Historic Mining Operations Research Articles

Surface Coal Mine Soils: Evidence for Chronosequence Development

Anthropogenic changes to soil properties and development can dominate soil systems, particularly in coal mining-impacted landscapes of the Appalachian region of the United States. Historical mining operations deposited spoils which are developing into mine soils in chronosequences, allowing for a correlation between emplacement age and rates of change in soil properties. The study site was in the Huff Run Watershed (Mineral City, OH, USA) with a series of eleven spoil piles that were deposited over a 30-year time period. Surface soils were analyzed for bulk density, loss on ignition (LOI) as a proxy for organic matter, particle size, and bulk mineralogical (by X-ray diffraction) and elemental (by X-ray fluorescence) compositions. The following linear trends were observed across the transect from older to younger mine soils: bulk density increased from 1.0 cm−3 to 1.5 g cm−3; LOI decreased from ~20% to 5%; the content of sand-sized particles and quartz decreased from ~50% to 30% and 50% to 25%, respectively, with a corresponding increase in the contribution of clay mineral from ~25% to 60%; and Fe and other trace metals (Cu, Ni, Pb, Sb, Sn, and Te) decreased in concentration, while Al, Mg, and K increased in concentration. These trends are likely the result of: (1) organic matter accumulation as vegetation becomes more abundant over time; (2) transport of clays out of more recently emplaced waste; and (3) oxidative dissolution of primary sulfides releasing Fe and other trace metals followed by re-precipitation of secondary Fe-phases and trace metal sequestration. The findings presented here provide insight into the future behavior of these materials and can potentially be used to assess the inferred age of previously unexamined mine soils across a wider geographic area. These results can also inform decisions related to reclamation activities and ecosystem restoration.

Epithermal Precious Metal Deposits in South Korea—History and Pursuit

Abstract The gold and silver endowment of Korea has historically been well known, with records alluding to production as far back as 1122 BC. The main gold production period was from 1925 to 1943 during the Japanese occupation of Korea, with more than 1 Moz recorded in 1939. Muguk was the most productive gold mining operation, located within the central region of South Korea, with a recorded 590 koz of gold produced from 1934 to 1998 (first mined in AD 912). The majority of the historical mining operations were closed by government order in 1943 during the Second World War and never reopened. A number of small mines operated between 1971 and 1998, with limited production during a period of gold prices generally lower than at present (~25–50% of current inflation adjusted prices, apart from a four-year period 1979–83). It is likely that significant resources remain within these historical mining areas. Gold-silver deposit types historically recognized and exploited in Korea include placers and orogenic and intrusion-related vein systems. Only more recently have epithermal vein and breccia systems been recognized. This is not surprising, given that the geologic and tectonic setting of the Southern Korean peninsula is prospective for epithermal precious metal deposits, spatially associated with basin-scale brittle fault systems in Cretaceous volcanic terranes. South Korea is an underexplored jurisdiction, with limited modern exploration and drilling until the mid-1990s, when Ivanhoe Mines Ltd. discovered the Gasado, Eunsan, and Moisan epithermal gold-silver deposits, all of which became mines. Exploration was limited for another 20 years until Southern Gold Ltd., an Australian Securities Exchange (ASX)-listed company, commenced regional-scale exploration for epithermal deposits, using a strategy similar to that successfully employed by Ivanhoe.

Mine drainage: Remediation technology and resource recovery.

Drainage from current and historic mining operations remains a persistent environmental problem. Numerous research and development efforts were made in 2019 with a goal to minimize the impact of mine drainage on the environment, while other research endeavors addressed the mine drainage issue from a different perspective, where mine drainage was considered a resource for water and valuable products, such as metals, sulfuric acid, and rare earth elements. Thus, this review has two main sections: (a) focusing on research efforts in mine drainage remediation technology, and (b) emphasizing advances in resource recovery from mine drainage. The first section covers traditional and emerging passive and active treatment technologies. The second section summarizes resource recovery efforts using various technologies, such as selective precipitation, membrane process, and biological systems. PRACTITIONER POINTS: Significant progress continued to be made in the management of mine drainage and related issues. Recent remediation technology advances in mine drainage were presented. Technologies focusing on resource recovery from mine drainage were reviewed.

Pedogenic carbonate sampling for Cu exploration on the Yorke Peninsula, South Australia

We report on the geochemistry of 215 regolith carbonate rocks collected across the Yorke Peninsula, South Australia in order to evaluate the potential of regolith carbonates as a geochemical sampling media for buried Cu mineralization. The Yorke Peninsula forms the southern part of the Olympic Domain iron-oxide‑copper‑gold (IOCG) mineral province and is host to a number of Cu-bearing mineral deposits and prospects including Hillside and the historic Moonta-Wallaroo mining district. The majority of the Yorke Peninsula is covered by a veneer of Cambrian to Quaternary sedimentary rocks and regolith, including marine limestones and regolith carbonates. We present a new regolith map of the Yorke Peninsula derived from geophysical data and field observations and use it to provide landscape context and regional characterization of the sampled regolith materials. Whole rock geochemistry of the sampled carbonates is used to demonstrate that major element chemistry is dominated by CaO (33%–53%), reflecting the calcite component. Other major components include SiO2 and Al2O3, reflecting quartz (typically quartz sand in carbonate indurated quaternary sands) and clay minerals respectively. Ca/Sr ratios vary between 179 and 1324 with 86% of the samples <650. The Ca/Sr < 650 group of samples forms a continuous array on a plot of Ca vs Sr which overlaps with the range of values expected from sea water derived Ca and Sr subjected to variable degrees of meteoric fractionation. These samples are interpreted to be regolith carbonates with little input of marine carbonate. A single sample has Ca/Sr 1324, consistent with a significant component of marine limestone. Twenty nine samples have Ca/Sr >650 and <940 which may indicate mixing of dominantly meteoric sources with a lesser component of marine carbonate. We recommend that geochemical results from samples with Ca/Sr >650 be treated with caution as the regolith carbonate trace element geochemical signal may be diluted by the marine carbonate component. Copper concentrations found in the carbonate rocks with Ca/Sr <650 range from 1.4 ppm to 36 ppm and form a slightly right-skewed, near log normal population. Samples with elevated log10Cu concentrations have a broad spatial coincidence with areas of known Cu enrichment in the basement and not related to dust or windblown contamination. Copper concentrations show no systematic relationship with common dust-born contaminants (Al2O3, Fe2O3, Zr) which would be expected if the Cu was derived from windblown spoil from the historic mining operations. We conclude that regolith carbonates are a potentially useful sampling media for Cu exploration on the Yorke Peninsula and that they can be easily differentiated from less useful marine carbonates on the basis of Ca/Sr ratios.

The Geological – Mining and Geotechnical Opinion as a Supplement to the Geotechnical Documentation in a Region of the Past Underground Mining

The purpose of a geological-mining report and geotechnical opinion, is to provide information about historical mining operations undertaken in the site of future construction works together with the assessment of potential geotechnical risk for the planned building or structure from the point of the view of post-mining influences. Preparing of such a report should be required by the building designers and construction engineers, especially in the case when the subsidence and ground conditions are not determined and predictable enough for reliable design of foundations and other critical parameters. The authors discuss the problem of mining influences and ground conditions on buildings and ground infrastructure construction. They give the example of application of expertise algorithm on the basis of a case study from the city of Tarnowskie Gory in the southern part of Poland. The example refers to modernisation of the road and technical infrastructure on the Repecka Street, located in the area of historical mining operations. Sinkhole subsidence risk in the investigated site is the additional aspect and it is connected with the presence of soluble limestone formation under shallow loose quaternary sands. It represents geological configuration highly vulnerable for surface sinkholes.

Mobility and chemical fate of antimony and arsenic in historic mining environments of the Kantishna Hills district, Denali National Park and Preserve, Alaska

The Kantishna Hills mining district of interior Alaska, USA, located within Denali National Park and Preserve, contains a number of antimony lode deposits, including Alaska's historically largest antimony producer, the Stampede mine. Oxidative weathering of sulfidic tailings and waste rock associated with historic mining operations has impacted water quality in the region. In the Stampede and Slate Creek watersheds, antimony and arsenic concentrations in stream waters were as high as 720μg/L and 239μg/L, respectively. Antimony in all water samples is predominantly present as Sb(V), whereas arsenic was detected in varying ratios of As(III) and As(V). Based on X-ray absorption spectroscopy (XAS) measurements reduced As(III) and Sb(III) were identified in mine waste materials, whereas predominantly oxidized forms, As(V) and Sb(V), were found in downstream sediments. Elevated antimony concentrations extend for more than 8km downstream from the antimony lodes, whereas arsenic quickly attenuates within 1.5km. The difference between antimony and arsenic aqueous phase speciation suggests that antimony oxidation is more rapid than arsenic within this system. A high correlation is observed between antimony, arsenic, and iron concentrations in fine-fraction streambed sediments downstream of the source lodes. This suggests that sorption and co-precipitation with iron (hydr)oxides are important pathways for the attenuation of antimony and arsenic in these interior Alaska watersheds. Further XAS characterization of the downstream sediments corroborates these observations and indicates that antimony is adsorbed to Fe-oxide phases as inner-sphere bi-dentate edge and corner sharing complexes. The trace element redox states, as well as downstream partitioning, are mainly controlled by iron speciation based on the strong correlation between redox potentials calculated from iron (Fe(II)/Fe(III)) and arsenic (As(III)/As(V)).

Arsenic species in weathering mine tailings and biogenic solids at the Lava Cap Mine Superfund Site, Nevada City, CA

BackgroundA realistic estimation of the health risk of human exposure to solid-phase arsenic (As) derived from historic mining operations is a major challenge to redevelopment of California's famed "Mother Lode" region. Arsenic, a known carcinogen, occurs in multiple solid forms that vary in bioaccessibility. X-ray absorption fine-structure spectroscopy (XAFS) was used to identify and quantify the forms of As in mine wastes and biogenic solids at the Lava Cap Mine Superfund (LCMS) site, a historic "Mother Lode" gold mine. Principal component analysis (PCA) was used to assess variance within water chemistry, solids chemistry, and XAFS spectral datasets. Linear combination, least-squares fits constrained in part by PCA results were then used to quantify arsenic speciation in XAFS spectra of tailings and biogenic solids.ResultsThe highest dissolved arsenic concentrations were found in Lost Lake porewater and in a groundwater-fed pond in the tailings deposition area. Iron, dissolved oxygen, alkalinity, specific conductivity, and As were the major variables in the water chemistry PCA. Arsenic was, on average, 14 times more concentrated in biologically-produced iron (hydr)oxide than in mine tailings. Phosphorous, manganese, calcium, aluminum, and As were the major variables in the solids chemistry PCA. Linear combination fits to XAFS spectra indicate that arsenopyrite (FeAsS), the dominant form of As in ore material, remains abundant (average: 65%) in minimally-weathered ore samples and water-saturated tailings at the bottom of Lost Lake. However, tailings that underwent drying and wetting cycles contain an average of only 30% arsenopyrite. The predominant products of arsenopyrite weathering were identified by XAFS to be As-bearing Fe (hydr)oxide and arseniosiderite (Ca2Fe(AsO4)3O3•3H2O). Existence of the former species is not in question, but the presence of the latter species was not confirmed by additional measurements, so its identification is less certain. The linear combination, least-squares fits totals of several samples deviate by more than ± 20% from 100%, suggesting that additional phases may be present that were not identified or evaluated in this study.ConclusionsSub- to anoxic conditions minimize dissolution of arsenopyrite at the LCMS site, but may accelerate the dissolution of As-bearing secondary iron phases such as Fe3+-oxyhydroxides and arseniosiderite, if sufficient organic matter is present to spur anaerobic microbial activity. Oxidizing, dry conditions favor the stabilization of secondary phases, while promoting oxidative breakdown of the primary sulfides. The stability of both primary and secondary As phases is likely to be at a minimum under cyclic wet-dry conditions. Biogenic iron (hydr)oxide flocs can sequester significant amounts of arsenic; this property may be useful for treatment of perpetual sources of As such as mine adit water, but the fate of As associated with natural accumulations of floc material needs to be assessed.

A CRYPTICALLY ZONED AMALGAM (Au1.5-1.9Ag1.1-1.4) 2.8-3.0Hg1.0-1.2 FROM A PLACER DEPOSIT IN THE TULAMEEN - SIMILKAMEEN RIVER SYSTEM, BRITISH COLUMBIA, CANADA: NATURAL OR MAN-MADE?

We describe an unusual pattern of zoning in an amalgam of Au and Ag; it occurs as peripheral zones in a 0.3 × 0.15 mm grain in a placer deposit associated with the Tulameen – Similkameen river system, British Columbia. This amalgam formed at the expense of primary Au–Ag alloy, which is present as relics in the core: Au 54–55 Ag 45–46 (Hg-free; not zoned). Abundances of Au gradually increase outward and complement decreasing levels of Ag in the amalgam. Values of Au/Ag increase from 1.1–1.2 in the core to 1.8 at the margin of the grain. The observed range of compositions, (Au 1.50–1.87 Ag 1.06–1.40 ) ∑2.81–3.00 Hg 1.00–1.19 , is limited. Two possibilities are discussed to explain the formation of the zoned amalgam. (1) This phase could be natural, formed by reaction between primary Au–Ag alloy and a late melt or oxidizing fluid, which may have remobilized and transported Hg as a result of destabilization and oxidation of cinnabar. If so, the observed zonation would reflect an increasing activity of Au species (and decreasing activity of Ag) during crystallization. (2) This phase may have formed under supergene conditions, as a result of anthropogenic introduction of Hg into placer gravels during historic mining operations in this region; we favor this hypothesis. Zoning in the amalgam may have been controlled principally by electrochemical factors related to the process of “self-electrorefining”. Gold is more “noble” than silver, so that ions of Au probably migrated and were preferentially deposited closer to the margin of the grain. This mechanism is similar to that responsible for the “secondary” rim rich in Au (poor in Ag) in placer grains of Au–Ag alloy, as reported from other localities worldwide.

The influence of metal exposure history and ultraviolet-B radiation on benthic communities in Colorado Rocky Mountain streams

Interest in understanding the influence of ultraviolet-B (UVB; 280–320 nm) radiation in aquatic ecosystems has increased since the early 1990s. Pollution from historic mining operations coupled with physicochemical characteristics of Rocky Mountain streams that increase exposure of benthic communities to UVB provided an opportunity to examine how UVB interacted with heavy metal contamination to structure stream communities. We integrated a series of UVB addition experiments done in stream microcosms with a large-scale UVB shading experiment to test the hypothesis that effects of UVB were greater on benthic communities from metal-polluted streams than from reference streams. Microcosm experiments involved short-term exposure (7–10 d) of natural benthic macroinvertebrate communities collected from reference and metal-contaminated sites to lamp-generated UVB. In all cases, abundance decreased in UVB-treated streams compared to controls. Moreover, effects of UVB addition were significantly greater on communities from metal-polluted sites than from reference sites. The field experiment involved shading portions of the streambed from UVB for 60 d at 12 streams along a Zn gradient. Median Zn concentration at these sites ranged between 5 and 530 μg/L, and mean UVB reaching the streambed varied from 6.5 to 29.0 J/cm2. Results of the field experiment indicated that removal of UVB significantly increased total macroinvertebrate abundance and abundance of grazers, mayflies, caddisflies, Orthocladiinae midges, and the mayfly Baetis bicaudatus compared to controls. Grazer abundance was significantly greater in UVB removal treatments compared to controls, but UVB removal had no effect on algal biomass. As with the microcosm experiments, the effects of UVB removal on benthic communities were generally greater at metal-polluted sites than at reference sites. We speculate that the energetic cost of regulating metals might inhibit the ability of some organisms to repair efficiently DNA damaged by UVB exposure. Our results demonstrate that benthic communities in Colorado Rocky Mountain streams are negatively influenced by UVB radiation and that communities subjected to long-term metal exposure are more sensitive to UVB than are reference communities. As a consequence, the effects of increased UVB radiation reaching the earth’s surface might be more severe than previously considered in systems receiving multiple stressors.

Lead, zinc, and antimony contamination of the Rio Chilco-Rio Tupiza drainage system, Southern Bolivia

An intense, but localized rainfall event in February 2003, led to the severe erosion and failure of a tailings disposal impoundment at the Abarόa Antimony Mine in southern Bolivia. The failure released approximately 5,500 m3 of contaminated tailings into the Rio Chilco-Rio Tupiza drainage system. The impacts of the event on sediment quality are examined and compared to contamination resulting from historic mining operations in the headwaters of the basin. Of primary concern are contaminated floodplain soils located along downstream reaches of the Rio Tupiza which were found to contain lead (Pb), zinc (Zn), and antimony (Sb) concentrations that locally exceed Canadian, German, and Dutch guidelines for agricultural use. Spatial patterns in sediment-borne trace metal concentrations, combined with Pb isotopic data, indicate that Pb, Zn, and Sb are derived from three tributary basins draining the Abarόa, Chilcobija, and Tatasi-Portugalete mining districts. Downstream of each tributary, geographical patterns in trace metal concentrations reflect local geomorphic changes throughout the drainage system. Trace metal concentrations within the Rio Chilco decrease rapidly downstream as a result of dilution by uncontaminated sediments and storage of metal enriched particles (e.g., sulfide minerals) in the channel bed as a result of ongoing aggradation. Storage in the floodplains is limited. These processes significantly reduced the dispersal and, thus, the relative environmental affects of tailings eroded from the Abarόa Mine during the 2003 flood. In contrast, storage of Pb, Zn, and Sb in floodplains along the Rio Tupiza is significant, the majority of which is derived from historic mining operations, particularly mining within the Tatasi-Portugalete district.

Geology of the Mwadui kimberlite, Shinyanga district, Tanzania

The Mwadui pipe represents the largest diamondiferous kimberlite ever mined and is an almost perfectly preserved example of a kimberlitic crater in-fill, albeit without the tuff ring.The geology of Mwadui can be subdivided into five geological units, viz. the primary pyroclastic kimberlite (PK), re-sedimented volcaniclastic kimberlite deposits (RVK), granite breccias (subdivided into two units), the turbidite deposits, and the yellow shales listed in approximate order of formation. The PK can be further subdivided into two units—lithic-rich ash and lapilli tuffs which dominate the succession, and lithic-poor juvenile-rich ash and lapilli tuffs. The lower crater is well bedded down to at least 684 m from present surface (extent of current drill data). The bedding is defined by the presence of juvenile-rich lapilli tuffs vs. lithic-rich lapilli tuffs, and the systematic variation in granite content and clast size within much of the lithic-rich lapilli tuffs. Four distinct types of bedding have been identified in the pyroclastic deposits. Diffuse zones characterised by increased granite abundance and size, and upward-fining units, represent the dominant types throughout the deposit.Lateral heterogeneity was observed, in addition to the vertical changes, suggesting that the eruption was quite heterogeneous, or that more than one vent may have been present. The continuous nature of the bedding in the pyroclastic material and the lack of ash-partings suggest deposition from a high concentration (ejecta), sustained eruption column at times, e.g. the massive, very diffusely stratified deposits. The paucity of tractional bed forms suggest near vertical particle trajectories, i.e. a clear air-fall component, but the poorly sorted, matrix-supported nature of the deposits suggest that pyroclastic flow and/or surge processes may also have been active during the eruption.Available diamond sampling data were examined and correlated with the geology. Data derive from the old 120 (37 m), 200 (61 m), 300 (92 m) and 1200 ft (366 m) levels, pits sunk during historical mining operations, drill logs, as well as more recent bench mapping. Correlating macro-diamond sample data and geology shows a clear relationship between diamond grade and lithology. Localised enrichment and dilution of the primary diamond grade has taken place in the upper reworked volcaniclastic deposits due to post-eruptive sedimentary in-fill processes. Clear distinction can be drawn between upper (re-sedimented) and lower (pyroclastic) crater deposits at Mwadui, both from a geological and diamond grade perspective.Finally, an emplacement model for the Mwadui kimberlite is proposed. Geological evidence suggests that little or no sedimentary cover existed at the time of emplacement. The nature of the bedding within the pyroclastic deposits and the continuity of the bedding in the vertical dimension suggest that the eruption was continuous, but that the eruption column may have been heterogeneous, both petrologically as well as geometrically. Volcanic activity appears to have ceased thereafter and the crater was gradually filled with granite debris from the unstable crater walls and re-sedimented volcaniclastic material derived from the tuff ring.The Mwadui kimberlite exhibits marked similarities compared to the Orapa kimberlite in Botswana.

Geology of the Mwadui kimberlite, Shinyanga district, Tanzania

The Mwadui pipe represents the largest diamondiferous kimberlite ever mined and is an almost perfectly preserved example of a kimberlitic crater in-fill, albeit without the tuff ring. The geology of Mwadui can be subdivided into five geological units, viz. the primary pyroclastic kimberlite (PK), re-sedimented volcaniclastic kimberlite deposits (RVK), granite breccias (subdivided into two units), the turbidite deposits, and the yellow shales listed in approximate order of formation. The PK can be further subdivided into two units—lithic-rich ash and lapilli tuffs which dominate the succession, and lithic-poor juvenile-rich ash and lapilli tuffs. The lower crater is well bedded down to at least 684 m from present surface (extent of current drill data). The bedding is defined by the presence of juvenile-rich lapilli tuffs vs. lithic-rich lapilli tuffs, and the systematic variation in granite content and clast size within much of the lithic-rich lapilli tuffs. Four distinct types of bedding have been identified in the pyroclastic deposits. Diffuse zones characterised by increased granite abundance and size, and upward-fining units, represent the dominant types throughout the deposit. Lateral heterogeneity was observed, in addition to the vertical changes, suggesting that the eruption was quite heterogeneous, or that more than one vent may have been present. The continuous nature of the bedding in the pyroclastic material and the lack of ash-partings suggest deposition from a high concentration (ejecta), sustained eruption column at times, e.g. the massive, very diffusely stratified deposits. The paucity of tractional bed forms suggest near vertical particle trajectories, i.e. a clear air-fall component, but the poorly sorted, matrix-supported nature of the deposits suggest that pyroclastic flow and/or surge processes may also have been active during the eruption. Available diamond sampling data were examined and correlated with the geology. Data derive from the old 120 (37 m), 200 (61 m), 300 (92 m) and 1200 ft (366 m) levels, pits sunk during historical mining operations, drill logs, as well as more recent bench mapping. Correlating macro-diamond sample data and geology shows a clear relationship between diamond grade and lithology. Localised enrichment and dilution of the primary diamond grade has taken place in the upper reworked volcaniclastic deposits due to post-eruptive sedimentary in-fill processes. Clear distinction can be drawn between upper (re-sedimented) and lower (pyroclastic) crater deposits at Mwadui, both from a geological and diamond grade perspective. Finally, an emplacement model for the Mwadui kimberlite is proposed. Geological evidence suggests that little or no sedimentary cover existed at the time of emplacement. The nature of the bedding within the pyroclastic deposits and the continuity of the bedding in the vertical dimension suggest that the eruption was continuous, but that the eruption column may have been heterogeneous, both petrologically as well as geometrically. Volcanic activity appears to have ceased thereafter and the crater was gradually filled with granite debris from the unstable crater walls and re-sedimented volcaniclastic material derived from the tuff ring. The Mwadui kimberlite exhibits marked similarities compared to the Orapa kimberlite in Botswana.

Aminolevulinic acid dehydratase activity in American dippers (Cinclus mexicanus) from a metal‐impacted stream

Blood samples collected from adult and nestling American dippers (Cinclus mexicanus) along the Arkansas River (CO, USA), a stream impacted by discharges from historical mining operations, and a reference stream were analyzed for lead concentration and delta-aminolevulinic acid dehydratase (ALAD) activity. Median ALAD activities of adult and nestling dippers from the Arkansas River were found to be significantly different from median ALAD activities of reference adults and nestlings (p = 0.002 and p = 0.028). Median ALAD activity for adult dippers from the Arkansas River was more than 50% lower relative to reference adults and activity approached a level close to 50% lower in nestlings from the same site. Median blood lead concentrations from adult (range 15.4-386.0 ppb) and nestling (range 12.1-323.0 ppb) dippers from the Arkansas River were found to be significantly different from median blood lead concentrations of reference adult (range 4.2-29.6 ppb) and nestling (range 4.2-8.2 ppb) dippers (p < 0.001 and p = 0.011). The median hematocrit level in adult dippers did not vary between sites (p = 0.73), whereas the median hematocrit level of nestling dippers from the reference site was significantly lower compared to Arkansas River nestlings (p = 0.042). Blood lead concentration in both adult and nestling dippers was found to be significantly correlated with invertebrate lead concentration (r = 0.81, p < 0.001 and r = 0.62, p = 0.01, respectively). Highly significant negative correlations were observed between blood lead concentration and ALAD activity in both adult and nestling dippers (r = -0.86, p < 0.001 and r = -0.84, p < 0.001, respectively). This study suggests that dippers (both adults and nestlings) from the Arkansas River have significantly lower ALAD activity and significantly higher blood lead concentrations compared to reference values. The measurement of ALAD activity may be a sensitive and accurate biomarker for environmental lead exposure in dippers.

Late Holocene channel and floodplain development in a wandering gravel-bed river: the River South Tyne at Lambley, northern England

Geomorphological analyses of the morphology, lithostratigraphy and chronology of Holocene alluvial fills in a 2.75 km long piedmont reach of the wandering gravel-bed River South Tyne at Lambley in Northumberland, northern England, have identified spatial and temporal patterns of late Holocene channel and floodplain development and elucidated the relationship between reach- and subreach-scale channel transformation and terrace formation. Five terraced alluvial fills have been dated to periods sometime between c. 1400 BC-AD 1100, AD 1100-1300, AD 1300-1700, AD 1700-1850 and from AD 1850 to the present. Palaeochannel morphology and lithofacies architecture of alluvial deposits indicate that the past 3000 years has been characterized by episodic channel and floodplain change associated with development and subsequent recovery of subreach-scale zones of instability which have been fixed in neither time nor space. Cartographic and photographic evidence spanning the past 130 years suggests channel transformation can be accomplished in as little as 50 years. The localized and episodic nature of fluvial adjustment at Lambley points to the operation of subreach-scale controls of coarse sediment transfers. These include downstream propagation of sediment waves, as well as internal controls imposed by differing valley floor morphology, gradient and boundary materials. However, the preservation of correlated terrace levels indicates that major phases of floodplain construction and entrenchment have been superimposed over locally complex patterns of sediment transfer. Reach-scale lateral and vertical channel adjustments at Lambley appear to be closely related to climatically driven changes in flood frequency and magnitude, with clusters of extreme floods being particularly important for accomplishing entrenchment and reconfiguring the pattern of localized instability zones. Confinement of flood flows by valley entrenchment, and contamination of catchment river courses by metal-rich fine sediments following recent historic mining operations, have combined to render the South Tyne at Lambley increasingly sensitive to changes in flood regimes over the past 1000 years. Copyright (C) 2000 John Wiley and Sons, Ltd.

Microbiological and Geochemical Characterization of Fluvially Deposited Sulfidic Mine Tailings

The fluvial deposition of mine tailings generated from historic mining operations near Butte, Montana, has resulted in substantial surface and shallow groundwater contamination along Silver Bow Creek. Biogeochemical processes in the sediment and underlying hyporheic zone were studied in an attempt to characterize interactions consequential to heavy-metal contamination of shallow groundwater. Sediment cores were extracted and fractionated based on sediment stratification. Subsamples of each fraction were assayed for culturable heterotrophic microbiota, specific microbial guilds involved in metal redox transformations, and both aqueous- and solid-phase geochemistry. Populations of cultivable Fe(III)-reducing bacteria were most prominent in the anoxic, circumneutral pH regions associated with a ferricrete layer or in an oxic zone high in organic carbon and soluble iron. Sulfur- and iron-oxidizing bacteria were distributed in discrete zones throughout the tailings and were often recovered from sections at and below the anoxic groundwater interface. Sulfate-reducing bacteria were also widely distributed in the cores and often occurred in zones overlapping iron and sulfur oxidizers. Sulfate-reducing bacteria were consistently recovered from oxic zones that contained high concentrations of metals in the oxidizable fraction. Altogether, these results suggest a highly varied and complex microbial ecology within a very heterogeneous geochemical environment. Such physical and biological heterogeneity has often been overlooked when remediation strategies for metal contaminated environments are formulated.

Mercury concentrations in surface waters from fluvial systems draining historical precious metals mining areas ink southeastern U.S.A.

This study evaluates several southern Appalachian Piedmont mining districts for Hg contamination in surface waters and determines potential relationships between Hg discharged from historical mining operations and site-specific physical factors. Water samples were collected from 3 fluvial systems that drain areas where Hg was used to amalgamate Au from ore during the 19th century. Each of the fluvial systems exhibit similar physical characteristics such as climate, vegetation, and rock type. Total Hg (Hg T) determinations were made using cold vapour atomic fluorescence spectroscopy techniques. Concentrations of Hg T in the southern Appalachian Piedmont range from 1–3 ng l −1 in waters of the Arbacoochee, Alabama, and South Mountains, North Carolina, Mining Districts to 13 ng l −1 in waters of the Dahlonega Mining District in Georgia. The correlation between Hg T and total suspended solids (TSS) at the southern Appalachian sites was good with a coefficient of determination ( r 2) of 0.82. A clear trend between environmentally-available Fe (Fe E) and Hg T ( r 2=0.86) was also evident. The correlation between Hg T and Fe E most likely reflects similarities in the mechanisms that control the aqueous concentrations of both metals (i.e., the particle-reactive nature of the two elements), allowing for the sorption of Hg onto Fe-oxyhydroxides. Hence, increased loads of TSS from erosional events are probably responsible for higher stream water Hg T concentrations. Vegetation at these sites, which is heavy due to the warm, humid climate of the SE, may help reduce the total amount of Hg released from contaminated mining sites to the rivers by controlling erosion, hence, decreasing the input of contaminated particles into streams and rivers. These southern Appalachian mining sites used Hg amalgamation techniques similar to those used in other precious metals mining districts, such as the highly contaminated Comstock Au–Ag district in Nevada, yet Hg T concentrations are orders of magnitude lower; This difference in concentration between the southern Appalachian districts and the Comstock district may correlate to the relative amounts of Hg that were used in each. However, other variables were evaluated to determine if physio-chemical differences such as climate could influence Hg T concentrations in surface waters of the two areas.

Integrated laboratory and field approach for assessing impacts of heavy metals at the Arkansas River, Colorado

AbstractThis research employed an integrated laboratory and field approach to assess effects of heavy metals at the Arkansas River, a Colorado stream impacted by historic mining operations. Ambient metal levels, chronic toxicity, metal bioaccu‐mulation by benthic organisms, and benthic community structure were examined at stations located upstream and downstream from California Gulch (CG), a U.S. Environmental Protection Agency Superfund site near Leadville, Colorado. Although each approach demonstrated effects of metals from CG, important differences among approaches were observed. Ambient metal concentrations and chronic toxicity tests conducted with Ceriodaphma dubia indicated reduced water quality at upstream and downstream stations. Because of temporal variability in metal levels, water samples collected for chronic toxicity tests did not reflect average exposure conditions. Instream monitoring of benthic communities was necessary to characterize metal impacts at the Arkansas River, but this approach had limitations. Levels of metals in periphyton and benthic invertebrates were significantly elevated at stations downstream from CG. Variation in metal levels among taxa and the absence of some taxa from some stations may limit the use of bioaccumulation studies for monitoring metal impacts. Benthic community structure was altered downstream from CG, but some metrics (e.g., species richness, abundance) were not affected by heavy metals because of the replacement of sensitive taxa by tolerant taxa. Because each of the approaches employed in this study provided different information on the degree of metal impacts, we recommend an integrated approach for assessing effects of metals on streams.

Bioaccumulation of heavy metals by benthic invertebrates at the arkansas river, colorado

AbstractA one‐year biomonitoring study was conducted to determine the extent of metal contamination (Cd, Cu, and Zn) in a benthic community from the Arkansas River (CO), a subalpine stream impacted by discharges from historic mining operations. Elevated concentrations of metals in water were paralleled by higher concentrations in benthic organisms. Significant differences (p &lt; 0.05) in metal concentrations in aufwuchs and benthic macroinvertebrates among upstream (reference) and downstream (impacted) stations were observed. Metal concentrations in aufwuchs and benthic invertebrates remained elevated at some downstream stations, despite decreases in water concentrations. Time of year and functional group contributed to the variation in metal bioaccumulation in benthic macroinvertebrates. Monitoring metal concentrations in aquatic macroinvertebrates was a better indicator of metal bioavailability in the Arkansas River than ambient (water) metal concentrations.