We sampled and studied a borehole located in the southern part of Maritsa Iztok lignite field (Bulgaria) which comprises Late Miocene-Pliocene sediments of Maritsa Formation. The current report of ...Troyanovo-3 Mine sequence is the first to our knowledge. It represents a lignite-mudstone succession with variations in organic matter (OM) maturity. Thirty eight coal and mudstone core samples showed predictable ash and sulfur content. The XRD study showed illite/muscovite, illite/smectite, kaolinite, chlorite and quartz as main constituents that argue for a detrital origin. Additionally, we identified pyrite and gypsum and some peaks of marcasite and elemental sulfur. A set of eight mudstone samples rich in OM was selected for further geochemical analyses. The OM was classified as type III and II/III kerogen based on Rock-Eval pyrolysis data. The low amounts of extractable organic matter (0.01–2.25%) we found are consistent with the samples' low maturity and kerogen type. The yields of two samples were too low for further fractionation. Asphaltene amount (26.1–79.7%) predominates in the extracts. Diterpenoids (neutral fraction) and their polar analogues (slightly polar fraction) are highly abundant. In slightly polar fractions we registered ketotriterpenoids (mainly lupenones) in addition to the linear n-alkan-2-ones.
OM elevated maturity of the deepest sample (59.60 m depth) was evidenced mainly by hopane distributions, i.e. Ts/(Tm + Ts), homohopane H31αβ index, hopane ratios (H29αβ/H30αβ) and H27β/H27α. The organic geochemistry results do not fit the ordinary regional maturity trend. OM maturity variation, superimposed over natural low coalification degree, could be ascribed to an interaction with ascending hot reductive fluids. The sulfide mineralization found in the fractures also gives indications about the fluid circulation. Another thermal alteration affecting the middle part samples (24.0–28.3 m) was suggested due to elevated Tmax values and HI and OI relation for a charcoal piece and carbonaceous mudstone. Smoldering processes affecting these samples were presumed.
Low-temperature alteration processes were identified by n-alkanes, n-alkan-2-ones, and n-alcohols expulsion and downwards migration (from 18.0 m to 30.0 m) accompanied by a clear terpenoids depletion. The 17,21-seco-hopane-17,21-dione found for the first time for Maritsa Iztok Basin (MIB) samples further suggested processes of water seepage and wash-out. Microbial degradation activities usually accompanying water-washing possibly led to a specific n-alkan-2-one distribution. All the features we report point to either an even-numbered n-alkanoic acid decarboxylation or to a selective microbial degradation of odd-numbered n-alkanes to n-alkan-2-ones. In all, the history of the coal-mudstone sequence is complex, overprinted by variable alteration processes, first ever reported for MIB samples.
•Late Miocene coal‑carbonaceous mudstone sequence with diverged thermal history.•OM maturity of the deeper samples does not fit with the ordinary regional trends.•Tectonic processes and ascending hot reductive fluids could cause elevated maturity.•Charcoalification resulted in the enhanced OM maturity in the mid borehole level (80).•A view for wash-out and biodegradation induced by meteoric water seepage is offered.
Soil water repellency is phenomenon which is caused by compounds of organic origin, type of clay minerals and wetting/drying cycles. Hydrophobicity is usually characterized by a great spatial and ...temporal variability, especially in mine spoils where different types of overburden materials are mixed with coal particles and other waste products. The aim of this study was to investigate the changes of hydrophobicity with soil moisture content of Heavy Clay textured Spolic Technosols in the region of Maritsa-Iztok open cast coal mine. The sampling was done in a stubble field at 8 points from two soil depths 10–15 cm and 30–35 cm. The samples were analyzed for particle size distribution, total organic carbon content, soil bulk density, soil moisture content at field sampling, soil particle density, soil moisture content and water-drop-penetration-time (WDPT) at different matric potentials (SWRCC). The irregular presence of coal particles and different overburden sediments lead to spatial variability of studied properties, especially of total organic carbon content. In depth the average clay content, organic carbon content, water retention properties and soil water repellency (SWR) increased and correspondingly the density properties decreased. The distribution of SWR classes of the studied samples at the applied suctions during the drying process showed that the hydrophilicity of all samples at saturation persisted at suction pF 1.0 in 73% of the samples Most of the samples at suctions pF 1.7 and pF 2.0 were with slight and strong water repellency, but still there were hydrophilic samples 27% and 18%, correspondingly. At pF 2.5, which is often accepted as field capacity of fine textured soils, all samples were water repellent. The further drainage of the samples at pF >3.3 led to domination of extreme SWR and above pF3.7 all samples were extremely water repellent. Besides the unfavorable consequences of water repellency, the dry hydrophobic topsoil at the time of sampling formed a capillary barrier that reduced the evaporation and led to nearly 3 times higher water content stored in the subsoil.
•Physical characteristics of Heavy Clay textured Spolic Technosols.•Change of water repellence class with matric suction of Heavy Clay Technosols.•Increased water storage in subsoil under topsoil of hydrophobic Spolic Technosols.
Geochemical analysis of dump materials from the opencast Maritsa Iztok mines, Bulgaria, was carried out based on biomarker assemblages of hydrocarbon fractions. Organic matter (OM) and secondary ...transformations in three representative samples (massive black claystones and materials from the Iztok and Staroselets dump sites) were studied using geochemical proxies.
A number of differences were recognised in the respective OM compositions of the samples compared to both published data and between the individual dump samples themselves. The ОM of the studied samples was found to be polar, but also contains some apolar compounds. It consists mainly of resins and asphalthenes. Claystone OM is of the dispersed type, with intense oxidative-reductive interactions in a lacustrine environment resulting in its transformation into an inert material. Dump sample kerogen is of Type II and mixed Type II/III. In all samples, “odd” numbered n-alkanes are found in higher amounts. Diterpenoids (С19, С20) with pimarane, abietane and phyllocladane skeletons are preponderant. Tri- and tetracyclic terpenoids and steranes have been identified in the black claystones OM only. Hopanes are present in low amounts in extractable OM from all three samples. Biomarkers indicate that black claystone OM is formed from aqueous flora, with a minor supply of gymnosperms (mainly G. Sequoia). Iztok Dump OM is structured by higher plants with an aqueous vegetation input. The Staroselets Dump OM formation is assigned to an active microbial reworking of aqueous vegetation and bacteria with a minor coniferous supply. Different geochemical parameters admit anoxic stratified bottom waters for the black claystones with an addition of deep water stagnation for Staroselets sample in a Maritsa Iztok Basin (MIB) aqueous environment.
An attempt was also made to track the effect of secondary processes (oxidation, destruction, dearomatisation), temperature, water drainage and wash-out on dump materials. Leaching and weak degradation processes in the MIB dump environment are likely for a time span of ca. 40–50 years, considering the low percentage of short-chain n-alkanes, long-chain prevalence and low Pr/nC17 and Ph/nC18 ratios, with the Iztok Dump sample experiencing more advanced transformations.
A sequence of three lignite seams and interlayering carbonaceous mudstone is characterized by geochemical proxies. The study is extended by the palaeoenvironmental details given by the fossil fauna ...(gastropods, ostracods, and fishes). The predominant minerals (quartz and kaolinite) and main oxide relations of the carbonaceous mudstone point to sand and clay washed from weathered and/or altered felsic rocks from the catchment area. The mudstone features to deposition from suspension in standing or slow to persistently moving fresh waters at the bottom of the core log, and slightly aerated, warm, fresh to low saline, acidic to alkaline waters on the top. Three communities of organisms are depicted. The first is the pre‐swamp environment characterized by standing or slow moving fresh waters and detrital organic matter deposition. The second is the environment of swamp of detrital forest trunks. Depending on the climate and water table, the main forest communities are of trees of families Cupressaceae, Taxodiaceae, and Podocarpaceae accompanied by trees of family Betulaceae, and herbaceous plants. Different Sphagnum species are also abundant. The dry/cold environment is reflected in the herbaceous organic matter deposition. Polar terpenoids ratio differentiates slight climatic oscillations for the samples with a strong Gymnospermae dominance. The second coal seam development reflects the optimum tectonic conditions for peat growth in a cold and dry climate leading up to 25 m lignite deposition. The third is the moss swamp environment with very fluctuating elements. At the top of the log, a Sphagnum‐dominated peat has developed.
The content and availability of Pb, Cu and Zn were determined by the methods of soil extractions with aqua regia, 1M NH4NO3 and 1M NH4Ac. Reclaimed soils, which differ in land use, the duration of ...post reclamation development, geological and geographical characteristics were included in the study. In most pedons trace element total contents are irregular along depth and close to the background values in Bulgarian soils (Pb — 26μg/g, Cu — 34μg/g and Zn — 88μg/g). The copper content greatly varies between the minimum of 8.5μg/g and the maximum of 500μg/g. The latter is defined as an intervention concentration by the Bulgarian legislation, and is accepted as a toxic threshold which affects soil functions, the environment and human health.
Mobile concentrations of Pb, Cu and Zn are non-toxic assuming 8μg/g for Cu, 4μg/g for Pb and 43μg/g for Zn as acceptable limits of available heavy metals in Technosols with slightly alkaline pH (7.0 - 8.0). The acidic pH (<6.0) increases the solubility and desorption of zinc and copper, but diversely influences the bioavailability of lead. In acidic Technosols Pb and Cu mobile contents could exceed the Prüeß critical level of 1μg/g and may provoke independent and joint toxic effects. The lithogenic origin of Cu toxicity which amounted to 47.7μg available Cu/g soil shows the most serious risk of environmental pollution.
Intensive weathering of soil surface layers does not accelerate the trace element bioavailability. Pb, Cu and Zn mobility mostly depends on pH, the content and mineralogy of fine earth fractions (<0.01mm) and organic carbon pools in studied soils.
•Background total contents of heavy metals in Technosols located in coal areas•Toxic total and available contents of Cu in soils originated from copper mining•Safe mobile concentrations of Pb, Cu and Zn in alkaline Technosols in coal areas•Mobile Pb and Cu toxicity is likely to occur in acidic Technosols
Coals are suspected for many human health problems and are an object of the new discipline - "medical geology". Potential human health risk of organic compounds with coal/lignite provenance includes ...endocrine disruption, nephrotoxicity, cancer, etc. Recent investigations proved that different organic components, i.e. hydrocarbons, phenols etc. move through/release out of the dump area as a result of alteration processes of the organic matter (OM) caused by the wash-out and/or drainage processes. The timeliness of the present study is based on the scarcity of information on organic geochemistry of dump materials from open pit coal mines and weathered lignites in particular. The limited number of studies on dumps clarifies that even for the "short" time span (some tens of years) in geological point of view, processes of transformation of the extractable OM are detectable. The secondary phases, a result of the OM transformations, move through and out of the dump area and could be potential contaminants for the surface/underground waters and soils in the area. Another environmental problem comes from the air-born VOCs and products of the modern chemical industry. By GC-MS in the slightly polar fractions of the chloroform extracts of dump samples a broad set of components was determined, i.e. phthalates (dominant), i-propyl palmitate, i-propyl myristate, n-hexyl benzoates, etc. These organic contaminants could be regarded more likely as anthropogenic (originating from plasticizers, industrial pollutants, etc.). Presently, it seems that the identified compounds do not represent an acute toxic risk from an environmental viewpoint. However, some compounds could raise concerns and further attention is needed to be focused on them.
Two homogeneous (humovitrain and xylain) and one heterogeneous (humoclarain) lithotype macerals, separated from a lignite, were subjected to mild reductive treatment by NaH. The extensive ...chromatographic separation of the decalin-soluble fraction revealed some structural peculiarities. A strong predominance of α-phyllocladane was characteristic for all macerals. Series of
n-,
iso-, and
anteiso-alkanes, regular isoprenoids, alkylbenzenes and 1-methyl-4-
n-alkylcyclohexanes were identified by mass spectrometry. An angiosperm source input was represented by friedelane, lupane and
seco-hopane structures. Products of des-A and des-E-ring cleavages and C-10 demethylation were registered by mass spectrometry. The main difference was in the hopane distribution pattern. A strong prevalence of extended ββ-hopanes was found in the humoclarain sample. The mass spectral data revealed the existence of a basic difference in hopane precursors—diploptent or diplopterol for the homogeneous lithotypes and bacteriohopanetetrol for the heterogeneous lithotype.
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