Regulation of bacterial sulfate reduction and hydrogen sulfide fluxes in the central namibian coastal upwelling zone

The coastal upwelling system off central Namibia is one of the most productive regions of the oceans and is characterized by frequently occurring shelf anoxia with severe effects for the benthic life and fisheries. We present data on water column dissolved oxygen, sulfide, nitrate and nitrite, pore water profiles for dissolved sulfide and sulfate,³⁵S-sulfate reduction rates, as well as bacterial counts of large sulfur bacteria from 20 stations across the continental shelf and slope. The stations covered two transects and included the inner shelf with its anoxic and extremely oxygen-depleted bottom waters, the oxygen minimum zone on the continental slope, and the lower continental slope below the oxygen minimum zone. High concentrations of dissolved sulfide, up to 22 mM, in the near-surface sediments of the inner shelf result from extremely high rates of bacterial sulfate reduction and the low capacity to oxidize and trap sulfide. The inner shelf break marks the seaward border of sulfidic bottom waters, and separates two different regimes of bacterial sulfate reduction. In the sulfidic bottom waters on the shelf, up to 55% of sulfide oxidation is mediated by the large nitrate-storing sulfur bacteria, Thiomargarita spp. The filamentous relatives Beggiatoa spp. occupy low-O₂ bottom waters on the outer shelf. Sulfide oxidation on the slope is apparently not mediated by the large sulfur bacteria. The data demonstrate the importance of large sulfur bacteria, which live close to the sediment-water interface and reduce the hydrogen sulfide flux to the water column. Modeling of pore water sulfide concentration profiles indicates that sulfide produced by bacterial sulfate reduction in the uppermost 16 cm of sediment is sufficient to account for the total flux of hydrogen sulfide to the water column. However, the total pool of hydrogen sulfide in the water column is too large to be explained by steady state diffusion across the sediment-water interface. Episodic advection of hydrogen sulfide, possibly triggered by methane eruptions, may contribute to hydrogen sulfide in the water column.     

Zur geoelektrischen Untersuchung der Zementverpressungen von Staumauern und Staudämmen

Zusammenfassung a) Es werden die Ergebnisse eines Messverfahrens besprochen, dessen Aufgabe die überprüfung des Injektionserfolges ist. -b) Das Verfahren wurde an verschiedenen Baustellen bei sehr verschiedenen Bodenverhältnissen eingesetzt. Die Ergebnisse werden mitgeteilt. Es war in vielen Fällen möglich, die durch elektrische Messungen begründete Vorhersage mit den mechanisch gewonnenen Befunden zu vergleichen. Auch diese Ergebnisse werden mitgeteilt. -c) Im Zuge dieser Untersuchungen wurde die elektrische Mischtheorie experimentell untersucht und ein geoelektrisches Verfahren zur Bestimmung desK-Wertes entwickelt. -d) Die richtige Verbindung der elektrischen und mechanischen Messverfahren ermöglicht ein weit genaueres Studium des Injektionsvorganges und eine viel richtigere Beurteilung des Injektionserfolges als die bisher übliche blosse Wasserverpressung.

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Summary The results of a geoelectrical method of measurement for controlling cement injections are discussed. This method was practised already at several building-sites e. g. at building-sites in the bare and rocky Alpine region (Carso) of Yugoslavia. By means of this geoelectrical method the volumetric distribution of the injection mass can be controlled and therefore also the quantity discharged from the injection volume. In many cases the results obtained by geoelectrical measurements were later mechanically controlled. These results show the usefulness of this method. By means of this geoelectrical method more precise results may be obtained than by water pressure which method was used exclusively before. In this paper the fundamentals of this method and the geoelectrical mixture theory are discussed. Then the results obtained at the building-sites of Kaprun (Austria) and of Lokvarka and Cetina (Yugoslavia) are compared.

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Nach Referaten auf der Vierten Allgem. Tagung derSocietà Italiana di Geofisica e Meteorologia in Genova (5.–8. April 1956).

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Der Verfasser dankt allen, die ihm bei der Durchführung der Untersuchungen geholfen haben und insbesondere seinen Mitarbeitern. Besonderen Dank spricht er den Herren der Tauernkraftwerke A. G. und Geofizika in Zagreb aus.     

Einige Probleme der geoelektrischen Bodenverfestigung

Zusammenfassung 1. Eine Verfestigung über die «kritische Zeit» hinaus ist unwirtschaftlich. Daher sollten Elektroden verwendet werden, bei deren Anwendung die kritische Zeit sehr gross ist, oder die leicht verlegt werden können, wenn die kritische Zeit abgelaufen ist. Bei Stabelektroden geschieht dies durch Umstecken. Man kann aber auch Rollenelektroden verwenden, die über das zu verfestigende Volumen hinwegrollen. Dies ist allerdings nur dann zulässig, wenn nur eine ziemlich schwache Oberflächenschichte zu verfestigen ist. — 2. Um die günstigste Verfestigungsleistung zu erreichen, muss die Elektrodenspannung und der Elektrodenstrom den bodenphysikalischen Bestimmungsstücken richtig angepasst werden. — 3. Die geoelektrische Entwässerung ist nur dann anwendbar, wenn der Boden einen Mindestwassergehalt hat. Dieser ist durch die Kornverteilungskurve bestimmt. — 4. Durch die geoelektrische Behandlung des Bodens wird das Verhältnis zwischen Raumgewicht und Wassergehalt verändert und daher die Verfestigungskurve verformt.

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Summary In this article some geoelectrical problems of soil consolidation are discussed. The principal part of the electrical power is effective only near the electrodes. The resistance in this zone rises quickly during the course of time. After a «critical time» it becomes so high that no further consolidation of soil can be achieved. This time depends on the number, form and configuration of the electrodes. Rollings and plates are preferable to sticks. The voltage of electrodes has to be adapted to the specific resistivity of soil. The content of water of the soil can be reduced by electric means only if it surmounts a certain lowest value. By this geoelectrical consolidation the moisture-density relationship (Proctor-diagram) is deformed.

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Nach einem Vortrag auf der 2. Tagung der «Società Italiana di Geofisica e Meteorologia» in Genova, 23–25 April 1954.     

Discussion of the formation of major positive and negative ions up to the 50 km level

Summary An attempt has been made to predict the nature of positive and negative ions up to a level of 50 km. Considerable progress has been made in recent years in the understanding of the mechanism of formation of small ions at ground levels and the altitude profile of ions presented here for the first time will rely on this previous work. It should be understood that this discussion as related to negative ions is tentative due to the fact that many more rate constants are needed to provide a quantitative answer.It is also attempted to postulate the existence of condensation embryos formed by gas-to-particle conversion induced by radiation and chemical reaction throughout the atmosphere. As is known at the present time, this gas-to-particle conversion takes place in the troposphere and is also responsible for the so-called Junge layer at around 20 km. However, we have reason to believe that the formation of condensation embryos must take place to some degree at any altitude being considered here.     

Negative ions in air-like gas mixtures

Summary The nature of negative ions in an air-like gas mixture containing 300 ppm²) of carbon dioxide and 1 ppm of water has been investigated using a drift tube working at atmospheric pressure and interfaced with a quadrupole mass spectrometer. It was found that the most dominant ion under equilibrium conditions is CO₄–·(H₂O).

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Zusammenfassung Mittels einer Kombination eines Beweglichkeits-Spektrometers und eines Vierpol-Massenspektrometers, ersteres im Bereich des normalen Luftdrucks arbeitend, wurde die Natur der negativen Ionen in einer luftähnlichen Gasmischung untersucht. Die Gasmischung enthielt 300 ppm²) Kohlendioxid und 1 ppm Wasserdampf. Es wurde festgestellt, dass unter Gleichgewichts-bedingungen das vorherrschende Ion die Formel CO₄–·(H₂O) hat.

     

The free jet as a means to improve water quality: Destratification and oxygen enrichment

Rivers, lakes, and coastal waters are chaotic systems — physical, chemical, and biological parameters influence their development. Each parameter itself is influenced by the system. Human interaction has led to fast eutrophication. Oxygen input and artificial mixing have been considered as tools to overcome the biggest problems of fish kills, algal blooms, and bad odour. The favoured technology for destratification and oxygen input so far is the bubble curtain. This technology has been applied successfully in several cases. But often, this technology could not be implemented because of high investment and operating costs.

Alternatively, the free jet is discussed as an efficient and low investment and operating cost technology. The free jet may transport oxygen-rich water from the surface down into the hypolimnion, thereby destratifying a water system. A free jet entrains on its way down even more oxygen rich and warm epilimnic water. This water will finally — if some mixing with the cold hypolimnic water occurs — be transferred to the metalimnion. The density differences will make this water travel long distances.

The energy input may be very low and the objective must not be to totally overturn a system. A jet started in early spring may help a lake to have a deep enough epilimnion, relatively large in volume in respect to the hypolimnion, and the normal wind will recirculate the water transferring enough oxygen to the deeper part, thus expanding the fish habitat and enabling benthic fauna. Literature also shows that the occurrence of massive algal blooms may be reduced.

The oxygen efficiency can be multifold compared to standard technologies.     

Raexcess/Ba growth rates and U-Th-Ra-Ba systematic of Baltic Mn/Fe crusts

We analyzed ²³⁸U, ²³⁴U, ²³²Th, ²³⁰Th, and ²²⁶Ra by thermal ionization mass spectrometry (TIMS) and Ba by inductively coupled plasma optical emission spectrometry (ICP-OES) on eight Mn/Fe crusts from the Mecklenburg Bay (SW Baltic) and on one from the Bothnian Bay (N Baltic) to test the ²²⁶Ra_ex/Ba ratio as potential geochronometer. ²²⁶Ra_ex/Ba ratios decrease as a function of depth within the concretions in all analyzed profiles. Calculated diffusion coefficients are relatively low (∼9 · 10⁻⁷ cm²/yr for Ra and 5 · 10⁻⁷ cm²/yr for Ba) and suggest that diffusion is negligible for the Ra and Ba record. In addition, ²²⁶Ra_ex/Ba ages are consistent and independent from the growth rate and growth direction within a crust. Thus, the decline in ²²⁶Ra_ex/Ba ratio is most likely due to radioactive decay of ²²⁶Ra_ex, although the influence of varying oxic conditions has still to be evaluated. ²²⁶Ra_ex/Ba growth rates range from 0.021 to 0.0017 mm/yr and tend to be lower than those calculated and based on stratigraphic methods (1 to 0.013 mm/yr). ²²⁶Ra_ex/Ba ages of concretions from shallow water environment (20 m depth, Mecklenburg Bay/SW Baltic) cover a time interval from 990 ± 140 yr to 4310 ± 310 yr BP corresponding to the stabilization of the sea level close to the present position about 5500 to 4500 yr ago. One sample from greater depth (70 m, Bothnian Bay-/N Baltic) showed a higher ²²⁶Ra_ex/Ba age of 6460 ± 520 yr BP.     

The significance of fixed ammonium in Palaeozoic sediments for the generation of nitrogen-rich natural gases in the North German Basin

In contrast to predominantly hydrocarbon-rich natural gases in the western part of the Central European Basin (CEB), accumulations of natural gases from the eastern part of the North German Basin (NGB) are nitrogen-rich with up to 90% N₂. This study is focused on the behaviour of fixed ammonium in clay minerals of organic-rich Palaeozoic sediments in the eastern part of the NGB as a major source of nitrogen-rich natural gases. Carboniferous shales have been investigated for a better understanding of nitrogen fixing during diagenesis, storage during burial and release during devolatilization processes or fluid–rock interactions. The total nitrogen contents in the studied Carboniferous shales of the NGB reach up to 2700 ppm with an inorganic fixed portion (in the form of NH₄ ⁺–N) of more than 60%. The results of this study indicate an increasing proportion of the mineralogically fixed ammonium with increasing thermal maturity and storage up to catagenetic conditions. The isotopic composition of fixed-NH₄ is relatively homogeneous in the majority of the shales and ranges from +1 to +3.5‰. In contrast, samples from the basin centre show a significant decrease in ammonium contents down to 460 ppm coupled with a shift in δ¹⁵N up to +5.6‰ suggesting a release of nitrogen on a large scale. Calculation of nitrogen loss and isotopic fractionation indicate that more than 30% of nitrogen was released as ammonium probably as a consequence of fluid-rock interaction with highly saline brines.