Geochemia organiczna węgli brunatnych wybranych złóż Polski

Abstract

The work presents results of the complex geochemical investigations concerning primary biogenic material of brown coals, its influence on brown coal features and correlations between material sedimented in different depositional environments and peat bog zones. Changes occurring with rank in organic matter were investigated together with differences in distributions of biomarkers present in brown coal bituminous fraction and in pyrolysates of their macromolecular part. Petrographic composition, bulk characteristics with Rock Eval Analysis of organic matter, measurements of huminite reflectance and solvent extraction were performed for brown coals from the Konin, Turoszów, Lubuskie and Bełchatów Brown Coal Basins (Poland). Group composition of extracts was investigated with preparative layer chromatography (PLC). Chemical compositions of compound fractions was investigated with gas chromatography-mass spectrometry (GC-MS) while flash pyrolysis gas chromatography-mass spectrometry (Py/GC-MS) was applied for brown coal macromolecular part. The possibility to apply several geochemical biomarker parameters was tested in the work showing the values of these which have yielded significant geochemical information. Several new biomarker parameters were proposed which are based on aliphatic and aromatic hydrocarbons and polar compounds present both in low-weight and macromolecular brown coal fractions. These parameters can be also applied for the other types of sedimentary organic matter of low rank. The biomarker parameter results, correlated with petrographic and Rock Eval Analysis data, enabled to conclude about variability of brown coals from different basins, origins and variability of their primary biogenic material, types of depositional environments, maturity stage and the influence of postdepositional processes. The influence of maceral composition, lithotype and a gellification stage on geochemical characteristics of brown coals, distributions of particular compound groups and values of geochemical parameters have been assessed, indicating these which are the most susceptible. The main depositional environments of brown coal primary material were identified. Using biomarkers distributions in the extracts (diterpenoids, pentacyclic triterpenes, fatty acids) and compositions of macromolecular part pyrolysates the main brown coal-forming organisms were identified as monocotyledonous plants (grasses) and conifers of Pinaceae, Podocarpaceae, Cupressaceae and Taxodiaceae families, with Araucariaceae to the much lower extent. Brown coal rank assessed by biomarker parameters and huminite reflectance is similar and corresponds to the middle catagenesis (the geochemical stage). In the profiles of the Lubstów, Sieniawa, Turów and Bełchatów mines there is a gradient of several maturity biomarker parameters, confirmed by values of huminite reflectance. The significant influence of water-washing on bituminous fraction composition and values of geochemical parameters has been found. Characteristic features of water-washed organic matter of low maturity and the removal of the particular compounds has been described. The ten-point scale for assessment of water washing extent has been proposed. Biomarker parameters which values are not influenced by this process have been indicated. The presence of characteristic lignin monomers in the extracts enabled to prove the occurrence of biodegradation of brown coal macromolecule, and higher resistance of xylithic than detritic brown coals due to the presence of diterpenoids in wood, which substances show fungicidal properties.