Kohlendioxid-Messungen in einem Durchfluß-Meßsystem mit einem neu entwickelten CO₂-Sensor am Beispiel eines Hartwassersees (Willersinnweiher, Ludwigshafen am Rhein)     

Johannes Schmid  Wolfram Oelßner  Gerd Schukraft 《Limnologica》2002,32(4):338-349

The concentrations of free dissolved carbon dioxide in lake water were measured with a newly developed CO₂ sensor, which was installed in a through-flow measurement system. The results of measurements demonstrate the CO₂ dynamics in lake Willersinnweiher. The CO₂ concentrations showed a correlation with the oxidation of CH₄ in the metalimnion and caused shifts in the carbonate system, thus affecting the autochthonous precipitation and dissolution of calcite.

From the results of measurement appears that the CO₂ sensor is capable of very exact measurements of dissolved free CO₂ in lake water. At the same time, the parameter is easily determined in the field without large expenditures.  相似文献   

CELIAS - Charge, Element and Isotope Analysis System for SOHO   总被引：1，自引：0，他引：1  

D. Hovestadt  M. Hilchenbach  A. Bürgi  B. Klecker  P. Laeverenz  M. Scholer  H. Grünwaldt  W. I. Axford  S. Livi  E. Marsch  B. Wilken  H. P. Winterhoff  F. M. Ipavich  P. Bedini  M. A. Coplan  A. B. Galvin  G. Gloeckler  P. Bochsler  H. Balsiger  J. Fischer  J. Geiss  R. Kallenbach  P. Wurz  K. -U. Reiche  F. Gliem  D. L. Judge  H. S. Ogawa  K. C. Hsieh  E. Möbius  M. A. Lee  G. G. Managadze  M. I. Verigin  M. Neugebauer 《Solar physics》1995,162(1-2):441-481

The CELIAS experiment on SOHO is designed to measure the mass, ionic charge and energy of the low and high speed solar wind, of suprathermal ions, and of low energy flare particles. Through analysis of the elemental and isotopic abundances, the ionic charge state, and the velocity distributions of ions originating in the solar atmosphere, the investigation focuses on the plasma processes on various temporal and spatial scales in the solar chromosphere, transition zone, and corona. CELIAS includes 3 mass- and charge-discriminating sensors based on the time-of-flight technique: CTOF for the elemental, charge and velocity distribution of the solar wind, MTOF for the elemental and isotopic composition of the solar wind, and STOF for the mass, charge and energy distribution of suprathermal ions. The instrument will provide detailed in situ diagnostics of the solar wind and of accelerated particles, which will complement the optical and spectroscopic investigations of the solar atmosphere on SOHO. CELIAS also contains a Solar Extreme Ultraviolet Monitor, SEM, which continously measures the EUV flux in a wide band of 17 – 70 nm, and a narrow band around the 30.4 nm He II line.Principal-InvestigatorPrincipal-Investigator for data phase  相似文献   

The abundance of 3He in the solar wind - A constraint for models of solar evolution     

P. Bochsler  J. Geiss  A. Maeder 《Solar physics》1990,128(1):203-215

³He is an intermediate product in the proton-proton chain, and standard models of the Sun predict a large bulge of enhanced ³He abundance near M _r /M ₀ = 0.6 in the contemporary Sun. The relatively low abundance of ³He at the solar surface, which is derived from solar wind observations, poses severe constraints to non-standard solar models.Direct measurements of the ³He abundance in the solar atmosphere are extremely difficult, whereas indirect measurements, e.g., in the solar wind, have been performed with considerable precision. The interpretation of solar wind observations with respect to solar surface abundances has been greatly improved in recent years. Abundance measurements have been performed under a large variety of solar wind conditions and refined models have been developed for the transport processes in the chromosphere and the transition region and for the processes occurring in the solar corona. From these measurements we estimate the present isotopic number ratio ³He/⁴He to be (4.1 ± 1.0) × 10^–4 at the solar surface, corresponding to the weight abundance X ₃ = (9.0 ± 2.4) × 10^–5. The zero-age Main-Sequence abundance of ³He (after burning of D) might have been slightly lower (by about 10 to 20%) than the present-day value.Non-standard solar models involving mild turbulent diffusion (Lebreton and Maeder, 1987) could account for a slow secular increase of the ³He/⁴He ratio in the solar atmosphere. On the other hand it is difficult to reconcile models with severe mass loss as proposed by Guzik, Willson, and Brunish (1987) with this constraint. The slowing down of the solar rotation during the early Main-Sequence evolution was accompanied by stronger differential rotation probably implying a more effective mixing of the inner parts. Again, the surface abundance of ³He imposes severe limits on the evolution of the distribution of momentum within the early Sun.  相似文献   

Interactions of calcium and fulvic acid at the goethite-water interface   总被引：6，自引：0，他引：6  

Li Ping Weng  Luuk K. Koopal  Johannes C.L. Meeussen 《Geochimica et cosmochimica acta》2005,69(2):325-339

  相似文献   

Eclogite-facies vein systems in the Marun-Keu complex (Polar Urals,Russia): textural,chemical and thermal constraints for patterns of fluid flow in the lower crust   总被引：1，自引：0，他引：1  

José?F.?MolinaEmail author  Stefano?Poli  H?kon?Austrheim  Johannes?Glodny  Anatolij?Rusin 《Contributions to Mineralogy and Petrology》2004,147(4):484-504

Metasomatic amphibole-eclogite sequences grew in selvages of quartz veins from the Marun-Keu complex (Polar Urals, Russia) during high-pressure metamorphism. Relicts of a pre-metasomatic eclogite-facies assemblage are present in the wallrock layers as irregular patches. Wallrock interstitial quartz trails lying at a high angle to reaction fronts provide evidence for grain-scale pore channelisation which may be produced by intergranular-fluid compositional gradients parallel to the quartz trails. Disequilibrium at vein-wallrock scale is inferred from wallrock mineral heterogeneity and from variable initial Sr isotope ratios in mineral separates. Mass-balance calculations between relicts and wallrock assemblages reveal chemical imbalances caused by open system-behaviour with two way mass-transfer. The vein-wallrock system registers a prograde history from 408–434 °C (relicts) to 526–668 °C (vein precipitates). Vein and metasomatic assemblages formed during a single fluid-rock interaction process, implying high heating rates (100 °C/Ma), which could result from heat advection by large-scale fluid circulation.Editorial responsibility: W. Schreyer  相似文献   

Stress indicators adjacent to buried channels of Elsterian age in North Germany     

Johannes Bruns 《第四纪科学杂志》1989,4(3):267-272

Tectonic and soil mechanics investigations of a strongly plastic clay (Miocene ‘Mica Clay’) led to the detection of strain phenomena induced in connection with the formation of Elsterian buried channels. A microjoint system with randomly distributed fissures is thought to result from early Elsterian dessiccation and frost crack formation. It occurs frequently in the upper part of the clay horizon. A younger joint system, which is encountered throughout the entire clay body, comprises macrojoints arranged in three joint sets. The evidence strongly suggests that they were formed by gravitational and kinematic loading of the clay body by overriding ice. The macrojoints display various secondary alterations such as slickensides, escarpments, shear zones, erosive and pressure zones, the formation of which is seen in context with the channel incision. Investigations into the genesis of these alterations indicate a strong horizontally-orientated stress induction lateral to the channels, which resulted in stiffness modulus anisotropy. It has also caused a horizontal compression of the clay body, which at that time was already consolidated through ice overburdening. Horizontal compression of the clay led to evorsion of pore water eroding clay particles from the joint walls. Lower water content of the clay, in combination with increased dry unit weights, are found adjacent to the channels today.  相似文献   

A comparison of a GCM response to historical anthropogenic land cover change and model sensitivity to uncertainty in present-day land cover representations   总被引：5，自引：1，他引：5  

Johannes Feddema  Keith Oleson  Gordon Bonan  Linda Mearns  Warren Washington  Gerald Meehl  Douglas Nychka 《Climate Dynamics》2005,25(6):581-609

This study assesses the sensitivity of the fully coupled NCAR-DOE PCM to three different representations of present-day land cover, based on IPCC SRES land cover information. We conclude that there is significant model sensitivity to current land cover characterization, with an observed average global temperature range of 0.21 K between the simulations. Much larger contrasts (up to 5 K) are found on the regional scale; however, these changes are largely offsetting on the global scale. These results show that significant biases can be introduced when outside data sources are used to conduct anthropogenic land cover change experiments in GCMs that have been calibrated to their own representation of present-day land cover. We conclude that hybrid systems that combine the natural vegetation from the native GCM datasets combined with human land cover information from other sources are best for simulating such impacts. We also performed a prehuman simulation, which had a 0.39 K ~higher average global temperature and, perhaps of greater importance, temperature changes regionally of about 2 K. In this study, the larger regional changes coincide with large-scale agricultural areas. The initial cooling from energy balance changes appear to create feedbacks that intensify mid-latitude circulation features and weaken the summer monsoon circulation over Asia, leading to further cooling. From these results, we conclude that land cover change plays a significant role in anthropogenically forced climate change. Because these changes coincide with regions of the highest human population this climate impact could have a disproportionate impact on human systems. Therefore, it is important that land cover change be included in past and future climate change simulations.  相似文献   

A unified global height reference system as a basis for IGGOS   总被引：1，自引：0，他引：1  

Johannes Ihde  Laura Snchez 《Journal of Geodynamics》2005,40(4-5):400

The definition of a global height reference system is based on a mean sea surface, gravity field parameters, and a three-dimensional terrestrial reference frame (TRF). Tide gauge records, satellite altimetry, gravity measurements on Earth and from space, TRF coordinates, and spirit levelling have to be combined for the realization of the vertical reference frame. Observations and parameters have to be consistent with respect to the used standards, conventions and models. They have to provide globally unified reference surfaces (geoid or quasigeoid, respectively, and mean sea surface). The continental reference systems of Europe (EUREF, ECGN) and South America (SIRGAS) are considering these requirements in their strategies. They are presented here, and slightly different definitions and realizations for a globally unified height reference system are discussed.  相似文献   

In situ measurements of sediment settling characteristics in floodplains using a LISST‐ST     

Ivo Thonon  Johannes R. Roberti  Hans Middelkoop  Marcel van der Perk  Peter A. Burrough 《地球表面变化过程与地形》2005,30(10):1327-1343

Due to a lack of data on settling velocities (w_s) and grain size distributions (GSDs) in ?oodplain environments, sedimentation models often use calibrated rather than measured parameters. Since the characteristics of suspended matter differ from those of deposited sediment, it is impossible to derive the w_s and GSD from the latter. Therefore, one needs to measure in situ suspended sediment concentrations (SSCs), settling velocities, effective grain sizes and sedimentation ?uxes. For this purpose we used the LISST‐ST, a laser particle sizer combined with a settling tube. In 2002 (twice) and 2004, we located the LISST‐ST with an optical backscatter sensor and sediment traps in two ?oodplains in The Netherlands: one along the unembanked IJssel River, another along the embanked Waal River. Measurements revealed that the SSC in the ?oodplains varied in relation to the SSC in the river channel. Smaller ?ocs dominated the SSC, while larger ?ocs dominated the potential sedimentation ?uxes. The in situ GSD in the IJssel ?oodplain was signi?cantly coarser than in the Waal ?oodplain, while the dispersed median grain sizes were equal for both ?oodplains. Therefore, the dispersed median grain size was two to ?ve times smaller than the effective one. The in situ grain size exhibited a signi?cant positive relationship with w_s, although the w_s for the largest ?ocs showed high variability. Consequently, the variability in sedimentation ?uxes was also large. In the actual sedimentation ?uxes, and hence in sedimentation models, in situ grain sizes up to about 20 µm can be neglected. In ?oodplain sedimentation models the relation between settling velocity and in situ grain size can be used instead of Stokes's law, which is only valid for dispersed grain sizes. These models should also use adequate data on ?ow conditions as input, since these strongly in?uence the suspended sediment characteristics. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

Numerical modeling of contaminant transport resulting from dissolution of a coal-tar pool in an experimental aquifer     

Kenneth Y. Lee  Johannes Khinast  Jung-Hoon Kim 《Hydrogeology Journal》2007,15(4):705-714

A previously developed two-dimensional numerical model is further developed for simulating the transport of dissolved contaminants originating from dissolution of a coal tar pool in a stratified, saturated porous medium. The model is used to simulate contaminant transport resulting from a rectangular-shaped coal-tar-pool dissolution experiment conducted in a large-scale experimental aquifer. The experimental porous medium consists of two sand strata, a high-hydraulic-conductivity upper stratum and a low-hydraulic-conductivity bottom stratum. The experiment was conducted to a time of 354 days and the groundwater velocity was changed several times within this duration. Model simulations show good agreement against observed contaminant concentrations, and simulations show that dissolved solute below the pool migrated deeper into the bottom stratum as compared to the upper stratum. Furthermore, simulations also suggest that contaminant concentrations in the lower stratum never reached quasi steady-state during the experimental time frame.  相似文献