Botryoidal and spherulitic hematite as experimental evidence of highly acidic conditions in burning coal-waste dumps and potentially on Mars.

In the extreme setting of burning coal-waste dumps in the Upper Silesian Coal Basin in Poland, botryoidal and spherulitic hematite occurs in association with sulphates and chlorides. A series of simple experiments aimed at replicating the conditions leading to the formation of hematite spherules on the burning dumps are described. Goethite synthesised in the laboratory, mixed with various combinations of other reactants, was heated in a heating chamber or a tubular furnace. Temperature, duration of heating, water and oxygen access, and pH were experimental variables. The results show that hematite may form spherules from goethite where access to oxygen is limited and where conditions are strongly acidic. The spherulitic shape of hematite produced due to dynamically changing physicochemical conditions in the burning dumps can be an indicator of an extremely acidic environment during the closing stages of coal-waste self-heating. The conditions of hematitic-spherule formation on burning coal-waste dumps may apply in a variety of other unrelated settings, e.g., waning volcanism, sulphuric acid speleologenesis and even the formation of blueberries on Mars.

Heavy metal- and organic-matter pollution due to self-heating coal-waste dumps in the Upper Silesian Coal Basin (Poland).

This study provides potential insight between self-heating coal-waste dumps and related environmental pollution in southern Poland. Samples collected from dumps in the Upper Silesian Coal Basin were used to quantify released contents of organic- and inorganic pollutants, i.e., polycyclic aromatic hydrocarbons (PAHs) and trace elements (Pb, Cd, Cr, Cu, Zn, Ni, Hg, As). Elevated Hg concentrations (~100-1078 mg/kg) and Pb (~600-2000 mg/kg) attest to the evaporation of these metals from deeper parts of the dumps. The acidic pH levels (3.0-4.5) may help to mobilize these elements. Pearson's correlation coefficients for samples analyzed by AAS and ICP-MS indicate a similar origin for Cd, Zn, and As. Mostly 2- and 3-ring PAHs, especially anthracene in burnt soil, dominate in the samples. Chlorinated PAHs, thiophenol, pyridines, quinolines (and derivatives) in thermally-altered samples, and waste containing pyrolytic bitumen indicate coking conditions. The high levels of Hg, Pb, and Cd, and chlorinated PAHs and nitrogen heterocycles formed or enriched during self-heating in these dumps should be deemed a significant environmental hazard. Calculating the lifetime cancer risks due to PAHs and heavy metals accumulations in the dumps are substantial, and access to these dumps should be prohibited.

Correction to: Investigation of organic material self-heating in oxygen-depleted condition within a coal-waste dump in Upper Silesia Coal Basin, Poland.

The original publication of this paper contains a mistake.

Investigation of organic material self-heating in oxygen-depleted condition within a coal-waste dump in Upper Silesia Coal Basin, Poland.

Self-heating occurring was studied in the Bytom coal-waste dump using petrographic, mineralogical, and organic geochemical to assess the changes induced by heating on organic material and quantify-qualify the emitted gases. The distribution of geochemical markers such as n-alkanes, alkylbenzenes, alkylcyclohexanes, phenols, sulfurous compounds, and emitted gases in the waste dump is outlined. Heating of organic material there is indicated by high vitrinite random reflectance (Rr)% values that typically characterize samples with short-chain n-alkanes, alkylbenzenes, and alkylmethylbenzenes. Contents of minerals showing minor alterations are high with ~ 90% in burned-out samples. Inside the dump where temperatures can reach up to 700-1300 °C and oxygen contents are significantly reduced, conditions favor coking. This situation is confirmed by the formation of enormous quantities of phenols and alkylbenzenes or by elevated amounts of H2 formed under low-oxygen conditions (pyrolysis). Aromatization, pyrolysis (thermal cracking), and oxidation are associated with the heating in the dump. Gases such as methane, ethane, propane, and ethylene formed during self-heating can serve as fuel for the fire inside the dump, in the process generating huge amounts of CO2.

Carbon­nitrogen compounds, alcohols, mercaptans, monoterpenes, acetates, aldehydes, ketones, SF6, PH3, and other fire gases in coal-mining waste heaps of Upper Silesian Coal Basin (Poland) - a re-investigation by means of in situ FTIR external database approach.

Coal-fire gas jets emanating from waste heaps are chemically very complex and variable mixtures, as proved by our former studies. The current paper is a result of further exploration of the GASMET FTIR system via an iterative external databases search. This allowed to pinpoint a number of subsequent chemicals, both in terms of (semi)quantitative analysis and occurrence probability (fit). Some compounds represent new finds. The most likely candidates found, with fit often >90%, are CN compounds - especially hydrogen cyanide and isocyanic acid; acetylene, various alcohols, monoterpenes, formic acid. Acetaldehyde is the most common aldehyde, followed by 2-ethylhexylaldehyde. Tetrachloroethylene quite commonly occurs, but with worse fit values. An interesting find concerns methane- and ethanethiol being enriched at a vent with an intense and cumulative sulfur (S8) mineralization. Other less frequent or worse fit compounds include arenes, COS, some alcohol derivatives, other aldehydes, hydrocarbons, nitriles (acrylonitrile), ketones, acetates, ethers, acetone, acrolein (propenal), triethylamine, and methyl metacrylate. Important and relatively frequent inorganic gas is PH3, while SF6 is very rare. However, the occurrence of the later seems to be a very important discovery: SF6 is recognized by the Intergovernmental Panel on Climate Change as the most potent greenhouse gas.

Environmental influence of gaseous emissions from self-heating coal waste dumps in Silesia, Poland.

Gaseous emissions from seven self-heating coal waste dumps in two large coal mining basins, Upper and Lower Silesia (Poland), were investigated by gas chromatography (GC-FID/TCD), and the results were correlated with on-site thermal activity, stage of self-heating as assessed by thermal mapping, efflorescences, and surface and subsurface temperatures. Though typical gases at sites without thermal activity are dominated by atmospheric nitrogen and oxygen, methane and carbon dioxide are present in concentrations that many times exceed atmospheric values. On average, their concentrations are 42.7-7160 ppm, respectively. These are levels considered harmful to health and show that coal waste fire can be dangerous for some years after extinction. At thermally active sites, concentrations of CH4 and CO2 are much higher and reach 5640-51,976 ppm (aver.), respectively. A good substrate-product correlation between CO2 and CH4 concentrations indicates rapid in-dump CH4 oxidation with only insignificant amounts of CO formed. Other gas components include hydrogen, and C3-C6 saturated and unsaturated hydrocarbons. Decreasing oxygen content in the gases is temperature-dependent, and O2 removal rapidly increased at > 70 °C. Emission differences between both basins are minor and most probably reflect the higher maturity of coal waste organic matter in the Lower Silesia dumps causing its higher resistance to temperature, or/and a higher degree of overburning there.

First multi-tool exploration of a gas-condensate-pyrolysate system from the environment of burning coal mine heaps: An in situ FTIR and laboratory GC and PXRD study based on Upper Silesian materials.

A methodological approach to the complex geochemical analysis of the coal fire in burning coal mine heaps (BCMH) of Upper Silesian Coal Basin has been developed. The other approach used is gas chromatography and indicatory tubes. Powder X-Ray Diffraction is applied for phase analysis to determine the species composition of mineral condensates present within and around gas flues. The gas compositions are proved to be extremely variable, when comparing both different BCMH and flues or flue zones of the same heaps. One outstanding determination concerns GeCl4, found in most samples often in large quantities. No evident dependence between the gas and mineral condensate compositions is found: N-rich condensates may but do not have to be associated with NH3-, pyridine-, or NOx-rich gases. This is also true for S-rich and Cl-rich mineralization in connection with gases of SO2, H2S, OCS, CS2, thiophene, dimethyl sulfide, dimethyl disulfide, HCl, and various halogenated hydrocarbons. Fluorine is rarely present as HF, whereas SiF4 occurs more frequently and in much larger quantities. AsH3 is mainly a trace gas but may locally be enriched. Besides the common gases, a number of trace gases is also determined based on residual FTIR spectra. Those with the highest presence chance include cyanogen isocyanate, cyanogen N-oxide, (iso)cyanic acid, c-cyanomethanimine (ethylenediimine), isocyanatomethane, iodocyanoacetylene, acetonitrile, acetaldehyde, m-hydroxybenzonitrile (m-cyanophenol), isonitrosyl chloride, nitrosyl isocyanide, difluorosilane, pentacene, triphenylene, thiazolidine, cyclohexane, and a trinitrenetriazine. The occurrence of some metals and semimetals (e.g., Al, Mg, Ga) as neutral hydroxides, suggested by other authors to occur in natural gases, is possibly confirmed. The presence of trace metal carbonyls, nitrosyls and hydrides is also possible.