Mine Waste Piles Research Articles

English

Abstract. Two trenches were dug into the south Dinero mine-waste pile near Leadville, Colorado, to study the weathering of rock fragments and the mineralogic sources of metal contaminants in the surrounding wetland and Lake Fork Watershed. Water seeping from the base of the south Dinero waste-rock pile was pH 2.9, whereas leachate from a composite sample of the rock waste was pH 3.3. The waste pile was mostly devoid of vegetation, open to infiltration of precipitation, and saturated at the base because of placement in the wetland. The south mine-waste pile is composed of poorly sorted material, ranging from boulder-size to fine-grained rock fragments. The trenches showed both matrix-supported and clast-supported zones, with faint horizontal color banding, suggesting zonation of Fe oxides. Secondary minerals such as jarosite and gypsum occurred throughout the depth of the trenches. Infiltration of water and transport of dissolved material through the pile is evidenced by optically continuous secondary mineral deposits that fill or line voids. Iron-sulfate material exhibits microlaminations with shrinkage cracking and preferential dissolution of microlayers that evidence drying and wetting events. In addition to fluids, submicron-sized to very fine-grained particles such as jarosite are transported through channel ways in the pile. Rock fragments are coated with a mixture of clay, jarosite, and manganese oxides. Dissolution of minerals is a primary source of metals. Skeletal remnants of grains, outlined by Fe-oxide minerals, are common. Potassium jarosite is the most abundant jarosite phase, but Pb- and Ag-bearing jarosite are common. Grain-sized clusters of jarosite suggest that entire sulfide grains were replaced by very fine-grained jarosite crystals. The waste piles were removed from the wetland and reclaimed upslope in 2003. This was an opportunity to test methods to identify sources of acid and metals and metal transport processes within a waste pile. A series of entrapment ponds, lined with limestone rip rap, was created where the mine waste was once situated. A flooded adit discharges low-pH metal-bearing waters into the ponds. A white (Zn, Mn)-sulfate precipitate was observed in 2003 around the edges of the most distal pond. Key Words: mine waste, dissolution, jarosite, anglesite, microlamination, leachate -----------------------------------------

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In a joint project, the mine waste-piles at the Rattler Mine near Idaho Springs, Colorado, were sampled and analyzed by scientists from the U.S. Geological Survey (USGS) and the Colorado School of Mines (CSM). Separate sample collection, sample leaching, and leachate analyses were performed by both groups and the results were compared. For the study, both groups used the USGS sampling procedure and the USGS Field Leach Test (FLT). The leachates generated from these tests were analyzed for a suite of elements using ICP-AES (CSM) and ICP-MS (USGS). Leachate geochemical fingerprints produced by the two groups for composites collected from the same mine waste showed good agreement. In another set of tests, CSM collected another set of Rattler mine waste composite samples using the USGS sampling procedure. This set of composite samples was leached using the Colorado Division of Minerals and Geology (CDMG) leach test, and a modified Toxicity Characteristic Leaching Procedure (TCLP) leach test. Leachate geochemical fingerprints produced using these tests showed a variation of more than a factor of two from the geochemical fingerprints produced using the USGS FLT leach test. We have concluded that the variation in the results is due to the different parameters of the leaching tests and not due to the sampling or analytical methods.

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The Tip Top Mine in Gamble Gulch, Colorado is a high mountain site where the stream above the mine is pristine and below the influx of acid rock drainage, the aquatic ecosystem appears to be impacted. An aquatic toxicity assessment study was carried out to determine the impact of contaminants on the stream and to test the leaching methods and simple toxicity tests that have been developed at the Colorado School of Mines. All tests show that the stream water above the adit inflow is pristine. However, the stream below shows concentrations of Al, Cu and Zn that are slightly above acute aquatic toxicity limits. Leaching tests on stream sediment samples taken below the adit entrance show concentrations of contaminants that are on the borderline of being toxic. Physical and chemical assessments of the mine waste piles on the site show that they are not impairing the immediate vicinity or the stream. It appears that the cause of any aquatic toxicity is the adit water entering the gulch or the heavy oxyhydroxide precipitates lining the streambed below the mine site.

Paleomagnetism of Late Paleozoic Strata and Mineralizationin the Tri-State Lead-Zinc Ore District

Paleomagnetic results are reported from five Upper Mississippian and 19 Upper Pennsylvanian limestone and black shale sites (272 samples) and from 42 boulders, oriented with respect to their bedding, of Mississippi Valley-type (MVT) mineralization from three mine waste piles (136 samples) in the Tri-State MVT district and along a northward transect to the Kansas City region. Thermal and alternating field-step demagnetization plus saturation isothermal remanence analysis show that the remanence of the samples is carried mostly by single to pseudosingle domain pyrrhotite and/or magnetite. Both outcrop and boulder samples carry a modern A component from a viscous remanent magnetization in the pyrrhotite and/or magnetite and from hematite produced by weathering. The site mean characteristic remanent magnetization (ChRM) from the five Mississippian outcrops (the D component), when combined with data from seven previously published sites, give a middle to Late Mississippian pole position (330 ± 6 Ma, 1 σ ), which indicates that the host rocks for the Tri-State MVT ores retain a primary chemical remanent magnetization. Similarly the site mean ChRM directions for the 19 Pennsylvanian outcrops (the C component) give a Middle Pennsylvanian pole position (313 ± 8 Ma, 1 σ ). Thus, despite the common presence of trace to minor MVT mineralization in a majority of these sites, they are also deemed to retain a primary chemical remanent magnetization. The MVT mineralization in the boulders yields a ChRM (the M component) with an average inclination of 7.4° ± 1.9°, which constrains ore genesis to an equatorial paleolatitude and which was true only from the Middle Pennsylvanian to the Middle Triassic for the study area. Two interpretations are given, using the paleomagnetic data that support epigenetic MVT ore genesis during either the Late Pennsylvanian (304 ± 6 Ma, 1 σ ) or the Late Permian (257 ± 10 Ma, 1 σ ).

Stability Evaluation of a Mine Waste Pile

Research Article| January 01, 2005 Stability Evaluation of a Mine Waste Pile JOHN C. STORMONT; JOHN C. STORMONT 1Department of Civil Engineering, University of New Mexico, Albuquerque, NM 87131 Search for other works by this author on: GSW Google Scholar ENRIQUE FARFAN ENRIQUE FARFAN 1Department of Civil Engineering, University of New Mexico, Albuquerque, NM 87131 Search for other works by this author on: GSW Google Scholar Author and Article Information JOHN C. STORMONT 1Department of Civil Engineering, University of New Mexico, Albuquerque, NM 87131 ENRIQUE FARFAN 1Department of Civil Engineering, University of New Mexico, Albuquerque, NM 87131 Publisher: Association of Environmental & Engineering Geologists First Online: 02 Mar 2017 Online ISSN: 1558-9161 Print ISSN: 1078-7275 Copyright © 2005 Geological Society of America Environmental & Engineering Geoscience (2005) 11 (1): 43–52. https://doi.org/10.2113/11.1.43 Article history First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation JOHN C. STORMONT, ENRIQUE FARFAN; Stability Evaluation of a Mine Waste Pile. Environmental & Engineering Geoscience 2005;; 11 (1): 43–52. doi: https://doi.org/10.2113/11.1.43 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyEnvironmental & Engineering Geoscience Search Advanced Search Abstract Failure of a portion of a mine waste pile motivated a study to identify remaining portions of the pile that were unstable and to suggest appropriate, remedial stabilization efforts. Data collection focused on the principal parameters that control stability, namely, pile geometry and material strength. Data from a topographic survey of the pile and the interpolated bedrock surface under the pile were used to characterize the slope of the mine waste pile and the thickness of the waste material. Strength data were obtained from conventional, small-scale laboratory test methods and a large-scale test method that was used in the field and the laboratory. The small-scale tests, which did not include the relatively coarse fraction of the mine waste material, tended to overestimate the strength of the waste pile material. Strength and pile geometry data were combined in a GIS-based model that provided a first-order, conservative estimate of the stability of the pile based on the infinite slope method. Results from this model indicated three potentially unstable areas. These areas were analyzed using the method of slices. A single location on the pile was found to have an unacceptable factor of safety. A simple grading plan to remediate the problematic location was developed. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Sulfur-isotope distribution and contamination related to the Balya Pb?Zn Mine in Turkey

Sulfur-isotope (δ34S) values and weight (%) of acid-volatile sulfur (AVS), chrome-reducible sulfide (CRS), elemental sulfur (ES), and acid-soluble sulfates were determined in Balya Mine ore rock, mine wastes, and Kocacay River and Lake Manyas sediments. Estimation of isotopic fractionation (Δ34S) between product sulfate and initial CRS (pyrite) was used to evaluate the progress of sulfide oxidation in the mine-waste area. Water- and acid-soluble sulfate produced from different mine-waste samples, such as metallurgical waste (MW) and waste rock (WR), in laboratory experiments also shows distinct δ34S values and allows identification of the acid-mine-drainage sources in the mine-waste area. Average δ34SSO4values are −1.43‰ for MW (n=4) and +2.06‰ for WR (n=8). Short (24 hr) and long (60 days) term leach experiments were considered using alternating wet/dry conditions to simulate sulfate-production capacity and metal-discharge characteristics for MW and WR piles. Release of heavy metals follows the order of Pb2+ >Mn2+ >Zn2+ >Cu2+ for these pile samples. Values of δ34SSO4 for river water that was collected after 3–4 h of heavy rainfall are close to values of δ34SSO4 for water-soluble sulfates from mine-waste piles used in laboratory leach experiments.

Characterization of Heavy Metals and Sulphur Isotope in Water and Sediments of a Mine-Tailing Area Rich in Carbonate

Mine tailings can provide a long-term source of environmental contamination. Lead-zinc mine tailings can represent a source of toxic elements-Pb and Zn through mobilization into surface water, and then into downstream rivers. Previous studies have shown that migration of heavy metals can be mitigated by carbonate rock. This research investigates the characterization of heavy metals and sulphur isotope in a downstream river of the Shanshulin Pb-Zn mine, which is located in Guizhou province in China, a typical carbonate area in the world. A slight alkalinity (pH > 8) of the river water is maintained owing to the carbonate rich country rocks. The results of this study show that heavy metals in water can be strongly adsorbed by suspended solids and therefore decrease more quickly than in sediments. Pb and Zn contents in water close to the waste pile are 6780 μg L-1 and 324 μg L-1 (Pb and Zn in water not affected by mine waste piles are only 3.71 μg L-1 and 11.6 μg L-1), respectively, meaning that the water is severely contaminated by the pile. Thirty kilometers downstream Pb and Zn contents in water drop quickly to 3.15 μg L-1 and 16.4 μg L-1. In contrast, Pb and Zn contents in sediment close to the waste pile are 4553 mg kg-1 and 7971 mg kg-1, respectively, and are still high 30 km downstream with measurements of 3334 mg kg-1 and 7268 mg kg-1 , respectively (Pb and Zn contents in sediment not affected by mine waste piles are only 20 mg kg-1 and 120 mg kg-1). This indicates that the impact of tailings on the sediment can be much further than on water. In sediment, Pb exists mostly as carbonate and oxide fractions, Zn mostly as sulfide+organic fraction, and Cu mostly as sulfide+organic, residual and carbonate fractions. Sulphur characteristics indicate that sulphur in sediment originates from mine tailing, soil and suspended solids in other tributaries, whereas sulphur in water originates from mine tailing dissolution, spring water, rain water and dissolution of gypsum. In conclusion, the environmental impact of mine tailing can be indicated by heavy metals content, sulphur content and sulphur isotope of sediment. On the other hand, heavy metal content, sulphur content or sulphur isotope of water are possibly not good indicators for mine impact due to mitigation of carbonate rocks, sorption of heavy metals, as well as interference of gypsum layers.

Paleomagnetic dating of Upper Mississippi Valley zinc–lead mineralisation, WI, USA

The Upper Mississippi Valley (UMV) zinc–lead district of Wisconsin is located on the northern fringe of the Illinois basin. It was the first major Mississippi Valley-type (MVT) Zn–Pb district to be mined in the United States. Its mineralisation is hosted by Ordovician limestones and dolostones, and has given a 87Rb– 86Sr sphalerite age of 270±4 Ma. One of the few MVT deposits worldwide to be directly dated by this method, it merits comparison with the paleomagnetic dating method for such deposits. Specimens (359) from oriented cores from host rock outcrops and mineralised blocks from mine waste piles at 33 sites have been analysed paleomagnetically using alternating field and thermal step demagnetisation, and some specimens were tested using saturation isothermal remanence methods. The specimens' characteristic remanent magnetisations (ChRM) are carried mostly by pyrrhotite with minor magnetite with a mean direction for the: (a) host limestones at Dec.=151.6°, Inc.=−7.3°( N=5 sites; α 95=6.3°, k=149.8) and (b) dolostones at Dec.=154.8°, Inc.=−7.6°( N=16 sites; α 95=3.5°, k=112.0). An increased ChRM intensity for the mineralised specimens ties their magnetisation to the mineralisation event. The limestones' paleopole plots off the Early Permian and towards the Ordovician portion of the apparent polar wander path for North America, indicating a secondary chemical remagnetisation, possibly with a minor residual primary Ordovician remanence. The dolostones' paleopole at 45.1°N, 126.7°E (δp=1.8°, δm=3.5°) records a secondary chemical remagnetisation from regional dolomitisation during the Early Permian (282±10 Ma). Comparison of the ChRM inclinations for the dolostones and mineralised blocks indicates that the host rocks were remagnetised during mineralisation; that is, the dolomitisation and mineralisation events were about coeval. Thus, the paleomagnetic age confirms the radiometric age for UMV mineralisation. Furthermore, the Early Permian paleomagnetic age agrees with ore genesis models that relate dolomitisation and mineralisation to topographically driven fluid flow during Alleghenian/Ouachitan orogenic uplift.

Atmospheric mercury emissions and speciation at the sulphur bank mercury mine superfund site, Northern California.

One pathway for release of mercury (Hg) from naturally enriched sites is emission to the atmosphere. Elemental Hg, when emitted, will enter the global atmospheric pool. In contrast, if reactive gaseous Hg or Hg2+ (as HgCl2, HgBr2, or HgOH2) is formed, it will most likely be deposited locally. This study focused on the measurement of elemental Hg flux and reactive gaseous Hg concentrations at the Sulphur Bank Superfund Site, an area of natural Hg enrichment with anthropogenic disturbance and ongoing geothermal activity. Mean Hg emissions ranged from 14 to 11000 ng m(-2) h(-1), with the highest emissions from anthropogenically disturbed materials. Reactive gaseous Hg concentrations were the highest ever reported for a natural setting (0.3-76 ng m(-3)). Measured Hg fluxes were used within a Geographic Information System to estimate mercury releases to the atmosphere from the site. Results indicated approximately 17 kg of Hg y(-1) of is emitted to the atmosphere from the 3.8 km2 area, with half from mine waste, ore, and tailing piles and half from relatively undisturbed naturally enriched substrate.

Geological and anthropogenic factors influencing mercury speciation in mine wastes: an EXAFS spectroscopy study

The speciation of Hg is a critical determinant of its mobility, reactivity, and potential bioavailability in mine-impacted regions. Furthermore, Hg speciation in these complex natural systems is influenced by a number of physical, geological, and anthropogenic variables. In order to investigate the degree to which several of these variables may affect Hg speciation, extended X-ray absorption fine structure (EXAFS) spectroscopy was used to determine the Hg phases and relative proportions of these phases present in Hg-bearing wastes from selected mine-impacted regions in California and Nevada. The geological origin of Hg ore has a significant effect on Hg speciation in mine wastes. Specifically, samples collected from hot-spring Hg deposits were found to contain soluble Hg-chloride phases, while such phases were largely absent in samples from silica-carbonate Hg deposits; in both deposit types, however, Hg-sulfides in the form of cinnabar (HgS, hex.) and metacinnabar (HgS, cub.) dominate. Calcined wastes in which Hg ore was crushed and roasted in excess of 600 °C, contain high proportions of metacinnabar while the main Hg-containing phase in unroasted waste rock samples from the same mines is cinnabar. The calcining process is thought to promote the reconstructive phase transformation of cinnabar to metacinnabar, which typically occurs at 345 °C. The total Hg concentration in calcines is strongly correlated with particle size, with increases of nearly an order of magnitude in total Hg concentration between the 500–2000 μm and <45 μm size fractions (e.g., from 97–810 mg/kg Hg in calcines from the Sulphur Bank Mine, CA). The proportion of Hg-sulfides present also increased by 8–18% as particle size decreased over the same size range. This finding suggests that insoluble yet soft Hg-sulfides are subject to preferential mechanical weathering and become enriched in the fine-grained fraction, while soluble Hg phases are leached out more readily as particle size decreases. The speciation of Hg in mine wastes is similar to that in distributed sediments located downstream from the same waste piles, indicating that the transport of Hg from mine waste piles does not significantly impact Hg speciation. Hg LIII-EXAFS analysis of samples from Au mining regions, where elemental Hg(0) was introduced to aid in the Au recovery process, identified the presence of Hg-sulfides and schuetteite (Hg3O2SO4), which may have formed as a result of long-term Hg(0) burial in reducing high-sulfide sediments.

Geochemical assessment of Hg pollution in gold mining sites

The increasing societal demand for actions and strategies towards sustainability of small-scale gold mining in developing countries has led experts to face the challenge of managing the harzards associated with mercury pollution from active and abandoned mine sites. Mercury pollution in drainage systems and its health effects are the most frequent subjects on environmental researchs dealing with small-scale gold mining worldwide. Also, filling of river beds with mineral matter originated from runoff of abandoned mining waste piles and tailings generally causes both silting of waterways and elevation of Hg concentrations in the environment. This paper summarizes the main results concerning the assessment of Hg pollution in Amazon drainage systems accomplished by the authors in the last decade in Brazil.

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Eastern Oklahoma's water resources are impacted by abandoned mine drainage. Passive treatment strategies have been demonstrated to improve water quality at abandoned mines, but watershed reclamation strategies, including a complete assessment of physical habitat degradation of stream ecosystems, are lacking. Mine drainage impacts to three Oklahoma streams were investigated by analyzing water quality, habitat availability, and riffle substrate distribution. Net acidic mine drainage originating from abandoned underground and surface coal mining activities has impacted Pit Creek (Latimer County) for more than 70 years. Beaver and Tar Creeks (Ottawa County) are impacted by net alkaline mine drainage from abandoned lead and zinc mining activities. Overall impact to water quality and habitat availability was assessed. All streams were determined to be impaired by mine drainage originating from discharges, seeps, and leachate derived from mine waste piles. Stream habitat quality varied considerably based on both mining and non-mining related impacts. As a result of this analysis, watershed reclamation strategies, based on passive treatment system design and implementation, will be prioritized and the potential for stream ecosystem recovery evaluated.

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A decision tree that uses simple physical and chemical tests has been developed to determine whether a mine waste poses a toxicity threat to the aquatic environment. For the chemical portion of the tree, leachate tests developed by the US Geological Survey (USGS), the Colorado Division of Minerals and Geology (CDMG), and modified 1311 TCLP test of the EPA have been extensively used. The multi-element power of modern inductively coupled plasma, atomic-emission spectroscopy (ICP-AES) is also a necessary component of the scheme. At two sites in Colorado, Virginia Canyon in the Idaho Springs/Central City Superfund Site and in the Upper Animas River Basin, 25 sediment samples and the water flowing over the sediments were collected. General analytical measurements were made in the field, and then, the water and extracts from the three leachate tests were analyzed for 31 elements by ICP-AES. Then, element concentration pattern graphs (ECPG) were produced that compared selected groups of the elements from the three leachates and the water. When the pHs of the water and the leachate were below 5.0, the element concentration patterns of all four solutions were quite similar and aquatic toxicity from metals such as Pb, Cu, Zn, Mn and Al was clearly indicated. When the pHs of the water and the leachate were above 5.0, the element concentration patterns from the four solutions were different and inferred aquatic toxicity depended on the leachate test. Usually when there was a difference, it was found that in the TCLP test, elements from carbonate minerals and oxides dissolved and these elements in the CDMG and USGS tests were not as readily released from solution. In a study done in 2002 in Russell Gulch near Central City, CO, that rated mine waste piles, it was necessary to rate the contamination possibility of the piles on separate physical and chemical scales for the most complete assessment.

Biosorption of Uranium and Copper by Biocers

Biological ceramic composites (biocers) made according to aqueous sol−gel protocol were used as selective metal binding filters. The biological component of the biocers Bacillus sphaericus JG-A12 was isolated from a uranium mining waste pile. Vegetative cells and spores of this strain are known to bind selectively U, Cu, Al, Cd, and Pb in large amounts. Sol−gel ceramics were prepared by dispersing vegetative cells, spores, and stabilized surface-layer proteins (S-layer) in aqueous silica nanosols, gelling, and drying. The biosorption of uranium and copper by the three kinds of biocers and by their single components was investigated with dependence on time, concentration, and preparation conditions. Biocers with cells possess the highest binding capacity compared to matrixes with spores and an S-layer. Freeze-drying of prepared biocers or adding water-soluble compounds as sorbitol lead to higher porosity and faster metal binding. Uranium was bound mainly to the biological component but also to the SiO2 network. In contrast, copper was only bound by the cells, spores, or S-layer. Bound uranium and copper were completely removed by washing with aqueous citric acid.

An analytical assessment on the impact of covers on the onset of air convection in mine wastes

AbstractIf a mine waste pile is left open, an active chemical reaction of oxidation is often found due to the commonly high content of pyritic materials. The oxidation of pyrites is an exothermic process and the released heat will promote the flow of fresh oxygen from the surrounding atmosphere into the waste dump. As a result, oxidation reaction will accelerate and temperature within the dump can increase to as high as 60°C above the ambient temperature. The oxidation process also releases sulphuric acid and hydrogen ions into ground water to cause water contamination. Low‐permeability covers such as clay liners have been recently proposed to abate the oxidation process in mine wastes. The effectiveness of using low‐permeability materials to cover mine wastes in order to suppress the pyrite oxidation is examined. By conducting the theoretical analysis of the onset of convective air flow within waste rocks, the conditions under which soil gas flow is significant are identified. By comparing the results with previous field measurements and theoretical analysis for the uncovered conditions, it is shown that low‐permeability covers can effectively suppress soil gas flow and slow down the pyrite oxidation process in mine wastes. Copyright © 2001 John Wiley &amp; Sons, Ltd.

Arsenic content and groundwater geochemistry of the San Antonio-El Triunfo, Carrizal and Los Planes aquifers in southernmost Baja California, Mexico

The San Antonio-El Triunfo mining district, located at a mountainous region 45 km south-east of La Paz, Baja California, has been worked since the late 1700s. Mine waste material produced during 200 years of mineral extraction area poses a risk of local groundwater pollution and eventually, regional pollution to the Carrizal (west basin) and the Los Planes (east basin) aquifers. There are different types of deposits in the mining area. These are dominated by epithermal veins, in which arsenopyrite is an important component. Carrillo and Drever (1998a) concluded that, even though the amount of mine waste is relatively small in comparison to the large scale area, significant As in groundwater derived from the mine waste piles is found locally in the groundwater. This paper shows the results of geochemical analyses of groundwater samples from the San Antonio-El Triunfo area and the Carrizal and Los Planes aquifers during several years of monitoring (1993–1997). The highest values of total dissolved solids (TDS) and As are in the mineralized area where the mining operations occurred (∼1500 ppm TDS and 0.41 ppm As). The lowest concentrations of TDS and As are, in general, away from the mineralized area (∼500 ppm TDS and 0.01 ppm As). Sulfate and bicarbonate (alkalinity) are, in general, high near the mineralized area and low away from it. The arsenic concentrations vary seasonally, especially after the heavy summer thunderstorms. Geochemical modeling (MINTEQA2 and NETPATH) and analysis of the regional geochemical evolution of the groundwater from the mining area towards the aquifer of Los Planes shows that the most likely hydrochemical processes include: dilution, precipitation of calcite, and adsorption of As onto surfaces of iron oxyhydroxides (ferrihydrite). These processes act as natural controls to the extent and amount of As pollution in the Carrizal and Los Planes aquifers.

Complex formation of U(VI) with Bacillus-isolates from a uranium mining waste pile

Accumulation studies with vegetative cells and spores of three Bacillus isolates (JG-A 30, JG-A 12, JG-A 22, classified as Bacillus cereus, Bacillus sphaericus, Bacillus megaterium) from a uranium mining waste pile (Johanngeorgenstadt, Saxony) and their corresponding reference strains have shown that Bacilli accumulate high amounts of U(VI) in the concentration range examined (11-214 mg/L). Information on the binding strength and the reversibility were obtained from extraction studies with different extractants. With 0.01 M EDTA solution the uranium bound to the biomass was released almost quantitatively. The characterization of the bacterial-UO22+-complexes by time-resolved laser fluorescence spectroscopy (TRLFS) showed the formation of inner-sphere complexes with phosphate groups of the biomass. The results lead to the conclusion that the cell wall components with phosphate residues e.g., polysaccharides, teichoic and teichuroic acids or phospholipide layers of the membranes are responsible for the uranium binding. The spectroscopic studies of the U(VI)-complexes with isolated bacterial cell walls and isolated surface-layer proteins of the strain Bacillus sphaericus NCTC 9602 after cell fractionation have shown that the complexation of U(VI) with intact cells (vegetative cells or spores) is different from the coordination with isolated cell wall components, especially with the S-layer proteins. For all Bacillus strains studied in this work, a significant contribution of the S-layer proteins to the binding of uranyl to living cells can be excluded.

Using Imaging Spectroscopy To Map Acidic Mine Waste

The process of pyrite oxidation at the surface of mine waste may produce acidic water that is gradually neutralized as it drains away from the waste, depositing different Fe-bearing secondary minerals in roughly concentric zones that emanate from mine-waste piles. These Fe-bearing minerals are indicators of the geochemical conditions under which they form. Airborne and orbital imaging spectrometers can be used to map these mineral zones because each of these Fe-bearing secondary minerals is spectrally unique. In this way, imaging spectroscopy can be used to rapidly screen entire mining districts for potential sources of surface acid drainage and to detect acid producing minerals in mine waste or unmined rock outcrops. Spectral data from the AVIRIS instrument were used to evaluate mine waste at the California Gulch Superfund Site near Leadville, CO. Laboratory leach tests of surface samples show that leachate pH is most acidic and metals most mobile in samples from the inner jarosite zone and that leachate pH is near-neutral and metals least mobile in samples from the outer goethite zone.

Use of sample color to estimate oxidized Fe content in mine waste rock

Color, a readily perceived feature of nat- ural earth materials, including mine waste, often represents compositional variation as a result of oxidative processes involving Fe. Near surface sam- ples from excavated trenches in a mine-waste rock pile were collected to investigate the relationship between color and contents of Fe, Cu, and S. The siltcclay fraction (~0.05 mm) was isolated from recognizable colored material of the bulk sample for determination of pH, total and extractable Fe and Cu, and bulk mineralogy. Rock fragments within the pile exhibited coatings of crystalline gyp- sum and amorphous Fe. These coatings result from weathering (secondary products) and play impor- tant roles in surface reactions of waste rock piles, such as adsorption of anions (SO4 2- ) or coprecipi- tation of Fe with Cu. The correlation between color (Hurst method) and extractable Fe was high. Al- though color is influenced by site conditions such as original mineral composition, materials han- dling, weathering conditions etc., the results sug- gest that color measurements may provide an inex- pensive and rapid estimation for secondary iron compounds and associated sorbed elements.

Prevention of Acid Mine Drainage by Sulfate Reducing Bacteria: Organic Substrate Addition to Mine Waste Piles

Coal or mineral mining operations generate pyritic wastes that are often deposited at open lands near the mine sites. Chemical or biochemical oxidation of pyrites in the waste piles results in the production of sulfuric acid solutions with pH values frequently less than 2. In addition, these low pH leachates often contain high concentrations of toxic heavy metals. This study addresses an innovative approach to prevent the production of acidic leachate from mining waste piles by promoting the growth of sulfate-reducing bacteria (SRB) within the piles. The activity of SRB is known to neutralize acids and stabilize toxic metals as non-bioavailable metal sulfide precipitates. Batch and column studies were conducted to evaluate the feasibility of inoculating mine waste piles with SRB and stimulating their activities for in situ treatment of acidic leachates containing toxic metals. Inoculation of mine waste materials in batch reactors with SRB cultures resulted in the neutralization of acidic supernatant (pH ∼ 3) to pH values of 7.0 and above. During batch incubation of SRB, the dissolved concentrations of Cd, Cu, Ni, and Zn in the supernatant were decreased to undetectable levels. In continuous-flow column experiments containing SRB/mine waste materials, effluent pHs above pH 7 and metal removal efficiencies of greater than 99% for Cd, Cu, and Zn, and 87% for Ni were attained due to the activity of SRB in mine waste columns. Key words: Acid mine drainage; sulfate reducing bacteria; mine waste piles