Characterization Of Mine Waste Research Articles

Characterization of Mine Waste from a Former Pb–Zn Mining Site: Reactivity of Minerals During Sequential Extractions

An integrated mineralogical and chemical characterization approach was applied to different types of mine waste collected from the ancient Pb–Zn mining area of Plombières. The combination of different methods to determine (pseudo-)total element concentrations, sequential extractions, and quantitative mineralogical analysis provided detailed information on the reactivity of minerals in the waste, as well as the associated metal(loid) release under different experimental conditions. Lithium borate (LiBO2) fusion was not suited to determine total metal(loid) concentrations in the investigated mine waste samples, due to the incomplete dissolution of the samples, and the volatilization of As and Cd during the fusion. Because some elements were below detection limit of X-ray fluorescence spectrometry (e.g., Cd), aqua regia digestion was useful to complement the chemical sample characterization, bearing in mind that only pseudo-total concentrations could be determined. Galena (PbS) and its alteration products, cerussite and anglesite (PbSO4), were the main lead minerals associated with the mining waste. Because of the high cerussite (PbCO3) content of the investigated samples (2–5 wt%), Pb not only shows the highest potential for recovery from the mining waste, but it also poses the highest environmental and human health risk. Zinc minerals showed a lower reactivity towards the BCR sequential extraction (sphalerite, ZnS) or were less abundant (willemite, Zn2SiO4). Quantitative XRD analysis allowed for better evaluation of the incomplete dissolution of some minerals, improving the interpretation of the sequential extraction results.

Trace elements leaching from Pb[sbnd]Zn mine waste (Plombières, Belgium) and environmental implications

The geochemical and mineralogical characterization of mine waste provides essential information to understand the environmental and health impacts and to adequately manage present and historical mine waste sites. In the present study, mine waste samples from a former ZnPb mining site were subjected to different types of leaching tests, an in-vitro bioaccessibility test, and a mineralogical analysis. The samples were characterized by elevated pseudo-total Pb (up to 51,800 mg/kg), Zn (up to 60,100 mg/kg), Cd (up to 429 mg/kg), and As (up 3170 mg/kg) concentrations, and contained, among other minerals, cerussite (PbCO3) and galena (PbS). Lead is not only present in abundant concentrations, but also in highly bioaccessible forms, as determined from the in-vitro bioaccessibility test. This indicates the high risks posed in the case of ingestion of fine dust particles. The partial dissolution of the Pb-bearing minerals as a function of pH was modeled using PHREEQC geochemical software and was compared with experimental data. The high Pb release is mainly controlled by the dissolution of cerussite, even at natural pH values. X-ray diffraction analyses revealed that the amount of cerussite decreased (by ≥50%) in all samples as a consequence of leaching with water. Other Pb and Zn minerals present in the samples also dissolved when extracted with water, but not to the magnitude of cerussite. Although the mining site has been inactive for over 100 years, the high concentrations of metal(loid)s within the samples are still evident. Not only are the metals present in high concentrations, but also as mobile forms, especially when pH changes. This study proved to be essential in understanding the different parameters controlling metal(loid)s and in identifying the potential threats the mine waste poses to human health and the environment. From this overall assessment, proper methods for an effective recovery or reprocessing of the mine waste can be further evaluated.

Assessment and Characterization of Mine Waste and Fly Ash Material for Effective Utilization in Opencast Coal Mines

Coal is a major source of nonrenewable energy in India. Most of the Industries depend on the coal to meet the energy demand of the country. Coal mining is invariably associated with the generation of voids. The voids so generated are often filled with overburden (OB) and waste materials. To enhance the utilization, fly ash (FA) is also being used for filling the voids. However, these operations inevitably require excessive planning and control to minimize the environmental impact of mining. In order to evaluate the impact of backfilling the voids with coal mine wastes and fly ash, Overburden and fly ash materials have been collected from Talcher coalfield. The geotechnical characterization study of overburden (OB) sample and OB+30% fly ash samples have been carried out separately for backfilling. After addition of fly ash, it is observed that the permeability is increased but liquid limit, plastic limit, and plasticity index (PI) of the OB are decreased. The maximum dry unit weight of OB mixture decreases while optimum water content increases with the fly ash. The angle of internal friction of OB decreases after addition of the fly ash. Cohesion value of OB sample has not changed much after addition of the fly ash. The grain size analyses results show OB sample is poorly graded. The OB soil type is found to be poorly graded sand of low compressible clay (SP-CL). Similarly, the OB+30% fly ash soil type is of poorly graded sand of low compressible silty (SP-ML) type. The OB and OB+ 30% fly ash contain heavy metals such as Fe and Al in high quantity, mild concentrations of Zn, Cr, and Mn and low amounts of Cu, Co, As, and Se. B and Pb are found below the detection level. The decreasing order of heavy metals in the leachate samples observed to be Fe>Mn>Ni>Cu>Zn>Se>Co>Cd>Cr>As. The major mineral phases in OB and OB+30% fly ash samples are found to be quartz, kaolinite, muscovite, dickite, zinnwaldite, and illite.

Environmental characterization of mine waste at the Pb–Zn Sidi Kamber abandoned mine (NE Algeria)

The mining wastes coming from Sidi Kamber mine stored at the surface are exposed to weathering conditions, which favour the leaching of toxic metals into the environment. This situation presents serious risks for humans and ecosystems. To better understand this problem, eight representative samples of Sidi Kamber mine tailing were taken from the surface along two vertical trenches and tested using static and dynamic leaching tests. The studied samples present a wide diversity in terms of particle size distribution, mineralogical and chemical compositions. These parameters may greatly affect the reaction rates. The mineralogical investigations show the presence of various sulphide minerals, such as pyrite, galena, sphalerite and chalcopyrite which are present in either free and/or associated with gangue minerals (i.e. quartz, albite, chlorite and muscovite). Moreover, the presence of only minerals with low neutralizing potential such as silicates, promotes the acid mine drainage generation, which is characterized by high concentrations of metals and sulphates. Leaching tests showed an acidic pH and the release of some toxic contaminants (i.e., Pb, Zn and Cu), which exceed the recommended limits (Algerian regulation law for industrial wastewater and US EPA thresholds).

Characterization of Mine Waste and Acid Mine Drainage Prediction by Simple Testing Methods in Terms of the Effects of Sulfate-Sulfur and Carbonate Minerals

Characterization of mine waste rocks and prediction of acid mine drainage (AMD) play an important role in preventing AMD. Although high-tech analytical methods have been highlighted for mineral characterization and quantification, simple testing methods are still practical ways to perform in a field laboratory in mines. Thus, this study applied some simple testing methods to the characterization of mine wastes and AMD prediction in addition to a leaching test and the sequential extraction test with HCl, HF, and HNO3, which have not been applied for these purposes, focusing on the form of sulfur and the neutralization effects of carbonates. The results of the Acid Buffering Characteristic Curve test supported the changing trend of the pH attributing carbonates only during the first 10 leaching cycles in the leaching test. The change in the Net Acid Generating (NAG) pH in the sequential NAG test reflected the solubility of sulfur in the rocks, providing information on the form of sulfur in the rocks and the acid-producing potential over time. Consequently, the sequential NAG test and sequential extraction with the acids in combination with the current standards tests (Acid Base Accounting and NAG tests) provided important information for preventing AMD.

Characterization of unsaturated mine waste: a case history

It is becoming increasingly common in the mining industry for either crushed ore or filtered mine waste to be stacked to a significant height (>100 m) in a moist state with little compaction, resulting in deposits that can be potentially loose and unsaturated. This paper presents a case history describing the characterization of stacked filtered tailings at a mine site in South America. Cone penetration tests with pore pressure and seismic velocity measurements (SCPTu) were carried out along with selected drilling, sampling, and laboratory testing. Compression wave velocity (Vp) and shear wave velocity (Vs) profiles were obtained and compared with laboratory values on reconstituted saturated and unsaturated samples. Results indicate that shear wave velocity is sensitive to suction hardening effects and appears to capture the correct unsaturated in situ behavior. The cone resistance, which is a large strain measurement, can destroy the beneficial effects of suction hardening and appears to be insensitive to the unsaturated in situ behavior, but may capture the correct behavior after the beneficial effects of suction are removed if the soil becomes saturated.

Improved mine waste characterisation through static blended test work

Prediction of the geoenvironmental characteristics of mine waste materials typically relies on the static and kinetic testing of individual waste units. In reality, waste rock piles are heterogeneous landforms containing potentially acid forming (PAF) units juxtaposed with non-acid forming (NAF) units. Despite this, predictive geoenvironmental test work programs rarely characterise blends of waste materials. Through undertaking laboratory-based blended static testing and mineralogical assessments, a first insight into the leachate chemistry of a waste landform can be ascertained. This was tested using three waste units (Type A – alkaline, B – neutral and D – PAF; n=31) obtained from the Savage River mine, Western Tasmania. Seven daughter blend types (1–7; n=42) were prepared using different ratios of the individual waste types, and characterised by acid base accounting and mineralogical techniques. Blend types were NAF when a maximum of 20% of Type D was used, with daughter blend 4 (90% Type A+10% Type D) the most inert when screened against ANZECC (2000) aquatic protection trigger values. This study demonstrates that through first-pass static blended testing, opportunities exist to improve waste-rock handling practices and design NAF waste piles once field trials, involving a range of particle sizes, have been conducted.

Ecological potential of Epilobium dodonaei Vill. for restoration of metalliferous mine wastes

Metalliferous mine wastes represent one of the major sources of environmental contamination from mining activities. Bor region (Serbia) is one of the largest copper mine basins in Europe where long-term mining caused severe environmental deterioration and created one of the most degraded locations in Serbia and Europe. At the spontaneously colonized metalliferous mine wastes in Bor, plant species Epilobium dodonaei dominates in the mine slopes and mine waste surfaces. Epilobium dodonaei has the status of endangered and protected species in parts of European range (i. e. plant is included in the Red lists of the countries in the Carpathian mountains region), primarily due to losses of natural gravel habitats. The main focus of this research was physico-chemical characterization of mine waste, assessment of phytoremediation potential and plant metabolic stress response of Epilobium dodonaei at the hot spot metalliferous mine site in order to evaluate the possibility for application of endangered species in ecological restoration. The Bor mine wastes are characterized by coarse soil texture, various pH (4.58–8.30), and elevated concentrations of arsenic (44.5–271mgkg−1) and copper (311–2820mgkg−1) that exceed the Serbian limiting threshold and remediation values. Oxidation of metal-sulfide minerals on waste surface leads to increased acidity, followed by elevated metal mobility of the mine spoil solution. Content of arsenic, copper, lead and zinc in roots of E. dodonaei was correlated with pseudo-total and EDTA-available concentrations in Bor mine spoils. Furthermore, the content of arsenic, copper, lead and zinc in roots (3.98mgkg−1, 140mgkg−1, 3.19mgkg−1, and 72.8mgkg−1, respectively) and shoots (4.69mgkg−1, 57.7mgkg−1, 1.17mgkg−1, and 59.3mgkg−1, respectively) of E. dodonaei reflected the multi-metal pollution at the investigated site. Epilobium dodonaei largely retains copper, lead and zinc in roots than in shoots and has the potential for phytoremediation of mine wastes. Epilobium dodonaei at Bor mine spoil had a high content of malondialdehyde in roots and leaves as well as reduced chlorophylls and carotenoids content in leaves, indicating great oxidative stress. However, elevated arsenic and copper content could promote biosynthesis of antioxidants in roots and leaves of E. dodonaei at mine spoil. Creation of an endangered species habitat on mine waste rocks of the Bor mining area and similar sites of Carpatho-Balkan metallogenic province could successfully contribute to the preservation of E. dodonaei. Development of practical procedures for the selection and application of endangered plant species in reclamation should create stronger link between ecological restoration and conservation biology. Finally, the application of endangered plant species should take a more prominent role in the restoration process and ecosystem design.

Size-dependent characterisation of historical gold mine wastes to examine human pathways of exposure to arsenic and other potentially toxic elements.

Abandoned historical gold mining wastes often exist as geographically extensive, unremediated, and poorly contained deposits that contain elevated levels of As and other potentially toxic elements (PTEs). One of the key variables governing human exposure to PTEs in mine waste is particle size. By applying a size-resolved approach to mine waste characterisation, this study reports on the proportions of mine waste relevant to human exposure and mobility, as well as their corresponding PTE concentrations, in four distinct historical mine wastes from the gold province in Central Victoria, Australia. To the best of our knowledge, such a detailed investigation and comparison of historical mining wastes has not been conducted in this mining-affected region. Mass distribution analysis revealed notable proportions of waste material in the readily ingestible size fraction (≤250µm; 36.1-75.6%) and the dust size fraction (≤100µm; 5.9-45.6%), suggesting a high potential for human exposure and dust mobilisation. Common to all mine waste types were statistically significant inverse trends between particle size and levels of As and Zn. Enrichment of As in the finest investigated size fraction (≤53µm) is of particular concern as these particles are highly susceptible to long-distance atmospheric transport. Human populations that reside in the prevailing wind direction from a mine waste deposit may be at risk of As exposure via inhalation and/or ingestion pathways. Enrichment of PTEs in the finer size fractions indicates that human health risk assessments based on bulk contaminant concentrations may underestimate potential exposure intensities.

Prediction of the long-term performance of abandoned lead zinc mine tailings in a Welsh catchment

In this study we investigated the sulphidic mine tailings from Frongoch and Grogwynion, two abandoned lead zinc mines in mid-Wales, UK. Despite falling within the same ore field the mine waste characterisation has identified differences in the tailings from the two sites. Bulk concentrations range from 10 to 52 g kg − 1 for Pb, 1.1 to 2.9 g kg − 1 for Zn in Grogwynion and from 1.0 to 130 g kg − 1 for Pb, 11 to 110 g kg − 1 for Zn in Frongoch. An experimental (European standard leaching tests TS 14429 and TS 14405) and geochemical modelling approach was used to study the leaching composition as a function of pH and liquid/solid ratio. There was little correlation between the tailings bulk metal concentrations and the leachate composition, but variations in Pb and Zn concentrations were found to be consistent with control of dissolved Pb and Zn by secondary minerals and the mechanisms of dissolution/precipitation/sorption involving them. Specifically, the Grogwynion mine tailings with near-neutral pH have predominantly lead and zinc carbonates controlling Pb and Zn solubility in the leachates, whereas the Pb and Zn concentrations in Frongoch leachates are best modelled with a surface complexation model for metal sorption to oxyhydroxides. The different speciation results in a greater sensitivity of Grogwynion tailings to acidification with a potential release of Pb in solution up to 10 times higher than in Frongoch, despite similar bulk Pb concentrations. At acid pH, Zn is similarly dissolved to a greater extent in Grogwynion than in Frongoch tailings. There was no evidence of sulphide oxidation during the batch and column leaching tests and the suitability of using these European leaching standards for the characterisation of sulphidic mine waste materials for waste management purposes has been considered.

Characterization of Zinc, Lead, and Cadmium in Mine Waste: Implications for Transport, Exposure, and Bioavailability

We characterized the lability and bioaccessibility of Zn, Pb, and Cd in size-fractionated mine waste at the Tar Creek Superfund Site (Oklahoma) to assess the potential for metal transport, exposure, and subsequent bioavailability. Bulk mine waste samples contained elevated Zn (9100 +/- 2500 ppm), Pb (650 +/- 360 ppm), and Cd (42 +/- 10 ppm), while particles with the greatest potential for windborne transport and inhalation (< 10 microm) contained substantially higher concentrations, up to 220 000 ppm Zn, 16 000 ppm Pb, and 530 ppm Cd in particles < 1 microm. Although the mined ore at Tar Creek primarily consisted of refractory metal sulfides with low bioavailability, sequential extractions and physiologically based extractions indicate that physical and chemical weathering have shifted metals into relatively labile and bioaccessible mineral phases. In < 37 microm mine waste particles, 50-65% of Zn, Pb, and Cd were present in the "exchangeable" and "carbonate" sequential extraction fractions, and 60-80% of Zn, Pb, and Cd were mobilized in synthetic gastric fluid, while ZnS and PbS exhibited minimal solubility in these solutions. Our results demonstrate the importance of site-specific characterization of size-fractionated contemporary mine waste when assessing the lability and bioavailability of metals at mine-waste impacted sites.