Mine Adits Research Articles

The role of surface water and mine groundwater in the chemical stratification of an acidic pit lake (Iberian Pyrite Belt, Spain)

• The lake is made up by mine groundwater and surface water and is in hydraulic balance. • The different sources of recharge at lake cause the meromixis in spite of little depth. • In winter the runoff inflow thickens mixolimnion and the system losses groundwater. • In summer the evaporation slims mixolimnion and the lake gains groundwater. • A conceptual model explaining its seasonal limnological evolution is advanced. The hydraulic system of the Concepción mine is made up of an open pit and an underground mine, which are currently flooded and hydraulically connected. The Concepción pit lake has shown permanent chemical stratification (meromictic lake), where two layers with different density and chemical composition can be differentiated: (i) a thick superficial layer of 11 ± 2 m deep, with a low concentration of dissolved solids (mixolimnion) and (ii) a thin bottom layer from 11 ± 2 m to 16 m deep (monimolimnion), exhibiting vertical changes in its physico-chemical parameters, with decreasing redox potential and increasing T, pH and dissolved solids content with depth. The distribution of the Concepción pit lake layers depends on recharge processes and the loss of water from the system. In winter, rainfall and runoff result in a rapid increase of lake levels. The lake regains its initial level whenever water is lost through an old mine adit, since galleries and shafts act as preferential pathways for inflowing and outflowing water. This network is connected to the bottom of the lake, resulting in the progressive downward movement of the chemocline. Furthermore, runoff generates a less dense superficial layer, which triggers the development of an ephemeral chemocline in the mixolimnion. In summer, the mixolimnion loses water by evaporation which is partially compensated by groundwater inflowing from the lake bottom, resulting in the upward movement of the permanent chemocline. During this period the water level in the system is below the outlet level, which therefore renders the outflow of water inactive. During this stage, the mixolimnion remains homogeneous and the shallow chemocline disappears. Taking into consideration the hydrochemical characteristics of this pit lake and the spatial distribution of the layers identified, a model that explains its seasonal limnological evolution is presented.

Impact of uranium mines closure and abandonment on groundwater quality

The aim of the study is to assess the evolving mine water quality of closed uranium mines (abandoned between 1958 and 1992) in the Czech Republic. This paper focuses on the changes in mine water quality over time and spatial variability. In 2010, systematic monitoring of mine water quality was performed at all available locations of previous uranium exploitation. Gravity flow discharges (mine adits, uncontrolled discharges) or shafts (in dynamic state or stagnating) were sampled. Since the quality of mine water results from multiple conditions-geology, type of sample, sampling depth, time since mine flooding, an assessment of mine water quality evolution was done taking into account all these conditions. Multivariate analyses were applied in order to identify the groups of samples based on their similarity. Evaluation of hydrogeochemical equilibrium and evolution of mine waters was done using the Geochemist's Workbench and PHREEQC software. The sampling proved that uranium concentrations in mine waters did not predominantly exceed 0.45 mg/L. In case of discharges from old adits abandoned more than 40 years ago, uranium concentrations were below the MCL of US Environmental Protection Agency for uranium in drinking water (0.03 mg/L). Higher concentrations, up to 1.23 mg/L of U, were found only at active dewatered mines. Activity concentration of 226Ra varied from 0.03 up to 1.85 Bq/L except for two sites with increased background values due to rock formation (granites). Radium has a typically increasing trend after mine abandonment with a large variability. Concerning metals in mine water, Al, Co and Ni exceeded legislative limits on two sites with low pH waters. The mine water quality changes with a focus on uranium mobility were described from recently dewatered mines to shafts with water level maintained in order to prevent outflows to surface water and finally to stagnating shafts and discharges of mine water from old adits. The results were in good agreement with published experience on mine water stratification, its disturbance by pumping or natural water decant and the "first flush" phenomenon after mine flooding.

Arsenic speciation and mobility in surface water at Lucky Shot Gold Mine, Alaska

Historical mining in Alaska has created a legacy of approximately 6,830 abandoned mine sites which include adits, tailing piles and contaminated land that continue to impact surface and groundwater quality through run-off and leaching of potentially toxic metals, especially arsenic (As). One such site is the Lucky Shot Gold Mine in Hatcher Pass, south-central Alaska, which operated from 1920 until 1942, mining gold-bearing quartz veins hosted in a Cretaceous tonalite intrusion. Arsenopyrite (FeAsS) and pyrite (FeS(2)) present in the quartz veins contribute to elevated As levels in water draining, abandoned mine adits. As future underground mining at Lucky Shot may further adversely impact water quality, baseline geochemical studies were undertaken to assess As mobility in the vicinity of the mine adits. Water samples were collected from streams, adits and boreholes around the mine and analysed for major and minor elements using inductively coupled plasma-mass spectrometry (ICP-MS) and for anions by ion chromatography (IC). Arsenic species separation was performed in the field to determine the ratio of inorganic As(III)/As(V) using anion-exchange chromatography, following established methods. It was determined that water draining the adits had elevated levels of As roughly seventy times the United States Environmental Protection Agency Drinking Water Standard of 10 μg L(-1), although this was rapidly diluted downstream in Craigie Creek to <2 μg L(-1). Adit and surface water pH was circum-neutral and displayed no characteristics of acid mine drainage. Despite being well oxygenated, As(III) is the dominant As species in adit water, accounting for close to 100 % of total As. The proportion of As(V) increases downstream of the adits, as some As(III) is oxidized, but the speciation enhances arsenic mobility at the site. The δ(18)O measurements indicate that the water in the system has a short residence time as it is very similar to meteoric water, supporting the observation that the predominance of As(III) in adit water results from the lack of thermodynamical equilibrium being attained and preferential absorbance of As(V).

Assessment of environmental hazards at abandoned mining sites: A case study in Sardinia, Italy

In the last two centuries, several Pb–Zn mines were active in the Rio Mannu basin near Narcao (SW Sardinia, Italy), but are now abandoned. These abandoned mines pose a serious risk to the population and required an assessment of the hazard sources and the contaminant pathways in the area. The characterization plan of the Rio Mannu basin was carried out according to Italian protocols. Specifically, samples of soil, stream sediment, fine-grained ore-processing waste (from washery and flotation processes), surface water and groundwater have been analyzed in order to assess the levels of contamination in each mine area and the risks in the plains surrounding the site. Several potential chemical contaminants were considered both in solid materials and water samples. The Rosas mine was recognized as the most contaminated area in the basin, due to the presence of a large tailing pond, some fine-grained waste piles and two mine adits with concentrations of the toxic elements As, Cd, Cu, Pb, Sb and Zn exceeding Italian regulatory standards. The dispersion of contaminants occurs downstream from the small stream draining the area. In case of heavy rain the runoff into the streamlet transports the contaminated material far into the plain. The results of this study show that the characterization plan is a relatively cheap tool for establishing mitigation actions, prior to the realization of a complete, and usually expensive, remediation project at abandoned mine sites. Urgent recommended actions in the Rio Mannu basin include the treatment of the adit water prior to its discharge into the Rio Barisonis; the construction of drainage barriers on waste piles to reduce runoff and solid transport into the Rio Barisonis; the consolidation of the earthen dam containing the tailing pond of Rosas to avoid the deepening of erosion furrows that may threaten its stability.

Mineralogical and chemical evolution of ochreous precipitates from the Libiola Fe–Cu-sulfide mine (Eastern Liguria, Italy)

Abstract The mineralogical and chemical evolution of ochreous precipitates forming from acid mine drainage (AMD) from the abandoned Libiola Fe–Cu-sulfide mine (Eastern Liguria, Italy) was followed through a multianalytical approach (XRD, TEM, XRF, ICP) applied to surface precipitates and associated waters collected from several mine adits. The mineralogy of the precipitates changed significantly as a consequence of the variations of the chemical parameters of the circulating solutions (mainly pH, Eh, and sulfate concentrations) which, in turn, were mainly controlled by mixing with unpolluted stream and rill waters of the mining area. A progressive transition from jarosite-, to schwertmannite-, to goethite-, to ferrihydrite-, to amorphous-dominated precipitates was observed, mainly as a consequence of an increase in the pH of the associated solutions. This mineralogical evolution agrees well with the aqueous speciation and Eh–pH stability calculations performed on the waters associated with the different precipitate types. Furthermore, TEM analysis indicated that metastable pristine phases (schwertmannite) tend to transform progressively to well-crystallized more stable species, here represented by goethite. The comparison of the water chemistry and the crystal chemistry of the different precipitates showed a significant decrease in the Zn, Cu, Ni, Co contents in waters where the coexisting precipitates were almost exclusively composed of goethite. The distribution of V, Sr, As concentrations within the different precipitates showed that the most efficient scavenging phase for these elements was jarosite, whereas ferrihydrite efficiently took up Pb ions, and schwermannite acted as a natural sink for Cr. The comparative analysis of the precipitates and waters of the Libiola mining area indicated that the authigenic Fe-oxyhydroxides play an important role in controlling the composition of the highly polluted AMD waters, but this role as “cleaning agents” was mostly ephemeral. Minor pH–Eh oscillations facilitated quick mineralogical transformations, via dissolution–reprecipitation or solid state transformation, which, in turn, controlled the trace elements that were mobilized or permanently stored within the solid phases.

The behavior of arsenic and antimony at Pezinok mining site, southwestern part of the Slovak Republic

Arsenic and antimony contamination is found at the Pezinok mining site in the southwest of the Slovak Republic. Investigation of this site included sampling and analysis of water, mineralogical analyses, sequential extraction, in addition to flow and geochemical modeling. The highest dissolved arsenic concentrations correspond to mine tailings (up to 90,000 μg/L) and the arsenic is present predominately as As(V). The primary source of the arsenic is the dissolution of arsenopyrite. Concentration of antimony reaches 7,500 μg/L and its primary source is the dissolution of stibnite. Pore water in mine tailings is well-buffered by the dissolution of carbonates (pH values between 6.6 and 7.0) and arsenopyrite grains are surrounded by reaction rims composed of ferric iron minerals. Based on sequential extraction results, most solid phase arsenic is in the reducible fraction (i.e. ferric oxyhydroxides), sulfidic fraction, and residual fraction. Distribution of antimony in the solid phase is similar, but contents are lower. The principal attenuation mechanism for As(V) is adsorption to ferric oxide and hydroxides, but the adsorption seems to be limited by the competition with Sb(V) produced by the oxidation of stibnite for adsorption sites. Water in mine tailings is at equilibrium with gypsum and calcite, but far from equilibrium with any arsenic and antimony minerals. The concentrations of arsenic and antimony in the surrounding aquifer are much lower, with maximum values of 215 and 426 μg/L, respectively. Arsenic and antimony are transported by ground water flow towards the Blatina Creek, but their loading from ground water to the creek is much lower compared with the input from the mine adits. In the Blatina Creek, arsenic and antimony are attenuated by dilution and by adsorption on ferric iron minerals in stream sediments with resulting respective concentrations of 93 and 45 μg/L at the site boundary south of mine tailing ponds.

Increased As load to the Uchen stream due to mine drainage and soils in the abandoned Kangwon mining district of Korea

To determine the appropriate allocation of resources for the future restoration of the abandoned mining district of Kangwon in Korea, identification of the main pollutants and the main sources discharging these pollutants is crucial. Therefore, a 2-year study was undertaken to quantify the amount of pollutants in the Uchen stream (a potential sink for contamination), which runs through the district, and to determine the potential sources of these pollutants, including mine drainage and soil. Arsenic (As) was the main pollutant in mine drainage and soils showing concentrations above the Korean regulated standard levels of 50 μg L−1 and 50 mg kg−1 for water and soil, respectively. In addition, the pollution index (PI) showed that mine drainages were polluted by As to a moderate (2 ≤ PI < 3) or strong (4 ≤ PI < 5) degree. Consequently, As load in mine drainage and soil contributed to increased amounts of As in the stream. The As loads in mine drainages (11 and 587 g month−1 for mine adit 1 and 2, respectively) accounted for only 9% of the total As load to the stream (6,378 g month−1); and the influence of mine drainages on As contents in the stream was more reliant on the total volume of mine drainage generated rather than the As concentration in the mine drainage. Approximately 91% of the As in the stream was derived from the soils within the study area.

Uranium-Series Constraints on Radionuclide Transport and Groundwater Flow at the Nopal I Uranium Deposit, Sierra Peña Blanca, Mexico

Uranium-series data for groundwater samples from the Nopal I uranium ore deposit were obtained to place constraints on radionuclide transport and hydrologic processes for a nuclear waste repository located in fractured, unsaturated volcanic tuff. Decreasing uranium concentrations for wells drilled in 2003 are consistent with a simple physical mixing model that indicates that groundwater velocities are low ( approximately 10 m/y). Uranium isotopic constraints, well productivities, and radon systematics also suggest limited groundwater mixing and slow flow in the saturated zone. Uranium isotopic systematics for seepage water collected in the mine adit show a spatial dependence which is consistent with longer water-rock interaction times and higher uranium dissolution inputs at the front adit where the deposit is located. Uranium-series disequilibria measurements for mostly unsaturated zone samples indicate that (230)Th/(238)U activity ratios range from 0.005 to 0.48 and (226)Ra/(238)U activity ratios range from 0.006 to 113. (239)Pu/(238)U mass ratios for the saturated zone are <2 x 10(-14), and Pu mobility in the saturated zone is >1000 times lower than the U mobility. Saturated zone mobility decreases in the order (238)U approximately (226)Ra > (230)Th approximately (239)Pu. Radium and thorium appear to have higher mobility in the unsaturated zone based on U-series data from fractures and seepage water near the deposit.

Metal contamination and post-remediation recovery in the Boulder River watershed, Jefferson County, Montana

ABSTRACT The legacy of acid mine drainage and toxic trace metals left in streams by historical mining is being addressed by many important yet costly remediation efforts. Monitoring of environmental conditions frequently is not performed but is essential to evaluate remediation effectiveness, determine whether clean-up goals have been met, and assess which remediation strategies are most effective. Extensive pre- and post-remediation data for water and sediment quality for the Boulder River watershed in southwestern Montana provide an unusual opportunity to demonstrate the importance of monitoring. The most extensive restoration in the watershed occurred at the Comet mine on High Ore Creek and resulted in the most dramatic improvement in aquatic habitat. Removal of contaminated sediment and tailings, and stream-channel reconstruction reduced Cd and Zn concentrations in water such that fish are now present, and reduced metal concentrations in streambed sediment by a factor of c . 10, the largest improvement in the district. Waste removals at the Buckeye/Enterprise and Bullion mine sites produced limited or no improvement in water and sediment quality, and acidic drainage from mine adits continues to degrade stream aquatic habitat. Recontouring of hillslopes that had funnelled runoff into the workings of the Crystal mine substantially reduced metal concentrations in Uncle Sam Gulch, but did not eliminate all of the acidic adit drainage. Lead isotopic evidence suggests that the Crystal mine rather than the Comet mine is now the largest source of metals in streambed sediment of the Boulder River. The completed removal actions prevent additional contaminants from entering the stream, but it may take many years for erosional processes to diminish the effects of contaminated sediment already in streams. Although significant strides have been made, additional efforts to seal draining adits or treat the adit effluent at the Bullion and Crystal mines would need to be completed to achieve the desired restoration. SUPPLEMENTARY MATERIAL Analytical data for all post-remediation samples is available at: http://www.geolsoc.org.uk/SUP18344.

Simulating metals and mine discharges in river basins using a new integrated catchment model for metals: pollution impacts and restoration strategies in the Aries-Mures river system in Transylvania, Romania

The INtegrated CAtchment (INCA) model has been developed to simulate the impact of mine discharges on river systems. The model accounts for the key kinetic chemical processes operating as well as the dilution, mixing and redistribution of pollutants in rivers downstream of mine discharges or acid rock drainage sites. The model is dynamic and simulates the day-to-day behaviour of hydrology and eight metals (cadmium, mercury, copper, zinc, lead, arsenic, manganese and chromium) as well as cyanide and ammonia. The model is semi-distributed and can simulate catchments, sub-catchment and in-stream river behaviour. The model has been applied to the Roşia Montană Mine in Transylvania, Romania, and used to assess the impacts of old mine adits on the local catchments as well as on the downstream Aries and Mures river system. The question of mine restoration is investigated and a set of clean-up scenarios investigated. It is shown that the planned restoration will generate a much improved water quality from the mine and also alleviate the metal pollution of the river system.

Site-specific P absorbency of ochre from acid mine-drainage near an abandoned Cu-S mine in the Avoca—Avonmore catchment, Ireland

AbstractAcid mine-drainage from an abandoned Cu-S mine adit, located in the Avoca–Avonmore catchment in the southeast of Ireland, results in low-value ochre deposition. Ochre found on-site had similar physical (particle size 97.7% &lt;2 mm and dry bulk density 0.8 g cm3), but dissimilar maximum P-retention characteristics (16–21 g P kg–1) to coal-mining ochre found in the UK. Stereomicroscopy identified oolites and diatoms in the ochre that were indicative of acidic environments. X-ray diffraction showed Fe mineralogy consisting of goethite, jarosite and minor amounts of ferrihydrite. Investigations by inductively coupled plasma-mass spectrometry and bulk energy-dispersive spectroscopy showed potentially toxic concentrations of Fe, Zn, Pb, As and Cu. Rapid mobilization of metals occurred during P-adsorption tests, which makes Avoca ochre unsuitable for use in a surface-water environmental technology.

Mineralogy and geochemistry of trace metals and REE in volcanic massive sulfide host rocks, stream sediments, stream waters and acid mine drainage from the Lousal mine area (Iberian Pyrite Belt, Portugal)

Acid mine drainage represents a major source of water pollution in the Lousal area. The concentrations of trace metals and the rare earth elements (REE) in the host rocks, stream sediment, surface waters and acid mine drainage (AMD) associated with abandoned mine adits and tailings impoundments were determined, in order to fingerprint their sources and to understand their mobility and water–rock interaction. The results show that the Fe–SO4-rich acid waters vary substantially in composition both spatially and seasonally. These waters include very low pH (mostly in the range 1.9–3.0), extreme SO4 concentrations (4635–20,070 mg L−1 SO42-), high metal contents (Fe, Al, Cu, Zn and Mn) and very high REE contents. The trace metal concentrations decrease downstream from the discharge points either due to precipitation of neoformed phases or to dilution. The North-American shale composite (NASC)-normalized patterns corresponding to sediment from one stream (Corona stream) show a flat tendency or are slightly enriched in light-REE (LREE). The NASC-normalized patterns corresponding to acidic mine waters show enrichment in the middle REE (MREE) with respect to the LREE and heavy REE (HREE). Moreover, the REE concentrations in acidic mine waters are 2 or 3 orders of magnitude higher than those of the surface waters. Changes of REE concentrations and variation of Eu anomaly show two spatially distinct patterns: (a) pond and spring waters with higher REE concentrations (ranging from 375 to 2870 μg L−1), that records conspicuous negative Eu anomaly, and (b) seeps from tailings impoundments corresponding to lower REE concentrations than the first pattern (ranging from 350 to 1139 μg L−1) with typically negative Eu anomaly. The stream water samples collected from the impacted stream during the spring show a low pH (2.8–3.1) and contain high concentrations of Fe and trace elements (up to 61 mg L−1). Also, temporal variations of the REE concentrations were observed in the Corona waters. The results obtained show that the REE concentrations increase during the winter–spring transition. Stream waters draining the Lousal mine area show high REE concentrations, reaching a maximum value of about 2846 μg L−1 (spring). The MREE concentrations are usually enriched with respect to both the LREE and HREE. A decrease in REE concentrations and a pH increase from 3 to 6 was observed downstream of the confluence of a tributary stream. The geochemistry of the waters strongly influenced the mineralogy and geochemistry of efflorescent sulfates precipitated on the banks of the streams polluted by AMD. The mineralogy is dominated by hexahydrite, rozenite, szomolnokite, alunite, gypsum, halotrychite, coquimbite, copiapite and schwertmannite. The REE concentrations determined in the efflorescent sulfates suggest a selective partitioning of the HREE onto Mg–Al-oxyhydroxides.

Hydrochemical, and Pb- and Sr- isotopic constraints on the precipitation and dilution of metals in acidified mine water: an example from the abandoned Dongjin Au-Ag-Cu mine, Korea

The geochemical properties (acidity, elemental composition, and isotopic composition of Sr and Pb) of surface water in the watershed of the abandoned Dongjin Au-Ag-Cu mine, central Korea, vary as the water drifts downstream and reacts with refuse ore piles. These properties also change due to adsorption and co-precipitation of metals on Fe-Al precipitates, and dilution by unpolluted waters. The patterns of variation of dissolved ions were divided into two groups (1 and 2). Group-1 ion (Al, Cu, Cd, and Pb) levels are increased only in acidified water after reaction with refuse ore piles, and their concentrations are regulated largely by precipitates of amorphous Fe-Al hydroxides, which strongly adsorb or precipitate these metals in mildly acidic to neutral conditions. The selective adsorption of Pb on Fe-Al precipitates is supported by Pb isotope data, suggesting that Pb from ore is dominant only in acidic water (pH 6.0) even with high contents of other ions from dissolved sulfide minerals because of strong adsorption of Pb from ore. Group-2 ions are composed of the major cations (alkali and alkaline-earth), anions, and trace elements including Zn and Mn. Their concentrations and 87Sr/86Sr ratios tend to decrease with distance from the mine adit, indicating that group-2 ions are less dependent on pH and are strongly controlled by mixing with unpolluted, dilute water from the surrounding areas. A combination of Pb and Sr isotopes is useful for tracing the geochemical evolution of surface water in acid mine drainage.

Detailed Radiometric Surveying at Radium Hill, South Australia

In June 2007 a ground radiometric survey utilising quad bikes, was conducted over the Radium Hill townsite, former minesite area and processing plant. An eight litre crystal pack was used along with an Exploranium GR-320 gamma ray spectrometer set to continuous (streaming) mode. A total of 148.8 line kilometres of radiometric data was collected over NS lines spaced at 100m intervals. Average ground speeds of ten kilometres per hour combined with the large crystal pack enabled good quality, highly detailed data to be collected on the ground over rough terrains. Data was continuously sampled at one second intervals and the entire survey was conducted in 10 days including mobilisation and demobilisation. The terrain was not suitable for large vehicles due to the danger of below surface mine adits, hence, the only alternative to surveying on quad bikes would be to survey on foot. It is estimated both that to get the same quality of data over this size survey area would require two operators 60 days, and also the use of such a large crystal pack would result in detailed data comparable with that derived from airborne surveys.

Radionuclides and metals in freshwater mussels of the upper South Alligator River, Australia

During an inspection of the old Rockhole Mine area in Kakadu National Park in 1999, it was found that a small amount of tailings from the former South Alligator uranium (U) mill had been uncovered by wet season rain and road works. Samples of sediment, water and freshwater mussels, Velesunio angasi, were collected from the South Alligator River, near and at the confluence of Rockhole Mine Creek, and adjacent to the exposed tailings. The 228Ra/ 226Ra activity ratios in sediments and mussel tissue indicate a small influence from the tailings and from Rockhole Mine adit water on 226Ra concentrations. The uptake of 226Ra in mussels does not correlate with other alkaline-earth metals. Mussel U concentrations are higher immediately downstream of Rockhole Mine Creek, but there is no noticeable increase in the immediate vicinity of the tailings area. A hypothetical ingestion of 2 kg of mussels from the sites was used to estimate the committed effective dose for a 10-year-old child resulting in a figure of 0.23 mSv per annum, of this total dose, 69% is attributed to 210Po. Only 0.03 mSv per annum can be directly linked to impacts of the tailings.

The status of the passive treatment systems for acid mine drainage in South Korea

This study was performed to investigate the operating status, evaluate the problems, and discuss possible improvement methods of passive treatment systems for acid mine drainage (AMD) in South Korea. Thirty-five passive treatment systems in 29 mines have been constructed from 1996 to 2002 using successive alkalinity producing systems (SAPS) as the main treatment process. We investigated 29 systems (two for metal mines), 19 of which revealed various problems. Overflows of drainage from SAPS, wetland, or oxidation ponds were caused by the flow rate exceeding the capacities of the facilities or by the reduced permeability of the organic substance layer. Leakages occurred at various parts of the systems. In some cases, clogged and broken pipes at the mouths of the mine adits made the whole system unusable. Some systems showed very low efficiencies without apparent leakage or overflow. Even though the systems showed fairly good efficiencies in metal removal ratios (mainly iron) and pH control; sulfate removal rates were very poor except in three systems, which may indicate very poor sulfate reductions with sulfate reducing bacteria (SRB) as a means.

Microbial Community Biofabrics in a Geothermal Mine Adit

Speleothems such as stalactites and stalagmites are usually considered to be mineralogical in composition and origin; however, microorganisms have been implicated in the development of some speleothems. We have identified and characterized the biological and mineralogical composition of mat-like biofabrics in two novel kinds of speleothems from a 50 degrees C geothermal mine adit near Glenwood Springs, CO. One type of structure consists of 2- to 3-cm-long, 3- to 4-mm-wide, leather-like, hollow, soda straw stalactites. Light and electron microscopy indicated that the stalactites are composed of a mineralized biofabric with several cell morphotypes in a laminated form, with gypsum and sulfur as the dominant mineral components. A small-subunit rRNA gene phylogenetic community analysis along the stalactite length yielded a diverse gradient of organisms, with a relatively simple suite of main constituents: Thermus spp., crenarchaeotes, Chloroflexi, and Gammaproteobacteria. PCR analysis also detected putative crenarchaeal ammonia monooxygenase subunit A (amoA) genes in this community, the majority related to sequences from other geothermal systems. The second type of speleothem, dumpling-like rafts floating on a 50 degrees C pool on the floor of the adit, showed a mat-like fabric of evidently living organisms on the outside of the dumpling, with a multimineral, amorphous, gypsum-based internal composition. These two novel types of biofabrics are examples of the complex roles that microbes can play in mineralization, weathering, and deposition processes in karst environments.

Interaction of acid mine drainage with waters and sediments at the Corona stream, Lousal mine (Iberian Pyrite Belt, Southern Portugal)

This study investigates the geochemical characteristics of the acid mine drainage discharged from the abandoned mine adits and tailing piles in the vicinity of the Lousal mine and evaluates the extent of pollution on water and on the stream sediments of the Corona stream. Atmospheric precipitation interacting with sulphide minerals in exposed tailings produces runoff water with pH values as low as 1.9–2.9 and high concentrations of \( {\text{SO}}^{{{\text{2}} - }}_{{\text{4}}}\)(9,249–20,700 mg l−1), Fe (959–4,830 mg l−1) and Al (136–624 mg l−1). The acidic effluents and mixed stream water carry elevated Cu, Pb, Zn, Cd and As concentrations that exceed the water quality standards. However, the severity of contamination generally decreases 4 km downstream of the source due to mixing with fresh waters, which causes the dilution of dissolved toxic metals and neutralization of acidity. Some natural attenuation of the contaminants also occurs due to the general reduced solubility of most trace metals, which may be removed from solution, by either co-precipitation or adsorption to the iron and aluminium precipitates.

Biological manganese removal from acid mine drainage in constructed wetlands and prototype bioreactors

Mine drainage waters vary considerably in the range and concentration of heavy metals they contain. Besides iron, manganese is frequently present at elevated concentrations in waters draining both coal and metal mines. Passive treatment systems (aerobic wetlands and compost bioreactors) are designed to remove iron by biologically induced oxidation/precipitation. Manganese, however, is problematic as it does not readily form sulfidic minerals and requires elevated pH (>8) for abiotic oxidation of Mn (II) to insoluble Mn (IV). As a result, manganese removal in passive remediation systems is often less effective than removal of iron. This was found to be the case at the pilot passive treatment plant (PPTP) constructed to treat water draining the former Wheal Jane tin mine in Cornwall, UK, where effective removal of manganese occurred only in one of the three rock filter components of the composite systems over a 1-year period of monitoring. Water in the two rock filter systems where manganese removal was relatively poor was generally <pH 5, whereas it was significantly higher (∼pH 7) in the third (effective) system. These differences in water chemistry and manganese removal were due to variable performances in the compost bioreactors that feed the rock filter units in the composite passive systems at Wheal Jane. An alternative approach for removing soluble manganese from mine waters, using fixed bed bioreactors, was developed. Ferromanganese nodules (about 2 cm diameter), collected from an abandoned mine adit in north Wales, were used to inoculate the bioreactors (working volume ca. 700 ml). Following colonization by manganese-oxidizing microbes, the aerated bioreactor catalysed the removal of soluble manganese, via oxidation of Mn (II) and precipitation of the resultant Mn (IV) in the bioreactor, in synthetic media and mine water from the Wheal Jane PPTP. Such an approach has potential application for removing soluble Mn from mine streams and other Mn-contaminated water courses.

Characterizing Aquatic Health Using Salmonid Mortality, Physiology, and Biomass Estimates in Streams with Elevated Concentrations of Arsenic, Cadmium, Copper, Lead, and Zinc in the Boulder River Watershed, Montana

Abandoned tailings and mine adits are located throughout the Boulder River watershed in Montana. In this watershed, all species of fish are absent from some tributary reaches near mine sources; however, populations of brook trout Salvelinus fontitalis, rainbow trout Oncorhynchus mykiss, and cut-throat trout O. clarki are found further downstream. Multiple methods must be used to investigate the effects of metals released by past mining activity because the effects on aquatic life may range in severity, depending on the proximity of mine sources. Therefore, we used three types of effects—those on fish population levels (as measured by survival), those on biomass and density, and those at the level of the individual (as measured by increases in metallothionein, products of lipid peroxidation, and increases in concentrations of tissue metals)—to assess the aquatic health of the Boulder River watershed. Elevated concentrations of Cd, Cu, and Zn in the water column were associated with increased mortality of trout at sites located near mine waste sources. The hypertrophy (swelling), degeneration (dying), and necrosis of epithelial cells observed in the gills support our conclusion that the cause of death was related to metals in the water column. At a site further downstream (lower Cataract Creek), we observed impaired health of resident trout, as well as effects on biomass and density (measured as decreases in the kilograms of trout per hectare and the number per 300 m) and effects at the individual level, including increases in metallothionein, products of lipid peroxidation, and tissue concentrations of metals.