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1.
2.
The sulfate pollution in an agriculturally used watershed has been investigated with respect to the transport in the saturated zone and the development of sulfate in the unsaturated zone. Besides of other sources such as acid wet and dry deposition or sulfate input by agricultural activities, most of the sulfate originates from oxidation of pyrite by either NO3 or O2. High sulfate concentrations coincided with high nitrate leaching caused by plowing of former grassland or by vegetable crop residues and with former wet lands that have become dry. By using soil water concentration data and maps showing the extension of former wetlands and grassland as well as agricultural land use, it was possible to delineate regions of high sulfate input. The transport of sulfate in the aquifer was analyzed with a modified version of the USGS MOC model, which takes into account the nonlinearity of the underlying equation describing unconfined groundwater flow. The calibration of the transport model showed good agreement between the estimated and modeled sulfate input rates. A prediction of future sulfate concentrations in the aquifer was feasible by using worst-case parameters. 相似文献
3.
Authigenic albites in carbonate rocks typically grow in a high-grade diagenetic to low-grade metamorphic environment and often show Roc-Tourné-twinning sensu Füchtbauer. Based on an investigation of four Middle to South European occurrences, they show Mn2+- and Fe3+-activated cathodoluminescence (CL), as revealed by combined high resolution spectroscopy of cathodoluminescence emission (HRS-CL), electron paramagnetic resonance (EPR), and proton-induced X-ray emission (μPIXE). 相似文献
4.
Frank M. Richter Andrew M. Davis Denton S. EbelAkihiko Hashimoto 《Geochimica et cosmochimica acta》2002,66(3):521-540
Experiments exposing Type B calcium-, aluminum-rich inclusion (CAI)-like melts at high temperatures to high vacuum or reducing hydrogen-rich gas mixtures were used to determine the rates and consequences of elemental and isotopic fractionation by evaporation. Silicon and magnesium were found to evaporate much faster than calcium and aluminum, and the resulting residual liquid trajectories in composition space are reproduced via a thermodynamic model for the saturation vapor pressure of the evaporating species. Isotopic fractionations associated with evaporation were measured for magnesium. The resulting relationship between fraction of magnesium lost and enrichment of the residue in the heavy isotopes of magnesium follows a Rayleigh fractionation curve with a fractionation factor that is close to, but not exactly, the theoretically expected value. The rate of evaporation is found to be a strong function of temperature, oxygen fugacity, and melt composition, which can be understood and modeled in terms of the dependence of the saturation vapor pressures on these variables. The relationship between evaporation rate, which we measure, and calculated saturation vapor involves empirical evaporation coefficients that we find to be significantly less than one (∼0.1). Analytical and numerical models are used to characterize how diffusion in both the melt and in the surrounding gas affects evaporation rates and the degree of chemical and isotopic fractionation. The experimental data and theoretical considerations are combined to give a parameterization of the rates and consequences of evaporation of Type B CAI-like liquids, which is then used to translate the measured isotopic fractionation of Type B CAIs into constraints on their thermal history. Cooling rates of the order of 10°C per hour are indicated. 相似文献
5.
Gudrun Richter Joachim Wassermann Martin Zimmer Matthias Ohrnberger 《Journal of Volcanology and Geothermal Research》2004,135(4):331-342
In this paper we present densely sampled fumarole temperature data, recorded continuously at a high-temperature fumarole of Mt. Merapi volcano (Indonesia). These temperature time series are correlated with continuous records of rainfall and seismic waveform data collected at the Indonesian–German multi-parameter monitoring network. The correlation analysis of fumarole temperature and precipitation data shows a clear influence of tropical rain events on fumarole temperature. In addition, there is some evidence that rainfall may influence seismicity rates, indicating interaction of meteoric water with the volcanic system. Knowledge about such interactions is important, as lava dome instabilities caused by heavy-precipitation events may result in pyroclastic flows. Apart from the strong external influences on fumarole temperature and seismicity rate, which may conceal smaller signals caused by volcanic degassing processes, the analysis of fumarole temperature and seismic data indicates a statistically significant correlation between a certain type of seismic activity and an increase in fumarole temperature. This certain type of seismic activity consists of a seismic cluster of several high-frequency transients and an ultra-long-period signal (<0.002 Hz), which are best observed using a broadband seismometer deployed at a distance of 600 m from the active lava dome. The corresponding change in fumarole temperature starts a few minutes after the ultra-long-period signal and simultaneously with the high-frequency seismic cluster. The change in fumarole temperature, an increase of 5 °C on average, resembles a smoothed step. Fifty-four occurrences of simultaneous high-frequency seismic cluster, ultra-long period signal and increase of fumarole temperature have been identified in the data set from August 2000 to January 2001. The observed signals appear to correspond to degassing processes in the summit region of Mt. Merapi. 相似文献
6.
7.
Arzu Çöltekin Rebecca Francelet Kai-Florian Richter John Thoresen Sara Irina Fabrikant 《制图学和地理信息科学》2018,45(4):339-353
We report on how visual realism might influence map-based route learning performance in a controlled laboratory experiment with 104 male participants in a competitive context. Using animations of a dot moving through routes of interest, we find that participants recall the routes more accurately with abstract road maps than with more realistic satellite maps. We also find that, irrespective of visual realism, participants with higher spatial abilities (high-spatial participants) are more accurate in memorizing map-based routes than participants with lower spatial abilities (low-spatial participants). On the other hand, added visual realism limits high-spatial participants in their route recall speed, while it seems not to influence the recall speed of low-spatial participants. Competition affects participants’ overall confidence positively, but does not affect their route recall performance neither in terms of accuracy nor speed. With this study, we provide further empirical evidence demonstrating that it is important to choose the appropriate map type considering task characteristics and spatial abilities. While satellite maps might be perceived as more fun to use, or visually more attractive than road maps, they also require more cognitive resources for many map-based tasks, which is true even for high-spatial users. 相似文献
8.
G. A. Richter 《Astronomische Nachrichten》1986,307(4):221-230
After a survey of the latest state of knowledge on cataclysmic variables in general (Chapter 1) and recurrent novae in particular (Chapter 2), the amplitude-cycle length relationship (A-C relation) is rederived (Chapter 3) after statistical correction for published incorrect values of C. While the A-C relationship of dwarf novae is of the form A = -0.40 + 2.50 log C, it is, presumably for physical reasons less sharply defined for the few known recurrent novae. 相似文献
9.
W. R. Dick H. Lorenz P. Notni E. Schilbach R.-D. Scholz G. A. Richter 《Astronomische Nachrichten》1986,307(2):85-88
We have determined the positions of 65 compact extragalactic objects with magnitudes between 16m and 21m.7. The mean error of one position is about 0″.3 in α cos δ and in δ. Some hitherto unpublished redshifts are also listed. 相似文献
10.
G. A. Richter P. Notni F. Brngen V. Afanasjev I. D. Karachentsev A. Kopylov 《Astronomische Nachrichten》1981,302(5):211-218
With the aid of silt spectrograms gained at the 6 meter telescope Selenchukskaja and at the 2 meter telescope Tautenburg a brightness outburst (the only one so far observed) could be followed up spectroscopically. The spectral behaviour resembles SS Cygni, but the presence of CIII and NIII emission is not typical of dwarf novae. Possibly the object is related to the anomalous recurrent nova WZ Sge. The definite determination of its belonging to a known subclass of cataclysmic variables will be possible only after obtainment of extensive photometric material. 相似文献