Über die Rolle von Mikroorganismen bei der Entstehung und Zerstörung von Lagerstätten

Zusammenfassung Das Forschungsgebiet Geomikrobiologie wird als Grenzgebiet zwischen Mikrobiologie und Geowissenschaften charakterisiert. Allgemeine ökologische und biochemische Voraussetzungen im Bereich der geomikrobiologischen Forschung werden mit Hinweisen auf Möglichkeiten der praktischen Anwendung am Beispiel des geochemischen Kreislaufs von Schwefel und Eisen erörtert.

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In scientific research, geomicrobiology stands between microbiology and geological sciences. General ecological and biochemical conditions are discussed by pointing out the realm and practical applications of geomicrobiology shown on the example of the sulfur and iron cycle.

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Der Text entspricht dem Vortrag der im Februar 1970 vor dem Symposium des Lagerstättenausschusses der GDMB über Ores and Wallrock in Heidelberg gehalten wurde. Diese Arbeit ist Professor Paul Ramdohr zum 80. Geburtstag gewidmet.     

Solar and cosmic X-rays above 7.7 keV

Since its launch on March 8, 1967, the OSO-III has continuously observed solar and cosmic X-rays over the 7.7–210 keV range. The sun emits many impulsive X-ray bursts having fluxes several orders of magnitude above the background level of 8 × 10^–9 ergs(cm²-sec)^–1 at 7.7 keV and characteristic times on the order of 5 min. Ninety-five such events having fluxes >3 × 10^–5 ergs(cm²-sec)^–1 were detected in the period from March 8 to June 15, 1967. The cosmic X-ray source Lupus XR-1 has been observed to have a power law spectral form and no significant time variations over a 40-day period. Upper limits have been obtained on the hard X-ray flux of the peculiar galaxy M 87.     

Artificial spacecraft in hybrid simulations of the quasi-parallel Earth’s bow shock: analysis of time series versus spatial profiles and a separation strategy for Cluster

We construct artificial “software” spacecraft consisting of magnetometers and 3D thermal and energetic ion detectors. Four such spacecraft are “flown” through a 1D simulation of a quasi-parallel shock. We analyze the resulting time series from the spacecraft, and then use the more complete simulational information to evaluate our interpretations based on the limited times series information. The separation strategy used, with two closely spaced spacecraft pairs separated by a large distance, was helpful in the interpretation, since a variety of important processes operate over several different scale lengths. This work highlights the ability to draw inferences about spatially and temporally varying phenomena based on multiple-spacecraft time series data, and suggests that many spacecraft configurations which bear little resemblance to the classic Cluster tetrahedron may be necessary when multiple scale lengths are present.     

Sediment subduction versus accretion around the pacific

Subducting oceanic plates are typically broken by normal faults as they bend downward into subduction zones, usually forming regular patterns of grabens. The faults strike parallel or subparallel to the trench axes and are most commonly 5–10 km in spacing and width. Rupture occurs initially near the outer topographic high and vertical displacement or graben depth increases as the plate descends, the 400 m or more at many trench axes. It is suggested that the grabens provide void spaces within the surface of the subducting plate, below the plane of subduction, into which the trench sediments are tectonically displaced and thus subducted. Around the Pacific, the only regions of apparent fore-arc sediment accretion are where the graben structures are missing or masked by thick sediment deposits. Even in these cases sediment subduction, by inclusion in subducting plate grabens or by other mechanisms, must be invoked to explain the relatively small fore-arc sediment volumes compared to calculated accretion volumes based on historical convergence. Where trench sediment volumes are small compared to the graben volumes the grabens may abrade the leading edge and underside of the overriding plate and subduct the eroded material. It is concluded that sediment subduction is dominant around the Circum-Pacific and that the bending-induced graben structures of the subducting plates are a major factor for sediment subduction and tectonic erosion.     

The new Wallula CO<Subscript>2</Subscript> project may revive the old Columbia River Basalt (western USA) nuclear-waste repository project

A novel CO₂ sequestration project at Wallula, Washington, USA, makes ample use of the geoscientific data collection of the old nuclear waste repository project at the Hanford Site nearby. Both projects target the Columbia River Basalt (CRB). The new publicity for the old project comes at a time when the approach to high-level nuclear waste disposal has undergone fundamental changes. The emphasis now is on a technical barrier that is chemically compatible with the host rock. In the ideal case, the waste container is in thermodynamic equilibrium with the host-rock groundwater regime. The CRB groundwater has what it takes to represent the ideal case.     

Numerical Modeling of Methane Leakage from a Faulty Natural Gas Well into Fractured Tight Formations

Horizontal drilling and hydraulic fracturing have enabled hydrocarbon recovery from unconventional reservoirs, but led to natural gas contamination of shallow groundwaters. We describe and apply numerical models of gas‐phase migration associated with leaking natural gas wells. Three leakage scenarios are simulated: (1) high‐pressure natural gas pulse released into a fractured aquifer; (2) continuous slow leakage into a tilted fractured formation; and (3) continuous slow leakage into an unfractured aquifer with fluvial channels, to facilitate a generalized evaluation of natural gas transport from faulty natural gas wells. High‐pressure pulses of gas leakage into sparsely fractured media are needed to produce the extensive and rapid lateral spreading of free gas previously observed in field studies. Transport in fractures explains how methane can travel vastly different distances and directions laterally away from a leaking well, which leads to variable levels of methane contamination in nearby groundwater wells. Lower rates of methane leakage (≤1 Mcf/day) produce shorter length scales of gas transport than determined by the high‐pressure scenario or field studies, unless aquifers have low vertical permeabilities (≤1 millidarcy) and fractures and bedding planes have sufficient tilt (～10°) to allow a lateral buoyancy component. Similarly, in fractured rock aquifers or where permeability is controlled by channelized fluvial deposits, lateral flow is not sufficiently developed to explain fast‐developing gas contamination (0‐3 months) or large length scales (～1 km) documented in field studies. Thus, current efforts to evaluate the frequency, mechanism, and impacts of natural gas leakage from faulty natural gas wells likely underestimate contributions from small‐volume, low‐pressure leakage events.     

Naïve Simplicity: The Overlooked Piece of the Complexity‐Simplicity Paradigm

Concepts of simplicity and complexity in modeling have been explored in papers, editorials, and talks. The concept is not well understood because there are at least two flavors of simplicity. Modelers envision simplicity (i.e., elegant simplicity) as the sought‐after goal in modeling, but naïve simplicity, which is the focus of this paper, is commonly unrecognized and dangerous. The problem is that naïve or simple ideas are often mistaken for settled science and come with the prospect of being more wrong than right. The concept of the so‐called simplicity cycle, in relation to classical problems of carbon‐14 age and salinity in closed‐basin lakes, is used to illustrate these points. The emerging problems of water‐mosquitoes‐diseases show the value of mapping new problems to the simplicity cycle. Researchers can “know what they do not know” and avoid the dangers of naïve simplicity.     

Modelling groundwater contamination above a nuclear waste repository at Gorleben, Germany

The candidate repository for high-level nuclear waste in the Gorleben salt dome, Germany, is expected to host 8,550 tonnes of uranium in burnt fuel. It has been proposed that 5,440 waste containers be deposited at a depth of about 800?m. There is 260?C280?m of siliciclastic cover sediments above the proposed repository. The potential groundwater contamination in the siliciclastic aquifer is simulated with the TOUGHREACT and TOUGH2-MP codes for a three-dimensional model with 290,435 elements. Two deterministic cases are simulated. The single-phase case considers the transport of radionuclides in the liquid phase only. The two-phase case accounts for hydrogen gas generated by the corrosion of waste containers and release of gaseous C-14. The gas release via a backfilled shaft is assumed to be steady (non-explosive). The simulation period is 2,000,000 years for the single-phase case and 7,000 years for the two-phase case. Only the radioactive dose in the two-phase case is higher than the regulatory limit (0.1?mSv/a).