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
When a satellite orbit decaying slowly under the action of air drag experiences 15th-order resonance with the Earth's gravitational field, so that the ground track repeats after 15 rev, the orbital eccentricity may suffer appreciable changes due to perturbations from the gravitational harmonics of order 15 and even degree (16, 18, 20…). In this paper the changes in eccentricity at resonance for six satellites in near-circular orbits at inclinations between 56 and 90° have been analysed to derive 11 pairs of equations linking the harmonic coefficients of order 15 and (even) degree l, in the usual notation. These equations (together with eight constraint equations) are solved to give:
We have analysed the variations of inclination in 13 satellite orbits as they pass slowly, under the action of air drag, through 15th-order resonance with the geopotential, when successive equatorial crossings are 24° apart and the ground track repeats after 15 rev. The size and form of the change in inclination are determined mainly by the values of the geopotential harmonics of 15th order and odd degree, and (with l = 15, 17, 19, …) in the usual notation. Our analysis gives values of these coefficients up to l = 33 as follows:
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
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
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
The Paleoproterozoic Ruttan Cu–Zn volcanogenic massive-sulfide (VMS) deposit is a large, relatively low grade, bimodal-siliciclastic
type deposit in the Rusty Lake volcanic belt of northern Manitoba. The deposit contained over 82.8 million tonnes of massive
sulfide, of which 55.7 million tonnes were mined from 1973 to 2002. The deposit consists of a series of moderately to steeply
dipping, south-facing lenses that extend along strike at the surface for 1.1 km and to a depth of 1.0 km. These lenses occur
within a steeply dipping, bimodal volcanic, volcaniclastic and siliciclastic sequence. In the immediate mine area, transitional
calc-alkalic to high-silica (tholeiitic), felsic, and intermediate volcanic/volcaniclastic rocks of the Mine Sequence are
host to, and intercalated with, the massive-sulfide lenses. Transitional tholeiitic to calc-alkalic basalt and andesite are
present in the footwall sequence, approximately 500 m down-section from the ore horizon. The overlying rocks are predominantly
fine-grained volcaniclastics and siliciclastics, but include polyfragmental agglomerate that contains mafic bombs and scoriaceous
felsic fragments. Syn-depositional felsic and mafic dikes, sills, and apophyses are ubiquitous throughout the Mine Sequence,
including the ore lenses, indicating continued, near-vent magmatism, and volcanism during ore formation. Fabrics in altered
hostrocks have consistent, down-plunge stretching lineations to the SSE that suggest the deposit has been elongated by a factor
of ~1.2–1.5; otherwise, the deposit is remarkably undeformed. Syn- and post-depositional faults in the mine area have relatively
minor displacements up to tens of meters. Proximal (within 200 m) footwall rocks exhibit moderate to strong chloritization,
characterized by the upper greenschist to lower amphibolite facies assemblages that include cordierite–almandine–andalusite–sillimanite–biotite ± staurolite ± anthophyllite ± talc,
and local silicification. The proximal hanging wall rocks are characterized by sericite ± gahnite alteration, which is restricted
to within approximately 75 m of the uppermost lenses. Additional gangue minerals are anhydrite and carbonate minerals (siderite,
dolomite, ankerite, and calcite), as well as chlorite, sericite, biotite, talc, and quartz. Carbonate (excluding siderite),
potassium feldspar, silicification and epidotization are common distal alteration zones in the footwall to the Mine Sequence
several kilometers to the northeast. There are three principal groups of massive sulfide lenses; the East lenses, the West
lenses, and the Western Anomaly lenses to the far west. In general, Cu is relatively enriched at the stratigraphic base and
in the center of the deposit, whereas Zn is enriched upsection and at the outer margins. Some of the Zn-rich ore exhibits
primary mineralogical layering. Parts of the West and Western Anomaly lenses show two layers with Cu-rich bases and Zn-rich
tops. The massive sulfide is typically 10–40-m thick; one area along the margin of the main lenses is over 130-m thick and
may represent deposition adjacent to a syn-depositional fault. The main sulfide phases are pyrite, pyrrhotite, chalcopyrite,
sphalerite, and galena, with tetrahedrite as the most abundant trace phase. Gahnite is ubiquitous in the chlorite-rich assemblages
adjacent to the ore lenses. The average base, precious and trace metal contents estimated from Cu and Zn concentrates, and
from millhead grades and recoveries. Metals easily transported as chloride and bisulfide complexes in hydrothermal fluids
including: Pb, Ag, In, Cu, Cd, Au, and Zn are enriched by 1.5–2.5 orders of magnitude in comparison to the bulk continental
crust. Other elements such as Sn, Mo, and As are at near-crustal concentrations, whereas Mn, Ga, and Co are significantly
depleted in comparison to the crust. Calculated metal concentrations in the average hydrothermal fluid based on the average
metal contents are comparable to, or higher than those measured at sediment covered ridge hydrothermal systems, which precipitate
much of their metal budget in the subsurface. Average rare earth element contents for the sulfide are light rare earth element
enriched (LaN/YbN=22) and range from 0.45 to 0.02x chondritic values, with a moderate negative Eu anomaly (Eu*=0.51). Metal and trace element
contents in the Ruttan exhalite horizon, and in proximal (within 1–2 km) exhalites along strike from the 0.6 million tonne
Dar-2 Cu–Zn deposit 12 km south of Ruttan, have positive Eu anomalies, whereas negative Eu anomalies are present at distance.
The positive Eu anomalies reflect high temperature paleoseafloor hydrothermal venting and precipitation of Eu2+-enriched clays and possibly carbonates, and indicate proximity to base-metal deposits. Silver and lead are also enriched
in the exhalites near the deposits, whereas Mn is enriched at ~1–3 km along strike, but not consistently.
Editorial handling: B. Gemmel
An erratum to this article is available at . 相似文献
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
