Acid Rock Drainage

The Texas Mining and Reclamation Association (TMRA) has sponsored a soil sample round robin program since 1990. To date, 17 different soil samples (including blind duplicate samples M and P) have been analyzed in a series of six rounds of analysis. Five laboratories have participated in this program. Three of these were commercial laboratories, one was an electric utility's in-house laboratory, and one was the state regulatory authority's laboratory. Samples submitted for analysis included minesoils and native soils. Results indicate that average inter-laboratory variability was approximately five times greater than intra-laboratory variability. The level of variation was affected by the sample being analyzed and the analytical parameter that was involved. The larger inter-laboratory variability suggest that a greater convergence of analytical results may be attained through a rigorous examination of individual laboratory methodologies and implementation of widely-used standard operating procedures (SOPs). An examination of coefficient of variation (C.V.) data from twelve analytical parameters indicated that pH was the least variable and trace elements were among the most variable. The inclusion of near minimum detection level (MDL) values tended to increase the C.V. of data. Analyses of variance (ANOV A) indicated that the sources of variation of most parameters were inconsistent over time. Differences in equipment, sample extraction, and personnel could also account for different values among the laboratories. Analytical parameters that exhibited a sample by laboratory (S XL) interaction suggest that there was inconsistency among laboratories over time. Samples M and P were blind duplicates of the same sample, included in the round robin to assess the precision of the participating laboratories. Results of samples M and P indicate that there was either a significant laboratory main-effect or S X L interaction for most of the analytical parameters, suggesting that either lab inconsistencies or sample heterogeneity could be the cause. The use of a standard reference material (SRM), with known parameter values, can help identify which laboratories are accurate. There are analytical considerations that require attention, such as sample preparation and pretreatment, sample extraction, and both determinate and indeterminate errors. Sample preparation is a critical step where variability can be introduced. The development and implementation ofSOPs are essential steps for any laboratory. The variable results obtained by the TMRA round robin program illustrate the need for QA/QC procedures and the use of good laboratory practices. The program's results also prompted the following questions: 1) are the levels of variability of sufficient importance to warrant additional research and 2) are there practical mine reclamation implications to the variability exhibited in the round robin data?

Extracellular polymeric substances (EPS) seem to play a pivotal role in bioleaching-the winning of precious metals as well as acid rock drainage. For a better control of both processes structure and function of extracellular polymeric substances from leaching bacteria are of crucial importance. Our research focussed on Acidithibacillus ferrooxidans, the composition of its extracellular polymeric substances and further deduction of their function. The extracellular polymeric substances of Acidithiobacillus ferrooxidans consist mainly of neutral sugars and lipids. The functions of the extracellular polymeric substances of this leaching bacterium seem to be (i) to mediate attachment to a (metal) sulfide surface, (ii) to concentrate iron(III) ions by complexation through uronic acids or other residues at the mineral surface and, thus, allowing for an oxidative attack on the sulfide. Consequently, dissolution of the metal sulfide is enhanced, which may result in an acceleration of 20-to 100-fold over chemical leaching. Experiments were performed to elucidate the importance of the iron(III) ions complexed by extracellular polymeric substances for strain-specific differences in oxidative activity for pyrite. The preliminary data indicate that strains of Acidithiobacillus ferrooxidans, with a high amount of iron(III) ions in their extracellular polymeric substances, possess a higher oxidation activity than those with less iron(III) ions. These data provide new insight into the function of extracellular polymeric substances and the consequent advantage conferred to bacteria involved in bioleaching.

A five-year, humidity-cell experiment was used to study the weathering evolution of a low-sulfide, granitic waste rock at 5 and 22 °C. Only the rock with the highest sulfide content (0.16 wt %) released sufficient acid to overcome a limited carbonate acid-neutralization capacity and produce a substantial decline in pH. Leached SO 4 and Ca quickly increased then decreased during the first two years of weathering. Sulfide oxidation continued to release acid and SO 4 after carbonate depletion, resulting in an increase in acid-soluble elements, including Cu and Zn. With the dissolution of Al-bearing minerals, the pH stabilized above 4, and sulfide oxidation continued to decline until the end of the experiment. The variation in activation energy of sulfide oxidation correlates with changes in sulfide availability, where the lowest activation energies occurred during the largest releases of SO 4 . A decrease in sulfide availability was attributed to consumption of sulfide and weathered rims on sulfide grains that reduced the oxidation rate. Varying element release rates due to changing carbonate and sulfide availability provide identifiable

The Lake Creek watershed in Colorado is an excellent, unique, natural outdoor laboratory for studying naturally occurring acid rock drainage (ARD) and other hydrogeochemical processes involving metal transport and deposition. ARD originates in Peekaboo Gulch, Sayres Gulch, and Sayres Bowl Stream, headwater tributaries of Lake Creek that drain low-grade Cu-Mo hydrothermal systems associated with the Grizzly Peak Caldera, host of an Oligocene, calc- alkaline porphyry. The watershed receives no visible contribution of ARD from mining or other anthropogenic disturbances. The pH in Peekaboo Gulch, Sayres Gulch, and Sayres Bowl Stream starts in the 2.5-3.0 range, but is naturally neutralized by freshwater tributaries to Lake Creek and ultimately attains a pH of 7.7 at the confluence with the Arkansas River, 37 kilometers downstream. Dissolved concentrations of 277 mg/L Al, 498 mg/L Fe, 10 mg/L Cu, and 1,180 µg/L Zn in the acidic headwaters are naturally attenuated downstream to 0.014 mg/L...

Acid rock drainage from diffuse sources such as waste rock dumps, tailings impoundments and discard coal dumps represents a significant environmental risk to South Africa, particularly with respect to sulphate salinity. Passive or semi-passive remediation options may be more practical, sustainable and affordable in many cases. Where sulphate salinity is a concern, biological sulphate reduction (BSR) plays a key role. Widespread application of BSR has been constrained by the cost of the electron donor, process kinetics and management of the sulphide product. The system developed addresses the challenge of biomass retention by employing submerged carbon microfibers to provide a large surface area for microbial attachment. Electron donor for the sulphate reduction and sulphide oxidation is provided by the anaerobic degradation of complex organic carbon sources (eg grass, algae, manure) in a separate hydrolysis reactor. Finally, sulphide management is achieved through the partial oxidat...

Hickory Log Creek Dam is a proposed 55 meter high roller compacted concrete dam located on a tributary of the Etowah River near Canton, Georgia. The site characterization involved several approaches that facilitated the rapid foundation investigation schedule. These included identification of critical data needs, design of the program to collect these data, and selection of preferred data acquisition and evaluation. The foundation area of the dam is composed of fresh relatively unfractured mica schist in the stream valley and a mantle of residual soil and partially weathered rock on the abutment hillslopes.

Weathering of metal-sulfide minerals produces suites of variably soluble efflorescent sulfate salts at a number of localities in the eastern United States. The salts, which are present on mine wastes, tailings piles, and outcrops, include minerals that incorporate heavy metals in solid solution, primarily the highly soluble members of the melanterite, rozenite, epsomite, halotrichite, and copiapite groups. The minerals were identified by a combination of powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and electron-microprobe. Base-metal salts are rare at these localities, and Cu, Zn, and Co are commonly sequestered as solid solutions within Fe-and Fe-Al sulfate minerals. Salt dissolution affects the surfacewater chemistry at abandoned mines that exploited the massive sulfide deposits in the Vermont copper belt, the Mineral district of central Virginia, the Copper Basin (Ducktown) mining district of Tennessee, and where sulfide-bearing metamorphic rocks undisturbed by mining are exposed in Great Smoky Mountains National Park in North Carolina and Tennessee. Dissolution experiments on composite salt samples from three minesites and two outcrops of metamorphic rock showed that, in all cases, the pH of the leachates rapidly declined from 6.9 to b3.7, and specific conductance increased gradually over 24 h. Leachates analyzed after 24-h dissolution experiments indicated that all of the salts provided ready sources of dissolved Al (N30 mg L À1 ), Fe (N47 mg L À1 ), sulfate (N1000 mg L À1 ), and base metals (N1000 mg L À1 for minesites, and 2 mg L À1 for other sites). Geochemical modeling of surface waters, mine-waste leachates, and salt leachates using PHREEQC software predicted saturation in the observed ochre minerals, but significant concentration by evaporation would be needed to reach saturation in most of the sulfate salts. Periodic surface-water monitoring at Vermont minesites indicated peak annual metal loads during spring runoff. At the Virginia site, where no winter-long snowpack develops, metal loads were highest during summer months when salts were dissolved periodically by rainstorms following sustained evaporation during dry spells. Despite the relatively humid climate of the eastern United States, where precipitation typically exceeds evaporation, salts form intermittently in open

Reaction modeling can be a valuable tool in predicting the long-term behavior of waste material if representative rate constants can be derived from long-term leaching tests or other approaches. Reaction modeling using the REACT program of the Geochemist's Workbench was conducted to evaluate long-term drainage quality affected by disseminated Cu-Ni-(Co-)-PGM sulfide mineralization in the basal zone of the Duluth Complex where significant resources have been identified. Disseminated sulfide minerals, mostly pyrrhotite and Cu-Fe sulfides, are hosted by clinopyroxene-bearing troctolites. Carbonate minerals are scarce to non-existent. Long-term simulations of up to 20 years of weathering of tailings used two different sets of rate constants: one based on published laboratory single-mineral dissolution experiments, and one based on leaching experiments using bulk material from the Duluth Complex conducted by the Minnesota Department of Natural Resources (MNDNR). The simulations included only plagioclase, olivine, clinopyroxene, pyrrhotite, and water as starting phases. Dissolved oxygen concentrations were assumed to be in equilibrium with atmospheric oxygen. The simulations based on the published single-mineral rate constants predicted that pyrrhotite would be effectively exhausted in less than two years and pH would rise accordingly. In contrast, only 20 percent of the pyrrhotite was depleted after two years using the MNDNR rate constants. Predicted pyrrhotite depletion by the simulation based on the MNDNR rate constant matched well with published results of laboratory tests on tailings. Modeling long-term weathering of mine wastes also can provide important insights into secondary reactions that may influence the permeability of tailings and thereby affect weathering behavior. Both models predicted the precipitation of a variety of secondary phases including goethite, gibbsite, and clay (nontronite).

Previous attempts to identify the source of Ni in acid rock drainage associated with coal mining operations within the Buller coalfield, West Coast, New Zealand, have identified the source rock as mudstones and coals, but not the source mineral. This work using time-of-flight secondary ion mass spectrometry (ToF-SIMS) investigated the Ni content of pyrite contained within the Eocene Kaiata mudstone, the dominant mudstone conformably overlying and laterally interfingering with the coal bearing Brunner Coal Measures. Results conclusively demonstrate that the predominant source of Ni within this lithological unit is pyrite, which agrees with previous results that indicated that the pyrite rich mudstones and coals are the source for Ni rather than the low pyrite sandstone units. If pyrite oxidation and hence acid rock drainage can be controlled by appropriate management methods then by association Ni is also controlled.

Characterisation of mine waste rock with respect to acid generation potential is a necessary part of routine mine operations, so that environmentally benign waste rock stacks can be constructed for permanent storage. Standard static characterisation techniques, such as acid neutralisation capacity (ANC), maximum potential acidity, and associated acid-base accounting, require laboratory tests that can be difficult to obtain rapidly at remote mine sites. We show that a combination of paste pH and a simple portable carbonate dissolution test, both techniques that can be done in the field in a 15 min time-frame, is useful for distinguishing rocks that are potentially acid-forming from those that are acid-neutralising. Use of these techniques could allow characterisation of mine wastes at the metre scale during mine excavation operations. Our application of these techniques to pyrite-bearing (total S = 1-4 wt%) but variably calcareous coal mine overburden shows that there is a strong correlation between the portable carbonate dissolution technique and laboratory-determined ANC measurements (range of 0-10 wt% calcite equivalent). Paste pH measurements on the same rocks are bimodal, with high-sulphur, lowcalcite rocks yielding pH near 3 after 10 min, whereas high-ANC rocks yield paste pH of 7-8. In our coal mine example, the field tests were most effective when used in conjunction with stratigraphy. However, the same field tests have potential for routine use in any mine in which distinction of acid-generating rocks from acid-neutralising rocks is required. Calibration of field-based acidbase accounting characteristics of the rocks with laboratory-based static and/or kinetic tests is still necessary.

A sampling protocol for the retention, extraction, and analysis of sulfoxyanions in hydrothermal waters has been developed in the laboratory and tested at Yellowstone National Park and Green Lake, NY. Initial laboratory testing of the anion-exchange resin Bio-Rad 2 AG1-X8 indicated that the resin was well suited for the sampling, preservation, and extraction of sulfate and thiosulfate. Synthetic solutions containing sulfate and thiosulfate were passed through AG1-X8 resin columns and eluted with 1 and 3 M KCl, respectively. Recovery ranged from 89 to 100%. Comparison of results for water samples collected from five pools in Yellowstone National Park between on-site IC analysis (U.S. Geological Survey mobile lab) and IC analysis of resin-stored sample at SUNY-Stony Brook indicates 96 to 100% agreement for three pools (Cinder, Cistern, and an unnamed pool near Cistern) and 76 and 63% agreement for two pools (Sulfur Dust and Frying Pan). Attempts to extract polythionates from the AG1-X8 resin were made using HCl solutions, but were unsuccessful. Bio-Rad 2 AG2-X8, an anion-exchange resin with weaker binding sites than the AG1-X8 resin, is better suited for polythionate extraction. Sulfate and thiosulfate extraction with this resin has been accomplished with KCl solutions of 0.1 and 0.5 M, respectively. Trithionate and tetrathionate can be extracted with 4 M KCl. Higher polythionates can be extracted with 9 M hydrochloric acid. Polythionate concentrations can then be determined directly using ion chromatographic methods, and laboratory results indicate recovery of up to 90% for synthetic polythionate solutions using AG2-X8 resin columns.

The formation of acid mine drainage from metals extraction or natural acid rock drainage and its mixing with surface waters is a complex process that depends on petrology and mineralogy, structural geology, geomorphology, surface-water hydrology, hydrogeology, climatology, microbiology, chemistry, and mining and mineral processing history. The concentrations of metals, metalloids, acidity, alkalinity, Cl À , F À and SO 2À 4 found in receiving streams, rivers, and lakes are affected by all of these factors and their interactions. Remediation of mine sites is an engineering concern but to design a remediation plan without understanding the hydrogeochemical processes of contaminant mobilization can lead to ineffective and excessively costly remediation. Furthermore, remediation needs a goal commensurate with natural background conditions rather than water-quality standards that might bear little relation to conditions of a highly mineralized terrain. This paper reviews hydrogeochemical generalizations, primarily from US Geological Survey research, that enhance our understanding of the origin, transport, and fate of contaminants released from mined and mineralized areas. Mobility of potential or actual contaminants from mining and mineral processing activities depends on (1) occurrence: is the mineral source of the contaminant actually present? (2) abundance: is the mineral present in sufficient quantity to make a difference? (3) reactivity: what are the energetics, rates, and mechanisms of sorption and mineral dissolution and precipitation relative to the flow rate of the water? and (4) hydrology: what are the main flow paths for contaminated water? Estimates of relative proportions of minerals dissolved and precipitated can be made with mass-balance calculations if minerals and water compositions along a flow path are known. Combined with discharge, these mass-balance estimates quantify the actual weathering rate of pyrite mineralization in the environment and compare reasonably well with laboratory rates of pyrite oxidation except when large quantities of soluble salts and evaporated mine waters have accumulated underground. Quantitative mineralogy with trace-element compositions can substantially improve the identification of source minerals for specific trace elements through mass balances. Post-dissolution sorption and precipitation (attenuation) reactions depend on the chemical behavior of each element, solution composition and pH, aqueous speciation, temperature, and contact-time with mineral surfaces. For example, little metal attenuation occurs in waters of low pH (<3.5) and metals tend to maintain element ratios indicative of the main mineral or group of minerals from which they dissolved, except Fe, SiO 2 , and redox-sensitive oxyanions (As, Sb, Se, Mo, Cr, V). Once dissolved, metal and metalloid concentrations are strongly affected by redox conditions and pH. Iron is the most reactive because it is rapidly oxidized by bacteria and archaea and Fe(III) hydrolyzes and precipitates at low pH (1-3) which is related directly to its first hydrolysis constant, pK 1 = 2.2. Several insoluble sulfate minerals precipitate at low pH including anglesite, barite, jarosite, alunite and basaluminite. Aluminum hydrolyzes near pH 5 (pK 1 = 5.0) and provides buffering and removal of Al by mineral precipitation from pH 4-5.5. Dissolved sulfate behaves conservatively because the amount removed from solution by precipitation is usually too small relative to the high concentrations in the water column and relative to the flow rate of the water.

A strategic business case analysis and five-year plan are presented here for the Teck Applied Mineralogy group in Trail, British Columbia. Applied mineralogy is a key technical competency for Teck Resources that adds value in the fields of process mineralogy supporting optimization at the mining operations, and in ore characterization supporting evaluation of greenfield and brownfield properties. This 2016-2020 business plan for the applied mineralogy group is cognisant of the current mining industry downturn and recommends only incremental increases in staffing and project budgets during the period. Importantly, the plan recommends improved positioning of the group within Teck to maximize its contributions and a focus on customer relationships and timely delivery of value to projects. It also recommends the development of strategic outsourcing partnerships with commercial providers of applied mineralogy, including development of QA/QC protocols, so that this service is well managed within the company as a whole. There are some key capital expenditures necessary for the group in the next five years, including the replacement of mineralogical instrumentation, but their timing can be managed to coincide with improving corporate economics.

Increasing competition within the cement industry and growing concerns about sustainable cement production have placed more rigorous demands on maintenance in cement plants, including the maintenance of the kiln. Therefore, kiln maintenance requires a more dedicated focus than ever.

Introduction: Sample return from Mars offers the promise of data from Martian materials that have previously only been available from meteorites. Return of carefully selected samples may yield more information about the history of water and possible habitability through Martian history. Here we propose that samples collected from Mars should include depth profiles of material across the interface between weathered material on the surface of Mars into unweathered parent rock material. Such profiles have the potential to yield chemical ...

This contribution analyzes water chem-1 ical data for the Choapa basin, North Central 2 Chile, for the period 1980-2004. The parameters 3 considered are As, Cu Fe, pH, EC, SO −2 4 , Cl −1 , 33 Keywords Acid rock drainage • 34 Hydrothermal alteration • Andean mining • 35 Drainage geochemistry • Water quality 36

Acid Rock Drainage (ARD), or Acid Mine Drainage, is a naturally occurring process often accelerated by mining activity. ARD may be misinterpreted as mining related, when in fact, it relates to natural hydrogeochemical processes associated with existing mineral ...

The quality of water in streams that are contaminated by acid drainage from mines and from the weathering of mineralized rocks improves as the water flows downstream. The purpose of this study was to investigate the geochemical processes that occur in one such stream and to determine the fate of the trace metals that are removed from the water. The stream chosen for this purpose was the Snake River, Summit County, Colorado, which is affected by natural acid rockdrainage (ARD) containing SO 4 , Al, Fe, and various trace elements such as Zn, Cu, Pb, Ni, and others. Most of the Fe in the Snake River is removed from solution by the oxidation of Fe 2+ to Fe 3+ and the subsequent precipitation of Fe-oxyhydroxides that form a massive ferricrete deposit near the springs that feed the river. Further downstream, the Snake River (pH=3.0) mixes with water from Deer Creek (pH= 7.0) thereby increasing its pH to 6.3 and causing SO 4-rich precipitates of Al-oxyhydroxide to form. The precipitates and associated organic C complexes sorb trace metals from the water and thus have high concentrations of certain elements, including Zn (540-11,400 ppm), Cu (34-221 ppm), Pb (90-340 ppm), and Ni (11-197 ppm). The concentrations of these elements in the precipitates that coat the streambed rise steeply in the zone of mixing and then decline downstream. The trace element concentrations of the water in the mixing zone at the confluence with Deer Creek decrease by 75% or more and are up to 3 orders of magnitude lower than those of the precipitates. Sorption curves for Zn, Cu, Pb, Ni, and SO 4 were derived by stepwise neutralization of a sample of Snake River water (collected above the confluence with Deer Creek) and indicate that the trace metals are sorbed preferentially with increasing pH in the general order Pb, Cu, Zn, and Ni. Sulfate is removed between pH 4 and 5 to form an Al-hydroxysulfate and/or by sorption to microcrystalline gibbsite. The sorption data determined from the neutralization experiment were used to account for the downstream decrease of trace-metal concentrations in the precipitates. The results of this study demonstrate that the partitioning of trace metals in the Snake River is not only a function of pH, but also depends on the progressive removal of trace metals as the water of the Snake River flows through its confluence with Deer Creek. The chemical composition of the water also determines what compounds precipitate with increasing pH.

Principal Component Analysis (PCA) applies in order to understand the interrelationships between the variables analyzed to determine the degree of alteration of the water of Coyuca de Benitez lagoon, at Guerrero, Mexico. Temperature, pH, dissolved oxygen, conductivity, TDS, salinity, diversity, abundance, class 1, 2, 3 (oxygen requirements by insects) and orders of insects collected: physicochemical and biological variables were considered. The results illustrate the application of the PCA, which allowed finding that the variables Temperature, pH and dissolved Oxygen showed higher interrelationships in this lentic system. Keywords— ACP, relationships, alteration, lineal relationship, macroinvertebrates Resumen— Se aplicó el Análisis de Componentes Principales (ACP), con el objeto de conocer las interrelaciones entre las variables analizadas que determinan el grado de alteración del agua de la Laguna de Coyuca de Benítez, en Guerrero, México. Se consideraron variables fisicoquímicas ...

fundado el 2 de febrero de 2018, reúne a un grupo de amigos tras la meta de contribuir activamente en la difusión de conocimientos sobre el desarrollo de la investigación histórica regional a través de talleres, jornadas, seminarios y labores de extensión hacia la comunidad local y nacional. El Colectivo es una organización de base, con personalidad jurídica funcional, otorgada por la Ilustre Municipalidad de La Serena, bajo el Registro N° 3013 del 2 de febrero de 2018. "El Chasqui, Región de Coquimbo, Chile" es un boletín que tiene como objetivo, ser una vía de expresión respecto a las actividades llevadas a cabo por el Colectivo de Estudios Históricos de la Región de Coquimbo, el cual será distribuido digitalmente por redes sociales.

fundado el 2 de febrero de 2018, reúne a un grupo de amigos tras la meta de contribuir activamente en la difusión de conocimientos sobre el desarrollo de la investigación histórica regional a través de talleres, jornadas, seminarios y labores de extensión hacia la comunidad local y nacional. DIRECTIVA PRESIDENTE, GABRIEL CANIHUANTE SECRETARIO, GASTÓN CASTILLO GÓMEZ TESORERO, JULIO CORTÉS MIRANDA El Colectivo es una organización de base, con personalidad jurídica funcional, otorgada por la Ilustre Municipalidad de La Serena, bajo el Registro N° 3013 del 2 de febrero de 2018. "El Chasqui, Región de Coquimbo, Chile" es un boletín que tiene como objetivo, ser una vía de expresión respecto a las actividades llevadas a cabo por el Colectivo de Estudios Históricos de la Región de Coquimbo, el cual será distribuido digitalmente por redes sociales.

The geomicrobiological characterization of the water column and sediments of Río Tinto (Huelva, Southwestern Spain) have proven the importance of the iron and the sulfur cycles, not only in generating the extreme conditions of the habitat (low pH, high concentration of toxic heavy metals), but also in maintaining the high level of microbial diversity detected in the basin. It has been proven that the extreme acidic conditions of Río Tinto basin are not the product of 5000 years of mining activity in the area, but the consequence of an active underground bioreactor that obtains its energy from the massive sulfidic minerals existing in the Iberian Pyrite Belt. Two drilling projects, MARTE (Mars Astrobiology Research and Technology Experiment) (2003-2006) and IPBSL (Iberian Pyrite Belt Subsurface Life Detection) (2011-2015), were developed and carried out to

During the operation of a mine, waste rock is often deposited in heaps and usually left under ambient conditions allowing sulfides to oxidize. To focus on waste rock management for preventing acid rock drainage (ARD) formation rather than ARD treatment could avoid its generation and reduce lime consumption, costs, and sludge treatment. Leachates from 10 L laboratory test cells containing sulfide-rich (> 60% pyrite) waste rock with and without the addition of lime kiln dust (LKD) (5 wt.%) were compared to each other to evaluate the LKD's ability to maintain near neutral pH and reduce the sulfide oxidation. Leaching of solely waste rock generated an acidic leachate (pH < 1.3) with high concentrations of As (21 mg/L), Cu (20 mg/L), Fe (18 g/L), Mn (45 mg/L), Pb (856 μg/L), Sb (967 μg/L), S (17 g/L), and Zn (23 mg/L). Conversely, the addition of 5 wt.% LKD generated and maintained a near neutral pH along with decreasing of metal and metalloid concentrations by more than 99.9%. Decreased concentrations were most pronounced for As, Cu, Pb, and Zn while S was relatively high (100 mg/L) but decreasing throughout the time of leaching. The results from sequential extraction combined with element release, geochemical calculations, and Raman analysis suggest that S concentrations decreased due to decreasing sulfide oxidation rate, which led to gypsum dissolution. The result from this study shows that a limited amount of LKD, corresponding to 4% of the net neutralizing potential of the waste rock, can prevent the acceleration of sulfide oxidation and subsequent release of sulfate, metals, and metalloids but the quantity and long-term stability of secondary minerals formed needs to be evaluated and understood before this method can be applied at a larger scale.

A dissolution rate law for galena in acidic environment was derived from the steady-state dissolution rates using flow-through experiments. The influence of temperature, dissolved oxygen concentration and pH between 1 and 3 was assessed. This rate law can be used for predicting galena dissolution behavior in a wide range of conditions analogous to Acid Rock Drainage. For pH below 2, the dissolution rate law can be expressed as: R Gn;pHb2 ¼ 10 À5:7F0:4 e À23F3 RT a 0:43F0:05 H þ where R Gn is the galena dissolution rate (mol m − 2 s − 1), R is the gas constant (kJ mol − 1 K − 1) , T is the temperature (K) and a H þ is the activity of hydrogen ion in the solution. Galena dissolution rate law for pH between 2 and 3 can be expressed as: R Gn;pH¼2À3 ¼ 10 À8:5F0:4 e À15F2 RT a À0:78F0:04 H þ a 0:30F0:03 O 2 aq ð Þ where a O 2 aq ð Þ is the activity of dissolved oxygen. XPS (X-ray Photoelectron Spectroscopy) examination of the reacted galena samples shows the formation of a lead-deficient and sulfur-rich surface layer, consistent with the observed non-stoichiometry between dissolved sulfur and lead in all the studied solutions. Based on the S/Pb ratio observed in solution and the reacted surfaces and the pH and dissolved oxygen dependence of the rates, two possible reactions for galena dissolution in acidic aqueous solution are proposed; (1) at pH ≤ 2 the rate seems to be determined by the protonation of surface sulfur atoms, and (2) at pH ≥ 2 the rate seems to be controlled by the attachment of oxygen to surface sulfur atoms. The values obtained for the activation energies (15 ± 2 kJ mol − 1 at pH 3 and 23 ± 3 kJ mol − 1 at pH 1) suggest that galena dissolution is controlled by diffusion processes or mixed-controlled by diffusion of reactants and products between the bulk solutions and the reacting surfaces.

Schwertmannite is a ubiquitous mineral formed from acid rock drainage (ARD), and plays a major role in controlling the water chemistry of many acid streams. The formation of schwertmannite was investigated in the acid discharge of the Monte Romero abandoned mine (Iberian Pyrite Belt, SW, Spain). Schwertmannite precipitated from supersaturated solutions mainly owing to the oxidation of Fe(II) to Fe(III) and transformed with time into goethite and jarosite. In a few hours, schwertmannite precipitation removed more than half of the arsenic load from solution, whereas the concentration of divalent trace metals (Zn, Cu, Pb, Cd, Ni, and Co) remained almost unchanged. In the laboratory, natural schwertmannite was kept in contact with its coexisting acid water in a flask with a solid-liquid mass ratio of 1:5 for 353 days. During this time, the pH of the solution dropped from 3.07 to 1.74 and the concentrations of sulfate and Fe increased. During the first 164 days, schwertmannite transformed into goethite plus H 3 O-jarosite but, subsequently, goethite was the only mineral to form. Some of the trace elements, such as Al, Cu, Pb, and As were depleted in solution during the first stage as schwertmannite transformed into goethite plus H 3 O-jarosite. On the contrary, the transformation of schwertmannite to goethite (with no jarosite) during the second stage released Al, Cu, and As to the solution. Despite the variation in their concentrations in solution, approximately 80% of the total Al and Cu inventories and more than 99% As and Pb remained in the solid phase throughout the entire aging process.

Your article is protected by copyright and all rights are held exclusively by Springer-Verlag Berlin Heidelberg. This e-offprint is for personal use only and shall not be selfarchived in electronic repositories. If you wish to self-archive your article, please use the accepted manuscript version for posting on your own website. You may further deposit the accepted manuscript version in any repository, provided it is only made publicly available 12 months after official publication or later and provided acknowledgement is given to the original source of publication and a link is inserted to the published article on Springer's website. The link must be accompanied by the following text: "The final publication is available at link.springer.com".

Clay-rich sediments injected into clastic dykes during earthquakes in the Galera fault zone (Guadix-Baza basin, Central Betic Cordillera) CATALINA SANCHEZ-ROA1, JUAN JIMENEZ-MILLAN1*, FERNANDO NIETO2, FRANCISCO J. GARCIA-TORTOSA1, ISABEL ABAD1 AND ROSARIO JIMENEZ-ESPINOSA1 1Department of Geology and CEACTierra, Associated Unit IACT (CSIC-UGR), Faculty of Experimental Science, University of Jaén, Campus Las Lagunillas s/n, 23071 Jaén, Spain (catasroa@ujaen.es; *correspondence: jmillan@ujaen.es; gtortosa@ujaen.es; miabad@ujaen.es, respino@ujaen.es) 2Department of Mineralogy and Petrology and IACT (CSICUGR), Faculty of Science, University of Granada, Avda. Fuentenueva s/n 18002, Granada, Spain (nieto@ugr.es)

This study was conducted to determine the effects of the waste-rock dump (WRD) of the underground polymetallic Balya Mine on the Kocacay River and eventually on Lake Manyas in Turkey. Data presented in this paper include geochemical characteristics of various kinds of water (mine, surface and groundwater) and of suspendedparticle samples in the vicinity of Balya. The more polluted mine waters have low pH and high conductivity, while high concentrations of Zn, Cd, Mn tend to be found in the dry and wet seasons. High concentrations of Pb, As, Cr, Cu and S appear only in the wet season. The sources of the heavy metal concentration within the Kocacay River are leached waste, surface run off, and overflow from the spillway of the WRD. To minimize the formation of acids and dissolved metal, and for the remediation of the harmful effects of extreme contamination conditions, it is recommended that lime or alkali materials and organic carbon be added to simulate the action of sulfate-reducing bacteria. Keywords Balya Mine AE Waste rock dump (WRD) AE Heavy metals AE Suspended particles AE Acid mine drainage (AMD)

The banded iron formation deposited during the first 2 billion years of Earth's history holds the key to understanding the interplay between the geosphere and the early biosphere at large geological timescales. The earliest ore-scale phosphorite depositions formed almost at~2.0-2.2 billion years ago bear evidence for the earliest bloom of aerobic life. The cycling of nutrient phosphorus and how it constrained primary productivity in the anaerobic world of Archean-Palaeoproterozoic eons are still open questions. The controversy centers about whether the precipitation of ultrafine ferric oxyhydroxide due to the microbial Fe(II) oxidation in oceans earlier than 1.9 billion years substantially sequestrated phosphate, and whether this process significantly limited the primary productivity of the early biosphere. In this study, we report apatite radial flowers of a few micrometers in the 2728 million-year-old Abitibi banded iron formation and the 2460 million-year-old Kuruman banded iron formation and their similarities to those in the 535 million-year-old Lower Cambrian phosphorite. The lithology of the 535 Million-year-old phosphorite as a biosignature bears abundant biomarkers that reveal the possible similar biogeochemical cycling of phosphorus in the Later Archean and Palaeoproterozoic oceans. These apatite radial flowers represent the primary precipitation of phosphate derived from the phytoplankton blooms in the euphotic zones of Neoarchean and Palaoeproterozoic oceans. The unbiased distributions of the apatite radial flowers within sub-millimeter bands do not support the idea of an Archean Crisis of Phosphate. This is the first report of the microbial mediated mineralization of phosphorus before the Great Oxidation Event when the whole biosphere was still dominated by anaerobic microorganisms.

The heavy metals and metalloids released by the oil refineries accumulated in the natural lakes may severely endanger the aquatic life. For this purpose the present study was carried out to explore the potential risk posed by the heavy metals and metalloids in the drainage ditch of a large oil refinery located at the southwest of Lake

Four en-echelon northeast-trending structures, including southeastdipping monoclines and northwest-dipping high-angle reverse faults, have been mapped along the inner edge of the Coastal Plain in northeastern Virginia an area generally considered to be undeformed. Although displacements are small (15 to 60 m), the structures markedly affect the present distribution and thickness of Coastal Plain strata. Structure contour maps on Cretaceous and Paleocene lithostratigraphic units show that the amount of displacement on the structures increases downward, indicating recurrent movement. The major deformation occurred in the Cretaceous and middle (?) Tertiary but some movement in the latest Tertiary or Quaternary is possible. The structures, herein named the Stafford fault system, extend for at least 56 kilometers parallel to the Fall Line and the northeasttrending reach of the Potomac estuary. This relationship supports the hypothesis that the Fall Line and major river deflections along it have been tectonically influenced.

Mineralogical characterization by X-ray diffraction (XRD) and a high throughput automated quantitative evaluation of minerals by scanning electron microscopy (QEMSCAN) was conducted on samples from a sulphate-reducing biochemical reactor (BCR) treating high concentrations of metals (As, Zn, Cu) in smelter waste landfill seepage. The samples were also subjected to energy dispersive X-ray (EDX) analysis of specific particles. The bulk analysis results revealed that the samples consisted mainly of silicate and carbonate minerals. More detailed phase analysis indicated four different classes: zinc-arsenic sulphosalts/sulphates, zinc-arsenic oxides, zinc phosphates and zinc-lead sulphosalts/sulphates. This suggests that sulphates and sulphides are the predominant types of Zn and As minerals formed in the BCR. Sphalerite (ZnS) was a common mineral observed in many of the samples. In addition, X-ray point analysis showed evidence of As and Zn coating around feldspar and amphibole particles. The presence of arsenic-zinc-iron, with or without cadmium particles, indicated arsenopyrite minerals. Copper-iron-sulphide particles suggested chalcopyrite (CuFeS 2) and tennantite (Cu,Fe) 12 As 4 S 13. Microbial communities found in each sample were correlated with metal content to describe taxonomic groups associated with high-metal samples. The research results highlight mineral grains that were present or formed at the site that might be the predominant forms of immobilized arsenic, zinc and copper.

Mineralogical characterization by X-ray diffraction (XRD) and a high throughput automated quantitative evaluation of minerals by scanning electron microscopy (QEMSCAN) was conducted on samples from a sulphate-reducing biochemical reactor (BCR) treating high concentrations of metals (As, Zn, Cu) in smelter waste landfill seepage. The samples were also subjected to energy dispersive X-ray (EDX) analysis of specific particles. The bulk analysis results revealed that the samples consisted mainly of silicate and carbonate minerals. More detailed phase analysis indicated four different classes: zinc-arsenic sulphosalts/sulphates, zinc-arsenic oxides, zinc phosphates and zinc-lead sulphosalts/sulphates. This suggests that sulphates and sulphides are the predominant types of Zn and As minerals formed in the BCR. Sphalerite (ZnS) was a common mineral observed in many of the samples. In addition, X-ray point analysis showed evidence of As and Zn coating around feldspar and amphibole particles. The presence of arsenic-zinc-iron, with or without cadmium particles, indicated arsenopyrite minerals. Copper-iron-sulphide particles suggested chalcopyrite (CuFeS 2) and tennantite (Cu,Fe) 12 As 4 S 13. Microbial communities found in each sample were correlated with metal content to describe taxonomic groups associated with high-metal samples. The research results highlight mineral grains that were present or formed at the site that might be the predominant forms of immobilized arsenic, zinc and copper.

One hundred and fifty years of mineral extraction throughout the mountainous Ruby Creek watershed, Washington has left a legacy of historical hard rock mines and placer claims and their wastes. We conducted a watershed-scale chemical analysis of these gold-bearing tributaries, accounting for seasonal variability in streamflow, to identify spatial and temporal changes in stream chemistry and attribute them to natural processes or mining activities. We used hierarchical cluster analysis (HCA) to group chemically similar water samples based on concentrations of 23 metals, pH, and conductivity and compared the chemistry of HCAgenerated clusters of water samples using pairwise comparisons to find chemical patterns. Total concentrations of As, Ba, Ca, Mg, Na, Sb, and Se, dissolved concentrations of Fe, and conductivity increased as streamflow progressed from snowmelt-influenced to baseflow. High total concentrations of Al, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Sb, V, and Zn during spring snowmelt and after rains were attributable to acid mine drainage at historical hard rock mines and prospect sites. Smaller-scale placer mining, by way of suction dredging and motorized gold panning, was associated with high concentrations of Al,

One hundred and fifty years of mineral extraction throughout the mountainous Ruby Creek watershed, Washington has left a legacy of historical hard rock mines and placer claims and their wastes. We conducted a watershed-scale chemical analysis of these gold-bearing tributaries, accounting for seasonal variability in streamflow, to identify spatial and temporal changes in stream chemistry and attribute them to natural processes or mining activities. We used hierarchical cluster analysis (HCA) to group chemically similar water samples based on concentrations of 23 metals, pH, and conductivity and compared the chemistry of HCAgenerated clusters of water samples using pairwise comparisons to find chemical patterns. Total concentrations of As, Ba, Ca, Mg, Na, Sb, and Se, dissolved concentrations of Fe, and conductivity increased as streamflow progressed from snowmelt-influenced to baseflow. High total concentrations of Al, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Sb, V, and Zn during spring snowmelt and after rains were attributable to acid mine drainage at historical hard rock mines and prospect sites. Smaller-scale placer mining, by way of suction dredging and motorized gold panning, was associated with high concentrations of Al,

Aluminum precipitates control the hydrochemistry and mineralogy of a broad variety of environments on Earth (e.g., acid mine drainage, AMD, coastal wetlands, boreal and alpine streams, tropical acid sulfate soils, laterites and bauxites, …). However, the geochemical and mineralogical processes controlling Al (and other associated metals and metalloids) transport and removal in those environments are not fully understood. The geochemical system of Paradise Portal (Colorado, USA) comprises sulfate-rich mildly acidic waters, the hydrochemistry of which is directly controlled by the massive precipitation of hydrobasaluminite Al 4 (SO 4)(OH) 10 •12-36H 2 O. Three connected but discernible aluminum precipitation stages were identified and described: 1) nanoparticle formation and size decrease along the creek, 2) hydrobasaluminite neoformation on the riverbed, and 3) precipitate accretion and accumulation on the riverbed leading to Al and Fe banded formations. The co-occurrence of Al and Si in the system was observed, recording significant amounts of Si accompanying the three different components of the system (i.e., nanoparticles and fresh and aged Al-precipitates). Also, abrupt and minor changes in the sedimentary record were described and proposed to be the response of the system to seasonal and interannual changes in AMD chemistry. Concerning the mobility of other metals and metalloids, P, Th, V, W, Ti and B showed a tendency to be preferentially incorporated into hydrobasaluminite, while others like Be, As, Se or Ba tend to remain dissolved in the water.

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 (FeS 2) 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 generation of acidic drainage has become pervasive over the years and toxic elements are released due to exposure to oxidising agents, unforeseen circumstances, and human interactions. Uncontrolled acidic mine drainage release can result in substantial ecological disruption in sensitive and productive receiving waters. This study probes the element mobility of gold tailings with regard to various zones identified, based on possible phenomena such as the natural water medium, or acidic and alkaline media using sequential extraction and multivariate analyses. Factor analysis results, coupled with mineralogy, were corroborated with acid generation potential to identify various relationships that exist and establish the efficacy of the research towards predicting acid mine drainage generation potential. The statistical analysis was able to establish that pH or acidity, Fe ions, Ca 2+ and Mg 2+ played a major role in the released metals. Out of the four factors (80.8% accounted for) identified in factor analysis results for water fraction (WF), Fe contributed to three factors which showed the presence of Fe ions (assuming Fe 2+ and Fe 3+) responsible for the increased acidity of the tailings. The net acid producing potential and cumulative net acid producing potential showed that overall; the tailings would generate acidity due to the high presence of leachable sulphides. The trends observed in the carbonate phase indicated that despite the posit of acidity, the tailings contain a considerable amount of neutralising agent to serve as a buffer.

A sampling protocol for the retention, extraction, and analysis of sulfoxyanions in hydrothermal waters has been developed in the laboratory and tested at Yellowstone National Park and Green Lake, NY. Initial laboratory testing of the anion-exchange resin Bio-Rad 2 AG1-X8 indicated that the resin was well suited for the sampling, preservation, and extraction of sulfate and thiosulfate. Synthetic solutions containing sulfate and thiosulfate were passed through AG1-X8 resin columns and eluted with 1 and 3 M KCl, respectively. Recovery ranged from 89 to 100%. Comparison of results for water samples collected from five pools in Yellowstone National Park between on-site IC analysis (U.S. Geological Survey mobile lab) and IC analysis of resin-stored sample at SUNY-Stony Brook indicates 96 to 100% agreement for three pools (Cinder, Cistern, and an unnamed pool near Cistern) and 76 and 63% agreement for two pools (Sulfur Dust and Frying Pan). Attempts to extract polythionates from the AG1-X8 resin were made using HCl solutions, but were unsuccessful. Bio-Rad 2 AG2-X8, an anion-exchange resin with weaker binding sites than the AG1-X8 resin, is better suited for polythionate extraction. Sulfate and thiosulfate extraction with this resin has been accomplished with KCl solutions of 0.1 and 0.5 M, respectively. Trithionate and tetrathionate can be extracted with 4 M KCl. Higher polythionates can be extracted with 9 M hydrochloric acid. Polythionate concentrations can then be determined directly using ion chromatographic methods, and laboratory results indicate recovery of up to 90% for synthetic polythionate solutions using AG2-X8 resin columns.

Fluviomarine areas are promising for development of new paddy fields if fragile soil properties, natural water logging and tidal behaviors receive strategic management to avoid environmental degradation. Three transects were established to investigate the complexity of sediment and tidal attributes. Soils were sampled from each horizon of profiles and key mineralogical and chemical properties analyzed. An upper fluvial derived zone was characterized by exchangeable Ca as the dominant cation (decreasing concentration with depth) and pyrite was absent. A lower zone derived from marine sediment was dominated by exchangeable Mg (increasing concentration with depth) accompanied by pyrite. The dominance and distribution of Ca and Mg indicate the origin of sediment in tidal areas. These acid sulfate soils have limited nutrient reserves being dominated by quartz in the sand fraction. The clay was dominated by kaolinite and illite and a variable proportion of vermiculite, resulting in variation of CEC values, being high with vermiculite. Pyrite position from soil surface varied from 25 to 100 cm (mostly 50-60 cm) depending on thickness of fluvial zone and local slope morphology. Significant variations in tidal amplitudes led to the separation of fluviomarine areas into neap-spring tide zone (NSZ), spring tide zone (SZ) and non-flooding tide zone (NZ). Zoning allowed the selection of the SZ with low tidal amplitude and NZ as being suitable for new paddy field development. A potential drop of soil pH from 5 to 2 may occur with serious consequences for paddy field and watercourses (huge acidity and dissolved metals at toxic levels) if pyrite is exposed to oxidation conditions (e.g. drainage system lowering water level below pyrite position). Water management through "controlled drainage" should be applied to avoid pyrite oxidation, soil degradation and poor water quality. This includes dimension (depth and width) of drainage canals and maintaining water levels above the pyrite zone through control using floodgates thereby ensuring pyrite zone remains under reducing conditions.

The use of paste tailings is considered as a potentially advantageous alternative to conventional slurry tailings disposal, especially in areas where water resources are scarce. In order to assess the response of a paste tailings storage facility, one needs to analyse the near-surface moisture fluxes in the exposed tailings due to evaporation and drainage. In the case of sulphide bearing materials with an acid mine drainage (AMD) generating potential, it is important to evaluate the impact of desaturation that may lead to tailings weathering, i.e. oxidation. A key factor influencing production of AMD is the distribution of the pore water within the tailings. This paper presents sample results from laboratory testing and numerical simulations that are being conducted to evaluate pore water movements in surface paste tailings. The study focuses primarily on columns tests made with paste tailings from Barrick Gold's Bulyanhulu Mine (Tanzania, Africa). These tests have been used to assess the evolution of paste tailings behaviour and their reactivity at the laboratory scale, with the help of numerical simulations. The oxidation rate is also investigated for different situations pertaining to the column tests results. The numerical simulations presented are a one-dimensional simplification of the tailings storage facility of Bulyanhulu Mine, and evaluate the impact of evaporation on the water balance of paste tailings deposited on surface. The main observations indicate that the oxidation of exposed reactive tailings is influenced by their degree of saturation and the evaporation plays an important role in the water balance of paste tailings exposed to near surface conditions.

Laboratory column experiments and numerical simulations are used to evaluate the effectiveness of an elevated water table as a management and reclamation method for acid-generating mine tailings. The laboratory experiments involved monitoring oxygen and effluent chemistry from several columns of mine tailings with different water table elevations. Each column contained a layer of reactive tailings overlain by a sand cover and was subjected to transient recharge and flushing in fourteen 30-70 day cycles for 502 days. A free-draining control column with no sand cover was also used. The experimental results were compared with numerical simulations using the fully coupled reactive transport model MIN3P, which included infiltration, saturation-dependent oxygen diffusion, pyrite oxidation, multi-component geochemical reactions, and mineral buffering. The numerical results were consistent with the observed data which showed that an elevated water table can be very effective in reducing the production of acid mine drainage.

The efficiency of a monolayer cover to prevent acid mine drainage (AMD) generation from two preoxidized tailings impoundments was assessed using the MIN3P code, a finite volume model for coupled groundwater flow, oxygen diffusion and multi-component reactive transport. Numerical simulations were validated using large column tests set up in the laboratory and monitored during 19 wetting and drying cycles, over approximately two years. Results indicate that a monolayer cover made of either non acid-generating tailings or a till was not able to prevent sulfide oxidation in the underlying reactive tailings, both for the conditions applied in the laboratory and under conditions more representative of field observations. The efficiency of the simulated monolayer cover was highly dependent on the position of the water table. Despite improved water quality, the reactive tailings nonetheless continued to oxidize and generate AMD, even when the water table was close to the surface of the tailings (1 m depth). The results from this study indicate that the efficiency criteria for cover systems on fresh unoxidized tailings may not be directly applicable for pre-oxidized tailings. The paper also presents a few modifications to the MIN3P code that were successfully applied to simulate the hydrogeological and geochemical response of pre-oxidized, already acidic and highly contaminated tailings.

The current research was conducted to assess the groundwater quality in the Patancheruvu area of Sangareddy District, South India. To analysis physicochemical parameters, 16 groundwater samples were collected for the month of May and November, 2020. The chemical analysis results show that the ground water nature in the study area is alkaline to basic and is classified very hard water. High TDS concentrations in the study area is due to various industries and anthropogenic activities. In both seasons, the order of major cations and major anions is in the following order: Na > Mg > Ca > K and Cl > SO 4 > HCO 3 > NO 3 > F respectively. The majority of the EC, TDS, Na, TH, Mg, Ca, Cl, HCO 3 , and SO 4 samples exceeded the desirable limit, and some samples also exceeding the permissible limit. In both seasons, the dominant hydro chemical facies identified by the Chadha diagram were Na-K-HCO 3 and Ca-Mg-HCO 3. Water quality analysis said that most of the data in both seasons fell into poor to very poor category. The research tells that around Patancheruvu groundwater quality is poor, thisis attributed due to both anthropogenic factors and geogenic processes.