Gold Mine Tailings Research Articles

Physiological and ultrastructural studies of Jatropha curcas and Reutealis trisperma in response to gold-mine tailings

Abstract. Prasetya DN, Hamim, Sulistyaningsih YC. 2022. Physiological and ultrastructural studies of Jatropha curcas and Reutealis trisperma in response to gold-mine tailings. Biodiversitas 23: 3471-3479. Heavy metal contamination through tailings from mining pollutes the environment and harms human health. This study aimed to analyze physiological, especially ultrastructural changes and the photosynthetic activities of Jatropha curcas and Reutealis trisperma in response to gold mine tailings. J. curcas and R. trisperma were grown in 8 kg of polybags and treated with 0%, 50%, and 100% gold mine tailings for three months before examining their morphological, physiological, and leaf ultrastructure. The results showed that gold mine tailings with 50% and 100% concentrations affected the growth of both species. This was indicated by reduced plant height, total leaf number, shoot, root dry weight, and decreased chlorophyll and carotenoid content. Furthermore, treatment of gold mine tailing at 50% and 100% induced lipid peroxidation, indicated by the significant increase in leaf malondialdehyde content. The photosynthetic and transpiration rates at 90 days after treatment decreased with the increase in gold mine tailings concentration. The leaf ultrastructure analysis showed high-level tailings of treatment-induced ultrastructure alteration of J. curcasand R. trisperma. However, these changes did not significantly affect the photosynthesis rate, hence the plants survived until the end of the observation period. The overall effect of tailings on R. trisperma was lower than on J. curcas, suggesting that R. trisperma had higher adaptability than J. curcas.

An In Toto Approach to Radon Dispersion Modelling from a South African Gold Mine Tailings.

The USA Environmental Protection Agency’s (EPA) Industrial Source Complex Short Term 3 (ISCST3) dispersion modelling code was used to evaluate radon transport and the effects of local variations around tailings dam using a Gaussian plume model. The tailings dam was modelled as point, flat ground and top level, total emitting surface area (true geometry) and volume source geometries. The true area geometry was considered as the baseline source geometry. To improve the accuracy of the model predictions as compared to traditional approaches, the true geometry area source term was corrected to account for cracks and fissures on the tailings and the geometry of tailings dam was modelled by considering all emitting surfaces as sources. Compared to the baseline, the model overpredicted the flat ground area source by up to 274% and underpredicted the top-level area source by up to 50%. The volume emission source was overpredicted by up to 300% in 60% of the modelling runs and underpredicted by 55% in 40% of the volume model runs. While the top-level area source term produced lower concentrations at near-field ground-level receptors, accounting for the wakes effect increased the radon concentrations from the top-level area source of the tailings dam by up to 239%. From the modelling results, the highest concentration predicted by the model from the true geometry source was found to be 0.843 Bq m−3, which corresponds to the dose of 0.012 mSv/y to the public due to radon from the tailings. This value is less than the 1 mSv/y dose constraint stipulated by the National Nuclear Regulator.

Potential Uses of Artisanal Gold Mine Tailings, with an Emphasis on the Role of Centrifugal Separation Technique

Few investigations have focused on the potential uses of artisanal gold (Au) mine tailings, despite the fact that artisanal gold mining activity contributes to environmental issues such as greenhouse gas. Mineralogical characterizations of artisanal gold mine tailings in Miyove gold mine (Baradega and Masogwe) in Rwanda were investigated for potential utilization as a source of valuable gold, using the centrifugal separation technique. Results of X-ray diffraction analysis, energy dispersive X-ray spectroscopy, inductively coupled plasma mass spectrometry, inductively coupled plasma–optical emission spectroscopy, and X-ray fluorescence showed that artisanal gold mine tailings samples have significant amounts of gold to justify economical gold extraction opportunity. The gold grades in the ores and artisanal gold mine tailings were in the ranges of 37–152 and 2–7 g t−1, respectively. Quartz was a major phase, with minor impurities in two different types of gold ores and their respective tailings. The beneficiation carried out using centrifugal separation, regarded as an extension of gravity separation, showed gold grades in the range of 535–1515 g t−1 for gold ores and 36–302 g t−1 for artisanal gold mine tailings. The gold recoveries for ores and artisanal gold mine tailings were in the range of 21.8–47.3% and 46.9–63.8%, respectively. The results showed that the centrifugal separation technique was more efficient in boosting gold recovery compared to the present panning approach employed at the site, which sometimes recover as low as 10%. The results suggest that mineralogical characterization of artisanal gold mine tailings allows for the development and design of a suitable methods for improving gold ore beneficiation and artisanal gold mine tailings reprocessing.

Ecological risk of trace metals in soil from gold mining region in South Africa

The Witwatersrand basin in South Africa is one of the well-known gold mining regions worldwide. Plausibly, it is one of the sites in South Africa with the highest environmental impact emanating from trace metal contamination. This study assessed the concentration of Fe, S, Cu, Mn, Cr, Zn, Ni, Co, P, Mo using inductively coupled plasma optical emission spectrometry on 21 soil samples that were collected from 9 independently located historical gold mine tailings. The results revealed high mean concentration (mg/kg) for Fe (36,433.39) > S (5,071.83) > Cu (1,717,28) > Mn (612.81) > Cr (74.52) > Zn (68.67) > Ni (40.44) > Co (9.63) > P (3.49) > Mo > (2.74) in the samples investigated. Estimated degree of contamination by using contamination indices calculations showed that the sites surveyed are on average low to moderately contaminated with Co, Cr, Cu, Mn, Ni, S, and Zn. The trace metals that are most likely to cause ecological risk incorporate Mn and Cu, especially at Durban Deep. While the health risk assessment revealed a low ecological risk (Eri) of Cr, Ni, and Zn, the Eri estimates showed that the residents in the study area are prone to health risk mainly from the covetous effects of Cu (320 ≤ Eri). The residents of the study area are low income earners and the possibility that they can relocate is nonexistent. Thus, mitigation strategies are required to avoid eminent health risks and restraining housing developments near the tailing dumps.

Biochar Promotes the Germination and Growth of Herbaceous Seeds Hydroseeded on Gold Mine Tailings

Biochar Promotes the Germination and Growth of Herbaceous Seeds Hydroseeded on Gold Mine Tailings

Instability of gold mine tailings subjected to undrained and drained unloading stress paths

The drained instability of two gold mine tailings under lateral stress relief is investigated in this study. Constant deviator stress (CDS) unloading tests were performed using a triaxial apparatus to examine instability imposed by unloading in a drained condition. Instability was induced by enforcing a constant deviator stress while simultaneously reducing the mean effective stress. Stress paths and shear strengths of CDS tests were compared with undrained triaxial tests on comparable specimens which were anisotropically consolidated to the same initial stress ratios of the CDS tests. Several techniques were employed to determine the onset of instability in the CDS tests. The effects of unloading rate and initial stress ratio on the behaviour and the triggering of instability in the CDS tests were further investigated. It was observed that specimens consolidated to the same void ratio and initial stress ratio undergo instability at similar stress ratios or friction angles in both CDS and undrained shear tests. This suggests that the instability characteristic of tailings prone to stress relief can be predicted using undrained triaxial tests on anisotropically consolidated specimens. Critical states and state parameters of specimens subjected to CDS and unloading stress paths were also compared and analysed.

Application of nanoporous ceramic membrane derived from Fe/S/Si/Al/O-rich mining solid waste in oil–water separation and heavy metal removal of industrial high concentrated emulsifying wastewater

Ceramic membranes are widely used in industrial wastewater treatment due to their excellent chemical stability, thermal stability, high oil cut-off rate, and long-term recyclability. However, its application range is limited because of the high price of commercial ceramic membranes. In this study, a low-cost environment-oriented ceramic membrane was prepared from gold mine tailings and SiO2-rich granite waste slag by sintering method. The Fe/S/Si/Al/O enriched ceramic membrane prepared by sintering in an atmospheric atmosphere was beneficial to the application of oil–water separation and heavy metal removal of industrial high concentrated emulsifying wastewater. At lower sintering temperature (1000 ℃), adding 33.3% gold tailings (M3), the membrane had good oil cut-off performance (96.1%) and stability. 29.47 MPa mechanical strength and 2.75% mass loss of 1000-M3 was confirmed under extreme acidic and alkaline conditions, and even in high-temperature environments, the mass loss was only 2.5%. After 16 cycles of performance test, the oil cut-off rate only decreased by 0.01%. The developed membrane exhibited good chemical stability and thermal stability. Based on the analysis of membrane contamination behavior, the ceramic membranes prepared could restore nanoporous channels only by ultrasonic treatment. In addition, 100% removal performance of iron and copper was obtained, and 78.6% removal efficiency was achieved for Chromium and cadmium. These fascinating characteristics make the novel ceramic membrane an excellent candidate with a high oil–water separation ability. More importantly, the inexpensive materials from recyclable solid waste and low-energy consumption preparation technique make it possible to scale up production. Thus, the as-prepared nanoporous ceramic membrane prepared from gold mine tailings with biological toxicity as hazardous waste has the potential of waste resource utilization for treating industrial grade high load emulsion wastewater.

Investigation of metal mobility in gold and silver mine tailings by single-step and sequential extractions

Metal leachate from mine tailings has the potential to release toxic metals into the surrounding environment. A single-step extraction procedure mimicking rainwater and a three-step BCR sequential extraction procedure (acid, reducing and oxidizing conditions) were applied to gold (GMT) and silver (SMT) mine tailings. Major (Al, Ca, Fe, Mg, and Mn) and trace metals were monitored to better understand the mobility and geochemistry of these metals when exposed to various environmental leaching conditions. Rainwater extraction released only small quantities of metals, while the three-step BCR extraction was more effective in mobilizing metals from the tailings. Under the acidic conditions of BCR step 1, Ca, Mg, Cd, Cu, and Mn were released in high concentrations. The dissolution of Fe, Ca, and Mg were dominant along with Pb in step 2 (reducing conditions). In step 3 (oxidizing conditions), Fe was the most dominant species together with Co, Cu, Ni, and Se. A high fraction of Al, Be, Cr, Li, Mo, Sb, Tl, and V remained in the residue. From SMT, larger quantities of As, Ca, Cd, and Zn were released compared to GMT. The BCR extraction could be applied to tailings to predict the potential release of toxic metals from mine wastes; however, excessive amounts of Ca and Fe in the tailings could cause carry-overs and incomplete extraction and carry-overs, resulting in a misinterpretation of results.

Life cycle assessment as a design consideration for process development for value recovery from gold mine tailings

With the decline of gold grades of primary resources in many parts of the world, gold recovery from primary resources may become unprofitable. Therefore, the identification of secondary gold resources (such as mine tailings) to prolong the existence of the gold industry has developed growing interest. Life cycle assessment (LCA) was used to design two process flowsheets (cyanide and thiosulphate) for recovering gold from a hypothetical tailings dam scenario in the West Witwatersrand region of South Africa while reducing environmental impacts of processes. The thiosulphate flowsheet reduced environmental impacts for 18 out of 19 impact categories compared to the cyanide flowsheet, apart from the freshwater consumption. The flowsheets proposed reduced sulphide, uranium, and arsenic in mine tailings by 82%, 75% and 94% respectively. Therefore, the solutions presented reduce environmental impacts associated with acid mine drainage, radionuclides and arsenic while producing gold as a value stream. The LCA model and corresponding sensitivity analysis showed that South Africa’s dependency on coal for electricity generation was a major contributor to environmental impacts for both flowsheets and transition to renewable energy can reduce environmental impact of mining operations.

Instability of a Gold Mine Tailings Subjected to Different Stress Paths

Static liquefaction of mine tailings has been the interest of many studies as these materials are generally deposited in a loose condition and stored at high saturation ratios. Yet few researchers have investigated the behavior of mine tailings in stress paths involving extensional consolidation or shearing in extension. In this study, the results of a set of experiments aimed at investigating the static liquefaction behavior of saturated loose gold mine tailings samples in triaxial compression and extension shear tests are described. Monotonic tests are carried out on isotropically and K0-consolidated samples to assess the effect of stress-induced anisotropy and mode of shearing on the instability and critical state behaviors of tailings. The comparison of undrained extension and compression shearing behaviors of samples consolidated to similar densities and stress conditions show a profound difference in their undrained shearing responses. This is attributed to the angular shapes of tailings particles that amplify the effects of particle orientation and sample fabric, as well as microstructural changes induced by different loading paths. Postliquefaction and yielding undrained shear strengths and effective friction angles from different modes of consolidation and shearing are examined. In both undrained compression and extension tests, tailings samples exhibit a limited liquefaction behavior after yielding, followed by a strain-hardening (dilative) behavior. Differences in tailings behavior under different loading directions and anisotropic stresses indicate the importance of considering the effects of these phenomena on the stability analysis of mine tailings dams.

Geochemical and mineralogical characteristics of some gold mine tailings in the Eastern Desert of Egypt

Geochemical and mineralogical characteristics of some gold mine tailings in the Eastern Desert of Egypt

Insight into soilless revegetation of oligotrophic and heavy metal contaminated gold tailing pond by metagenomic analysis

Soilless revegetation is an efficient way for gold tailing remediation, and micro-ecological environments in plant rhizosphere are important for vegetation establishment and pollution removal. In the present study, a field experiment of soilless revegetation has been carried out in a gold tailings pond, and the key genera and functional genes in the plant rhizosphere of gold mine tailings were revealed by metagenomics analysis. Soilless revegetation significantly decreased rhizosphere tailing pH from 8.54 to 7.43–7.87, reduced heavy metal (HM) concentration by 29.81–44.02% and enhanced the nutrient content by 50.30–169.50% averagely. Such improvements were strongly and closely correlated to microbial community and functional gene composition variation. The relative abundance of ecologically beneficial genus such as Actinobacteria (increased 9.7–18.8%) and functional genes involved in carbon, nitrogen and phosphorus cycling such as pyruvate metabolism (relatively increased 8.7–15.0%), assimilatory (increased to 1.44–2.08 times), phosphate ester mineralization (increased to 1.12–1.29 times) and phosphate transportation (increased to 1.28–1.85 times) were significantly increased. Moreover, the relative abundance of most As and Zn resistance genes were reduced, which may relate to the decrease of As and Zn concentration in the rhizosphere tailings. These results revealed the correlation among HM concentrations, microbial composition and functional genes, and provided clear strategies for improving gold mine tailing ecological restoration efficiency.

Physical Disturbance Reduces Cyanobacterial Relative Abundance and Substrate Metabolism Potential of Biological Soil Crusts on a Gold Mine Tailing of Central China.

As the critical ecological engineers, biological soil crusts (biocrusts) are considered to play essential roles in improving substrate conditions during ecological rehabilitation processes. Physical disturbance, however, often leads to the degradation of biocrusts, and it remains unclear how the physical disturbance affects biocrust microorganisms and their related metabolism. In this study, the photosynthetic biomass (indicated by chlorophyll a), nutrients, enzyme activities, and bacterial communities of biocrusts were investigated in a gold mine tailing of Central China to evaluate the impact of physical disturbance on biocrusts during the rehabilitation process of gold mine tailings. The results show that physical disturbance significantly reduced the photosynthetic biomass, nutrient contents (organic carbon, ammonium nitrogen, nitrate nitrogen, and total phosphorus), and enzyme activities (β-glucosidase, sucrase, nitrogenase, neutral phosphatase, and urease) of biocrusts in the mine tailings. Furthermore, 16S rDNA sequencing showed that physical disturbance strongly changed the composition, structure, and interactions of the bacterial community, leading to a shift from a cyanobacteria dominated community to a heterotrophic bacteria (proteobacteria, actinobacteria, and acidobacteria) dominated community and a more complex bacterial network (higher complexity, nodes, and edges). Altogether, our results show that the biocrusts dominated by cyanobacteria could also develop in the tailings of humid region, and the dominants (e.g., Microcoleus) were the same as those from dryland biocrusts; nevertheless, physical disturbance significantly reduced cyanobacterial relative abundance in biocrusts. Based on our findings, we propose the future work on cyanobacterial inoculation (e.g., Microcoleus), which is expected to promote substrate metabolism and accumulation, ultimately accelerating the development of biocrusts and the subsequent ecological restoration of tailings.

Production of gold mine tailings based concrete pavers by substitution of natural river sand in Misisi, Eastern Congo

For nearly a decade, the artisanal and small-scale gold mining (ASGM) in Misisi, eastern Congo, has been storing piles of gold mining tailings (GMT) from cyanide leaching. These tailings are stored carelessly in the nature without respect for environmental and sanitary standards, leading to soil and underground pollution risks. In order to valorize the GMT of Misisi, they were incorporated in concrete and from this concrete, pavers were produced. In addition to GMT, these pavers are made of gravel, cement and water. The compressive strength of the GMT-based pavers was compared with that of the natural river sand (NRS)-based pavers made up of NRS, gravel, cement and water. Both types of pavers were produced under the same drying conditions (7 days) with different dosages of gravels, cement and water for each type. More gravel and water were used for the GMT-based pavers with the same amount of cement for both types of pavers. The compressive strength was similar between GMT and NRS pavers with a breaking stress of 27 N/mm2. It was found that the use of a specific dosage for GMT-based pavers that differs from the dosage of NRS-based pavers had a positive impact on their compressive strength, specifically due to the larger amount of gravel used for GMT-based pavers. This paper shows that the production process of pavers also had an impact on their compressive strength. The particle size, elemental chemical characteristics and organic content were favorable for GMT to substitute NRS. The GMT consist of 75% sandy aggregate with an organic matter content of 4.49% and 52% of silica. This study consists of a first global vision of the possibility of total substitution of NRS by GMT in concrete pavers. The study's aims is to provide a perspective of the substitution of NRS by GMT in concrete paver production. Further studies of mechanical properties and durability will be necessary before considering a large scale adoption.

Polyethylene Terephthalate Waste as a Mobilizer for Heavy Metals in Gold Mine Tailings

The accumulation of gold mine tailings (GMT) and polyethylene terephthalate plastic waste (PW) continue to impact the ecosystem negatively, and strategies are required to counteract these issues to maintain a sustainable environment. This study investigated the use of PW as a binder to mobilize heavy metals in GMT. Plastic was used as a binder to develop specimens. were developed using plastic as a binder, the geotechnical and geochemical properties of the specimens were studied. The leachability of heavy metals from developed specimens was also studied. GMT and PW ratios of 80:20; 70:30, and 60:40 were investigated. The mineralogy and elemental composition of GMT and developed specimens showed that was quartz and silicon oxide were the predominant constituent in the materials. The specimen with the highest unconfined compressive strength yielded the lowest water absorption. The concentration of heavy metals in the PW-based specimens was lower than in the raw GMT. Waste plastic can be used as a sustainable binder to mobilize contaminants in GMT. The proposed solution can solve and prevent environmental pollution caused by GMT and WP.

Immobilization of mercury in tailings originating from the historical artisanal and small-scale gold mining using sodium polysulfide.

A series of sodium polysulfides (SPSs) with different sulfur indexes was prepared as stabilizers to amend elemental mercury-contaminated artisanal small-scale gold mine (ASGM) tailings in Hubei, China, by controlling the molar ratio of sulfur and sodium sulfides as 1:1, 2:1, 3:1, and 4:1 during the synthesis. XRD, XPS, and laser Raman spectroscopy all suggested that the synthesized SPSs were a mixture of multiple polysulfides, sulfur, sodium sulfides, and sodium thiosulfate. Based on toxicity characteristic leaching procedure test (TCLP), mercury stabilization efficiency of SPSs was evaluated and proved to be more superior than sulfur, sodium sulfide, and also calcium polysulfide, with an optimal stabilization efficiency of 97.16% at SPS/THg = 1:2, SPSs pH = initial pH, and liquid-to-solid ratio = 20:7. A pseudo-second-order kinetic model was able to interpret the stabilization kinetics and demonstrated that mercury stabilization rate increased with the sulfur index in the SPSs, but excess SPSs were potentially to inhibit the precipitation of mercury. Speciation analysis results determined with sequential extraction indicated that the unstable mercury, elemental mercury, and organic-bound mercury fractions decreased respectively by up to 88.6%, 53.5%, and 26.3%. Pearson correlation analysis showed that the mercury stabilization in the mine tailings amended with SPSs mainly occurs from the precipitation of the elemental mercury, and the organic mercury fraction reduction was correlated with the decrease of the unstable mercury.

Migration mechanism of pollutants in karst groundwater system of tailings impoundment and management control effect analysis: Gold mine tailing impoundment case

Tailing impoundments are sources of high-risk pollution due to the accumulation of mining tailings and wastewater. As a result of thin karst overburden as well as actions of precipitation leaching and scouring, pollutants in the tailing impoundment can easily enter the karst aquifer through sinkholes, corrosion fissures and other channels, causing pollution to groundwater and is not conducive to the utilization of groundwater resources. Through the analysis of hydrogeological conditions, the boundary condition, aquifer structure, source-sink term, and hydraulic characteristics of groundwater are generalized, the groundwater flow model and solute migration model were established, and the migration mechanism of the characteristic pollutant (arsenic ions) was analyzed. The research results show that with the passage of time, the area of high-concentration polluted areas showed a decreasing trend, and the area of low-concentration polluted areas showed a decreasing trend; Under the influence of groundwater flow and the pollutant concentration difference, the pollution plume presents an elliptical shape with the long axis along the direction of water flow; The migration law of pollutants is controlled by the direction of groundwater flow, the concentration difference of pollutants and the permeability of the aqueous medium; The direction of groundwater flow determines the migration direction of pollutants, the concentration difference of pollutants determines the diffusion range of pollutants, and the permeability of aqueous media determines the migration speed of pollutants; Through the prediction of the pollutant control effect, it can be found that a reasonable number of pumping wells that do not interfere with each other are arranged around the groundwater flow channel, which can effectively control the migration of pollutants to the target area. The above research reveals the migration mechanism of pollutants in karst groundwater and main control factors, and also provides a scientific basis for the protection of groundwater resources in karst areas.

Biodegradation of cyanide using a Bacillus subtilis strain isolated from artisanal gold mining tailings

Biodegradation of cyanide using a Bacillus subtilis strain isolated from artisanal gold mining tailings

Biochar mitigates bioavailability and environmental risks of arsenic in gold mining tailings from the eastern Amazon

Artisanal gold mining has generated tailings highly contaminated by arsenic (As) in Cachoeira do Piriá, eastern Amazon, leading to severe risks to the environment. Such risks should be mitigated considering the bioavailable concentration of the element, since it implies immediate damage to the ecosystem. The objective of this study was to evaluate the potential of biochars in mitigating the environmental risks of bioavailable As concentrations in gold mining tailings from underground and cyanidation exploration. The biochar addition increased mineral components, cation retention, phosphorus in all fractions, and organic and inorganic carbon. The bioavailability of As was reduced after adding the biochars, following the order palm kernel cake biochar > Brazil nut shell biochar > açaí seed biochar, with reductions of up to 13 mg kg−1 in the underground mining tailings and 17 mg kg−1 in the cyanidation mining tailings. These results contributed to the statistically significant reduction of the environmental risks in both mining tailings (6–17% in the underground mining tailings and 9–20% in the cyanidation mining tailings), which was emphasized by Pearson's correlation and multivariate analyzes. The incorporation of the bioavailable fractions of As (from sequential extraction) in the environmental risk assessment was a promising method for evaluating the efficiency of biochars in mitigating the damage caused by this metalloid in gold mining tailings.

Synergistic Effects of Biochar and Hydrogel on Growth of Three Herbaceous Species Hydroseeded onto Gold Mine Tailings

Synergistic Effects of Biochar and Hydrogel on Growth of Three Herbaceous Species Hydroseeded onto Gold Mine Tailings