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1.
Mineral extraction and processing, especially metal mining, produces crushed and milled waste; such material, exposed to weathering, poses the potential threat of environmental contamination. In this study, mill tailings from inactive Pb-Zn mines in New Mexico, southwest USA, have been examined for their potential environmental impacts by means of detailed mineralogical and geochemical characterization. The principal ore minerals remaining in the tailings material are sphalerite, chalcopyrite, and very minor galena, smithsonite, and cerrusite, accompanied by the gangue minerals pyrite, pyrrhotite, magnetite, hematite, garnet, pyroxene, quartz, and calcite. White precipitate occurring on tailings surfaces is composed of gypsum and hydrated magnesium sulfates. Pyrite is mostly unaltered or shows only micron-scale rims of oxidation (goethite/hematite) in some surface samples. This iron oxide rim on pyrite is the only indication of weathering-derived minerals found by microscopy. There are variations in element concentrations with depth that reflect primary variations through time as the tailings ponds were filled. Cadmium and Zn concentrations increase with depth and Ag and Pb are low for the uppermost core samples, while Cu, Ni, and Co concentrations are generally high for the uppermost core samples. These elemental distributions indicate that little or no leaching has taken place since emplacement of the tailings because no accumulation or enrichment of these metals is observed in Hanover tailings, even in reducing portions of tailings piles. Element concentrations of surface samples surrounding the tailings reflect underlying mineralized zones rather than tailings-derived soil contamination. We observed no successive decreasing metal concentrations in prevalent wind directions away from the tailings. Stream sediment samples from Hanover Creek have somewhat elevated Zn, Cd, and Pb concentrations in areas that receive sediments from erosion of the tailings. However, input from tributaries downstream of the ponds appears to be principal source of heavy metals in Hanover Creek. The results of this study indicate that there is low risk for groundwater heavy-metal contamination from Hanover tailings. Tailings material do not show significant geochemical oxidation/alteration or metal leaching with depth. Our studies indicate that neutralizing minerals present in the tailings are sufficient to keep the tailings material chemically stable. Geochemically, however, tailings materials are being eroded and may pose a threat to Hanover Creek via siltation. 相似文献
2.
Joseph S. Walder 《Bulletin of Volcanology》2000,62(2):105-118
Received: 15 March 1999 / Accepted: 9 December 1999 相似文献
3.
High-resolution numerical simulations reveal the turbulent character of the interaction zone of colliding, radiative, hypersonic
flows. As the shocked gas cools radiatively, the cooled matter is squeezed into thin, high density shells. The remaining
kinetic energy causes supersonic turbulence within these shells, before it is finally dissipated by internal shocks and vortex
cascades. The density is far from homogeneous. High density filaments and large voids coexist. Its mean value is significantly
below the stationary value. Similarly, areas with supersonic velocities are found next to subsonic regions. The mean velocity
is slightly below or above the sound speed. While quasi uniform flow motions are observed on smaller scales the large scale
velocity distribution is isotropic. Part of the turbulent shell is occupied by relatively uniform flow-patches, resembling
coherent structures. Astronomical implications of the turbulent interaction zone are multifarious. It probably drives the
X-ray variability in colliding wind binaries as well as the surprising dust formation on orbital scales in some WR-binaries.
It lets us understand the knotty appearance of wind-driven structures as planetary and WR-ring nebulae, symbiotics, supernova
remnants, galactic supperbubbles. Also, WR and other radiatively driven, clumpy winds, advection dominated accretion, cooling
flows and molecular cloud dynamics in star-forming regions may carry its stamp
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
4.
We present a survey of different kinds of instabilities in the context of radiative colliding flows which greatly contribute
to structure formation. In particular, this includes analytical results for different kinds of thin shell instabilities (DI,
NDI, NTSI). New numerical results for the non-linear evolution of such instabilities in two dimensions, and their coupling
with the thermal cooling instability are presented. The astrophysical implications are briefly outlined, in particular the
formation of knots and filaments.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
5.
Fundamental differences between SPH and grid methods 总被引：1，自引：0，他引：1
Oscar Agertz Ben Moore Joachim Stadel Doug Potter Francesco Miniati Justin Read Lucio Mayer Artur Gawryszczak rey Kravtsov Åke Nordlund Frazer Pearce Vicent Quilis Douglas Rudd Volker Springel James Stone Elizabeth Tasker Romain Teyssier James Wadsley Rolf Walder 《Monthly notices of the Royal Astronomical Society》2007,380(3):963-978
6.
During a 3-year period, several aspects of the glacier-rock interface were studied in a cavity beneath 5–8 m of ice near the terminus of Grinnell Glacier, Montana, U.S.A. Continuous week-long records of the summer sliding rate revealed a very uniform speed of about 12 m a?1 during the summer, a value about 20 per cent higher than the average annual sliding rate. Several decimetre-sized rock fragments were broken from the glacier bed near the lee sides of bedrock ledges and transported down-glacier. In the course of a two-week long experiment, the glacier abraded its bed significantly and non-uniformly. It is of interest that significant quarrying and abrasion occurred under thin ice with relatively little entrained debris. 相似文献
7.
K. V. Mardia V. B. Nyirongo A. N. Walder C. Xu P. A. Dowd R. J. Fowell J. T. Kent 《Mathematical Geology》2007,39(4):355-381
This paper deals with the problem of estimating fracture planes, given only the data at borehole intersections with fractures.
We formulate an appropriate model for the problem and give a solution to fitting the planes using a Markov chain Monte Carlo
(MCMC) implementation. The basics of MCMC are presented, with particular emphasis given to reversible jump, which is required
for changing dimensions. We also give a detailed worked example of the MCMC implementation with reversible jump since our
implementation relies heavily on this new methodology. The methods are tested on both simulated and real data. The latter
is a unique data set in the form of a granite block, which was sectioned into slices. All joints were located and recorded,
and the joint planes obtained by stacking strike lines.
This work is important in the risk assessment for the underground storage of hazardous waste. Problems and extensions are
discussed. 相似文献
8.
The Usoi dam was created in the winter of 1911 after an enormous seismogenic rock slide completely blocked the valley of the
Bartang River in the Pamir Mountains of southeastern Tajikistan. At present the dam impounds 17 million cubic meters of water
in Lake Sarez. Flood volume and discharge estimates were made for several landslide generated floods that could overtop the
dam. For landslide volumes of 200, 500, and 1,000 million cubic meters, estimated overtopping flood volumes were 2, 22, and
87 million cubic meters of water, respectively. Estimated peak discharge at the dam for these three flood scenarios were 57,000,
490,000, and 1,580,000 m3/s, based on triangular hydrographs of 70-, 90-, and 110-s durations, respectively. Flood-routing simulations were made for
the three landslide-induced overtopping floods over a 530-km reach of the Bartang and Panj Rivers below the Usoi dam. A one-dimensional
flow model using a Riemann numerical solution technique was selected for the analysis. For the 87 million cubic meter volume
overtopping flood scenario, the peak flows were approximately 1, 100, 800, and 550 m3/s at locations 50, 100, and 150 km downstream of the dam respectively. 相似文献
9.
Rolf Walder 《Astrophysics and Space Science》1998,260(1-2):243-252
The properties of the interaction region of colliding winds in hot star binaries and evolved low mass binaries are discussed
in the frame of 2D and 3D hydrodynamical numerical simulations. The emission of such systems and their nebulae, in particular
in X-rays, is reviewed and new results regarding orbital line profile variations are presented. The connection between colliding
winds, thin shell instabilities and structure formation is outlined.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
10.
The link between gas dynamical models and observations is crucial. The general progress in numerical simulations must be accompanied
by predictions for observable quantities, which not only allow to test the models or parts of them against observations but
which also improve the understanding of observational data. In this paper we focus on predictions for observations, for three
examples of 3Dhydrodynamical simulations of binary star systems, and the techniques required for their derivation. The examples
include synthetic, optically thin Doppler broadened line profiles for colliding wind symbiotic binaries, the UV light curve
of an accretion model for the symbiotic binary RW Hya, and the X-ray light curve of the WR+O binaryγ Velorum. The main purpose
is to emphasize the importance of such studies and to illustrate the capabilities of the emploiedtools. The tools are all
contained in the A-MAZE code package we have developed and are publicly available.
Seminar for Applied Mathematics
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献