Tailings Surface Research Articles

Обоснование технологического решения по экологической реабилитации техногенных образований

В статье изложены результаты многолетних исследований по обоснованию технологических решений, направленных на реабилитацию техногенных образований, загрязненных соединениями тяжелых металлов и мышьяка, с использованием потенциала биологических систем. На основе разработанных биогенных принципов и воспроизводства продуктивности нарушенных горными работами земель предложено технологическое решение с использованием потенциала биологических систем (фототрофных бактерий) по снижению их негативного воздействия на экосферу для перевода после рекультивации в земли лесного фонда. Abstract. In the Far Eastern Federal District (FEFD) of Russia, as a result of the restructuring of the economy, many mining facilities in the past century were bankrupt. Large volumes of toxic waste were uncontrolled. Hydrotechnical services were eliminated and the tailings were drained. Their preservation and recultivation was not carried out. As a result, the plume of products from the dusting surface of drained tailings constantly covers landscapes and settlements, especially in the spring-summer-autumn season. A significant part of the territory of the mining enterprise has a crisis ecological situation, which has led to the emergence of environmentally-related diseases of the local population. The purpose of the research was to substantiate the technological solution for the rehabilitation of technogenic formations contaminated with heavy metal and arsenic compounds, using the potential of biological systems, to reduce their negative impact on the ecosphere. They are considered by us as environmental damage to the past economic activities of the mining enterprise. To assess the risk of waste impact on the ecosphere, the following methods and techniques are used: geobotanical, silvicultural, geomorphological, modern instrumental and traditional physicochemical, chemical methods and cartographic modeling, statistical data processing, as well as scientific forecasting and systematization. Expeditionary field studies within the boundaries of the influence of the mining enterprise, conducted during 2008-2017, were carried out according to a single methodology. The samples were prepared for the analysis in the same way and were analyzed at the Khabarovsk Innovation and Analytical Center ITIG FEB RAS on a modern ICP device. The processes of soil formation and natural overgrowing in technogenic landscapes by generally accepted methods have been studied. The chemical analysis was carried out according to the methods described in the «Guidelines for the Control of Atmospheric Pollution RD.52.04.286-89». On the basis of the conducted research, conclusions were drawn about the insufficient knowledge of the problem of recultivation of the surface of tailings within the influence of «Dalnegorsky GOK» containing toxic waste. The formulated bioengineering principles for creating a safe technology for the ecological rehabilitation of technogenic formations will significantly reduce the anthropogenic impact on the environment to an acceptable level of inevitable impact generated by the fact of artificial withdrawal of part of the lithosphere for mining purposes. The efficiency of using phototrophic bacteria for solving the problem of eliminating accumulated environmental damage is shown. In the future, it is planned to continue research in this area for the transfer of land to the forest fund of the Dalnegorsk district forest area after reclamation work using the potential of biological systems.

Surficial geochemistry and bioaccessibility of tellurium in semiarid mine tailings

Environmental contextTellurium can be more toxic than arsenic, but its fate in the surficial environment is poorly understood. We studied tellurium behaviour in semiarid mine tailings and found that most tellurium is associated with iron (oxy)hydroxides as tellurate (TeVI), the less toxic oxidation state. Iron (oxy)hydroxides are likely to control the fate of Te in the surficial environment and may effectively sequester Te oxyanions released by oxidative weathering. AbstractTellurium (Te) is a critical element owing to its use in solar technology. However, some forms are highly toxic. Few studies have examined Te behaviour in the surficial environment, thus little is known about its potential human and environmental health impacts. This study characterises two physicochemically distinct Te-enriched mine tailings piles (big and flat tailings) deposited by historic gold (Au) mining in the semiarid Delamar mining district, Nevada, USA. The big tailings are characterised by smaller particle size and higher concentrations of potentially toxic elements (up to 290mgTekg−1), which are enriched at the tailings surface. In contrast, the flat tailings have larger particle size and properties that are relatively invariant with depth. Based on the sulfate to sulfide ratio, the tailings were determined to be sulfate dominated, which suggested a high degree of weathering, although the flat tailings did contain significant amounts of sulfides (~40%). Tellurium X-ray absorption spectroscopy of the big tailings indicates that tellurate, the less toxic Te species, is the principal form of Te. Electron microscopy indicates that most of the Te present at the site is associated with iron (oxy)hydroxides, and sometimes with other potentially toxic elements, especially lead and antimony. Physiologically-based extraction tests indicate that substantially more Te is solubilised in synthetic stomach fluids than in lung fluids, with gastric bioaccessibility ranging from 13 to 31% of total Te. This points to low to medium bioaccessibility, which is common for iron (oxy)hydroxide-associated elements. Together, these results represent a preliminary assessment of Te surficial behaviour in a semiarid environment and indicate that Te in these tailings represent a moderate health concern.

ASSESSMENT OF POTENTIAL RADIATION HAZARD OF THE FORMER URANIUM FACILITIES FOR THE POPULATION OF THE ISTIKLOL CITY OF THE REPUBLIC OF TADZHIKISTAN

The article presents the results of alpha, gamma spectrometric analyzes of samples, dosimetry, radon monitoring of the estimated areas in the Istiklol city. It has been established that the specific activity of radionuclides for uranium and radium in the tailing materials are in the range: 1405 – 2140, 5935 – 9843 Bq / kg, respectively. Based on the results of the monitoring of gamma radiation and radon volume activity at Istiklol city sites, it has been established that gamma radiation ambient equivalent dose rate varies from 0.52 to 1.78 μSv / h, and radon volume activity in air ranges from 20 and 45 Bq / m3. It is shown that the radon concentration in the air above the surface of tailings is not high. However, the exhalation of radon from the soil surface of all the tailings dumps examined is above the standard (1 Bq / (m2·s). The results of measurements of radon volume activity in the air of residential buildings and facilities located on the territory of Istiklol city have shown that the value of radon volume activity is within the limits of 44 – 195 Bq / m3. A high value of radon volume activity is noted in the former dilapidated plant (1319 Bq / m3). Gamma and alpha spectrometric studies revealed that the average values of the activity concentration of uranium and radium in the soils for tailings and the pit are for 234U – 65365 Bq / kg, for 238U – 50295 Bq / kg, and for 226Ra – 3800 Bq / kg. To estimate the doses of population irradiation via the water pathway were taken the average values of the volumetric activity of 234U, 238U, 226Ra in the waters. Maximum values of volumetric activity of radionuclides were observed in samples of drainage water, Bq / m3: 234U – 530000, 238U – 390000, 226Ra – 185. To calculate the contributions of various radiation factors to an additional annual dose of irradiation, the population was divided into four hypothetical groups. The time duration of stay of various hypothetical population groups in the areas of potential irradiation, radiation dose due to water use from contaminated water sources and additional factors in Istiklol were taken into account.The main contributor to the additional radiation dose received by hypothetical population groups is external irradiation during the stay on the territory of the FBR and tailing dumps, and internal irradiation due to the use of contaminated water.

Geothermal study to explain man-made permafrost in tailings with raised surface

Deposition of mine tailings in a cold climate requires precautions as temporary sub-zero temperatures can imply considerable consequences to the storage due to creation of permafrost. The risk of creating man-made permafrost lenses due to tailings deposition exists even in regions with no natural permafrost, as material being frozen during winter might not fully thaw by the following summer. When such frozen layers thaw during later longer warmer periods, excess pore water pressure and large settlements might develop. Such implications close to the dam structure have to be avoided and therefore the risk of generating permafrost should be reduced. This paper describes a geothermal model for one-dimensional heat conduction analysis. The model is able to simulate the temperature profile in tailings where the surface elevation is constantly increased due to deposition. At the tailings surface, the boundary condition is the air temperature changing over time during the year. Air temperatures, tailings deposition schedule and tailings properties are given as input to the model and can easily be changed and applied to specific facilities. The model can be used for tailings facilities in cold regions, where the effects of tailings deposition on the temperature regime are of interest. Findings can improve tailings management by explaining man-made permafrost generation. The model can also aid in setting up appropriate deposition schedules and to prevent generation of permafrost layers.

Assessment of emissions of trace elements and sulfur gases from sulfide tailings

This article presents the results of field and laboratory experiments performed to determine the compositions of gases in the air above the Komsomolsk sulfide tailings. Concentrations of SO2 were measured using a GANK-4 portable gas analyzer. The possibility of the gaseous transport of trace elements was estimated by pumping air through a bubbler with an absorber. Qualitative analyses of sulfur gases (CS2, C2H6S2, C2H6S3, S8, S7, and S6) were performed using a field chromatography-mass spectrometer. The SO2 concentrations in the air above the surface of the Komsomolsk tailings can reach up to 2.5mg/m3 and vary significantly during the day, depending on the difference between the temperature of the tailings surface and that of the ambient air. A wide range of chemical elements (i.e., rock-forming elements, metals, and anionic elements) can migrate with the gaseous phase from both sulfide tailings and background sites. Correlation analysis indicates that the main source of trace elements in gas streams from tailings material is unstable crystalline hydrates, which are represented by sulfates and sulfarsenates of Al, Fe, Mg, Zn, and Cu. The emissions of alkaline and alkaline earth elements are mainly caused by the compositions of pore solutions. Volatile sulfur compounds, including sulfur dioxide, carbon disulfide, dimethyl disulfide, and dimethyl trisulfide, as well as elemental sulfur, are the products of microbiological activity. The results obtained here indicate that the gas phase above the surface of the sulfide tailings has a complex composition and that many chemical elements may be transferred by gases under low-temperature conditions.

UAV Remote Sensing Surveillance of a Mine Tailings Impoundment in Sub-Arctic Conditions

Mining typically involves extensive areas where environmental monitoring is spatially sporadic. New remote sensing techniques and platforms such as Structure from Motion (SfM) and unmanned aerial vehicles (UAVs) may offer one solution for more comprehensive and spatially continuous measurements. We conducted UAV campaigns in three consecutive summers (2015–2017) at a sub-Arctic mining site where production was temporarily suspended. The aim was to monitor a 0.5 km2 tailings impoundment and measure potential subsidence of tailings. SfM photogrammetry was used to produce yearly topographical models of the tailings surface, which allowed the amount of surface displacement between years to be tracked. Ground checkpoints surveyed in stable areas of the impoundment were utilized in assessing the vertical accuracy of the models. Observed surface displacements were linked to a combination of erosion, tailings settlement, and possible compaction of the peat layer underlying the tailings. The accuracy obtained indicated that UAV-assisted monitoring of tailings impoundments is sufficiently accurate for supporting impoundment management operations and for tracking surface displacements in the decimeter range.

Thermal Remote Sensing For Moisture Content Monitoring of Mine Tailings: Laboratory Study

Abstract Mining produces massive volumes of mine tailings that are deposited into large-scale mine tailings impoundments. A key environmental objective of managing these large impoundments is mitigating fugitive dust emissions by monitoring and controlling moisture, because moisture directly affects the tailings’ strength and the ability to apply dust control measures using motorized equipment. Therefore, understanding the spatial and temporal variations in moisture content for surface tailings is critical for characterizing dust susceptibility and trafficability. Remote sensing has been proven to be a useful tool for similar applications. This study utilized laboratory testing conducted on iron mine tailings to verify that: (1) a relationship exists between moisture content and strength for the surface of mine tailings, and (2) thermal remote sensing can be used to infer spatial variations in moisture content for surface tailings. Multivariate regressions were developed to identify the critical remote sensing and climatic variables and evaluate their influence in remotely measured moisture content. For tailings samples collected from two different North American iron mines, regressions using sample temperature and ambient humidity were able to predict surface moisture content (R2> 0.9).

Analysis of the effects of natural organic matter in zinc beneficiation

In this study, we present the analysis of the effects of Natural Organic Matter (NOM) in zinc beneficiation from abandoned mine tailings using bioleaching technologies. We used standardized Suwannee River Humic Acid (SRHA) as the NOM source to analyze the importance of the quality of the process waters and the possible side effects of NOM accumulated on mine tailings when exposed to environmental conditions. Our study proposes the use of process waters as an important variable to maintain high process efficiency. Concentrations of 20 ppm of SRHA suspended in the bioleaching medium reduced the Zn removal efficiency by 10% as compared with the process without SRHA. Similarly, at concentrations of 50 ppm of SRHA, the Zn removal efficiency decreased by 20% as compared with the process without SRHA. However, our study refutes the view that the accumulation of NOM on mine tailings could possibly reduce the process efficiency. We conclude that the suspended NOM was able to alter the process efficiency by reducing the bacterial attachment on the mine tailing's surface, which suggested the importance of the bacterial contact mechanism.

Geochemical characteristics of rehabilitated tailings and associated seepages at Kidston gold mine, Queensland, Australia

This study investigated an uncapped tailings storage facility in a semi-arid subtropical climate, with the aim of understanding the hydro-geochemical processes controlling the seepage water quality and the dispersion/attenuation of metals and metalloids within the tailings and through a constructed wetland. While direct re-vegetation helped to stabilize the surface of tailings, development of an oxidation front in the tailings resulted in high sulphate and arsenic concentrations in the seepage. The findings of this study will assist maximizing the efficiency of any future passive treatment system on site and provide useful information for similar tailings closure strategies elsewhere.

Atmospheric dust deposition on soils around an abandoned fluorite mine (Hammam Zriba, NE Tunisia)

The present study focuses on the eolian dispersion and dust deposition, of major and trace elements in soils in a semi-arid climate, around an old fluorite (CaF2) and barite (BaSO4) mine, located in Hammam Zriba in Northern Tunisia. Ore deposits from this site contain a high amount of metal sulphides constituting heavy metal pollution in the surrounding environment.Samples of waste from the surface of mine tailings and agricultural topsoil samples in the vicinity of the mine were collected. The soil samples and a control sample from unpolluted area, were taken in the direction of prevailing northwest and west winds. Chemical analysis of these solids was performed using both X-ray fluorescence and X-ray diffraction. To determine the transfer from mine wastes to the soils, soluble fraction was performed by inductively coupled plasma and ionic chromatography.The fine grained size fraction of the un-restored tailings, still contained significant levels of barium, strontium, sulphur, fluorine, zinc and lead with mean percentages (wt%) of 30 (calculated as BaO), 13 (as SrO), 10 (as SO3), 4 (F), 2 (Zn) and 1.2 (Pb). Also, high concentrations of cadmium (Cd), arsenic (As) and mercury (Hg) were found with an averages of 36, 24 and 1.2mgkg−1, respectively. As a result of the eolian erosion of the tailings and their subsequent wind transport, the concentrations of Ba, Sr, S, F, Zn and Pb were extremely high in the soils near to the tailings dumps, with 5%, 4%, 7%, 1%, 0.8% and 0.2%, respectively. Concentration of major pollutants decreases with distance, but they were high even in the farthest samples. Same spatial distribution was observed for Cd, As and Hg. While, the other elements follow different spatial patterns.The leaching test revealed that most elements in the mining wastes, except for the anions, had a low solubility despite their high bulk concentrations. According the 2003/33/CE Decision Threshold, some of these tailings samples were considered as hazardous. Furthermore, other waste samples, considered non hazardous, were not inert. In contrast, the SO42-, Ba, Pb and Sb leachable contents measured in most of the soil samples were relatively high, exceeding the inert threshold for landfill disposal of wastes.

Prediction of water content and normalized evaporation from oil sands soft tailings surface using hyperspectral observations

The paper addresses the challenge of measuring water content and evaporative fluxes from oil sands soft tailings surfaces using hyperspectral observations. Hyperspectral time-series laboratory observations were collected from four different mature fine tailings (MFT) samples displaying variations in swelling potential and bitumen concentration. The samples were allowed to evaporate from an initial state of water saturation to an air-dried state. From these data, several spectral features were evaluated to predict water content and normalized evaporation rate from the optically sensed portion of the tailings surface (less than a few hundred micrometres). For the samples tested, the best estimate of moisture content was achieved using the normalized soil moisture index (NSMI) index (coefficient of determination R2 = 0.97). The absolute reflectance at 1920 nm was found to be the best spectral estimator of normalized evaporation (R2 = 0.97), with the NSMI index also being valuable (R2 = 0.95). In both instances, the NSMI index may be of value for estimations attempted in the field. Remote estimation of moisture content and evaporation could help tailings managers assess the drying process to determine when the deposit has stopped drying at the surface and decide when the next lift should be deposited. In future efforts, the models obtained from this laboratory investigation will be assessed for their applicability in field settings and validated using concurrent sampling.

Next-Generation Sequencing Assessment of Eukaryotic Diversity in Oil Sands Tailings Ponds Sediments and SurfaceWater.

Tailings ponds in the Athabasca oil sands (Canada) contain fluid wastes, generated by the extraction of bitumen from oil sands ores. Although the autochthonous prokaryotic communities have been relatively well characterized, almost nothing is known about microbial eukaryotes living in the anoxic soft sediments of tailings ponds or in the thin oxic layer of water that covers them. We carried out the first next-generation sequencing study of microbial eukaryotic diversity in oil sands tailings ponds. In metagenomes prepared from tailings sediment and surface water, we detected very low numbers of sequences encoding eukaryotic small subunit ribosomal RNA representing seven major taxonomic groups of protists. We also produced and analysed three amplicon-based 18S rRNA libraries prepared from sediment samples. These revealed a more diverse set of taxa, 169 different OTUs encompassing up to eleven higher order groups of eukaryotes, according to detailed classification using homology searching and phylogenetic methods. The 10 most abundant OTUs accounted for >90% of the total of reads, vs. large numbers of rare OTUs (<1% abundance). Despite the anoxic and hydrocarbon-enriched nature of the environment, the tailings ponds harbour complex communities of microbial eukaryotes indicating that these organisms should be taken into account when studying the microbiology of the oil sands.

不同植物群落下铜尾矿废弃地生物结皮中真菌群落结构的比较

PDF HTML阅读 XML下载 导出引用 引用提醒 不同植物群落下铜尾矿废弃地生物结皮中真菌群落结构的比较 DOI: 10.5846/stxb201507181512 作者: 作者单位: 安徽大学资源与环境工程学院,安徽大学资源与环境工程学院,安徽大学资源与环境工程学院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金资助项目（41171418） Comparing the fungal community structure in biological soil crusts obtained under different plant communities in a copper mine tailings Author: Affiliation: School of Resources and Environmental Engineering,Anhui University,School of Resources and Environmental Engineering,Anhui University,School of Resources and Environmental Engineering,Anhui University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:分布于铜尾矿废弃地的裸地表面及维管植物群落中的生物土壤结皮在尾矿废弃地生态恢复过程中扮演重要角色。利用分子生物学技术探讨了不同维管植物下以及不同演替阶段的生物土壤结皮中真菌的多样性及其群落结构的变化。结果表明：生物土壤结皮中的真菌主要包括子囊菌门（Ascomycota）、担子菌门（Basidiomycota）和壶菌门（Chytridiomycota），其中子囊菌门占绝对优势，其相对丰度为55.12%-87.73%，其次为担子菌门相对丰度为12.27%-43.86%；不同样本真菌群落结构在门、纲、目以及属的水平存在显著差异；生物土壤结皮中真菌群落结构和多样性的差异与维管植物群落类型以及演替阶段不同的生物土壤结皮的类型有关，与基质化学性质之间无显著的相关性。 Abstract:Biological soil crusts (BSCs) found on the surface of bare wasteland and beneath the tracheophyte communities in mine tailing ponds, play an important role in the processes that are involved in natural ecological restoration of copper mine tailings. Fungi are an important part of BSCs, and they adhere to the surface soil and other components stably through their fungal hypha. It is important to enhance the resilience of mine tailings against wind erosion, as well as improve their moisture holding capacity that can be beneficial for the plant colonization on loose mine tailings' surfaces. However, the structure and diversity of microbial communities (especially fungal communities) of BSCs on the surface of mine tailings are poorly investigated. In this study, the changes in the fungal diversity and community structure of BSC samples at different successional stages, as well as tracheophyte species, were investigated using molecular biotechnologies. Moss-algal crusts beneath the Hippochaete ramosissimum (YM) had the lowest diversity index (including Shannon-Wiener index, Simpson index and Pielou index), among other significant differences of diversity and evenness that were observed in the fungal communities from the BSC samples and tracheophyte species. In addition, significant differences in basic soil chemical properties, such as loss-on-ignition, total nitrogen, and available phosphorus, were also found among the BSC samples. This indicates that the fungi in the BSC samples included the phyla Ascomycota, Basidiomycota, and Chytridiomycota. The phylum Ascomycota was dominant in these samples, and displayed a higher relative abundance 55.12%-87.73%, followed by the phylum Basidiomycota with a relative abundance of 12.27%-43.86%. Significant differences in fungal community structure were found at the phylum, order, class, and genus level. In addition, a non-metric multidimensional scaling (NMDS) analysis also showed that the fungal community structure is significantly influenced by tracheophyte species and the successional stage. However, canonical correlation analysis (CCA) indicated that this variation was not mainly caused by the substrate chemical properties of the mine tailings. In addition, Pearson correlations showed no significant correlation between fungal community structure and soil chemical properties. 参考文献 相似文献 引证文献

Natural Organic Matter Affects the Treatment of Mine Tailings through Bioleaching Processes

In the present study, the effects of natural organic matter (NOM) on metal bioleaching from mine tailings were investigated. NOM can enter into the bioleaching process either through mine tailings being exposed in the natural ground surface conditions or through the water quality in the bioleaching process. An analysis of the conditions resembling the interaction between NOM and mine tailings was conducted through the variation of the concentration of suspended NOM (0, 20, 50 ppm) and the amount of NOM (0, 20, 50 ppm) attached to the mine tailings surface. Different concentrations of Suwannee River Humic Acid (SRHA) were considered as the main source of NOM for the bioleaching experiments. The flask experiments were conducted using bacterial cultures of Acidithiobacillus ferrooxidans (1x107 cells/mL) grown in DSMZ medium 882 at a constant temperature of 30 °C, shaking speed of 150 rpm, and 1.8 as initial pH. The solid concentration was fixed at 0.5 % w/v of mine tailings (particle size of 100-150 µm), which were obtained from Janggun Mine, Gyeongsang, South Korea. No differences in extraction efficiency were observed in relation to variation of NOM concentration (0–50 ppm SRHA) attached to the surface of mine tailings. On the other hand, a reduction of approximately 10% to 15% of metal bioleaching efficiency (Zn) was observed due to the increment of suspended NOM concentrations, 20 and 50 ppm of SRHA, respectively.

Focal depths and mechanisms of shallow earthquakes in the Himalayan–Tibetan region

The complexity of the Himalayan–Tibetan lithospheric deformation is evident from widespread seismicity and diverse focal mechanism solutions. Here we investigate the focal depths and fault plane solutions of 97 moderate and shallow earthquakes in the Himalayan–Tibetan region by modeling teleseismic P-wave and its tailing surface reflections pP and sP. Earthquakes in central Tibet are restricted to the upper crust and originate dominantly by strike-slip faulting, in agreement with the low P-wave velocity layers in the lower crust and the strong S-wave attenuation zones in the uppermost mantle. In northern and southern Tibet, where the Asian and Indian plates descend beneath central Tibet, earthquakes appear to be distributed throughout the thickness of the crust and exhibit dominantly reverse faulting. We incorporate well-estimated focal depths of 127 additional earthquakes from previous studies to estimate the seismogenic thickness (Ts) of the study region. The resulting pattern of Ts is found to be rather flat for central and northeastern Tibet and highly variable along the strike of the Himalayan foreland.

Long-term mineralogical and geochemical evolution of sulfide mine tailings under a shallow water cover

The long-term influence of a shallow water cover limiting sulfide-mineral oxidation was examined in tailings deposited near the end of operation in 1951 of the former Sherritt-Gordon Zn–Cu mine (Sherridon, Manitoba, Canada). Surface-water, pore-water and core samples were collected in 2001 and 2009 from above and within tailings deposited into a natural lake. Mineralogical and geochemical characterization focused on two contrasting areas of this deposit: (i) sub-aerial tailings with the water table positioned at a depth of approximately 50cm; and (ii) sub-aqueous tailings stored under a 100cm water cover. Mineralogical analyses of the sub-aerial tailings showed a zone of extensive sulfide-mineral alteration extending 40cm below the tailings surface. Moderate alteration was observed at depths ranging from 40 to 60cm and was limited to depths >60cm. In contrast, sulfide-mineral alteration within the submerged tailings was confined to a <6cm thick zone located immediately below the water-tailings interface. This narrow zone exhibited minimal sulfide-mineral alteration relative to the sub-aerial tailings. Sulfur K-edge X-ray absorption near edge structure (XANES) spectroscopy showed results that were consistent with the mineralogical investigation. Pore-water within the upper 40cm of the sub-aerial tailings was characterized by low pH (1.9–4.2), depleted alkalinity, and elevated SO4 and metal concentrations. Most-probable number (MPN) enumerations revealed abundant populations of acidophilic sulfur-oxidizing bacteria within these tailings. Conversely, pore-water in the sub-aqueous tailings was characterized by near-neutral pH, moderate alkalinity, and relatively low concentrations of dissolved SO4 and metals. These tailings exhibited signs of dissimilatory sulfate reduction (DSR) including elevated populations of sulfate reducing bacteria (SRB), elevated pore-water H2S concentrations, and strong δ34S-SO4 and δ13C-DIC fractionation. Additionally, mineralogical investigation revealed the presence of secondary coatings on primary sulfide minerals, which may serve as a control on metal mobility within the sub-aqueous tailings. Results from this study provide critical long-term information on the viability of sub-aqueous tailings disposal as a long-term approach for managing sulfide-mineral oxidation.

Bioleaching of arsenic from highly contaminated mine tailings using Acidithiobacillus thiooxidans

The behavior of arsenic (As) bioleaching from mine tailings containing high amount of As (ca. 34,000 mg/kg) was investigated using Acidithiobacillus thiooxidans to get an insight on the optimal conditions that would be applied to practical heap and/or tank bioleaching tests. Initial pH (1.8–2.2), temperature (25−40 °C), and solid concentration (0.5–4.0%) were employed as experimental parameters. Complementary characterization experiments (e.g., XRD, SEM-EDS, electrophoretic mobility, cell density, and sulfate production) were also carried out to better understand the mechanism of As bioleaching. The results showed that final As leaching efficiency was similar regardless of initial pH. However, greater initial As leaching rate was observed at initial pH 1.8 than other conditions, which could be attributed to greater initial cell attachment to mine tailings. Unlike the trend observed when varying the initial pH, the final As leaching efficiency varied with the changes in temperature and solid concentration. Specifically, As leaching efficiency tended to decrease with increasing temperature due to the decrease in the bacterial growth rate at higher temperature. Meanwhile, As leaching efficiency tended to increase with decreasing solid concentration. The results for jarosite contents in mine tailings residue after bioleaching revealed that much greater amount of the jarosite was formed during the bioleaching reaction at higher solid concentration, suggesting that the coverage of the surface of the mine tailings by jarosite and/or the co-precipitation of the leached As with jarosite could be a dominant factor reducing As leaching efficiency.

Surficial weathering of iron sulfide mine tailings under semi-arid climate

Mine wastes introduce anthropogenic weathering profiles to the critical zone that often remain unvegetated for decades after mining cessation. As such, they are vulnerable to wind and water dispersion of particulate matter to adjacent ecosystems and residential communities. In sulfide-rich ore tailings, propagation to depth of the oxidative weathering front controls the depth-variation in speciation of major and trace elements. Despite the prevalence of surficial mine waste deposits in arid regions of the globe, few prior studies have been conducted to resolve the near-surface profile of sulfide ore tailings weathered under semi-arid climate. We investigated relations between gossan oxidative reaction-front propagation and the molecular speciation of iron and sulfur in tailings subjected to weathering in a semi-arid climate at an EPA Superfund Site in central Arizona (USA). Here we report a multi-method data set combining wet chemical and synchrotron-based X-ray diffraction (XRD) and X-ray absorption near-edge spectroscopy (XANES) methods to resolve the tight coupling of iron (Fe) and sulfur (S) geochemical changes in the top 2m of tailings. Despite nearly invariant Fe and S concentration with depth (130–140 and 100–120gkg−1, respectively), a sharp redox gradient and distinct morphological change was observed within the top 0.5m, associated with a progressive oxidative alteration of ferrous sulfides to (oxyhydr)oxides and (hydroxy)sulfates. Transformation is nearly complete in surficial samples. Trends in molecular-scale alteration were co-located with a decrease in pH from 7.3 to 2.3, and shifts in Fe and S lability as measured via chemical extraction. Initial weathering products, ferrihydrite and gypsum, transform to schwertmannite, then jarosite-group minerals with an accompanying decrease in pH. Interestingly, thermodynamically stable phases such as goethite and hematite were not detected in any samples, but ferrihydrite was observed even in samples with the lowest pH, indicating its metastable persistence in these semiarid tailings. The resulting sharp geochemical speciation gradients in close proximity to the tailings surface have important implications for plant colonization, as well as mobility and bioavailability of co-associated toxic metal(loid)s.

Mapping Changes in a Recovering Mine Site with Hyperspectral Airborne HyMap Imagery (Sotiel, SW Spain)

Hyperspectral high spatial resolution HyMap data are used to map mine waste from massive sulfide ore deposits, mostly abandoned, on the Iberian Pyrite Belt (southwest Spain). Mine dams, mill tailings and mine dumps in variable states of pyrite oxidation are recognizable. The interpretation of hyperspectral remote sensing requires specific algorithms able to manage high dimensional data compared to multispectral data. The routine of image processing methods used to extract information from hyperspectral data to map geological features is explained, as well as the sequence of algorithms used to produce maps of the mine sites. The mineralogical identification capability of algorithms to produce maps based on archive spectral libraries is discussed. Trends of mineral growth differ spectrally over time according to the geological setting and the recovery state of the mine site. Subtle mineralogical changes are enhanced using the spectral response as indicators of pyrite oxidation intensity of the mine waste piles and pyrite mud tailings. The changes in the surface of the mill tailings deserve a detailed description, as the surfaces are inaccessible to direct observation. Such mineralogical changes respond faithfully to industrial activities or the influence of climate when undisturbed by human influence.

Erosion processes in anthropogenic systems in the South of the Russian Far East

The results of studying erosion processes in anthropogenic systems in the South of the Russian Far East are given. The surface of tailings dumps has been shown to be subjected to not only air and wind but also chemical erosion, which creates a great hazard to the environment and human health. A direct relation has been found between the anthropogenic material discharge and precipitation amount. Its maximal value during intense erosion processes has been estimated. A set of measures has been proposed to reduce the impact of erosion processes in mining anthropogenic systems.