Geochemistry of trace elements in Çan coal (Miocene), Çanakkale, Turkey

This study focuses on the geochemistry of trace elements and the coal quality parameters of Miocene lignite's from Çan basin. Twelve coal samples have been studied using proximate and ultimate analyses, X-ray powder diffraction, inductively coupled plasma-mass spectrometry, inductively coupled plasma-atomic emission spectrometry, scanning electron microscopy with energy-dispersive X-ray microanalysis and organic petrographic analyses. The Çan coals on an air-dried basis are characterized by broad variation of ash (ranging from 4.42% to 36.72%), high total sulphur contents (up to 8.10%) and high gross calorific values (3870–6612 kcal/kg). The mineral matter of the studied coal samples is made up of quartz, pyrite, clay minerals and gypsum. Major elements correlate positively with dry ash contents demonstrating an association with inorganic constituents. For twenty trace elements, including As, B, Ba, Be, Cd, Cu, Co, F, Hg, Mo, Ni, Pb, Sb, Se, Sn, Th, Tl, U, V and Zn received much attention due to environmental and human health concerns. Based on statistical analyses, most of the trace elements, except for Ba, Mo, Se and U, show an affinity to ash content. Elements including As, Cu, Co and Hg appear to be associated with pyrite. The concentrations of the trace elements are within the range of world coal average. However, the V content is higher than the world coal value and some volatile elements such as As, B and U are slightly enriched in some coal samples.