Lead Zinc Research Articles

Calcareous Materials Effectively Reduce the Accumulation of Cd in Potatoes in Acidic Cadmium-Contaminated Farmland Soils in Mining Areas.

The in situ chemical immobilization method reduces the activity of heavy metals in soil by adding chemical amendments. It is widely used in farmland soil with moderate and mild heavy metal pollution due to its high efficiency and economy. However, the effects of different materials depend heavily on environmental factors such as soil texture, properties, and pollution levels. Under the influence of lead–zinc ore smelting and soil acidification, Cd is enriched and highly activated in the soils of northwestern Guizhou, China. Potato is an important economic crop in this region, and its absorption of Cd depends on the availability of Cd in the soil and the distribution of Cd within the plant. In this study, pot experiments were used to compare the effects of lime (LM), apatite (AP), calcite (CA), sepiolite (SP), bentonite (BN), and biochar (BC) on Cd accumulation in potatoes. The results showed that the application of LM (0.4%), AP (1.4%), and CA (0.4%) had a positive effect on soil pH and cations, and that they effectively reduced the availability of Cd in the soil. In contrast, the application of SP, BN, and BC had no significant effect on the soil properties and Cd availability. LM, AP, and CA treatment strongly reduced Cd accumulation in the potato tubers by controlling the total ‘flux’ of Cd into the potato plants. In contrast, the application of SP and BN promoted the migration of Cd from the root to the shoot, while the effect of BC varied by potato genotype. Overall, calcareous materials (LM, CA, and AP) were more applicable in the remediation of Cd-contaminated soils in the study area.

The roles of hydrocarbons on the mineralization of Carlin-type gold deposits, Nanpanjiang Basin, South China

The spatial association of hydrocarbons with metalliferous ore deposits, like MVT lead–zinc deposits, sandstone uranium deposits and various type gold deposits (epithermal Au-Ag (-Hg) deposits, orogenic gold deposits and Carlin-type gold deposits) is found worldwide. However, the genetic relationship between hydrocarbon evolution and mineralization is still under controversy. Integrating isotope dates related to timing of petroleum evolution and gold mineralization from published data, as well as high-resolution transmission electron microscopy (TEM) analysis of pyrobitumen, electron probe microanalysis (EPMA) on both pyrobitumen and pyrite, the In-situ S isotope analyses of the gold-bearing pyrite in this study, we consider different type hydrocarbons (liquid oil and gas) played different roles on the mineralization of Carlin type gold deposits. As the residue of liquid oil cracking, the widespread high maturity pyrobitumen within the reservoir indicate both oil and gas has ever accumulated in the Nanpanjiang Basin. The high gold abundance (EPMA: ∼120 ppm; TEM: ∼1500 ppm) within the pyrobitumen in agreement with the metal solubility experiment suggest liquid oils could have acted as gold carrier before metal precipitation. The late Triassic timing overlapping between gas generation and gold mineralization and the δ34S features with gold bearing pyrite ∼ 10 ‰ lighter than the coeval seawater sulfate indicate gas dominated TSR process may play an important role on the supply of gold bisulfide complex (Au(HS)2−) in the ore-forming fluid and directly involved the precipitation of the Carlin-type gold deposit.

Influence of open cast mining on radiological health risk of agricultural soils around Adudu lead–zinc mine, Nasarawa State, Nigeria

Various fields of science have focused on the level of natural radionuclides in the environment since they are responsible for terrestrial background radiation exposure to members of the public. Gamma ray spectrometry with high purity germanium (HPGe) detector was used to measure the activity concentrations of natural radionuclides {238U (226Ra), 232Th and 40K} in one hundred and ten (110) composite soil samples collected from eleven (11) studied sites around lead (Pb)–zinc (Zn) mine. Result showed that the mean activities of 238U (226Ra), 232Th and 40K in the investigated soils varied between 28.49 ± 2.93–72.95 ± 7.07, 33.97 ± 4.09–105.78 ± 9.91 and 27.37 ± 1.87–853.16 ± 45.95 Bq/kg respectively. The activity concentrations of the analyzed natural radionuclides and their evaluated radiological health hazard parameters for soils around the mine, were above global average values and higher than those of control soil. The levels of 238U (226Ra), 232Th and 40K and the values of assessed radiological health hazard parameters for the control soil, were all lower than the global average values. This research showed that open cast mining of Pb–Zn in Adudu significantly increased the radiological health risk posed to the mine workers and community dwellers.

Integration of multi-sensor remote sensing, geological and geochemical data for delineation of Pb–Zn bearing carbonates of Middle Aravalli group in Zawar–Dungarpur Belt, NW India

The rocks of the Aravalli Protocontinent of NW India are enriched in lead–zinc bearing deposits amongst which the Zawar mineralized belt is one of the famous for base metal deposits and was mined since ancient times. In the present study, an attempt has been made to identify and map the extension of the mineralized belt and base metal prognostic zones using the integration of multi-sensor remote sensing, geological and geochemical data. Remote Sensing studies were carried out using ASTER, AVIRIS-NG, and ASAR datasets to understand the extension and associated structural features of host rocks (dolomite in the present case) of lead–zinc mineralization from the Middle Aravalli Group. Relative band depth (B6 + B9/B8) was used to delineate the dolomite of the region using the ASTER imagery. Mineral map was derived using the AVIRIS-NG dataset with the help of the MTMF algorithm. Multifrequency and multipolarization ASAR datasets demarcated the structural features in the complexly deformed rocks of the extended belt. The obtained results from remote sensing were validated with the help of geological and geochemical studies. Geological studies (field surveys and petrographic studies) confirmed the presence of dolomites and associative mafics. Mineralogical, major oxides and trace elements data further substantiated the presence of dolomite, associated sulfides such as galena, sphalerite, pyrite, and chalcopyrite, and lead, zinc and copper in the Zawar–Dungarpur Belt. Presence of chromium and nickel were observed through the trace element studies of dolomite belt. The trace elements interpolated maps were superimposed by traced structural maps using ASAR datasets. The densely populated E-W lineaments are considered the suitable zones for base metal accumulation. These lineaments carried the base metal bearing fluid along with a low concentration of Chromium and Nickel. Under the finding of this study, the northern head of Hati Magra and near Keekawat are the suitable zones for Pb–Zn sulfide mineralization.

Provenance Tracing and Age Analysis of Lead–Zinc Mineralization in Qiyimuchang, Inner Mongolia, NE China

The Qiyimuchang lead–zinc deposit is an important deposit in the Erguna Massif on the west slope of Daxinganling, for which the material source and age of mineralization remain unclear. The lead–zinc deposit in Qiyimuchang has been observed to occur in Jurassic volcanic strata as a vein-like orebody, and its strike is nearly perpendicular to that of the strata and the regional structures of the orogenic belt. The ore is mainly composed of sphalerite, galena, chalcopyrite, pyrite, and quartz, and hydrothermal alteration zones dominated by silicification, fluoritization, and pyritization are common within 1–5 m on both sides of the vein. The metasomatic lead–zinc mineralization is characterized by a massive vein structure. The mineralization process can be divided into three stages, pre-ore (mainly quartz, arsenopyrite and a small amount of pyrite), ore-formation (pyrite, chalcopyrite, sphalerite, galena, fluorite, and a small amount of tetrahedrite), and post-ore (quartz-calcite veinlets with a small amount of pyrite). Element and isotope geochemical studies show that the trace element compositions of the wall rocks (andesite, tuff, etc.) of Jurassic volcanic rocks in the ore bodies and surrounding rocks reflect affinity or similarity between them. The S isotopic composition of sulfide minerals in the metallogenic stage (δ 34SV-CDT = 1.6‰~4.8‰) indicate the sulfur isotopic composition of the magma. The Pb isotopic compositions of sulfide minerals (38.5–38.39, 15.55–15.62, and 18.33–18.41 for 208Pb/204Pb, 207Pb/204Pb, and 206Pb/204Pb, respectively) in the metallogenic stage are relatively concentrated and close to the average Pb isotopic compositions of the mantle and average Pb isotopic composition of an orogenic belt, indicating that the ore-forming metals are likely to be a mixed source of crust and mantle. A new zircon U-Pb age of 150.8 ± 1.3 Ma (MSWD = 0.74) was obtained from andesitic tuff. Collectively considering the regional geology and ore deposit geological analysis, the lead–zinc mineralization in Qiyimuchang possibly occurred during the early Cretaceous. The ore-forming processes belong to Cretaceous magmatic-hydrothermal activity in extensional tectonic setting.

Bio-accumulation effects of heavy metals Pb, Zn and Cd on Procecidochares utilis parasitism to Eupatorium adenophorum at Suzu metal mines, Yunnan

Procecidochares utilis is an obligatory parasitic insect to Eupatorium adenophorum. Both organisms have been spread to some metal mines areas. The objective of this study is to comprehend the trend of heavy metals transfer and the process of their bio-accumulation in the soil-E. adenophorum-P. utilis system and particularly their impact on the parasitic effect of P. utilis to E. adenophorum to reflect the impact of heavy metals on obligate parasitic insect and its host. Therefore, a detailed investigation was carried out at the Suzu Lead–Zinc Mine in Yunnan Province using the concentric circle's method. The results showed that the parasitic rate of P. utilis to a single plant and branch is positively correlated with distance. The metals content of the soil in E. adenophorum and P. utilis, decreased dramatically with an increase in distance away from the center of the mining area. From which is cleared that these metals could enter to E. adenophorum and P. utilis through the soil-E. adenophorum-P. utilis system which likely to affect its parasitic activities. In addition, the parasitic rate is impacted by per Zn content greatly, and the parasitic rate per plant is affected by Cd content enormously. This work could provide important basis of data for further understanding and clarifying the effects of bioaccumulation and heavy metals pollution on various aspects of the food chain. Simultaneously, it could clarify and simplify whether heavy metal contamination affects the parasitic behaviour of some obligatory parasitic insects.

Streptomyces plumbidurans sp. nov., a Pb2+-tolerant actinomycete.

A novel actinobacterium, designated KC 17012T, was isolated from lead zinc tailings collected from Lanping, Yunnan, PR China. Comparative 16S rRNA gene sequencing showed that KC 17012T belonged to the genus Streptomyces and was most closely related to the type strains of Streptomyces neyagawaensis (98.34%), Streptomyces panaciradicis (98.34%) and Streptomyces heilongjiangensis (98.27%). Phylogenetic tree analysis revealed strain KC 17012T formed a distinct clade. The genome size was 8.64 Mbp with a DNA G+C content of 70.8%. Digital DNA-DNA hybridization and average nucleotide identity values between the genome sequence of strain KC 17012T and those of S. neyagawaensis JCM 4796T (25.3 and 81.5 %) and S. panaciradicis NBRC 109811T (30.1 and 85.7 %) were below the thresholds of 70 and 96% for prokaryotic conspecific assignation. The strain formed long straight aerial hyphae which generated regular short rod spores with spiny surfaces. Growth occurred at 10-45 °C, pH 6-8 and with 0-9 % NaCl (w/v). Strain KC 17012T contained ll-diaminopimelic acid and the major whole-cell hydrolysates included glucose, mannose and ribose. The menaquinones were MK-9(H4), MK-9(H6) and MK-9(H8). The major cellular fatty acids were iso-C15 : 0, anteiso-C15 : 0, iso-C16 : 0 and anteiso-C17 : 0. The polar lipid profile consisted of diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylinositol, phosphatidylinositol mannoside, one unidentified lipid and one unidentified phospholipid. On the basis of the results of a polyphasic taxonomic study, it is concluded that KC 17012T represents a novel species of the genus Streptomyces, for which the name Streptomyces plumbidurans sp. nov., is proposed. The type strain is KC 17012T (CGMCC 4.7704T=JCM 35204T).

Study on leaching behaviour of germanium and iron in zinc oxide dust from lead zinc smelting

ABSTRACT Zinc oxide dust from lead zinc smelting is an important raw material for germanium recovery. This article researched the behaviour of germanium and iron in zinc oxide dust leaching in response to the problem of low germanium leaching efficiency. For this purpose, the germanium phase distributions were confirmed, the effects of sulphuric acid concentration, liquid–solid ratio, leaching temperature, and leaching time were determined. According to the findings, germanium exists primarily in the form of soluble germanium oxide and germanates. In addition, the germanium leaching efficiency is most affected by the leaching time, because the leaching iron will be oxidised and create Fe4Ge3O12 precipitation with the leaching germanium if the leaching time is too long, resulting in the decline of germanium leaching efficiency. The leaching efficiency of zinc and germanium can reach 89.05% and 84.32%, respectively, when the sulphuric acid concentration is 150 g/L, the liquid–solid ratio is 5:1, the leaching temperature is 85°C, and the leaching time is 30 min, which is 0.44% and 7.21% higher than that under unoptimised conditions. Furthermore, through sodium sulphite-assisted leaching, the leaching efficiency of germanium is further increased to 89.48%, indicating that reductant-assisted leaching is a direction worthy of study.

The bio-immobilization of Pb(II) induced by the Chlorella–montmorillonite composite in the Ca(II) environment

The clay–microbial consortium is ubiquitous in the soil near the mining area and plays an important role in the transport of heavy metals. In this study, Chlorella sorokiniana FK was separated from lead–zinc mine tailings. The montmorillonite–Chlorella sorokiniana FK system as a typical case was applied to study Pb(II) biomineralization in the presence of usually co-existent Ca(II) and further reduce the migration and transformation of Pb(II) in the Ca(II) environment. Chlorella sorokiniana FK showed good resistance to Pb(II), and the addition of montmorillonite provided a more stable pH environment, which is conducive to the stability of Pb(II)-bearing bio-minerals. Montmorillonite created a low-biotoxicity environment in the overall process, especially less Pb(II) bio-adsorption capacity of individual Chlorella to protect the process of mineralization effectively. Batch experiment results also demonstrated that montmorillonite as the formation site of bio-minerals results in dispersed minerals on the surface of Chlorella and Chlorella–MMT composite, which is beneficial to the survival of Chlorella. Moreover, Pb(II)-bearing phosphate minerals tended to form in the Ca(II) environment rather than without Ca(II). This study demonstrated the mechanism of Pb(II) immobilization induced by Chlorella in the Ca(II) environment, further presenting a green, sustainable, and effective strategy for Pb(II) bio-immobilization combining clay minerals and microorganisms.

Microstructural and compaction characteristics of tropical black clay soil subgrade modified with lead-zinc mine tailings

Lead–Zinc Mine tailings (LZMT) are wastes generated after the extraction of lead and zinc from mined mineral ore, whose disposal mechanism is gradually becoming environmentally unfriendly. For effective recycling of LZMT, this present study utilized a combination of LZMT and Portland limestone cement (PLC) to improve the compaction and microstructural characteristics of tropical black clay soil (TBCS) for use in pavement design and construction. The LZMT and PLC were added to the expansive soil in varying proportions with mix ratios generated from Taguchi orthogonal array. The result obtained for the compaction characteristics showed that the maximum dry density (MDD) increased significantly when a combination of 20% LMZT and 4% PLC were blended with the expansive soil. The increase in the MDD was attributed to the formation of cementitious compounds. In addition, the optimum mix ratio obtained from the unconfined compressive strength of the TBCS, was used for the evaluation of the pore structure characteristics which included porosity, tortuosity and permeability. The result obtained from the analysis that was implemented with a combination of fractal geometry and Bradley and Roth adaptive thresholding image segmentation technique, indicates the possibility of a slight reduction in the strength properties of the modified soil due to its high level of porosity. Also, the permeability and tortuosity values obtained from the present study suggest a slight increase in the permeability of the modified soil-additive mixtures which may not be unconnected to the occurrence of pozzolanic reaction that resulted in the agglomeration and flocculation of the LZMT-PLC modified TBCS. Furthermore, microstructural analysis was executed on the modified TBCS and LZMT using Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The result from the FTIR analysis indicates the pozzolanic character of LZMT in the presence of Si–O and Al–O tension bond with the bonds around 1000 cm−1 wavenumber, while the SEM analysis reveals the formation of a cementitious compound in the modified expansive soil-LZMT-PLC mixture.

Comparison of Phytoremediation Potential of Nerium indicum with Inorganic Modifier Calcium Carbonate and Organic Modifier Mushroom Residue to Lead-Zinc Tailings.

At present, the application of phytoremediation technology in the ecological remediation of heavy metal tailings is receiving more and more attention. In this study, the physiological and biochemical response and tolerance mechanism of woody plant Nerium indicum to Pb and Zn under different proportions of inorganic modifier calcium carbonate (C1: 5%, C2: 10%, C3: 15%) and organic modifier mushroom residue (M1: 10%, M2: 20%, M3: 30%) was compared. The results showed that the pH value has a trend of C group > M group > CK group and organic matter has a trend of M group > CK group > C group. Phosphatase activity and catalase activity has a trend of M group > C group > CK group, but catalase was more vulnerable to the calcium carbonate concentration. Both modifiers can promote the transformation of Pb, Zn, Cu, and Cd in tailings to more stable organic bound and residual states. However, the stabilization effect of mushroom residue is better, and its stability is Pb, Zn > Cd, Cu. Both modifiers can increase the biomass of Nerium indicum and the modification effect of mushroom residue is better than calcium carbonate. Pb/Zn content and accumulation in Nerium indicum organs showed root > stem > leaf in all groups. Compared with the CK group, the enrichment coefficient of Pb/Zn in C1 and M1 groups decreased, while the translocation factor of Pb/Zn in C1 and M1 groups increased. With the increase in modifier concentration, the enrichment coefficient increases about 1.75~52.94%, but the translocation factor decreases rapidly (20.01~64.46%). Clearly, both the calcium carbonate and mushroom residue amendment could promote the growth ability of Nerium indicum in lead–zinc tailings and strengthen the phytoremediation potential.

Study on Stope Stability in Continuous Mining of Long-Dip, Thin Orebody by Room–Pillar Method

In order to analyze the stability of the stope under continuous mining with the room–pillar method for a kind of orebody with a long inclination, but not deep mining, this paper takes the room–pillar method for the continuous mining of a long-inclination orebody in the Mengnuo Lead–Zinc Mine, Yunnan Province as the research background. On the basis of the analysis of the stope mechanical model of a long, inclined, thin orebody with room-and-pillar mining, based on numerical simulation, the nature of the change in stress, displacement and the plasticity zone of the roof and pillar during continuous mining along the inclination are systematically analyzed. The results show that as the mining depth increases, the roof subsidence of the stope in the middle of the current operation increases. With the continuous mining of the lower middle section, the roof displacement of the stope will continue to increase with the subsequent mining of the middle section until the end of all stope operations, and the roof displacement of the stope has an obvious cumulative effect. The stress on the roofs and pillars increases with the gradual downward movement of the mining in each level, and the distribution of the plastic zone also expands. It shows that the stope structural parameters that are set according to shallow mining cannot fully meet the requirements of stability and safety in mining a deeper orebody. Therefore, for the mining of a non-deep orebody with a greater tendency to extend, the structural parameters of a shallow stope should not simply be used in the mining of a deeper orebody, but the pillar size should be appropriately increased or the spacing between the room and pillar should be reduced to ensure the stability and safety of the continuous stope.

Tolerance and Heavy Metal Accumulation Characteristics of Sasa argenteostriata (Regel) E.G. Camus under Zinc Single Stress and Combined Lead–Zinc Stress

Sasa argenteostriata (Regel) E.G. Camus is a gramineous plant with the potential for phytoremediation. In this study, we aimed to determine its tolerance to zinc stress and combined lead–zinc stress and the effect of zinc on its absorption and accumulation characteristics of lead. The results showed that S. argenteostriata had good tolerance to zinc stress, and S. argenteostriata was not significantly damaged when the zinc stress concentration was 600 mg/L. Under both zinc stress and combined lead–zinc stress, the root was the main organ that accumulated heavy metals in S. argenteostriata. The presence of zinc promoted the absorption of lead by the root of S. argenteostriata, and the lead content in the root under PZ1, PZ2, PZ3 and PZ4 treatments was 2.15, 4.31, 4.47 and 6.01 times that of PZ0 on the 20 days. In the combined lead–zinc stress treatments, the toxicity of heavy metals to S. argenteostriata was mainly caused by lead. Under high concentrations of combined lead–zinc stress (PZ4), the proportion of zinc in the leaf of S. argenteostriata on the 20 days increased, which was used as a tolerance strategy to alleviate the toxicity of lead.

Grinding kinetics of lead–zinc tailing powders and its optimal particle size as a pozzolanic admixture in cement mortar

Recycling lead–zinc tailing powders (LZTPs) as pozzolanic admixtures can effectively solve its stockpiling and hazards problems synchronously, and mechanical grinding can increase the recycling utilization quantity and efficiency of LZTPs. Based on the laser particle size distribution (PSD) and activity index test results, the grinding kinetics, Rosin-Rammler-Bennet (RRB), Swebrec distribution model, and fractal theory of LZTPs have been studied. The results show that the grinding process of LZTPs is described quantitatively in the Divas-Alyaviden grinding kinetics equation, and the grinding efficiency of LZTPs becomes negligible after grinding for 120 min. Moreover, the PSD of LZTPs was remarkably consistent with the RRB, Swebrec distribution model, and fractal theory. The activity index increases with the grinding time. The gray correlational analysis revealed that a particle size range of 3.3 ∼ 6.5 μm presented a maximal positive effect on the activity index. In addition, the leaching toxicity of Pb, Cr, and Cd of LZTPs cement mortar block is below the standard limit of TCLP 1211 and it is safe to use the mortar with the addition of 30% LZTPs. The optimal grinding time for LZTPs was 90 min taking into account the economic and technical benefits.

Removal of arsenic in acidic wastewater using Lead-Zinc smelting slag: From waste solid to As-stabilized mineral.

High-arsenic wastewater has long been considered a major threat to ecological balance and human health because of its strong toxicity and high mobility. Herein, an environmentally friendly process was proposed for As removal and fixation in the form of As-stabilized mineral, using Lead-Zinc smelting (LZS) slag as the in situ Fe donor, neutralizer, and crystal seed. The slag was dissolved in the wastewater and released Fe and Ca ions, while simultaneously increasing the pH value of the solution to help scorodite synthesis. The dissolved Ca2+ ion preferentially reacted with SO42- ion in the form of CaSO4·2H2O precipitate as in situ "seeds" for As precipitation. The dissolved Fe(II) and As(III) ions were oxidized to Fe(III) and As(V) ions by H2O2, and later reacted with each other to generated amorphous ferric arsenate on the surface of CaSO4·2H2O, and then evolved into scorodite crystals with high stability. With a Fe/As molar ratio of 2, a reaction temperature of 90°C, and a reaction time of 12h, 98.42% of As was effectively precipitated from the wastewater with an initial As concentration of 7530.00mg/L. Moreover, the leached As concentration of the As-bearing precipitate in the TCLP test was 3.46mg/L. The concentration of the residual As and heavy metals ions in the final filtrate was lower than local wastewater discharge standards, successfully realizing the treatment of smelting wastewater. In summary, a prospective process successfully shows a great potential for co-treatment of LZS wastewater and slag, which could advance the large-scale disposal of LZS plants.

Distribution, Assessment, and Source of Heavy Metals in Sediments of the Qinjiang River, China.

Heavy metals are toxic, persistent, and non-degradable. After sedimentation and adsorption, they accumulate in water sediments. The aim of this study was to assess the extent of heavy metal pollution of Qinjiang River sediments and its effects on the ecological environment and apportioning sources. The mean total concentrations of Mn, Zn, Cr, Cu, and Pb are 3.14, 2.33, 1.39, 5.79, and 1.33 times higher than the background values, respectively. Co, Ni, and Cd concentrations are lower than the background values. Fe, Co, Ni, Cd, Cr, Cu, and Pb are all primarily in the residual state, while Mn and Zn are primarily in the acid-soluble and oxidizable states, respectively. Igeo, RI, SQGs, and RAC together indicate that the pollution status and ecological risk of heavy metals in Qinjiang River sediments are generally moderate; among them, Fe, Co, Ni, Cd, Cr, and Pb are not harmful to the ecological environment of the Qinjiang River. Cu is not readily released because of its higher residual composition, suggesting that Cu is less harmful to the ecological environment. Mn and Zn, as the primary pollution factors of the Qinjiang River, are harmful to the ecological environment. This heavy metal pollution in surface sediments of the Qinjiang River primarily comes from manganese and zinc ore mining. Manganese carbonate and its weathered secondary manganese oxide are frequently associated with a significant amount of residual copper and Cd, as a higher pH is suitable for the deposition and enrichment of these heavy metals. Lead–zinc ore and its weathering products form organic compounds with residual Fe, Co, Cr, and Ni, and their content is related to salinity. The risk assessment results of heavy metals in sediments provide an important theoretical basis for the prevention and control of heavy metal pollution in Qinjiang River.

Dust pollution hazard and harmful airborne dust exposure assessment for remote LHD operator in underground lead-zinc ore mine open stope.

Underground mines embroil several occupational hazards, including airborne dust generation from various mining operations. Line-of-sight remote Load Haul Dumper (LHD) mucking is adopted to draw the blasted muck from unsupported open stopes in underground metalliferous mines. Assessment of particulate matter (PM) concentrations and remote LHD operator's exposure is crucial for devising appropriate dust control measures. In this study, PM generated due to mucking in longhole open stope by line-of-sight remote LHD during downcast airflow was measured using real-time aerosol spectrometers. The particulate concentrations at upstream and downstream of dust source were analysed for various particle sizes as well as occupational dust types, such as alveolic and thoracic. The airborne dust concentration of ≤ 10μm (PM10), ≤ 5μm, and ≤ 1μm (PM1) size at operator's location in downstream was measured 71.3%, 28.5%, and 3.0%, respectively. The alveolic and thoracic dust types, respectively, were determined 25.1% and 74.2% in downstream and 48.9% and 84.6% in upstream total airborne dust concentration (311 ± 246μg/m3). Dilution of airborne dust generated due to muck sliding inside the stope was analysed with time. Moreover, dust concentrations under typical airflow scenarios encountered in open stope were simulated using Ventsim software to identify the potential dust exposure hazard for remote LHD operator. The simulation revealed that downcast airflow causes maximum exposure of harmful airborne dust for remote LHD operator. This study enhanced the understanding of exposure potential of airborne dust during remote LHD mucking. Moreover, it emphasised adoption of tele-remote-operated LHD and automated mucking operation in open stopes.

Contamination of potable water supply sources in the lead–zinc mining communities of Mkpuma Akpatakpa, Southeastern Nigeria

Contamination of potable water supply sources in the lead–zinc mining communities of Mkpuma Akpatakpa, Southeastern Nigeria

Variations of fungal communities in lead–zinc tailings located in Northwestern China

Investigation of microbial community structures is critical for situ-remediation of heavy metal contaminated soils. For this purpose, we used high-throughput 18S rRNA sequencing method to analyze soil fungal communities in the Shanping village (SPC) and Yanzibian (YZB) tailings situated in northwestern China. The relationships of the fungal community and the environmental factors, including heavy metals and soil chemical properties were analyzed. The results showed that the fungal community richness and diversity in the soils were both trending as control soil > contaminated soil. The compositions and relative abundances of the fungal populations in the two tailings were different, however the dominant fungal phyla of which were almost the same, mainly including Ascomycota, Basidiomycota, Calcarisporillomycota, Mortierellomycota, and Rozellomycota. Further, the Canonical correlation analysis and spearman correlation analyses revealed that Cd, Pb, Cu, Zn, Cr, TP, NO3 −-N, TN, and/or pH were predominantly positive correlation factors for the most abundant fungal phyla Ascomycota and Basidiomycota. Together, we have sorted out certain fungal species, such as s_unclassified_p_Ascomycota, s_unclassified_c_Sordariomycetes, s_Talaromyces_solicola, and s_Cutaneotrichosporon_curvatus, which are probably tolerant to heavy metals in these specific tailing soils. Overall, our results have provided an initial perspective of the fugal community variations of these specific tailing ponds.

Utilization of lead–zinc mine tailings as cement substitutes in concrete construction: Effect of sulfide content

Production of acid mine drainage and emission of heavy metals from tailings, especially sulfide tailings, to the environment is one of the serious challenges in the management of mine tailings. The use of cementation process and replacement of cement with mine tailings in the manufacture of concrete is one of the practical approaches to the management of mine tailings. In this study, two different lead-zinc mine tailings (T1 with 0.4% and T2 with 19% sulfide content) were separately used as a cement substitution in concrete construction. Toxicity characteristic leaching procedure (TCLP), acid generation potential, compressive strength tests, and mercury intrusion porosimetry (MIP) were conducted on the constructed concrete samples. The TCLP test results revealed that with increasing the curing time of the samples, the leaching rate of toxic metals (arsenic, cadmium, chromium, cobalt, nickel, copper, zinc, and lead) in all samples was reduced to lower than the permissible criteria, indicating the good stabilization of heavy metals in concrete samples. The MIP test results also revealed that with increasing the curing days and subsequently the hydration process, the intruded mercury volume decreased, indicating that heavy metals were stabilized in concrete samples. The compressive strength test findings revealed that in constructed concrete containing 20% cement-replacing T1, with increasing the curing time of the sample from 28 to 90 days, the compressive strength increased from 16.9 to 19.8 MPa, and the leaching rate of heavy metals decreased from 39.64 to 23.65 μg/L,. In addition, in the sample with 20% T2, the compressive strength increased from 10.59 to 16.4 MPa, and the leaching rate of heavy metals decreased from 44.65 to 26.5 μg/L. Comparing the Scanning Electron Microscope (SEM) and Energy Dispersive X-ray analyzer (EDX) results, it was found that the Ca/Si ratio was lower in the samples prepared with mine tailings compared to the control, indicating insufficient amount of calcium available to form the main hydration product (C–S–H). Therefore, less C–S–H gel was formed in these samples. Also, according to the elemental distribution analysis, it was revealed that other heavy metals were scattered throughout the concrete matrix and stabilized in the concrete structure by forming new compounds. In general, it could be concluded that cement replacement with lead-zinc mine tailings up to 20% without the use of any improvement technique may be possible. Further, the formation of hydration products affected by high sulfide content and causes the production of sulfide salts that attack the concrete sample over time, thereby reducing cementitious properties and strength.