Attenuation of Scalar Fluxes Measured with Spatially-displaced Sensors

Observations from the Horizontal Array Turbulence Study (HATS) field program are used to examine the attenuation of measured scalar fluxes caused by spatial separation between the vertical velocity and scalar sensors. The HATS data show that flux attenuation for streamwise, crosswind, and vertical sensor displacements are each a function of a dimensionless, stability-dependent parameter n _m multiplied by the ratio of sensor displacement to measurement height. The scalar flux decays more rapidly with crosswind displacements than for streamwise displacements and decays more rapidly for stable stratification than for unstable stratification. The cospectral flux attenuation model of Kristensen et al. agrees well with the HATS data for streamwise sensor displacements, although it is necessary to include a neglected quadrature spectrum term to explain the observation that flux attenuation is often less with the scalar sensor downwind of the anemometer than for the opposite configuration. A simpler exponential decay model provides good estimates for crosswind sensor displacements, as well as for streamwise sensor displacements with stable stratification. A model similar to that of Lee and Black correctly predicts flux attenuation for a combination of streamwise and crosswind displacements, i.e. as a function of wind direction relative to the sensor displacement. The HATS data for vertical sensor displacements extend the near-neutral results of Kristensen et al. to diabatic stratification and confirm their finding that flux attenuation is less with the scalar sensor located below the anemometer than if the scalar sensor is displaced an equal distance either horizontally or above the anemometer.     

Attacks on oil transport pipelines in Nigeria: A quantitative exploration and possible explanation of observed patterns

In countries with insufficient investments in infrastructure and weak environmental governance, oil leakage from pipelines often occurs as a result of poor management and maintenance. Nigeria has its share of such incidents, but also, it suffers a large number of deliberate attacks (‘interdictions’) on oil pipelines. Often these attacks are accompanied by oil theft, carried out by well-equipped professionals and/or at a smaller scale by opportunistic local residents. The causes of these attacks, and the extent of subsequent damage to local communities and the environment, are obscured by a complex web of stakeholders, claims and actions. Any efforts to mitigate the negative impacts of interdiction on the environment and people require a better understanding of its spatiotemporal pattern of occurrence. This article presents a first quantitative and regional exploration of the problem of oil pipeline interdiction in Nigeria. It illustrates geographic patterns through choroplethic and bivariate GIS (Geographical Information Systems) map overlays. We examine interdiction statistics, identify spatiotemporal patterns and discuss correlations with socioeconomic factors. Findings include: (a) strong negative correlation between pipeline interdiction and poverty; and (b) statistically and non-statistically significant mean differences in the pattern of interdiction occurrence amongst the five geographic regions. Finally, we highlight the need for much better data collection and reporting for the mitigation of the negative socio-environmental impacts of interdiction incidences.     

Zur Entstehung und Entwicklung von Kontinentalen Riftsystemen

Zusammenfassung Kontinentale Riftsysteme und ihre möglichen Entwicklungsstadien stehen in direktem Zusammenhang mit der Teilung von Kontinenten und ihren damit verbundenen Bewegungen.Am Beispiel des Rheinischen Riftsystems und seinen Randbereichen wird über stratigraphische Daten sowie K-Ar Altersdaten vulkanischer Aktivitäten demonstriert, daß die Bildungs- und Frühphase dieses Systems die Existenz eines komplexen synchronen Zugspannungssystems notwendig machte. Als wahrscheinlichste Ursache hierfür werden Hebungen der Lithosphäre vorgeschlagen. Diese Vorstellung wird durch die Quantifizierung von Hebungsvorgängen anhand numerischer Modelle belegt.Im Stadium der Ozeanbildung weist die kontinentale Kruste starke Absenkungen entlang der passiven Kontinentalränder auf. Die Betrachtung struktureller Kräfte aufgrund lateraler Dichtedifferenzen am Übergang von kontinentaler zu ozeanischer Kruste legt eine Beeinflussung der Dynamik derartiger Strukturen durch diese Kräfte nahe. Mit Hilfe numerischer Rechnungen werden die zugehörigen Spannungen, ihre räumliche Verteilung und ihr möglicher Einfluß auf das Deformationsgeschehen abgeschätzt.Der hauptsächliche Vorteil der numerischen Rechnungen liegt in der quantitativen Verknüpfung komplexer Strukturen mit komplizierten Rheologien und spezifischen Kräfteverteilungen sowie Randbedingungen.

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Continental rift systems and their possible stages of development are directly related to the split up of continents and the corresponding movements.For the Rhenish Rift System it will be demonstrated on the base of stratigraphic data and K-Ar ages of volcanic activities, that the rift forming phase required a complex synchronous system of tensional stresses. As the most likely cause of such a stress system lithospheric uplift is proposed. This idea is supported by means of quantitative numerical models.During the formation of the ocean the continental crust exhibits significant subsidence along passive continental margins. The existence of differential loads on the continents and their compensation by buoyancy forces implies an influence of these structural loads on the dynamics of the transition zone. The corresponding structural stersses, their special distribution and their possible affects on the deformation rates are quantified on the base of numerical calculations.The main advantage of the numerical calculations is evidently the quantitative relation of complex structures with complicated rheologies and specific force systems of boundary conditions.

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Résumé Les systèmes de rift continentaux et les étapes possibles de leur développement sont en rapport direct avec séparation des continents et avec les mouvements qui en résultent. On démontres, sur la base de données stratigraphiques et d'âges K-Ar des activités volcaniques du graben rhénan, que les premières phases de formation de ce système ont requis l'existence d'un système complexe et synchrone de forces d'extension. On propose comme cause la plus vraisemblable d'un tel système l'existence de soulèvements lithosphériques. Cette idée est appuyée par des modèles numériques quantitatifs. Pendant la formation de l'océan, la croûte continentale a subi le long des marges continentales passives de grands effondrements. L'existence de forces tectoniques causées par des différences de densité latérales le long le long de la transition entre croûte continentale et croûte océanique donne lieu à la supposition que la dynamique de telles structures a été influencée par ces forces. Les tensions associées, leur distribution spatiale et leur possible influence sur le processus de déformation ont été estimées à l'aide de calculs numériques. L'avantage principal des des calculs numériques est de permettre une relation quantitative entre structures complexes à rhéologies compliquées et répartitions de forces spécifiques comme aussi de conditions marginales.

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Geomagnetische Tiefentellurik

Zusammenfassung Die lokalen Unterschiede der geomagnetischen zeitlichen Variationen [1, 2] wurden mit Hilfe von 3 Reiseregistrierstationen nachFanselau [3] untersucht. Hier werden die gegenseitige Beeinflussung der Variometernadeln, Veränderung der Skalenwerte über die Breite des Registrierpapiers und die Abhängigkeit der Grösse des Skalenwertes von der Temperatur sowie von der Grösse der Vertikalintensität untersucht. Die reduzierten Skalenwerte besitzen im Mittel eine Unsicherheit von nicht mehr als 0,6%. Eine grössere Genauigkeit kann bei Feldmessungen nicht erwartet werden. Aufstellung und Justierung der Stationen im Felde werden beschrieben.

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Summary Local differences of geomagnetic variations [1, 2] were investigated by three ambulant geomagnetic variographs afterFanselau [3]. The influence of the variometer needles on each other, the dependence of the scale-values on the position of the lightpoint and the changing of the scale-value with temperature and with the value of the vertical intensity are shown. The reduced scale-values have an uncertainty of not more than 0.6%. A higher accuracy is not to be expected for field measurements. The menagement and the adjustment of the stations in field are described.

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Mitteilung Nr. 157 des Geomagnetischen Instituts Potsdam.     

Die Liegendschichten der devonischen Pyrit- u. Schwerspat-Lager von Eisen (Saarland), Meggen und des Rammelsberges

Detailed petrographic and geochemical investigations on the rocks underlying the Devonian stratiforme pyrite and barite deposits of Eisen (Saar district), Meggen (Westphalia), and Rammeisberg (Harz Mountains) in the Rhenish Schiefergebirge have led to the following conclusions:

1. These deposits are tied to dark shales of the pelagic basin facies. In all cases a local depression of the sea floor coincides largely with the spatial extension of the overlying pyrite and barite bodies. These depressions are marked by a large number of sand and silt intercalations, accumulations of reef debris and a significant lower carbonate content.
2. The dark shales underneath the deposits have conspicuously high, but strongly varying contents of Mn, Zn and Pb. This, corresponding with the low carbonate content, is characteristic for the presence of hydrothermal, metalliferous emissions.
3. Predepositional phases of sulfide and barite emplacement are indicated by small layers and lenses.

     

Evidence for a nitrogen flux directly derived from the European subcontinental mantle in the Western Eger Rift, Central Europe

In the Czech-German border region of the Vogtland and NW Bohemia (western Eger rift, Central Europe), chemical and isotopic compositions (C, N, He, Ar) of free gas from a thermal water escape (fluorite mine, Schönbrunn), two mineral springs (“Eisenquelle,” Bad Brambach; “Sprudel III,” Bad Elster) and a mofette (Bublak) located along an ∼40-km long traverse are reported. The gases of Bublak and Bad Brambach are CO₂-rich (>99 vol.%) and have δ¹³C values of −1.95 and −4.29‰, respectively. With distance from the center of CO₂ degassing (Bublak) the δ¹³C values decrease, most likely due to physico-chemical fractionation of CO₂ between gaseous and aqueous phases rather than to admixture of organic/biogenic CO₂. The δ¹⁵N values range between −3.2 and −0.6‰, compared to an upper mantle value of −4.0 ± 1.0‰. The four locations are characterized by ³He/⁴He ratios decreasing from 5.9 R_a in the center (Bublak) to 0.8 R_a in the periphery (Schönbrunn) and give evidence for mixing of He from a deep-seated magmatic source with a crustal source. The location with the highest ³He/⁴He ratio (5.9 R_a) is accompanied by the highest ⁴⁰Ar/³⁶Ar (550). We argue that the nitrogen of the Bublak mofette gas is a mixture of predominantly atmospheric and mantle-derived components, whereas at the other three locations crustal nitrogen may also be present. The Bublak δ¹⁵N value of ≈−4.5 ± 1.0‰ represents the first free gas δ¹⁵N reference from the European subcontinental mantle (ESCM) and indicates that, in contrast to the ³He/⁴He ratios, the δ¹⁵N values are equal for ESCM and MORB, respectively.     

On Frequency Response Corrections for Eddy Covariance Flux Measurements

Several potentially significant errors are noted in published frequency-response corrections for eddy-covariance flux measurements.     

Evolution of a tourmaline-bearing lawsonite eclogite from the Elekdağ area (Central Pontides,N Turkey): evidence for infiltration of slab-derived B-rich fluids during exhumation

An undated high-pressure low-temperature tectonic mélange in the Elekda area (central Pontides, N Turkey) comprises blocks of MORB-derived lawsonite eclogite within a sheared serpentinite matrix. In their outer shells, some of the eclogite blocks contain large (up to 6 cm) tourmaline crystals. Prograde inclusions in poikiloblastic garnet from a well-preserved eclogite block are lawsonite, epidote/clinozoisite, omphacite, rutile, glaucophane, chlorite, Ba-bearing phengite, minor actinolite, winchite and quartz. In addition, glaucophane, lawsonite and rutile occur as inclusions in omphacite. These inclusion assemblages document the transition from a garnet-lawsonite-epidote-bearing blueschist to a lawsonite eclogite with the peak assemblage garnet + omphacite I + lawsonite + rutile. Peak metamorphic conditions are not well-constrained but are estimated approximately 400–430°C and >1.35 GPa, based on Fe–Mg exchange between garnet and omphacite and the coexistence of lawsonite + omphacite + rutile. During exhumation of the eclogite–serpentinite mélange in the hanging wall of a subduction system, infiltration of B-rich aqueous fluids into the rims of eclogite blocks caused retrogressive formation of abundant chlorite, titanite and albite, followed by growth of tourmaline at the expense of chlorite. At the same time, omphacite I (X_Jd=0.24–0.44) became unstable and partially replaced by omphacite II characterized by higher X_Jd (0.35–0.48), suggesting a relatively low silica activity in the infiltrating fluid. Apart from Fe-rich rims developed at the contact to chlorite, tourmaline crystals are nearly homogeneous. Their compositions correspond to Na-rich dravite, perhaps with a small amount of excess (tetrahedral) boron (~5.90 Si and 3.10 B cations per 31 anions). ¹¹ B values range from –2.2 to +1.7. The infiltrating fluids were most probably derived from subducting altered oceanic crust and sediments.     

Ichthyofauna in the upper Rhine River close to the city of Karlsruhe as determined by the analysis of fish impingement by cooling-water intakes of a power plant

The fish fauna in the northern part of the upper river Rhine close to the city of Karlsruhe (Germany) was analyzed by collecting fish from the cooling-water intake of a power plant (impingement method) between 1989 and 2001. With this method a total of 36 fish species were recorded. The results were compared between the years as well as with other studies on the fish fauna in this area. Particularly with regard to the physical structure of the river bed and banks, the pre-technical situation of the river Rhine has not been restored. However, the number of fish species has been augmented since the 1970s mainly due to improvements in the water quality and almost all autochthonous fish species are present again. Altogether only three introduced fish species (Sander lucioperca L., Lepomis gibbosus L., and Carassius auratus gibelio were found in this study. Among the long-distance migrating species three freshwater spawners (Lampetra fluviatilis, Petromyzon marinus and Salmo trutta trutta) were detected in addition to the catadromous eel. The eudominant fish species varied between years, i.e. the European eel, Anguilla anguilla, was the eudominant species 1989, whereas this species occurred in much lower numbers during the subsequent sampling campaigns. This clearly indicates that the high dominance of eels is mainly caused by stocking activities in the upper Rhine. In the following years roach, Rutilus rutilus was the eudominant fish species. Overall a positive development of the fish fauna in the upper Rhine over the last 15 years could be observed in terms of fish populations as well as in terms of species richness.