Mine-impacted Water Research Articles

Highly Zn, Mn-rich calcite in calcareous tufa from the Qixiashan Pb-Zn Mine, Nanjing: a possible candidate for Zn-Mn removal from mining impacted waters

The exploitation of metallic mines may cause serious environmental problems. The removal of the heavy metals from the contaminated mining environments has become an urgent issue. In this paper, the occurrence and distribution of heavy metals in the calcareous tufa collected from the mining laneway of the Qixiashan Pb-Zn Mine in Nanjing were investigated by using multiple mineralogical techniques. Examination by X-ray diffraction spectrum (XRD) shows that calcite is the major component of the calcareous tufa. Several heavy metals such as Mn, Zn, Mg, Fe and Pb are detected in calcite by means of electron microprobe analysis. Although the heavy metal contents in the hostrock and the formation water are significantly low, the contents of Mn, Zn, Mg, Fe and Pb in the tufa calcite are as high as 23.65 wt%, 9.6 wt%, 0.76 wt%, 4.44 wt% and 0.66 wt%, respectively. The back-scattered electron image shows complex compositional zoning texture in the tufa, which is linked directly to variations in heavy metals, particularly in Mn and Zn. In addition, we also observed floccule and helical precipitations, which may be derived from the metabolism of the microbe. It is deduced that the occurrence and high concentration of heavy metals in tufa may be controlled by the activities of microbes. The results presented in this work suggest that calcite will be an important candidate for the remediation of the heavy metal contamination in mining areas.

THE BASIS FOR ECOTOXICOLOGICAL CONCERN IN AQUATIC ECOSYSTEMS CONTAMINATED BY HISTORICAL MERCURY MINING

The Coast Range of California is one of five global regions that dominated historical production of mercury (Hg) until declining demand led to the economic collapse of the Hg-mining industry in the United States. Calcines, waste rock, and contaminated alluvium from inactive mine sites can release Hg (including methylmercury, MeHg) to the environment for decades to centuries after mining has ceased. Soils, water, and sediment near mines often contain high concentrations of total Hg (TotHg), and an understanding of the biogeochemical transformations, transport, and bioaccumulation of this toxic metal is needed to assess effects of these contaminated environments on humans and wildlife. We briefly review the environmental behavior and effects of Hg, providing a prelude to the subsequent papers in this Special Issue. Clear Lake is a northern California lake contaminated by wastes from the abandoned Sulphur Bank Mercury Mine, a U.S. Environmental Protection Agency Superfund Site. The primary toxicological problem with Hg in aquatic ecosystems is biotic exposure to MeHg, a highly toxic compound that readily bioaccumulates. Processes that affect the abundance of MeHg (including methylation and demethylation) strongly affect its concentration in all trophic levels of aquatic food webs. MeHg can biomagnify to high concentrations in aquatic food webs, and consumption of fish is the primary pathway for human exposure. Fish consumption advisories have been issued for many North American waters, including Clear Lake and other mine-impacted waters in California, as a means of decreasing MeHg exposure. Concerns about MeHg exposure in humans focus largely on developmental neurotoxicity to the fetus and children. Aquatic food webs are also an important pathway for MeHg exposure of wildlife, which can accumulate high, sometimes harmful, concentrations. In birds, wild mammals, and humans, MeHg readily passes to the developing egg, embryo, or fetus, life stages that are much more sensitive than the adult. The papers in this issue examine the origin, transport, transformations, bioaccumulation, and trophic transfer of Hg in Clear Lake, assess its potential effects on biota and humans, and provide information relevant to remediation of mine-impacted aquatic ecosystems.

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Crab-shell chitin has been shown to effectively reduce SO4 2- , enhance alkalinity, and remove metals from mine impacted water (MIW) at the bench scale and in field trials. To date, this research has been conducted using inexpensive, raw crab shell (ChitoRem™ SC-20), which in addition to chitin, contains CaCO3 and residual protein. All three of these components contribute to MIW treatment simultaneously, and are therefore difficult to uncouple. In this experiment, three different purities of crab shell (SC-20, SC-40, and SC-80) and limestone were tested for their ability to remediate natural MIW from an abandoned coal-mine in central Pennsylvania. The goals of this project were: 1) to compare the efficiency of metals and sulfate removal between different purities of chitin; and, 2) to begin to uncouple the contributions of chitin, protein, and calcium carbonate when raw crab shell chitin is used for the treatment of acid mine drainage. Sacrificial batch microcosms containing natural MIW, stream sediment, and either SC-20, SC-40, SC-80, or limestone were established in duplicate and incubated at room temperature for up to 117 days. The most complete and rapid metals removal was observed with SC-20, followed by SC-40, SC-80, and limestone. SC-20 removed more than 99% of Al, Fe, and Zn and more than 98% of dissolved Mn. SC-40 exhibited similar metals removal, but at slower rates. SC-80 and limestone were not effective at removing Mn. Alkalinity production followed similar trends, with SC-20 surpassing the other substrates with a total alkalinity of 1175 mg/L as CaCO3 after 117 days. Elevated NH4 production was observed at early times only with SC-20, indicating that it is residual protein, not chitin, releasing this nutrient. It is likely that the rapid dissolution of CaCO3 from the crab shell, coupled with NH4 release and biological SO4 2- reduction all contributed to elevated alkalinity values and consequently superior metals removal with SC-20. Preliminary geochemical modeling suggests that the probable mechanisms for metals removal with SC-20 include precipitation of Al and Fe oxides/hydroxides and manganese carbonates, as well as physical adsorption onto components of the crab shell.

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The Copper Basin, located in southeast Tennessee, is the site of extensive copper mining and processing operations dating back to the mid-1800s. The London Mill area within the Copper Basin, which included a mine and a flotation plant to separate metal sulfides from waste rock, was abandoned in 1987. Under a voluntary agreement, Glenn Springs Holdings, Inc., a subsidiary of Occidental Petroleum Company, has developed and implemented a remedial plan for the London Mill area to address safety and human health hazards and conduct environmental restoration activities. The remedial approach for the London Mill area required a combination of reclamation activities including elimination of physical hazards, removal or isolation of waste materials, diversion of clean water, collection and treatment of mine-impacted water, and stabilization of surface conditions.

Impact of past mining activity on the quality of groundwater in SW Sardinia (Italy)

Hydrogeochemical surveys were carried out in SW Sardinia (Italy) to investigate the impact of past mining activities on the quality of groundwater. The chemistry of waters from flooded galleries, adits and dumps has been compared with that of springs and wells in the same area at sites relatively far from any mine legacy. A feature, common to all waters, is the circumneutral pH, since the carbonate formations in the area neutralise the acidity produced by the oxidation of Fe-bearing sulphide minerals in the mine impacted water. However, groundwater interacting with mine workings is degraded in quality; it shows high dissolved SO 4, Zn, Cd and Pb contents. In some cases groundwater exceeds the limit established by the guidelines of the World Health Organization for Pb content in drinking water, so that groundwater is mixed before entering the local aqueducts. Results from this study suggest that more attention needs to be paid to the impact on the streams from contaminated water flowing out from some mine areas because during the dry season these streams are only fed by mine groundwater. We recommend focusing efforts to reduce the chemical contamination prior to discharge.

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The Peerless Jenny King treatment system is a series of four sulfate reducing bioreactor cells installed to treat acid mine drainage in the Upper Tenmile Creek Superfund Site located in the Rimini Mining District, near Helena MT. The system consists of a wetland pretreatment followed by the four cells connected in a serpentine manner. The mining impacted water flows from the wetland through each cell before discharge. Sulfate reducing bioreactors mitigate acidity and metal contamination through the microbial production of sulfide. The produced biogenic sulfide precipitates metals, and the microbial process of reducing sulfate to sulfide produces alkalinity. The health of the entire microbial community present in such systems is important for remediation to be effective. Classes of microbes generally present in such systems include fermenters, methanogens and sulfate reducers. The health can be measured in terms of active microbial populations and positive interactions between populations for the support of sulfate reduction. The goal of this research is to measure the activity of each class utilizing analyses that quantify the groups by their function, as opposed to the traditional molecular techniques of identifying bacteria. Gas chromatography, HPLC- DAD, and ICP-AES are used to identify and quantify the end products of metabolism. The microbial activity can then be characterized and changes can be monitored over time. Results from 2005 sampling of Cell 3 within the system indicate that the activity of sulfate reducing bacteria is much higher than the numbers present would indicate. These results combined with those from 2006 sampling indicate that methanogenesis is a minor process within this cell. The calculation of the stoichiometry of carbon utilization by SRB is much higher than what would be predicted from known stoichiometric ratios of carbon used per sulfate reduced.

An Innovative Carbonate Coprecipitation Process for the Removal of Zinc and Manganese from Mining Impacted Waters

Although mine drainage is usually thought of as acidic, there are many cases where the water is of neutral pH, but still contains metal species that can be harmful to human or aquatic animal health...

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Limestone systems are generally used for acid neutralization of mining impacted waters. However they can also be designed to remove heavy metal constituents. The issues surrounding the design of a limestone system for metal removal are different from the issues involved in acid neutralization. Experiments were carried out to explore these issues by evaluating the interaction of CaCO3 with solutions containing a primary metal (Fe, Al), and a secondary metal (Zn, Ni). The fate of the secondary metals and their removal as a function of pH, alkalinity, and primary metal concentration are reported. Although these parameters by themselves are not necessarily good indicators of secondary metal removal, when coupled with the influent primary:secondary metal ratio, trends become apparent that can be used as design parameters. Zinc and Ni removals appear to be a function of Fe +3 concentrations and removals are shown to be as high as 97% and 87%, respectively, at near neutral pH values. The removal reaches a saturation point at an Fe:Zn ratio of 50:1, and for Ni the saturation ratio is 45:1 Zinc and Ni removals with Al gave ambiguous results.

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Pulsed limestone bed treatment is a new technology for the processing of acid mine drainage that utilizes limestone in fluidized bed reactors for an economical method of neutralizing acidity, adding alkalinity, and removing metal contaminants from mining impacted waters. The technology was developed by the U.S. Geological Survey, at the Leetown Science Center in Kearneysville, West Virginia. Previous demonstrations of this technology have taken place at coal mining sites in the Appalachian region. In this demonstration project, funded by the Mine Waste Technology Program of EPA, the Pulsed Limestone Bed (PLB) technology is being demonstrated at the Argo Tunnel Water Treatment Facility, which currently treats metal mining impacted waters flowing into Clear Creek. A 230 liter per minute pilot treatment system was installed in a moving van trailer and transported to the site in summer of 2004. Untreated water at the Argo site typically contains about 600 mg/L acidity (as CaCO3), due to the presence of hydrolysable metals including iron, aluminum, copper, zinc and manganese. Shakedown tests of the system were conducted by project cooperators from the Colorado School of Mines, and demonstrated an increase in pH from 3.0 to 7.0, nearly complete removal of iron and aluminum and an effluent alkalinity of about 100 mg/L as CaCO3. Post-treatment of the process effluent was required for removal of Mn and Zn, but test results indicated a decrease in reagent costs, as well as decreased sludge volume, due to the replacement of lime or sodium hydroxide by limestone as the neutralization agent. Complete process testing is scheduled for summer 2005.

Does batch operation enhance oxidation in subsurface constructed wetlands?

Two side-by-side experimental sub-surface flow systems allowed direct comparison of wetland performance under batch and continuous-flow operation. One system consisted of microcosm "columns" operated in 20-day batch mode while the second consisted of continuous-flow "cells" operated at a five-day residence time. Both systems treated identical synthetic domestic wastewater for two years and then treated identical synthetic mine-impacted water for one year. Each system had replicates planted with Typha latifolia, Scirpus acutus and unplanted controls. Temperature was cycled annually between 4 to 24 degrees C. Results indicated that plant species, season, and mode of operation interacted strongly in controlling dynamics of COD, nitrogen species, phosphate, sulfate, and redox potentials. In batch-loaded columns, between-species differences in oxidation and COD removal were large in winter, during plant dormancy, but absent in summer; COD removal, sulfate concentration, and redox potentials were closely correlated, suggesting that variation in root-zone oxygenation due to seasonal plant growth patterns and temperature-dependent plant and microbial respiration may explain observed differences. In the continuous-flow cells, species and seasonal differences were minimal or non-existent, indicating that under continuous-flow operation plants either did not influence root zone oxidation or that this influence had no effect on wetland performance for COD and nutrient removal or sulfate reduction.

Reaction rates of natural orpiment oxidation at 25 to 40°C and pH 6.8 to 8.2 and comparison with amorphous As 2S 3 oxidation

The oxidation rate of natural orpiment from Carlin-type deposits was measured at 25 to 40°C in a mixed flow reactor as a function of pH (6.8 to 8.2) and dissolved oxygen concentration (6.4 to 17.4 ppm) with a starting ionic strength of 0.01 M NaCl. All experiments ran for approximately 30 h, where steady-state conditions were reached after 20 h at a flow rate of 10 mL/min. The stoichiometric ratio of As/S was observed once steady state was reached. The rate law of orpiment oxidation is as follows: R=10 −11.77(±0.36)[ DO] 0.36(±0.09)[H +] −0.47(±0.05), where R signifies the rate of orpiment destruction (mol m −2 s −1), [DO] is the concentration of dissolved oxygen (M), and [H +] is the concentration of proton (M). The activation energy for the orpiment oxidation by dissolved oxygen at a temperature range of 25 to 40°C is 59.1 kJ/mol. Oxidation reactions of orpiment show incomplete oxidation of arsenic and sulfide in solution. At a pH range of 6.8 to 8.2, As(III) exists as H 3AsO 3 and As(V) is present as HAsO 4 2− and H 2AsO 4 −. Sulfite, sulfate, and thiosulfate are present as small fractions of total sulfur. The possible major sulfur species are intermediate oxidation state species. The oxidation rate of natural orpiment oxidation is slightly lower by a factor of 0.002 to 0.560 than that of As 2S 3(am) at the considered pH 7 to 10 and DO concentrations of 1 to 10 ppm. The dependence factors on pH for natural orpiment oxidation are lower by a factor of 0.37 compared with As 2S 3(am). However, the calculated activation energy is much larger for natural orpiment than As 2S 3(am) by a factor of 3.5. As(III) and As(V) are the major products for both As 2S 3(am) and natural orpiment oxidation along with intermediate sulfur species. The rate of orpiment oxidation increases with pH and results in an increase in the release of As. In mining-impacted environments with alkaline waters, as may be found in carbonate-hosted ore deposits, the natural attenuation of As oxyanions by sorption to oxide/hydroxide mineral surfaces is minimized because of a negative surface charge at a higher pH range. Thus, As concentrations may increase in mining-impacted waters at higher pH values (>8).

Assessing mine drainage pH from the color and spectral reflectance of chemical precipitates

The pH of mine impacted waters was estimated from the spectral reflectance of resident sediments composed mostly of chemical precipitates. Mine drainage sediments were collected from sites in the Anthracite Region of eastern Pennsylvania, representing acid to near neutral pH. Sediments occurring in acidic waters contained primarily schwertmannite and goethite while near neutral waters produced ferrihydrite. The minerals comprising the sediments occurring at each pH mode were spectrally separable. Spectral angle difference mapping was used to correlate sediment color with stream water pH ( r 2=0.76). Band-center and band-depth analysis of spectral absorption features were also used to discriminate ferrihydrite and goethite and/or schwertmannite by analyzing the 4T 1← 6A 1 crystal field transition (900–1000 nm). The presence of these minerals accurately predicted stream water pH ( r 2=0.87) and provided a qualitative estimate of dissolved SO 4 concentrations. Spectral analysis results were used to analyze airborne digital multispectral video (DMSV) imagery for several sites in the region. The high spatial resolution of the DMSV sensor allowed for precise mapping of the mine drainage sediments. The results from this study indicate that airborne and space-borne imaging spectrometers may be used to accurately classify streams impacted by acid vs. neutral-to-alkaline mine drainage after appropriate spectral libraries are developed.

Potential Remobilization of Toxic Anions during Reduction of Arsenated and Chromated Schwertmannite by the Dissimilatory Fe(III)-Reducing Bacterium Acidiphilium cryptum JF-5

Schwertmannite, an iron(III)-oxyhydroxysulfate formed in acidic mining-impacted stream or lake waters often contaminated with toxic elements like arsenate or chromate, is able to incorporate high amounts of these oxyanions. Detoxification of the water might be achieved if precipitated arsenated or chromated schwertmannite is fixed in the sediment. However, under reduced conditions, reductive dissolution of iron oxides mediated by the activity of Fe(III)-reducing bacteria might mobilize arsenate and chromate again. In this study, the reduction of synthesized arsenated or chromated schwertmannite by the acidophilic Fe(III)-reducer Acidiphilium cryptum JF-5, isolated from an acidic mining-impacted sediment, was investigated. In TSB medium at pH 2.7 with glucose as electron donor, A. cryptum JF-5 reduced about 10% of the total Fe(III) present in pure synthetic schwertmannite but only 5% of Fe(III) present in arsenated schwertmannite. In contrast to sulfate that was released during the reductive dissolution of pure schwertmannite, arsenate was not released during the reduction of arsenated schwertmannite probably due to the high surface complexation constant of arsenate and Fe(III). In medium containing chromated schwertmannite, no Fe(II) was formed, and no glucose was consumed indicating that chromate might have been toxic to cells of A. cryptum JF-5. Both As(V) or Cr(VI) could not be utilized as electron acceptor by A. cryptum JF-5. A comparison between autoclaved (121 °C for 20 min) and non-autoclaved schwertmannite samples demonstrated that nearly 100%of the bound sulfate was released during heating, and FTIR spectra indicated a transformation of schwertmannite to goethite. This structural change was not observed with autoclaved arsenated or chromated schwertmannite. These results suggest that the mobility of arsenate and chromate is not enhanced by the activity of acidophilic Fe(III)-reducing bacteria in mining-impacted sediments. In contrast, the presence of bound arsenate and chromate seemed to stabilize schwertmannite against reductive dissolution and its further transformation to goethite that is an ongoing process in those sediments.

Microbially Mediated Thallium Immobilization in Bench Scale Systems

Results from bench-scale tests for thallium remediation in mining-impacted water are presented and removal mechanisms are discussed. The source water consisted of surface runoff mixed with groundwater from an inactive gold mine in central Montana. Bench scale columns were operated under continuous flow for 225 days to test for microbially-mediated thallium immobilization. Various compositions of straw and steer manure in a gravel matrix provided a source of organic nutrients and sulfate-reducing bacteria sufficient to initiate and maintain microbial sulfate reduction up to 270 mmol/m3d. Hydraulic residence times of 2.7 days produced an aqueous thallium effluent concentration below the analytical detection limit of 2.5 μg/L at 20°C in all the tested columns. These effluent levels were achieved for influent dissolved thallium concentrations varying from 450 to 790 μg/L. An increase in pH between influent (pH 6.9) and effluents (pH 7.5) was observed. Hydraulic conductivity remained relatively constant during the course of the experiments and varied for the different test columns between 0.2 and 10 cm/s. The highest k-values were observed in the horizontal flow column. In addition to the column tests, sterile serum-vial experiments were performed to confirm that thallium sulfide (Tl2S) formation and precipitation was the most likely mechanism for thallium removal. Data from the bench-scale experiments were utilized for the design of an on-site pilot-scale passive treatment system.

Development of flow cytometry‐based algal bioassays for assessing toxicity of copper in natural waters

Copper toxicity to the freshwater algae Selenastrum capricornutum and Chlorella sp. and the marine algae Phaeodactylum tricornutum and Dunaliella tertiolecta was investigated using different parameters measured by flow cytometry: cell division rate inhibition, chlorophyll a fluorescence, cell size (i.e., light-scattering), and enzyme activity. These parameters were assessed regarding their usefulness as alternative endpoints for acute (1-24 h) and chronic (48-72 h) toxicity tests. At copper concentrations of 10 micrograms/L or less, significant inhibition (50%) of the cell division rate was observed after 48- and 72-h exposures for Chlorella sp., S. capricornutum, and P. tricornutum. Bioassays based on increases in algal cell size were also sensitive for Chlorella sp. and P. tricornutum. Copper caused both chlorophyll a fluorescence stimulation (48-h EC50 of 10 +/- 1 micrograms Cu/L for P. tricornutum) and inhibition (48-h EC50 of 14 +/- 6 micrograms Cu/L for S. capricornutum). For acute toxicity over short exposure periods, esterase activity in S. capricornutum using fluorescein diacetate offered a rapid alternative (3-h EC50 of 90 +/- 40 micrograms Cu/L) to growth inhibition tests for monitoring copper toxicity in mine-impacted waters. For all the effect parameters measured, D. tertiolecta was tolerant to copper at concentrations up to its solubility limit in seawater. These results demonstrate that flow cytometry is a useful technique for toxicity testing with microalgae and provide additional information regarding the general mode of action of copper (II) to algal species.

METHODS TO DIFFERENTIATE BETWEEN GROUNDWATER SOLUTE SOURCES

The Robinson district, Ely, Nevada is located in a complex hydrogeological system consisting of 12 distinct provinces each with distinctive background chemistry. To elucidate transport pathways, it was necessary to discriminate between background, marginally impacted, and historic source impacted waters. Standard approaches such as Piper diagrams failed to provide adequate discriminatory power. Therefore, a selected set of pit lakes, waste rock seeps, and surface water/groundwater samples were analyzed for a suite of major, minor and trace elements, rare earth elements (REEs), precious metals, and stable isotopes ({sup 16}O/{sup 18}O and D/H). The stable isotopes {sup 16}O/{sup 18}O and D/H provide coarse discrimination between the three classes of water. Background waters were found to contain barium above 10 {micro}g/L, and less in mine-impacted waters due to precipitation of insoluble barium sulfate. Scandium, rhenium, and rubidium in waste rock related seeps and pit lakes, in conjunction with barium allowed clear segregation between the three classes of water.