equilibria. Furthermore, the equilibrium constants were re-calculated with the code SUPCRT92, which also applied a pressure correction to the equilibrium constants. Varying the thermodynamic database caused a range of 61% in the amount of trapped CO₂ calculated. Simultaneously, the assemblage of secondary minerals was varied, and the potential secondary minerals dawsonite and K-mica were included in several scenarios. The selection of the secondary mineral assemblage caused a range of 74% in the calculated amount of trapped CO₂. Correcting the equilibrium constants with respect to a pressure of 125 bars had an influence of 11% on the amount of trapped CO₂. This illustrates the need for incorporating sensitivity analyses into reaction pathway modeling.     

How to assess hydromorphology? A comparison of Ukrainian and German approaches

Recently, the Ukrainian Western Bug water authorities developed a national field survey to assess the quality of river habitats. The Ukrainian government already cooperates with EU member states along transboundary rivers and also orientates itself towards the European Water Framework Directive (WFD). As a future application for EU membership is feasible, the water authorities started to implement WFD criteria into their national survey schemes including the assessment of rivers’ hydromorphology. This article compares two different hydromorphological survey methods to identify similarities and differences of the classification approaches with regard to the conformity of obtained outputs with the WFD demands. The field surveys, the Ukrainian (UA-FS) and the German (LAWA-FS), were applied in parallel on 14 river sections along the Western Bug River and parts of its tributaries. Results show a wide range of conformity, but also several differences between and gaps within all methods. The UA-FS generally lacks the idea of reference condition in rivers’ hydromorphology and the definition of different stream types or near-natural land uses. The UA-FS and the LAWA-FS approaches are similar with respect to their incorporated compartments and most main parameters, but differ in definition and interpretation of specific functional units and single parameters. Greatest similarities down to single parameters exist in aspects of land use, bank vegetation, currents diversity, and within-stream variation of water depths. Differences include the assessment and interpretation of lateral erosion, sinuosity, type and depth of profile, substrate diversity, as well as special structures of bank and riverbed. Overall, the LAWA-FS is more conservative in its rating than the UA-FS. Still, UA-FS can be regarded as an important improvement for a systematic and reliable monitoring of river hydromorphology in the Ukraine that will help to successfully engage with both the integrated water resources management and the WFD harmonisation process in the future.     

Modeling, parameterization and evaluation of monitoring methods for CO2 storage in deep saline formations: the CO2-MoPa project

Capture and geological sequestration of CO₂ from large industrial sources is considered a measure for reducing anthropogenic emissions of CO₂ and thus mitigating climate change. One of the main storage options proposed are deep saline formations, as they provide the largest potential storage capacities among the geologic options. A thorough assessment of this type of storage site therefore is required. The CO₂-MoPa project aims at contributing to the dimensioning of CO₂ storage projects and to evaluating monitoring methods for CO₂ injection by an integrated approach. For this, virtual, but realistic test sites are designed geometrically and fully parameterized. Numerical process models are developed and then used to simulate the effects of a CO₂ injection into the virtual test sites. Because the parameterization of the virtual sites is known completely, investigation as well as monitoring methods can be closely examined and evaluated by comparing the virtual monitoring result with the simulation. To this end, the monitoring or investigation method is also simulated, and the (virtual) measurements are recorded and evaluated like real data. Application to a synthetic site typical for the north German basin showed that pressure response has to be evaluated taking into account the layered structure of the storage system. Microgravimetric measurements are found to be promising for detecting the CO₂ phase distribution. A combination of seismic and geoelectric measurements can be used to constrain the CO₂ phase distribution for the anticline system used in the synthetic site.     

Preliminary Interlaboratory Trial for ISO/DIS 12010: Determination of Short Chain Polychlorinated Alkanes (SCCP) in Water

A first preliminary interlaboratory trial was planned to prepare ISO/DIS 12010: Water quality – determination of short chain polychlorinated alkanes (SCCP) in water – method using GC/MS and electron capture negative ionisation (ECNI). The task was to determine the sum of short chain polychlorinated n‐alkanes with carbon chain lengths of C₁₀–C₁₃ and a chlorine content between 49 and 67% in water by GC‐ECNI‐MS and quantification by multiple linear regression described in ISO/DIS 12010 as the compulsory method. Distributed samples were obtained from a real water extract spiked with a target concentration of 0.4 µg/mL sum of SCCP, i.e. the environmental quality target level according to the Water Framework Directive. The interlaboratory trial included the calibration, a column chromatographic clean up, a concentration step and an integration of chromatographic unresolved humps as well as the quantification with multiple linear regression. Reproducibility standard deviations between 21.5 and 22.9% were achieved by 17 participating laboratories from four countries. The method outlined no significant difference of the results between the standard solution and a real water matrix extract. On the basis of this succeeded preliminary interlaboratory trial the final interlaboratory trial for validation of ISO 12010 was prepared in autumn 2010.