Gold Mine Tailings Research Articles

Recycling Gold Mine Tailings into Eco-Friendly Backfill Material for a Coal Mine Goaf: Performance Insights, Hydration mechanism, and Engineering Applications

Recycling gold mine overflow tailings for coal mine filling is crucial for sustainable mining. In this work, an eco-friendly, performance-controllable overflow tailings-fly ash-based backfill material is developed for coal mine filling. The effects of three critical factors, namely, the slurry concentration (SC), cement-sand ratio (C:S), and tailings-fly ash ratio (T:F), on the workability and uniaxial compressive strength (UCS) properties of the novel backfill material are thoroughly investigated, and an optimization of the corresponding formulation is conducted. The optimal formula for the backfill is determined to be a CS of 60%, a C:S of 0.10, and a T:F of 6:6. The hydration mechanism of the chosen typical mixtures is analyzed via X-ray diffraction (XRD), Scanning electron microscopy (SEM), and Fourier transform infrared (FTIR) spectroscopy, and the results show that a needle-like Aft gel, identified as the major gelatinous product, is intricately intertwined to create an intricate network structure. As the T:F increases, the content of calcium and silicon oxide initially decreases but then increases, and the optimal mixture reaches a minimum value of 63.66%. The optimum specimen exhibits a peak wavenumber at 1,109.46cm-1 involving a Si-O stretching vibration bond. A comprehensive filling program at the Liangjia Coal Mine is successfully implemented. Approximately 0.27 tons of overflow tailings are utilized for every ton of backfills. The underground core-pulling backfill achieves a peak uniaxial compressive strength (UCS) of 7.56MPa after 28 d, surpassing design requirements and showing promise for coal mine filling applications. This study is expected to achieve the transformation of a coal mine goaf into a gold mine tailings pond.

Brevundimonas aurifodinae, sp. nov., an Aerobic Anoxygenic Phototroph Resistant to Metalloid Oxyanions Isolated from Gold Mine Tailings

A polyphasic taxonomic study was carried out on the rod-shaped, orange-pigmented strain C11T, isolated from gold mine tailings. Sequencing of the 16S rRNA gene showed a relatedness to Brevundimonas, with a 98.4% and 98.2% similarity to Brevundimonas bacteroides and Brevundimonas variabilis, respectively. The average nucleotide identity and a digital DNA–DNA hybridization with the closest phylogenetic neighbor of strain C11T indicate distinction at the species level, further confirmed by the differences in physiology. C18:1 ω7c is the dominant cellular fatty acid. Its DNA G + C content is 68.3 mol %. Its predominant ubiquinone is Q-10; 1,2-Di-O-acyl-3-O-α-D-glucopyranuronosyl glycerol, phosphatidylglycerol, 1,2-di-O-acyl-3-O-α-D-glucopyranosyl glycerol, and 1,2-di-O-acyl-3-O-[D-glucopyranosyl-(1→4)-α-D-glucopyranuronosyl] glycerol are its major polar lipid constituents. This bacterium produces bacteriochlorophyll a and tolerates high concentrations of (μg/mL) the following: tellurium (>1500), selenium (1000 to >5000), and vanadium (>5000) oxyanions. The data support the inclusion of the strain C11T into the genus Brevundimonas as a new species with the proposed name Brevundimonas aurifodinae sp. nov. (C11T = NRRL B-61758T; =DSM 118059T).

Development of geopolymer from gold mine tailings utilizing Taguchi robust design

Development of geopolymer from gold mine tailings utilizing Taguchi robust design

Indoor/Outdoor particulate matter (respirable dust) and respirable crystalline silica source tracking in households located proximal to gold mine tailings in Johannesburg, South Africa

Introduction: This study aimed to investigate the concentration of Respirable Crystalline Silica (RCS) and respirable dust, Particulate matters (PM4) concentration in samples measured indoors and outdoors of the nine(9) selected households located proximal to gold mine tailings in Riverlea, Johannesburg. Materials and methods: Sampling locations were separated according to grids, based on distance from the tailings; A (<500 m from the dump), B (>500m<1 km) and C (1 km-3 km). Three households were selected from each grid zone to measure indoor and outdoor PM4 samples continuously over 24 h using GilAir constant sampling pumps. Samples were collected during dry and wet seasons, and respirable crystalline silica in PM4 samples were analysed by an X-ray diffraction method. Results: The mean indoor and outdoor PM4 mass concentrations ranged from 2.02±0.02 µg/m3 to 2.26±0.02 µg/m3, respectively. The dry season mean for PM4 mass concentrations were higher than the wet season PM4 mass concentrations in all zones. The pairwise comparison of PM4 mass concentration for dry and wet seasons revealed no statistically significant difference (p<0.05). The dry season means the indoor/outdoor ratio was greater than one across all zones, suggesting indoor activities as the primary source of PM. In both seasons, the mean indoor and outdoor RCS ranged from 0.02±0.01% to 0.06±0.03%. The mean indoor and outdoor 24 h RCS concentrations in both seasons were below the California Office of Environmental Health Hazard Assessment (OEHHA) defined 24 h ambient exposure threshold of 3 µg/m3. Conclusion: The study found that PM4 concentration was directly proportional to distance from the gold mine tailings. Using RCS as a signature chemical, we found a similar chemical composition in all samples collected in winter and dry season at varied distances. It is concluded that the gold mine tailings are the significant source of PM4 emissions. Therefore, further dust control measures needs to be implemented at the gold mine tailings.

Effective management of endangered Blanding’s Turtle (Emydoidea blandingii) populations in Nova Scotia, Canada, requires consideration of threats posed by legacy gold mine contamination

The Nova Scotia, Canada, Blanding’s turtle (Emydoidea blandingii) population is designated as endangered both federally and provincially. Currently, its range is confined to five disjunct sub-populations in the province’s southwestern interior. With fewer than 500 breeding adults in the wild, current recovery efforts are focused on reducing mortality risk to adult and juvenile turtles. However, little is being done to address the cumulative impacts of environmental contamination on species fitness and reproductive capacity. This paper focuses on legacy impacts of Nova Scotia’s gold mining industry within present-day Blanding’s turtle critical habitat, with a focus on mercury and arsenic contamination. To date, previous studies have not considered the impacts of legacy gold mining contaminants on Blanding’s turtle recovery and conservation. Three historical gold mining areas were identified as overlapping with Blanding’s turtle ranges (West Caledonia District, Brookfield District, and Pleasant River Barrens District). To address the current knowledge gap, site assessments for Blanding’s turtle presence, food web contamination surveys, turtle claw tissue sampling, and overall site remediation are recommended to complement existing recovery efforts. Keywords: Blanding’s turtle, critical habitat, environmental con-tamination, gold mine tailings

The effect of cow manure amendment and the ratio of gold mine tailings on sweet potato gold phytomining

Artisanal and small-scale gold mining has commonly used the mercury amalgamation method for gold ore extraction. The processing waste or tailings often contain gold and other metals. This study examined the effects of cow manure amendment and the ratio of gold mine tailings on sweet potato (Ipomoea batatas L.) gold phytomining. The pot experiment was conducted in the Faculty of Agriculture greenhouse at Padjadjaran University in Indonesia. The sweet potato MZ119 clone (an orange-fleshed sweet potato) was planted on a polybag (40 x 40 cm) consisting of 10 kg of planting media, which was a mixture of gold mine tailing and soil. The design used was a completely randomized design factorial with three replications. The first factor was ratios of gold mine tailing consisting of three levels, namely 30%, 50%, 70%, and 100% (w/w). The second factor was doses of organic manure, namely without cow manure, 250 g pot-1, 500 g pot-1, and 750 g pot-1. The results demonstrated that the application of cow dung and the gold mine tailings ratio (w/w) had a significant (p = 0.05) effect on plants' dry weight biomass, gold accumulation, and gold phytomining by sweet potato. The highest gold mass yield of 0.066 mg gold plant-1 was achieved by a 50% (w/w) gold mine tailing ratio and 750 g pot-1 cow manure treatment.

Synergistic effect of compost and moringa leaf extract biostimulants on the remediation of gold mine tailings using chrysopogon zizanioides

Phytoremediation is a cost-effective and environmentally friendly method for restoring degraded land. However, optimizing phytoremediation conditions and using locally sourced materials can further improve the sustainability of this approach. A 3×2×2 factorial design was used in determining the optimal parameters in the remediation of gold mine tailings using vetiver grass. The treatments consisted of three compost concentrations (0 %, 30 % and 60 %), two biostimulant types (laboratory-extracted and commercial biostimulants) and two application regimens (once and twice a week) in a randomized complete block design. The biomass and metal concentrations in the vetiver grass were measured after 16 weeks. All the vetiver that was planted in 0 % compost amendment died within four weeks regardless the MLE treatment. There was no significant difference in vetiver biomass between vetiver grown in 30 % and that grown in 60 % compost amendment. Biostimulant application frequency led to no significant differences. A difference on vetiver biomass due to the type of moringa leaf extract was eminent, with laboratory moringa leaf extract resulting in significantly higher biomass in vetiver grown on 60 % compost yet the commercial moringa leaf extract producing significantly higher vetiver biomass on vetiver grown on 30 % compost amendment. These findings suggest that the optimal combination for field study would be 30 % compost amendment with commercial biostimulant for a more cost-effective option.

Characterization and Reprocessing of Artisanal and Small-Scale Gold Mine Tailings

Characterization and Reprocessing of Artisanal and Small-Scale Gold Mine Tailings

Heavy Metal Contamination in Rhizosphere of Plants at a Decommissioned Gold Mine Tailings Dam

Heavy Metal Contamination in Rhizosphere of Plants at a Decommissioned Gold Mine Tailings Dam

Biodegradation of polypropylene microplastics by Bacillus pasteurii isolated from a gold mine tailing

Microplastics (MPs) are present throughout the environment, and due to their nature, they are extremely difficult to decompose. Reportedly, microorganisms play an important role in degrading and decomposing MPs. Bacillus pasteurii can degrade various complex organic matter, including MPs, which are a class of polymeric organic compounds. This study investigated the degradation effect of B. pasteurii on polypropylene MPs (PP-MPs) in soil. B. pasteurii was extracted from gold mine tailings. Herein, three experimental groups were established—a blank control treatment group, a group with bacteria without Ca2+ added (T2 group), and a group with bacteria supplemented with Ca2+ (T3 group)—for a 30-day indoor simulation of MP degradation in MP-treated soil. The results showed that the total mass change rate of the PP-MPs in the T2 group was 20.95 %, and grooves and holes appeared on the PP-MP surfaces. The total mass change rate of the PP-MPs in the T3 group was 23.22 %, and abundant fissures and pits appeared on the PP-MP surfaces. Additionally, new dominant phyla, such as Bacteroidetes and Firmicutes, appeared after bacterial addition. The relative abundance of several common soil genera, such as Bacillus, Brevundimonas, Flavobacterium, and Arthrobacter, and genera capable of breaking down complex compounds increased after B. pasteurii addition. The soil microbial community diversity improved, with the distribution of each species being relatively uniform. These findings indicated that the B. pasteurii strain can be used to degrade PP-MPs. Additionally, the addition of Ca2+ generated microbially induced calcium carbonate precipitation, which further improved the degradation of MPs. This study provides theoretical support for studying the degradation mechanism of PP-MPs.

Unintended Consequences of Urban Expansion and Gold Mining: Elevated Indoor Radon Levels in Gauteng Communities’ Neighboring Gold Mine Tailings

The province of Gauteng in South Africa has a rich history of gold mining, which has driven economic growth and urbanization. Gold mining has also created over 270 gold mine tailings (GMT), now surrounded by human settlements due to a housing shortage. These GMT pose a health risk as they harbor elevated uranium, which over time undergoes radioactive decay to produce radon, a known lung carcinogen. This study aimed to investigate the potential correlation between the proximity to gold mine tailings (GMT) and indoor radon concentrations in Gauteng’s residential dwellings. Volume activity of radon (VAR) inside 330 residential dwellings was measured in residential dwellings located proximally (<2 km) and distally (>2 km) to gold mine tailings using AlphaE radon monitors during winter. An interviewer-administered questionnaire was utilized to obtain data on factors that may influence indoor radon activities. Descriptive statistics and bivariate logistic regression analyzed the influence of proximity to gold mine tailings and dwelling characteristics on VAR. Furthermore, VAR was compared to the World Health Organization (WHO) radon reference level of 100 Bq/m3. Residential dwellings near gold mine tailings had significantly higher average indoor radon concentrations (103.30 Bq/m3) compared to the control group (65.19 Bq/m3). Residential dwellings proximal to gold mine tailings were three times more likely to have VAR beyond the WHO reference level of 100 Bq/m3. Furthermore, they had estimated annual effective doses of 2.60 mSv/y compared to 1.64 mSv/y for the control group. This study highlighted a concerning association between proximity to gold mine tailings and elevated indoor radon levels. Public health interventions prioritizing residential dwellings near gold mine tailings are crucial. Educational campaigns and financial assistance for radon mitigation systems in high-risk dwellings are recommended. Residents near gold mine tailings are encouraged to ensure continuous natural ventilation through frequent opening of windows and doors.

Investigating the Partition of Metalloid Pollutants in Gold Mine Tailings by STEM-EELS Spectrum Image

Investigating the Partition of Metalloid Pollutants in Gold Mine Tailings by STEM-EELS Spectrum Image

Açaí Seed Biochar-Based Phosphate Fertilizers for Improving Soil Fertility and Mitigating Arsenic-Related Impacts from Gold Mining Tailings: Synthesis, Characterization, and Lettuce Growth Assessment

Biochar represents a promising alternative for enhancing substrates and remediating contaminants in mining areas. Given that arsenic (As) and phosphorus (P) share similar chemical forms, the combination of biochar and P fertilizers may reduce As uptake, thereby mitigating As-related impacts. This study aimed to evaluate the potential of biochar-based P fertilizers in improving soil fertility and mitigating human health risks from gold mining tailings in the eastern Brazilian Amazon. Biochar from açaí palm (Euterpe oleracea Mart.) seeds was produced through enrichment with single and triple superphosphate at a ratio of 1:4, at 400 °C, and applied to mining tailings at 0.5%, 1%, and 2%. After one year of incubation, lettuce plants were grown for 70 days. Biochar reduced As absorption by lettuce and improved biomass and nutrient accumulation, resulting in improved vegetation indices. Biochar was effective in reducing non-carcinogenic As risks via ingestion of soil and plants to acceptable levels. Regression equations explained the As absorption behavior as affected by the biochar and the importance of biochar-related nutrients in reducing As stress. This study demonstrates the potential of P-enriched biochar as an amendment for As-contaminated soils, reducing As absorption, increasing P availability, and improving plant growth.

Evaluation of potentially toxic metals in tailings from Busia gold mine fields of eastern Uganda

Busia Gold mines in eastern Uganda generate significant wastes that contribute to environmental and health challenges in the region. This study assessed the extent of 9 potentially toxic metals (PTMs) present in Busia gold mine tailings. The study also evaluated environmental risks for each of the PTMs, using contamination indices. The indices were: index of geo accumulation (Igeo); potential ecological risk index (RI); contamination factor (CF); pollution load index (PLI) and ecological risk factor (ERI). Tailing samples were collected at two distinct depths; surface (0–30 cm) and deep (30–60 cm) from four sites. The samples were analyzed using an Atomic Absorption Spectrometry (AAS). The Igeo results showed that As and Hg recorded extreme pollution levels (Igeo >5) in all 4 sites. The other seven PTMs in all the sites were classified between heavily polluted to unpolluted categories. CF results revealed extreme contamination for Hg at site-A and As at site-M with moderate contamination of Ni, Zn, and Co at sites-C and B. RI findings showed that all the sites recorded RI > 600, with the highest (RI = 80, 407) at site-A, followed by site-C (RI = 74, 536). All the sites had a high level of ecological impact with greater potential for environmental risks in the area. In the case of PLI, all the sites were classified as polluted sites (PLI > 1). Sites-M and C recorded the highest (PLI = 12), followed by sites-B and A, with PLIs of 11 and 9, respectively. ERI findings for all the sites showed significant Hg, As, and Cd contamination, (ERI >320). Site-A recorded the highest Hg contamination (ERI = 78, 825). Site-M recorded elevated levels of As and Cd, with ERI of 1, 323, and 399, respectively. Pb at site-M posed considerable potential ecological risk with an ERI of 108, while Zn, Cu, Co, Ni, and Cr presented low ecological risk across all sites with ERI˂ 40. There is, therefore, need to properly manage tailings in Busia gold fields to minimize ecological contamination to avoid impacts on human, animal, and plant health.

Exploring the Coagulant Capability of Moringa oleifera seed powder at reducing Turbidity in Gold Mine Tailings Slurry

Moringa oleifera is characterised as an effective alternative to traditional approaches for the treatment of gold mine tailings spoils, particularly for its low cost, non-toxic nature, and simple application. This study investigated the use of M. oleifera seed powder as a primary coagulant for the treatment of gold mine tailings with respect to turbidity reduction, and the effect of varying pH on the coagulation process. The tailings sample used in the study was collected from an active mining operation in the Waiamu area, Cuyuni Mining District 4, Guyana; with the average turbidity ranging between 216.33 ± 4.62 and 275.33 ± 8.33 NTU. The standard jar test procedure was used to assess the efficiency of the M. oleifera coagulant based on measurements of turbidity reduction. M. oleifera was found to be an effective coagulant for reducing turbidity in the selected gold mine tailing pond, with the best turbidity reduction being 91.31 ± 0.53%. Further evidence from the study suggested that at the optimum coagulant concentration of 250mg/L, turbidity reduction changed as pH levels (5, 6, 7, 8, 9) were altered, whereby reduction at the natural pH level of 7 (control) was 91.31 ± 0.53%; and following adjustments of pH levels to 5, 6, 8 and 9, turbidity was reduced by 85.00 ± 0.58%, 84.88 ± 0.94%, 77.81 ± 5.21% and 74.16 ± 5.28% respectively. Therefore, strong knowledge of biological approaches for the treatment of gold mine tailings spoils would be pivotal to support long-term decisions on wastes management and disposal.

Investigation of glycine leaching for gold extraction from Witwatersrand gold mine tailings with permanganate pre-treatment

The Southern African region contains abundant gold tailing heaps that are an environmental concern due to dust pollution and chemical contamination of nearby water bodies. Nevertheless, these heaps contain gold with potential to be extracted for financial gain. In this study, the feasibility of extraction of gold from a Witwatersrand gold tailings using glycine was investigated using a two-level full factorial design. Effects of variables such as glycine concentration at levels of 0.5-1.5 M with a solid-liquid ratio of 50-200 g/L were investigated. Although the solid-liquid ratio used in this study was below the industrial norm, it provides a starting point for investigating the applicability of this technology. To enhance the gold extraction, potassium permanganate pretreatment and copper ion addition were adopted. The results revealed that 91.4% gold extraction was achieved after 24 h pre-treatment of the tailings using 2 g/L potassium permanganate followed by subsequent leaching using 1.5 M glycine at pH 12, with 50 g/L solid-liquid ratio and 2 g/L copper ions. Statistically, the solid-liquid ratio and potassium permanganate pre-treatment of the tailings were found to be significant at 95% confidence interval, whilst interactions of copper ions and glycine concentration were significant factors. The work demonstrates that potassium permanganate pre-treatment prior to glycine leaching of low-grade secondary gold resources, such as tailings, can be beneficial. Furthermore, the methodology developed in this work provides an opportunity for further investigation of the recovery of gold hosted in complex mineralogical matrices.

The Effect of Azotobacter on Growth and Yield of Water Spinach in Growing Media Containing Gold Mine Tailings

Gold mining provides economic benefits but results in the conversion of agricultural land and produces low-fertility tailings. Efforts to remediate tailings can be done through the utilization of the biofertilizer bacteria Azotobacter sp., which is capable of producing exopolysaccharides. This study aims to study the effects of biofertilizers containing a consortium of Azotobacter sp. strains S5, S6a, and S9 in enhancing the growth and yield of water spinach plants in growth media containing gold mine tailings. The experiment used a randomized complete block design with four treatments and six replications. The treatments consisted of; (A) control, (B) 1% biofertilizer, (C) 5% biofertilizer, and (D) 10% biofertilizer. The results of the experiment showed that the dosage of 5% biofertilizers increased plant height, leaf count, and fresh weight of plants, while the 10% biofertilizer increased the stem diameter. The findings of this experiment emphasize the importance of biofertilizers in enhancing the growth and yield of water spinach plants in media with low fertility.

Adapted Sequential Extraction Protocol to Study Mercury Speciation in Gold Mining Tailings: Implications for Environmental Contamination in the Amazon.

Artisanal small-scale gold mining (ASGM), an increasingly prevalent activity in South America, generates mercury-contaminated tailings that are often disposed of in the environment, leading to the introduction of mercury into ecosystems and the food web, where it bioaccumulates. Therefore, studying the geochemical processes involved in the desorption and dissolution of mercury in these tailings is essential for critical risk evaluations in the short and long term. For this purpose, sequential extraction procedures (SEPs) can be useful because they help to identify the phases to which Hg is associated, although they also have limitations such as a lack of selectivity and specificity. In this work, we propose a modified four-step SEP: exchangeable mercury (F1), oxidizable mercury (F2), mercury bound to Fe oxides (F3), and strongly bound mercury (F4). To test this adapted sequential extraction method, we evaluated the Hg contamination in mercury-contaminated tailings of the Amazon basin. The results revealed a total mercury concentration of 103 ± 16 mg·kg-1 in the tailings, with a significant portion in F1 (28% of the total), where Hg was bioavailable. The large Hg concentration in F3 (36%) suggested that Fe oxides likely contribute to mercury retention. Together, the SEP results emphasize the urgent need for improved surveillance of gold mining activities and responsible tailings management practices to mitigate environmental contamination and safeguard the health of the Amazon ecosystem.

Determination of Activity Concentration and Radiological Risks from Gold Mine Tailings around Ilahun-Ijesa in Obokun Local Government, Osun State, Nigeria

In this study, the activity concentrations and radiological risks associated with exposure to NORMS in soils around the gold mine tailings in Ilahun – Ijesa, Obokun Local Government, Osun State, Nigeria was evaluated. A Sodium Iodide (NaI) gamma spectroscopy was used to determine the activity concentrations of the natural radio nuclides in soil samples that were collected from the gold mine tailings. The mean activity concentration for 238 U, 232 Th and 40K were 14.50±2.40, 10.45±3.20 and 332.70±6.10 Bqkg-1 respectively. The average absorbed dose was calculated to be 26.4 nGy/h and the corresponding average annual effective dose was found to be 0.0031 mSv, which is less than the total annual effective dose of 1 mSv recommended by ICRP for public exposure control. Radiological hazard parameters were evaluated from activity concentrations and the average values were found to be lower than recommended safety limits.

Elemental composition and potential health risk of vegetable cultivated in residential area situated close to abandoned gold mine dump: Characteristics of soil quality on the vegetables

The presence of toxic metals in residential areas near abandoned gold mine tailings is a major environmental issue. This study mainly aimed to investigate the elemental distribution of both toxic and essential elements in soils and leafy vegetables (Brassica oleracea) collected from eight different sites around the Davidsonville residential area, located closer to the abandoned Princess gold mine dump, Johannesburg, South Africa. The nutritional value of vegetables in the human diet was determined to assess their value to their health. The vegetables contained metals in the following descending order: Ca > Mg > Ca > Sb > Pb > Fe > Mo > Cr > Se > As > V > Ni > Co > Cd. The bioaccumulation factor (BAF) revealed that vegetables tend to accumulate most metals even (toxic) during the transfer and translocation process. Based on the recommended daily allowance (%RDA) the vegetables showed to contribute 152%, 84% and 75% toward RDA for Se, V and Ca, respectively for most adults and these play a role in human metabolic activities. The vegetables were found to be a good source of essential elements (Ca, Mg, Ni, Na, Fe) but with some traces of toxic metals such as Pb, As and Sb. Based on the health risk assessment, the vegetable posed an adverse health hazard for human consumption due to metals with high HRI >1.