Showing papers on "Tailings published in 1981"

Geochemical investigations on fluvial sediments contaminated by tin-mine tailings, Cornwall, England

Abstract: Tin-mine tailings containing high concentrations of Sn, Cu, Zn, Fe, Mn, As, and W are discharged into the Red River of cornwall, England and are then transported into St. Ives Bay under normal flow conditions. Most of the tin-bearing particles in the fluvial sediments are smaller than 170 μm, but tin-bearing composite grains or mineral grains with tin interspersed in the crystal lattices also occur in coarser size fractions. Tin distribution in the sediments is controlledby: (1) the distance from the source of the tailings, and (2) the concentration processes operating on the river bed. Suspended sediment and sediment transported by saltation filtered from river water samples also showed high concentrations of metals although, in contrast to the bottom sediments, they vary within a narrow range. Distributions of Cu, Zn, Fe, As, and Pb in the filtered sediments probably are related to the physical and chemical behavior of their sulphide minerals during fluvial transportation. A regional stream-sediment geochemical reconnaissance survey for tin did not show the highest concentration in the Red River; this indicated that in other rivers and streams tin reconcentration by selective removal of light minerals had taken place in the bottom sediments after mining operations had ceased. These rivers and streams also can transport large quantitiies of land-derived sediment including tin-mine tailings discharged into them when mines were operating. The minimum distance of tin transported by the Red River is at least 10 km; however, most of the tin was derived from mine tailings and is considered to be unnatural.

Distribution of heavy metals and radionuclides in sediments, water, and fish in an area of Great Bear Lake contaminated with mine wastes.

Abstract: The concentrations of heavy metals and radionuclides in the sediments and water of Great Bear Lake were determined during 1978 near an operating silver mine and an abandoned uranium mine. Additional information on the level of mercury in fish tissues were also collected. The mines, situated on the same site, deposited tailings and other waste material directly into the lake. The concentrations of mercury, lead, manganese, and nickel in the sediments were highest near the tailings deposit and decreased significantly as the distance from the mine increased. Although there were also significant positive correlations between these metals and the organic content of the sediments, water depth and slope of the bottom had no impact on metal distribution. Since the concentrations of arsenic, cobalt, copper, 226radium, 210lead and 230thorium varied inconsistently throughout the study area, the distribution of these substances could not be related to any of the environmental factors that were measured. There were, however, significant negative correlations between the concentrations of 232thorium and 228thorium and distance from the mine and organic content of the sediments. Heavy metal and radionuclide levels in water were generally below detectable limits, reflecting the strong chemical bonding characteristics of the sediments. The low concentrations of mercury in the tissues of lake trout Salvelinus namaycush were probably related to low uptake rates and the ability of this species to move into uncontaminated areas of the lake.

Tailings from a lead mine and lead levels in schoolchildren: a preliminary report

Abstract: Whole blood lead levels, free erythrocyte protoporphyrin (FEP) concentrations, and hair lead levels were measured in 181 schoolchildren resident in and around the town of Northampton, Western Australia, where tailings from a lead mine have been used extensively for ground surfacing and other purposes. Mean blood lead levels were 0.68 μmol/L (14.0 μg/100 mL) in boys and 0.5 μmol/L (10.4 μg/100 mL) in girls, the highest being 2.27 μmol/L (47 μg/100 mL). Nine children (5%) had blood lead levels above 1.21 μmol/L (25 μg/100 mL) and four had levels above 1.45 μmol/L (30 μg/100 mL). Four of these children had FEP levels above 2.0 μmol/L. There was a statistically significant difference between the mean blood lead levels of children resident in the town (mean blood lead level, 0.63 μmol/L (13.1 μg/100 mL)) compared with those resident out of the town 0.55 μmol/L (11.3 μg/100 mL). The presence of lead tailings in the town may account for the small difference.

Environmental impacts of iron ore tailings - the case of tolo harbour, hong kong

Abstract: Disposal of iron ore tailings along the shore of Tolo Harbour, Hong Kong has altered the adjacent environment. Due to the ever-expanding population, the vast development of various industries, and the lack of sanitary control, the existing pollution problem of Tolo Harbour is serious. The iron ore tailings consist of a moderate amount of various heavy metals, e.g., copper, iron, manganese, lead, zinc, and a lower level of macronutrients. A few living organisms have been found colonizing this manmade habitat. Higher metal contents were also found in the tissue ofPaphia sp. (clam);Scopimera intermedia (crab);Chaetomorpha brychagona (green alga);Enteromorpha crinita (green alga); andNeyraudia reynaudiana (grass). The area can be reclaimed by surface amelioration using inert materials, soils, or organic substrates, and by direct seeding, using nontolerant and tolerant plant materials. Reclamation of the tailings would improve the amenity of the adjacent environment and also mitigate pollution escaping to the sea.

The use of legumes for reclaiming copper mine wastes in the Southwestern USA

Abstract: Seeds of three legumes, blue lupine (Lupinus hirsutus L.), sesbania (Sesbania macrocarpa Muhl.), and alfalfa (Medicago sativa L.) were broadcast planted on four soil materials (desert soil, overburden, overburden plus tailings, and tailings) associated with copper mines near Tucson, Arizona. Experiments were conducted to study the effects of the four soil materials on germination (emergence), seedling establishment, and growth over a two-year period (1974 and 1975). All species grew best on desert soil, followed by overburden, overburden plus tailings, and tailings, in decreasing order. The presence of copper in overburden plus tailings and in tailings may have created a toxicity effect that limited the growth of plants in these two soil materials. Alfalfa was superior on all soil materials. Sesbania and blue lupine grew equally well. All three species were able to adapt to the different soil materials. For revegetation on copper mine wastes, it is desirable to plant a variety of plant species rather than a single species, to help blend the disturbed areas into the surrounding environment

Preparation concentrated TiO2 slurries from spent steam

Abstract: A process for preparing concentrated slurries of TiO 2 and water with a solids content of 30-70% by weight from TiO 2 micronizer tailings that are carried in steam separated from TiO 2 and steam from a micronizer by scrubbing the steam and TiO 2 micronizer tailings with a slurry of TiO 2 and water, separating TiO 2 and water from the steam and circulating a portion of the TiO 2 and water to the absorber until the solids content desired is reached.

Process for recovery of residual bitumen from tailings from oil sand extraction plants

Abstract: IMPROVED PROCESS FOR RECOVERY OF RESIDUAL BITUMEN FROM TAILINGS FROM OIL SAND EXTRACTION PLANTS Abstract of the Disclosure Bitumen in primary separation vessel underflow and bitumen plus diluent naphtha in aqueous effluent from centrifugation plants that together represent losses of 8 to 12% of oil in oil sand feed to a hot water extration plant may be substantially recovered by settling and flotation scavenging after tailings fractions have been subjected to a tumbling, mixing or shearing process. The process of the present invention includes the possibility of dilution of the sand while raising the bitumen content of the primary separation vessel under-flow by admixture with centrifugation plant tailings, unscavenged primary separation vessel middlings or bituminous sludge from a retention pond, subjecting the resulting mixture to a tumbling, mixing or shearing action with incorporation of air or alternative gas bubbles followed by settling of the sand with passive or gas induced flotation scavenging of bitumen which can be promoted by use of carbon dioxide. By providing a back-up recovery system capable of efficient scavenging of residual hydrocarbon the hot water process can be operated at increased throughput, lower temperatures, reduced sensitiv-ity to clay-water ratios and increased extraction efficiencies.

Attenuation of Radionuclides and Toxic Elements by In Situ Soils at a Uranium Tailings Pond in Central Wyoming

Abstract: Existing concentrations of radionuclides and arsenic in a uranium tailings pond and groundwater, and hydrogeologic and mass transport parameters were utilized in a Galerkin-based finite element mass transport model to predict future migration potential for discrete chemical species. Field and laboratory data and the results of computer modeling indicate that movement of chemical species of interest at the subject site is mitigated by chemical reaction with in situ soils including precipitation, coprecipitation, and ion exchange. The study showed that among the hydrogeologic and mass transport parameters, distribution coefficients are the major controlling factor in determining the extent of attenuation of radionuclides and arsenic. 9 refs.

Reducing the environmental impact of coal-washing practice in Australia

Abstract: All Australian coal for export is washed — that is, the low-grade high-ash material is separated out and disposed of at the washery site. The coarse rejects are generally placed in embankments and the tailings are pumped into settling ponds. These methods of waste disposal can create environmental problems. In addition, they represent a significant energy loss, because about one-third of the waste material is combustible and is thus a potentially valuable source of energy. Laboratory studies at the CSIRO Division of Fossil Fuels at North Ryde, New South Wales, have shown that energy can be successfully recovered from washery wastes by the process of fluidized-bed combustion. A pilot fluidized-bed combustor, with a capacity of 2 tonnes/hour, is undergoing prolonged trial at the Clutha washery near Camden, New South Wales, in a joint project between the Joint Coal Board and CSIRO. The results from the pilot plant tests have provided the basis for a conceptual design and feasibility study for a full-scale tailings treatment plant. This study has indicated that fluidized-bed combustion:

Stabilization and disposal of coal preparation plant tailings

Abstract: It was generally felt by the tip operatives that the troublesome material involved in the waste disposal was the filter cake. Filter cake is an apparently solid material which in actual fact carries a moisture content near the liquid limit - the percentage moisture at which the tailings liquify. Its apparent solidity is illusory, being due to the effect of capillary action of the contained water. This exerts a strong compressive stress on the soil skeleton and holds it together. If such material is brought into contact with free water, which is always present in the coarse discard, the capillary forces are nullified and it immediately begins to revert to liquid. This process is rapid in the case of drum tailings and slower for press tailings, as the former has a greater surface area weight for weight. This is important, since the behavior of a mixture of filter cake and coarse washery discard tends to be governed by the characteristics of the filter cake. One possible method found for stabilizing the tailings was the addition of cement, combined with adequate mixing. Accordingly, some small-scale experiments on the cone tailings were carried out. These demonstrated that the addition of 5% bymore » weight of cement to the wet tailings produced a material that became semi-hard in 24 hours. Exhibiting no free moisture, the material had an unconfined compressive strength of 34.5 kilonewtons per square meter (5 pounds per square inch). On the basis of these experiments, a pilot plant was constructed at Oakdale which would treat the cone material and at least part of the dredged material. The results were satisfactory at a very reasonable cost. (LTN)« less

Method of reducing the sludge content of a tailings pond

Abstract: METHOD OF REDUCING THE SLUDGE CONTENT OF A TAILINGS POND A hot water process for processing bituminous tar sands which includes the steps of: A) forming a pulp of the bituminous tar sands and water in a conditioning drum; B) passing the pulp across screen means and discarding oversize rejected thereby; C) diluting the screened pulp; D) settling the diluted pulp in a separation zone to form an upper primary bitumen froth zone, a middlings layer comprising water and mineral, and a sand tailings layer; and E) separately withdrawing the primary bitumen froth layer and the sand tailings layer; the improvement which comprises introducing a clay-containing slurry into the conditioning drum such that the pores of clay lumps contained therein become filled to render the lumps resistant to dispersal whereby they are rejected by the screen means and discarded as oversize.

Moisture content analysis of covered uranium mill tailings

Abstract: The use of vegetation and rock covers to stabilize uranium mill tailings cover systems is being investigated by Pacific Northwest Laboratory. A modeling study of moisture movement through the tailings and cover layers was initiated to determine the effect of the stabilizing techniques. The cover system was simulated under climatic conditions occurring at Grand Junction, Colorado. The cover consisted of a layer of wet clay/gravel mix followed by a capillary barrier of washed rock and a surface layer of fill soil. Vegetation and rock were used to stabilize the surface layer. The simulation yielded moisture content and moisture storage values for the tailings and cover system along with information about moisture losses due to evaporation, transpiration, and drainage. The study demonstrates that different surface stabilization treatments lead to different degrees of moisture retention in the covered tailings pile. The evapotranspiration from vegetation can result in a relatively stable moisture content. Rock covers, however, may cause drainage to occur because they reduce evaporation and lead to a subsequent increase in moisture content. It is important to consider these effects when designing a surface stabilization treatment. Drainage may contribute to a groundwater pollution problem. A surface treatment that allows the cover systemmore » to dry out can increase the risk of atmospheric contamination through elevated radon emission rates.« less

Evaluation of liners for a uranium-mill tailings disposal site: a status report

Abstract: The United States Department of Energy is conducting a program designed to reclaim or stabilize inactive uranium-mill tailings sites. This report presents the status of the Liner Evaluation Program. The purpose of the study was to identify eight prospective lining materials or composites for laboratory testing. The evaluation was performed by 1) reviewing proposed regulatory requirements to define the material performance criteria; 2) reviewing published literature and communicating with industrial and government experts experienced with lining materials and techniques; and 3) characterizing the tailings at three of the sites for calcium concentration, a selection of anions, radionuclides, organic solvents, and acidity levels. The eight materials selected for laboratory testing are: natural soil amended with sodium-saturated montmorillonite (Volclay); locally available clay in conjunction with an asphalt emulsion radon suppression cover; locally available clay in conjunction with a multibarrier radon suppression cover; rubberized asphalt membrane; hydraulic asphalt concrete; chlorosulfonated polyethylene (hypalon) or high-density polyethylene; bentonite, sand and gravel mixture; and catalytic airblown asphalt membrane. The materials will be exposed in test units now being constructed to conditions such as wet/dry cycles, temperature cycles, oxidative environments, ion-exchange elements, etc. The results of the tests will identify the best material for field study. Themore » status report also presents the information gathered during the field studies at Grand Junction, Colorado. Two liners, a bentonite, sand and gravel mixture, and a catalytic airblown asphalt membrane, were installed in a prepared trench and covered with tailings. The liners were instrumented and are being monitored for migration of moisture, radionuclides, and hazardous chemicals. The two liner materials will also be subjected to accelerated laboratory tests for a comparative assessment.« less

Application of controlled release technology to uranium mill tailings stabilization

Abstract: A trifluralin (herbicide) releasing device was developed with a theoretical effective lifetime in excess of 100 years. When placed in a layer in soil, the PCD system will prevent root penetration through that layer without harming the overlying vegetation. Equilibrium concentrations of trifluralin in soil can be adjusted (along with the theoretical life of the device) to suit specific needs. The present system was designed specifically to protect the asphalt layer or clay/aggregate barriers on uranium mill tailings piles; PCD devices composed of pellets could also be implanted over burial sites for radioactive and/or toxic materials, preventing translocation of those materials to plant shoots, and thence into the biosphere.