Mine Tailings Site Research Articles

Numerical Simulation of Geophysical Models to Detect Mining Tailings’ Leachates within Tailing Storage Facilities

The effective detection and monitoring of mining tailings’ leachates (MTLs) plays a pivotal role in environmental protection and remediation efforts. Electrical resistivity tomography (ERT) is a non-invasive technique widely employed for mapping subsurface contaminant plumes. However, the efficacy of ERT depends on selecting the optimal electrode array for each specific case. This study addresses this challenge by conducting a comprehensive review of published case studies utilizing ERT to characterize mining tailings. Through numerical simulations, we compare the imaging capabilities of commonly used electrode configurations, six ERT arrays, aiming to identify the optimal array for MTLs’ detection and monitoring. In addition, field surveys employing ERT were conducted at the El Mochito mine tailings site to detect zones saturated with leachates within the tailing storage facilities (TSFs). The findings indicate that the “Wenner-Schlumberger” array exhibits superior data resolution for MTL detection. However, the choice of the optimal electrode array is contingent on factors such as survey location, geological considerations, research objectives, data processing time and cost, and logistical constraints. This study serves as a practical guide for selecting the most effective electrode array in the context of pollutant penetration from mining tailings, employing the ERT technique. Furthermore, it contributes valuable insights into characterizing zones saturated with mining tailing leachates within the TSFs, providing a solid foundation for informed environmental management and remediation strategies.

Mining-related multi-resistance genes in sulfate-reducing bacteria treatment of typical karst nonferrous metal(loid) mine tailings in China.

Management of tailings at metal mine smelter sites can reduce the potential hazards associated with exposure to toxic metal(loid)s and residual organic flotation reagents. In addition, microbes in the tailings harboring multi-resistance genes (e.g., tolerance to multiple antimicrobial agents) can cause high rates of morbidity and global economic problems. The potential co-selection mechanisms of antibiotic resistance genes (ARGs) and metal(loid) resistance genes (MRGs) during tailings sulfate-reducing bacteria (SRB) treatment have been poorly investigated. Samples were collected from a nonferrous metal mine tailing site treated with an established SRB protocol and were analyzed for selected geochemical properties and high throughput sequencing of 16S rRNA gene barcoding. Based on the shotgun metagenomic analysis, the bacterial domain was dominant in nonferrous metal(loid)-rich tailings treated with SRB for 12 months. KEGGs related to ARGs and MRGs were detected. Thiobacillus and Sphingomonas were the main genera carrying the bacA and mexEF resistance operons, along with Sulfuricella which were also found as the main genera carrying MRGs. The SRB treatment may mediate the distribution of numerous resistance genes. KOs based on the metagenomic database indicated that ARGs (mexNW, merD, sul, and bla) and MRGs (czcABCR and copRS genes) were found on the same contig. The SRB strains (Desulfosporosinus and Desulfotomaculum), and the acidophilic strain Acidiphilium significantly contributed to the distribution of sul genes. The functional metabolic pathways related to siderophores metabolism were largely from anaerobic genera of Streptomyces and Microbacterium. The presence of arsenate reductase, metal efflux pump, and Fe transport genes indicated that SRB treatment plays a key role in the metal(loid)s transformation. Overall, our findings show that bio-treatment is an effective tool for managing ARGs/MRGs and metals in tailings that contain numerous metal(loid) contaminants.

Unlocking the potential of microbes: biocementation technology for mine tailings restoration - a comprehensive review.

Mine tailings contain finer particles, crushed rocks, dugout-soil, water, and organic and inorganic metals or metalloids, including heavy metals and radionuclides, which are dumped as waste or non-economic by-products generated during mining and mineral processing. These abundant and untreated materials seriously threaten the environment, human health, and biodiversity because of the presence of heavy metals, radionuclides, and associated primary and secondary toxic components, including the risk of tailings dam failures. Biocementation technology, which involves the use of mining microbes to secrete cement-like materials that bind soil particles together, is a promising approach to restore mine tailing sites and reduce their mobility and toxicity. However, there is a lack of literature on the combined interactions among mining microbes, tailings residues, biocementation, and low-carbon cement (LCC) prospects. This comprehensive review article explores the prospects of mining microbes for mine tailings restoration using biocementation technology, the key influencing factors and their impact, mechanisms and metabolic pathways, and the effectiveness of biocementation technology in restoring mine tailings sites. In addition, it reviews the utilization of mine tailings materials as an alternative source of cement or construction materials for LCC technology. Furthermore, this review highlights the important issues, challenges, limitations, and applications of biocementation technology for mine tailings rehabilitation. Finally, it provides insights for future research and implementation of biocementation for mine tailings restoration and utilization of tailing materials in the industrial sector to reduce carbon emissions/footprints and achieve net-zero goals.

Effects of high‐carbon wood ash biochar on volunteer vegetation establishment and community composition on metal mine tailings

Pyrolyzed organic waste, also known as biochar, is commonly used as a soil amendment and has recently been promoted to remediate metal mine tailings by increasing substrate pH, enhancing water and nutrient retention, and reducing bioavailability of toxic metals. Bottom ash from bioenergy facilities can contain high levels of charcoal residue, and thus qualify as a type of biochar according to international standards; the availability of this material at low costs makes it of particular interest in the context of tailings remediation. Naturally recruiting vegetation is critical in areas of primary succession such as mine tailings, and thus understanding vegetation responses on these substrates is essential. We examined responses of naturally regenerated “volunteer” vegetation to additions of high‐carbon wood ash biochar at a range of application rates (from 0 to 30 metric tons [t]/ha) at two gold mine tailings sites in northern Ontario, Canada over a 2‐year period. Volunteer vegetation cover increased with biochar dosage, peaking at 10–20 t/ha. Wood ash biochar amendments altered substrate physical properties (pH, electrical conductivity [EC], bulk density, total carbon [TC], and nitrogen [TN]), but effects varied by site and with dosage. Substrate TC and EC increased significantly with dosage at both sites with highest measures detected in the 10–20 t/ha amendment range. Species composition showed site‐ and dosage‐specific responses to biochar additions; however, species accumulation curves consistently showed peak species richness at intermediate dosages in both sites and both years of growth. Observed changes in volunteer vegetation suggest that low to moderate dosage applications of high‐carbon wood ash biochar can be highly beneficial for revegetation of mine tailings, but that wood ash impurities can result in deleterious effects at high dosages. Results from these field experiments demonstrate the potential of wood ash in tailings restoration and incentivizes additional in situ experiments to further discern site‐specific mechanisms.

Characterization of diazotrophic root endophytes in Chinese silvergrass (Miscanthus sinensis)

BackgroundPhytoremediation is a potentially cost-effective way to remediate highly contaminated mine tailing sites. However, nutrient limitations, especially the deficiency of nitrogen (N), can hinder the growth of plants and impair the phytoremediation of mine tailings. Nevertheless, pioneer plants can successfully colonize mine tailings and exhibit potential for tailing phytoremediation. Diazotrophs, especially diazotrophic endophytes, can promote the growth of their host plants. This was tested in a mine-tailing habitat by a combination of field sampling, DNA-stable isotope probing (SIP) analysis, and pot experiments.ResultsBacteria belonging to the genera Herbaspirillum, Rhizobium, Devosia, Pseudomonas, Microbacterium, and Delftia are crucial endophytes for Chinese silvergrass (Miscanthus sinensis) grown in the tailing, the model pioneer plant selected in this study. Further, DNA-SIP using 15N2 identified Pseudomonas, Rhizobium, and Exiguobacterium as putative diazotrophic endophytes of M. sinensis. Metagenomic-binning suggested that these bacteria contained essential genes for nitrogen fixation and plant growth promotion. Finally, two diazotrophic endophytes Rhizobium sp. G-14 and Pseudomonas sp. Y-5 were isolated from M. sinensis. Inoculation of another pioneer plant in mine tailings, Bidens pilosa, with diazotrophic endophytes resulted in successful plant colonization, significantly increased nitrogen fixation activity, and promotion of plant growth.ConclusionsThis study indicated that diazotrophic endophytes have the potential to promote the growth of pioneer plant B. pilosa in mine tailings.EAsdjSo3ZCTEVznKh83dpJVideo

Microbial community structure and functions during chronosequence-based phytoremediation programme of Lignite tailing soil

The eco-restoration of mine-tailing sites has a profound impact on native microbial communities and soil physicochemical properties. The adaptive response of microbial communities during the initial years of phyto-remediated mine-tailing sites was poorly understood. Therefore, the microbial changes during the early stages of chronosequence-based phytoremediative technology were studied at Lignite mine-tailing soils of Panandhro, Rann (desert) of Kachchh, Gujarat using amplicon and shotgun metagenomic approaches. The mine-tailing regions were segregated into three zones, based on the year of plantation and a fourth zone (i.e. unmined) was in proximity of the mining area. In a successive restoration programme, seedlings of local plant species were randomly dispersed and planted across the study area. The pH was acidic to circumneutral (3.7–6.7) at raw mine-tailing sites, post-revegetation, it retards the soil degradation by stimulating soil pH to 6.5–7.6 with an increase in the period of plantation (i.e. at the fifth year of study). In mine-tailing sites and during the restoration process, the bacterial community was predominantly composed of phyla Firmicutes (32%–72%), Bacteroidetes (1%–10%) and Proteobacteria (1%–24%), with changes in their relative abundances. The annotation of genes and proteins from sequenced metagenomes of different zones revealed the functions related to energy metabolism, cellular processing and signalling, genes for stress response, virulence and defence, various membrane transporters, genetic information processing, organismal systems and metabolism, etc. These results suggested that revegetation in the mine tailings has initiated the primary microbial succession and thus it can be further expanded to the remaining regions of the tailing areas. • A metagenomic study of Lignite mine tailings and restoration sites was performed. • Chronosequence-based phytoremediation approach was used for site restoration. • The study suggested the increase in TOC and micronutrients at restoration sites. • Firmicutes, Bacteroidetes, Proteobacteria were abundant at tailing and study sties. • The functional potential of indigenous communities was also characterized.

An integrated geochemical and mineralogical investigation on soil-plant system of Pinus halepensis pioneer tree growing on heavy metal polluted mine tailing

ABSTRACT The plant species Pinus halepensis grows spontaneously on heavily polluted mine tailings dumps of Campo Pisano (Sardinia, southwestern Italy). The area is characterized mainly by Zn, Pb, and Cd. Sampling campaign was done, related to soils and plant materials (roots, barks, wood, and needles), aimed at evaluating the main mineralogical characteristics, metal content, plant accumulation, and translocation behavior. The polluted substrates were composed of pyrite, dolomite, calcite, quartz, gypsum, and barite with iron sulphate, and iron oxide. Zn ore minerals (smithsonite) and muscovite detected mostly in the deeper soil layers. Zn was the most abundant metal in the substrate as well as plant tissues. Roots accumulated high metal concentrations (664.65-2710 Zn, 58.39-735.88 Pb, and 4.86-11.02 mg kg−1 Cd) reflecting high metal contamination in soil. The biological accumulation and translocation values were reported below one for all plant tissues. Pb, Zn and Cd Translocation Factor (TF) in needles ranged 0.03-0.32, 0.03-0.19, 0.04-0.14. Biological Concentration Factor (BCF) estimated up to 0.17, 0.18, and 0.19, respectively. Results indicate that P. halepensis is an excluder, tolerates high Zn, Pb, and Cd concentrations, restricts their accumulation and translocation to the aerial parts and may be applied for long-term phytostabilization and revegetation processes in abandoned mine tailing sites.

Metal Lability and Mass Transfer Response to Direct-Planting Phytostabilization of Pyritic Mine Tailings.

Understanding the temporal effects of organic matter input and water influx on metal lability and translocation is critical to evaluate the success of the phytostabilization of metalliferous mine tailings. Trends of metal lability, e.g., V, Cr, Mn, Co, Ni, Cu, Zn, and Pb, were investigated for three years following a direct-planting phytostabilization trial at a Superfund mine tailings site in semi-arid central Arizona, USA. Unamended tailings were characterized by high concentrations (mmol kg-1) of Fe (2100), S (3100), As (41), Zn (39), and Pb (11), where As and Pb greatly exceeded non-residential soil remediation levels established by Arizona. Phytostabilization treatments included a no-compost control, 100 g kg-1 compost with seed, and 200 g kg-1 compost with and without seed to the top 20 cm of the tailings profile. All plots received supplemental irrigation, effectively doubling the mean annual precipitation. Tailings cores up to 90 cm were Collected at the time of planting and every summer for 3 years. The cores were sub-sectioned at 20 cm increments and analyzed via total digestion and an operationally defined sequential extraction for elemental analysis and the calculation of a mass transfer coefficient normalized to Ti as an assigned immobile element. The results indicate that Pb was recalcitrant and relatively immobile in the tailings environment for both the uncomposted control and composted treatments with a maximum variation in the total concentration of 9-14 mmol kg-1 among all samples. Metal lability and translocation above the redox boundary (ca. 30 cm depth) was governed by acid generation, where surficial pH was measured as low as 2.7 ± 0.1 in year three and strongly correlated with the increased lability of Mn, Co, Ni, Cu, and Zn. There was no significant pH effect on the lability of V, Cr, or Pb. Translocation to depths was greatest for Mn and Co; however, Zn, Ni, Cr, and Cu were also mobilized. The addition of organic matter enhanced the mobilization of Cr from the near surface to 40-60 cm depth (pH > 6) over the three-year phytostabilization study compared to the control. The increased enrichment of some metals at 60-90 cm indicates that the long-term monitoring of elemental translocation is necessary to assess the efficacy of phytostabilization to contain subsurface metal contaminants and thereby protect the surrounding community from exposure.

Integrating Historic Mine Hazard Scoring for Comprehensive Assessment of Abandoned Mine Rehabilitation in the Philippines

Abandoned mines remain a social, environmental, and health-risk problem for the Philippines. These abandoned sites are generally characterized by water-filled pit lakes surrounded with disturbed and exposed soils and sediments containing elevated values of heavy metals and other environmental contaminants. Previous studies with abandoned mines in the Philippines have initiated the use of integrated methods for the assessment of existing abandoned mine site conditions as a tool for decision-making. To further provide a numerical basis for rehabilitation prioritization, this paper aimed to utilize the modified Historic Mine Site Scoring System (HMS-SS) for physical and environmental hazard assessment of the abandoned mercury mine located in Barangay Sta. Lourdes, Puerto Princesa City, Philippines and to produce hazard classification maps based on the generated scores. Results identified the pit lake to be extremely hazardous physically, however, the liquid material (rainfall accumulation in the pit) yielded very low environmental hazard scores with only a few identified points that exceed the regulatory limit. Moreover, the two (2) identified mine tailings sites were found to be physically moderately hazardous but are categorized as extremely hazardous for the environmental aspect. The hazard scoring, coupled with the integrated environmental methods for characterization and development of hazard maps, is recommended as a scientific and quantitative basis for providing decisions in priority of actions to be taken with regards to abandoned mine sites.

Native plants facilitate vegetation succession on amended and unamended mine tailings

Facilitating the establishment of native pioneer plant species on mine tailings with inherent metal and/or acid tolerance is important to speed up natural succession at minimal cost, especially in remote areas where phytoremediation can be labor intensive. We investigated vegetation community dynamics after ∼48 years of succession along two legacy Ni–Cu mine tailings and waste rock deposits in the Sudbury Basin, Ontario, Canada with and without various site amendments (i.e. liming and fertilization) and planting. Metal/acid tolerant pioneer plants (Betula papyrifera, Populus tremuloides, Pohlia nutans) appeared to facilitate the establishment of less tolerant species. Conifers and nitrogen-fixers less tolerant to site conditions were planted at the fully amended (limed, fertilized, planted) mine tailings site in the 1970s, but conifers were not propagating at the site or facilitating understory succession. The planted nitrogen-fixing leguminous species Lotus corniculatus was, however, associated with increased diversity. These findings have implications for long-term reclamation strategies in acidic mine waste deposits utilizing native species, as primary colonizing tree species are only recently emerging as candidates for phytoremediation. Novelty statement The potential for native species to act as facilitators for vegetation colonization has rarely been investigated on tailings, despite wide use in remediation of less toxic sites. This study provides a retrospective of over 40 years of plant growth following initial treatment of toxic tailings. We observed that regardless of tailings geochemical conditions, acid/metal tolerant pioneer plants were facilitating ecological succession on acidic Ni-Cu mine tailings sites.

Identification and diversity assessment of cyanobacterial communities from some mine tailing sites in Benguet Province, Philippines using isolation-dependent and isolation-independent methods

Cyanobacteria are a group of diverse prokaryotes that are capable of oxygenic photosynthesis. They are ubiquitous in nature and have been reported to survive in extreme environments. This study aimed to identify and assess the diversity of the cyanobacteria present in some mine tailing sites in the towns of Itogon and Tuba, in Benguet Province, Philippines using isolation-dependent and isolation-independent methods. Analysis of the water and sediment samples from the mine tailing sites (designated as Acu, Ampu, TSF1 and TSF3) showed higher metal concentrations in the sediment samples (2930–11,500 mg/kg dry weight Ca, 10–34 mg/kg dry weight Cr, 83–6500 mg/kg dry weight Cu, 6–172 mg/kg dry weight Pb, 8310–32,600 mg/kg dry weight Mg, 640–3400 mg/kg dry weight K, 43–144 mg/kg dry weight Zn), which were then processed for cyanobacterial enrichment. Identification of cyanobacteria was performed using the conventional isolation-dependent method for the characterization of microorganisms, 16S rRNA gene sequencing, and isolation-independent 16S rRNA metabarcoding analysis. Both approaches revealed that Arthronema africanum (1.98–60.1%) and Leptolyngbya spp. (39.9–97.0%) of the Pseudoanabaenales dominated the cyanobacterial composition in all sites. The isolation-dependent method identified most of the dominant taxa such as Arthronema africanum, Leptolyngbya spp. and Calothrix spp. Nodosilinea spp. was also confirmed to be part of the cyanobacterial community through this method. Unicellular cyanobacteria such as Chroococcales and Synechococcales were also observed. However, they were not fully identified at lower taxonomic levels in both methods, especially Chroococcales. On the other hand, the isolation-independent method recovered other taxa in selected sites such as Calothrix (0.002–0.022%), Halomicronema (0.01%), Nostoc (0.006–0.03%), Phormidium (0.007–14.1%), Planktothrix (0.36%), Pseudoanabaena (0.02–0.6%), Acaryochloris (0.006%), and Thermosynechococcus (0.02–4.7%). Metabarcoding revealed that samples from small-scale mine tailing ponds of Acu and Ampu, and the inactive pond of the large scale mining site, TSF1, had higher species diversity and evenness as compared to its active pond, TSF3, based on Shannon and Simpson indices. However, TSF1 and TSF3 of the large-scale mine tailings had higher species richness than Acu and Ampu of small-scale mining based on Chao index. Altogether, this study provided an inventory of cyanobacteria that can survive even in extreme metal conditions giving insights to their future applications, particularly, in bioremediation.

Interactive assessment of lignite and bamboo-biochar for geochemical speciation, modulation and uptake of Cu and other heavy metals in the copper mine tailing.

This study was designed to examine the combined effect of bamboo-biochar (BC) and water-washed lignite (LGT) at copper mine tailings (CuMT) sites on the concentration of Cu and other metals in pore water (PW), their bioavailability, and change in geochemical speciation. Rapeseed (first cropping-season) and wheat (second cropping-season) were grown for 40-days each and the influence of applied-amendments on both cropping seasons was observed and compared. A significant increase in pH, water holding capacity (WHC), and soil organic carbon (SOC) was observed after the applied amendments in second cropping-seasons. The BC-LGT significantly reduced the concentration of Cu in PW after second cropping seasons; however, the concentration of Pb and Zn were increased with the individual application of biochar and LGT, respectively. BC-LGT and BC-2% significantly reduced the bioavailability of Cu and other HMs in both cropping seasons. The treated-CuMT was subjected to spectroscopic investigation through X-ray photoelectron spectroscopy (XPS), Fourier transform Infrared spectroscopy (FTIR), and X-ray powder diffraction (XRD). The results showed that Cu sorption mainly involved the coordination with hydroxyl and carboxyl functional groups, as well as the co-precipitation or complexation on mineral surfaces, which vary with the applied amendment and bulk amount of Mg, Mn, and Fe released during sorption-process. The co-application of BC-LGT exerted significant effectiveness in immobilizing Cu and other HMs in CuMT. The outcomes of the study indicated that co-application of BC-LGT is an efficacious combination of organic and inorganic materials for Cu adsorption which may provide some new information for the sustainable remediation of copper mine tailing.

Investigation of pollution history in XKS mining area in China using dendrochronology and LA-ICP-MS.

Past pollution episodes and the intensity of mining activity in a contaminated region can be unraveled, using archived elemental information in tree rings. Elemental dendrochronology can be utilized with laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) to make a timeline of metal(loid)s uptake in trees. In this study, six tree core samples from five tree species were collected around the XKS antimony mine region in Hunan, China, which is impacted by metal pollution: NM1 shuitong (Camptotheca acuminate L.), M1 shuitong (Camptotheca acuminate L.), G1 xiangchun (Toona sinensis L.), J2 wutong (Firmiana platanifolia L.), BSN kulian (Melia azedarach L.), and MT1 zhang (Cinnamomum camphora L.). Tree cores were dated by counting annual rings, and concentrations of As, Ca, Pb, Sb, and Zn were determined using LA-ICP-MS. Results demonstrate that the highest concentrations of Sb are present in the areas closer to mining activity: NM1 - north mine (shuitong), MT1 - mine tailing site (zhang), and BSN - between south and north mine (kulian) tree cores have average Sb concentrations of 18.8mg/kg, 13mg/kg, and 4.8mg/kg, respectively. In comparison, at the village sites located farther away from the mining areas, G1 xiangchun, J2 wutong, and M1 shuitong have average Sb concentrations of 0.69mg/kg, 0.57mg/kg, and 0.66mg/kg, respectively. NM1 shuitong, G1 xiangchun, and MT1 zhang all have large Sb and Zn peaks around 1986, while BSN kulian has larger Sb peaks slightly later around 1988-1990. J2 wutong has Sb peaks somewhat earlier, at 1977 and 1980. Unlike the others trees, M1 shuitong has greater Sb concentrations in more recent years (2009, 2015-2016) demonstrating Sb pollution.

Hazardous substances in karst aquifer waters - one of the results of the operational monitoring of groundwater in Serbia

Hydrogeological survey of wider Majdanpek mining area in the Carpathian mountain arch of eastern Serbia, including open mine pits, tailings sites, and major karstic springs and caves has been undertaken in order to estimate environmental conditions in groundwater body (GWB) ?Krs?sever?, groundwater quality, and to investigate causes of their earlier indicated poor chemical status. Bearing in mind that Majdanpek copper mine field is directly bordering the karst aquifer and delineated GWB ?Krs?sever?, the two karst springs namely Valja Fundata and Kaludjerica were in situmeasured and sampled in high and low-water periods (spring 2019, late autumn 2019 and spring 2020). Sampling and analysis of groundwater were carried out under the frame of project ?Operational Monitoring of Groundwater of the Republic of Serbia?, established by the Ministry of Environmental Protection of Serbia. The field measurements of unstable chemical components and physical properties as well as laboratory analyses confirmed very poor and even hazardous water quality of both surveyed springs Valja Fundata and Kaludjerica. Registered concentrations of some ions, such as Fe2+, Mn2+, Ca2+, SO4 2?are high above maximal permitted level for potable water in Serbia. High turbidity rate also confirms impact of colloidal suspensions from the tailing which is located in karstic blind valley. Leakage of mine water passes through joints, open cavities and even large cave system Valja Fundata. Results of undertaken survey confirm that low-water period results with worse water quality and much higher concentration of hazardous substances than that characterized high-water season when infiltrated rainy water and/or melted snow dilute tailing?s wastewater. Strict application of environmental protection measures and de - sign/construction of the smaller water treatment facility at both surveyed springs should possibly mitigate the impacts of mining activities to karst groundwater and dependant ecosystem.

Soil Heavy Metal(loid) Pollution and Phytoremediation Potential of Native Plants on a Former Gold Mine in Ghana

This study investigated the soil pollution level and evaluated the phytoremediation potential of 25 native plant species on a former gold mine-tailing site in Ghana. Plant shoots and associated soil samples were collected from a tailing deposition site and analyzed for total element concentration of As, Hg, Pb, and Cu. Soil metal(loid) content, bioaccumulation factor (BAFshoots), and hyperaccumulator thresholds were also determined to assess the current soil pollution level and phytoextraction potential. The concentration of As and Hg in the soil was above international risk thresholds, while that of Pb and Cu were below those thresholds. None of the investigated plant species reached absolute hyperaccumulator standard concentrations. Bioavailability of sampled metal(loid)s in the soil was generally low due to high pH, organic matter, and clay content. However, for Cu, relatively high bioaccumulation values (BAFshoots > 1) were found for 12 plant species, indicating the potential for selective heavy-metal extraction via phytoremediation by those plants. The high levels of As at the study site constitute an environmental and health risk but there is the potential for phytoextraction of Cu (e.g., Aspilia africana) and reclamation by afforestation using Leucaena leucocephala and Senna siamea.

Phytoremediation of Heavy Metal- Contaminated Tailings Soil by Symbiotic Interaction of Cymbopogon Citratus and Solanum Torvum with Bacillus Cereus T1B3

ABSTRACTEnvironmental pollution by dumping of tailings and overburden from different industrial activities has become a critical issue due to considerable increase in heavy metals (HMs) in all compartments of environment, especially in soils. Phytoremediation shows potential for remediating mine tailing sites contaminated with HMs. The aim of the present study was to isolate, characterize, and assess the native potential HM-resistant bacteria to enhance growth and metal accumulation of Solanum torvum and Cymbopogon citratus. In this study, a pot experiment was conducted to evaluate the effect of native Bacillus cereus T1B3 strain, which can produce plant growth-promoting traits including 1-aminocyclopropane-1-carboxylate deaminase (ACC), Indole Acetic Acid (IAA), Siderophores production, Nitrogen fixation, and Phosphate solubilization on the growth and metal uptake of S. torvum and C. citratus growing in multi-metal-contaminated soil. Inoculating tailings with T1B3 strain significantly increased biomass, photosynthetic pigment content, enzymes and HMs (Cr (VI), Fe, Mn, Cu, Cd, Ni and Zn) accumulation in both plants. Based on translocation and biococentration factors, both plants acted as a potential phytostabilizer of HMs in roots. Results indicate that inoculating of native B. cereus T1B3 strain with S. torvum and C. citratus improves its efficiency for phytoremediation of soil containing mine tailings contaminated with HMs.

Assessing the Long-Term Ecosystem Productivity Benefits and Potential Impacts of Forests Re-Established on a Mine Tailings Site

Restoring sites disturbed by industrial activity to a forested condition can ensure the continued provision of economic and ecosystem services from these areas. Impounded mine tailings are particularly challenging sites, and positive benefits of establishing trees must be balanced against risks associated with metal contamination, ongoing tailings stability, and the possibility of acid mine drainage. We used a hybrid biometric modelling approach based on dendrochronological reconstruction to retrospectively (1980–2015) quantify productivity and carbon dynamics of pine plantations growing on impounded mine tailings at the Vale waste management facility near Sudbury, Canada. Historical reclamation practices had remediated conditions sufficiently to allow conifer plantation establishment in the late 1970s. The revegetated sites were highly productive, when compared to reference conditions based on site index, wood volume growth, and ecosystem production, congruent with other studies showing that forests on revegetated post mining sites can be highly productive. However, metal concentrations in the forest floor were high, and further research is warranted to evaluate ecosystem impacts. Due to the requirement for energy-intensive inputs, we estimated that it took 12 years or more to recover the emissions associated with the revegetation process through C accumulated in biomass and soil at the revegetated sites.

Mapping ground movements caused by mining-induced earthquakes applying satellite radar interferometry

Anthropogenic activity related to the extraction of gas and oil, raw materials or water pumping leads to slow or rapid ground deformation. The ground motion rate is related to the type of the mined material, geological conditions, mining methods and other factors. Ground subsidence resulting from the collapse of underground post-mining voids occurs gradually. Mining-induced earthquakes and seismic earthquakes are largely unpredictable and have an adverse impact on the local inhabitants and buildings. For this reason, monitoring of this phenomenon is a challenge. The application of interferometric SAR for the evaluation of ground movement has brought satisfactory results over the past twenty years mainly in the regions where no other measurements were conducted during ground subsidence. In this paper we have examined a mining-induced earthquake with a magnitude 4.5 which occurred in an underground copper ore mine in Poland on 29th November 2016 and caused eight fatalities. It also had an impact on ground surface deformation in the vicinity of the mine tailings. An assessment of the earthquake-related impact on surface movement was carried out by Sentinel-1 TOPS time series interferometry. The velocity of ground movement and the scale of the phenomenon were investigated. In addition, the impact of the mining-induced earthquake on Zelazny Most mine tailings site was analyzed. Moreover, the process of dynamic ground compaction was also investigated in detail. Ground movement following the mine earthquake was explored. Two time phases of the movements were determined. The first phase of dynamic ground displacement was rapid and 90% of total ground deformation appeared on the surface within 7 days. The second phase of displacement was a ‘vanishing’ one; it lasted for approx. 3 weeks and 10% of ground deformation appeared on the surface. The study revealed that the maximum observed ground subsidence did not exceed 9 cm. The presented results contribute to a better understanding of post-earthquake ground deformations in the light of their spatial distribution in time.

Defunct gold mine tailings are natural reservoir for unique bacterial communities revealed by high-throughput sequencing analysis

Mine tailing dumps are arguably one of the leading sources of environmental degradation with often both public health and ecologically consequences. The present study investigated the concentration of heavy metals in gold mine tailings, and used high throughput sequencing techniques to determine the microbial community diversity of these tailings using 16S rRNA gene based amplicon sequence analysis. The concentration of detected metals and metalloids followed the order Si > Al > Fe > K > Ca > Mg. The 16S rRNA gene based sequence analysis resulted in a total of 273,398 reads across the five samples, represented among 7 major phyla, 41 classes, 77 orders, 142 families and 247 major genera. Phylum Actinobacteria was the most dominant, followed by Proteobacteria, Firmicutes, Chloroflexi, Cyanobacteria, Bacteroidetes, Acidobacteria and Planctomycetes. Redundancy analysis (RDA) and pairwise correlation analysis positively correlated the distribution of Alphaproteobacteria and Gammaproteobacteria to Al and K; Actinobacteria to Cr and Chloroflexi to Si. Negative correlations were observed in the distribution of Bacteroidetes with respect to As concentrations, Actinobacteria to Al, and Alphaproteobacteria and Gammaproteobacteria to high As and Te content of the soils. Predictive functional analysis showed the presence of putative biosynthetic and degradative pathways across the five sample sites. The study concludes that mine tailing sites harbour diverse and unique microbial assemblages with potentially biotechnologically important genes for biosynthesis and biodegradation.

Use of RESRAD-Onsite 7.2 Code to Assess Environmental Risk around Tudor Shaft Mine Tailing Sites

The RESRAD-onsite 7.2 code has been used to assess the total dose rate in Tudor shaft site contaminated over an area of 10 km2. The risk analysis simulation was span over a period of 1.0E+3 years. The maximum total dose of 1.64 mSv/yr was obtain at t = 8.17 ± 0.02 years. The total peak dose at time t = 0 yr. is 1.63 ± 1.0 mSv/yr for all pathways. This value is 6.53 times higher compare to the basic radiation dose limit of 2.5E-01 mSv/yr. The evaluated excess cancer risk was 3.46E-3 and is 10 times higher compared to the recommended limit of WHO. A cover layer depth of 1.25 m was simulated using the code and a total maximum peak dose for all pathways was 2.52E-01 mSv/yr at t = 5.0E+2 ± 1.0 years.