Showing papers on "Tailings published in 1998"

Quantitative arsenic speciation in mine tailings using X-ray absorption spectroscopy

Abstract: X-ray absorption fine structure spectroscopy (XAFS) was used to determine arsenic (As) oxidation state, local coordination (to a radius of nearly equal Aa around As), and the relative proportion of different As species in model compounds and three California mine wastes: fully oxidized tailings (Ruth Mine), partially oxidized tailings (Argonaut Mine), and roasted sulfide ore (Spenceville Mine). Mineralogy was characterized by Rietveld refinement of X-ray powder diffraction patterns. The spatial distribution of As in the mine wastes (at several micrometers spatial resolution) was determined by electron microprobe analyses. X-ray absorption near edge structure (XANES) analysis indicates that As (super 5+) is the dominant oxidation state in the mine samples, but mixed oxidation states (nominally As 0 and AS (super 5+) ) were observed in the Argonaut Mine waste. Non-linear, least-squares fits of mine waste EXAFS (Extended XAFS) spectra indicate variable As speciation in each of the three mine wastes: As (super 5+) in the Ruth Mine sample is sorbed on ferric oxyhydroxides and aluminosilicates (probably clay) in roughly equal portions. Tailings from the Argonaut Mine contain nearly equal 20% As bound in arsenopyrite (FeAsS) and arsenical pyrite (FeS (sub 2-x) Asx) and nearly equal 80% As (super 5+) in a precipitate such as scorodite (FeAsO 4 .2H 2 O); however, no precipitate was detected by X-ray diffraction or microprobe analysis, suggesting that the phase is poorly crystalline or has low abundance (total As in sample = 262 ppm). Roasted sulfide ore of the Spenceville Mine contains As (super 5+) substituted for sulfate in jarosite [KFe 3 (SO 4 ) 2 (OH) 6 ] or incorporated in the structure of an unidentified Ca- or K-bearing phase, and As (super 5+) sorbed to the surfaces of hematite or ferric oxyhydroxide grains. Determination of solid-phase As speciation in mine wastes by XAFS spectroscopy is a valuable first step in the evaluation of its bioavailability, because the mobility and toxicity of As compounds vary with oxidation state. As bound in precipitates, as in the Argonaut mine sample, is considered to be less available for uptake by organisms than when sorbed on mineral surfaces or coprecipitated with poorly crystalline phases, as found for the Ruth and Spenceville mine wastes.

A predictive model for the water retention curve : application to tailings from hard-rock mines

Abstract: It is now commonly recognized that many geotechnical problems are related to the unsaturated behavior of soils. Such is the case for phenomena occurring at shallow depths in the so-called vadose zo...

Arcellaceans as pollution indicators in mine tailing contaminated lakes near Cobalt, Ontario, Canada

Abstract: Six assemblages resulting from Q-mode cluster analysis of 27 arcellacean taxa in thirty-nine sediment-water interface samples collected from two small lakes heavily polluted by mine tailings near the town of Cobalt, northeastern Ontario, Canada, correlated well with various distinct polluted and remediated environments. Results of R-mode cluster analysis indicated that arcellacean strains within the same species often discriminate between environments, thus utilization of infraspecific categories increases resolution when studying lake microenvironments, pollutants, and rates of lake remediation. Results of this study suggest that successful lake remediation in these and similarly polluted lakes is best achieved by leaving the tailings undisturbed to be buried naturally, or to speed the process by addition of an allochthonous sediment cap. INTRODUCTION Arcellaceans (thecamoebians) are freshwater protozoans that form agglutinated tests. They occur abundantly in Holocene lacustrine sediments (Medioli and Scott 1983; Scott and Medioli 1983) and have been successfully used to reconstruct Pleistocene-Holocene lacustrine paleoenvironments (Patterson et al. 1985; McCarthy et al. 1995). Most previous investigations have been of a reconnaissance nature and primarily concerned with the determination of occurrences, and ranges in different environments (Patterson et al. 1996). However, recent research of lakes in Canada and Italy has demonstrated the use of arcellaceans as an excellent indicator of pollution levels (Collins et al. 1990; Asioli et al. 1996; Patterson et al. 1996). For example, Patterson et al. (1996) have demonstrated the relationship between the distribution of arcellacean faunal assemblages and heavy metal pollutants (arsenic and mercury) in tailings in northeastern Ontario lakes. In addition, Asioli et al. (1996) have also conducted similar studies in Italy on acidic lakes polluted with copper and ammonium sulphates. These studies indicate that different arcellacean species appear to be influenced by the metal pollutants from mine tailings and they may indicate certain environmental parameters. Although ecological stresses on various arcellacean species have not been investigated thoroughly, some have been shown under laboratory conditions to vary in their gross morphology (strain) when under environmental duress (Medioli et al. 1987). Asioli et al. (1996) confirmed these laboratory results in the field when they recognized distinct morphotypic variations within three species of arcellaceans to characterize distinct paleoenvironments. As a result of these studies, the importance of investigating the distribution of strains of different arcellacean species was realized. Cobalt, Ontario is a prime example of an area heavily contaminated by tailings and waste by-products of silver mining (Patterson et al. 1996). In 1911, when silver mining in Cobalt was at highest levels of production, annual silver production exceeded 850 metric tons per year which easily made Cobalt Camp, as it was then known, the world's largest producer of the metal (Murphy 1977). An unfortunate legacy of this exploration is the millions of tons of mine waste and tailings that were dumped into nearby lakes and streams which, in addition to being detrimental to the surrounding environment, pose a great residual health risk to the 10,000 current residents of the Cobalt area. Most problematic is the arsenic associated with the silver ore, which ended up in the tailings, and the mercury and cyanide used in the ore milling process (Dumaresq 1993). We have observed several distinctive strains within the arcellacean populations of Crosswise and Peterson lakes (text-figure 1). These strains have developed in response to different environmental stresses and stimuli, such as the presence of chemical pollutants in the substrate and low oxygen levels. These morphotypic, or infraspecific, names are not considered valid under the International Code of Zoological Nomenclature (ICZN) and thus we use them in an informal sense. To avoid confusion where possible we have derived our morphotypic names from published literature. In most cases, what we consider strains of the same species have been described at various times as separate species. The purpose of this research is to increase our understanding of arcellaceans as environmental and pollution indicators by correlating these morphotypes with the geochemical environment (affected by mine tailings), bathymetry, organic content, and bottom sediment type (Table 1).

Biotic Generation of Arsenic(III) in Metal(loid)-Contaminated Freshwater Lake Sediments

Abstract: Sediments of Coeur d'Alene Lake, ID, are heavily contaminated with mine tailings that contain high levels of arsenic, iron, lead, and other trace elements. Maximal abundance of redox-active elements such as As and Fe is generally found close to the sediment−water interface, whereas peak abundance of less redox-active elements such as Pb is found at >25 cm. The suggestion that As is mobile within reduced sediments led us to characterize the sediment microbiota with regard to organisms whose activities favor As mobilization. Most probable number (MPN) estimates reveal that the densities of cultivable sulfate-, iron-, and arsenate-reducing bacteria approach 106, 105, and 104 cells g-1 wet weight sediment, respectively. Because As is considered more mobile in environments that produce As(III), we measured aqueous As(III) generation within As(V)-amended sediment microcosms. In organic acid-stimulated microcosms, >50% of a 10mM As(V) amendment is transformed to As(III), compared to 30% and 5% in unstimulated mi...

Acid-forming capacity of lead-zinc mine tailings and its implications for mine rehabilitation

Abstract: Acid mine drainage problems were experienced in a Pb–Zn mine operation at Lechang, in the northern part of Guangdong Province, People's Republic of China. Geochemical and acid generation evaluations were made on fresh tailings including tailings fine, tailings sand and high sulphide tailings, and oxidised tailings with the aim of providing information on mine rehabilitation. All fresh tailings had a pH higher than 7 while the oxidised tailings had a pH of 4.9 (range 1.6 to 7.4). Only samples with pH 4 dS m⊃-1. Total S contents of all tailings samples were very high with the high sulphide fraction having a mean S content of 38%. All fresh tailings had a high acid neutralisation capacity (ANC) while half of the oxidised tailings had an ANC less than zero. The results from the acid–base account and the net acid generation test indicated that all fresh and oxidised tailings samples were acid-forming except for the sand fraction samples. All tailings samples contained high total concentrations of Cd, Cu, Fe, Pb and Zn but low concentrations of total nitrogen and phosphorus. The preliminary results demonstrated that the tailings were all acid-forming especially the high sulphide fraction which should be kept permanently unexposed under impermeable cap or water.

Liquefaction flowslides in Rocky Mountain coal mine waste dumps

Abstract: Over the past 25 years there have been a large number of long runout flowslides from Rocky Mountain coal mine waste dumps. The waste dumps are constructed as end-dumped fills with an angle of repos...

Phase Associations and Mobilization of Iron and Trace Elements in Coeur d'Alene Lake, Idaho

Abstract: Sediments of Coeur d'Alene Lake, ID, are heavily contaminated with mine tailings that contain high levels of iron, lead, zinc, arsenic, and other trace elements. These tailings originate from the Silver Valley mining district drained by the South Fork of the Coeur d'Alene River. The possibilities that either lake eutrophication or the develop ment of a seasonally anoxic hypolimnion could mobilize trace elements from sediments into overlying waters led us to evaluate their phase associations. Analysis of ∼0.5 m gravity cores reveals these sediments to be highly reduced, and the trace elements therein predominantly associated with an operationally defined sulfidic phase. Vertical patterns of metal distribution suggest that Fe, Mn, and As have mobilized toward the sediment−water interface; these patterns are consistent with diagenetic solubilization. This is not the case for Zn, Pb, and other trace elements whose maximum abundance is generally found in deeper sediments. We postulate that metal sulfide format...

A comparative mineralogical and geochemical study of sulfide mine tailings at two sites in New Mexico, USA

Abstract: A comparative study of sulfide mine tailings from two sites near Silver City in southwest New Mexico has shown the need for environmental monitoring in a geological context. The Cyprus-Pinos Altos and Cleveland deposits consist of Cu and Zn skarn mineralization in the Pinos Altos Mountains of New Mexico. Primary ore minerals in both deposits include chalcopyrite, sphalerite, and galena. The Cyprus-Pinos Altos Mine ceased operation in 1995 and the Cleveland Mill closed in 1950. The deposits have similar mineralogical characteristics; however, the tailings are different in terms of age, degree of oxidation and method of disposal. The Cyprus-Pinos Altos tailings (CPAT) are stored in a lined, bermed impoundment. They are dominantly water-saturated and exhibit no secondary-phase formation. The grains are not cemented and show no evidence of primary-mineral dissolution. The geochemical data show a predominantly primary signature. The tailings pond water is neutral to slightly alkaline (pH from 7 to 8.3), partly as a result of processing methods. The Cleveland mill tailings (CMT) were deposited in a valley at the headwaters of an ephemeral stream. They are highly oxidized and differentially cemented. They have undergone numerous wet/dry cycles resulting in extensive oxidation. Secondary minerals predominate, and consist mainly of jarosite, goethite, hematite, and Fe-oxyhydroxides and -oxyhydroxysulfates. The pH of the stream draining the CMT is as high as 2.15. Maximum metal contents in the stream immediately downstream from the tailings are 5305 ppm Zn, 454 ppm Cu, 1.16 ppm Pb, 17.5 ppm Cd, 1.4 ppm As, and 0.01 ppm Hg.

Mobilization and attenuation of heavy metals within a nickel mine tailings impoundment near Sudbury, Ontario, Canada

Abstract: The oxidation and the subsequent dissolution of sulfide minerals within the Copper Cliff tailings area have led to the release of heavy metals such as Fe, Ni, and Co to the tailings pore water. Dissolved concentrations in excess of 10 g/l Fe and 2.2 g/l Ni have been detected within the shallow pore water of the tailings, with increasing depth these concentrations decrease to or near analytical detection limits. Geochemical modelling of the pore-water chemistry suggests that pH-buffering reactions are occurring within the shallow oxidized zones, and that secondary phases are precipitating at or near the underlying hardpan and transition zones. Mineralogical study of the tailings confirmed the presence of goethite, jarosite, gypsum, native sulfur, and a vermiculite-type clay mineral. Goethite, jarosite, and native sulfur form alteration rims and pseudo-morphs of the sulfide minerals. Interstitial cements, composed of goethite, jarosite, and gypsum, locally bind the tailings particles, forming hardpan layers. Microprobe analyses of the goethite indicate that it contains up to 0.6 weight % Ni, suggesting that the goethite is a repository for Ni. Other sinks detected for heavy metals include jarosite and a vemiculite-type clay mineral which locally contains up to 1.6 weight % Ni. To estimate the mass and distribution of heavy metals associated with the secondary phases within the shallow tailings, a series of chemical extractions was completed. The experimental design permitted four fractions of the tailings to be evaluated independently. These four fractions consisted of a water-soluble, an acid-leachable, and a reducible fraction, as well as the whole-rock total. Twenty-five percent of the total mass of heavy metals was removed in the acid-leaching experiments, and 100% of the same components were removed in the reduction experiments. The data suggest that precipitation/coprecipitation reactions are providing an effective sink for most of the heavy metals released by sulfide mineral oxidation. In light of these results, potential decommissioning strategies should be evaluated with the recognition that changing the geochemical conditions may alter the stability of the secondary phases within the shallow tailings.

Alluvial fans formed by channelized fluvial and sheet flow. II: application

Abstract: The formulation of the companion paper describing the evolution of mean elevation in a radially symmetric alluvial fan is applied to the specific case of the tailings basin of an iron mine. The tailings basin provides a simple field-scale example of a fluvial fan-delta system. Calculation procedures are developed to determine the effect of changing water and sediment discharge on fan evolution. The analysis is used to evaluate options for the extension of the lifetime of the tailings basin.

The impact of unconfined mine tailings and anthropogenic pollution on a semi-arid environment – an initial study of the Rodalquilar mining district, south east Spain

Abstract: A geochemical study of stream sediments near Rodalquilar (South-east Spain) was undertaken to investigate the impact of processing activities associated with nearby gold mining. Despite the semi-arid nature of the area, visual inspection of tailings indicates that considerable fluvial erosion occurs during rainfall events. Geochemical analysis demonstrates that Mo, Sb, Te, Bi and As are all found at elevated levels in stream sediments downstream of the tailings site. Elevated levels of Pb, Cu and Zn were also noted in stream sediments. Statistical analysis demonstrates that four factors control trace-element distribution. Factor 1 displays a strong association of Mo, Sb, Te and Bi and As and is attributed to the mine tailings. Factor 2 displays an association of Pb and Cu, and is most easily attributed to anthropogenic pollution. Factor 3 distinguishes Au and reflects the selective nature of ore-processing methods employed at the site. Factor 4 only highlights Zn, reflecting that it is derived from several, probably unrelated, sources.

Mineralogical study of base metal tailings with various sulfide contents, oxidized in laboratory columns and field lysimeters

Abstract: Oxidation of a flotation-derived, low-sulfide tailings containing approximately 0.4 wt.% S was compared with simultaneously oxidized tailings containing 1.0 wt.% S and 2.5 wt.% S to assess their acid generating characteristics. Each tailings type was exposed to oxidation for three years in laboratory columns and in lysimeter pits in the field. In these tailings the sulfide mineral of principal concern with respect to acid generation is pyrrhotite (Fe 1-x S). In past studies the alteration of pyrrhotite has been characterized by initial replacement with marcasite (FeS2) and ferric iron sulfates, which are followed by development of ferric oxyhydroxides such as goethite and lepidocrocite. Macroscopic characterization of the tailings shows varying and progressive degrees of oxidation correlative with the three different sulfur contents. As expected, the tailings with the lowest sulfur content are the least oxidized, and those with the highest sulfur content have reacted the most. The column tests, which represent accelerated reaction conditions relative to those for the lysimeter pits, show much higher degrees of oxidation, and a markedly more distinct boundary between the oxidized and unoxidized zones; as well, differences among the three tailings types are more pronounced.

The Environmental Impact of Gold Mines in the Yugu-Kwangcheon Au-Ag Metallogenic Province, Republic of Korea

Abstract: An investigation was made of the degree and extent of heavy metals in tailings, stream waters, sediments, soils and crop plants in the Yugu-Kwangcheon Au-Ag Province, comprising the Gubong, Daebong...

Marine tailings disposal simulation

Abstract: The disposal of mine tailings in deep water body requires comprehensive assessment of the potential environmental impacts, and estimates of the effective storage capacity of the bottom bathymetry for accommodating the anticipated volume of disposed tailings over the life of a mine. A mathematical simulation model was developed for this purpose to predict the distribution and long-term deposition patterns of tailings in a fjord. The model describes the mechanics of the tailings slurry flow along the bottom of the receiving water body and the settling of suspended particles, as well as the redistribution of the deposited sediments due to slumping of unstable slopes. Specific processes simulated in the model also include entrainment at the top of the density current, entrainment associated with internal hydraulic jumps in areas of changing bottom slopes, hindered settling and coagulation of suspended particles, and sediment deposition and bathymetric changes resulting from the deposition of large quantities of tailings. Long-term tailings deposition patterns are predicted by analyzing the flow of the tailings slurry in a series of time increments, from a few months to a year. The bathymetry is assumed to remain unchanged within each time increment, and the model first simulates the steady-state flow field for the tailings slurry along the bottom and the resulting deposition rates for several sizes of suspended particles. Then the estimated tailings deposition rates are combined with slope stability considerations to predict the new bathymetry of the receiving water body. Data from several operating marine tailings disposal systems were reviewed to assess the applicability of specific relationships used in the model. The model was calibrated using data from one of the most extensively studied marine tailings disposal systems, the Island Copper mine in Rupert Inlet of Vancouver Island, British Columbia. Comparison of simulated tailings deposition patterns in Rupert Inlet with data from field observations and measurements suggests that calibration of the model is satisfactory and provides confidence in the capability of the model to predict deposition patterns and suspended sediment concentrations for proposed mines.

In-Lake Neutralization of Acid Mine Lakes

Abstract: One of the problems caused by strip mining is the generation of acidic lakes. Typically, the huge holes left from strip mining of soft coal are partly filled by mine tailings containing pyrite and other sulphide minerals. The remaining holes are flooded by groundwater forming so-called mine lakes. When in contact with oxygen-rich water the iron-sulphide species of the mine tailings are oxidized to sulphuric acid and ferric iron (Singer and Stumm 1970; Nordstrom et al. 1979). This results in an extreme acidification of the lakes (van Berk 1987; Obermann et al. 1992; Wisotzky 1994).

Mercury partitioning within alluvial sediments of the Carson river valley, Nevada: Implications for sampling strategies in tropical environments

Abstract: The Carson River system of west-central Nevada was subjected to a massive influx of mercury-enriched tailings derived from mining and milling of the Comstock Lode near the end of the 1800s. Detailed investigations have shown that these contaminated tailings were deposited along the Carson River Valley during a period of channel and floodplain aggradation. Following cessation of mining, incision re-exposed the historical sediment in banks of the modern channel. Concentrations of mercury in these deposits are commonly two to three orders of magnitude above background levels observed in other sediments and soils of the region. Most of the mercury is carried on fine-grained particles as would be expected from previous studies of trace metal partitioning in alluvial deposits. However, erosion and reworking of the historical sediment during lateral channel migration leads to a loss of fine-grained particles and a concentration of mercury-gold/silver amalgam grains in the modern channel bed. As a result, mercury is distributed in both fine- and coarse-grained sediment fractions of the channel floor.