Chemistry of alkali extraction of brown coals—I. Kinetics, characterisation and implications to coalification

Three Australian brown coals have been separated into humin and humic acid fractions and studied by high resolution solid state ¹³C NMR spectroscopy and Fourier transform IR spectroscopy. The aromatic rings of the humic acids are highly substituted showing that extensive cross linking must have occurred during formation from wood lignin and tannin. However, the humins contain more aliphatic carbon and hydrogen than the corresponding humic acids. This shows that little cross linking has occurred with other components of the brown coal such as resins, waxes cutin and algal detritus, and cross linking has not rendered the aromatics alkali insoluble. The kinetics of extraction are complex and not simple first order. This is reflected in the chemical composition of the humic acid which is extraction temperature dependent. We also observed that there is a conversion of aromatic carbon to aliphatic carbon and gas during extraction, probably by alkaline oxidation, resulting in ring opening. A range of suitable model compounds have been studied to confirm this finding. Such a mechanism may account for the modification of lignin in oxidising environments such as those occurring in the initial stages of coalification (lignite or brown coal formation) and in soils.     

Plio-Quaternary geodynamic evolution of a segment of the Peruvian Andean Cordillera located above the change in the subduction geometry: the Cuzco region

The Cuzco region, which is located above a change in subduction geometry, appears to be characterized by a variable Plio-Quaternary tectono-sedimentary evolution essentially located along the major fault system that separates the High Plateaux from the Eastern Cordillera. After the higher surface formation of the High Plateaux, a set of Neogene basins were filled by Miocene “ fluvio-torrential” series and by Plio-Pleistocene fluvio-lacustrine deposits. The Neogene series have been affected by compressional tectonic forces attributed to the Late Miocene. This compression is followed by roughly E-W trending syn-sedimentary extensional tectonics attributed to the Pliocene; it is related to reactivation of the pre-existing major faults, basin evolution, and volcanic activity concentrated along the faults. In the Early Pleistocene, fluvio-lacustrine deposits are affected by syn- and post-sedimentary compressional tectonism it is characterized by shortening that trends both N-S and E-W and produces folding and faulting of the sedimentary cover. Extensional tectonism trending roughly N-S has been taking place from the Middle Pleistocene to the Present; it is coeval with shoshonitic volcanic activity, and with sedimentation of fluvio-lacustrine terraces, torrential fans and moraines. Quaternary and active normal faults due to this tectonism, are located in a narrow zone more than 100 km-long between the High Plateaux and the Eastern Cordillera, and two 15 km-long fault sectors in the Eastern Cordillera. Characteristic Pleistocene scarps, 400 m or more high, are due to the cumulative normal offset, and there are also little scarps, with heights ranging between 2 and 20 m, which are related to Holocene fault reactivations. Recent fault reactivation on the Cuzco fault system, during the April 5, 1986 earthquake (m_b = 5.3), is due to the N-S trending extension. This state of stress, located at a mean elevation of roughly 3730 m, is generally homogeneous to different scales. The active Cuzco normal faults may be a consequence of adjustment between the compensated Western Cordillera and the undercompensated Eastern Cordillera, this latter being uplifted higher than its isostatic equilibrium due to compression acting on its eastern edge. The variation of the state of stress, during the Plio-Quaternary is in agreement with the variations of the compressional boundary forces. It may be explained by variation of the convergence rate or by the variation of pull-slab forces.     

Meteorology and haze structure during AGASP-II,Part 1: Alaskan Arctic flights, 2–10 April 1986

The second Arctic Gas and Aerosol Sampling Program (AGASP-II) was conducted across the Alaskan and Canadian Arctic in April 1986, to study the in situ aerosol, and the chemical and optical properties of Arctic haze. The NOAA WP-3D aircraft, with special instrumentation added, made six flights during AGASP-II. Measurements of wind, pressure, temperature, ozone, water vapor, condensation nuclei (CN) concentration, and aerosol scattering extinction (b_sp) were used to determine the location of significant haze layers. The measurements made on the first three flights, over the Arctic Ocean north of Barrow and over the Beaufort Sea north of Barter Island, Alaska are discussed in detail in this report of the first phase of AGASP II. In the Alaskan Arctic the WP-3D detected a large and persistent region of haze between 960 and 750 mb, in a thermally stable layer, on 2, 8, and 9 April 1986. At its most dense, the haze contained CN concentrations >10,000 cm^–3 and b_sp of 80×10^–6 m^–1 suggesting active SO₂ to H₂SO₄ gas-to-particle conversion. Calculations based upon observed SO₂ concentrations and ambient relative humidities suggest that 10⁴–10⁵ small H₂SO₄ droplets could have been produced in the haze layers. High concentrations of sub-micron H₂SO₄ droplets were collected in haze. Ozone concentrations were 5–10 ppb higher in the haze layers than in the surrounding troposphere. Outside the regions of haze, CN concentrations ranged from 100 to 400 cm^–3 and b_sp values were about (20–40)×10^–6 m^–1. Air mass trajectories were computed to depict the air flow upwind of regions in which haze was observed. In two cases the back trajectories and ground measurements suggested the source to be in central Europe.     

The social forecasting industry

This is an essay and report on the social forecasting industry-the collection of individuals and organizations, both profit and nonprofit, supplying forecasts of social futures in direct exchage for pay. It begins with a review of the industry's size, growth, and scope; contrary to initial impressions, the industry is by any comparative standard quite small, occupying a precarious niche in the much larger market for statistical services. Hallmark methodologies of the industry, including the Delphi method and cross-impact analysis, are discussed extensively. These methodologies are linked to a domain assumption of the industry—namely, that the complexities of the social world are best rendered tractable by forming consensuses of experts' judgments. It is argued that the key characteristic differentiating the social forecasting industry from forecasting in the social sciences proper—the existence of a direct, paying market for services—is an important element in maintaining the most salient methodological and product differences between the two arenas: The marketplace for forecasts is not the same as the marketplace for ideas.     

Production and pelagic dissolution of biogenic silica in the Southern Ocean

Vertical distributions of particulate silica, and of production and dissolution rates of biogenic silica, were determined on two N-S transects across the Pacific sector of the Antarctic Circumpolar Current during the austral spring of 1978. Particulate silica profiles showed elevated levels in surface water and near the bottom, with low (35–110 nmol Si · 1^?1) and vertically uniform values through the intervening water column. Both the particulate silica content of the upper 200 m and the production rate of biogenic silica in the photic zone increased from north to south, reaching their highest values near the edge of the receding pack ice. A significant, but variable, fraction (18–58%) of the biogenic silica produced in the surface layer was redissolving in the upper 90–98 m. Net production of biogenic silica in the surface layer (production minus dissolution) was proceeding at a mean rate of ca. 2 mmol Si · m^?2 · day^?1. This is ca. 4 times greater than the most recent estimate of the mean accumulation rate of siliceous sediments beneath the ACC. We estimate, based on mass balance, that the mean dissolution rate of biogenic silica in subsurface water column in the Southern Ocean is 1.2–2.9 mmol Si · m^?2 · day^?1.     

Les Facies de Transgression du Trias sur la Bordure Nord-est du Massif Central Français

Résumé La transgression triasique est suivie d'Est en Ouest sur la bordure du Massif Central français. Les formations sont de plus en plus récentes vers l'Ouest, indépendamment de leur faciès. Les limites du Buntsandstein et du Trias supérieur semblent locales et d'origine tectonique, tandis que la limite du Ladinien supérieur parait plus générale et correspond à la période où le caractère marin de la transgression sur les massifs hercyniens était le plus franc.Le début de la transgression aniso-ladinienne est daté pour l'Anisien par des empreintes de Reptiles et pour les faciès les plus marins du Ladinien par des Foraminifères et des pollens. A cette période, des microfaunes mésogéennes de mer ouverte apparaissent sur les bordures.Dans les faciès de transgression réduits, le Trias est constitué de grès fins silteux à pseudomorphoses de sel gemme et empreintes de Reptiles, étalés par une mer pelliculaire sur une surface plate. Le socle sous-jacent a fourni peu de matériel clastique et les courants sont orientés du Nord au Sud. Les évaporites sont plus concentrées sur la bordure que plus au large, ce qui implique une certaine aridité pendant toute la période de la transgression.Les faciès de bordure les plus avancés sur le socle sont formés d'une dolomie paralique supratidale déposée dans des lagunes évaporitiques. Sur les massifs hercyniens, des fractures et des failles ouvertes ont permis des circulations auxquelles sont liés des remplissages carbonates et des minéralisations.

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Conditions of the triassic transgression are analysed from East to West across the eastern border of the Central Massif. Formations directly overlying the basement get younger and younger westwards, without relation with the environment. Buntsandstein and upper Triassic boundaries appear to be syntectonic local limits. The upper Ladininian boundary seems to be more general and connected with the main period of the marine environment for the transgression on the variscan basement rocks. The anisoladinian transgression beginns during the anisian age as indicated by fooprints, while ladinian age is supported by mesogean foraminifera and palynology during the climax of the transgression, in an open sea environment.Silty fine sandstones with footprints and salt casts constitute the triassic transgression facies on the flattened border of the Central Massif. The underlying basement supplied only a little arenaceous material and the currents are oriented from Nord to South. Evaporites are more concentrated at the boundary of the transgression than towards the basin, what means aridity.Paralic supratidal dolomite constitutes the most external deposits at the transgression limit, in a syntectonic environment. Dolomite infillings and ore deposits are connected with water circulations along faults and fractures.

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Zusammenfassung Die Triastransgressionsschichten werden von Osten nach Westen am Nordrand des französischen Zentralmassivs beschrieben. Die auf dem Grundgebirge auflagernden Basisschichten werden, unabhängig von ihrer Faziesausbildung, nach Westen stets jünger. Die Begrenzungen der Ablagerungen des Buntsandsteins und der oberen Trias werden nur lokal, wahrscheinlich in Abhängigkeit von synsedimentären, tektonischen Strukturen angetroffen. Die Beckenausdehnung am Top des oberen Ladiniums ist dagegen zusammenhängend zu erkennen. Sie entspricht den eindeutigeren marinen Transgressionsverhältnissen auf dem variskischen Sockel.Die einsetzende Transgression des Aniso-Ladiniums wird durch Reptilienfährten als anisisch und die stärker marinen Ablagerungen durch Foraminiferen und Pollen als ladinisch datiert. In diesem Zeitabschnitt dringen offenmarine, mesogäische Mikrofossilien bis zum Beckenrand vor.Die geringmächtigen Transgressionsablagerungen bestehen aus siltigen Feinsanden mit Steinsalzpseudomorphosen und Reptilienfährten. Diese Sande wurden von einem sehr seichten Meer auf dem stark eingeebneten Grundgebirge verteilt. Das Grundgebirge hat nur sehr wenige klastische Abtragungsprodukte geliefert. Die Strömungen waren von Norden nach Süden ausgerichtet. Evaporite treten stärker in den randlichen Gebieten als zum offenen Becken hin auf. Dies zeigt auf eine ausgeprägte Aridität während der gesamten Transgressionszeit hin.Die am weitesten zum Festland hin vorgeschobenen Transgressionssedimente bestehen aus paralischen, subpratidalen Dolomiten, die sich in evaporitischen Lagunen bildeten. Die in den offenen Spalten und Verwerfungen des Grundgebirges zirkulierenden Lösungen führten zu Dolomitausfällungen und zu schichtgebundenen Vererzungen.

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An experimental investigation of volatile exsolution in evolving magma chambers

Previous laboratory experiments investigating the fluid dynamics of replenished magma chambers have been extended to model effects resulting from the release of gas. Turbulent transfer of heat between a layer of dense, hot and volatile-rich mafic magma overlying cooler more evolved magma can lead to crystallization and exsolution of volatiles in the lower layer. Small gas bubbles can cause the bulk density to decrease to that of the upper layer and thus produce sudden overturning and initiate mixing, followed by further exsolution of gas and explosive eruption. These processes have been modelled in the laboratory using a chemical reaction between sodium or potassium carbonate and nitric acid to release small bubbles of CO₂. We have investigated both the initial overturning produced by gas release in the lower layer, and the subsequent evolution of gas due to intimate mixing of the two layers. The latter experiments, in which the reactants remained isolated in the two layers until overturning occurred, demonstrated unambiguously that the fluxes of chemical components across the interfaces between convecting layers are very slow compared to the flux of heat. This shows that the evolution of layers of magma of different origins and composition can take place nearly independently of each other. The magmas can coexist in the same stratified chamber, until their bulk densities become equal and they mix together. The processes illustrated in these experiments could occur in H₂O-bearing magmas such as in the calcalkaline association and in CO₂-bearing mafic magmas such as in silica undersaturated suites.     

Investigation of NaCl deliquescence in porous substrates using RH-XRD

We report on the use of X-ray diffractometry under controlled conditions of temperature and relative humidity (RH-XRD) for the investigation of NaCl deliquescence in the pore space of glass filter frits, which were used as model substrates. The study confirms that RH-XRD is an appropriate experimental technique for the in situ observation of phase transformation in porous materials. It is used for an investigation of both the deliquescence kinetics and the deliquescence humidity within pores of different median pore diameter. Several major influences affecting deliquescence rates in the pore space close to the surface of a porous material are discussed. It appears that quite short-term variation of ambient relative humidity, e.g., typical daily fluctuations, might induce damaging deliquescence–crystallization cycles within the pore space of building materials. In agreement with theoretical considerations it was found that confinement of NaCl crystals in pores with median diameters in the range 1.4–70 μm does not affect the deliquescence humidity of the salt.