Modes of occurrence of ecotoxic elements in coal from the Upper Silesian Coal Basin, Poland

Optical microscopy, x-ray diffraction and selective x-ray fluorescence spectrometry, SEM/EDS and laser ablation-micro-ICP-AES have been used to study the minerals and the concentrations of 15 trace elements in coal from the Upper Silesian Coal Basin. Mineral matter has a significant impact on the contents of V, Cr, Co, Cu, As, Rb, Sr, Cd, Ba and Pb in coal and organic matter on the contents of Ni, Zn, Mo, Sn and Sb in coal. Contents of V, Cr, Cu, Rb, Sr and Ba are most probably dependent on clay minerals and those of V and Rb on both clay minerals and vitrinite. Organic matter and carbonate minerals likely determine contents of Mn, and mineral matter and vitrinite likely determine contents of Co and Pb are probably influenced by sulphides. The bulk of the V, Cr, Mn, Co, Ni, Cu, Rb, Sr, Mo, Sb and Ba in the coal is probably of syngenetic origin. In contrast, the contents of Zn, As, Cd and Pb and, to a degree, those of Mn, Ni, Mo and Sb are epigenetic. Analysis results in the micro-area of minerals from bituminous coal reveal that the greater the heterogeneity of disulphides and of their association with carbonates and the more this heterogeneity applies to epigenetic minerals, the higher the contents of Ca, Cr, Mn, Ni, Zn, Cd and Pb. Diagenetic carbonates have higher contents of Cr, Mn and Ni, and smaller contents of Ca, Zn, Cd and Pb than the epigenetic minerals. These characteristics can be important from an ecological perspective; they identify which mineral matter components are best removed from coal to make it more suitable for combustion and in chemical processing.