Correlation between microbiological and chemical parameters of some hydrothermal springs in New Mexico, USA

Discharge areas of hydrothermal springs are known to be inhabited by diverse types of microorganisms including archaea, prokaryotes and eukaryotes. A total of 11 hydrothermal samples from the Rio Grande rift and the Valles caldera in New Mexico were analyzed to investigate the correlation between chemical and microbiological parameters of hydrothermal waters. The sampled fluids are categorized into three chemical groups: (I) steam-condensing acid sulfate waters, (II) deep geothermal and derivative waters and (III) thermal meteoric waters. Analyses of the microbial phospholipid fatty acids and denaturing gradient gel electrophoresis of DNA show that acid sulfate waters were populated by thermoacidophilic organisms and had high biomass content. Mineralized deep geothermal and derivative waters exhibited a high degree of microbial diversity, but had low biomass content. Thermal meteoric waters are low in total dissolved solids, and exhibit very low biomass content and microbial diversity. DNA sequences from several previously unknown microbial species were detected. The results of this study support the hypothesis that microbes can be used as tracers for specific types of subsurface environments.     

Effect of soil crusting on the emission and transport of wind-eroded sediment: field measurements on loamy sandy soil

Field data are reported for the horizontal and vertical flux of wind-eroded sediment on an agricultural field in northern Germany. Measurements were made during a windstorm that hit the region on 18 May 1999. The magnitude of both fluxes was significantly affected by the presence of a surface crust covering the test field. Measuring the physical crust strength at 45 locations with a torvane, the relationships between crust strength (τ) and the horizontal (F_h) and vertical (F_v) sediment fluxes were investigated. Both fluxes decreased as the surface crust became stronger. The decay behaved as an exponential function for both types of flux. The horizontal sediment flux over a crusted surface can be accurately predicted by completing Marticorena and Bergametti's [Journal of Geophysical Research 100 (1995) 16415] erosion model with a crust function. The vertical particle flux over crusted soil can be calculated by adding a similar function to Alfaro and Gomes's [Journal of Geophysical Research 106D (2001) 18075] dust production model. The study also suggests that the gradual bombardment of a surface crust by impacting particles does not immediately result in a decay of the crust's protective effect, provided that the crust has a minimum thickness. However, once the crust becomes perforated, its protective effect disappears very quickly, leading to much higher horizontal and vertical sediment fluxes than predicted for undamaged crusted soil.     

Thermochemistry of jarosite-alunite and natrojarosite-natroalunite solid solutions

The thermochemistry of jarosite-alunite and natrojarosite-natroalunite solid solutions was investigated. Members of these series were either coprecipitated or synthesized hydrothermally and were characterized by XRD, FTIR, electron microprobe analysis, ICP-MS, and thermal analysis. Partial alkali substitution and vacancies on the Fe/Al sites were observed in all cases, and the solids studied can be described by the general formula K_1-x-yNa_y(H₃O)_xFe_zAl_w(SO₄)₂(OH)_6-3(3-z-w)(H₂O)_3(3-z-w). A strong preferential incorporation of Fe over Al in the jarosite/alunite structure was observed. Heats of formation from the elements, ΔH°_f, were determined by high-temperature oxide melt solution calorimetry. The solid solutions deviate slightly from thermodynamic ideality by exhibiting positive enthalpies of mixing in the range 0 to +11 kJ/mol. The heats of formation of the end members of both solid solutions were derived. The values ΔH°_f = −3773.6 ± 9.4 kJ/mol, ΔH°_f = −4912.2 ± 24.2 kJ/mol, ΔH°_f = −3734.6 ± 9.7 kJ/mol and ΔH°_f = −4979.7 ± 7.5kJ/mol were found for K_0.85(H₃O)_0.15Fe_2.5(SO₄)₂(OH)_4.5(H₂O)_1.5, K_0.85(H₃O)_0.15Al_2.5(SO₄)₂(OH)_4.5(H₂O)_1.5, Na_0.7(H₃O)_0.3Fe_2.7(SO₄)₂(OH)_5.1(H₂O)_0.9, and Na_0.7(H₃O)_0.3Al_2.7(SO₄)₂(OH)_5.1(H₂O)_0.9 respectively. To our knowledge, this is the first experimentally-based report of ΔH°_f for such nonstoichiometric alunite and natroalunite samples. These thermodynamic data should prove helpful to study, under given conditions, the partitioning of Fe and Al between the solids and aqueous solution.     

A comparison of stygofauna communities inside and outside groundwater bores

Sampling stygofauna is both time consuming and labour intensive. The challenge is to get samples from as many bores as possible within a limited time. The essential assumption for this is that faunal communities inside bores are comparable and representative of the communities outside.To compare relative abundance, taxonomic richness and community composition of the fauna inside groundwater bores to the fauna of the surrounding aquifer, 20 monitoring bores in Palatinate, southwestern Germany, were sampled twice in 1 month. Initially, a sample of 4 l of water was collected from the bottom of each bore. A further sample of 51 l was collected from the groundwater surrounding the bore using a pneumatic piston pump with double packer sampler.Water chemistry inside and outside the bore was similar, but the relative amounts of sediments within the bores were higher compared to those from outside. Relative abundances of fauna inside the bores were higher than in the aquifer, but taxonomic composition was similar with the exception of the proportions of nematodes and amphipods, which were higher inside. As a result, the proportions of cyclopoids were lower inside. Higher nematode proportions are explained partially by the nearly complete extraction of bore sediment. A “habitat heterogeneity effect” states that in heterogeneous aquifers with few suitable habitats, faunal distribution is supposed to be extremely patchy. Thus, detritus accumulates in bores, attracting animals and providing “habitat islands” in the groundwater. This effect could explain the higher amphipode proportions inside the bores, which were generally more frequently populated than the surrounding groundwater. As a consequence, fauna is thought to be nearly absent from groundwater, where suitable habitats are lacking. In those sparsely populated aquifers, samples representative of the aquifer taxonomic richness and composition can only be collected by removing large volumes of water, or by sampling the bottom of bores. These findings also suggest that the use of unbaited colonisation chambers or traps in the groundwater, which are comparable with bores, would seem to be a promising approach.     

Efficient finite-difference modelling of seismic waves using locally adjustable time steps

Conventional finite-difference modelling algorithms for seismic forward modelling are based on a time-stepping scheme with a constant (global) time step. Large contrasts in the velocity model or in the spatial sampling rate cause oversampling in time for some regions of the model. The use of locally adjustable time steps can save large amounts of computation time for certain modelling configurations. The computation of spatial derivatives across the transition zone between regions of the model with different temporal sampling requires the definition of the wavefield at corresponding time levels on both sides of the transition zone. This condition can be obtained by extrapolation in time, which is inaccurate, or by multiple time integration in the transition zone. The error in the latter solution is of the same order as the conventional time-stepping scheme because both methods are based on the same iteration formula. The technique of multiple time integration simply requires the use of different sizes of time step. It is applicable only for certain factors of variation of the time step.     

Synsedimentäre Gleitschollen großen Ausmaßes im terrestrischen Jungtertiär der Karawanken

Zusammenfassung Während der Sedimentation der Rosenbacher Kohleschichten (W.Klaus 1956, Untersarmat) spielten die Karawanken als Liefergebiet der Sedimente kaum eine Rolle. Wie aus der Verbreitung dieser Sedimente im Bereich des Karawankenkörpers zu erkennen ist, wurden zumindest seine nördlichen Teile damit bedeckt. Im Hangenden dieser, aus gut gerollten, tonig sandigen Kiesen (mit hohem Quarzanteil) gebildeten Rosenbacher Kohleschichten treten dann die ersten deutlichen Einschüttungen aus den Karawanken auf. Diese deuten auf eine beginnende Heraushebung hin. Ihre Geröllzusammensetzung zeigt an, daß am Beginn dieser Entwicklung noch ein deutlicher Gerölltransport aus dem Bereich der Periadriatischen Naht über den Nordstamm der Karawanken stattfand.Die fortschreitende Heraushebung unterbrach diese Transportwege und führte zum Lösen großer Schollen von Wettersteinkalk, die nach Norden abglitten. Begünstigt wurde dieser Vorgang durch die Unterlagerung des Wettersteinkalkes durch mächtige Raibler Schiefer, die als Gleitmittel dienten.Die abgeglittenen Schollen (Tafeln bis zu 100–150 m Mächtigkeit und Längserstreckungen bis 2000 m) wurden dann in die grobklastischen Sedimente des Vorlandes konkordant eingelagert. Beide Vorgänge, Lösen und Abgleiten ins Vorland dieser Tafeln deuten auf eine rasche Hebung des Karawankenkörpers hin.Die weitere Hebung brachte dann nur noch sehr grobe Karbonatkiese, die die hangenden Anteile des grobklastischen Jungtertiärs (Bärental Konglomerat) bilden.In der weiteren Folge wurden diese Sedimente noch vom Karawankenkörper über eine kurze Strecke überschoben und auch in die fortschreitende Hebung (Ostteile) miteinbezogen.

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During the sedimentation of the Rosenbacher Kohleschichten (W.Klaus 1956, Untersarmat) the Karawanken were not so important for yielding sediments. As to be seen by the distribution of these sediments in the Karawanken area, at least its northern parts were covered by them. The top layers of the Rosenbacher Kohleschichten, consisting of clayey, sandy, well shaped gravels (with a high percentage of quartz) show first strong embankments from the Karawanken indicating a beginning uplift. Their gravel composition assigns that at the beginning of this development there was yet a transport northward from the area of the Periadriatische Naht through the Nordstamm of the Karawanken on many places.The proceeding uplift interrupted some of these spillways and lead to a discharge of large plates of Wettersteinkalk which glided northward. This procedure was favored by the thick Raibler Schiefer underlying the Wettersteinkalk and working as a lubricant.The down-glided plates (to 100–200 m thickness and a width up to 2000 m) were then embedded concordantly in the coarse clastic sediments of the forelands. Both, discharge and gliding of the plates point to a quick uplift of the Karawanken during Obersarmat.The further uplift yielded only very coarse carbonate gravels forming the top layers of the coarse clastic Young Tertiary (Bärental Konglomerat).Henceforth these sediments were overthrust by the Karawankenbody over a short distance and included in the advancing uplift (Eastern parts).

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Résumé Pendant la sédimentation des Rosenbacher Kohleschichten (W. Klaus 1956, Sarmatien inférieur) les Karawanken ne jouaient pas un grand rôle dans l'apport de sédiments. Tout au moins les sédiments couvraient-ils les pentes nord des Karawanken. Le toit des Rosenbacher Kohleschichten (formées par les graviers sableux et argileux, bien roulés, avec quartz abondant) montrent les premiers remblaiements provenant des Karawanken. Ceuxci indiquent le commencement du soulèvement des Karawanken. La composition des galets indiquent que, au commencement de ce développement, il y avait encore un transport bien marqué de galets depuis la suture périadriatique par dessus le rameau septentrional des Karawanken. Le soulèvement progressif interrompit cette voie de transport et conduisit à la séparation des grands blocaux du Wettersteinkalk, qui glissèrent vers le Nord. Ce processus était favorisé par la présence d'une puissante couche de Schistes de Raibler en-dessous du Wettersteinkalk, agissant comme lubrifiant.Puis les blocaux entraînés (des plaques de 100 à 200 m. d'épaisseur, jusqu'à 2000 m. de long), venaient s'intercaler en concordance dans les sédiments clastiques grossiers de l'avant-pays. Les deux phénomènes, séparation et glissement de ces plaques dans l'avantpays, indiquent un soulèvement rapide des Karawanken. Le soulèvement ultérieur ne délivra que de gros cailloux carbonatiques qui forment la partie supérieure du Miocène clastique (Bärentalkonglomerat).Dans la suite, ces sédiments furent chevauchés sur une courte distance par les Karawanken et impliqués aussi dans le soulèvement encore en cours (partie orientale).

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东北太平洋天然气水合物伴生沉积物中自生石膏矿物

自生微球粒状石膏集合体和颗粒状石膏集合体被首次发现于东北太平洋水合物脊海区的两个沉积物钻孔SO143-221和SO143/TVG40-2中. X光粉晶衍射和电子探针分析表明, 上述两种不同形态的集合体内矿物晶体均具有典型的石膏衍射峰和化学成分, 其中主要化学组成略小于其他海区自生石膏. 扫描电子显微镜分析显示, 石膏呈清晰的单晶和双晶, 清晰的晶体边界、晶面、晶棱和解理面. 结合沉积物岩芯中已发现的与水合物伴生的自生碳酸盐岩和富含SO₄^2-和Ca²⁺离子的孔隙水, 有理由认为这类石膏是自生形成于与水合物相关的沉积环境中, 很可能形成于研究区富含SO₄^2-离子的海底水与下伏沉积物中甲烷水合物层之间的交互地段. 自生的颗粒状石膏集合体和石膏微球粒集合体分别产自同一研究区不同的钻孔沉积物内, 说明了两个钻孔位置处在不同的微地球化学动力环境. 因此, 这种特征性自生石膏可视作一种识别标志应用于其他海区, 以确定其沉积环境是否与天然气水合物有关.     

Analytical 3D views and virtual globes — scientific results in a familiar spatial context

In this paper we introduce analytical three-dimensional (3D) views as a means for effective and comprehensible information delivery, using virtual globes and the third dimension as an additional information carrier. Four case studies are presented, in which information extraction results from very high spatial resolution (VHSR) satellite images were conditioned and aggregated or disaggregated to regular spatial units. The case studies were embedded in the context of: (1) urban life quality assessment (Salzburg/Austria); (2) post-disaster assessment (Harare/Zimbabwe); (3) emergency response (Lukole/Tanzania); and (4) contingency planning (faked crisis scenario/Germany). The results are made available in different virtual globe environments, using the implemented contextual data (such as satellite imagery, aerial photographs, and auxiliary geodata) as valuable additional context information. Both day-to-day users and high-level decision makers are addressees of this tailored information product. The degree of abstraction required for understanding a complex analytical content is balanced with the ease and appeal by which the context is conveyed.     

A wind-driven model of the ocean surface layer with wave radiation physics

Ocean Dynamics - Surface windstress transfers energy to the surface mixed layer of the ocean, and this energy partly radiates as internal gravity waves with near-inertial frequencies into the...