Comprehensive evaluation of potential coal mine dust emissions in an open-pit coal mine in Northwest China

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 (PM10 and PM2.5), 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 (TiO2) 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.This study was supported by Generalitat de Catalunya (AGAUR 2017 SGR41), Spain; by the National Science Foundation of China (grant 41972180); the Program of Introducing Talents of Discipline to Universities (grant B14031) and Overseas Top Scholars Program for the Recruitment of Global Experts, China and by the Spanish Ministry of Science and Innovation (Excelencia Severo Ochoa, Project CEX2018-000794-S). Pedro Trechera is contracted by the ROCD (Reducing risks from Occupational exposure to Coal Dust) project supported by the European Commission Research Fund for Coal and Steel; Grant Agreement Number-754205.Peer reviewe

Geochemistry and oxidative potential of the respirable fraction of powdered mined Chinese coals

This study evaluates geochemical and oxidative potential (OP) properties of the respirable (finer than 4 μm) fractions of 22 powdered coal samples from channel profiles (CP4) in Chinese mined coals. The CP4 fractions extracted from milled samples of 22 different coals were mineralogically and geochemically analysed and the relationships with the OP evaluated. The evaluation between CP4/CP demonstrated that CP4 increased concentrations of anatase, Cs, W, Zn and Zr, whereas sulphates, Fe, S, Mo, Mn, Hf and Ge decreased their CP4 concentrations. OP results from ascorbic acid (AA), glutathione (GSH) and dithiothreitol (DTT) tests evidenced a clear link between specific inorganic components of CP4 with OPAA and the organic fraction of OPGSH and OPDTT. Correlation analyses were performed for OP indicators and the geochemical patterns of CP4. These were compared with respirable dust samples from prior studies. They indicate that Fe (r = 0.83), pyrite (r = 0.66) and sulphate minerals (r = 0.42) (tracing acidic species from pyrite oxidation), followed by S (r = 0.50) and ash yield (r = 0.46), and, to a much lesser extent, Ti, anatase, U, Mo, V and Pb, are clearly linked with OPAA. Moreover, OPGSH correlation was identified by organic matter, as moisture (r = 0.73), Na (r = 0.56) and B (r = 0.51), and to a lesser extent by the coarse particle size, Ca and carbonate minerals. In addition, Mg (r = 0.70), B (r = 0.47), Na (r = 0.59), Mn, Ba, quartz, particle size and Sr regulate OPDTT correlations. These became more noticeable when the analysis was done for samples of the same type of coal rank, in this case, bituminous.This study was supported by Generalitat de Catalunya (AGAUR 2017 SGR41), Spain; by the National Science Foundation of China (grant 41972180); the Program of Introducing Talents of Discipline to Universities (grant B14031) and Overseas Top Scholars Program for the Recruitment of Global Experts, China; and by the Spanish Ministry of Science and Innovation (Excelencia Severo Ochoa, Project CEX2018-000794-S). Malvern Mastersizer Scirocco 2000 extension measurements were performed at the ICTS NANBIOSIS by the Nanostructured Liquids Unit (U12) of the CIBER in Bioengineering, Biomaterials & Nanomedicine (CIBER-BBN), located at the IQAC-CSIC (Barcelona, Spain). Pedro Trechera is contracted by the ROCD (Reducing risks from Occupational exposure to Coal Dust) project supported by the European Commission Research Fund for Coal and Steel; Grant Agreement Number 754205.Peer reviewe

Mineralogy, geochemistry and toxicity of size-segregated respirable deposited dust in underground coal mines

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.This study was supported by Generalitat de Catalunya (AGAUR 2017 SGR41), Spain; by the National Science Foundation of China (grant 41972180); the Program of Introducing Talents of Discipline to Universities (grant B14031) and Overseas Top Scholars Program for the Recruitment of Global Experts, China; the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation, grant4 16816480) and by the Spanish Ministry of Science and Innovation (Excelencia Severo Ochoa, Project CEX2018-000794-S). Pedro Trechera is contracted by the ROCD (Reducing risks from Occupational exposure to Coal Dust) project supported by the European Commission Research Fund for Coal and Steel; Grant Agreement Number 754205.Peer reviewe