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The health risks associated with exposure to respirable dust in coal mines have been attracted much attention by an increasing number of researchers. However, the accurate identification of potentially hazardous agents in respirable dusts and the evaluation of the potential health risks arising from it still remains controversial to varying degrees. A comprehensive understanding of the physicochemical properties of respirable dust is a prerequisite and an important basis for resolving this controversy. Therefore, in this study, the particle size distribution and morphology, pore structure, mineralogical and geochemical patterns, and oxidative potential (OP) of respirable coal mine dust were comprehensively investigated. Stepwise multiple linear regression was employed to identify dust components driving OP, such as anatase, tobelite, quartz, and ankerite, in respirable coal mine dust, along with Na, Ni, Se, W, and As. On this basis, we performed a single-factor risk prediction for different coal mines by considering factors that may impact miners' health, with the analyses yielding somewhat contradictory results. Therefore, a multifactor integrated prediction model is proposed using an entropy-based technique for order preference by similarity to the ideal solution to categorize coal mines in the study area into three risk categories, high-, medium-, and low-risk dust mines, which is important for the hierarchical classification and control of coal mines and for formulating appropriate dust prevention and control measures. [Display omitted] • A comprehensive investigation of the physicochemical and oxidative potential characteristics of respirable coal mine dust (RD). • Stepwise multiple linear regression was employed to identify the potentially hazardous agents of RD. • The TOPSIS was used to comprehensively evaluate health risks in various coal mines and sites within those mines. [ABSTRACT FROM AUTHOR]

The coals from the Jungar Coalfield, Inner Mongolia, China, have been found to be enriched in Ga and Li. These are valuable metals that are potentially recoverable from coals and/or coal combustion residues. Based on fifteen roof/floor/parting samples collected from one borehole and one hundred and forty one bulk coal samples collected from three boreholes in the Buertaohai-Tianjiashipan coal mining district, Jungar Coalfield, this paper reports new data on the mineral compositions and geochemical characteristics of the Jungar Li-Ga-rich coals, and provides new evidence for the origin and mode of occurrence of Al, Ga and Li in these coals. The main mineral phases occurring in the coals are kaolinite, boehmite, calcite, with small proportions of quartz, pyrite, ankerite, siderite, and trace amounts of microcline and rectorite. An unusual mineral phase, svanbergite (SrAl 3 (PO 4 )(SO 4 )(OH) 6 ) also occurs as a main mineral constituent in the studied coals. The mineral phases in the roof/floor/parting samples are dominantly kaolinite, with a small proportion of quartz. Kaolinite is of both terrigenous and authigenic origin, which were possibly derived from terrigenous Yinshan Oldland sediment-source region and/or from recrystallization during the coal formation process. Boehmite and svanbergite are primarily of authigenic origin, and were dominantly derived from the weathered bauxite sediment-source region. Calcite may have formed by dissolution of limestone layers close to the margin of coal basin and subsequent deposition of the Ca or Mg-rich carbonates in the cells/fractures of the coal seams. Sulfide minerals in fractures may have been precipitated from epithermal fluids. Rectorite was probably formed by the reaction of kaolinite with epigenetic low-temperature hydrothermal fluids during diagenesis. Compared to common Chinese and worldwide coals, the studied Jungar coals are much more enriched in Al (4.4–6.1%), Li (70–79 mg/kg), and Ga (14–19 mg/kg). Titanium, P, Sr, Zr, Nb, Th, Ta, Hf, and rare earth elements (REEs) are also enriched in the studied coals to some extent. Aluminum in the coals mainly occurs in the form of kaolinite and boehmite, whereas, lithium may be associated with aluminosilicate minerals (kaolinite and illite if present) as well as svanbergite. Gallium principally occurs in kaolinite, and to a lesser extent, svanbergite. Strontium, P, and LREEs (La, Ce, and Rr, Nd and Sm) mainly present in svanbergite. The source of Li and Ga in Jungar coals is most likely from the Yinshan Oldland region, but there is also a possibility of migration from bauxite of the Benxi formation. [ABSTRACT FROM AUTHOR]

Oxidative potential (OP) is considered to be an efficient indicator of particulate matter (PM) to induce oxidative stress in the lungs and is increasingly considered to be a relevant health metric. In this study, two complementary OP assays were deployed, including dithiothreitol (DTT) and ascorbic acid (AA) assays, to investigate the potential toxicity (as generators of oxidative stress) of respirable fractions (DD4, < 4 μm) of deposited dust (DD500, < 500 μm) in underground low-S and low-pyrite coal mines in Henan Province, Central China. The OPDTT of DD4 is higher than that reported for other types of atmospheric PM, whereas the OPAA of DD4 is similar and/or slightly higher. Cross-correlation and multilinear regression analyses are applied using datasets of major mineral and geochemical patterns in the DD4 samples and the respective OP values to identify the major drivers for OP in respirable coal dust. Thereafter, the patterns of DD4 are compared with those of DD500 and the parent coals to determine the sources of OP-relevant substances. OPDTT is mainly governed by some trace elements (Sb, As, Li, B, Sr, and Pb) and minor minerals (anatase, quartz, siderite), and their synergistic effect may be one of the reasons for the high DTT consumption. For OPAA, quartz, total clay (sum of illite, kaolinite, tobelite, and clinochlore) and Ni, Cr, Co, Si, and S, play an important role in regulating the OPAA of pyrite-free DD4 samples. These OP-relevant substances have three sources: coal dust, which has a similar composition in DD4, DD500, and the parent coal (such as siderite and its associated elements); gangue dust, which does not occur in the parent coal but is widely detected in DD4 and DD500 (such as quartz, kaolinite, and relevant elements); and cement dust (from gunite galleries), which is mainly calcite- and calcite-associated elements. • A study of the mineralogy, geochemistry and OP of deposited dust, respirable dust and coal in underground coal mines. • OPDTT of size-segregated respirable dust (DD4) is mainly governed by anatase, siderite, quartz, and Sb, As, Li, B, Sr, Pb. • OPAA of DD4 is regulated by anatase, tobelite, kaolinite, and total clay, as well as Ni, Cr, Co, Si, and S. • The parent coal dust, gangue dust, and cement dust are the primarily source of these hazardous materials. [ABSTRACT FROM AUTHOR]

Abstract: The Yimin Ge-coal deposit, located in the Yimin coalfield, Inner Mongolia, is the third largest Ge-rich coal deposit in China just after the Lincang and Wulantuga Ge-coal deposits. Based on the coal and non-coal samples recently collected from the Wumuchang coal mining district in the Yimin Ge-coal deposit, this paper reports some new data on the mineralogical and geochemical characteristics of the Yimin high-Ge coals, and provides some new evidence for the possible mode of Ge enrichment in the Yimin coals. Mineralogical analyses were performed by means of Powder X-ray diffraction (XRD). Major and trace element concentrations were determined by inductively coupled plasma atomic-emission spectrometry (ICP-AES) and inductively coupled plasma mass spectrometry (ICP-MS), respectively. Element affinities were determined by Pearson's correlation analysis. The studied coals fall within the coal rank between sub-bituminous A and high volatile bituminous C, with relatively high moisture content, high volatile matter yield and low to medium ash yield. Quartz and kaolinite are the main mineral matters in the Yimin coals, with small amounts of pyrite and traces of microcline. Common pyrite and As-bearing pyrite occurring in the Yimin coals show an epigenetic origin. The epigenetic precipitation of kaolinite, quartz and As-rich pyrite (with Ge, and other trace elements) in the Yimin coal fractures may be caused by activities of both hydrothermal and low temperature fluids. Compared to common Chinese and worldwide coals, the Yimin coals are markedly enriched in Ge (43mg/kg), As (155mg/kg), and W (9.84mg/kg) and slightly enriched in Pb (22mg/kg) and Hg (0.24mg/kg). Most of the elements (e.g. Al, K, Sc, Ti, V, Cu, Ga, Sn, Th and REEs) in the studied coals present an aluminosilicate affinity as deduced from their obvious positive correlation with Al and ash yields. High correlation coefficients of As and Hg with Fe and S indicate a sulfide affinity of these elements in the Yimin coals. Germanium, B, Mo, and W in the studied coals show an organic affinity and a partial sulfur affinity as deduced from their negative correlation with Al and positive correlation with S, respectively. The preliminary and possible model for Ge enrichment in the Yimin Ge-coal deposit was that Ge was carried by hydrothermal fluids and then these fluids were incorporated in the water existing in the upper porous conglomerates and percolate in the top of the coal seam, where Ge was trapped by organic matter and finally enriched in an early diagenetic stage (humification–gelification). [Copyright &y& Elsevier]

Highlights: [•] Large amounts of coal fly ashes generated from power plants in Xinjiang, Northwest China. [•] Synthesis of high value-added zeolite from fly ash by KOH direct conversion method. [•] Utilize synthetic merlinoite product as efficient slow release potassic fertilizer. [•] Application potential of merlinoite for soil reclamation around opencast coal mines. [Copyright &y& Elsevier]

This study systematically investigates the mineralogical and geochemical variations in parent coal, coal gangue (roof, parting, and floor), deposited coal mine dust (DD), and respirable fractions of DD (RD) in an underground coal mine using the blasting mining method in China to evaluate the major sources of DD. The emission of dust in this study is affected by coal gangue sources during the mining process, which causes different geochemical patterns in the DD samples. Moreover, weathering of the cement gunite walls plays an important role in the enrichment of specific elements in the DD from air uptake and air out galleries. Furthermore, the spatial variation in RD characteristics, including mineralogy, geochemistry, and oxidative potential (OP), is discussed, with emphasis on the major health-relevant species and elements. Organic species from coal dust seem to be the essential components contributing to OP rather than metals, although some metals (e.g., Cr, Co, Ge, Se, Zn, Ba, Rb, Cs, Sn, and Pb) influence OP to some degree. [Display omitted] • Deposited coal mine dust, parent coal, and gangue in an underground coal mine using blasting mining method were studied. • Gangue and cement dust mixed into coal dust result in the enrichment of abundant elements. • The primary species driving the oxidative potential are site-dependent. • Organic species, quartz, calcite, and Cr, Co, Ge, Zn, Ba, Rb are highly correlated with toxicity. [ABSTRACT FROM AUTHOR]

Abstract: The Zhundong coalfield is a very large coal deposit, currently under exploration, and promises to be an important coal mining resource in Western China. The coal reserves amount to 164Gt. At Xiheishan and Wucaiwan, the coal-bearing units are the Badaowan (Lower Jurassic) and, especially, the Xishanyao formations (Middle Jurassic). These contain from one to 31 coal seams (one to 10 workable coals reaching the rank of high volatile A bituminous) with an accumulated workable coal thickness of 20–87m. These recently explored coal reserves are of a high quality and are characterized by low ash, aluminum, iron, sulfur, and trace element contents. The minerals present in this coal are mainly quartz, kaolinite, siderite, and pyrite. The trace element contents in both Xiheishan and Wucaiwan coals are much lower when compared with the usual concentration ranges present in Chinese coals, with the exception of Ba and Sr. Thus, Ba contents in Xiheishan coal are higher than Swaine''s worldwide concentration range. A large number of elements have mainly aluminosilicate affinity, and occur in clay and other detrital coal minerals. Ca and Mn have mainly carbonate affinity; Fe and S have mainly sulphide affinity in Wuchaiwan coal. In Xiheishan, Fe, Mn and Mg have mainly carbonate affinity (siderite), and probably, B, Co, Ni and S have an organic affinity. Thus, the Zhundong coalfield contains coal with a very high quality and very low levels of impurities. The very low ash yields, S, Fe, and trace element contents may be attributed to the sedimentological setting, with intensive peat bog aggradation in a very shallow lake environment with a low detrital supply. The very low sulfur content, the relatively high Ba-sulfate (barite) content and the high siderite occurrence in Xiheishan coal (in contrast to the pyrite occurrence in Wucaiwan coal) may be attributed to the rapid aggradation of peat with the consequent oxidation and leaching of minerals, elements, and degradation of organic components. Under this scenario, sulfate is trapped by the continuous precipitation and accumulation of barium sulfate (very low soluble). [Copyright &y& Elsevier]

Previous investigations on major and trace elements within the Early Permian coals from Xinjiang Province are very scarce. This paper reports on the geochemistry of the Early Permian coals and associated non-coal rocks in the Jimunai depression, Xinjiang Province, northwestern China. Samples collected from coal exploration boreholes ZK2603, ZK3003, and ZKH1102 as well as the Haerjiao underground coal mine (Nos. HRJ-7 and HRJ-9 Coals) in the Jimunai Depression were analyzed using SEM-EDS, ICP-AES, and ICP-MS. These Early Permian coals reach the rank of semi-anthracite to anthracite and have low-sulfur contents (0.30% on average). In comparison with the average element concentrations of world coals, Zr, Hf, and rare earth elements and Y (REY) are slightly enriched (concentration coefficient (CC) = 2–5, as the ratio of element content in sample vs. that in world coals) and Mn is enriched (CC = 5–10) in the ZK2603, ZK3003, and ZKH1102 coals. Niobium and Ta are highly enriched in the ZK2603 and ZK3003 coals (CC = 10–100). The HRJ-7 and HRJ-9 coals are slightly enriched in Mn (CC = 2–5). The coals have a sediment source region mainly composed of intermediate-felsic compositions from the Saur Volcanic Arc to the south of the Jimunai Depression, which may have provided relatively high geochemical background concentrations of Zr, Hf, Nb, and Ta. Manganese is hosted mainly in ankerite that was derived from epigenetic precipitation from Mn-bearing hydrothermal fluids. Zirconium and Hf in the ZK2603, ZK3003, and ZKH1102 coals are controlled primarily by detrital matter or hydrothermal fluids, the latter of which results in the higher Zr/Hf ratio in the ZK2603 and ZK3003 coals due to the re-distribution of Zr and Hf. Niobium and Ta in the ZK2603 and ZK3003 coals are concentrated chiefly in zircon, and hydrothermal fluid activity caused the release of Nb and Ta from previously-existing inorganic constituents and subsequent incorporation into zircon, resulting in the lower Nb/Ta ratio due to Ta being more easily incorporated into zircon than Nb. REY are hosted primarily within multiple mineral phases (e.g., zircon, phosphates, anatase, clay minerals) and their enrichment results from a combination of detrital matter input and hydrothermal fluid influx, the former of which is evidenced by the occurrence of REY-bearing detrital zircon and anatase, and the latter of which is indicated by the existence of REY-bearing authigenic rhabdophane and anatase and corroded anatase particles, as well as by the positive Gd anomalies and MREY-type or HREY-type REY distribution patterns. • The elevated Zr, Hf, Nb, and Ta are hosted mainly in zircon. • Hydrothermal fluid causes redistribution of Zr, Hf, Nb, Ta, and REY. • The enhanced Mn concentration was derived from epigenetic hydrothermal solution. • Terrigenous material and hydrothermal activity contribute to geochemical anomaly. [ABSTRACT FROM AUTHOR]

Underground coal mining produces large amounts of mine water annually in the Shendong mining area of China. Due to the severe scarcity of water resources, mine water is extensively used for productive, domestic, and ecological demands. However, mine water exhibits high fluoride levels. For water-use security, reduction of fluoride exposure and environmental protection, knowledge of sources and geochemical controls of fluoride enrichment in mine water is required. The results showed that F− concentrations of mine waters vary from 0.05 to 11.65 mg/L, with a mean value of 1.96 mg/L, and 51% of the mine waters contain F− concentrations exceeding the Chinese drinking water standard (1 mg/L). The overall mine water quality is influenced by cation exchange, mineral dissolution, pyrite oxidation, silicate weathering and so on. The high-fluoride mine waters are all associated with Na–type, with a remarkable cation composition feature of higher Na+ and lower Ca2+ and Mg2+ concentrations. Overall, the high-fluoride mine waters are well-matched with the water environment with higher pH, TDS, and EC levels. PCA reveals that the geochemical controls on the enrichment of F− in mine waters include dissolution of fluoride-bearing minerals and F−-OH− ion exchange; the former process is mainly caused by the decrease in Ca2+ concentrations resulting from Na + -Ca2+ cation exchange and mineral precipitation, and the latter process benefits from a highly alkaline water environment, facilitating the substitution of OH− in the mine water for F− within or absorbed on the minerals. Evaporation also controls F− enrichment in local areas. [Display omitted] • 51% of mine water samples exceed the Chinese drinking water limit for fluoride (1 mg/L). • The overall mine water quality is influenced by cation exchange, dissolution of minerals and so on. • NaHCO 3 type mine water possesses the highest average fluoride concentration. • Fluoride concentrations are overall proportional to higher pH, TDS, and EC levels. • Fluoride enrichment is related to ion exchange, mineral precipitation, and evaporation. [ABSTRACT FROM AUTHOR]

Coal mining in China is continually increasing, and the associated emitted coal mine dust is of growing environmental and occupational concern. In this study, deposited coal mine dust (DD) was analysed in three different regions of an active, highly-volatile bituminous open-pit coal mine in the Xingjian Province, Northwest of China: coal working fronts, tailings handling sites, and road traffic sites. Samples were analysed for particle size, and geochemical and mineralogical patterns, and then compared with the respirable DD fractions (RDDs, <4 μm) separated from DD samples. Online measurements of ambient air concentrations of particulate matter (PM 10 and PM 2.5), black carbon (BC) and ultrafine particles (UFP) were performed in the same mine zones where DD was sampled. Furthermore, the RDD samples were subjected to analysis of specific biological response or toxicological indicators (oxidative potential, OP). The results demonstrated: i) large differences in particle size and composition among DD from tailings handling, road traffic and coal working front sites, ii) a strong influence of the DD moisture contents and ash yields on particle size, and, accordingly, on the potential dust emissions, iii) an enrichment of multiple elements (such as Nb, Th, Cr, Sr, Li, As, Pb, Cu, Zr and Ni) in the RDD from coal working fronts compared with their contents in the worked parent coal seams, mostly attributed to mining machinery, tyre and brake wear emissions and to deposition of dust emitted from gangue working zones, iv) low OP values of the RDD emitted from the studied mine, which works a high-quality coal, with OP being influenced by Mn, sulphate and anatase (TiO 2) contents, and v) the impact of specific mining operations and mine areas on the levels of air pollutants, such as high PM from tailings handling in the upper parts of the mine or the high UFP levels in the bottom of the mine (due to vehicle and machinery emissions and lower dispersive conditions). The data presented here demonstrate the necessity of extracting the more deeply respirable size fraction of coal mine dusts in future studies on the health effects of these materials because this finer fraction is mineralogically and geochemically different from the parent rocks. • High impact of specific mining operations in ambient air pollutants. • Particle size distribution of deposited dust (DD) was different over mine sites. • Moisture and ash have strong influence on respirable DD (RDD) emissions. • Enrichment of multiple elements in RDD attributed to mining activities. • Oxidative potential of RDD is influenced by Mn, sulphate and anatase contents. [ABSTRACT FROM AUTHOR]

• Respirable fraction of dust deposited inside coal mines was extracted and analysed • Respirable coal dust is enriched in minerals related to parent coal geochemistry • Deposited coal mine dust can be used as a proxy for the geochemistry of PM10 • Fe, Si, Mn, Ba and particle size of coal dust are highly correlated with toxicity We focus on a comparison of the geochemistry and mineralogy patterns found in coal, deposited dust (DD), respirable deposited dust (RDD) and inhalable suspended dust (PM10) from a number of underground mines located in China, with an emphasis on potential occupational health relevance. After obtaining the RDD from DD, a toxicological analysis (oxidative potential, OP) was carried out and compared with their geochemical patterns. The results demonstrate: i) a dependence of RDD/DD on the moisture content for high rank coals that does not exist for low rank coals; ii) RDD enrichment in a number of minerals and/or elements related to the parent coal, the wear on mining machinery, lime gunited walls and acid mine drainage; and iii) the geochemical patterns of RDD obtained from DD can be compared with PM10 with relatively good agreement, demonstrating that the characterization of DD and RDD can be used as a proxy to help evaluate the geochemical patterns of suspended PM10. With regards to the toxicological properties of RDD, the Fe content and other by-products of pyrite oxidation, as well as that of anatase, along with Si, Mn and Ba, and particle size (among others), were highly correlated with Ascorbic Acid and/or Glutathione OP. [ABSTRACT FROM AUTHOR]