Time-Independent Gravitational Fields

This article reviews, from a global point of view, rigorous results on time independent spacetimes. Throughout attention is confined to isolated bodies at rest or in uniform rotation in an otherwise empty universe. The discussion starts from first principles and is, as much as possible, self-contained.Comment: 47 pages, LaTeX, uses Springer cl2emult styl

Exploitation of gold in an historic sewage sludge stockpile, Werribee, Australia: resource evaluation, chemical extraction and subsequent utilisation sludge

Sewage sludges are potential targets for economic extraction of Au because of the documented Au content of sewage sludges worldwide, which are of the order of some ore deposits currently mined for Au. The sewage of Melbourne, Australia, was stockpiled in large, closed, lagoonal tanks from 1898 until 1980. Reeves, Plimer and Foster, 1999, have conducted, and published, an extensive and exhaustive study of the Werribee sewage reserves utilising RNAA, INAA, GFAAS, ICPMS, and FLAAS to determine 31 elements, including Au, Ag, Sb, As, Cd, Hg, Zn, Cu, and Pb. The study was initiated to determine Au, Ag and other metal variations in both space and time and to investigate the economics of chemical extraction of the precious metals. A total of 149 samples from over 50 hand-auger drillholes to a depth up to 4m were analysed from the stockpiles, with Au assays yielding remarkably consistent results. Average grades of 0.77 g/t Au and 18.8 g/t Ag have been documented for a measured resource of 770,000 m3. Laboratory-based extractive metallurgy of the Werribee sludges has demonstrated that Au, Ag, and Zn can be removed with relative ease by heap-leaching using modified conventional technology, albeit with prohibitive reagent consumption. The extraction of the precious metals also results in the variable removal of contaminant metals such as Cd, As, Sb, Hg and Cr which may render the sludges fit for sale as agricultural fertiliser, provided organic pollutants and pathogenic organisms are below governmental environmental protection limits

Evaporative mineral precipitates from a historical smelting slag dump, Río Tinto, Spain

This work reports the chemistry and mineralogy of mineral efflorescences associated with slag deposits at the historical Río Tinto smelter site, southwest Spain. The slags have been subject to weathering since dumping in the 19 th and 20 th century, and a series of evaporative mineral efflorescences has been observed. The efflorescences commonly occur as powdery or cemented salt precipitates at seepage points at the base of the slag dump and as solid aggregates in protected overhangs facing the Tinto river. The mineral salt types include Ca and Mg sulfates (gypsum, epsomite, hexahydrite, bloedite) as well as mixed Fe2+ – Fe3+ hydrated sulfates (copiapite, roemerite). The salt mixtures have variable metal concentrations, including major (> 1 wt %) concentrations of Zn, minor Cu (> 1000 ppm), sub-minor (100–1000 ppm) to traces (< 100 ppm) of As and Co as well as traces (< 100 ppm) of Ag, Bi, Cd, Mo, Ni, Pb, Sb, Sn, Tl and W. Copiapite-rich samples exhibit the highest As, Cd and Cu, epsomite–hexahydrite rich samples have the highest Zn, and the gypsum-rich samples show the lowest metal and metalloid concentrations. Dissolution experiments show that all salt mixtures are acid generating due to Fe and Al hydrolysis and resultant pH decrease in the solution. Thus, weathering and leaching of metalliferous smelting slags are accompanied by the mobilisation of metals, metalloids, alkali earth elements and sulfate into pore and seepage waters. Evaporation of seepage waters emanating from the slag dump causes the precipitation of mobilised elements and compounds and leads to their temporary fixation in secondary soluble minerals. Dissolution of the efflorescences during the next rainfall and flushing event and associated Al3+ and Fe3+ hydrolysis contribute to the acidification and metal and sulfate contamination of Río Tinto waters

Mobilisation of metals and metalloids from historical smelting slag dumps, Rio Tinto, Spain

While the chemistry and mineralogy of sulfidic, AMD\ud producing wastes have been studied in great detail, few\ud studies have focused on smelting residues commonly present\ud at historic mine sites. This is despite the fact that historical base metal smelting slags contain elevated levels of heavy metals and metalloids and are subject to contemporaneous weathering processes thereby releasing elements to ground and surface waters. This work reports the chemistry and mineralogy of slag deposits (3 Mt) at the historic Rio Tinto smelter site, southwest Spain. \ud \ud The microcrystalline slags contain primary slag phases, relict flux, ore and furnace materials and secondary weathering related minerals. Common primary slag phases are glass, Zn-rich fayalite and Zn-rich hedenbergite/augite. The slag materials contain wt% concentrations of Zn, major (ie. 1000 - 10000 ppm) Cu and Pb, minor (ie. 100 - 1000 ppm) Co, Sb and Sn, and traces (ie. <100 ppm) of Ag, As, Bi, Cd, Mo, Ni, TI and W. The slags have been subject to weathering since dumping in the 19th and 20th century, and a series of mineral efflorescences has been observed. They most commonly occur as powdery or cemented salt precipitates at seepage points and as solid aggregates in protected overhangs facing the Rio Tinto river. Mineral salts include gypsum, epsomite and copiapite as well as a series of minor phases such as roemerite, bloedite and hexahydrite. The mineral mixtures contain variable metal concentrations, including major Cu and Zn, minor As and Co, and traces of Cd, Ni and Pb.\ud \ud Rio Tinto slags have high concentrations of metals and\ud metalloids in the order of Zn>Cu>Pb>Sb>Co>As>Ni. In contrast, the mineral salt mixtures have metal concentrations in the order of Zn>Cu>As>Co>Ni>Sb. Such distinctly different relative concentrations of elements in the two sample media collected from the weathered slag dumps can be related to the different mobility of elements in surface environments. For example, Sb displays a reduced mobility possibly due to the formation of insoluble precipitates, coprecipitation and adsorption in the slag dump. Thus, weathering of siliceous smelting slags is accompanied by the preferential mobilisation of some trace elements (ie. As, Co) into pore and seepage waters. Evaporation of the saline, metalliferous seepage waters emanating from the siliceous slag dumps causes the precipitation of secondary minerals. These minerals\ud temporarily store metals, metalloids and sulfate until\ud redissolution during the next rainfall. The Rio Tinto slag\ud dumps represent long-term sources of metals and metalloid\ud pollutants to local ground and surface waters

Leaching of sulfidic backfill at the Thalanga Copper-Lead-Zinc mine, Queensland, Australia

The placement of sulfidic waste below the groundwater table ensures limited interaction with the hydrosphere and suppression of sulfide oxidation. However, if sulfidic waste is placed above the groundwater table and remains uncovered, the backfill becomes part of the unsaturated zone and is exposed to atmospheric oxygen and leaching. This study aims to establish the leaching behaviour of sulfidic waste placed above the groundwater table and the impact of such leachate on the local aquifer at the Thalanga base metal mine. Mining of the Thalanga copper-lead-zinc deposit resulted in a large final mining void (600 m × 150 m × 70 m) and extensive underground workings. The underground workings were partly filled with tailings and the open pit was partly backfilled with acid producing sulfidic waste rock. In addition, the pit serves as a sink for acidic run-off from adjacent waste rock piles and mine workings. To date, the backfill of sulfidic waste rock placed into the pit has not been capped with benign materials and for most of the dry season, the surface of the backfill is covered by melanterite-type efflorescences. Results of kinetic column leach experiments conducted on the sulfidic waste indicate that Cd, Cu, Zn and SO4 rich waters migrate from the backfilled sulfidic waste into the local unconfined aquifer. However, the seepage of alkaline (pH 7.3 - 8.0), high conductivity (>10 000 µS/cm) tailings waters into the remaining pit void clearly shows that the acid leachate originating from the sulfidic waste rock does not impact beyond the waste repository and its immediate environment. Geochemical modelling implies that minimal or no mixing occurs between the acid waste rock leachate and the alkaline tailings waters

Tailings dam seepage at the rehabilitated Mary Kathleen uranium mine, Australia

This study reports on the seepage of metals, metalloids and radionuclides from the Mary Kathleen uranium mill tailings repository. Since rehabilitation in the 1980s, the capped tailings have developed a stratified hydrochemistry, with acid (pH 3.7), saline, metal-rich (Fe, Mn, Ni, U ± As, Pb, Zn), oxygenated (1.05 mg L^−1 DO), radioactive waters in the upper tailings pile and near-neutral pH (pH 7.57), metal-poor, reduced (0.08 mg L−1 DO) waters at depth. Seepage (~0.5 L s^−1) of acid (pH 5.5), metal-rich (Fe, Mn ± Ni, U, Zn), radioactive (U-235, U-238, Ra-226, Ra-228, Ac-227) waters occurs from the base of the tailings dam retaining wall into the former evaporation pond and local drainage system. Oxygenation of the seepage waters causes the precipitation of Fe and coprecipitation and adsorption of other metals (U, Y), metalloids (As), rare earth elements (Ce, La) and radionuclides (U-235, U-238). By contrast, alkalis and alkaline–earth elements (Ca, K, Mg, Na, Sr), Mn, sulfate and to some degree metals (U, Zn, Ni), rare earth elements (Ce, La) and radionuclides (U-235, U-238, Ra-226, Ra-228) remain in solution until pH neutralisation and evaporation lead to their precipitation in efflorescences and sulfate-rich evaporative sediments. While the release of contaminant loads from the waste repository through seepage is insignificant (~5 kg of U per year), surface waters downstream of the tailings impoundment possess TDS, U and SO4 concentrations that exceed Australian water quality guideline values in livestock drinking water. Thus, in areas with a semi-arid climate, even insignificant load releases of contaminants from capped tailings repositories can still cause the deterioration of water quality in ephemeral creek systems

High-Resolution pit water quality model for the Highway Reward Mine, Queensland, Australia

Field and laboratory data combined with computational modelling have been used to predict the pit water quality for the Highway Reward mine. Open pit mining of the Highway Reward copper-gold deposit has produced a final mining void with a diameter of 600 m and a depth of 280 m. This void will be left to fill with ground and surface water once pumping of pit water ceases. Several leaching tables were constructed to simulate weathering reactions and surface water run-off in the major pit wall units during a 200-day leaching experiment. To date, about three-quarters through the experiment, combined run-off from these cells has reached a pH <4, corresponding to actual present day pit water pH values and chemistries. While sulfide oxidation in the pitwalls leads to an acid, metal-rich leachate, bicarbonate-rich groundwater inflow during the dry season acts as a buffer. Acid generating salts appear to have only a small impact on the overall pit water chemistry. The kinetic test data have been combined with measured pit water chemistry data, measured surface and seasonal groundwater inflows, climatic data, and calculated pit lake surface area and volume to produce a high-resolution pit water quality model. This high-resolution pit water quality model will aid in the mine decommissioning process

Physical dispersion of radioactive mine waste at the rehabilitated Radium Hill uranium mine site, South Australia

The Radium Hill uranium deposit, in semi-arid eastern South Australia, was discovered in 1906 and mined for radium between 1906 and 1931 and for uranium between 1954 and 1961 (production of 969 300 t of davidite ore averaging 0.12% U3O8). Rehabilitation was limited to removal of mine facilities, sealing of underground workings and capping of selected waste repositories. In 2002, gamma-ray data and samples of tailings, uncrushed and crushed waste rock, stream sediment, topsoil and vegetation were collected to assist in examination of the current environmental status of the mine site. The data indicate that capping of tailings storage facilities did not ensure the long-term containment of the low-level radioactive wastes due to the erosion of sides of the impoundments. Moreover, wind erosion of waste fines (phyllosilicates, ore minerals) from various, physically unstable waste repositories has caused increasing radiochemical (from a background dose of 35-70 nSv/hr to max. 0.94 Sv/hr) and geochemical (Ce, Cr, La, Lu, Rb, Sc, Th, U, V, Y, Yb) impacts on local soils. Plants (saltbush, pepper tree) growing on waste dumps display evidence of biological uptake of lithophile elements, with values being up to 1-2 orders of magnitude above values for plants of the same species at background sites. However, radiation doses associated with the mine and processing site average 0.67 Sv/hr; hence, visitors to the Radium Hill site will not be exposed to excessive radiation levels. Although rehabilitation procedures have been partly successful in reducing dispersion of U and related elements into the surrounding environment, it is apparent that 20 years after rehabilitation, there is significant physical and limited chemical mobility, including transfer into plants. Additional capping and landform design of the crushed waste and tailings repositories are required in order to minimise erosion and impacts on surrounding soils and sediments