Ozeane: Ergebnisse der 7. Sitzung der Kommission für nachhaltige Entwicklung (CSD) der Vereinten Nationen

Ocean Dynamics - Die 7. Sitzung der Kommission für nachhaltige Entwicklung (Commission on Sustainable Development, CSD) der Vereinten Nationen fand vom 19. bis 30. April 1999 im...     

Transmission electron microscopy on meteoritic troilite

Phase transitions and associated domains of meteoritic troilite (FeS) have been studied by means of transmission electron microscopy (TEM). Three polymorphs have been found, two of which can be described by superstructures of the NiAs-type structure (A, C subcell). The P \(\overline 6\) 2c (√3A, 2C) polymorph, stable at room temperature, displays antiphase domains with the displacement vector 1/3< \(\overline {\text{1}}\) 10>. In situ heating experiments showed that the P \(\overline 6\) 2c polymorph changes at temperatures of 115°–150° C into an orthorhombic pseudohexagonal transitional phase with the probable space group Pmcn (A,√3A, C). It contains antiphase domains with the displacement vector 1/2 [110] and twins with a threefold twin-axis parallel c. When heated above 210° C the transitional phase transforms into the high-temperature modification with NiAs structure (P6 ₃/mmc). All observed phase transitions are reversible. The occurrence of antiphase and twin domains, respectively, agrees with the symmetry reductions involved in the subsolidus phase transitions. This is demonstrated by group-subgroup relationships among the space groups P6 ₃/mmc, Pmcn, and P \(\overline 6\) 2c.     

Flux between soil and atmosphere, vertical concentration profiles in soil, and turnover of nitric oxide: 2. Experiments with naturally layered soil cores

Intact soils cores were taken with a stainless steel corer from a sandy podzol and a loamy luvisol, and used to measure the flux (J) of NO between soil and atmosphere and the vertical profile of the NO mixing ratios (m) in the soil atmosphere, both as function of the NO mixing ratio (m _a) in the atmosphere of the headspace. These measurements were repeated after stepwise excavation of the soil column from the top, e.g. by removing the upper 2 cm soil layer. The gaseous diffusion coefficients of NO in the soil cores were either computed from soil porosity or were determined from experiments using SF6. The NO fluxes (J) that were actually measured at the soil surface were compared to the fluxes which were calculated either from the vertical NO profiles (J _c ) or from the NO production and uptake rates (J _m ) determined in the excavated soil samples. In the podzol, the actually measured (J) and the calculated (J _m , J_m) NO fluxes agreed within a factor of 2. In the luvisol, the measured NO fluxes (J) and those calculated from the vertical NO profiles (J _c ) also agreed well, but in the upper 6 cm soil layer the NO fluxes (J _m ) calculated from NO production and uptake rates were up to 7 times higher than the measured NO fluxes. This poor agreement was probably due to the inhomogeneous distribution of NO production and consumption processes and the change of diffusivities within the top layers of the luvisol. Indeed, the luvisol showed a pronounced maximum of the NO mixing ratios at about 6 cm depth, whereas the podzol column exhibited a steady and exponential decrease of the NO mixing ratios with depth. The inhomogeneities in the luvisol were confirmed by incubation of the soil cores under anoxic conditions. This treatment resulted in production of NO at several depths indicating a zonation of increased potential activities within the luvisol profile which may have biased the modelling of the NO surface flux from turnover measurements in soil samples. Inhomogeneities could be achieved even in homogenized soil by fertilization with nitrate solution.     

Lithium isotope composition of ordinary and carbonaceous chondrites, and differentiated planetary bodies: Bulk solar system and solar reservoirs

In order to better constrain the Li isotope composition of the bulk solar system and Li isotope fractionation during accretion and parent body processes, Li isotope compositions and concentrations were determined on a number of meteorite falls and finds. This is the first comprehensive study that systematically investigates a representative set of samples from carbonaceous chondrites (CI, CM2, CO3, CV3, CK4 and one ungrouped member), enstatite chondrites (EH, EL), ordinary chondrites (H, L, LL), and achondrites (one eucrite, diogenites, one pallasite, and a silicate inclusion from a IAB iron).

Carbonaceous chondrites have an average isotope composition of δ⁷Li = + 3.2‰ ± 1.9 (2σ) which agrees with the average composition of relatively pristine olivines (representative for the bulk composition) from the Earth primitive upper mantle (PUM). This is lighter than the average δ⁷Li of the basaltic differentiates of the Earth, Moon and Mars and the achondrites. It is an important observation, however, that the lighter end of the isotopic range of the differentiates always coincides with the averages of the mantle olivines and the carbonaceous chondrites. From this we conclude that the bulk of the inner solar system consists mostly of material from carbonaceous chondrites and that the variation seen in the differentiates is due to planetary body processes. Ordinary chondrites are significantly lighter than carbonaceous chondrites. No significant differences in δ⁷Li exist between enstatite chondrites (n = 3) and carbonaceous or ordinary chondrites. The difference between carbonaceous and ordinary chondrites and the variability within the chondrites could indicate the existence of distinct Li isotope reservoirs in the early solar nebula.     

Bestimmung von Umweltqualitätsnormen für potenziell gewässerrelevante Stoffe

With the Water Framework Directive (WFD) the European Commission (EC) is requested to define environmental quality standards for pollutants to protect aquatic life in surface waters. Quality standards have to be derived by a scientific risk assessment and should not be exceeded. The recommended quality standards are mainly based on long term toxicological tests with algae, crustaceans and fish. The lowest effect concentration is divided by an assessment factor between 10 and 1000, which considers the data quality and quantity. In this work funded by the German Länder Working Party on Water (Länderarbeitsgemeinschaft Wasser – LAWA) environmental quality standards for 40 considered relevant substances were derived for aquatic ecosystems. The data sheets cover the identification of the compounds, their behaviour in the environment (physical‐chemical properties, biotic and abiotic degradation, sorption, bioaccumulation), information about mode of action, uses, analytical determination and available quality criteria. Ecotoxicological effect concentrations for bacteria, algae, protozoa, aquatic plants, crustaceans, fish, amphibians, insects and molluscs are listed. For 17 of the 40 hazardous substances investigated, quality objectives above 1 μg/L were derived. For 12 substances the values were between 0.1 μg/L and 1 μg/L and for 5 substances lower than 0.1 μg/L. Incomplete ecotoxicological data sets of the remaining compounds do not allow the derivation of quality standards. Especially for drugs further ecotoxicological test results are needed.     

The Meteoritical Bulletin,No. 93, 2008 March

Abstract— In this edition of the Meteoritical Bulletin, 1443 approved meteorite names with their relevant data are reported, one from a specific location within Africa, 211 from Northwest Africa, 5 from KOREAMET, 598 from the Chinese Antarctic Expedition, 23 from the Americas, 151 from Asia, three from Australia, two from Europe, two from NOVA, and 447 from ANSMET that were not reported in the Meteoritical Bulletin no. 87. Also reported are 4 falls from the Americas. Some highlights of approved meteorites are 10 lunar (including NWA 5000, an 11.528 kg sample), 3 Martian, 4 irons (one from Indonesia), 2 ureilites, 5 mesosiderites, 1 pallasite, 6 brachinites, 3 CV3s, 4 CO3s, 8 CMs, 12 CK3s, and many more. Finally, the Committee on Nomenclature of the Meteoritical Society announces two new names series in North America.     

Soft-sediment deformation structures in NW Germany caused by Late Pleistocene seismicity

New data on seismically triggered soft-sediment deformation structures in Pleniglacial to Late Glacial alluvial fan and aeolian sand-sheet deposits of the upper Senne area link this soft-sediment deformation directly to earthquakes generated along the Osning Thrust, which is one of the major fault systems in Central Europe. Soft-sediment deformation structures include a complex fault and fold pattern, clastic dikes, sand volcanoes, sills, irregular intrusive sedimentary bodies, flame structures, and ball-and-pillow structures. The style of soft-sediment deformation will be discussed with respect to brittle failure, liquefaction and fluidization processes, and was controlled by (1) the magnitude of the earthquake and (2) the permeability, tensile strength and flexural resistance of the alluvial and aeolian sediments. It is the first time in northern Germany that fluidization and liquefaction features can be directly related to a fault. The occurrence of seismicity in the Late Pleistocene and in the seventeenth century indicates ongoing crustal movements along the Osning Thrust and sheds new light on the seismic activity of northern Germany. The Late Pleistocene earthquake probably occurred between 15.9 ± 1.6 and 13.1 ± 1.5 ka; the association of soft-sediment deformation structures implies that it had a magnitude of at least 5.5.