Coal Mine Drainage Research Articles

Iron Isotope Compositions of Natural River and Lake Samples in the Karst Area, Guizhou Province, Southwest China

Abstract:To better understand the Fe isotope characteristics of natural samples in the Karst area, the Fe isotope compositions of riverine suspended particulates, lake suspended particulates, lake sediments, porewaters, phytoplanktons, and aerosols in the watersheds of Lake Aha (a mineralized water system) and Lake Hongfeng (a mesotrophic water system), which are located in the Karst area, southwest China, were investigated. The studied samples displayed a variable range between δ56Fe=–2.03‰ and 0.36‰. Aerosols and phytoplanktons have similar or slightly heavier Fe isotope compositions relative to the average of igneous rocks. Fe isotope compositions of riverine Suspended Particulate Matter (SPM) were mainly affected by the types of tributaries. Suspended particulates collected from tributaries seriously contaminated with coal mine drainages displayed negative δ56Fe values (–0.89‰ to –0.31‰) during summer, and there were significant increases of δ56Fe values in winter, except AR2, which was polluted with both coal mine drainage and sewage effluent. Characteristics of lakes have important influences on Fe isotope compositions of suspended particulates, lake sediments, and porewaters. The epilimnetic particulate Fe of Lake Hongfeng had δ56Fe=–0.04‰ to 0.13‰, while lighter Fe isotope compositions were measured for particulate Fe from Lake Aha, ranging from –0.42‰ to –0.09‰. Sediments collected from Hou Wu (HW) station of Lake Hongfeng have an average δ56Fe value of 0.09‰ and their corresponding porewaters have lighter Fe isotope compositions, ranging from –0.57‰ to –0.31‰; no significant variations have been observed. For the Liang Jiang Kou (LJK) station of Lake Aha, the content of reactive Fe and the concentration of sulfate were all high. Due to the reactive Fe recycling, including dissimilatory Fe reduction, adsorption, and Fe–sulfide formation, porewaters sampled near the sediment surface have been found to have a δ56Fe value as low as –2.03‰ and an increase up to 0.12‰, with a burial depth of 10 cm. In contrast, an opposite variation trend was found for LJK sediments. Sediments sampled at 1‐cm depth had a value of δ56Fe=–0.59‰ and decrease as low as –1.75‰ with burial depth. This investigation demonstrated that significant Fe isotope fractionations occur in surface environments. Fe isotope compositions of particulate Fe were seriously affected by Fe sources, and Fe biogeochemical recycling has an important influence on Fe isotope fractionations in lake sediments, especially when there are significant amounts of reactive Fe and sulfate.

Remediation of coal-mine drainage by a sulfate-reducing bioreactor: A case study from the Illinois coal basin, USA

Abstract This study reports changes in coal-mine drainage constituent concentrations through an anaerobic SO4-reducing bioreactor monitored over a 3-a period. The purpose of the study was to identify and monitor over time the biogeochemical mechanisms that control the attenuation of toxic compounds in the mine drainage. This information is needed to investigate bioreactor performance and longevity. The water treated at the case example site, the Tab-Simco Mine, was highly acidic with an average pH of 2.9, a net acidity of 1674 mg/L CaCO3 equivalent-CCE, and high levels of dissolved SO 4 2 - , Al, Fe and Mn. The results of this study indicated that the treatment system increased the pH of the acid mine drainage (AMD) to 6.2 and decreased the median acidity to 22.7 mg/L CCE, SO 4 2 - from 2981 to 1750 mg/L, Fe from 450.6 to 1.76 mg/L, Al from 113 to 0.42 mg/L, and Mn from 36.4 to 23.3 mg/L. Geochemical modeling indicates that the bioreactor discharge is saturated with respect to the minerals alunite, gibbsite, siderite, rhodochrosite, jarosite, and Fe hydroxide precipitates. The observed trends also include seasonal variations in SO 4 2 - reduction and a general decline in the amount of alkalinity produced. The average δ34S value of the SO 4 2 - in the untreated AMD was +7.3‰. In the bioreactor, δ34S value of SO 4 2 - increased from an average of +6.9‰ to +9.2‰, suggesting the presence of bacterial SO4 reduction processes. Preliminary results of a bacterial community analysis show that DNA sequences corresponding to bacteria capable of SO4 reduction were present in the bioreactor outflow sample. However, these sequences were outnumbered by sequences similar to bacteria capable of reoxdizing reduced sulfur species. This study illustrates the dynamic nature of metal removal in SO4-reducing bioreactor-based treatment systems.

석탄광산배수슬러지를 이용한 액상상태의 비소제거 흡착특성 및 반응속도에 관한 연구

Abstract In this research, equilibrium of adsorption and kinetics of As(V) removal were investigated. The coal mine drainage sludge(CMDS) was used as adsorbent. To find out the physical and chemical properties of CMDS, XRD (X-ray diffraction), XRF (X-ray fluorescence spectrometer) analysis were carried out. The CMDS was consist of 70% of goethite and 30% of calcite. From the results, an adsorption mechanism of As(V) with CMDS was dominated by iron oxides. Langmuir adsorption isotherm model was fitted well more than Freundlich isotherm adsorption model. Adsorption capacities of CMDS 1 was not different with CMDS 2 on aspect of amounts of arsenic adsorbed. The maximum adsorption amount of two CMDS were respectively 40.816, 39.682 mg/g. However, the kinetic of two CMDS was different. The kinetic was followed pseudo second order model than pseudo first order model. Concentrations of arsenic in all segments of the polymer in CMDS 2 does not have a constant value, but the rate was greater than the value of CMDS 1. Therefore, CMDS 2, which is containing polymer, is more effective for adsorbent to remove As(V).

A process-orientated design and performance assessment methodology for passive mine water treatment systems

The aim of this paper is the development of a methodology for assessing the iron removal efficiency of passive mine water treatment settling lagoons and reed beds. Previous work in the design and sizing of coal mine drainage lagoons and wetlands has focussed on the use of standard hydraulic residence times or using the 10 g m −2 d −1 metric, these criteria have been applied without regard to the fundamental physical and chemical processes controlling iron removal in the system, namely the pH dependent rates of Fe(II) oxidation and physical settling of the particulate Fe(III). In this study field water quality data have been collected from lagoons and reed beds. These data are examined alongside data from the UK Coal Authority database and combined with simple mathematical formulations to provide a framework through which to understand passive treatment schemes from a process-orientated perspective. It is demonstrated that for the sites studied reed beds are more efficient for iron removal. This paper recommends that judgements of iron removal performance should be based on a derived treatment efficiency index ( ɛ) and that the modelling approach espoused in this paper should be used when designing passive mine water treatment schemes.

Evaluation of Field Applicability with Coal Mine Drainage Sludge (CMDS) as a Liner: Part I: Physico-Chemical Characteristics of CMDS and a Mixed Liner

CMDS (Coal Mine Drainage Sludge) is mainly generated from acid mine drainage during physicochemical treatment or electrical purification. CMDS is well worth considering on recycling possibilities in various areas. This research applies the liner and cover materials using waste disposal landfill generally to treat acid mine drainage sludge. In this Part I of the two parts paper, physico-chemical characteristics of CMDS, bentonite and cement to prepare the liner have been identified using XRD, XRF, FESEM. In addition, combining their physicochemical characteristics, the optimum mixing ratio has been determined to be 1: 0.5: 0.3 for CMDS: bentonite: cement by the batch tests. Initial permeability of CMDS was . Through the leaching test, it was confirmed that its mixture was environmentally safe. In the Part 2, a large-scale Lysimeter was used to simulate the effects of the layer on the freeze/thaw for evaluation on field applicability and stability.

Potential application of sludge produced from coal mine drainage treatment for removing Zn(II) in an aqueous phase

Various analyses of physico-chemical characteristics and batch tests were conducted with the sludge obtained from a full-scale electrolysis facility for treating coal mine drainage in order to find the applicability of sludge as a material for removing Zn(II) in an aqueous phase. The physico-chemical analysis results indicated that coal mine drainage sludge (CMDS) had a high specific surface area and also satisfied the standard of toxicity characteristic leaching procedure (TCLP) because the extracted concentrations of certain toxic elements such as Pb, Cu, As, Hg, Zn, and Ni were much less than their regulatory limits. The results of X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) showed that the CMDS mainly consists of goethite (70%) and calcite (30%) as a weight basis. However, the zeta potential analysis represented that the CMDS had a lower isoelectric point of pH (pH(IEP)) than that of goethite or calcite. This might have been caused by the complexation of negatively charged anions, especially sulfate, which usually exists with a high concentration in coal mine drainage. The results of Fourier transform infrared (FT-IR) spectrometry analysis revealed that Zn(II) was dominantly removed as a form of precipitation by calcite, such as smithsonite [ZnCO₃] or hydrozincite [Zn₅(CO₃)₂(OH)₆]. Recycling sludge, originally a waste material, for the removal process of Zn(II), as well as other heavy metals, could be beneficial due to its high and speedy removal capability and low economic costs.

Kinetic and thermodynamic studies of the adsorption of heavy metals on to a new adsorbent: coal mine drainage sludge

In this study, we investigated the application of sludge waste obtained from a coal mine drainage treatment facility that treats acid mine drainage (designated as AMD) from metal‐mine water. The coal mine drainage sludge (designated as CMDS), which contained 70% goethite and 30% calcite, was utilized as a sorption material for Cu(II) and Zn(II) removal from an aqueous solution of metallic mine drainage. The equilibriums and kinetics were investigated during a series of batch adsorption experiments. The Langmuir model was used to fit the equilibrium data, resulting in the best fits. The removal efficiencies were controlled by solution pH, temperature, initial concentration of heavy metal, sorbent amount and contact time. The pseudo‐second‐order kinetic model was used to fit the kinetic data, providing a good correlation with the experimental data. The results of a thermodynamic study showed that the activation energies (EA) were 3.75 and 1.75 kJ mol−1 for the adsorption of Cu(II) and Zn(II) on to CMDS at pH 5.5. These values of activation energy could correspond to physisorption. The positive values obtained for both the standard enthalpy change, Δ0, and the standard entropy change, ΔS0, suggest that the adsorption of Cu(II) and Zn(II) on to the CMDS was an endothermic reaction and that randomness increased at the solid–liquid interface during the adsorption of Cu(II) and Zn(II) on to the CMDS. The adsorption process also followed a pseudo‐second‐order kinetic model.

Plant-derived phenolic compounds impair the remediation of acid mine drainage using treatment wetlands

The use of wetlands to remediate acid mine drainage has expanded rapidly since the realisation that acid coal mine drainage running into natural sphagnum wetlands undergoes an increase in pH and a precipitation of metals. However, our study suggests that the inclusion of plants in the acid mine drainage treatment system may be questionable, due to inefficiencies caused by exudation of dissolved organic carbon (DOC), and in particular its phenolic constituents. They complex with iron, causing increased solubility, the exact opposite of what is required to facilitate amelioration. The addition of minewater to planted wetland mesocosms initially caused a decline in Fe concentrations, typically from over 1100 to a low of 75mgL−1. However, it increased higher than 300mgL−1 after 15 days. The rise in iron occurred concurrently with DOC and phenolic increases; 15–69 and 5–15mgL−1, respectively, for Eriophorum angustifolium. Removal of DOC by precipitation with calcium lowered the DOC abundance, but without a simultaneous decrease in iron concentration. The concentration of one fraction of the DOC, phenolic compounds, did not decline, and we propose that the Fe was complexed with that phenolic DOC pool. The proposal was confirmed by enzymic depletion of the phenolic compounds using phenol oxidase. Our findings suggest that phenolic complexation represents a potent constraint on wetland-based bioremediation of iron in acid mine drainage.

Performance of a passive treatment system for net-acidic coal mine drainage over five years of operation

A full-scale passive treatment system (PTS) was commissioned in 2003 to treat two net-acidic coal mine water discharges in the Durham coalfield, UK. The principal aim of the PTS was to decrease concentrations of iron (< 177 mg L − 1) and aluminium (< 85 mg L − 1) and to increase pH (> 3.2) and alkalinity (≥ 0 mg L − 1 CaCO 3 eq). Secondary objectives were to decrease zinc (< 2.8 mg L − 1), manganese (< 20.5 mg L − 1) and sulfate (< 2120 mg L − 1). Upon treatment, water qualities were improved by 84% in the case of Fe, 87% Al, 83% acidity, 51% Zn, 23% Mn and 29% SO 4 2 −. Alkalinity (74%) and pH (95% as H +) were increased. Area adjusted removal rates (Fe = 1.49 ± 0.66 g d − 1 m − 2; acidity = 6.7 ± 4.9 g d − 1 m − 2) were low compared to design criteria, mainly due to load limitation. Disregarding seasonality effects, acidity removal and effluent pH were stable over time. A substantial temporal decrease in calcium and alkalinity generation suggests that limestone is increasingly armoured. Once pH is no longer buffered by the carbonate system, metals could be remobilized, putting treatment efficiency at risk.

Operational state monitoring and fuzzy fault diagnostic system of mine drainage

A system to monitor the operational state of a coal mine drainage system is presented, fault problems are diagnosed and solved. The system includes a Single Chip Microprocessor (SCM) Atmega169 and an industrial PC used as a master-slave structure. Characteristic parameters of the drainage system were extracted and analysed. As well, a research project on the fault diagnosis of centrifugal water pump based on a fuzzy synthetic evaluation method is initiated. The proposed monitoring and fault diagnostic system can improve the automation, safety, reliability, economy and efficiency of mine drainage systems considerably, decrease blindness and shorten the time required for water pump maintenance.

English

The AMDTreat computer program ( . Treatment with caustic chemicals typically is used to increase pH and decrease concentrations of dissolved aluminum, iron, and/or manganese in largevolume, metal-laden discharges from active coal mines. Generally, aluminum and iron can be removed effectively at near-neutral pH (6 to 8), whereas active manganese removal requires treatment to alkaline pH (~10). The treatment cost depends on the specific chemical used (NaOH, CaO, Ca(OH)2, Na2CO3, or NH3) and increases with the quantities of chemical added and sludge produced. The pH and metals concentrations do not change linearly with the amount of chemical added. Consequently, the amount of caustic chemical needed to achieve a target pH and the corresponding effluent composition and sludge volume can not be accurately determined without empirical titration data or the application of geochemical models to simulate the titration of the discharge water with caustic chemical(s). http://amd.osmre.gov/ ) is widely used to compute costs for treatment of coal-mine drainage. Although AMDTreat can use results of empirical titration with industrial grade caustic chemicals to compute chemical costs for treatment of net-acidic or net-alkaline mine drainage, such data are rarely available. To improve the capability of AMDTreat to estimate (1) the quantity and cost of caustic chemicals to attain a target pH, (2) the concentrations of dissolved metals in treated effluent, and (3) the volume of sludge produced by the treatment, a titration simulation is being developed using the geochemical program PHREEQC (wwwbrr.cr.usgs.gov/projects/GWC_coupled/phreeqc/) that will be coupled as a module to AMDTreat. The simulated titration results can be compared with or used in place of empirical titration data to estimate chemical quantities and costs. This paper describes the development, evaluation, and potential utilization of the PHREEQC titration module for AMDTreat.

Passive Treatment of Acidic Coal Mine Drainage: The Anna S Mine Passive Treatment Complex

The Anna S coal mine complex in Tioga County, PA, produces drainage with a pH of 2.8–3.6 containing 3–36 mg/L Al, 1–36 mg/L Fe, and 6–9 mg/L Mn. In 2003, the Babb Creek Watershed Association installed two systems that passively treat three discharges from the mine complex. Both systems contain four parallel vertical flow ponds followed by aerobic wetlands. The vertical flow ponds contain a total of 35,483 t of limestone and 4,913 m3 of organic substrate. During the last 6 years, the systems have treated an average of 1,971 L/min of flow to neutral pH with 135–146 mg/L of alkalinity (as CaCO3), with less than 1 mg/L of Al and Fe, and 2–4 mg/L of Mn. The vertical flow ponds have generated alkalinity at rates of 32–53 g/m2/day as CaCO3. No seasonal variation in treatment effectiveness has been observed, despite relatively harsh winter seasons. The total cost of the passive systems was $2.5 million (US). The 20 year projected unit treatment cost, including periodic replacement of the organic substrate, is $403–618 per t (as CaCO3) of net alkalinity generated.

Recycling utilization patterns of coal mining waste in China

With the fast development of Chinese economy in recent years, China has become the largest coal production and consumption country in the world. Correspondingly, it has produced large quantities of mining waste including coal gangue, coal sludge, fly-ash, coal mine drainage and coal-bed methane (CBM) that are hazardous to the soil, air, and water. Based on the theory and practice of sustainable development and recycling economy, the paper will discuss and analyze the mining waste management in Jincheng Anthracite Mining Group, Shanxi Province, where they have found the paths to realize the mining waste reusing and recycling in colliery. They had established many green industrial chains in the mining waste treatment: the gangue piles turned into man-made eco-park, gangue used for power generation, fly-ash used in the building material, the coal mining water reused and recycled in closed pipelines, the CBM extracted for home-burning and electricity generation, etc. The coal mining waste has been converted into wealth and played more and more important roles in many fields. The practice indicated that these patterns can be applied in other coal mines.

Factors that influence coal mine drainage chemistry West Coast, South Island, New Zealand

Coal mine drainage chemistry on the West Coast of the South Island is highly variable; pH ranges from about 2–8, and chemical concentrations vary by several orders of magnitude. Factors that influence mine drainage chemistry on the West Coast include regional geology, mine type, hydrogeology, and local geology. At a regional scale, mine drainage chemistry is bimodal and relates to geological formations. Mines within the Paparoa Coal Measures have neutral mine drainage, whereas those within the Brunner Coal Measures have acid mine drainage. This is related to the availability of SO4 during coal measures deposition and, in combination with Fe and organic material, the subsequent formation of pyrite during burial. Paparoa Coal Measures were deposited in alluvial to lucustrine environments where SO4 was relatively unavailable, whereas Brunner Coal Measures were deposited in alluvial to estuarine to marginal marine settings where marine SO4 was abundant. Brunner Coal Measures acid mine drainage chemistry is influenced by mine type; open cast mines have Al- and trace element-rich acid mine drainage compared to underground mines. Acid mine drainage forming reactions that release trace elements and Al proceed more rapidly and completely at open cast mines where mine waste has a higher reactive surface area compared to waste rock at underground mines. Brunner coal mine drainage chemistry is also influenced by hydrogeology where flooded underground mines release less acid than free-draining mines because there is less oxygen available to react with pyrite. In addition, local geology overprints mine drainage chemistry where differences in acid mine drainage chemistry arise from changes in contributing lithologies either within a single mine or between different coalfields. Identification of factors that control mine drainage chemistry enables prediction of mine drainage chemistry. These predictions have application to the mining industry for managing, mitigating, monitoring, and remediation of mine drainages that would otherwise cause negative environmental impact.

Adsorption of arsenic by iron rich precipitates from two coal mine drainage sites on the West Coast of New Zealand

Dissolved As can be strongly adsorbed to fine grained Fe(III) minerals such as hydroxides, oxyhydroxides and hydroxysulphates. Therefore precipitates that form during neutralisation or treatment of acid mine drainage have potential to be useful for treatment of As-contaminated water because acid mine drainage is often Fe rich. We tested the adsorption properties of Fe(III) rich precipitates from two West Coast coal mines with As-contaminated water from an historic gold ore processing site near Reefton. Precipitates were collected from distinctly different settings, an active acid mine drainage treatment plant at Stockton mine and the neutralisation/oxidation zone of acid mine drainage discharge at the abandoned Blackball Coal Mine. The two mine sites produce precipitates with different compositions and mineralogy. Arsenic adsorption onto precipitates from each site was determined in batch and column tests under laboratory conditions. Batch experiments indicate As adsorption occurs rapidly during the first 5 h and reaches equilibrium after 24 h. At equilibrium, and for a dosing ratio of 50 g of precipitate per litre of water, As concentrations decreased from 99 mg/L to 0.0080 mg/L with precipitates from Stockton and to 0.0017 mg/L with precipitates from Blackball. Arsenic adsorption capacity is up to 12 mg/g on precipitates from Stockton sludge and 74 mg/g on precipitates from Blackball. The Blackball precipitate adsorbs more As than precipitates from Stockton which is probably due to the higher Fe oxide content but pH and surface structure could also play a role. The column experiment confirmed that adsorption of As from a continuous waste stream onto these precipitates is possible, and that passive remediation using this waste product mixed with gravel to enhance permeability could be a viable approach at As-contaminated mine sites.

Variability of Stockton Coal Mine drainage chemistry and its treatment potential with biogeochemical reactors

Thirteen acid mine drainage seeps emanating from waste rock dumps and associated sediment ponds were monitored at Stockton Coal Mine near Westport, New Zealand to identify and quantify metal loads and delineate their spatial and temporal variability. Dissolved metal concentrations ranged from 0.05–1430 mg/L Fe, 0.200–627 mg/L Al, 0.0024–0.594 mg/L Cu, 0.0052–4.21 mg/L Ni, 0.019–18.8 mg/L Zn, <0.00005–0.0232 mg/L Cd, 0.0007–0.0028 mg/L Pb, <0.001–0.154 mg/L As and 0.103–29.3 mg/L Mn and the pH ranged from 2.04–4.31. Currently this acid mine drainage is treated further downstream by a number of water treatment plants employing a combination of ultra fine limestone and Ca(OH)2. However, in the interest of assessing more cost-effective technologies, biogeochemical reactors were assessed in the laboratory as potential cost-effective passive treatment options. Results of mesocosm-scale treatability tests showed that biogeochemical reactors incorporating mussel shells, pine bark, wood fragments (post peel) and compost increased pH to >6.7 and sequestered ≥98.2% of the metal load from the Manchester Seep located within the Mangatini Catchment. Laboratory results demonstrated that the maximum loading rate was 0.8 mol total metals/m3 substrate, and an average of 20.0 kg/day (7.30 tonnes/year) of metals could be removed by appropriately sized biogeochemical reactors.

Correlation of acid base accounting characteristics with the Geology of commonly mined coal measures, West Coast and Southland, New Zealand

Assessment of the potential for waste rock at coal mine sites to produce acid mine drainage is an important part of mine planning and operations and is commonly assessed using acid base accounting analyses. The underlying factor that controls mine drainage chemistry is the mineralogical composition of the coal measures sequences which in turn is controlled by several geological factors including provenance, depositional environment, diagenetic processes and tectonic setting. Therefore, coal mine drainage chemistry is directly linked to the geology of coal measures sequences. Our research uses acid base accounting data to identify relationships between coal measures geology and acid production potential for Brunner, Paparoa and Morley Coal Measures as well as Gore Lignite Measures. Our data is from several sources and reflects areas in these sets of coal measures where mining or exploration is underway. In general Brunner Coal Measures are strongly acid producing especially fine grained rocks and this relates to a coastal depositional environment, common diagenetic pyrite, overlying transgressive marine rocks and compositional maturity. Morley and Paparoa Coal Measures are mostly non-acid forming relating to fluvial - lucustrine depositional environments, overlying coal measures, diagenetic carbonates, and possibly carbonates from source rocks. Gore Lignite Measures are mostly non-acid forming, however, some acid forming rocks are present. Gore Lignite Measures are delta plane deposits with occasional marine influence. Datasets from Brunner, Paparoa and Morley Coal Measures as well as Gore Lignite Measures also demonstrate some of the limitations of acid base accounting analyses. For example, oxidation steps in acid base accounting analyses designed to dissolve pyrite also react with organic material and this causes a false positive analysis. Other assumptions common in acid base accounting such as use of total S content to calculate pyrite related acidity are inappropriate for some samples because of other forms of S in these samples. Despite the interferences, standard acid base accounting tests and procedures are very useful for first pass predictions of mine drainage chemistry and datasets from commonly mined New Zealand coal measures can be successfully related to geological processes.

Promotion of Mn(II) oxidation and remediation of coal mine drainage in passive treatment systems by diverse fungal and bacterial communities.

Biologically active, passive treatment systems are commonly employed for removing high concentrations of dissolved Mn(II) from coal mine drainage (CMD). Studies of microbial communities contributing to Mn attenuation through the oxidation of Mn(II) to sparingly soluble Mn(III/IV) oxide minerals, however, have been sparse to date. This study reveals a diverse community of Mn(II)-oxidizing fungi and bacteria existing in several CMD treatment systems.

A preliminary study of coal mining drainage and environmental health in the Santa Catarina region, Brazil

The concentrations and loadings of major and trace elements in coal mine drainage (CMD) from 49 abandoned mines located in the coal fields of the Brazilian state of Santa Catarina were determined. The CMD sites typically displayed a wide spatial and temporal variability in physical and geochemical conditions. The results of our CMD analyses in Santa Catarina State were used to illustrate that the geochemical processes in the rock piles can be deduced from multiple data sets. The observed relationship between the pH and constituent concentrations were attributed to (1) dilution of acidic water by near-neutral or alkaline groundwater and (2) solubility control of Al, Fe, Mn, Ba and Sr by hydroxide, sulfate, and/or carbonate minerals. The preliminary results of the CMD analyses and environmental health in the Santa Catarina region, Brazil, are discussed.

Attenuation and diel cycling of coal-mine drainage constituents in a passive treatment wetland: A case study from Lambert Run, West Virginia, USA

Abstract This study reports changes in coal-mine drainage constituent concentrations through a passive treatment wetland and over diel cycles. The purpose of the study was to determine what physiochemical mechanisms control attenuation of metals and if they varied by location and through time. The source water was slightly acidic (average pH 5.43); downstream degassing of CO2 contributed to an increase in pH prior to discharge from the site (average pH 7.05). Aluminum, Fe, rare earth elements (REE) and Y were removed to a greater extent than were Mn, Co and Ni. At acidic pH, the REE and Y were generally complexed by SO4. At higher pH, carbonate complexes became more important. The REE and Y concentrations were normalized to the North American Shale Composite standard; the normalized patterns were coherent near the source but anomalies of Ce and Y were present further downstream indicating oxidation and sorption processes. Four sets of diel-based samples were collected, one from a shallow, surface-flow wetland and three from a deeper, newly constructed wetland. Well-defined diel cycles were observed for concentrations of Si, Mn, Fe, Co, Ni, As, REE and Y in the shallow wetland. In all cases, the concentrations increased (up to 863%) during night and decreased during the day. These cycles had an inverse relationship with the temperature cycle (pH had no discernable cycle). The consistency of concentration cycles suggests a common mechanism, most likely associated with the formation of Fe oxyhydroxides. The increased rate of Fe2+ oxidation in warm water can account for the cycles in Fe; scavenging of the other elements by the Fe precipitate can account for the consistency of the cycles even though the elements include cations, anions ( H 2 AsO 4 - or HAsO 4 - 2 ), and neutral species ( H 4 SiO 4 0 ). While REE and Y had clear cycles in the constructed wetland, the other elements did not. This is partially due to the lower elemental concentrations (including Fe) but the cycles may also be damped by the deeper, slower-moving water. This study illustrates the dynamic nature of metal removal in passive treatment systems. Furthermore, it suggests that grab samples collected during daytime hours may underestimate the concentrations and flux of metals in these systems.