Metal extractability in acidic and neutral mine tailings from the Cartagena-La Unión Mining District (SE Spain)     

Héctor M. Conesa  Brett H. Robinson  Rainer Schulin  Bernd Nowack 《Applied Geochemistry》2008

Mine tailings are ubiquitous in the landscapes of mined areas. Metal solubilities were compared in two chemically distinct mine tailings from the old Mining District of Cartagena-La Unión (SE Spain). One of the tailings was acidic (pH 3.0) with 5400 mg/kg Zn, 1900 mg/kg As and 7000 mg/kg Pb. The other was neutral (pH 7.4) with 9100 mg/kg Zn, 5200 mg/kg Pb and 350 mg/kg As. In samples from the acidic tailings, more than 15% of the Zn and 55% of the Cd were extractable with 0.1 M NaNO₃, and distilled water. In the neutral tailings, using the same reagents, less than 1% of the metals were extractable. A sequential extraction procedure revealed that the sum of the residual and the Fe oxide fractions of Cu, Zn and Pb comprised 80–95% in the acidic tailings and 70–90% in the neutral tailings. The acidic mine tailings had a higher metal solubility, resulting in more metal leaching in the short-term, but also a higher fraction of inert metal. In contrast, in the neutral tailings, the metals were evenly distributed between, oxides and the residual fraction. This implies lower metal mobility in the short-term, but that metal mobility may increase in the long-term. When applied to mine tailings, sequential extractions may provide misleading results because the strong cation exchange capacity of some extractants may induce pH changes and thereby significantly change metal solubility.  相似文献   

Evidence for long-term instability in the Storegga Slide region off western Norway   总被引：1，自引：0，他引：1  

D. Evans  E. L. King  N. H. Kenyon  C. Brett  D. Wallis 《Marine Geology》1996,130(3-4):281-292

Shallow-seismic surveys around the Storegga Slide off western Norway have allowed greater understanding of the development of this part of the European margin. The northern flank of the scarp is formed of seismically well-layered, hemipelagic and distal-glaciomarine deposits in which a variety of luid-escape structures, probably due to gas, are locally abundant. There is evidence of slides that substantially pre-date the earliest slide previously recognized. Surveying on the North Sea Fan to the southwest of the Storegga Slide shows the markedly different nature of the autochthonous sediments on the southern flank of the Storegga Slide; there is a predominance of glacigenic debris flows in the upper part of the sequence, lesser maximum slopes, and an apparent absence of interstitial gas and/or hydrates. This contrast has had considerable effect on slope stability and has influenced the position of the southwestern Storegga Slide boundary. The North Sea Fan succession includes at least three major buried slides, termed the Vigra, Møre and Tampen slides, all of which substantially pre-date the Storegga event and probably pre-date predominantly glacigenic margin sedimentation. Post-late Weichselian slope failure is locally significant. The region has a long, but as yet chronologically poorly defined history of instability in which seismic triggering is considered to have been important.  相似文献   

Persistence of yessotoxin under light and dark conditions     

Mitrovic SM  Hamilton B  McKenzie L  Furey A  James KJ 《Marine environmental research》2005,60(3):397-401

The change in concentration of the disulfated polyether yessotoxin (YTX) produced by a culture of the marine dinoflagellate Protoceratium reticulatum was measured in laboratory experiments under light and dark conditions. Experimental cultures were inoculated and grew at a growth rate of 0.14 d(-1) until stationary phase was reached, after approximately 21 days. Cultures were maintained in the stationary phase until 31 days after inoculation. Cells of P. reticulatum contained a concentration of approximately 10-15 pg YTX cell(-1) during stationary phase but this was considerably lower (<5 pg cell-1) during the growth phase. Low amounts of 45-hydroxy-YTX were also detected. At day 32, P. reticulatum was killed by cooling to 1 degrees C (confirmed microscopically) and YTX concentrations were measured periodically under light and dark conditions. YTX concentrations decreased rapidly to approximately 10% of the initial concentration within the first 3 days and depleted to near zero within a week in the light treatment. In the dark environment, YTX persisted longer with approximately 10% of the initial YTX concentration still remaining after 18 days.  相似文献   

Using long-term transit timing to detect terrestrial planets     

Jeremy S. Heyl †  Brett J. Gladman † 《Monthly notices of the Royal Astronomical Society》2007,377(4):1511-1519

We propose that the presence of additional planets in extrasolar planetary systems can be detected by long-term transit timing studies. If a transiting planet is on an eccentric orbit then the presence of another planet causes a secular advance of the transiting planet's pericentre over and above the effect of general relativity. Although this secular effect is impractical to detect over a small number of orbits, it causes long-term differences when future transits occur, much like the long-term decay observed in pulsars. Measuring this transit-timing delay would thus allow the detection of either one or more additional planets in the system or the first measurements of non-zero oblateness ( J ₂) of the central stars.  相似文献   

In situ Mixing of Organic Matter Decreases Hydraulic Conductivity of Denitrification Walls in Sand Aquifers   总被引：2，自引：0，他引：2  

Gregory F. Barkle  Louis A. Schipper  Craig P. Burgess  Brett D.M. Painter 《Ground Water Monitoring & Remediation》2008,28(1):57-64

In a previous study, a denitrification wall was constructed in a sand aquifer using sawdust as the carbon substrate. Ground water bypassed around this sawdust wall due to reduced hydraulic conductivity. We investigated potential reasons for this by testing two new walls and conducting laboratory studies. The first wall was constructed by mixing aquifer material in situ without substrate addition to investigate the effects of the construction technique (mixed wall). A second, biochip wall, was constructed using coarse wood chips to determine the effect of size of the particles in the amendment on hydraulic conductivity. The aquifer hydraulic conductivity was 35.4 m/d, while in the mixed wall it was 2.8 m/d and in the biochip wall 3.4 m/d. This indicated that the mixing of the aquifer sands below the water table allowed the particles to re-sort themselves into a matrix with a significantly lower hydraulic conductivity than the process that originally formed the aquifer. The addition of a coarser substrate in the biochip wall significantly increased total porosity and decreased bulk density, but hydraulic conductivity remained low compared to the aquifer. Laboratory cores of aquifer sand mixed under dry and wet conditions mimicked the reduction in hydraulic conductivity observed in the field within the mixed wall. The addition of sawdust to the laboratory cores resulted in a significantly higher hydraulic conductivity when mixed dry compared to cores mixed wet. This reduction in the hydraulic conductivity of the sand/sawdust cores mixed under saturated conditions repeated what occurred in the field in the original sawdust wall. This indicated that laboratory investigations can be a useful tool to highlight potential reductions in field hydraulic conductivities that may occur when differing materials are mixed under field conditions.  相似文献   

Intelligent ship traffic monitoring for oil spill prevention: risk based decision support building on AIS     

Eide MS  Endresen O  Brett PO  Ervik JL  Røang K 《Marine pollution bulletin》2007,54(2):145-148

The paper describes a model, which estimates the risk levels of individual crude oil tankers. The intended use of the model, which is ready for trial implementation at The Norwegian Coastal Administrations new Vard? VTS (Vessel Traffic Service) centre, is to facilitate the comparison of ships and to support a risk based decision on which ships to focus attention on. For a VTS operator, tasked with monitoring hundreds of ships, this is a valuable decision support tool. The model answers the question, "Which ships are likely to produce an oil spill accident, and how much is it likely to spill?".  相似文献   

Prevention of oil spill from shipping by modelling of dynamic risk   总被引：1，自引：0，他引：1  

Eide MS  Endresen O  Breivik O  Brude OW  Ellingsen IH  Røang K  Hauge J  Brett PO 《Marine pollution bulletin》2007,54(10):1619-1633

This paper presents a new dynamic environmental risk model, with intended use within a new, dynamical approach for risk based ship traffic prioritisation. The philosophy behind this newly developed approach is that shipping risk can be reduced by directing efforts towards ships and areas that have been identified as high priority (high risk), prior to a potential accident. The risk model proposed in this paper separates itself from previous models by drawing on available information on dynamic factors and by focusing on the ship's surroundings. The model estimates the environmental risk of drift grounding accidents for oil tankers in real time and in forecast mode, combining the probability of grounding with oil spill impact on the coastline. Results show that the inherent dynamic risk introduced by an oil tanker sailing along the North Norwegian coast depends, not surprisingly, significantly upon wind and ocean currents, as well as tug position and cargo oil type. Results of this study indicate that the risk model is well suited for real time risk assessment, and effectively separates low risk and high risk situations. The model is well suited as a tool to prioritise oil tankers and coastal segments. This enables dynamic risk based positioning of tugs, using both real-time and projected risk, for effective support in case of a drifting ship situation.  相似文献   

Analyzing shallow faulting at a site in the Wasatch fault zone, Utah, USA, by integrating seismic, gravity, magnetic, and trench data     

Alvin K. Benson  Nathan Brett Mustoe 《Engineering Geology》1995,40(3-4):139-156

Gravity, magnetic, and seismic surveys were conducted across the Wasatch fault zone east of Springville, Utah, near the mouth of Hobble Creek Canyon. The geophysical data were acquired, processed, and interpreted to determine possible locations of larger [total offset greater than 6 ft (1.8 m)], shallow normal faults within the fault zone. Interpretations of the individual data sets were integrated to help eliminate spurious readings and to strengthen the interpretations. Visual methods of integration, along with computer modeling, were chosen for this study. Furthermore, the geophysical data were correlated and integrated with available trench data and surface data. In addition to verifying locations of known faults, the geophysical surveys detected numerous possible additional faults not previously mapped. Of particular interest is a newly discovered graben structure near the southern end of the site, where building of new homes has recently been proposed.

New structural information about fault densities and styles was also determined from the surveys. The fault concentration for this site is 1.3 faults/100 ft (30.5 m), or one fault per 77 ft (23.5 m). Interpreted antithetic faults at the Hobble Creek site account for 65% of the total, while synthetic faults account for 35% with respect to the main fault strand.

Information derived from this study should be useful during planning and development of areas within the Wasatch fault zone. The characteristics of subsurface deformation can be used to gain a better understanding of the potential for surface rupture at a given site. This is also useful in planning appropriate site development and remedial measures to help mitigate hazards associated with large-magnitude earthquakes.  相似文献   

Thicknesses of some lunar mare basalt flows and ejecta blankets based on chemical kinetic data     

Robin Brett 《Geochimica et cosmochimica acta》1975,39(8):1135-1141

Data on the kinetics of some chemical reactions occurring in lunar samples are used to estimate cooling rates over limited temperature ranges. These results, together with data on thermal conductivity and specific heats of lunar samples, have been applied to estimate the thicknesses of the cooling units.Estimates for mare basalts indicate that they were derived from cooling units no thicker than 10 m. Breccias are derived from cooling units up to a few meters in thickness. This suggests that most lunar breccias are the product of a series of relatively local events rather than large basin-forming events. If this conclusion is correct, the significance of the radiometric ages of lunar breccias needs to be re-evaluated, as does the assignment of breccias to individual basin-forming events on the basis of their trace element contents. If the breccias are a product of the major basin-forming events, it is unlikely that so many would show an age of about 4.0 b.y. It is likely that a large proportion of materials sampled would have escaped resetting by these major events, and a wider spread of ages would be observed. Attempts to link a given breccia to a specific basin-forming event on the basis of its crystallization age therefore appear to be unfounded.  相似文献   

A lunar rock of deep crustal origin: sample 76535     

R Gooley  Robin Brett  Jeff Warner  J.R Smyth 《Geochimica et cosmochimica acta》1974,38(9):1329-1339

Lunar sample 76535 is a coarse-grained troctolitic granulite exhibiting a texture indicative of long annealing times. It is composed of homogeneous crystals of plagioclase (58 per cent, An₉₆), olivine (37 per cent, Fo₈₈) and bronzite (4 per cent, En₈₆).Chromian spinel-bronzite-diopside (Wo₄₆En₅₀Fs₄) symplectic intergrowths commonly occur along olivine-plagioclase boundaries and as tiny inclusions within olivine grains. These symplectites apparently formed by a reaction of the type: . The reaction is related to the experimentally determined reaction of Kushiro and Yoder (1966). The enstatite content of the diopside coexisting with the bronzite indicates equilibration at about 1000°C. Thermodynamic calculations for 1000°C indicate that the symplectites formed at a minimum pressure of about 0.6 kb. Low alumina contents of the pyroxenes indicate equilibration near this minimum pressure.Clusters of the same assemblage found in the symplectic intergrowths, but containing accessory metal, troilite, Ca-phosphates, baddeleyite, plagioclase and/or K-feldspar occur sporadically throughout the rock. These apparent late stage products crystallized in the low temperature-high pressure region discussed above.Phase relations of co-existing metal phases indicate that the rock cooled at a few tens of degrees/my, corresponding to depths of 10–20 km below the lunar surface, in agreement with the above pressure estimate.We infer that 76535 represents an original cumulate deposited at a depth between about 10 and 30 km. The last liquid crystallized in the relatively high pressure-low temperature field opx + cpx + Al-Mg-chromite. Cooling was extremely slow and accompanied by extensive chemical and textural re-equilibration. Reaction to form the symplectites occurred during the late stages of re-equilibration.  相似文献