Ruda Beds (Ba, Cr, Cu, Ni, Sr and V) and Saddle Beds (Mn and Pb) may be potentially
hazardous. Fly ash from combustion of coals from the USCB seems to be more easily
enriched with As, Co, Cr, Cu, Mn, Ni, Pb, V and Zn than with Ba, Rb and Sr, accumulating
probably in bottom ash. The highest element contents were found in the grains of fly ash,
with the size of 20 μm.