Metal-mining exploitation has caused ecosystem degradation worldwide. Legacy wastes are often concentrated around former mines where monitoring and research works are mostly focused. Geochemical and physical weathering can affect metal-enriched sediment locations and their capacity to release metals at a catchment scale. This study investigated how fluvial geomorphology and soil geochemistry drive zinc and lead dispersion along the Nant Cwmnewyddion (Wales, UK). Sediments from different locations were sampled for geochemical and mineralogical investigations (portable X-ray fluorescence, scanning electron microscope, X-ray diffraction, and electron microprobe analysis). The suspended sediment fluxes in the streamwater were estimated at different streamflows to quantify the metal dispersion. Topographical and slope analysis allowed us to link sediment erosion with the exposure of primary sulphide minerals in the headwater. Zinc and lead entered the streamwater as aqueous phases or as suspended sediments. Secondary sources were localised in depositional stream areas due to topographical obstruction and a decrease in stream gradient. Sediment zinc and lead concentrations were lower in depositional areas and associated with Fe-oxide or phyllosilicates. Streamwater zinc and lead fluxes highlighted their mobility under high-flow conditions. This multi-disciplinary approach stressed the impact of the headwater mining work on the downstream catchment and provided a low-cost strategy to target sediment sampling via geomorphological observations.

An estimated 23 million people live on floodplains affected by potentially dangerous concentrations of toxic waste derived from past and present metal mining activity. We analyzed the global dimensions of this hazard, particularly in regard to lead, zinc, copper, and arsenic, using a georeferenced global database detailing all known metal mining sites and intact and failed tailings storage facilities. We then used process-based and empirically tested modeling to produce a global assessment of metal mining contamination in river systems and the numbers of human populations and livestock exposed. Worldwide, metal mines affect 479,200 kilometers of river channels and 164,000 square kilometers of floodplains. The number of people exposed to contamination sourced from long-term discharge of mining waste into rivers is almost 50 times greater than the number directly affected by tailings dam failures.

Abstract
. Rozenite (FeSO4·4H2O) is a candidate mineral component of the polyhydrated sulfate deposits on the surface and in the subsurface of Mars. To better understand its behavior at temperature conditions prevailing on the Martian surface and aid its identification in ongoing and future Rover missions, we have carried out a combined experimental and computational study of the mineral’s structure and properties. We collected neutron powder diffraction data at temperatures ranging from 21–290 K, room-temperature synchrotron X-ray data and Raman spectra. Moreover, first-principles calculations of the vibrational properties of rozenite were carried out to aid the interpretation of the Raman spectra. We found, in contrast to a recent Raman spectroscopic study, that there are no phase transitions between 21 and 290 K. We confirm the heavy atom structure reported in the literature (space group P21/n) to be correct and present, for the first time, an unconstrained determination of the H atom positions by means of high-resolution neutron powder diffraction, and report the complete crystal structure at 290 and 21 K. The anisotropy of the thermal expansion of the lattice vectors is αa:αb:αc = 1.00:2.19:1.60 at 285 K. Subsequent analysis of the thermal expansion tensor revealed highly anisotropic behavior as reflected in negative thermal expansion approximately ||⟨101⟩ and ratios of the tensor eigenvalues of α1:α2:α3 = −1:3.74:5.40 at 285 K. Lastly, we demonstrated how combining Raman spectroscopy and X-ray diffraction of the same sample sealed inside a capillary with complementary first-principles calculations yields accurate reference Raman spectra. This workflow enables the construction of a reliable Raman spectroscopic database for planetary exploration, which will be invaluable to shed light on the geological past as well as in identifying resources for the future colonization of planetary bodies throughout the solar system.

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The jarosite family of minerals are part of the alunite supergroup with the general formula AB3(TO4)2(OH)6. Jarosite family minerals are known to incorporate silver (Ag), but the extent to which this occurs, and at what temperature range, is not well constrained. To address this knowledge gap, jarosite compounds with the a site filled with K, Na, Ag and H3O were synthesised at 22 °C, 97 °C and 140 °C to simulate low-, moderate- and high-temperature environments, respectively. The compounds were characterised by XRD, SEM, chemical analysis and Raman spectroscopy. All of the synthesised compounds took up Ag. In general, higher temperatures of synthesis increased alkali and Ag occupancy of the a site of the products. Silver contents increased with the increasing concentration of Ag in the starting solutions at all temperatures. The order of preference for occupancy of the a site in the synthesised solids is K > Na > H3O > Ag at all temperatures, which is consistent with the reported order of ΔGf of −3309 kJ/mol, −3270 kJ/mol, −3247 kJ/mol and −2948 kJ/mol for jarosite, natrojarosite, hydroniumjarosite and argentojarosite, respectively. The results of this study show that Ag can be incorporated in jarosite and natrojarosite at low-to-high temperatures, and therefore, jarosite family minerals can be important stores of Ag in in natural and engineered environments.

Globally, many mines emit acid mine drainage (AMD) during and after their operational life cycle. AMD can affect large and often inaccessible areas. This leads to expensive monitoring via conventional ground-based sampling. Recent advances in remote sensing which are both non-intrusive and less time-consuming hold the potential to unlock a new paradigm of automated AMD analysis. Herein, we test the feasibility of remote sensing as a standalone tool to map AMD at various spatial resolutions and altitudes in water-impacted mining environments. This was achieved through the same-day collection of satellite-based simulated Sentinel-2 (S2) and PlanetScope (PS2.SD) imagery and drone-based UAV Nano-Hyperspec (UAV) imagery, in tandem with ground-based visible and short-wave infrared analysis. The study site was a historic tin and copper mine in Cornwall, UK. The ground-based data collection took place on the 30 July 2020. Ferric (Fe(III) iron) band ratio (665/560 nm wavelength) was used as an AMD proxy to map AMD pixel distribution. The relationship between remote-sensed Fe(III) iron reflectance values and ground-based Fe(III) iron reflectance values deteriorated as sensor spatial resolution decreased from high-resolution UAV imagery (

The growing global demand for non-ferrous metals has led to serious environmental issues involving uncovered mine site slag dumps that threaten the surrounding soils, surface waters, groundwater, and the atmosphere. Remediation of these slags using substitute cement materials for ordinary Portland cement (OPC) and precursors for alkali-activated materials (AAMs) can convert hazardous solid wastes into valuable construction materials, as well as to attain the desired solidification and stabilization (S/S) of heavy metal(loid)s (HM). This review discusses the current research on the effect of non-ferrous slags on the reaction mechanisms of the OPC and AAM. The S/S of HM from the non-ferrous slags in AAM and OPC is also reviewed. HM can be stabilized in these materials based on the complex salt effect and isomorphic effects. The major challenges faced in AAMs and OPC for HM stabilization include the long-term durability of the matrix (e.g. sulfate attack, stability of volume). The existing knowledge gaps and future trends for the sustainable application of non-ferrous slags are also discussed.

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In 2021, GeoHealth benefited from 365 reviews provided by 241 of our peers

A number of individuals submitted multiple reviews for GeoHealth in 2021

Seismic studies are essential for accurate characterisation of planetary interior structures, but are dependent on modelling for interpretation, requiring data on the elastic properties of likely constituent minerals. With the potential deployment of seismic stations on icy worlds such as Europa and Titan envisioned for the near future, a campaign of study into the elasticity of potential icy ocean world minerals is of paramount importance. In the paper we assess the role of first-principles computer simulations to this problem, in particular focussing on the application of recent advances in simulating dispersion forces in loosely-bonded molecular solids, likely to be the main constituents of icy ocean worlds. This is of particular interest for these kinds of materials, since the complex sample handling, phase transitions and the difficulty of obtaining single crystals often greatly complicates the experimental determination of the full elastic tensor. We focus on CO2, C6H6, MgSO4·7H2O and CaSO4·2H2O as they allow us to benchmark the performance over a wide range of chemical space, structural topologies, crystal symmetries and bonding types, and moreover have accurate experimentally determined unit-cell dimensions, bulk moduli and full elastic tensors for benchmarking purposes. We demonstrate that the dispersion corrected approaches indeed perform better in modelling the experimental density profiles (mean unsigned differences of only 0.04 g/cm3 (CO2), 0.02 g/cm3 (C6H6), 0.003 g/cm3 (MgSO4·7H2O) and 0.013 g/cm3 (CaSO4·2H2O)) and may find application in exploring the compressive parameters of candidate materials, which could then be used in rheological models of icy ocean worlds. Moreover, we have assessed if the elastic constants computed by dispersion corrected density functional theory are accurate enough to be used in a reference data base for the seismic exploration of icy ocean worlds. Despite one approach having demonstrated good accuracy compared with the experimental values in modelling the elasticity of CO2, we instead find average differences from expected P and S wave velocities of around 10 to 25% for the elastically more complex title compounds. In part these differences are due to the large temperature difference between the experimental elasticity data (typically near 300 K) and our calculations, which were performed in the athermal limit.

Mine tailings sites are considered as a continuous source of discharged metal(loid)s and residual organic flotation reagents. They are extremely toxic environments representing unique ecological niches for microbial communities. Mine tailings as a source of multi-resistance genes have been poorly investigated. Metagenomic analysis for four active nonferrous metal(loid) tailings sites with different environmental parameters was conducted. The abundance of Thiobacillus, able to tolerate acidity and showing iron- and sulfur/sulfide oxidation capacities, was significantly different (p < 0.05) between acid and neutral tailings sites. Correlation analyses showed that Zn, Pb, TP, Cd, and Cu were the main drivers influencing the bacterial compositions. Multi-metal resistance genes (MRGs) and antibiotic resistance genes (ARGs), such as baca and copA, were found to be co-selected by high concentrations of metal(loid)s tailings. The main contributors to different distributions of MRGs were Thiobacillus and Nocardioides genus, while genera with low abundance (

To determine the status and sources of contamination and phytoremediation capability of Typha latifolia L. in the Bahmanshir River of Iran, the concentration of eight potentially toxic elements (As, Cd, Cr, Cu, Mn, Ni, Pb, and Zn) in sediment and plant tissues from ten sampling sites were measured. Mean concentrations of Cd, Cr, Cu, Pb, and Zn in the sediment exceeded those of local background. PCA-MLR receptor analysis suggested that the sediment contamination was due to municipal wastewater/vehicular pollution and weathering/industrial/agricultural activities, with contributions of 66% and 34%, respectively. Average enrichment factor (EF) and modified hazard quotient (mHQ) for Pb and Cu were categorized as moderate. Modified pollution index (MPI) and modified ecological risk index (MRI) values suggested moderate to heavy pollution and low ecological risk, respectively. The values of sediment quality guidelines (SQGs), ecological contamination index (ECI), contamination severity index (CSI), and toxic risk index (TRI) were all similar, reflecting low to moderate contamination and toxicity. Typha latifolia L. showed good phytostabilization capability for Cd, Cu, and Pb, and phytoextraction capacity for Zn. Using the metal accumulation index (MAI) and the comprehensive bioconcentration index (CBCI), Typha latifolia L. was shown to have acceptable performance in the accumulation of Cd, Cu, Pb, and Zn and thus, can be considered a good candidate for bioaccumulation of these elements in the study area. Overall, this study suggests that phytoremediation using Typha latifolia L. could be a practical method for uptake and remove of potentially toxic elements from aquatic environments.

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Cobalt is recognised by the European Commission as a “Critical Raw Material” due to its irreplaceable functionality in many types of modern technology, combined with its current high-risk status associated with its supply. Despite such importance, there remain major knowledge gaps with regard to the geochemistry, mineralogy, and microbiology of cobalt-bearing environments, particularly those associated with ore deposits and subsequent mining operations. In such environments, high concentrations of Co (up to 34,400 mg/L in mine water, 14,165 mg/kg in tailings, 21,134 mg/kg in soils, and 18,434 mg/kg in stream sediments) have been documented. Co is contained in ore and mine waste in a wide variety of primary (e.g. cobaltite, carrolite, and erythrite) and secondary (e.g. erythrite, heterogenite) minerals. When exposed to low pH conditions, a number of such minerals are known to undergo dissolution, typically forming Co2+(aq). At circumneutral pH, such aqueous Co can then become immobilised by co-precipitation and/or sorption onto Fe and Mn(oxyhydr)oxides. This paper brings together contemporary knowledge on such Co cycling across different mining environments. Further research is required to gain a truly robust understanding of the Co-system in mining-affected environments. Key knowledge gaps include the mechanics and kinetics of secondary Co-bearing mineral environmental transformation, the extent at which such environmental cycling is facilitated by microbial activity, the nature of Co speciation across different Eh-pH conditions, and the environmental and human toxicity of Co.

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The editors thank the 2019 peer reviewers

AbstractPublic trust in science, effective science communication, and rapid and constructive response to authors about their submissions are of paramount importance to the scientific enterprise and indeed to society itself. This is really at the heart of peer review—providing thoughtful insights into both the scientific quality and importance of work, and also how it is communicated to other scientists and increasingly to a broader audience. Very few opportunities exist to acknowledge the mostly anonymous process of peer review, especially given the huge increase in review requests and the relatively mechanical nature of online reviewing platforms. We continue to be humbled by the time, effort, and careful insights that our colleagues share with each other through the process of peer review. In 2018, GeoHealth benefited from more than 83 reviews provided by 53 of our peers for papers submitted to the journal. Thank you all for your awesome efforts toward advancing geohealth now and for the future.

Dissolved Mn(III) has been identified at all stages throughout a Water Treatment Works (WTW) receiving inflow from a peaty upland catchment in NE England. Ninety percent of the influent total manganese into the WTW is particulate Mn, in the form of Mn oxide (>0.2 μm). Approximately 9% (mean value, n = 22, range of 0–100%) of the dissolved (

The ability of a Fe-Mn binary oxide waste to adsorb arsenic (As) in a historically contaminated soil was investigated. Initial laboratory sorption experiments indicated that arsenite [As(III)] was oxidized to arsenate [As(V)] by the Mn oxide component, with concurrent As(V) sorption to the Fe oxide. The binary oxide waste had As(III) and As(V) adsorption capacities of 70 mg g−1 and 32 mg g−1 respectively. X-ray Absorption Near-Edge Structure and Extended X-ray Absorption Fine Structure at the As K-edge confirmed that all binary oxide waste surface complexes were As(V) sorbed by mononuclear bidentate corner-sharing, with 2 Fe at ∼3.27 Ǻ. The ability of the waste to perform this coupled oxidation-sorption reaction in real soils was investigated with a 10% by weight addition of the waste to an industrially As contaminated soil. Electron probe microanalysis showed As accumulation onto the Fe oxide component of the binary oxide waste, which had no As innately. The bioaccessibility of As was also significantly reduced by 7.80% (p < 0.01) with binary oxide waste addition. The results indicate that Fe-Mn binary oxide wastes could provide a potential in situ remediation strategy for As and Pb immobilization in contaminated soils.

Assessing water sources for drinking and irrigation along with community vulnerability, especially in developing and rural regions, is important for reducing risk posed by poor water quality and limited water availability and accessibility. We present a case study of rural mining-agricultural communities in the Lake Poopó Basin, one of the poorest regions on the Bolivian Altiplano. Here, relatively low rainfall, high evaporation, salinization and unregulated mining activity have contributed to environmental degradation and water issues, which is a situation facing many Altiplano communities. Social data from 72 households and chemical water quality data from 27 surface water and groundwater sites obtained between August 2013 and July 2014 were used to develop locally relevant vulnerability assessment methodologies and ratings with respect to water availability and quality, and Chemical Water Quality Hazard Ratings to assess water quality status. Levels of natural and mining-related contamination in many waters (CWQHR ≥ 6; 78% of assessed sites) mean that effective remediation would be challenging and require substantial investment. Although waters of fair to good chemical quality (CWQHR ≤ 5; 22% of assessed sites) do exist, treatment may still be required depending on use, and access issues remain problematic. There is a need to comply with water quality legislation, improve and maintain basic water supply and storage infrastructure, build and operate water and wastewater treatment plants, and adequately and safely contain and treat mine waste. This study serves as a framework that could be used elsewhere for assessing and mitigating water contamination and availability affecting vulnerable populations.

The iron-reducing bacterium Acidiphilium cryputum JF-5 and a sulfate reducing bacterium (SRB) collected and purified from the mine drainage of a copper mine in the northwest of Sichuan Province, China, were used to biologically synthesize nano-sized FeS-coated limestone to remove As(V) from solution. The adsorption efficiency of As(V) is improved from 6.64 μg/g with limestone alone to 187 μg/g with the FeS coated limestone in both batch and column experiments. The hydraulic conductivity of the columns are also improved by the presence of the nano-sized FeS coatings, but the solution neutralization performance of the limestone can be reduced by passivation by gypsum and Fe(III) precipitates. Calculations for FeS-coated limestone dissolution experiments show that the process can be described as nCa.sol = At1/2 − nCa,gyp. The results suggest that FeS-coated limestone may be an effective medium for remediating As(V)-bearing solutions such as acid mine drainage in systems such as Permeable Reactive Barriers.

Minerals are naturally occurring inorganic solids that make up the solid part of most solar terrestrial planets. Redox-active elements such as iron, manganese, titanium and sulfur, in these minerals allow them to engage in a wide range of electron-transfer reactions including those mediated by biota or processes involved in palaeo-weathering and biogeochemical cycling. The importance of redox-reactive minerals in many natural and industrial processes has been demonstrated by a plethora of scientific publications and industrial applications in recent decades. In this book, the influence of redox-reactive minerals on key biogeochemical processes and opportunities for their application in environmental technologies are outlined and illustrated in 14 comprehensive chapters. The book will be a key reference for Earth science students, geologists, geochemists and engineers and other researchers and practitioners in this rapidly growing interdisciplinary field.

We have grown single crystals of M2+SO4 hydrates at 270 K from aqueous solutions in the ternary systems CoSO4–MgSO4–H2O and MnSO4–MgSO4–H2O. These systems exhibit broad stability fields for a triclinic undecahydrate on the Mg-rich side (i.e. Co- or Mn-bearing meridianiite solid solutions) and stability fields for monoclinic heptahydrates on the Mg-poor side (i.e. Mg-bearing solid solutions of bieberite or mallardite). The solubility curves and distribution coefficients, describing the partitioning of M2+ ions between liquid and solid phases, have been determined by thermo-gravimetric and spectroscopic techniques. A subset of M2+SO4·11H2O specimens were selected for single-crystal time-of-flight neutron diffraction analysis in order to evaluate preferential occupancy of symmetry-inequivalent coordination polyhedra in the structure. Considering the nearly identical dimensions of the first coordination shells, there is a surprising difference in the distribution of Co and Mn over the two available sites.

Mining, oil and gas and other extractive industries are vital and irreplaceable constituents of the modern global economy. The overall demand for the products of these industries rises inexorably with economic growth and developing prosperity. However, these industries produce vast quantities of potentially harmful waste. Many of the elemental, and hence mineralogical, components of the waste stream are redox active. This review focuses on redox-reactive minerals sourced from this waste stream in reuse and remediation schemes. Copper-, manganese- and iron-bearing mine wastes are used as pigments, in fertilizers, sorbents of toxic compounds in water treatment systems, and for the production of SO2 and H2SO4. Some solid mine wastes can be remediated by phytostabilization, where plants are used to induce the precipitation of secondary redoxreactive minerals that sequester contaminants. Liquid wastes are remediated using a variety of abiotic and biotically-assisted schemes such as anoxic limestone drainages and permeable reactive barriers. These schemes use phases such as zero-valent iron and Feoxyhydroxides, and produce mineralogical by-products such as sulfides, green rust and oxyhydroxides. Further research is needed to optimize the reuse and remediation schemes in mine wastes and to develop new and innovative systems employing redox active minerals.

Purpose: Chromium, a potentially harmful element, occurs commonly within the urban sediment cascade as a result of abundant industrial and transport-related sources. The risks that Cr-bearing particles pose to ecosystems and humans depend on the solid-phase chemical speciation of Cr and its environmental mobility. In this study, we adopt an integrated geochemical approach to investigate and determine the long-term fate of Cr in the urban sediment cascade. Materials and methods: We use bulk chemical digests, sequential chemical extraction analysis, electron microscopy, electron microprobe and microfocus XANES analysis to describe the solid-phase speciation, geochemical characteristics and potential long-term behaviour of Cr in urban particulate matter from both aquatic sediment and road dust sediment (RDS) in Manchester, UK. Results and discussion: Cr-bearing grains within RDS and aquatic sediment are predominantly iron oxides and alumino-silicate glass grains. Electron microprobe analysis indicates Cr concentrations up to 3300 and 133,400 μg g−1 in the RDS and aquatic grains, respectively. XANES analysis indicates that Cr(III) is the dominant oxidation state, with only trace amounts of Cr(VI). Importantly, Cr speciation does not appear to have changed between sedimentary environments and the dominance of Cr(III) suggests limited bioavailability or toxicity under predominant environmental (anoxic and neutral pH) conditions in the aquatic sediment sink. Furthermore, geochemical analyses suggest the environmental mobility of Cr in the aquatic sediment sink is low (compared to other toxic metals) due to its association mainly with alumino-silicate glass grains and its inclusion as an integral part of the glass structure. Conclusions: Industrial glass grains are a major component of urban sediment worldwide. The speciation and geochemical investigations performed in this study suggest most Cr within the urban sediment cascade may be resistant to environmental processes that could mobilise other toxic metals.

Future climate change is likely to pose significant challenges for heritage management, especially in landscape settings, such as river valleys as the magnitude, intensity and nature of geomorphological processes alter in response to changing threshold conditions. Industrial landscapes afford particular challenges for the heritage community, not only because the location of these historic remains is often intimately linked to the physical environment, but also because these landscapes can be heavily polluted by former (industrial) processes and, if released, the legacy of contaminants trapped in floodplain soils and sediments can exacerbate erosion and denudation. Responding to these challenges requires the development of methodologies that consider landscape change beyond individual sites and monuments and this paper reports the development of such an approach based on investigation of the Derwent Valley Mills World Heritage Site, Derbyshire, UK. Information on geomorphological evolution of the Derwent Valley over the last 1000 years, a time period encompassing the last two periods of major climatic deterioration, the Medieval Warm Period and Little Ice Age, has been dovetailed with archaeological and geochemical records to assess how the landscape has evolved to past landscape change. However, in addition to assessing past evolution, this methodology uses national climate change scenarios to predict future river change using the CAESAR-Lisflood model. Comparison of the results of this model to the spatial distribution of World Heritage Site assets highlights zones on the valley floor where pro-active mitigation might be required. The geomorphological and environmental science communities have long used predictive computer modelling to help understand and manage landscapes and this paper highlights an approach and area of research cross-over that would be beneficial for future heritage management.

Siderophores are biogenic chelating ligands that facilitate the solubilisation of Fe(III) and form stable complexes with a range of contaminant metals and therefore may significantly affect their biogeochemical cycling. Desferrioxamine B (DFOB) is a trihydroxamate siderophore that acts synergistically with fulvic acid and low molecular weight organic ligands to release Fe from Fe(III) oxides. We report the results of batch dissolution experiments in which we determine the rates of Cr(III) desorption and Fe(III) release from Cr(III)-treated synthetic goethite as influenced by DFOB, by fulvic acid, and by the two compounds in combination. We observed that adsorbed Cr(III) at 3% surface coverage significantly reduced Fe(III) release from goethite for all combinations of DFOB and fulvic acid. When DFOB (270 μM) was the only ligand present, dissolved Fe(III) and Cr(III) increased approximately 1000-fold and 16-fold, respectively, as compared to the ligand-free system, a difference we attribute to the slow rate of water exchange of Cr(III). Suwannee River fulvic acid (SRFA) acts synergistically with DFOB by (i) reducing the goethite surface charge leading to increased HDFOB+ surface excess and by (ii) forming aqueous Fe(III)-SRFA species whose Fe(III) is subsequently removed by DFOB to yield aqueous Fe(III)-DFOB complexes. These observations shed new light on the synergistic relationship between DFOB and fulvic acid and reveal the mechanisms of Fe(III) acquisition available to plants and micro-organisms in Cr(III) contaminated environments.

The Derwent Valley Mills World Heritage Site (DVMWHS) exemplifies and records the 18th century birth of the factory or mill technology for the industrial spinning of cotton. The site is therefore a key global heritage asset. The Derbyshire Derwent catchment also contains another significant cultural asset with a long history - that of mining and, in particular, lead (Pb) mining. In this paper research on mining- and non-mining related Pb contamination of the Derwent catchment is reviewed and used to identify the risks it poses to the DVMWHS. The upper Derwent soils, though not impacted by mining, have high sediment-borne Pb concentrations, and the Pb is sourced from local conurbations (principally Manchester) and carried to the upper Derwent on the wind. River sediments in the middle and lower parts of the Derwent catchment are contaminated with Pb mined mainly between the 18th and 19th centuries and before, possibly as far back as the Bronze Age. The potential for large-scale, acidity-related chemical remobilization of this Pb is low in the Derwent catchment due to the largely alkaline nature of the underlying soils, but the potential for oxidation-reduction-related, and physical (flood-related), remobilization, is higher. Management guidelines for mining heritage assets and the DVMWHS are developed from the reviewed information, with the view that these will provide a framework for future work in, and management of, the DVMWHS that will be applicable to other World Heritage Sites affected by ongoing and past metal mining. Focused collaborative work between archaeologists, geochemists, geomorphologists and mineralogists is vital if the risks to the DVMWHS and other similarly-affected World Heritage Sites are to be quantified and, if necessary, mitigated.

Although the removal of arsenic(V) (As(V)) from solution can be improved by forming metal-bearing coatings on solid media, there has been no research to date examining the relationship between the coating and As(V) sorption performance. Manganese-coated bone char samples with varying concentrations of Mn were created to investigate the adsorption and desorption of As(V) using batch and column experiments. Breakthrough curves were obtained by fitting the Convection-Diffusion Equation (CDE), and retardation factors were used to quantify the effects of the Mn coatings on the retention of As(V). Uncoated bone char has a higher retention factor (44.7) than bone char with 0.465 mg/g of Mn (22.0), but bone char samples with between 5.02 mg/g and 14.5 mg/g Mn have significantly higher retention factors (56.8-246). The relationship between retardation factor (Y) and Mn concentration (X) is Y = 15.1 X + 19.8. Between 0.2% and 0.6% of the sorbed As is desorbed from the Mn-coated bone char at an initial pH value of 4, compared to 30% from the uncoated bone char. The ability of the Mn-coated bone char to neutralize solutions increases with increased amounts of Mn on the char. The results suggest that using Mn-coated bone char in Permeable Reactive Barriers would be an effective method for remediating As(V)-bearing solutions such as acid mine drainage.

Currently, the evaluation of sediment storage and transport for large river systems with variable flow has proven to be a challenge that often requires complex numerical models to be applied and sometimes costly direct data acquisition to be made. The present study proposes a low cost, widely available GIS-based method through which an initial assessment can be made on areas of sediment storage, transport and deposition as well as possible environmental risks that the accumulation of contaminated material may pose to riverine communities along the rivers’ channel. The method mainly relies on satellite imagery and elevation data to devise a quick model of the channel. The model has been successfully applied to study the Bolivian sector of the well-known mining-contaminated Rio Pilcomayo. The analysis shows that the portion of the channel from Villamontes to D’Orbigny accounts for more than half of the total c. 314 km2 sedimentation area of the Pilcomayo in Bolivia, and that the most environmentally problematic area is centreed around Puente Sucre, where agriculture is practiced on the contaminated floodplain. Combined with supplementary bathymetric data on the depth of the river in various points around the channel the method could offer further insight into the sediment fluxes and transport capacity of the Pilcomayo in various sectors and could thus be successfully used to assess other large mining-contaminated river channels around the world.

The processes, rates, controlling factors and products of alunite (KAl3(SO4)2(OH)6) dissolution were assessed using batch dissolution experiments at pHs of c. 3, 4, 4.6, 7 and 8, and temperatures of c. 280, 293 and 313K. Alunite dissolution is roughly congruent at pH3, while at pH≥3.9 the process is incongruent, giving a lower Al/K ratio in solution than in the pristine alunite sample. The decrease in the Al/K ratio appears to be caused by precipitation of secondary aluminium sulfate/hydroxysulfate minerals coating the surface of the dissolving alunite, as inferred from SEM images and XPS determinations, but these minerals do not passivate the alunite surface for the time frame of the experiments (up to 400h). The lowest dissolution rates are obtained for pH4.6 and 280K. Both the temperature increase and any pH variation from that point lead to faster dissolution rates. Based on the potassium release to solution, the influence of pH and temperature on the alunite dissolution rate for pH of 4.8 and below can be expressed as;. rateK = 10 4.4 ± 0.5aH+0.10 ± 0.02e 32±3/RT where rateK is the alunite dissolution rate (in mol·m-2·s-1); aH+ is the activity of hydrogen ions in solution; R is the Universal gas constant (in kJ·mol-1·K-1) and T is temperature (in K).For pH of 4.6 and above, the alunite dissolution rate can instead be expressed as;. rateK = 102.5±0.8aOH0.14±0.02e-39±4/RT where aOH- is the activity of hydroxyl ions in solution. In light of the calculated values for the activation energy under the two sets of pH conditions (32 ± 3 and 39 ± 4 kJ·mol-1), alunite dissolution appears to be surface-controlled. Examination of the most stable solvated alunite surfaces obtained by atomistic computer simulations suggests that the least energetically favourable steps during alunite dissolution are the detachment of either Al atoms or SO4 tetrahedra from exposed surfaces. Thus, these processes are most probably the rate-determining steps in alunite dissolution.

A natural Mn oxide (NMO) waste was assessed as an in situ remediation amendment for Pb contaminated sites. The viability of this was investigated using a 10month lysimeter trial, wherein a historically Pb contaminated soil was amended with a 10% by weight model NMO. The model NMO was found to have a large Pb adsorption capacity (qmax 346±14mgg-1). However, due to the heterogeneous nature of the Pb contamination in the soils (3650.54-9299.79mgkg-1), no treatment related difference in Pb via geochemistry could be detected. To overcome difficulties in traditional geochemical techniques due to pollutant heterogeneity we present a new method for unequivocally proving metal sorption to in situ remediation amendments. The method combines two spectroscopic techniques; namely electron probe microanalysis (EPMA) and X-ray photoelectron spectroscopy (XPS). Using this we showed Pb immobilisation on NMO, which were Pb free prior to their addition to the soils. Amendment of the soil with exogenous Mn oxide had no effect on microbial functioning, nor did it perturb the composition of the dominant phyla. We conclude that NMOs show excellent potential as remediation amendments.

The effects of Sb on the precipitation of synthetic scorodite, and the resultant phases formed, were investigated. Nine synthetic precipitates with varying concentrations of Sb, together with As-only and Sb-only end members, were prepared using a scorodite synthesis method, and these were characterised using XRD, SEM, chemical digestion and μXRF mapping. XRD analysis shows that the end members are scorodite (FeAsO4·2H2O) and tripuhyite (FeSbO4), and that the intermediate members are not Sb-substituted scorodite, but instead are physical mixtures of scorodite and tripuhyite, with tripuhyite becoming more prominent with increasing amounts of Sb in the synthesis. Electron microprobe analysis on natural scorodites confirms that they contain negligible concentrations of Sb. With increasing Sb in the synthesis, the morphology of the scorodite changes from rosettes of intergrown crystals to anhedral masses of smaller crystallites. Chemical digestion of the series also became increasingly difficult with increasing Sb content. We conclude that Sb is not taken up in scorodite (perhaps due to its larger ionic radius and different co-ordination with O compared to As), that increasing amounts of Sb in the system affect scorodite morphology, and that tripuhyite is a highly stable and perhaps underestimated Sb-sink.

On a global scale demand for the products of the extractive industries is ever increasing. Extraction of the targeted resource results in the concurrent production of a significant volume of waste material, including tailings, which are mixtures of crushed rock and processing fluids from mills, washeries or concentrators that remain after the extraction of economic metals, minerals, mineral fuels or coal. The volume of tailings is normally far in excess of the liberated resource, and the tailings often contain potentially hazardous contaminants. A priority for a reasonable and responsible mining organization must be to proactively isolate the tailings so as to forestall them from entering groundwaters, rivers, lakes and the wind. There is ample evidence that, should such tailings enter these environments they may contaminate food chains and drinking water. Furthermore, the tailings undergo physical and chemical change after they have been deposited. The chemical changes are most often a function of exposure to atmospheric oxidation and tends to make previously, perhaps safely held contaminants mobile and available. If the tailings are stored under water, contact with the atmosphere is substantially reduced, thereby forestalling oxygen-mediated chemical change. It is therefore accepted practice for tailings to be stored in isolated impoundments under water and behind dams. However, these dams frequently fail, releasing enormous quantities of tailings into river catchments. These accidents pose a serious threat to animal and human health and are of concern for extractive industries and the wider community. It is therefore of importance to understand the nature of the material held within these dams, what best safety practice is for these structures and, should the worst happen, what adverse effects such accidents might have on the wider environment and how these might be mitigated. This paper reviews these factors, covering the characteristics, types and magnitudes, environmental impacts, and remediation of mine tailings dam failures.

Phosphorus (P) is one of the most important limiting nutrients for the growth of oceanic phytoplankton and terrestrial ecosystems, which in turn contributes to CO2 sequestration. The solid-phase speciation of P will influence its solubility and hence its availability to such ecosystems. This study reports on the results of X-ray diffraction, electron microprobe chemical analysis and X-ray mapping, chemical extractions and X-ray absorption near-edge spectroscopy analysis carried out to determine the solid-phase speciation of P in dusts and their source sediments from the Saharan Bodélé Depression, the world's greatest single source of dust. Chemical extraction data suggest that the Bodélé dusts contain 28 to 60% (mean 49%) P sorbed to, or co-precipitated with, Fe (hydr)oxides,

The enthalpy of formation from the elements of well characterized Pb-As, Pb-Cu, and Pb-Zn synthetic jarosites, corresponding to chemical formulas (H3O)0.68±0.03Pb0.32±0.002Fe2.86±0.14(SO4)1.69±0.08(AsO4)0.31±0.02(OH)5.59±0.28(H2O)0.41±0.02, (H3O)0.67±0.03Pb0.33±0.02Fe2.71±0.14Cu0.25±0.01(SO4)2±0.00(OH)5.96±0.30(H2O)0.04±0.002 and (H3O)0.57±0.03Pb0.43±0.02Fe2.70±0.14Zn0.21±0.01(SO4)2±0.00(OH)5.95±0.30(H2O)0.05±0.002, was measured by high temperature oxide melt solution calorimetry and gave δH°f=-3691.2±8.6kJ/mol, δH°f=-3653.6±8.2kJ/mol, and δH°f=-3669.4±8.4kJ/mol, respectively. Using estimated entropies, the standard Gibbs free energy of formation from elements at 298K δG°f of the three compounds were calculated to be -3164.8±9.1, -3131.4±8.7, and -3153.6±8.9kJ/mol, respectively. Based on these free energies, their logKsp values are -13.94±1.89, -4.38±1.81 and -3.75±1.80, respectively. For this compounds, a log10{Pb2+}-pH diagram is presented. The diagram shows that the formation of Pb-As jarosite may decrease aqueous arsenic and lead concentrations to meet drinking water standards. The new thermodynamic data confirm that transformation of Pb-As jarosite to plumbojarosite is thermodynamically possible. © 2013 Elsevier Ltd.

The toxic element arsenic (As) occurs widely in solid and liquid mine wastes. Aqueous forms of arsenic are taken up in As-bearing sulfides, arsenides, sulfosalts, oxides, oxyhydroxides, Fe-oxides, -hydroxides, -oxyhydroxides and -sulfates, and Fe-, Ca-Fe- and other arsenates. Although a considerable body of research has demonstrated that microbes play a significant role in the precipitation and dissolution of these As-bearing minerals, and in the alteration of the redox state of As, in natural and simulated mining environments, the molecular-scale mechanisms of these interactions are still not well understood. Further research is required using traditional and novel mineralogical, spectroscopic and microbiological techniques to further advance this field, and to help design remediation schemes.

Polaromonas sp. str. GM1 is an aerobic, psychrotolerant, heterotrophic member of the Betaproteobacteria and is the only isolate capable of oxidising arsenite at temperatures below 10 °C. Sequencing of the aio gene cluster in GM1 revealed the presence of the aioB and aioA genes, which encode the arsenite oxidase but the regulatory genes typically found upstream of aioB in other members of the Proteobacteria were absent. The GM1 Aio was purified to homogeneity and was found to be a heterodimer. The enzyme contained Mo and Fe as cofactors and had, using the artificial electron acceptor 2,6- dichlorophenolindophenol, a Km for arsenite of 111.70 ± 0.88 μM and a Vmax of 12.16 ± 0.30 U mg-1, which is the highest reported specific activity for any known Aio. The temperature-activity profiles of the arsenite oxidases from GM1 and the mesophilic betaproteobacterium Alcaligenes faecalis were compared and showed that the GM1 Aio was more active at low temperatures than that of A. faecalis. A homology model of the GM1 Aio was made using the X-ray crystal structure of the Aio from A. faecalis as the template. Structural changes that account for cold adaptation were identified and it was found that these resulted in increased enzyme flexibility and a reduction in the hydrophobicity of the core. © 2013 the Royal Society of Chemistry.

Silver has been known for centuries to be a powerful disinfectant, with no known harmful effects to humans if applied in adequate doses. Although its use was partially discontinued with the advent of chlorination and modern antibiotics, the discovery of bacterial resistance and disinfection byproducts has enabled its re-emergence as a viable water purification option. On the other hand, implementation in small-scale rainwater harvesting (RWH) systems has received little attention, possibly due to a general perception that it is a complex and/or expensive technology. This can be overcome by efficient designs that dose silver ions into the water at a minimal cost. The authors evaluated a dozen RWH systems equipped with silver releasing devices, which have been providing drinking water to schools and clinics in a rural area of Mexico. This paper represents a follow-up to a previously published study on an evaluation performed in the same region. A number of water quality parameters have been analysed, examining the long-term efficiency of the projects. Our observations show that the silver ion devices act as an effective disinfection mechanism, as long as adequate maintenance is provided. The combination with conventional settling tanks and filtration units seems to greatly enhance the overall performance of the system. © IWA Publishing 2013.

Lead (Pb) concentrations and isotopic compositions from soils, dusts and aerosols from public land and residential lots adjacent to the copper and Pb mine and smelter at Mount Isa, Australia, were examined to understand the sources and risks of environmental Pb exposure. Urban soil samples contain elevated Pb concentrations (mean 1560 mg/kg), of which 45-85% of the Pb is bioaccessible. The Pb isotopic composition of surface soils (0-2 cm), aerosols and dusts (206Pb/207Pb, 208Pb/207Pb range: 1.049, 2.322-1.069, 2.345) are dominated by Pb derived from the Mount Isa Pb-zinc ore bodies. Underlying soil horizons (10-20 cm) have distinctly different Pb isotopic compositions (206Pb/207Pb, 208Pb/207Pb range: 1.093, 2.354 -1.212, 2.495). Surface soil-, dust- and aerosol-Pb are derived predominantly from smelter emissions and fugitive mining sources and not from in situ weathered bedrock. Remediation strategies should target legacy and ongoing sources of environmental Pb to mitigate the problem of Pb exposure at Mount Isa. © 2013 Elsevier Ltd. All rights reserved.

Siderophores are Fe3+specific low MW chelating ligands secreted by micro-organisms in response to Fe stress. Low MW organic acids such as oxalate have been shown to enhance siderophore mediated dissolution of Fe3+oxides. However, the effect of fulvic acid presence on siderophore function remains unknown. We used batch dissolution experiments to investigate Fe release from goethite in the goethite-fulvic acid-desferrioxamine B (goethite-SRFA-DFOB) ternary system. Experiments were conducted at pH 6.5 while varying reagent addition sequence. FTIR and UV-Vis spectroscopy were employed to characterise the Fe-DFOB, Fe-SRFA and DFOB-SRFA complexes. Iron released from goethite in the presence of SRFA alone was below detection limit. In the presence of both SRFA and DFOB, dissolved Fe increased with reaction time, presence of the DFOB-SRFA complex, and where SRFA was introduced prior to DFOB. FTIR data show that in the ternary system, Fe3+is complexed primarily to oxygen of the DFOB hydroxamate group, whilst the carboxylate CO of SRFA forms an electrostatic association with the terminal NH3+ of DFOB. We propose that SRFA sorbed to goethite lowers the net positive charge of the oxide surface, thus facilitating adsorption of cationic DFOB and subsequent Fe3+ chelation and release. Furthermore, the sorbed SRFA weakens Fe-O bonds at the goethite surface, increasing the population of kinetically labile Fe. This work demonstrates the positive, though indirect role of SRFA in increasing the bioavailability of Fe3+. © 2013.

The weathering and oxidation of mine tailings has the potential to contaminate water and soil with toxic elements. To understand the mechanisms, extent and products of the long-term weathering of complex Bolivian tailings from the Cerro Rico de Potosí, and their effects on As, Pb, P and Sb cycling, three-year long laboratory column experiments were carried out to model 20 years of dry-and wet-season conditions in the Pilcomayo basin. Chemical analysis of the leachate and column solids, optical mineralogy, X-ray diffraction, scanning electron microscopy, electron probe microanalysis, microscale X-ray absorption near edge structure spectroscopy, Bureau Commun de Référence sequential extraction and water-soluble chemical extractions, and speciation modelling have shown that the weathering of As-bearing pyrite and arsenopyrite, resulted in a loss of 13-29% of the original mass of As. By contrast, Pb and Sb showed much lower mass losses (0.1-1.1% and 0.6-1.9%, respectively) due to the formation of insoluble Pb-and Sb(V)-rich phases, which were stable at the low pH (~2) conditions that prevailed by the end of the experiment. The experiment also demonstrated a link between the cycling of As, Sb, and the oxidation of Fe(II)-bearing sphalerite, which acted as a nucleation point for an Fe-As-Sb-O phase. Phosphorus was relatively immobile in the tailings columns (up to 0.3% mass loss) but was more mobile in the soil-bearing columns (up to 10% mass loss), due to the formation of soluble P-bearing minerals or mobilization by organic matter. These results demonstrate the influence of mine tailings on the mobility of P from soils and on the potential contamination of ecosystems with As, and strongly suggest that these materials should be isolated from fluvial environments. © 2012 Mineralogical Society.

Spring, stream and tap waters from in and around San Antonio de los Cobres, Salta, Argentina, were sampled to characterize their geochemical signatures, and to determine whether they pose a threat to human health and crops. The spring waters are typical of geothermal areas world-wide, in that they are Na-Cl waters with high concentrations of As tot, As(III), Li, B, HCO 3, F and SiO 2 (up to 9.49, 8.92, 13.1, 56.6, 1250, 7.30 and 57.2mgL -1, respectively), and result from mixing of deep Na-Cl brines and meteoric HCO 3-rich waters. Springs close to the town of San Antonio have higher concentrations of all elements, and are generally cooler, than springs in the Baños de Agua Caliente. Spring water chemistry is a result of mixing of deep Na-Cl brines and meteoric HCO 3 waters. Stream waters are also Na-Cl type, and receive large inputs of all elements from the springs near San Antonio, but concentrations decrease downstream through the town of San Antonio due to mineral precipitation. The spring that is used as a drinking water source, and other springs in the area, have As, F and B concentrations in excess of WHO and Argentinian drinking water guidelines. Evaluation of the waters for irrigation purposes suggests that their high salinities and B concentrations may adversely affect crops. The waters may be improved for drinking and irrigation by dilution with cleaner meteoric waters, mineral precipitation or by use of commercial filters. Such recommendations could also be followed by other settlements that draw drinking and irrigation waters from geothermal sources. © 2011 Elsevier B.V.

Mine tailings discharged to river systems have the potential to release significant quantities of major and trace metals to waters and soils when weathered. To provide data on the mechanisms and magnitudes of short- and long-term tailings weathering and its influence on floodplain environments, three calendar year-long column leaching experiments that incorporated tailings from Potosí, Bolivia, and soil from unaffected downstream floodplains, were carried out. These experiments were designed to model 20 cycles of wet and dry season conditions. Two duplicate columns modeled sub-aerial tailings weathering alone, a third modeled the effects of long-term floodplain tailings contamination and a fourth modeled that of a tailings dam spill on a previously contaminated floodplain. As far as was practical local climatic conditions were modeled. Chemical analysis of the leachate and column solids, optical mineralogy, XRD, SEM, EPMA, BCR and water-soluble chemical extractions and speciation modeling were carried out to determine the processes responsible for the leaching of Al, Ca, Cu, K, Na, Mg, Mn, Sn, Sr and Ti. Over the 20 cycles, the pH declined to a floor of ca. 2 in all columns. Calcium, Cu, Mg, Mn and Na showed significant cumulative losses of up to 100%, 60%, 30%, 95% and 40%, respectively, compared to those of Al, K, Sr, Sn and Ti, which were up to 3%, 1.5%, 5%, 1% and 0.05%, respectively. The high losses are attributed to the dissolution of relatively soluble minerals such as biotite, and oxidation of chalcopyrite and Cu-sulfosalts, while low losses are attributed to the presence of sparingly soluble minerals such as svanbergite, cassiterite and rutile. These results strongly suggest that the release of tailings to floodplains should be limited or prohibited, and that all tailings should be removed from floodplains following dam spills. © 2011 Elsevier Ltd.

Jarosites are produced during metallurgical processing, on oxidized sulfide deposits, and in acid mine drainage environments. Despite the environmental relevance of jarosites, few studies have examined their biogeochemical stability. This study demonstrates the simultaneous reduction of structural Fe(III) and aqueous As(V) during the dissolution of synthetic Pb-As jarosite (PbFe3(SO4,AsO4)2(OH)6) by Shewanella putrefaciens using batch experiments under anaerobic circumneutral conditions. Fe(III) reduction occurred immediately in inoculated samples while As(V) reduction was observed after 72 h. XANES spectra showed As(III) (14.7%) in the solid phase at 168 h coincident with decreased aqueous As(V). At 336 h, XANES spectra and aqueous speciation analysis demonstrated 20.2% and 3.0% of total As was present as As(III) in the solid and aqueous phase, respectively. In contrast, 12.4% of total Fe was present as aqueous Fe(II) and was below the detection limits of XANES in the solid phase. TEM-EDS analysis at 336 h showed secondary precipitates enriched in Fe and O with minor amounts of As and Pb. Based on experimental data and thermodynamic modeling, we suggest that structural Fe(III) reduction was thermodynamically driven while aqueous As(V) reduction was triggered by detoxification induced to offset the high As(V) (328 μM) concentrations released during dissolution. © 2012 American Chemical Society.

Jarosite is an important mineral on Earth, and possibly on Mars, where it controls the mobility of iron, sulfate and potentially toxic metals. Atomistic simulations have been used to study the incorporation of Al3+, and the M2+ impurities Cd, Cu and Zn, in the (012) and (001) surfaces of jarosite. The calculations show that the incorporation of Al on an Fe site is favorable on all surfaces in which terminal Fe ions are exposed, and especially on the (001) [Fe3(OH)3]6+ surface. Incorporation of Cd, Cu or Zn on a K site balanced by a K vacancy is predicted to stabilize the surfaces, but calculated endothermic solution energies and the high degree of distortion of the surfaces following incorporation suggest that these substitutions will be limited. The calculations also suggest that incorporation of Cd, Cu and Zn on an Fe site balanced by an OH vacancy, or by coupled substitution on both K and Fe sites, is unfavorable, although this might be compensated for by growth of a new layer of jarosite or goethite, as predicted for bulk jarosite. The results of the simulations show that surface structure will exert an influence on uptake of impurities in the order Cu>Cd>Zn, with the most favorable surfaces for incorporation being (012) [KFe(OH)4]0 and (001) [Fe3(OH)3]6+. © 2010 Elsevier Ltd.

With growing pressures on water supplies worldwide, rainwater harvesting is increasingly seen as a viable option to provide drinking water to an ever expanding population, particularly in developing countries. However, rooftop runoff is not without quality issues. Microbiological and chemical contamination have been detected in several studies, well above local and international guidelines, posing a health risk for consumers. Our research explores the use of silver ions, combined with conventional filtration and settling mechanisms, as a safe and affordable model for purification that can be applied on a small scale. The complete systems were installed and tested in rural communities in a Mexican semi-arid region. Efficiencies up to 99.9% were achieved in the removal of indicator microorganisms, with a marked exception where cross-contamination from external seepage occurs. Sites without overhanging branches or with relatively clean surfaces show an absence of total coliforms in the untreated runoff, compared with others where values as high as 1,650 CFU/100 ml were recorded. Thus, given adequate maintenance, the system can successfully deliver high quality drinking water, even when storage is required for long periods of time. © IWA Publishing 2011.

The weathering of discharged mine tailings can contaminate groundwaters, rivers and floodplains with potentially toxic Cd and Zn, depending on tailings mineralogy, storage, dispersal and climatic conditions. The mechanisms of long-term tailings weathering and its influence on waste piles and floodplain environments were assessed by a column leaching experiment that incorporated tailings and soil from Potosí, Bolivia, and modelled 20 cycles of wet and dry season conditions over three calendar years. Chemical analysis of the leachate and column solids, optical mineralogy, XRD, SEM, EPMA, BCR and water-soluble chemical extractions and speciation modelling were carried out to determine the processes responsible for the leaching of Cd, Fe, S and Zn. Over this period, approximately 50 to 95% of the original Cd and 50 to 60% of the Zn were leached from the columns. Large amounts of leached Cd and Zn at the beginning of the experiment are attributed to the dissolution of soluble sulphate minerals present in the original tailings and formed after the first wetting of the columns. The Zn/Cd mass ratios of the tailings and soil, initially 429 and 400, respectively, vary considerably over the course of the experiment. Low values (between 220 and 300) in the early cycles are attributed to preferential weathering of Cd-rich wurtzite [Zn,Fe)S] and sequestration of Zn in preference to Cd in secondary Fe phases forming in the columns. In the middle cycles, dissolution of secondary Fe(OH)3 under low pH (

Mine wastes are unwanted, currently uneconomic, solid and liquid materials found at or near mine sites. Volumetrically they are one of the world's largest waste streams, and they often contain high concentrations of elements and compounds that can have severe effects on ecosystems and humans. Multidisciplinary research on mine wastes focuses on understanding their character, stability, impact, remediation and reuse. This research must continue if we are to understand and sustainably manage the immense quantities of historic, contemporary and future mine wastes, given the trend to exploit larger deposits of lower-grade ores.

This study aimed to assess AMF diversity in various plant species in lakes with low and relatively high P concentrations to elucidate possible correlations with environmental factors in order for better understanding the functioning of mycorrhizal fungi in submerged plants. A considerable diversity of AMF communities was observed in the lakes with low dissolved P concentrations, especially in the roots of Littorella uniflora. Glomus group A, Archaeospora and Acaulospora were the most frequent and diverse AMF lineages with eight, seven and four phylotypes at Littorella uniflora in at least six lakes with low dissolved P concentrations. In theses lakes, AMF were for the first time observed in the roots of J. bulbosus, a member of a family previously thought to be non-mycorrhizal. In the lakes with relatively high dissolved P concentrations, the frequency decreased from Acaulospora, found at three locations, to Archaeospora at two locations and Glomus group a and Paraglomus at one location. All chemical parameters of the surface water layer, except pH, revealed significant (p≤0.01) differences between the lakes with low and relatively high dissolved P concentrations. Mean Mg2+, Ca2+, K+, NH4+, CO2, o-PO43- and HCO3- were 3, 13.5, 15.7, 19.5, 31 and 42.6 times higher, respectively, in the lakes with relatively high dissolved P concentrations compared to the lakes with low dissolved P concentrations. AMF occurred more abundantly with low phosphate and high redox values in the lakes than with high phosphate and low redox values. The pH-value, the total-calcium and total-phosphorus concentrations were strongly correlated with the occurrence of Glomus phylotypes 4 and Archaeospora phylotypes 5 and 8, and a bit less with Acaulospora phylotype 4 and Archaeospora phylotype 3. In such lakes the presence of a diverse AMF community still enables the uptake of sufficient P for isoetid plant species despite the prevailing 'ultra-oligotrophic' conditions. As a consequence, macrophyte plant communities in lakes with relatively high dissolved P concentrations are less dependent on AMF colonization for their development. © 2010 Elsevier B.V.

X-ray absorption spectroscopy, scanning electron microscopy (SEM) and X-ray diffractometry (XRD) have been used to study the solid-phase speciation of Zn in urban road dust sediments (RDS) in Manchester, UK. X-ray absorption near-edge structure (XANES) analysis using linear combination modelling suggest that the soluble species Zn(NO 3) 2•6H 2O and ZnCl 2 represent 70-83%, and Zn-sorbed goethite 17-30%, of the Zn species present. The presence of goethite is not corroborated by extended X-ray absorption fine structure (EXAFS) modelled first shell scattering Zn-O distances of 2.01-2.03 Å , but this may be due to distortion of the Zn octahedra on the goethite surface, or the existence of Zn-sorbed species with other metal hydrous oxides, as inferred by the EXAFS-modelled second shell Fe and Al scatterers. Analysis by EXAFS also suggests that metallic Zn-Cu-Sn-Pb and Zn-silicate phases are present in the RDS, and this is corroborated by SEM and XRD. Other phases suggested by EXAFS include ZnO, franklinite, Zn-sorbed birnessite and zinc formate. Differences between the XANES and other results suggest that model compounds such as Zn-bearing phyllosilicates and metallic Zn phases may have been missing from the XANES fitting. Long-term low-level exposure to the RDS Zn phases identified may lead to an increased risk of cardiovascular or pulmonary diseases. © 2011 the Mineralogical Society.

This article presents the geochemical characteristics and physicochemical properties of water and sediment from twelve semi-permanent, dryland pools in the upper Leichhardt River catchment, north-west Queensland, Australia. The pools were examined to better understand the quality of sediments and temporary waters in a dryland system with a well-established metal contamination problem. Water and sediment sampling was conducted at the beginning of the hydroperiod in May and September 2007. Water samples were analyzed for major solute compositions (Ca, Na, K, Mg, Cl, SO 4, HCO 3) and water-soluble (operationally defined as the

Atmospheric mineral dust plays a vital role in Earth's climate and biogeochemical cycles. The Bodl Depression in Chad has been identified as the single biggest source of atmospheric mineral dust on Earth. Dust eroded from the Bodélé is blown across the Atlantic Ocean towards South America. The mineral dust contains micronutrients such as Fe and P that have the potential to act as a fertilizer, increasing primary productivity in the Amazon rain forest as well as the equatorial Atlantic Ocean, and thus leading to N 2 fixation and CO2 drawdown. We present the results of chemical analysis of 28 dust samples collected from the source area, which indicate that up to 6.5 Tg of Fe and 0.12 Tg of P are exported from the Bodélé Depression every year. This suggests that the Bodl may be a more significant micronutrient supplier than previously proposed. © 2010 by the American Geophysical Union.

Background: Arsenic is toxic to most living cells. The two soluble inorganic forms of arsenic are arsenite (+3) and arsenate (+5), with arsenite the more toxic. Prokaryotic metabolism of arsenic has been reported in both thermal and moderate environments and has been shown to be involved in the redox cycling of arsenic. No arsenic metabolism (either dissimilatory arsenate reduction or arsenite oxidation) has ever been reported in cold environments (i.e. < 10°C). Results: Our study site is located 512 kilometres south of the Arctic Circle in the Northwest Territories, Canada in an inactive gold mine which contains mine waste water in excess of 50 mM arsenic. Several thousand tonnes of arsenic trioxide dust are stored in underground chambers and microbial biofilms grow on the chamber walls below seepage points rich in arsenite-containing solutions. We compared the arsenite oxidisers in two subsamples (which differed in arsenite concentration) collected from one biofilm. 'Species' (sequence) richness did not differ between subsamples, but the relative importance of the three identifiable clades did. An arsenite-oxidising bacterium (designated GM1) was isolated, and was shown to oxidise arsenite in the early exponential growth phase and to grow at a broad range of temperatures (4-25°C). Its arsenite oxidase was constitutively expressed and functioned over a broad temperature range. Conclusions: the diversity of arsenite oxidisers does not significantly differ from two subsamples of a microbial biofilm that vary in arsenite concentrations. GM1 is the first psychrotolerant arsenite oxidiser to be isolated with the ability to grow below 10°C. This ability to grow at low temperatures could be harnessed for arsenic bioremediation in moderate to cold climates. © 2010 Osborne et al; licensee BioMed Central Ltd.

This article investigates the relationship between soil Cd, Cu, Pb and Zn contaminants and the location and activities of the Pb-Zn-Ag and Cu mines at Mount Isa, Queensland, Australia. Analysis of the data focuses primarily on soil Pb distributions and concentrations because of their potential impact on children's health. The Xstrata Mount Isa Mines lease (XMIM) is Australia's leading emitter of numerous contaminants to the environment, including Cu and Pb, and the mining-related activities have been linked causally to the findings of a 2008 study that showed 11.3% of local children (12-60. months) have blood Pb levels >10μg/dL. Queensland government authorities and Xstrata Mount Isa Mines Pty Ltd maintain that contaminants within environmental systems around Mount Isa are largely the result of near-surface mineralization. The evidence for whether the contamination is derived from XMIM or other possible sources, such as the natural weathering of ore-rich bedrock, is investigated using data from surface and subsurface soil chemistry, atmospheric modelling of metal contaminants from mining and smelting operations and local geological and associated geochemical studies. Sixty surface soil samples collected from sites adjacent to houses, parks and schools throughout Mount Isa city were analyzed for their total extractable Cd, Cu, Pb and Zn concentrations in the 180μm (coarser) and

The quality of the urban environment is of growing concern as its human population continues to dramatically increase. X-ray absorption spectroscopy (XAS) and SEM have been used to study the solid-phase speciation of Pb in urban road dust sediments (RDS) in Manchester, UK. XANES analysis and linear combination modeling indicate that PbCrO4 and Pb-sorbed goethite occur in 1000?500 μm, 250?125 μm, 63?38 μm, and

The enthalpy of formation from the elements of a well-characterized synthetic Pb-jarosite sample corresponding to the chemical formula (H3O)0.74Pb0.13Fe2.92(SO4)2(OH)5.76(H2O)0.24 was measured by high temperature oxide melt solution calorimetry. This value (Δ H{ring operator}f = -3695.9 ± 9.7 kJ/mol) is the first direct measurement of the heat of formation for a lead-containing jarosite. Comparison to the thermochemical properties of hydronium jarosite and plumbojarosite end-members strongly suggests the existence of a negative enthalpy of mixing possibly related to the nonrandom distribution of Pb2+ ions within the jarosite structure. Based on these considerations, the following thermodynamic data are proposed as the recommended values for the enthalpy of formation from the elements of the ideal stoichiometric plumbojarosite Pb0.5Fe3(SO4)2(OH)6: Δ G{ring operator}f = -3118.1 ± 4.6 kJ/mol, Δ H{ring operator}f = -3603.6 ± 4.6 kJ/mol and S° = 376.6 ± 4.5 J/(mol K). These data should prove helpful for the calculation of phase diagrams of the Pb-Fe-SO4-H2O system and for estimating the solubility product of pure plumbojarosite. For illustration, the evolution of the estimated solubility product of ideal plumbojarosite as a function of temperature in the range 5-45 °C was computed (Log(Ksp) ranging from -24.3 to -26.2). An Eh-pH diagram is also presented. © 2009 Elsevier Ltd.

This study has investigated the utility of using field-based reflectance spectroscopy to characterise the distribution and nature of the dispersion of tailings material from the Rodalquilar mine, Spain. Field spectral measurements covering the visible to shortwave infrared wavelengths (0.35 to 2.5 m) and laboratory analyses were performed on samples collected along the length of the main river within the Rodalquilar valley. The nature and degree of contamination at locations within the river channel were calculated by a range of spectrometric analyses. The resulting mineral maps identified that tailings material with significant amounts of hematite with minor jarosite, ferrihydrite and goethite, and clays, primarily alunite and kaolinite, with minor smectite and illite, had been dispersed along the length of the river. These results have been used to improve understanding of the erosion and remediation history of the Rodalquilar mine. This study has shown the potential of field-based reflectance spectroscopy, integrated with ground positioning and digital mapping systems, as a real-time mapping methodology enabling immediate, accurate characterisation of the nature and scale of tailings material dispersion. © 2008 Elsevier B.V. All rights reserved.

This paper examines the environmental risk and impact of trace metals affecting river water and sediment in and around Mount Isa, Queensland, Australia. Bacterial indicator densities are also analysed throughout the catchment to assess the impacts and the potential hazards arising from agricultural activities, sewage treatment plant releases and urban runoff. The area is drained by the ephemeral Leichhardt River, which bisects Mount Isa City and the major Pb, Zn, Cu and Ag Mount Isa Mine. Runoff is captured downstream in Lake Moondarra, with the water being used following natural filtration via a lagoon-reed bed system for potable purposes by the residents of Mount Isa City. During the dry season, the channel is characterised by numerous pools that act as storage zones for sediment and water-soluble metals as well as urban and agriculturally derived nutrients and pathogens. Our results show that sediment and water quality within the Leichhardt River adjacent to and downstream of the mine frequently exceed Australian government sediment guidelines with average values of Cu, Pb and Zn found adjacent to the footprint of the mine being 1550, 510 and 470 mg kg-1, respectively. Dry season analysis of water-soluble Cu, Pb and Zn concentrations within pools showed that Australian government low trigger guidelines are exceeded in 100, 46 and 100% cases, respectively. The densities of bacterial indicators in remnant pools throughout the Leichhardt River also exceeded acceptable guidelines. Maximum dry season faecal coliform densities of 2000 colony forming units (CFU) per 100 mL and Enterococcus counts of 900 organisms per 100 mL were recorded in dry season remnant pools compared to wet season maximum faecal coliform and Enterococcus densities of 119000 CFU per 100 mL and 95000 organisms per 100 mL, respectively. The impacts on biota were also examined by assessing the metal content of the tissue of seven fish from Lake Moondarra for their Cd, Cu, Hg, Pb and Zn concentrations. Tissue metal values were generally low with only a few samples having Cu and Zn values in excess of the recommended Australian retail guideline values for fish suitable for human consumption. The effectiveness of the City's natural reed bed potable water processing facility for removing metals held within the water body (soluble and particulate) was also assessed. The results show that the treated water generally meets Australian drinking water guidelines. Overall it is clear that sediment and water quality in the area upstream of the potable water storage zone is seriously impaired. The combined effects of industrial, agricultural and urban activities present a considerable risk to the consistency and reliability of water quality, especially during highly turbid wet season flows, which transfer highly elevated concentrations of water-soluble metal and microbial contaminants. © 2009 the Royal Society of Chemistry.

Raman and IR spectroscopies, X-ray diffraction and chemical analysis have been used to characterize synthetic compounds of the alunite supergroup of formula AB3(SO4)2(OH)6, with a = Na+, K+, H3O+ and B = Al, Cr 3+, Fe3+, V3+. For each A-site cation, the proportion of B-site vacancies decreases in the same order as the effective ionic radius of the B-site cations (Al > Cr > Fe > V). Raman and IR spectra of the compounds with B = Al and Fe3+ (alunite- and jarosite-group phases) show very close agreement with previously published spectra. The spectra for Cr- and V-based analogues show similarities to the alunite- and jarosite-group phases, and particularly the latter. The Raman and IR spectra are similar in the high-wavenumber ranges (around 3400-3500 cm -1), but are different in the intermediate and, particularly, the lower ranges,

Jarosite minerals are effective scavengers of potentially toxic elements such as Pb and Cu, and are abundant in acid rock drainage systems, acid sulfate soils and metallurgical wastes. We used XRD, SEM, and infrared, Raman and X-ray absorption (EXAFS and XANES) spectroscopy tp determine the structural differences between natural and synthetic Pb-Cu-jarosites. Differences in the a0 unit cell dimensions for the natural and synthetic samples (7.2288(27) Å and 7.32088(26) Å, respectively), and c0 unit cell values (34.407(14) Å and 17.0336(7) Å, respectively) are attributed to different proportions of H3O, Fe and Pb in the jarosite structures. The synthetic Pb-Cu-jarosite has sharper Raman and IR spectra, with narrower and more intense bands, suggesting that it is more crystalline than the natural sample. EXAFS fitting of the Fe and Pb data for the natural and synthetic Pb-Cu-jarosite samples are similar to each other, and are also similar to previously reported EXAFS data for jarosites, suggesting that Fe occupies the B sites, and Ph the a sites. The natural sample's Pb EXAFS data are only fitted over a short k-range, however, and the comparison is based on only the first two shells around Pb. Our Cu fits for the natural Pb-Cu-jarosite are similar to the first and third shell fittings for Fe, except that the Cu occupies a tetrahedral rather than an octahedral site (4 O in first shell at r = 1.94-1.95 Å; 4 Fe in third shell at r = 3.59-3.60 Å). In the synthetic Pb-Cu-jarosite, Cu also shares the B site with Fe, but fits of 4 Cu around the Cu atom at a bond distance of 2.60 Å and XANES evidence also suggest the presence of metallic Cu within the structure. Variations in the structures of the natural and synthetic samples are Rely due to their differing chemistries and conditions of formation. © 2008 E. Schweizerbart'sche Verlagsbuchhandlung, D-70176 Stuttgart.

The sediments in the Salford Quays, a heavily-modified urban water body, contain high levels of organic matter, Fe, Zn and nutrients as a result of past contaminant inputs. Vivianite [Fe3(PO4)2 · 8H2O] has been observed to have precipitated within these sediments during early diagenesis as a result of the release of Fe and P to porewaters. These mineral grains are small (

In the Bengal Basin, the land surface exposed during the last lowstand of sea level around 20 ka, and now buried by Holocene sediment, is capped by an effectively impermeable clay paleosol that we term the Last Glacial Maximum paleosol (LGMP). The paleosol strongly affects groundwater flow and controls the location of arsenic pollution in the shallow aquifers of our study site in southern West Bengal and, by implication, in shallow aquifers across the Bengal Basin and As-polluted deltaic aquifers worldwide. The presence of the LGMP defines paleointerfluvial areas; it is absent from paleochannel areas. A paleosol model of pollution proposed here predicts that groundwater in paleochannels is polluted by arsenic, while that beneath paleointerfluvial areas is not: paleointerfluvial aquifers are unpolluted because they are protected by the LGMP from downward migration of arsenic and from downward migration of organic matter that drives As-pollution via reductive dissolution of As-bearing iron oxyhydroxides. Horizontal groundwater flow carries arsenic from paleochannels toward paleointerfluvial aquifers, in which sorption of arsenic minimizes the risk of pollution. Copyright 2008 by the American Geophysical Union.

This paper details the distribution of Cu, Pb and Zn in aquatic systems draining Mount Isa Ag-Cu-Pb-Zn Mine in arid northern Queensland, Australia. Sediment-metal concentrations in the

As the result of current and historical metal mining, river channels and floodplains in many parts of the world have become contaminated by metal-rich waste in concentrations that may pose a hazard to human livelihoods and sustainable development. Environmental and human health impacts commonly arise because of the prolonged residence time of heavy metals in river sediments and alluvial soils and their bioaccumulatory nature in plants and animals. This paper considers how an understanding of the processes of sediment-associated metal dispersion in rivers, and the space and timescales over which they operate, can be used in a practical way to help river basin managers more effectively control and remediate catchments affected by current and historical metal mining. A geomorphological approach to the management of rivers contaminated by metals is outlined and four emerging research themes are highlighted and critically reviewed. These are: (1) response and recovery of river systems following the failures of major tailings dams; (2) effects of flooding on river contamination and the sustainable use of floodplains; (3) new developments in isotopic fingerprinting, remote sensing and numerical modelling for identifying the sources of contaminant metals and for mapping the spatial distribution of contaminants in river channels and floodplains; and (4) current approaches to the remediation of river basins affected by mining, appraised in light of the European Union's Water Framework Directive (2000/60/EC). Future opportunities for geomorphologically-based assessments of mining-affected catchments are also identified. © 2006 Elsevier B.V. All rights reserved.

Computer modelling techniques involving a rigid ion model have been used to investigate the defect structure and impurity site preferences in end-member K-jarosite. Calculated intrinsic vacancy energies show that the K2SO4 neutral cluster, with an energy per species of 1.34 eV, will be the most common defect in the pure phase. Defect reactions leading to vacancies on the Fe site have high energies, in excess of 4.0 eV per species, and are thus unlikely to occur in great numbers. However, the calculations show that divalent metal cations can be incorporated onto the Fe site via solution reactions with oxides leading to the formation of goethite. Calculated solution reactions are exothermic and thus predicted to be highly favourable. At K sites substitutions occur in the order Cd > Zn > Cu, but will be limited due to endothermic solution energies and structural considerations. © 2006 Elsevier Ltd. All rights reserved.

Jarosite [KFe3(SO4)2(OH)6] is a mineral that is common in acidic, sulphate-rich environments, such as acid sulphate soils derived from pyrite-bearing sediments, weathering zones of sulphide ore deposits and acid mine or acid rock drainage (ARD/ AMD) sites. The structure of jarosite is based on linear tetrahedral-octahedral-tetrahedral (T-O-T) sheets, made up from slightly distorted FeO6 octahedra and SO4 tetrahedra. Batch dissolution experiments carried out on synthetic jarosite at pH 2, to mimic environments affected by ARD/AMD, and at pH 8, to simulate ARD/AMD environments recently remediated with slaked lime (Ca(OH)2), suggest first order dissolution kinetics. Both dissolution reactions are incongruent, as revealed by non-ideal dissolution of the parent solids and, in the case of the pH 8 dissolution, because a secondary goethite precipitate forms on the surface of the dissolving jarosite grains. The pH 2 dissolution yields only aqueous K, Fe, and SO4. Aqueous, residual solid, and computational modelling of the jarosite structure and surfaces using the GULP and MARVIN codes, respectively, show for the first time that there is selective dissolution of the A- and T-sites, which contain K and SO4, respectively, relative to Fe, which is located deep within the T-O-T jarosite structure. These results have implications for the chemistry of ARD/AMD waters, and for understanding reaction pathways of ARD/AMD mineral dissolution. © 2005 Elsevier Inc. All rights reserved.

Lead- and Pb-As-jarosites are minerals common to acidic, sulphate-rich environments, including weathering zones of sulphide ore deposits and acid rock or acid mine drainage (ARD/AMD) sites, and often form on or near galena. The structures of these jarosites are based on linear tetrahedral-octahedral-tetrahedral (T-O-T) sheets, comprised of slightly distorted FeO6 octahedra and SO42- (-AsO43- in Pb-As-jarosites) tetrahedra. To better understand the dissolution mechanisms and products of the break down of Pb- and Pb-As-jarosite, preliminary batch dissolution experiments were conducted on synthetic Pb- and Pb-As-jarosite at pH 2 and 20 °C, to mimic environments affected by ARD/AMD, and at pH 8 and 20 °C, to simulate ARD/AMD environments recently remediated with slaked lime (Ca(OH)2). All four dissolutions are incongruent. Dissolution of Pb-jarosite at pH 2 yields aqueous Pb, Fe and SO42-. The pH 8 Pb-jarosite dissolution yields aqueous Pb, SO42- and poorly crystalline Fe(OH)3, which does not appear to resorb Pb or SO42-, possibly due to the low solution pH (3.44-3.54) at the end of the experiment. The pH 2 and 8 dissolutions of Pb-As-jarosite result in the formation of secondary compounds (poorly crystalline PbSO4 for pH 2 dissolution; poorly crystalline PbSO4 and Fe(OH)3 for pH 8 dissolution), which may act as dissolution inhibitors after 250 to 300 h of dissolution. In the pH 2 dissolution, aqueous Fe, SO42- and AsO43- also form, and in the pH 8 dissolution, Fe(OH)3 precipitates then subsequently resorbs aqueous AsO43-. The dissolutions probably proceed by preferred dissolution of the A- and T-sites, which contain Pb, and SO42- and AsO43-, respectively, rather than Fe, which is sterically remote, within the T-O-T Pb- and Pb-As-jarosite structures. These data provide the foundation necessary for further, more detailed investigations into the dissolution of Pb- and Pb-As-jarosites. © 2005 Elsevier B.V. All rights reserved.

The study is undertaken in the barite mining area of Mangampeta. (Lat. 14° 01′ N; Long. 79° 19′ E), which is located in the Kodur Mandal of Cuddapah District, Andhra Pradesh, India. The important geological formations in this area are quartzites (quartz veins), carbonaceous tuff and dolomites. The paper presents the assessment of water quality for its suitability for agricultural and domestic purposes. The results of chemical analyses for the major ions of 50 water samples collected from the entire study area (mining and adjacent virgin area) are presented. The quality analysis is performed through the estimation of silica, calcium, magnesium, sodium, potassium, carbonate, bicarbonate, sulphate, chloride, total dissolved solids, pH, specific conductance, alkalinity and hardness. Based on the analyses, certain parameters like non-carbonate hardness, sodium adsorption ratio, percent sodium, potential salinity, residual sodium carbonate, Kelly's ratio, magnesium ratio, index of base exchange, permeability index and Gibb's ratio were calculated. The striking difference is in the sulphate content of mine water samples, which ranges from 211 to 589 mg/l, and is due to the presence of barites, the source for the high content of sulphates in the mining area. In contrast, in the virgin area water samples show 1-20 mg/l sulphate content. The bicarbonates (262 to 1100 mg/l) and alkalinity (198 to 953 mg/l) are very high and this is due to the presence of tuff and dolomitic rocks in the virgin area. According to the Gibb's diagram all the samples of both the virgin and mining area fall in the rock dominance field. From the evaluation it is known that the water quality is suitable for both domestic and irrigation purposes. © TÜBİTAK.

The headwaters of the Río Pilcomayo drain the Cerro Rico de Potosi precious metal-polymetallic tin deposits of southern Bolivia. Mining of these deposits has taken place for around 500 years, leading to severe contamination of the Pilcomayo's waters and sediments for at least 200 km downstream. Communities living downstream of the mines and processing mills rely on the river water for irrigation, washing and occasionally, cooking and drinking, although most communities take their drinking water from springs located in the mountains above their village. This investigation focuses on arsenic exposure in people living in riverside communities up to 150 km downstream of the source. Sampling took place in April-May 2003 (dry season) and was repeated in January-March 2004 (wet season) in five communities: El Molino, Tasapampa, Tuero Chico, Sotomayor and Cota. Cota was the control in 2003 and again in 2004; a nearby city, Sucre, and several locations in the UK were also used as controls in 2004. Drinking, irrigation and river waters, hair and urine samples were collected in each community, digested where appropriate and analysed for As using ICP-MS. Arsenic concentrations in drinking waters ranged 0.2-112 μg 1-1, irrigation water 0.6-329 μg 1-1, river waters 0.9-12,800 μg 1-1, hair 37-2110 μg kg-1 and urine 11-891 μg 1-1. All but one drinking water sample was found to contain As below the World Health Organization recommended guideline of 10 μg 1-1, although a number of irrigation and river water concentrations were above Canadian and Bolivian guidelines. Many As concentrations in the hair and urine samples from this study exceeded published values for non-occupationally exposed subjects. Analysis of mean concentration values for all media types showed that there were no statistically significant differences between the control locations and the communities exposed to known As contamination, suggesting that the source of As may not be mining-related. Arsenic concentration appears to increase as a function of age in hair samples from males and females older than 30 years. Male volunteers over the age of 35 showed increasing urine-As concentrations as a function of age, whereas the opposite was true for the females. © 2005 the Mineralogical Society.

The April 1998 breaching of the Aznalcóllar tailings dam at Boliden Apirsa's Spanish Aznalcóllar/Los Frailes Ag-Cu-Pb-Zn mine resulted in the flooding of the Ríos Agrio and Guadiamar with arsenic (As)-rich tailings and water. Mineralogical and geochemical characterisation of water and sediment from five ephemeral pools on the Agrio-Guadiamar floodplain has been carried out to understand how the As is sequestered and to evaluate the long-term stability of the As-bearing phases. Dissolved As concentrations in pool waters range from an extreme of 85,000 μg 1-1 down to 5.5 μg 1-1. XANES, EXAFS, XRD, X-ray mapping, electron microprobe analysis and single chemical extractions suggest that As in the sediments is sequestered in sulphide (As0 in arsenopyrite and pyrite, coordinated by 1 S and 3 Fe) and in Fe oxide (AsV in arsenate, coordinated by 4 O, bound to Fe oxide and Fe sulphate, probably jarosite). The pools evolved as a result of the interaction of rainwater with the sediments, and As concentrations are controlled by evaporation and by the amount of tailings (and specifically, arsenopyrite) in the sediments that remained even after clean-up efforts. The arsenopyrite remaining in the floodplain sediment is potentially highly reactive under the prevailing pH and Eh conditions on the floodplain, and will probably continue to provide As to ephemeral pools and possibly, Agrio-Guadiamar river water. © 2005 Elsevier B.V. All rights reserved.

Ferrihydrite and goethite are amongst the most important substrates for the sorption of contaminants in soil and other environmental media. Isotopic studies of the transition elements, particularly those that exhibit more than one oxidation state and show pH- and/or redox-sensitive behaviour at low temperatures, have been shown to be potentially useful present-day and past proxies for redox (or palaeoredox) conditions. We have made preliminary investigations of Fe isotope fractionation that take place during the formation of FeIII (oxy)hydroxides (FeoxIII) from an aqueous FeIII(NO3)3 solution (FeaqIII) under laboratory conditions. We have attempted to keep the chemical system simple by excluding 'vital effects' and major changes in redox through the maintenance of abiotic conditions and use of FeaqIII. Isotopic measurements (56Fe/54Fe, 57Fe/54Fe) of the FeIII(NO3)3 stock solution, the original ferrihydrite and the mixed ferrihydrite/goethite-supernatant FeaqIII 'pairs' were carried out using a double focusing multicollector inductively coupled plasma mass spectrometer. The results reveal an apparent systematic variation indicating larger ΔFeaqIII-FeoxIII with decrease in the ferrihydrite:goethite ratio, which reflects the time allowed for isotopic exchange. These values range from virtually zero (0.03‰) after 24 h to 0.30‰ after 70 h. In each FeoxIII-FeaqIII 'pair' the lighter Fe isotope is partitioned into the FeoxIII, leaving the FeaqIII isotopically heavier. The observed fractionation reflects isotopic exchange of Fe between the FeoxIII and FeaqIII upon at least a two step transition of ferrihydrite to goethite. © 2005 the Mineralogical Society.

The Mathiatis massive sulphide deposit in Cyprus was a low-grade (0.3% Cu), three million ton ore body of pyrite and minor chalcopyrite occurring within basaltic lavas of the Troodos ophiolite. Cessation of mining in 1987 left a deep open pit surrounded by large heaps of spoil, which are undergoing oxidation and leaching. The aim of this study was to determine the mineralogical controls on the storage and potential remobilization of As, Cu, Pb and Zn within, and from, mine spoil heaps. Most of the spoil samples collected, and related materials (stream sediment, reaction zone between a boulder of massive pyrite and calcareous chert, salt crusts on stream beds), are enriched in As (27-220 ppm), Cu (110-400 ppm), Pb (10-140 ppm) and Zn (290-12,000 ppm) relative to both the basalt and calcareous chert (As 4-10 ppm, Cu 20-76 ppm, Pb 3-6 ppm, Zn 39-200 ppm). Arsenic, Cu, Pb and Zn in the spoil an d related materials are associated with Fe(-Al-S)-O, Fe(-Al-Mg)-S-O, Al(-Mg-Fe)-S-O and Mg(-Al-Fe)-S-O phases (the brackets represent minor components of less than 20 wt.% within the phases). Chemical extraction work using CaCl2 suggests that Cu, Zn and to some extent, As, are potentially more soluble than Pb. This is corroborated by the very high total concentrations of Cu and Zn in both the secondary salt crusts and the reaction zone material, high CaCl2-extractable As, Cu and Zn in the salt crusts, and aqueous data for the Mathiatis mine area collected for a European Union LIFE report. This may have implications for ecosystem health and water quality in the Mathiatis area and areas of similar mineralogy and climate world wide. © 2005 the Mineralogical Society.

In order to reveal the intra-annual variability of the major ion composition of the Pilcomayo river, a dryland river, and its relationship to discharge, water samples were taken at regular time intervals from May 1998 until February 1999 at the town of Villa Montes (Bolivia). Water chemistry of the Pilcomayo river was highly variable during the year and strongly influenced by differences in discharge between the wet and the dry season. Halite dissolution appeared to play an important role and both Cl and Na concentrations became very high (±10 mmolL-1) during the dry season. Pyrite weathering and dissolution of gypsum, dolomite and calcite determined Ca, Mg, CO3 and SO4 chemistry. At the onset of the rainy season 'rinse out' effects occurred, resulting in marked concentration peaks especially for the least soluble ions. Possible effects on biota, such as consequences for trace metal toxicity, are discussed briefly. © 2004 Elsevier Ltd. All rights reserved.

The ability to extract arsenic (As) from soils and sediments, and analyze it with accuracy and precision, is of paramount importance, given the high risk that As, even in relatively low concentrations, poses to pore waters and biota. A large number of methods exist for extracting and analyzing total As, and As associated with a variety of operationally defined phase associations, in soils and sediments. We give an overview of methods used at present, and consider potential problems. We strongly recommend adoption of universal standard techniques and certified reference materials, especially for sequential extraction schemes. © 2004 Elsevier Ltd. All rights reserved.

The Río Pilcomayo heads on the Cerro Rico de Potosí precious metal-polymetallic tin deposits of Southern Bolivia. Mining of the Potosí deposits began in 1545 and has led to the severe contamination of the Pilcomayo's water and sediments for at least 200 km downstream of the mines. This investigation addresses the potential human health affects of metal and As contamination on four communities located along the upper Río Pilcomayo by examining the potential significance of human exposure pathways associated with soils, crops and water (including river, irrigation and drinking water supplies). The most significantly contaminated agricultural soils occur upstream at Mondragón where Cd, Pb and Zn concentrations exceed recommended guideline values for agricultural use. Further downstream the degree of contamination decreases, and metal concentrations are below Dutch, German and Canadian guideline values. Metal and As concentrations in agricultural products from the four communities were generally below existing guidelines for heavy metal content in commercially-sold vegetables. Thus, the consumption of contaminated produce does not appear to represent a significant exposure pathway. A possible exception is Pb in carrots, lettuce and beetroots from Sotomayor and Tuero Chico; 37% and 55% of the samples, respectively, exceeded recommended guidelines. Most communities obtain drinking water from sources other than the Río Pilcomayo. In general, dissolved concentrations of metals and As in drinking water from the four studied communities are below the WHO guideline values with the exception of Sb, which was high at Tasapampa. The inadvertent ingestion of contaminated water from irrigation canals and the Río Pilcomayo represents a potential exposure pathway, but its significance is thought to be minimal. Given the degree of soil contamination in the area, perhaps the most significant exposure pathway is the ingestion of contaminated soil particles, particularly particles attached to, and consumed with vegetables. The risks associated with this pathway can be reduced by thoroughly washing or peeling the vegetables prior to consumption. Other exposure pathways that are currently under investigation include the consumption of contaminated meat from livestock and poultry, which drink polluted waters and the ingestion of contaminated wind-blown dust. © 2003 Elsevier B.V. All rights reserved.

In this article, we probe the causes behind the unconventional spin glass state of the kagomé antiferromagnet hydronium jarosite, (H 3O)Fe3(SO4)2(OH)6, by study of the lead based compounds PbFe3(AsO4)(SO 4)2(OH)6, Pb(Fe,Cu)3(SO 4)2(OH)6, and Pb0.5Fe 3(SO4)2(OH)6. DC susceptibility measurements indicate that the glassy state is dependent on segregated layers of H3O+ ions in the crystal structure. © 2004 Elsevier B.V. All rights reserved.

In order to investigate the mechanism of As release to anoxic ground water in alluvial aquifers, the authors sampled ground waters from 3 piezometer nests, 79 shallow (80 m) wells, in an area 750 m by 450 m, just north of Barasat, near Kolkata (Calcutta), in southern West Bengal. High concentrations of As (200-1180 μgL-1) are accompanied by high concentrations of Fe (3-13.7 mgL-1) and PO4 (1-6.5 mgL-1). Ground water that is rich in Mn (1-5.3 mgL-1) contains

Heavy metal-bearing sediment particles enter river systems by discharge of mine or processing waste, tailings dam failures, remobilization of mining-contaminated alluvium and mine drainage. The mineralogy and geochemistry of these particles is dependent upon the original ore mineralogy, and on processes that have occurred in the source areas, during transport and deposition and during post-depositional early diagenesis. This paper reviews the research carried out to date on the sources, mineralogy, chemistry and fate of heavy metal-bearing particles in mining-affected river systems, and identifies six important avenues for further investigation.

The Aznalcóllar tailings dam at Boliden Apirsa's Aznalcóllar/Los Frailes Ag-Cu-Pb-Zn mine 45 km west of Seville, Spain, was breached on 25 April 1998, flooding approximately 4600 hectares of land along the Ríos Agrio and Guadiamar with approximately 5.5 million m3 of acidic water and 1.3×106 m3 of heavy metal-bearing tailings. Most of the deposited tailings and approximately 4.7×106 m3 of contaminated soils were removed to the Aznalcóllar open pit during clean-up work undertaken immediately after the spill until January 1999. Detailed geomorphological and geochemical surveys of the post-clean-up channel, floodplain and valley floor, and sediment and water sampling, were carried out in January and May 1999 at 6 reaches representative of the types of river channel and floodplain environments in the Río Guadiamar catchment affected by the spill. The collected data show that the clean-up operations removed enough spill-deposited sediment to achieve pre-spill metal (Ag, As, Cd, Cu, Pb, Sb, Tl, Zn) concentrations in surface sediment. These concentrations, however, are still elevated above pre-mining concentrations, and emphasise that mining continues to contaminate the Agrio-Guadiamar river system. Dilution by relatively uncontaminated sediment appears to reduce metal concentrations downstream but increases in metal and As concentrations occur downstream, presumably as a result of factors such as sewage and agriculture. River water samples collected in May 1999 have significantly greater dissolved concentrations of metals and As than those from January 1999, probably due to greater sulphide oxidation from residual tailings with concomitant release of metals in the warmer early summer months. These concentrations are reduced downstream, probably by a combination of dilution and removal of metals by mineral precipitation. Single chemical extractions (de-ionised water, CaCl2 0.01 mol l-1, CH3COONH4 1 M, CH3COONa 1 M and ammonium oxalate 0.2 M) on alluvial samples from reaches 1 and 6, the tailings, pre-spill alluvium and marl have shown that the order of sediment-borne contaminant mobility is generally Zn>Cd>Cu>Pb>As. Pb and As are relatively immobile except possibly under reducing conditions. Much of the highly contaminated sediment remaining in the floodplain and channel still contains a large proportion of tailings-related sulphide minerals which are potentially reactive and may continue to release contaminants to the Agrio-Guadiamar river system. Our work emphasises the need for pre-mining geomorphological and geochemical data, and an assessment of potential contributions of contaminants to river systems from other, non-mining sources. © 2003 Elsevier Science Ltd. All rights reserved.

Waste materials from mining of the Cerro Rico de Potosi precious metal-polymetallic tin deposits of southern Bolivia have been released to the headwaters of the Rio Pilcomayo for the past 450 years, resulting in extensive contamination of water, sediments and soils along the upper reaches of the river. This study uses isotopic data to identify the primary sources of Pb to the aquatic environment, and the relative contributions of each source to pre and post-mining alluvial deposits. Prior to the onset of mining activities in 1545, alluvial sediments along the Rio Pilcomayo were dominated by Pb from the underlying bedrock and from mineralized rocks exposed at the surface of Cerro Rico. Mining and milling operations at Cerro Rico released a new source of Pb to the river that can be traced downstream for at least 200 km. Simple mixing models suggest that Pb from the mines comprise between 30 and 89% of the Pb in the modern channel bed sediment. However, these estimates may be low because the isotopic composition of the contaminant source was based on samples of ore deposits rather than mill tailings, the latter of which contain fragments of both ore and host rock.

The Río Pilcomayo rises on the Cerro Rico de Potosí precious metal-polymetallic tin deposits of Bolivia, and flows in a southeasterly direction for ca. 600 km to Bolivia's southern border with Argentina. Mining of the Potosí deposits has occurred continuously since 1545, generating large quantities of waste materials in the headwater of the basin. In addition, a tailings dam breach at the Porco mine in 1996 released an estimated 235 000 m3 of tailings and fluid into the upper reaches of the Río Pilaya, the largest tributary to the Pilcomayo. Concentrations of As, Sb, Cd, Cu, Pb, Hg, Ag, Tl and Zn in contemporary channel sediments upstream of the Pilaya confluence are significantly elevated above background values. Elevated levels appear to be associated with pyrite- and other sulphide mineral-bearing tailings materials transported more than 200 km downstream of the Potosí mines. Significant downstream declines in elemental concentrations occur within 15 km, and again between 150 and 200 km, from the mines. The initial decrease in concentrations is due to the rapid dilution of nearly pure tailings effluent released to the river from milling facilities near Potosí. The latter decrease results from a combination of geomorphic processes including the storage of sediment-borne metals within the channel bed and the influx of 'clean' sediment from several large tributaries. Downstream of the Pilaya confluence, concentrations of Cu, Pb, Hg and Zn are only slightly elevated above background values, and Ag, Cd, Sb and Tl cannot be distinguished from background levels. These data suggest that while the Porco tailings spill may have had a significant short-term impact on sediment and water quality along the lower reaches of the Río Pilcomayo, its longer-term impacts were limited. Metals stored and eroded from alluvial deposits of historical age in upstream reaches appear to be an important source of metals to the river today. An additional, and perhaps more significant source, is the release of tailings effluent to the river from modem milling operations. The transport of these contaminants downstream of Icla (203 km from Potosí) appears to be restricted by aggradational processes occurring in the vicinity of Puente Sucre. In addition, downstream of the confluence of the Río Pilaya, inputs of large amounts of 'clean' sediment have caused dilution of the metal contaminants. Data from other studies where similar geomorphic processes have occurred suggest that the metals in the upper Pilcomayo may eventually be moved downvalley as the aggradational processes are reversed and channel stabilisation occurs. Thus, the most significant impacts of metal contamination may not be realised in downstream areas for decades. © 2001 Elsevier Science B.V. All rights reserved.

Geomorphological, geochemical and geochronological investigations of Holocene fluvial sedimentary sequences have been undertaken within a range of upland, piedmont and lowland valley floor reaches in the Yorkshire Ouse catchment, northern England. The aims of these studies have been to: (a) evaluate the effects of prehistoric and historic land-use change on catchment erosion and sediment delivery to river channels and floodplains; (b) establish the degree to which episodes of river erosion and sedimentation are controlled by climate-related variations in flood regime; and (c) assess the spatial heterogeneity of river response to environmental change and how this is likely to influence short- and long-term sediment storage, as well as sediment transfer to the Humber Estuary. Similar discontinuities in the Holocene alluvial record are evident at many sites in the Yorkshire Ouse catchment, though local differences in river sensitivity to externally imposed change have resulted in a complicated and often unique relationship between river behaviour and environmental change. The large proportion of particulate-borne contaminant metals (resulting predominantly from historical mining) stored in the Vale of York strongly indicates that sediment delivery from the Ouse catchment to the Humber Estuary during the Holocene may have been relatively low. This suggests that the degree of connectivity between river, estuarine and coastal transport systems, as well as spatial and temporal variations in fluvial sediment storage, are the key controls of long-term land-ocean sediment fluxes.

This paper provides the first radiometrically dated evidence of Holocene alluvial landform development in Upper Wharfedale, Yorkshire Dales. Four river terraces are identified. Terraces 1 and 2 are closely linked to Late Devensian and early Holocene environmental change, with gravel reworked from local glacial and periglacial sources prior to cementation by carbonate-rich waters. U-series dating of cement provides age estimates for cementation of between ca. 5.1-7.4 kyr BP for Terrace 1 and ca. 3.6->8.0 kyr BP for Terrace 2. U-series dating of tufas overlying Terraces 1 and 2 produced ages of ca. 4.2-4.5 kyr BP and ca. 2.1-2.2 kyr BP respectively, and provide upper age limits for terrace formation. Terrace 3 marks a change in sediment calibre, supply and sedimentation style, and 14C dating suggests that the principal source of fine-grained material may be agricultural expansion in the Yorkshire Dales from ca. AD 600 (1350 cal. yr BP). Radiocarbon dates indicate that Terrace 4 was deposited from the eleventh century, with initiation of the contemporary floodplain between the fifteenth and seventeenth centuries AD. Both these lowest units contain sediments contaminated with heavy metals as a result of mining activities within the catchment. The evidence presented in this study is comparable to that of research undertaken in upland environments elsewhere in northern and western Britain, thereby adding to the corpus of information currently available for evaluating the fluvial geomorphological response to climate and vegetation change during the Holocene. Copyright (C) 2000 John Wiley and Sons, Ltd.

Holocene alluvial sediment sequences and floodplain geomorphological histories from three valley-floor sequences in the Yorkshire Ouse Basin have been determined using a variety of field evidence and laboratory methods: geomorphological mapping, sediment coring and trenching, physical and chemical analysis of sedimentary units, and 14C dating. The application of multiple methods has revealed contrasting phases of fiver erosion, alluviation and depositional styles during the Late Quaternary at each of the individual study reaches. The gravel-bedded River Swale at Catterick has been characterized by progressive valley-floor incision during the late Holocene with major phases of incision occurring during the cooler and wetter phase of the 'Little Ice Age'. Within the last c. 245 years, substantial thicknesses (up to 2 m) of overbank alluvium contaminated by metalliferous mining have been deposited across the floodplain. In contrast, floodplain development in the lower reaches of the River Swale at Myton and the River Aire at Beal has predominantly been one of relative channel stability and vertical aggradation. Here, low floodplain gradients, wide valley floors, stable channels and limited lateral floodplain erosion have combined to produce thick (c. 10 m) sequences of fine-grained alluvium deposited in overbank environments. Mining-related contamination in lowland floodplains is much lower than at Catterick with limited amounts of historically contaminated alluvium being deposited across the floodplain. Although environmental change has been important in controlling Holocene floodplain development, the upper and lower reaches of the Yorkshire Ouse basin have responded differently to these effects because of reach-scale geomorphic controls. Caution needs to be applied before relating broad-scale environmental change to river response across a whole fiver basin.

Floodplain overbank sediments are often used to evaluate the influence of environmental change on sediment and chemical fluxes within river basins. This paper presents the results of an investigation of heavy metal storage in seven floodplain reaches in the Yorkshire Ouse basin in north-east England. Floodplain heavy metal storage has been greatest since c. 1750, and many of the post-1750 sedimentary units exhibit heavy metal values that exceed recommended trigger and guideline values for contaminated land. Relatively high heavy metal storage occurs from AD 1250-1750 in most of the reaches. These patterns are related to 2000 years of Pb and Zn mining in the Yorkshire Dales and c. 250-300 years of industrial and urbanization activity around Leeds and Bradford, and increased delivery of fine-grained sediment during the last millennium, possibly owing to factors such as population growth and agricultural expansion during the Middle Ages, and climate change during the Little Ice Age.

The City of York in northern England has a long history of being flooded by the River Ouse. Excavations of a 9 m sedimentary profile were carried out by the York Archaeological Trust on the site of a pumping station associated with a flood prevention scheme at North Street on the south-west bank of the River Ouse. This profile records evidence of human activity and episodic river sedimentation over a period from the 2nd to the 14th century AD. Anthropogenic materials in the profile include waterfront timber and wattle structures, and dumps of organic domestic debris and industrial waste. Evidence of historic floods is preserved in interleaved alluvial deposits. This study reports on the degree of lead (Pb) contamination at the site from Roman to Mediaeval times and the sources of both alluvial and manufactured lead deposited in the profile. Archaeological, sedimentological, geochemical and mineralogical evidence suggest that Yorkshire Dales mining activity during the 9th-13th centuries AD may have both directly and indirectly caused lead contamination of the alluvial deposits at North Street.

The Rio Tinto in SW Spain drains Cu and pyrite mines which have been in operation since at least the Bronze Age. Extensive metal mining, especially from 1873 to 1954, has resulted in contamination of the Rio Tinto alluvium with As, Cu, Pb, Ag and Zn. X-ray diffraction (XRD), wavelength-dispersive X-ray mapping, scanning electron microscope petrography and X-ray energy-dispersive (EDX) analysis has revealed that 4 major groups of contaminant metal and As-bearing minerals, including sulphides, Fe-As oxides, Fe oxides/hydroxides/oxyhydroxides, and Fe oxyhydroxysulphates, occur in the alluvium. Sulphide minerals, including pyrite, chalcopyrite, arsenopyrite and sphalerite, occur in alluvium near the mining areas. Iron hydroxides and oxyhydroxides such as goethite and possibly ferrihydrite occur in cements in both the mining areas and alluvium downstream, and carry minor amounts of As, Cu and Zn. Iron oxyhydroxysulphates; including jarosite, plumbojarosite and possibly schwertmannite, are the most common minerals in alluvium downstream of the mining areas, and are major hosts of Cu, Pb, Zn and of As, next to the Fe-As minerals. This work, and other field observations, suggest that (1) the extreme acidity and elevated metal concentrations of the river water will probably be maintained for some time due to oxidation of pyrite and other sulphides in the alluvium and mine-waste tips, and from formation of secondary oxide and oxyhydroxysulphates; (2) soluble Fe oxyhydroxysulphates such as copiapite, which form on the alluvium, are a temporary store of contaminant metals, but are dissolved during periods of high rainfall or flooding, releasing contaminants to the aqueous system; (3) relatively insoluble Fe oxyhydroxysulphates and hydroxides such as jarosite and goethite may be the major long-term store of alluvial contaminant metals; and (4) raising river pH will probably cause precipitation of Fe oxyhydroxides and oxides/hydroxides/oxyhydroxides and thus have a positive effect on water quality, but this action may destabilise some of these contaminant metal-bearing minerals, releasing metals back to the aqueous system.

Metals such as Pb, Zn, Cd and Cu from historical mining activity have been used as stratigraphic markers for dating and provenancing vertically accreted, fine-grained floodplain overbank deposits. This study presents evidence for chemical remobilization of these metals within overbank sediments in the Tyne basin, UK. The evidence includes: breakdown of metal-bearing minerals (sulphides, carbonates, iron and manganese oxyhydroxides); shifts of chemical fractions within zones of relatively low pH towards more soluble and reactive phases; and accumulation of secondary iron and manganese oxyhydroxides at levels related to fluctuating water-table levels or to the breakdown of organic matter. All of this suggests that fine, centimetre-scale, chemostratigraphy using metal concentrations and ratios is unlikely to provide reliable data in river systems that have experienced, or are experiencing, major changes in water-table levels, or pedogenesis. Coarse tens of centimetre- to metre-scale, chemostratigraphy, when applied with caution, may still provide a means of delineating contaminated units.

Historic metal mining has greatly influenced sediment delivery and metal contamination in the Tees River Basin. Investigations of metal-contaminated overbank river sediment show that sediment-borne metal concentrations decrease downstream of mining areas. Metalliferous mineralogy also changes: sulphides and carbonates are abundant in the upstream part of the basin, and both decline and disappear downstream where iron oxyhydroxides dominate. Mineral compositional and textural information can be used to trace sources of mining-related contaminated sediment. Sulphides, carbonates, and oxyhydroxides which pseudomorph ore deposit minerals, are interpreted to be derived from outcropping ore bodies and mine-waste tips. The relative abundance of these grains suggests that the ore bodies and mine-waste tips are still important sources of metal pollutants. This is corroborated by morphological mapping and coring of Tees floodplain sequences, which also suggests that metal-contaminated alluvium downstream has experienced limited re-working.

Historic lead and zinc mining in the Northern Pennines, Yorkshire Dales and Peak District significantly affects water and sediment quality in river basins in the LOIS study area. Sediment-associated contaminant metals are transported, often in pulses or slugs, as suspended load under flood conditions. Although downstream decreases in metal concentrations are observed in the river systems, a substantial proportion of the metals have been incorporated into alluvial deposits. These in turn are, and will continue to act, as a major secondary source of metal contaminants over many hundreds of years. These processes need to be taken into consideration when modelling riverine metal fluxes to the North Sea, to avoid overestimation of metal contaminants from industrial and urban sources, and underestimation of contaminants from these mining-related sources.

Historic mining has produced widespread Pb, Zn, Cd, and Cu contamination in the fluvial deposits of the Tyne River Basin, northeast England. Detailed mineralogical analysis of contemporary overbank river sediment, mining-age alluvium, and mine-waste tips and of suspended solids in river waters has defined a general weathering reaction paragenesis of Pb-, Zn-,Cd-, and Cu-bearingminerals: sulfides → carbonate, silicate, phosphate, and sulfate weathering products - iron and manganese oxyhydroxides. Textural and chemical evidence suggests that the sulfides alter to carbonates in high pH/pCO2, limestone-dominated source terrains. These minerals and other contaminant metal-rich minerals such as silicates and manganese oxyhydroxides decline and disappear downstream in lower pH shale/sandstone-dominated environments. The concomitant decrease in total Pb, Zn, Cd, and Cu sediment contents in the Tyne and possibly other metal contaminated rivers may be related to these essentially chemical weathering and dispersion processes. These are augmented by physical, hydrodynamic processes that to a large extent effect dilution by premining Quaternary sediment and by uncontaminated sediment from tributaries.

The Pechenga Rift Zone is located in the northwestern part of the Kola Peninsula in Russia near the Norwegian border, where it forms part of the 100 km long early Proterozoic Polmak-Opukasjarvi-Pasvik-Pechenga-Imandra/Varzuga-Ust'Ponoy Greenstone Blet. The rift zone is by the 16 000-18 000m thick Petsamo Supergroup which is divided into the North Pechenga and South Pechenga Groups. The North and South Pechenga Groups and the lithologies, sedimentary facies and whole-rock and rare-earth element geochemistry of their Norwegian correlatives support a three-stage rift model for the Petsamo Supergroup: first, an intracontinental rift stage (2450-2100 m.y.); a transitional rift stage (2100-1970 m.y.) and both intra- and intercontinental tectonic settings and possible short-term, aborted spreading at about 1990-1970 m.y.; and, finally, a possibly collision-related intercontinental rift stage (1970-1800 m.y.). -from Authors

The Pechenga Ni-Cu deposits are located within the early Proterozoic Pechenga Rift Zone in the northwestern part of the Russian Kola Peninsula close to the Norwegian border. Differentiated, Ni-Cu ore-bearing gabbro-wehrlite intrusions and associated ultramafic flows occur in the Productive Formation, the fourth and youngest sedimentary formation of the North Pechenga Group. Similar rock assemblages are present in the correlative Norwegian Pasvik Group. The Pechenga Ni-Cu deposits formed as a result of the contamination of ferropicritic magmas by sulphur that was derived from both consolidated and unconsolidated sediments of the Productive Formation. Two phases of deformation have localized the deposits into their present position in the troughs of asymmetric synclines. -from Authors