Interaction of organic compounds with calcium carbonate-II. Organo-carbonate association in Recent sediments

Surface area measurements as well as organic carbon, nitrogen and phosphorus analyses on various grain size fractions of carbonate mud samples confirm that in natural environments of carbonate deposition, surface sorption processes take place which are similar to those described earlier for dissolved organics and artificially suspended calcite particles in both seawater and synthetic solutions.The specific surface area of the sediment increases from 1.8m²/g for the coarse-grained fraction to 12.5 m²/g for the fine material; likewise organic carbon, nitrogen and phosphorus increase with increasing surface area so that there are 1.20 mg C, 0.175 mg N and 0.06–0.20 mg P associated with every square meter of carbonate surface irrespective of the mineralogy of the sediment particles.It appears that the organic matter in these sediments is similar in composition, structure and quantity to the organic layers produced in sorption experiments. With their apparently defined structure and ubiquitous nature, these layers could determine the mineralogy and orientation of submarine carbonate cement or could even be a prerequisite to calcification in general.     

Late Cretaceous exhumation history of an extensional extruding wedge (Graz Paleozoic Nappe Complex, Austria)

Late Cretaceous structures within the eastern Graz Paleozoic Nappe Complex define an extruding wedge with north-eastward directed thrusting in eastern portions and strike-slip shear along the margins. Stacking structures are overprinted by south-westward directed extension with low-grade metamorphic rocks in the hangingwall and high-grade basement rocks in the footwall. Pressure–temperature and structural data are obtained from successively opening quartz veins that record various stages of progressive deformation and metamorphism. Fluid inclusion data and related structures show that during extension isothermal decompression from ca. 550°C and 8 kbar down to ca. 450°C and 2 kbar was related to exhumation of rocks from deep crustal levels. The data point to a high geothermal gradient and explain condensed paleo-isotherms due to ductile normal faulting in the eastern areas of the Graz Paleozoic Nappe Complex. The investigated Late Cretaceous structural elements suggest that the Graz Paleozoic Nappe Complex decoupled from the surrounding basement units and operated as a large-scale extension–extrusion corridor that evolved prior to Miocene extrusion tectonics in the Eastern Alps.     

The metamorphic evolution of migmatites from the Ötztal Complex (Tyrol,Austria) and constraints on the timing of the pre-Variscan high-T event in the Eastern Alps

Within the Ötztal Complex (ÖC), migmatites are the only geological evidence of the pre-Variscan metamorphic evolution, which led to the occurrence of partial anatexis in different areas of the complex. We investigated migmatites from three localities in the ÖC, the Winnebach migmatite in the central part and the Verpeil- and Nauderer Gaisloch migmatite in the western part. We determined metamorphic stages using textural relations and electron microprobe analyses. Furthermore, chemical microprobe ages of monazites were obtained in order to associate the inferred stages of mineral growth to metamorphic events. All three migmatites show evidence for a polymetamorphic evolution (pre-Variscan, Variscan) and only the Winnebach migmatite shows evidence for a P-accentuated Eo-Alpine metamorphic overprint in the central ÖC. The P-T data range from 670–750 °C and < 2.8 kbar for the pre-Variscan event, 550–650 °C and 4–7 kbar for the Variscan event and 430–490 °C and ca. 8.5 kbar for the P-accentuated Eo-Alpine metamorphic overprint. U-Th-Pb electron microprobe dating of monazites from the leucosomes from all three migmatites provides an average age of 441 ± 18 Ma, thus indicating a pervasive Ordovician-Silurian metamorphic event in the ÖC.     

A field trial for in-situ bioremediation of 1,2-DCA

Historic spillages of chlorinated hydrocarbons at a vinyl chloride plant in the Rotterdam Botlek area in The Netherlands have lead to contamination of the underlying aquifer. The principal contaminant is 1,2-dichloroethane (1,2-DCA). The contamination is temporarily contained by a pump-and-treat system. A field trial was carried out to investigate the feasibility of treating the dissolved phase of 1,2-DCA via reductive dechlorination by injection of an aqueous solution of methanol, ammonium chloride and sodium chloride into the confined aquifer using an array of eight boreholes. Biodegradation of 1,2-DCA was localised. This was attributed to limited mixing of the carbon substrate within the test zone. In addition, clogging of recharge wells complicated groundwater circulation.     

Die Mikroseismik und ihre Anwendung zum Abschätzen der Dicke der Kontinentalschollen

Zusammenfassung An Hand einiger Wetterlagen mit besonders starker Mikroseismik wird der Verlauf von Amplituden und Perioden in Stuttgart verfolgt. Das Gesetz der Abhängigkeit zwischen Periode und Amplitude wird empirisch ermittelt, das Periodenspektrum gezeichnet. Die am häufigsten auftretende Periode wird zur Berechnung der Dicke der schwingenden Schicht benutzt unter der Annahme, dass diese Schicht mit ihrer Unterlage lose verbunden ist und die Art der Schwingungen sich nicht wesentlich von Rayleighwellen unterscheidet. Es ergibt sich so der theore tische Zusammenhang zwischen Periode und Amplitude einerseits und der Schichtdicke andrerseits. Sie beträgt für Norwegen etwas über 40 km.

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Summary With the help of several weather-situations with particularty violent microseism the progress of amplitudes and periods as perceived at Stuttgart is examinated. The law of dependency between period and amplitude is found empirically, the spectrum of periods is drawn up. The period, which occurs most frequently is used for calculating the thickness of the swinging layer as this layer is supposed to be in loose connection with its support and as the sort of oscillations is not essentially different from Rayleight waves. Thus there is found the theoretical connection between periods and amplitudes and, on the other side, the thickness of layer of something more than 40 km for Norway.

     

Bemerkungen zur Zwillingsbildung bei Plagioklasen

Ohne Zusammenfassung     

An Algorithm to Determine the Slope of the Spectral Absorption of Colored Dissolved Organic Matter (CDOM) and Detritus

A simple method to determine the slope of spectral variations of combined absorption of the colored dissolved organic matter and detritus (CDM) is presented. This method uses the slope of total absorption spectrum excluding contribution of waters in lieu of slope for the CDM. The errors in slopes using the new method decreased with increase in contributions of CDM to the total absorption. The relative errors were less than 10% when CDM contributions were above 60% and even at very low contributions of CDM of 25%, errors in the slopes were less than 40%. For estuarine and coastal waters rich in CDM, the errors in the slopes for CDM were less than 10% using this simple method. Absorption of CDM derived using the slope with the new method in a semi-analytical algorithm QAAV6 showed improved performance with RMSE of 0.07, 0.0119 and 0.0027 at 405, 555 and 665 nm respectively and with R² > 0.95 at all spectral range. The method provided values of spectral absorption due to CDM with fewer errors when validated with the satellite derived data from MODIS and SeaWiFS. This method to determine the slope of CDM could be easily implemented in any model, as it was very generic in nature, simple, did not involve any mathematical model and avoids empirical methods. Since the method is also independent of any specific bands, it can be used for most ocean color satellites. Considering the performance of this new method and applicability for most water types, it was considered as a better option to derive the slope of CDM than using a constant value or deriving the slope with empirical method.     

Environmental mechanism of magnetic susceptibility changes of lacustrine sediments from Lake Hulun, China

The changes of magnetic susceptibility(κ) are correlated with those of corresponding sedimentological, geochemical, mineralogical and biological results, which verifies thatκ can be taken as one of the environmental proxies. However, usually the exact origin of magnetic signal is poorly understood, and is difficult to relate with the environmental evolution. Magnetic properties of material derived from the catchment and sedimentary environment may affect the accumulation, preservation, or authigenesis and diagenesis of magnetic minerals. In the Lake Hulun region in Inner Mongolia, it is found that muddy sediments, deposited during high water level period (corresponding to humid climate), have comparatively highκ values. In contrast, the sandy sediments, deposited during low water level period (corresponding to arid climate), have lowκ values. Detailed rock magnetic investigation confirms that detrital magnetite derived from volcanic rocks in the catchment exists in both muddy and sandy sediments. During high water level period, secondary ferrimagnetic iron sulphide was produced in muddy sediments under relatively reductive conditions. Ferrimagnetic iron sulphide, coexisting with detrital magnetite, predominates the magnetic properties of muddy sediments, resulting in increasingκ. This paper reveals the significance of authigenic ferrimagnetic iron sulphide produced after sediment deposition.     

Modeling climate change and biophysical impacts of crop production in the Austrian Marchfeld Region

Climate change affects major biophysical processes in agricultural crop production (e.g. evaporation of plants and soils, nutrient cycles, and growth of plants). This analysis aims to assess some of these effects by simulating regional climate projections that are integrated in the biophysical process model EPIC (Environmental Policy Integrated Climate). Statistical climate models have been developed for six weather parameters based on daily weather records of a weather station in the Austrian Marchfeld region from 1975 to 2006. These models have been used to estimate daily weather parameters for the period 2007–2038. The resulting projections have been compared to climate scenarios provided from the TYNDALL Centre for Climate Change Research, which are based on General Circulation Models (GCMs). The comparison indicates some differences, namely a smaller temperature increase and a higher precipitation amount in the TYNDALL data. Both climate datasets have been used to simulate impacts of climate change on crop yields, topsoil organic carbon content, and nitrate leaching with EPIC and thus to perform a sensitivity analysis of EPIC. Yield impacts have been assessed for four simulated crops, i.e. 6.2?t/ha for winter wheat for statistical climate projections compared to 5.7?t/ha for TYNDALL scenarios, 10.6?t/ha for corn compared to 10.5?t/ha, 3.9?t/ha for sunflower compared to 3.7?t/ha, and 4.5?t/ha for spring barley compared to 4.3?t/ha—all values as an average over the period 2007–2038. Smaller differences have been simulated for topsoil organic carbon content i.e. 55.1?t/ha for the statistical climate projections compared to 55.3?t/ha for the TYNDALL scenarios and nitrate leaching i.e. 7.1?kg/ha compared to 11.1?kg/ha. All crop yields as well as topsoil organic carbon content and nitrate leaching show highest sensitivity to temperature and solar radiation.