Geochemistry of trace elements in the Keşan coal and its effect on the physicochemical features of ground- and surface waters in the coal fields, Edirne, Thrace Region, Turkey

In this study, concentration and origin of trace elements of the Keşan coals in Edirne, Thrace Basin, have been investigated in order to determine possible environmental impacts on water pollution. The coal, ground and surface waters, and clay samples were taken from the coal mining area. The concentration of trace elements in 14 coal ashes, 15 water samples, and seven clays was determined by inductively coupled plasma-mass spectrometry. Additionally 11 of these coal samples were studied by proximate and seven coal samples were also studied by X-ray diffraction analyses. The mineralogical composition of the studied coal samples is made up mainly of quartz, clay minerals, feldspar group minerals, pyrite and amorphous matter. The Keşan coal ash samples have higher average concentrations of Cr (180ppm), Ni (192ppm), Rb (91ppm), and Sr (1701ppm); average values of other trace elements are lower than the world average of brown coal ashes. The sulfur content of the Keşan coals ranges from 0.4 to 3.90% (2.02% on average). The pH values of the waters vary between 6.55 and 8.36 in coal fields, 7.21 and 7.54 in springs. The F, Cl, NO₃^-, SO₄⁼, Ca, Mg, Na and K values of the waters vary between 0.11 and 0.25mg/l, 33.49 and 52.90mg/l, 0.05 and 59.27mg/l, 85 and 2829mg/l, 66 and 349mg/l, 64 and 222mg/l, 41 and 1187mg/l, 2 and 13mg/l, respectively in coal fields. Some elements are anomalous in concentrations in some water samples (e.g., Cr up to 49.6ppb; Mn up to 1185ppb; Fe up to 10,352ppb; Ni up to 55.8ppb; As up to 9.7ppbppb). It has been interpreted that the lower trace element concentrations in the water samples may be due to clay intercalated with coal. The clays are smectite type and they are enriched in Cr, Co, Ni, As, Sr, and Th (e.g., up to 394ppm Cr, up to 305ppm Ni, and up to 35.5ppm As).