Multielemental composition and arsenic speciation in low rank coal from the Velenje Basin, Slovenia

Abstract

Coal is one of the main fossil fuel resources and remains the most important contributor to global power generation but coal utilization has severe negative impacts, mostly due to the release of CO2 and toxic elements into the environment. This means that determining the quality of coal is important to address the environmental and health problems related to coal combustion. Coal samples from the Velenje coalmine, one of the largest actively mined coal basins in Central Europe, were divided into organic rich and inorganic rich fractions according to the percentage of carbon. Oxides of the major elements (SiO2, Al2O3, Fe2O3 MgO, CaO, Na2O, K2O, TiO2, P2O5, MnO, Cr2O3), toxicologically and environmentally relevant elements (As, Ba, Co, Cu, Hg, Mo, Ni, Pb, Th, U, V, Zn, Se) and other trace elements (Ce, Cs, Dy, Er, Eu, Gd, La, Nb, Nd, Pr, Rb, Sm, Sr, Tb, Y, Zr) were measured in sample digests using inductively coupled plasma mass spectrometry (ICP-MS). The concentrations of the majority of analyzed elements were either equal to or below the global average for coal. Exceptions were Sr (1090 ± 510 μg g−1, 9 times higher), Ba (301 ± 184 μg g−1, 2 times higher) and Pb (9.12 ± 17.0 μg g−1, 1.4 times higher) in inorganic rich coal and Mo (7.76 ± 4.76 μg g−1, 3.5 times higher) and U (5.24 ± 3.23 μg g−1, 1.8 times higher) in organic rich samples. Eighteen elements (Ag, Au, Be, Bi, Cd, Ga, Hf, Ho, Lu, Sb, Sc, Se, Sn, Ta, Ti, Tm, Yb, W) were below the limit of detection in >70% of the samples. Speciation analysis revealed the presence of several organoarsenic compounds in the organic rich samples, with the tetramethylarsonium ion (TETRA, 0.01–1.10 μg g−1) and trimethylarsine oxide (TMAO, 0.01–0.29 μg g−1) as the most abundant. A comparison with coal samples from the Senovo, Kanižarica, and Trbovlje coal mines in Slovenia and from the Sokolov Basin, (Czech Republic) revealed that Velenje contains much higher amount of organoarsenic compounds (34.8 ± 16.9%) in comparison to the others (4.45 ± 4.19%).